The Design: Structure

All Systems Go!

A month or so before I left for Australia to work for a while, I placed an order for my primary mirror.  It's a 16" F/4 from Terry Ostahowski which should be ready sometime in March.  With this key decision out of the way, I can pretty much order everything else for the scope as my funds and time allow.

One of the key reasons I decided to build my own telescope was so that I could choose exactly which parts met my particular balance of cost, quality and portability.  I have a good handle on the basic components needed, and some time to figure out exactly which specific part will best serve my needs.  After the mirror, the next thing seemed to be the overall structure... the stuff that would hold all the other stuff together.

The Criteria

Just like the overall criteria for my new scope, the structure itself needs to be portable, and economical, but there are a few more specific requirements:

• I want it to be as small and light as reasonable to firmly and stiffly support the optical system.  
• Ideally it will be quick and easy to take apart and put back together.
• It should have great motion;  Pointing a scope is a big part of using a scope and stiff or irregular movement on either axis can be a frustration.
• Like most things, being aesthetically pleasing is a plus.
• Of course it should be as inexpensive as possible while meeting the above criteria.

Any structure will be some compromise of all these competing criteria.  Some of them, like 'great motion' are tricky to evaluate without seeing one in person.  I've already decided that some variation of the Dobsonian mount.  This is mainly due to my desire for ease of use, but also helps a lot with the budget.  An equatorial mount for a 16" telescope would pretty much consume it entirely.

The Options

The first option is to built it all myself.  This sounds like a fun project, I do have some woodworking experience, and there are good plans of various designs available on the Internet.  In theory, it would be the least expensive monetarily, but would take a large amount of time.  Practically, I don't have a wood shop so I would need to purchase quite a number of fairly expensive tools to really do the job.  There is also a good chance I would not get it anywhere near right on the first try, which would mean putting up with something sort of usable, or spending the time and money to re-do it.... maybe more than once!

Although building from scratch was initially appealing, after a bit of thought, the option of a commercial kit seemed like a much better choice.  I'd love to be able to say with pride that I crafted this great telescope by hand, but even if I produced the structure, I knew I was not going to make the mirrors, focuser, cell, or any of the other pieces that go into a working telescope.   Some sort of kit really fit in with my plan for the scope; To assemble it from the specific pieces I feel meet my criteria best.

Besides,  I already had read about a great kit option, so I knew they were out there.  Even though I was pretty excited about the DobStuff.com kits, I wanted to see what other options were out there.  My search was not exhaustive, but I came up with a few other options:

• Obsession Telescopes:  I heard rumors that one could purchase some or all of a kit from Obsession, but I could not really find any information on this.  If they do sell them, I bet they are pretty nice, and rather expensive.  
• AstroSystems Telekit:  This seems like a nice kit, and it actually comes basically complete with spider for the secondary and a mirror cell.  The cost for a 16" kit is $1670, which after subtracting my budgeted cost for spider ($120) and primary cell ($250) is $1300.
• Hubble Optics: As indicated in this review Hubble Optics will sell you the structure of their ultra-portable dobs.  The price is listed in the review at $1195, which includes the spider and cell, I assume.  This is a bit better than the AstroSystems, and is very lightweight.  I had researched Hubble Optics as a potential supplier of the entire scope, but it seems there is some work to be done to make their scopes really perform, and I'm looking for something solid, even if it weights a bit more.
• DobStuff.com: DobStuff offers kits in a variety of sizes and configurations.  By default it's the structure only, but they also produce mirror cells and sell various lines of parts.  Kits include all the wooden elements, the strut poles, and bearing surfaces (ebony star/teflon) required to build the scope.  All I would have to do is sand, finish, and assemble.  The 13"-16" strut kit is $696.  I saw a few in action at the Golden State Star Party and was impressed.

The Decision

DobStuff kits were high on my list when I started this project.  In a way, it's sort of what inspired it by getting me daydreaming about building a large dob; Knowing I could get the precut parts to assemble made the whole enterprise seem doable.  After exploring the options above, I sent an email to Dennis Steele inquiring about prices and lead time.

He was very helpful and the prices were as quoted on the site.  It also turns out his workshop is near my primary observing locations in Joshua Tree, CA, where the scope would be built and spend most of it's time.  Graciously, he agreed to allow my to pickup the scope from his shop to save some shipping.

I placed an order for a 16" strut kit with the easy transport option for even more portability.  While I was communicating with him I also found that he produced nice aluminum floating mirror cells as well.  I'd already done a fair bit of research on mirror cells, which I'll describe in another post, and I felt his price/quality/design made sense, so I added a mirror cell to the order.

I believe the initial lead time he quoted was something like 4-6 weeks, which seemed fine since my mirror would take four months anyway.  This would still give me plenty of time to work on finishing and assembling the structure before the mirror was ready.  Turns out, he was able to piggy back my order with another 16" kit and cut the parts all at once.  This shortened the lead time to just a week and a half!


On October 20th, Dennis sent me an email with a picture of my completed kit, ready for pickup!

DobStuff 16" kit with mirror cell.  Strut poles are included but not pictured.

It was around this time that I learned I would be going to Australia for several months.  Exciting, but a bit of a bummer at the same time.  I was really looking forward to sanding that bad boy up nicely and figuring out what stain/finish I wanted to use.  When I emailed Dennis to let him know I could not pickup the kit as planned and to arrange for shipping, he kindly offered to hold the kit for me as long as I needed for no additional cost.  That's great customer service!


Current Status

As of now I have almost 2/3rds of a telescope. budget wise at least.  Here is my updated budget with a few the few things I've ordered slotted in with actual pricing.

Item	Cost	Notes
16" Primary Mirror	$2450	Terry Ostahowski 16"
Secondary Mirror	$220
Mirror Cell	$200	DobStuff Flotation Cell
Structure	$700	Dob Stuff 13"-16" Kit
Spider	$100
Focuser	$200
TOTAL	$3870

For anyone keeping track, this is about $1200 more than my original budget.  This is pretty much due to my mirror choice.  I had originally planned on going with a more mass produced JMI 16" f/4.5 mirror with secondary for only $1439, which is a very good price.  However this would have made the scope too long and put the eyepiece out of reach for me when pointing towards the top of the sky.

I could have gone with a smaller mirror, and therefore a shorter scope, but once I left the JMI mass produced mirror behind, I was in custom territory and the prices went up considerably even for smaller mirrors.  I ultimately decided to spend more now so I would not be as tempted to upgrade again later or regret that I did not get the scope I really wanted after all was said and done.

So that is where the project stands.  I have a mirror on order, perhaps even being ground by now, a finished DobStuff kit waiting to be picked up, and me out of the country.  I knew waiting would be tough, and being on an overseas adventure of sort has made the time go by more quickly, but I am anxious to get started.  I miss observing in Joshua Tree and knowing I could be working on the scope during the day, and observing at night over the holidays, makes it all the tougher to be away.

I hope the holidays find you in good spirits and provides some wonderful winter observing opportunities.  Clear skies and warm fingers!

The Geminids and The Astronomical Society of Victoria

So yeah, hmmm.... it's been a while since I posted.  Looks like it's been almost a month since my last post, and that was just a quick note about moving to Australia for a while.  If you discount that, it's been almost two months.  It's been a busy time, but I'm finally feeling settled into the new city and the job duties are smoothing out, so I'm hoping to write a bit more.

I've certainly not stopped dreaming about astronomy, or my future telescope, but dreaming is about all I've really been able to do.  I'm under a whole new section of sky, with so many and varied wonders to be seen, and I've not been able to take advantage of it... yet.  A few things have been lacking so far, Time, Equipment, and Knowledge.


Time and the Geminids

I think the time issue will  only get better from this point, at least for a while.  The new studio I'm here to setup is really coming together; I'm now usually free on the weekends and I'm not working very late in the evenings.  In fact, last Tuesday, the sky was very clear, the moon was gone, and I took my new Southern Skies edition of the Night Sky out on a walk.

I did not get anywhere very dark, mostly just around my hotel, ducking into shadows to avoid street lights.  There is a park nearby I've got my eyes on, it's walking distance, and is large enough to at least offer some relief from local light sources... maybe next time.  On my short excursion I was at least able to look at the sky and try to orient myself.  Even fairly close to the center of Melbourne, there are still significantly more stars visibile than in Los Angeles.  I'm going to chalk it up to less particulate in the air, and about half the population density.

There are some familiar sights here, I spotted Orion almost immediately, but it took me a minute or two to realize what should have been obvious.  He's upside down.  At least from the way I'm used to seeing him.  The constellation was low on the North/East hoizon, and his sword was hanging 'upwards' towards the zenith pointing the way to a whole area of sky completely unfamiliar to me.  It was strange to think that the rest of the sky I'm familiar with is down below the horizon in the direction of his, now upside down, head.  

My attempts at finding constellations were not all that successful, this first time out.  I'm hoping to spend some more time studying the sky next week if the weather cooperates.  Even though it was a short observing session, from a terrible location, I was rewarded with one gem.  A very bright, and fairly long lived, Geminid!

At least it seemed like a Geminid.  It was several days before the peak of the shower, but it seemed to be going the right direction, in the correct area of sky, so I'm pretty confident.  It was surprising to me considering I was a few days early, it was pretty early in the evening, and I was under light polluted skies.  Under a dark sky, I imagine it would have been awesome.


Equipment

I have several potential solutions to this one.  First, as I came to realize by taking the time to actually go outside and look up, eyes are pretty good on their own.  There is a lot for me to observe with the standard issue equipment.  There are whole new constellations and wide starscapes to learn and appreciate

Second, I found an optics shop that has what looks to be a decent pair of binos at a resonable price.  I've not found many reviews, but the few I have found are positive.  New binoculars have been on my list for a while, and I'd love to get under a dark sky here and try them out!

Third, when I return to Los Angeles for the holidays in about a week, I'm going to come back with my C6 travel kit.  At 6" (152mm) in diameter the scope is smaller than my workhorse XT8, and much smaller than the 16" (406mm) I'm working on building.  I'll also have to travel light, with the collapsable photo tripod and a limited set of eyepieces and accessories, but it will still be a heck of a lot more kit than I observed with for years.  I expect great things from that little scope!


Knowledge - Enter the ASV

To tackle the last item I'm going to join the Astronomical Society of Victoria (ASV), which is the local astro club here in Melbourne.  The way things stand right now I'll be here for 4 months or so after the new year.  That's maybe 8 weekends of good dark sky observing when the moon won't be an issue.  Weather might cut into that number even more, so it's important I know where to go to observe, and what the "Can't Miss" objects are.  I need to meet people who know the geography and the sky.  Also, maybe they can give me a ride... driving on the left is a little intimidating.

Joining an astronomy club has been on my todo list for a long time.  In Los Angeles, my work schedule and lack of automobile always seemed to interfere with getting to any of the local club meetings to check them out.  By a wonderfully strange set of coincidences, here in Melbourne, I'm staying a block or two away from the regular meeting place of the ASV, and my work runs from 8-6, rather than 9-7.

I missed the meeting in November due to work and ignorance of the location, but I was able to attend the December meeting last Wednesday.  Right before the meeting was scheduled to start I found the room in the National Herbarium and rushed in.  There were something like 50 people in attendance and the meeting started promptly at 8:00pm.

The president of the club started with some announcements about committee memberships, meeting schedule changes and information about the yearly Star-Be-Cue they hold at their dark sky site during the new moon in December.  He then went on to describe the building of a wooden hybrid tripid/dobsonian mount he built for his 6" refractor.  It was a very interesting presentation and hearing about it made me yearn for the chance to get started on my 16" scope.

Being the last meeting of the year, the majority of the time was dedicated to slideshows and videos from the last year's events.  I could not have picked a better time for my first visit!  It was a fun and fascinating to hear about the events the ASV has sponsored including monthly star parties, a viewing of the transit of Venus, and the total solar eclipse visible from the northern tip of Australia.

A few of the recaps included wide field, time lapse photography of the sky from their dark sky site.  It's only about 1.5 hours from the city, but judging from the video, it's got much better skies than my normal dark sky site 3 hours from Los Angeles.  Even though Melbourne is not all that far south, at 37 degrees latitude, they had a strong Aurora during one of the most recent star parties.  Sadly, this is very uncommon, so I'm not likely to see anything like it while I'm here.  Still, it was beautiful, even on the time lapse.

When the meeting was breaking up I had a chance to introduce myself to the club president and speak to him for a few minutes.  He, like everyone I met, was very friendly and enthusiastic about both their club and the night sky.  Before attending the meeting I was somewhat apprehensive, but it was a wonderful experience to be around so many people with a common interest.  I look forward to attending again in January.

When I get back into Melbourne after my holiday trip home, joining the ASV is first on my todo list.  For a $70AU membership fee, I'll have access to their dark sky site and, more importantly, a group of very knowledgable people to help me make the best of my observing time here in Melbourne.  I'll probably end up renting a car for the trips, but it will be nice knowing that I have a dark and friendly place to head to.

Attending the meeting also showed me what I am probably missing by not making the effort to make it to one of the local Los Angeles clubs.  When I get back I'm definitely going to find some way to make it work for me.  If you have not at least explored one of your local astronomy clubs, I really suggest you do.  You might enjoy it as much as I did.

My next post will definitely return to my telescope build, I've got some exciting new via email to share!

Greetings from Australia

A Busy Time

I really did intend to post some entries the last few weeks, I've got some ideas, and some half written pieces....  However, like it so often happens, life sort of directed my attention in other areas.  I work in Visual Effects for Film, and the hours can sometimes get a little crazy when deadlines loom.

Almost immediately after I finalized my choice and ordered my new 16" mirror, I launched into a little patch of overtime at work.  Nothing too crazy, but enough that I did not have the time to post any updates.  As this little burst of deadline related activity was winding down, plans for opening a new branch of our studio in Australia were heating up.

There was some talk of me flying out to do some training and help get things started, but the date was unknown and it all seemed a bit distant to me....  I had a nice weekend trip to Northern California planned, and figured I'd get some observing and writing time in the following weekend.  When I returned to work last Monday following my four day trip, I was asked if I could be on a plane to Australia that Friday, and stay for a few months.  Wow!

Between tying up loose ends at home and work, I was pretty busy last week.  I boarded a plane on Friday night, landed Sunday morning in Melbourne and went almost immediately to work.  Things are just now settling down, and my jet-lag subsiding, enough that I found an hour to update my blog.  


A Great Opportunity

This blog is not really about my work in Visual Effects, which I enjoy a bunch, it's about Astronomy, which I enjoy even more.  Aside from the craziness of getting ready to go, and the sadness of leaving my girlfriend, family, and usual observing locals behind, I'm really excited to be here.  There is a lot of work to be done over the next few months, but there is no way I'm NOT going to find some time to observe under the Southern Skies!

I've never even cracked the pages in my Pocket Sky Atlas that detail anything further south than Sagittarius, so I'm in unfamiliar territory to say the least.  I managed to order the Southern Sky edition of the venerable "The Night Sky" planisphere before I left, but I did not have enough time, luggage space, or mental bandwidth to pack my C6 travel kit.  I'm going to be pretty busy anyway, and I figured I'd need some time to get oriented and figure out a nice place to observe.

If I find time to observe before I head home for Xmas, I'll be using any scope I can beg from a local club, or perhaps a pair of Binoculars if I can find one here for a good price.  I've been meaning to get a nice pair anyway.  So the first few things on my agenda are to find a local club, find an optics shop, and spend some time with the planisphere trying to orient myself.


An Appeal to Locals

There are some Australian readers, if the Blogger stats are to be believed, and I know it's a long shot, but if anyone has any information about the Astronomy scene in and around Melbourne, I'd love to hear it!  Club information, observing sites, whatever you've got.

I'd also love to have some suggestions for 'Don't Miss' objects.  The large and small Magellanic clouds clouds are a long time dream of mine, but there is certainly so much to see, I'm afraid I'll miss some real gem.  If you have any suggestions, they will be appreciated.

I hope to finish up some of those long-delayed posts, but until then, Clear Skies wherever you are!

The Design: Primary Mirror - Part 2

Work has been a bit hectic for me lately, long hours and such, so I've not had a lot of time to post anything here.  Even as busy as it's been, I've found time to daydream about my new telescope.  In my last post I narrowed my list of potential mirrors down to four candidates:

Company	Material	Size	f-ratio	Height	xt8 Mult	Price	$/Inch
Discovery	Pyrex	15	4.2	64.5	3.5	1699	9.60
Pegasus	Borofloat	14.5	4.3	64	3.3	2100	12.72
O.W.L.	Pyrex	15	4	61.5	3.5	2470	13.95
LightHolder	Pyrex	14.5	4.1	61.2	3.3	2440	14.79

It was a nice tidy list, and I contacted each of the manufactures to double check pricing and see about delivery times and such.  The pricing was accurate, and lead times were all around three months, which is pretty reasonable considering the work involved in a mirror like this.  Everybody I've contacted was helpful and responsive, which goes to show the passion they seem to share.

All of the emails did not bring me any closer to a decision, so I decided to try and get some additional input.  There are a lot of helpful and knowledgeable people on Cloudy Nights so it's usually my go-to place for questions I might have.  I started a thread titled 'Mirror Choice for 14-16" Dob Project' and laid out my plans and the current short list.

Quality vs. Price

In no time at all I was getting some insightful comments.  The entire thread is an interesting read, but the most useful posts were not about any specific mirror I had on the list, but were the more philosophical posts and the posts that added perspective.  Two things stood out to me; The first is summed up by these two quotes:

What you are paying extra for is the comfort and re-assurance that your mirror will be excellent. [...] On nights of excellent seeing you can certainly tell an excellent mirror apart from a good one. These nights aren't all that common but it's worth it when the air is good and knowing what you have doesn't get better. - John Bambury 

The thrill and satisfaction of quality is remembered long after the sting of high price. If you intend this to be a "lifetime" telescope take the pain now. [...] Forget the price for now. Aperture, length, and availability is what you need. - Jeff Morgan

A few of my questions boiled down to,  'How good is good enough?' and 'What is the extra money for a premium mirror really buying?'.  These two posts, along with others, sort of put things in perspective for me.

If I purchase a great mirror, from someone with a reputation for quality, there is a good chance that I will be happy for the lifetime of the telescope.  Aperture fever may kick in again, but I will never wonder 'What if I had paid a little extra?'.  Additionally, if I ever do succumb to aperture fever and want to sell my scope, the resale value will probably be higher.


Size Vs. Price

The second thing I realized in reading through the posts was closely related to the first.  Basically, if I was going to spend the money for a 'lifetime' scope, I should be happy with the end product.  Even though a 16" has only 14% more area than a 15" mirror, I know myself, and I'm pretty sure I'd be often wondering what that 14% would be like.

When I had to rule out the 16" mirrors due to price constraints, I was disappointed.  From the start I imagined this as a 16" scope project, even though I was open to a smaller scope if my design constraints (Eyepiece Height, Overall Size, Budget) meant 16" would not be possible.  I was tempted to go beyond my $2500 budget for a mirror and just make it happen....


Wisdom of the Crowd

I spent a fair amount of time trying to find mirror vendors, but I am not at all surprised that I missed a couple.  Two new manufacturers were suggested, Steven Swayze, who I had somehow missed but was very well respected and Terry Ostahowski, who also has a great reputation for quality optics.  I contacted both of them asking for pricing on a 15" or 16" f/4 mirror.

Both of them were responsive and informative.  I even got three different options from Steven Swayze, which was appreciated.  Here is the table with the new possibilities added, again sorted by $/inch.

Company	Material	Size	f-ratio	Height	xt8 Mult	Price	$/Inch
Discovery	Pyrex	15	4.2	64.5	3.5	1699	9.60
Ostahowski	Pyrex	16	4	65	4	2450	12.19
Pegasus	Borofloat	14.5	4.3	64	3.3	2100	12.72
Swayze	Pyrex/Cellular	16.25	4	65.9	3.3	2700	13.03
Swayze	Pyrex	16	4	65	4	2700	13.44
O.W.L.	Pyrex	15	4	61.5	3.5	2470	13.95
Swayze	Pyrex	15	4	61.5	4.13	2500	14.15
LightHolder	Pyrex	14.5	4.1	61.2	3.3	2440	14.79

The Decision

So many great options, and I was really excited to have 16" mirrors back into the mix, even if they blew my budget by 8% or so.  I was leaning heavily towards the 16.25" cellular mirror Steven Swayze suggested.  It's larger, and lighter, than a 16" mirror and would probably have superior cooling and stiffness.  Ultimately, I decided a 16" is more standard, and would make replacing (if I did something foolish to damage it) or selling the mirror (if something else terrible happend) easier in the future.

Looking at the price per square inch, and doing some research about the acknowledged quality, finally made my choice clear.  Today I put down a deposit on a 16" f/4 mirror from Terry Ostahowski.  Delivery is estimated sometime in March of next year... that's going to seem like long time, I'm sure!

Unlike the larger 80mm finder I bought a while back at P.A.T.S. this is the first, scarily big, step towards my new telescope.  Since the dimensions and focal length of the mirror sort of anchor the design, I can pretty much finalize all the other options I have to consider.  I can figure out what size secondary to use, find a spider to hold it, double check my decision on a structure, and think about focusers and other accessories.

It's exciting to think that I could have a working telescope as soon as April or May, 2013.  Seems like a long time from now, but I have a lot of things to consider, and observing to do with my current XT8 in the meantime!

Here's hoping for clear skies to keep me occupied...

The Design: Primary Mirror - Part 1

Quick Recap

In my last new telescope related post, I finalized my decision to build a telescope rather than buy.  Towards the end of that post, I did some thinking about my budget.  After some quick calculations, it became pretty clear that the mirror has a huge impact on the cost. 

It seems that no matter what size mirror I buy, the rest of the scope is going to be pretty much the same price.  A couple of parts, namely the primary cell and secondary, vary a bit with the size of the mirror, but everything else remains constant.  I'm estimating this 'base price' for the telescope, sans mirror, at about $1500.

The Long List

After looking around for a bit online, here is my long list of 17 potential telescope mirrors.  They are ordered by name of the company that produces them:

Company	Material	Size	f-ratio	Height	XT8 Mult	Price	Link
Discovery	Pyrex	15	4.2	64.5	3.5	1699	link
Discovery	Pyrex	16	4.5	73	4	1699	link
Hubble	Pyrex / Sandwich	14	5	72	3	1775	link
JMI/GSO	BK/7	16	4.5	73	4	1439	link
LightHolder	Pyrex	14.5	4.1	61.2	3.3	2440	link
LightHolder	Pyrex	16	4	65	4	2870	link
Lockwood	Pyrex	16	4	65	4	3870	link
O.W.L.	Pyrex	15	4.5	61.5	3.5	2470	link
O.W.L.	Pyrex	16	4	65	4	2900	link
Pegasus	Borofloat	14.5	4.3	64	3.3	2100	link
Pegasus	Borofloat	16	3.5	57	4	3100	link
Waite Research	SUPREMAX 33	14.5	4	60	3.3	2650	link
Waite Research	SUPREMAX 33	15	4	61.5	3.5	2800	link
Waite Research	SUPREMAX 33	16	4	65	4	3000	link
Zambuto	SUPREMAX 33	14.5	4.5	67	3.3	2650	link
Zambuto	SUPREMAX 33	15	4	61.5	3.5	3360	link
Zambuto	SUPREMAX 33	16	4	65	4	3924	link

*XT8 Mult is how many times more area this new mirror would be than my current 8" mirror

Two obvious points, there are a lot of options (this may not even be a complete list), and they vary quite a bit in price.  If I choose the least expensive option, the mirror will make up 50% of the $3000 cost of the telescope.  If I choose the most expensive, the mirror will make up 73% of the $5500 cost.

So this is the decision that seems to have the most impact on the cost, and probably quality, of my new telescope.  A telescope I hope will last a long time.  I'm beginning to dread this decision.

A Disappointing Realization

When I was thinking about the size of my new telescope a while back, I felt that something in the 14-16" f4.5 range met my criteria for portability, and for flat footed observing.  Along with price and overall aperture these are two of my most important considerations.  After a recent experience at the Pacific Astronomy and Telescope Show, I think my allowable size range might be a little off.

Me and a LightBridge 16" f4.5 Telescope

You can pretty much see in the photo above, that my eye is NOWHERE NEAR the eyepiece...

In order to observe with my feet on the ground, without a ladder, step-stool, box, or the like, I have to be able to reach the eyepiece through most of the range of motion of my new telescope.  Observing with the telescope straight up is somewhat awkward, so I'm willing to forego a bit of sky close to 90 degrees, but I am really committed to a flat foot telescope.  This means that the eyepiece height has to be at or below 62", which is the distance my eyes are from the ground, for the vast majority of angles.

The main factor in how high the eyepiece of a dobsonian telescope is from the ground is the focal length of the telescope, which is determined by the size of the mirror and it's Focal Ratio.  The focal ratio (or f-ratio) of a telescope is the relationship between the size of the mirror and the distance away from that mirror the converging light beam reaches focus.  In short, the higher the f-ratio the longer a telescope will be for a given size mirror.  There are some other design issues that can raise or lower the eyepiece a few inches, but really it's the focal length of the scope.

In retrospect, it should have been obvious to me that a 16" f4.5 scope, with an eyepiece height at zenith (pointed straight up) of somewhere around 73" would be no good.  I was hopeful that my rough calculations of eyepiece height might be off.  After all, eyepiece height is not exactly the focal length of the scope since the light path is turned at a right angle and the mirror is not sitting on the ground.  I also figured that even if the height at zenith was too much, that pointing the scope down just a bit would get the eyepiece and my eye better aligned.  

Seeing a 16" f/4.5 scope in person, standing next to it, moving it to various altitudes, really showed me just how wrong I was.  It was not until lower than 70 degrees that the eyepiece got to a height I could actually view through.  This means I would give up the upper 40-50 degree patch  of the sky, which is pretty much the darkest and most awesome part.  

So I am ruling out any mirror that will produce an eyepiece height greater than 65".  Even at 65" I could not use the scope straight up, but it would let me get close.  I think this height would be comfortable for me, and the area of the sky that would be inaccessible would be pretty small.  

Cut #1 - Eyepiece Height

All of that long winded explanation means I have to go with something more like a 16" f/4, or a smaller f/4.5 mirror.  This limits my options a bit, which is good, because too many options are proven to make people anxious and less satisfied with their decisions.  Sadly, 16" f/4.5 is a very common size, and common tends to equal less expensive.  Here is the slightly shorter list, now with 13 options:

Company	Material	Size	f-ratio	Height	xt8 Mult	Price	Link
Discovery	Pyrex	15	4.2	64.5	3.5	1699	link
LightHolder	Pyrex	14.5	4.1	61.2	3.3	2440	link
LightHolder	Pyrex	16	4	65	4	2870	link
Lockwood	Pyrex	16	4	65	4	3870	link
O.W.L.	Pyrex	15	4	61.5	3.5	2470	link
O.W.L.	Pyrex	16	4	65	4	2900	link
Pegasus	Borofloat	14.5	4.3	64	3.3	2100	link
Pegasus	Borofloat	16	3.5	57	4	3100	link
Waite Research	SUPREMAX 33	14.5	4	60	3.3	2650	link
Waite Research	SUPREMAX 33	15	4	61.5	3.5	2800	link
Waite Research	SUPREMAX 33	16	4	65	4	3000	link
Zambuto	SUPREMAX 33	15	4	61.5	3.5	3360	link
Zambuto	SUPREMAX 33	16	4	65	4	3924	link

Cut #2 - Price

I could theoretically save up money for as long as I need to get the most expensive mirror on the list above, but every month I save is another month I don't get to use my new telescope.  That's why I set a goal of one year; I'd love to have the telescope ready to go for the summer star party season 2013.  Spending more than $4000 on this project is probably unrealistic if I want to meet my goal.  So I'm going to have to spend less than $2500 on the mirror to make it work.  That brings us down to these 4 options:

Company	Material	Size	f-ratio	Height	xt8 Mult	Price	Link
Discovery	Pyrex	15	4.2	64.5	3.5	1699	link
LightHolder	Pyrex	14.5	4.1	61.2	3.3	2440	link
O.W.L.	Pyrex	15	4	61.5	3.5	2470	link
Pegasus	Borofloat	14.5	4.3	64	3.3	2100	link

I still think those are a lot of good options, based on some of the tests and opinions I have found so far.  Ultimately, there is only room for one primary mirror in my new telescope, so I'm going to have to figure out some way to evaluate these mirrors.

The Short List

Now that I have a manageable list, I need to figure out what I need to do to convince myself to buy one.  All things being equal, I want the most bang for my buck.  A good first way to compare these options is dollars per inch of area.  Here is the same list, with dollars per inch replacing links, and sorted by the same:

<

Company	Material	Size	f-ratio	Height	xt8 Mult	Price	$/Inch
Discovery	Pyrex	15	4.2	64.5	3.5	1699	9.60
Pegasus	Borofloat	14.5	4.3	64	3.3	2100	12.72
O.W.L.	Pyrex	15	4	61.5	3.5	2470	13.95
LightHolder	Pyrex	14.5	4.1	61.2	3.3	2440	14.79
LightHolder	Pyrex	14.5	4.1	61.2	3.3	2440	14.79

Now this is a list I can do some thinking about!  It's reasonably short and ordered by value.

I'm hoping to decide in the next week or two and see if I can place an order.  Here are my thoughts on each of these options, and what I want to look into:

Discovery 15" f/4.2: There is a virtue in being the least expensive.  The money saved could potentially go for a nicer focuser, or perhaps a nice fan system.  I have not read any information about their quality, so I'll definitely need to do a bit more digging

Pegasus 14.5" f/4.3: About 7% smaller than the 15", but this does not sound like much.  I've heard generally good things about Pegasus mirrors, but is the extra quality worth less aperture and more cost?

O.W.L 15" f/4: Almost $800 more than the Discovery, but slightly lower f-ratio for a shorter scope.  In fact, I'd be able to use this one straight up!  Not sure how the quality compares to the Discovery mirror. This is another company I've not heard much about, so I'll have to try to find some reviews.

LightHolder 14.5" f/4.1: The most expensive inches of aperture of the bunch, but LightHolder is supposed to be very good.  Again, will I notice?  Is it $340 better than the Pegasus?

So my next step is to try to learn about mirror quality, and how much difference it makes at the eyepiece.  I'm sure that there are differences in quality that can be measured with various machinery, but are these differences perceptible?

Another consideration is lead time.  Since most of these companies make mirrors to order, I'm going to email each one to see what their current wait/lead time is.  I'll let you know in a future post what sort of responses I get.


A Eulogy for the 16"

I'd like to pause here for a second to mourn the passing of the 16" options.  There is just something nice, round and magical, with the idea of upgrading to a telescope that offers 4x the light gathering of my existing telescope.  16" offers 21% more aperture than the 14.5", and 13% more than the 15" mirrors.  If I was able to go with an f/4.5 and still reach the eyepiece, 16" would be within my grasp!  Curse my shortness!

I'm very much tempted to open up my budget a little bit to get to the 16" mark.  I'd have to go at least $2900 to get there.  That's $1100 more than the Discovery 15" above!  I'm just not sure it's worth it for 13% more light gathering.

One very interesting option that I dropped due to price was the Pegasus 16" f/3.5.  For $3100 it would have given my the LOWEST eyepiece height out of any of the options, a mere 57" off the ground!  That complete telescope would cost roughly $4700, about 46% more than a 15" based on the Discovery mirror.


What do you think?

I'm going to do some research on manufacturing methods, reputation, and test reports, but ultimately, How much difference does the quality of a mirror make to the visual observer?  Have you had any relevant experience?  Do you know, or have you heard, anything about the mirrors on my short list?  Are there any I missed?

Also, if I'm going to have this telescope for a long time, will I end up disappointed if I don't spend 50% more and get a 16" scope?  That fast 16" Pegasus is tempting!  I'd love to hear what you think.

PATS 2012 - Good Products, Great Fun, and Sad Realizations

A Tale of Two Shows

Last Sunday I made some time to visit the Pacific Astronomy and Telescope Show in Pasadena.  It's a yearly exposition of astronomy related vendors and clubs which claims to be "the largest and most exciting astronomy show on the west coast".  This was the second time I've checked it out, and can't say that it's either the largest, or most exciting astronomy show on the west coast, but it's a nice way to spend and afternoon and maybe find a deal or two from one of the vendors.

The show runs Saturday and Sunday; tickets at the door are $20.  I think last year I purchased in advance and received some discount. There is an exhibit hall with booths setup and a series of presentations in adjacent rooms.  The Pasadena convention center is pretty sizable, and the PATS is not really large enough to fill the entire space.  This year it was sharing the main exhibition hall with the Bride World Bride Expo. 

As I was walking towards the hall after purchasing my ticket, it was pretty easy to guess who was attending which event.  The people walking around with the Sky and Telescope bags, or with arms full of astro gear were here for the PATS.  Everyone else had copies of Bridal World or flowers.  Lots of flowers.

PATS was sharing with the Bridal Expo... the line is for the Expo.  There was no line to enter the PATS exhibits.

The Exhibition Hall

Everybody attending the show got a free issue of Sky and Telescope and a program upon entry.  I briefly glanced at the program schedule and did not see anything to interest me, so I headed straight to the exhibits.  This was only my second year, and I remember it being pretty small, but this year seemed even smaller.  According to the program there were 44 vendors, and they were arranged in four rows.

I did an initial walk through of the exhibit in about 15 minutes or so and even though it was not a huge show, it was very nice to be surrounded by like minded folks.  The booths ranged from the large and professional, to the small and volunteer.  It was not very crowded, which meant the venders were available to chat and spend some actual time with the attendees.

There was not really any specific thing I was looking for.  I thought that it would be nice to see some of the newer gear, talk to some of the organizations and clubs, and maybe find something for my telescope project.  If nothing else I figured it was a nice way to spend a Sunday afternoon.


The Big Names

As one would expect the three heavyweights in telescopes and accessories were on hand.  Meade had a large booth, spaciously appointed with selections of their current line.  They had mounts, SCT's and one 16" LightBridge to round things out.  This was the first time I had seen their convertible Alt-Az/GEM mount.  It seemed pretty solid and was presented in the Alt/Az dual scope configuration.  Pretty neat.

Meade Instruments

Right across the way was the smaller, but still impressive, Celestron booth.  They had a nice selection of their SCTs on GEMs, along with eyepieces and some educational items, such as microscopes and a very small/cheap newtonian.  You can see the little guy at the screen right end of the table in the pictures below.

Celestron.  Notice the little guy at the far end of the table.  A Newtonian Finder?

The FirstScope is a 76mm f4 reflector with a spherical mirror.  Immediately upon seeing it's diminutive size, I was launched into a several minute daydream of using it as a finder.  I suspect it would work, but it would be difficult to get the image into the 'correct' orientation.  Some people have no issue with the mental gymnastics required for non-correct image finders.  I, however, prefer to use finders that orient the sky the same as my un-aided eyes, so this dream was dashed.  

Around the corner, Tele Vue had a large, but sparse booth.  They only have so many telescopes in their line, and eyepieces don't take up much space.  It is pretty impressive to see a full set of Ethos, Nagler or Delos eyepieces though.  Speaking of which, there is still time to enter the the International Dark Skies Association Dark Sky Giveaway for a chance to win an entire set of Ethos eyepieces!

TeleVue - Home of the Eyepiece!

On the right side of the picture above you can see a gentleman pointing to a black case.  He's probably explaining to the other gentleman that you can use one telescope to collimate another!  This was the most interesting thing in the booth as far as I was concerned.  There was an artificial star stuck in the diagonal of one telescope, which was then pointed at and rigidly joined to a second you wanted to collimate.  The optics of the first scope made the star appear like it was very far away, far enough to use it to collimate or star test.  It was a clever idea and an interesting experiment in optics.


The Up and Comers

Aside from the bigger names, there were a few other telescope manufacturers.  PlaneWave and Williams Optics were there, showing two different approaches to astrophotography.  PlaneWave produces very well corrected, large aperture, exotic telescope designs mainly for non-visual use.

PlaneWave Instruments

Williams Optics sells smaller aperture refractors, also geared more towards astrophotography.  They produce very high-quality versions of a tried and true design with some higher tech innovations.  Both booths really showcased the quality of manufacturing from these smaller run shops.  Not to say that Meade or Celestron don't produce quality scopes, but the fit and finish from these two are difficult to beat.

Williams Optics

The REAL BIG Name

I spent a fair amount of time talking to the guy at the Thirty Meter Telescope (TMT) booth.  Observing is a part of the hobby I enjoy quite a bit, but I also have an interest in the science and technology of astronomy and this project has it all.  When complete, this will be the largest telescope ever produced.  Well, it might actually end up being the second largest, as the Europeans are working on a 39 meter scope.

The Thirty Meter Telescope Outreach Booth

It was fascinating to hear about the design of the scope, but also about some of the long term issues such a large telescope faces.  Many amateur astronomers are aware that the reflective coatings on mirrors degrade with time.  Often, mirrors are sent out for re-coating to restore their reflectivity.  To maintain the highest level of performance continuously, so that the massive investment can be best utilized, the TMT will be swapping out several mirror segments weekly for re-coating.  This will allow them to re-coat each of the 492 segments every two years.

After the first few minutes I was ready to donate to help the cause.  Turns out, they are not looking for donations, just doing general outreach.  Very cool.  If you love telescopes, the website is an interesting read.

The Vendors

Theoretically, all the booths were vendors, but there were only a few booths you could actually buy things from and take them home.  The two largest were Woodland Hills Camera & Telescope and Oceanside Photo & Telescope.  Both had nice booths with a wide selection of things to tempt the crowd.

Woodland Hills Camera & Telescope

OPT - Oceanside Photo & Telescope

Both offer special pricing, and no sales tax, at the show.  This makes almost everything at least 20% cheaper, so it's a nice time to buy.  If you don't feel comfortable deciding on your feet, they will honor the same deal if you call or visit their websites a few days after the show and mention PATS.  I found both crews to be very friendly and knowledgeable.

Among the vendors actually selling product was Howie Glatter.  He's an ex-hippie who now spends his time inventing and patenting useful things for telescopes, mainly in the area of collimation.  It was great fun to talk to him about his design and manufacturing process, and the merits of various types of collimation equipment and techniques.  He's very friendly and very knowledgable.  All his products were wonderfully machined, solid and well designed.

Howie Glatter, Inventor / Collimator

One of his products I had never seen before were nebula filters designed to fit over the eye lens of binoculars.  As soon as I saw this I was struck by the cleverness of the idea and his implementation.  Compared to the objective lens, the eye lens has much less area to cover, reducing price and weight.  To protect the delicate filter from eye gunk, he sandwiches it between two pieces of optical glass.  This allows you to clean them without worrying about scratching the coating.

Eye Lens Binocular Nebula Filters - Very cool idea

To affix the filters to the binoculars, he mounts them in a metal ring of various sizes.  By ordering a size the correct diameter for your binos, it can be held in place by the rubber eye guard.  You roll the cup down, place the filters over the eye lens and roll the eye guard back up holding the metal ring in place.  It's tricky to describe in words, but simple and easy when you see it in person.  If I were not planning on buying a new pair of binoculars in the semi-near future, I'd think about buying a set.

The Truth About 16" Scopes

As I was heading out, I saw that the Meade both was relatively empty and decided that I should really see what a 16" scope would be like to use.  I'm leaning towards this size, and I was hoping it would allow me to observe without a ladder or stool.  Sadly, I'm not so sure this would be the case.  

Me and a 16" LightBridge.  Notice they Eyepiece Height

One of the Meade reps was kind enough to take my photo next to the LightBridge pointed at Zenith.  I'm about 5' 6" tall, a bit under average for a male human, and there was a pretty wide gulf between my eye and the eyepiece.  There was another show attendee, slightly taller than average, who could walk right up to the scope and peer into the eyepiece... sigh.  I did not measure exactly, but I figure anything over 70 degrees would be a stretch for me on this 16" f4.5 scope.

So... what does this mean for my plans?  It means I have to think about them.  Observing at the zenith is uncomfortable anyway, so maybe it's not bad?  Perhaps a small box would not be too cumbersome?  Can I find an f4 mirror at a reasonable price?  Is a 15" a better size?  Would another structure offer a significantly lower eyepiece?  Are elevator shoes expensive?  There are a lot of questions to consider.  I'd love to hear your thoughts on the questions above, or about aperture vs. eyepiece height, or any experiences you have had observing with feet on, or off, the ground.  

The PATS Bounty

So I left the show with a lot of questions about my telescope design, but I also carried out some other things.  Before leaving I gave into the tempting opportunity to purchase a new finder scope.  I knew I wanted something larger than 50mm for my new scope and I was leaning towards an Orion ST 80, then I saw this great StellarVue 80mm finder.  

The StellarVue is an 80mm f3.75 achromat that comes complete with an erecting prism, helical focuser, and 23mm eyepiece with reticle.  It's roughly the same price as the 80mm f5 Orion with an erect image prism and 32mm plossl, both of which would provide about the same 3.9 deg TFOV.  

After some quick cell phone research and a few calculations I choose the StellarVue for two reasons.  First, it's shorter focal length means I can get an even wider 5.2 deg field of view with a 32mm plossl if I decide to upgrade it.  Second, it's just a bit over 50% of the weight of the Orion, which will help with any potential balance issues.

My Haul from the Show

You can see the finder, with mounting rings, in the picture above.  I thought the 50mm finder was large when I first got it, the 80mm is more like a small scope than a large finder.  It looks almost comical on the Orion XT8, but I think it will be much more proportional on my new scope.  The comical nature won't stop me from using it in the meantime though.

The extra aperture will be nice to hunt down some of the NGC objects and dimmer Messiers as I progress onto dimmer and more difficult objects.  The scope/finder should also provide nice views of the wide field objects like the Double Cluster, or the Coathanger.  I'm looking forward to sweeping it over the Milky Way under a dark sky!  As soon as I have a chance to try it out, I'll write up a review here.  That new moon can't come soon enough.

If you are in the Los Angeles area next year in September, I would suggest checking out PATS.  At the very least it's something to do between observing sessions!