A Better Scope

After observing for a few years, and attending a few great star parties, I decided I wanted to get a better telescope.   I currently own two scopes, more about them in a future post, but they each have some drawbacks for me.  So when I decided to start this project and spend a year trying to get the telescope I really want, a scope that would let me do the observing I like for a long time to come, I had to start thinking about what that would be.  I had to start thinking about some design requirements.

There are lots of great scopes out there, many better than my workhorse Orion XT8, but each in different ways.  I do all sorts of observing, but my favorite objects, the ones I spend the most time observing and go back to again and again, are deep sky objects: Galaxies, Nebula of all sorts, and particularly, globular clusters.  Oh the majesty of a beautiful globular cluster!  I usually observe whatever bright planets are in the sky on my observing nights, but they are secondary to the main event.  So I want a telescope fit for deep sky hunting!

Requirement #1: Aperture

All my favorite objects are dim... so aperture rules the day.  The larger the main mirror or lens, the more light gathered and the brighter the image.  Increased aperture also provides some benefits on resolution, so that’s a plus as well!  With that in mind overall aperture is one of my main requirements.  If it was the only requirement, I’d just get the biggest honking mirror I could and build a scope around that.  Alas, I have some other constraints and considerations.

Requirement #2: Portability

Living in Los Angeles, CA, if I want to see anything aside from the two dozen brightest stars in the sky, I have to travel.  I am fortunate enough to have a semi-permanent observing location in Joshua Tree, CA, where I can leave a telescope, but I still need to move it outside to observe.  There are also several yearly dark sky star parties, like the GSSP, which I would like to continue attending.  Perhaps I’ll even get to the Oregon Star Party... people say it’s REALLY dark.  All of this means that whatever scope I have, it has to be mobile.  I’m going to say I have to be able to lift and put it together myself, and it has to fit into an average car.  

Requirement #3: Economy

Hey, I’m not made of money.  I’d like to have a fancy 20” Ritchey–Chrétien, with it’s flat and coma-free field, but that will have to wait for another day.  I want the most aperture I can get for the least money.  I want to spend where it counts, aperture, optical/mechanical quality, and save on everything else.  Fortunately, there are some things I know are NOT important to me that I can give up.


Trade Off #1: Tracking

At this point I’m pretty much a dedicated visual observer, and I don’t mind pushing the scope around.  I usually use lower magnification for wider fields, so it’s not tough to track by hand.  Astrophotography is great, and I’ve done some wide field imaging with a tripod and DSLR, but the real deal is a something I can live without for the next while.  I love seeing the dedicated guys at the star parties, their kit is awesome, and they produce some jaw-droppingly beautiful images, but you gotta give some things up in any design, and this is one I am willing to let go.  By foregoing this ability in my design, I’ll save a ton of money.

Trade Off #2: Goto, Push-To, DSC’s, etc.

This stuff is great, but I LIKE hunting down faint objects with nothing more than a good star atlas, my trusty telescope, and lots of effort.  I enjoy observing, and the thought of zooming from one object to another is intriguing, but I find there is a great reward in learning the sky and star hopping to find that elusive thing.... whatever it is.  It might be nice to add Digital Setting Circles later, for finding tough objects, or if I’m just feeling lazy one night, so I’ll try to keep the design open to it, but I’m definitely willing to go without for the sake of the budget.

Trade Off #3: Refractor Like Views

I was not entirely sure how to encapsulate this point.  At first it was going to be Image Quality, but I certainly want the best image quality I can design into the system.  However, I am willing to put up with a few things that will enable more aperture.  A really good telescope based off a lens, a refractor, will give outstanding views; Contrasty, highly detailed, velvet black field, just beautiful.  I’ve seen the view through a good 5” apo-refractor and it was stunning.  But, it was painfully expensive, and that 5” of aperture is never going to show the same objects a 10” scope will... no matter how good the optics.  I’m okay with some coma, a side effect of most large aperture designs, and diffraction spikes... if it gives me another magnitude or two.  

The Winner Is...

With this subset of requirements:  Aperture and Economy, and the allowable trade-offs it seems pretty clear that a Newtonian design, on a simple altazimuth mount, is the way to go for me.   I’m pretty lucky that there has been a LOT of exploration of this design space.  John Dobson pioneered this thinking in the late 1960’s, creating the Dobsonian Telescope. There is a reason most 10+” scopes, and just about every 16+” scope at star parties are of this general design; It’s robust, it offers large aperture at low cost, and it can be made portable, fulfilling my third requirement.

So now that I know basically what I am looking for, I can start filling in some of the details.  How big is big?  What can I actually move from place to place?  Do I buy this thing, or build it?  What am I going to need to spend on this better telescope? I'll be posting my thoughts on the details of the design in another post.

Clear Skies