My Current Eyepieces - A Lesson About Investing

A few weeks back I did a post about My Current Scopes.  I wanted to take stock of the two telescopes I have, share a bit about how and why I decided to buy them, and to ruminate about what each has to offer.  My goal was to help me get a better idea of what's important to me in a telescope by really thinking about my experiences to date, and to see if there was anything I wanted to sell or salvage in pursuit of my new telescope.

It seemed popular and elicited some useful feedback, so here is another somewhat rambling look at another part of my current observing kit; eyepieces.  I realized pretty quickly that eyepieces were a huge part of the observing experience.  Like most parts of a telescope, they can work well and disappear into the experience, or they can work poorly and remind you of their frustrating presence all too often.

Before I dive into my eyepiece experiences,  I'll warn its a bit long and can be technical in parts.  This blog is aimed mainly at people who have been observing for a while, so I'm going to assume a bit of eyepiece jargon knowledge.  If you'd like to get up to speed, or need a refresher, you might want to check out Astronomical Telescope Eyepieces: A Discussion for the Beginner.

My Eyepiece Menagerie with the XT8

Brand	Type	MM	Afov	Relief	X Pup	Mag	Tfov
Orion	Plossl	25	50	17	4.23	48	1.04
Orion	Epic ED 2	12.5	55	20	2.11	96	0.57
Orion	Epic ED 2	7.5	55	20	1.27	160	0.34
Teleview	Plossl	32	50	18	5.41	37	1.33
Teleview	Nagler 6	13	82	12	2.20	92	0.89
Teleview	Delos	6	72	20	1.02	200	0.36

If you are looking at the chart above and thinking "This seems a little haphazard" you are right.  They are listed in the order I acquired them and they seem to show an almost studied disregard for planning.  There is a story, and I've learned something from it.

The Story

The first telescope I purchased as an adult was my Orion XT8 dob and it came with the 25mm plossl eyepiece.  I used it for several observing sessions, enjoying the views and getting oriented in they sky again after a long absence.  The 25mm plossl gave pleasing views and was comfortable to use, but it was not long before I felt like I needed some options.  Particularly some higher magnifications for globulars, planetary nebula, and the occasional peek at one our solar system neighbors.

Orion Epic ED2s

After doing a very little bit of research and seeing some positive reviews of the relatively inexpensive ( < $100 ) Orion Epic ED2 eyepieces, I jumped in and purchased two; a 12.5mm and 7.5mm.  These gave me basically 2x and 3.3x times the magnification of the included 25mm plossl with a little more apparent field of view and eye relief.

I debated getting a 2x barlow instead of the 12.5 as it would give me the same magnification as the 12.5mm, and I'm not really sure in retrospect why I did not.  It might be because of the terrible barlow I had when I was a kid.  It really seemed to degrade the view, and with the added inconvenience of another set screw to work in the dark, I just never really seemed to use it.  Every time I purchase a new eyepiece, I think about a barlow, or powermate, instead.  Maybe next time....

The Epic ED2's did provide more options when I was observing, and I did enjoy the higher magnification on globulars and planetary nebula.  Looking back through my observing logs, the 12.5mm seemed to get a bit of use, but I seldom used the 7.5mm.  This is somewhat because I often view extended objects and through my 8" scope they can get pretty dim at high magnification, but I think it was mostly because both were uncomfortable to use, particularly the 7.5mm.

A few online reviews mentioned some issues with 'kidney beaning', darkening of portions of the field if your eye was not in the perfect position relative to the eye lens, but I blithely ignored them.  I had never really seen the effect before, the 25mm plossl was easy to view through, and it did not really sound so bad.  "Okay, so I just look through the eyepiece dead center, no problem at all".

Sadly, this was not as easy as I thought and it was just distracting enough that I found myself avoiding the eyepieces, even when an object probably would have benefited from some more magnification.  I'm not an optical engineer, so I can't really say why one eyepiece with 20mm of eye relief  would exhibit this issue, when another with the same eye relief would not, but these eyepieces seemed positively vexing to view through.  The 12.5mm seemed better in this regard, so it got more use than it's brethren, but even at their comparatively low price point, I felt I was not really getting my money's worth.

Enter Televue

Disenchanted by my experiments at the high end of magnification, I decided to expand my eyepiece collection in the other direction.  There are some great objects, or collections of objects,  that are over the 1 degree field my 25mm plossl provided.  I had also recently purchased my Celestron C6 and, with a longer focal length than my XT8, I wanted something that would provide a wider field.

The C6 has a 1.25" visual back, and I want to be able to share eyepieces as much as possible, so I started looking into the widest true field of view (tfov) 1.25" eyepiece I could get.  After some reading and math, A 32mm plossl seemed like the way to go.  There were some exotic designs that could squeeze a little more tfov out of 1.25", but they were pricey and it seemed like a lot of additional money, complexity, and optical surfaces, to get a very fractional increase.  Besides, I did enjoy the view through my 25mm plossl, and I was a little shy about more exotic designs based on my experience with the ED2's.

I'd read just about everywhere that Televue is the cadillac of eyepiece manufacturers.  Reviews of Ethos' or Naglers abound with tales of life altering views and hefty price tags.  So when I started looking at 32mm plossls I was surprised to see them among the results.  Amazon had them for a bit over $100, and I just happened to have a gift card, so I made the leap.

The eyepiece arrived a few days later and as soon as I opened it I felt good about my purchase.  It was well packaged in a substantial box, and it has the feel of fine craftsmanship.  The knurling was distinct, clean and even, and the text was crisp and easy to read.  These are small touches, but they added up the impression of a long lasting piece of kit.

When I took it out under the stars, the view was great.  It was a very comfortable eyepiece to use, had high contrast and a view as sharp as I had seen through my telescopes.  In short order it became my favorite eyepiece to use in both scopes and the double cluster with the XT8 and the 32mm became one of my favorite targets.

Eyepieces as Investments

My experience with the Televue 32mm plossl on the one hand, and the Orion Epic ED2's on the other, showed me how important an eyepiece is to my overall observing experience.  Since they can be used with any telescope I might own, and can last a lifetime with proper care, I decided I was going to invest in them.  I figured it would take longer for me to fill out my eyepiece case, but I hoped I'd be happy with each and not regret my purchases.

It was about this time that I wished I had more observing friends, or that I was part of an astro-club.  I could only scour reviews and go with my limited experience to decide on which eyepieces I wanted to save up for and purchase.  Looking through a variety of eyepieces owned by other people would have been a wonderful decision making tool.  I've still not joined a local club... something that I need to rectify sometime soon.

Nagler Type 6 13mm

A few months later I had saved up enough money to purchase a Televue Nagler Type 6 13mm.  It seemed like a good next step in magnification, providing a slightly smaller tfov than my 25mm plossl, but with almost double the magnification.  It's also small and light, which I really like.  No balance issues and it's easy to handle in the dark.

The Nagler 13mm has proven to be a spectacular eyepiece.  I really can't say anything negative about it, save for the price.  It seemed high when I purchased it, but it's become a staple of my observing and I never feel it get in the way of what I am viewing.  If there is an object that can take some additional magnification, I never hesitate to switch eyepieces now.  I do wish it was parfocal with the 32mm plossl, and I'm tempted to try some parfocalizing rings to make switching magnifications even easier.

Delos 6mm

To round out my eyepiece set I wanted something about double the magnification of the 13mm Nagler.  My first thought was a 7mm Nagler.  I was really pleased with the 13mm and the small size was attractive compared to other short focal length premium eyepieces.  As I was saving up and contemplating my purchase Televue released their first round of Delos eyepieces.

The Delos are designed for 72 degree, 20 mm eye relief at every focal length.  Early reviews were very good, comparing them very favorably to the legendary Ethos eyepieces, only with a smaller apparent field of view (afov).  As time went on, people posted head to head comparisons with similar focal length Naglers and it was pretty much universal that the Delos offered a better experience for a small (~12%) extra cost.

When I was ready, I spent the extra money and purchased the Delos.  I don't have a similar Nagler to compare it with, but I do find the sharpness and color rendition superior to my 13mm, which is absolutely no slouch!  It's incredibly comfortable to use, and my only issue is the size and weight.

Size Comparison: Delos 6mm, Nagler 13mm, Plossl 32mm

As you can see, it's somewhat of a beast.  Not the largest, or heaviest, eyepiece out there, but compared to the Nagler and Plossl, it's very large.  In the diagonal of my C6 it's almost comical.  Fortunately, I only have balance issues in my dob if I'm observing lower in the sky, and engaging the friction springs on the XT8 generally holds the scope in place.  I'd really like to do a side by side with a 7mm or 5mm Nagler someday just to see if the extra size is worth it.

The Lesson

I've been very happy with my more recent eyepiece purchases.  To me, and my observing experience, they were completely worth the extra money.  It was a learning experience, and I want to apply my lesson to my better telescope project.

My intention is to buy or build a telescope which will last me a long time.  Both in durability, and  usefulness.  I want to be frugal, but ultimately if I don't enjoy the observing experience, it will be a false frugality as I'll just end up purchasing another scope, or replacing cheap parts.

I've already been saving money for a while, and I expect that I'll be saving for a while to come before I can invest in my new telescope.  I'm planning to use that time exploring my options and thinking hard about where the quality/price sweet spot is for each component.  At least when I buy my new telescope, I'll already have some fine eyepieces to use!

Since I've narrowed my better scope down to something in the 14-16" range, I thought it might be interesting to plug a hypothetical 16" f4.5 scope into my eyepiece/telescope spreadsheet to see what I could expect.

My Current Eyepiece Collection with a hypothetical 16" f4.5

Brand	Type	MM	Afov	Relief	X Pup	Mag	Tfov
Teleview	Plossl	32	50	18	5.41	57	0.88
Teleview	Nagler 6	13	82	12	2.20	140	0.58
Teleview	Delos	6	72	20	1.02	304	0.24

Not bad, but eventually I expect to purchase some sort of wide field 2" eyepiece to get me back to a 1+ degree field, and perhaps add a bit more magnification to take advantage of the increased light collection and resolution a 3-4x jump in aperture might afford.

I'd be interested to hear what anyone has to say about their own experiences trying to balance cost and quality.  With plenty of time ahead to think about the issue, I'm sure there is plenty to learn.

Clear Skies!  I'm hoping to get out of the city to take advantage of the new moon.  I hope you can as well.