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A Word About Eyepieces


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A Word About Eyepieces

by Ed Turco

 

Amateur astronomers today have almost too many choices when it comes to eyepieces, from the sublime designs of Al Nagler to the unlabeled “cheap stuff” we all see on the internet.   It is a long cry from seventy years ago when an eyepiece might be a Ramsden or a Kellner, or if one could afford it, an orthoscopic.  Added to these might be the occasional war-surplus material Erfle from Edmund Scientific!  Such Ramsden and Kellners had small, under 40 degree or less APOVs; an Erfle might be 70 degrees, but only a useful central field of 40 degrees.  It was a lucky amateur who had three eyepieces accounting for roughly $30, almost the same as a 6” telescope constructed at home.

 

Nowadays, a set of eyepieces can be cost more than a thousand bucks, and considerably more if one wants to spend the time and the money.   In contrast, many amateurs have been warned that the cheap Internet eyepieces are to be avoided as they don’t perform well and they come from China, whatever that means.  In the 1950s, we were similarly warned about “junk” from Japan, until Binolux, Goto and Unitron came along.

 

A lot of advice has been offered by some who seem to have never looked through such eye-pieces. Others who have actually tried, report on Cloudy Nights that most of these aren’t bad at all.  Indeed some of the unbranded items look awfully familiar.  Browsing on Ebay enough times,  I decided to try them out and bought some; here they are!

 

 

 

 

 

Included in the above collection are 1.25” eyepieces with focal lengths of 40, 32, 26, 16, 9 and 6mm focal lengths.  The ones on the right, with the gorgeous polished barrels are Barlows of 2 and 3 times amplification.  I’ll get to the big guys in the upper left later.

 

I have to admit that I couldn’t take these out and scan the heavens as much as what I would like (the story of my arthritis can be found in my other CN article cited below) but  I did considerable testing on terrestrial objects to see what they could do.  And with my over sixty years of experience at this sort of thing, I’ve been able to interpret the appearances of terrestrial objects (the appearance of my neighbors’ mottled asphaltic roofs) and extrapolate them to celestial performance. 

 

Quite generally, the quality of my samples’ fit and finish are above reproach.  The lenses have darkened edges, the lens’ polish are excellent.   They come with rubber eyeguards are in boxes (that seem to be very important so some people) Their performances were typical for the Plossl design.  The APOVs were at the normal 52 degrees.   Others, when I did a little research on the specifications, I found eyepieces with wider angle APOVs near 60 degrees.  All it took is a search within the Ebay category to pick up wider field eyepieces for a few bucks more than the regular Plossls.; as such they have eye relief that won’t make it tough for eyeglass wearers.

 

The 9 and 6mm models merit extra attention; they have a Smyth lens setup that amplifies the power of longer wide-angle eyepieces.  Their APOVs` are 68 degrees or even a little bit better.   The eye relief on both is 20mm.  I haven’t mentioned prices so far but I’ll drop a preview hint of this entire set -- $60!  These work wonderfully for the price and I have actually used these to get great peeks at the moon and I have no complaints.

 

 

The Barlow lenses perform perfectly well, in either the 2 or 3 power magnifications; one is enough.  At $10 to $20, you can afford a few to put on your mantel.  Try that with Naglers!

 

 

The entire set is about perfect for any f/6 or slower telescope.   A full set will put you back (are you ready?) $200!  You might get lucky down to f/4.5 with these depending upon the amount of coma you can tolerate; you must skip the 40mm eyepiece as its exit pupil gets wider than what your eye can handle.   And, please remember that if you insist on making an f/2.8 reflector, you may have trouble using any company’s eyepiece.

 

Was there a downside to with my purchases?    I found a few that had single layer instead of the multilayer antireflection coatings.  Judging from the overall good workmanship of these eyepieces, I was disconcerted by this – but not for long.  My second complaint is that the sellers don’t market these eyepieces as sets, and that would make a purchaser’s job a lot easier.  Also, you may have to order from different companies for different eyepieces.  Sometimes there is overlap between companies, sometimes not.  Be ready to do some homework and spend time getting obtaining  the eyepiece/s you want!     

 

Someone is going to say that I forgot the 2” models at the rear of my picture.  If your telescope has a 2” eyepiece holder, you can always get an adapter for the little one and-a-quarter-inch guys.  The two inch models come in 40 and 30mm focal lengths; bigger lenses make for a wider apparent field in a wider barrel, call them 65 degrees.   I didn’t pay enough attention and missed out of buying a 25mm in the 2” size.   This serves to remind again that an hour’s work is necessary to get what you want.  Finally, if you want the 2” models in 40, 32 and 25mm focal lengths instead, you must add another $75 to that $200 price.

 

I can only conclude that prospective buyers can get a good set of eyepieces at great savings. Statements about cheap low quality eyepieces made in China are not necessarily true!   And remember that just about anybody’s eyepieces come from China these days!

 

Finally, in this COVID era, there is more good news -- a beginning ATM or amateur astronomer with limited resources can get this eyepiece set and begin his hobby better equipped than he would think.  I think it is better to have a set of eyepieces than a single high-priced eyepiece.  Isn’t having only one magnification a little boring?

 

Chinese makers also offer zoom eyepieces and aspheric models.   I cannot offer evaluations of them, but I suspect that they will give above average performance.  If you make an f/6 telescope you cannot go wrong!

 

 

The usual disclaimer:  I have no connection with any Chinese eyepiece manufacturer.

 

 

 

Ed

 

 

 

 

Cloudy Nights Article: May, 2015

 

"The Definitive Newtonian Reflector."

A discussion of the age-old question "Are apos really better than Newtonian reflectors?"

 

http://www.cloudynights.com/page/articles/cat/articles/the-definitive-newtonian-reflector-r2983

 

 

Sky and Telescope articles:

 

"Making an Aplanatic Telescope." Nov. 1979: 473-7.

"Tripods from Crutches." Jan. 1996: 31.

"A Scavenger's 12-Inch Telescope". Apr. 1998: 96-7.


  • Stargazer3236, davidc135, davelpg and 2 others like this


8 Comments

 Ed,  What brand are those big 2" 40mm and 30mm eyepieces?

 

Thanks,  Martyn

Ed,

What happened to all the comments about your wonderful article?

 

Ah, another thread, sorry.

Photo
Astro Canuck
Nov 13 2020 01:38 PM

 I have only a Meade 9mm - gives a soft image though.. all my other eyepieces 40mm-10mm plossls are Soviet-Russian made TAL. they give nice views and happy with.  

    • mr.otswons likes this

 I have only a Meade 9mm - gives a soft image though.. all my other eyepieces 40mm-10mm plossls are Soviet-Russian made TAL. they give nice views and happy with.  

I am pleasantly surprised with eyepieces that came with my TAL-1. Multicoated and clear, very nice barlow too!

Photo
Stargazer3236
Nov 14 2020 10:15 AM

I bought a set of SvBony wide fields, 20mm, 15mm, 9mm and 6mm with AFOV of 68 degrees. I paid $130 for the set. Now, I normally would not use eyepieces as my favorite way of observing is with my ZWO cameras and my laptop. However, I decided to buy a set so I could use them during object acquisition before inserting the camera. I would say that they are clean FOV. Not many aberrations,  Hardly any coma and near tack sharp edge to edge viewing. I am surprised. I could afford naglers, but since I don't need them, why buy them?

I’ll preface this by saying that I’m a visual observer and not much of an astrophotographer at this time. I agree about the usefulness of Plossl eyepieces.

 

I recently purchased the forbidden Celestron 1.25” Eyepiece and Accessory Kit. Amongst many other useful items the kit contains five Plossl, 4 element, 52 degree eyepieces. I have a new 102 mm, f/4.5 achromatic refractor telescope and I wanted to see what range of eyepiece focal lengths were practical in such a fast scope. My existing EP set are 0.965”. I don’t have anyone to swap with so I figured this would be a good way to determine what focal lengths of “real” eyepieces I could purchase in the future.

 

To my surprise it turns out that I’m completely satisfied with the quality of these Plossls. They are well constructed and their standard fine threads mesh smoothly with the included filters. The images are sharp and aberration free all the way to the edges of the field. Their eye relief is fine except for maybe the largest one. The only negatives are that the 32 mm exhibits too much eye relief and suffers from blackouts or “kidney beans” and the 6 mm doesn’t buy me anymore detail as probably expected. Both “defects” may be the result of their combination with my f/4.5 telescope and not necessarily the eyepieces themselves. 
 

My only comparison is with my Bresser 20 mm Plossl 5 element eyepiece with a 70mm degree AFOV. It gives me beautiful DSO views but with slight comma astigmatism on the outer 20% of the FOV. Granted, since I don’t have any $250+ eyepieces to compare too in this scope I may not know what I’m missing. However, except for greater AFOV I don’t know what could be improved upon compared to these good Plossls that I have. I am open to enlightenment. 

Reality is, it's cheap to manufacture spherical even aspheric lenses today which has drastically reduced the price of these eyepieces.  An eyepiece like the Svbony 60 deg. aspheric would in the past cost $100.00, but now a set of 3 is $27.00.  However, there are idiosyncrasies that some of these eyepieces have that higher level eyepieces don't.  Some are bad at the edge except in longer telescopes.  Some have oddball reflections.  But on the whole, they are a major step up  from the ancient Huygens and Ramsden eyepieces of years past, wider fields, better eye relief.

Thanks for the article. I agree with your premise in general. I have the SV 4, 10 and 23mm aspheric eyepieces; now rebranded by Meade. I believe the 10mm was the weakest. I also have the 9mm 68 and a 16mm clone which are surprisingly good in my Meade infinity, SCT and Mak. I also tried the zoom which was narrow but actually good and crisp at the low to mid powers.

 

I often use an off brand 30mm /80 which works very well as a finder in my Dob and cost only a fraction of the premium brands. I have a few high-grades which seem to perform noticeably better than the off brands especially in my faster scopes; a Meade 14mm /84; 20 RG, ES 24mm/68 and a Badder Zoom. If I had to make hard choices I would keep the Zoom and the 2 Meade’s but replace the rest with off brands.



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