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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.
Cloudy Nights Article: May, 2015
"The Definitive Newtonian Reflector."
A discussion of the age-old question "Are apos really better than Newtonian reflectors?"
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.
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