Don Pensack

TeleVue Apollo 11. It's close to the ideal magnification in the dob and its 85° is usable with glasses on.

I never saw one with a rubber gripper on it. The rubber grip ring sticks out beyond the barrel on that eyepiece, i.e. there isn't a machined groove for it, so I wonder if the factory added them later upon request? The 25mm in the image has no rubber grip ring on it. Did it break off? It also looks like the longer one had a rubber eyecup at one time that might have fallen off from age, maybe?

Or an accessory lens to extend the eye relief. Or a lens to lengthen the focal length. Some experimentation is in order.

If the interest is more for high powers, then yes, it makes sense.

Pleaides would be excellent with a 30mm eyepiece that has no astigmatism, like an APM 30mm Ultra Flat Field--2.77° with a 750mm focal length. Coma can only be solved with a coma corrector. If the astigmatism is in your eye, you'll see it in the center of the field as well as the edge. If only at the edge, it's the eyepiece

Yes, it was intended to be a value line for Meade. They never had rubber grippers around the exterior. Like the 4000 Series, the first ones had no rubber eyecups but the later ones did. I don't think Meade brought then in very long because they disappeared about the same time Meade started bringing in the Series 5000 eyepieces from Jing Hua. The Series 4000 "Super Plössls" had maybe 7 or 8 different versions, the first 3 from Japan: 5 element no rubber eyecup, 5 element with rubber eyecup, and 4 element with rubber eyecup. When the S4000 became the "value line", the S3000 disappeared.

That's a good question. It also isn't 48°, it's 43°. The goal is to get a large exit pupil, low power, and wide field at the same time in an instrument not designed for it. I like your thinking on the small ED refractor--it can even be mounted piggy-back on the large SCT.

The primary issues, as I see them, are: --how comfortable will you be in the dark to be unscrewing the lower section of the eyepiece and installing the fine tuning rings? --the eye reliefs change as the magnifications change. Will you be uncomfortable if the eye reliefs change? --you will quickly learn that the eyepieces sans lower lens are not very good. With the bottom lenses added, the eyepieces are a LOT better. Would you be better off with the 21mm and 10mm as a pairing? --the eyepieces will display some possibly noticeable (varies from observer to observer) vignetting with 42mm of rings added. Could you get by without the 2 rings together is not going for close double stars?

When I did auto racing, we used to refer to "driving at 9/10" or "driving at 10/10". If you never drive at a level above 3/10, then the really fast cars are barely utilized, and there is very little difference with slower cars. As your observing skill improves, you are moving up the scale, like the driver moving to a higher level. It is at that point that the differences in eyepieces start to become apparent, and, once seen, important. And your observing skills do improve with hours spent doing it. It's like playing a piano--with a lot of practice, you can play Chopin and understand all the nuances, where the beginner starts out with Chopsticks. Observing teaches the eye and the brain how to see. But, like the race car driver, being able to drive at 10/10 doesn't mean you can afford the faster car. And a limited budget pay pull back on expectations. There are a lot of very nice, non-limiting, eyepieces available today for £200-£350 that can satisfy even the most experienced observers. Once the eyepieces get above a certain level, the differences are more in the observer and the atmosphere.

I think it is like a moving field stop where first one side of the field is illuminated, then the other as your head moves. I seriously contemplated pulling those adapters out of the packages when I started selling the eyepieces many many years ago, but there are people who use the eyepieces that way.

I have owned ~370 eyepieces and looked though many many more over the last 6 decades. To my eye, no company producing an eyepiece for 50% the price of a TeleVue has equaled the TeleVue eyepiece. None. No copy by anyone has equaled the original. There are eyepieces just as good, though, but they seem to sell for more. And there are eyepieces that are pretty close that sell for less, but a multi-point comparison will reveal the differences. That doesn't mean you won't be happy with the lower-priced eyepieces, though. For example, an out-of-focus field stop doesn't matter to me at all, so I may note that an eyepiece has that, but it wouldn't be a deal-breaker for me. However, astigmatism at the edge of the field is my bête-noire, and even a little bit leaves me looking for a replacement. (not that such a search is always successful--there is NO perfect eyepiece). People ask me all the time if there is a $300 eyepiece that is "the same as" a $600 eyepiece, and I answer no. A $25K car is not the same as a $50K car. But it can be very close--so close in some cases, it just might be the true bargain everyone is looking for, with 98% of the performance for 50% of the price. Such eyepieces are few and far between, though. And a careful reading of the threads here on SGL and on other forums reveals which they are. What can be fairly said, though, is that there are some terrific eyepieces for less; in some cases a lot less. And if you want eyepieces compatible with eyeglasses, TeleVue has some, but is not the only game in town.

There is this site, where he tests eyepieces at f/4 and f/10: http://astro-talks.ru/forum/viewtopic.php?f=32&t=1483#p41976 You can go way down the page to the second chart where the links to the original tests can be found (plus a LOT more eyepieces. And then, these, where eyepieces are tested at f/3.5 and f/7: https://web.archive.org/web/20110622011950/http://cieletespace.fr/files/InstrumentTest/201102_test_oculaires.pdf https://web.archive.org/web/20130829052725/http://www.cieletespace.fr:80/files/InstrumentTest/201306__6_oculaires_10mm.pdf

Characteristics to look for when testing an eyepiece: Date__________________Scope______________ Eyepiece_______________________________Day Night 1. spherical aberration_________________________________________________________ 2. coma_____________________________________________________________________ 3. astigmatism________________________________________________________________ 4. field curvature______________________________________________________________ 5. distortion--type and amount___________________________________________________ 6. chromatic aberration--axial and lateral___________________________________________ 7. apparent field_______________________________________________________________ 8. eye relief___________________________________________________________________ 9. light scatter control--field and star outside field (glare)______________________________________________________________________ 10. SAEP_______________________________________________________________________ 11. CAEP_______________________________________________________________________ 12. Tint________________________________________________________________________ 13. Vignetting___________________________________________________________________ 14. Transmission_________________________________________________________________ 15. thermal issues________________________________________________________________ 16. field stop focus_______________________________________________________________ 17. impression of contrast_________________________________________________________ 18. EOFB_______________________________________________________________________ 19. Sharpness on axis/50%/edge____________________________________________________ Other comments about eyepiece____________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________ _______________________________________________________________________________

The f/6.3 focal reducer is also a field flattener, so improves the image quality over f/10, and the lower power sees less interference from seeing.

It affects the exit pupil. Normally, the exit pupil is solidly positioned behind the eyepiece. With the adapter, the exit pupil seems to float as first the field of view is on the right side of the eyepiece's actual field, then on the left side, then top or bottom. The exit pupil becomes a "floating" pupil and makes the eyepiece incredibly annoying to use. I really don't know why they made or included that adapter. OK, it's not an aberration per se, but it does render the exit pupil "difficult".

Whatever you do, don't use the conical 1.25" adapter with the 31mm or the 36mm. The adapter severely limits the apparent field and causes all kinds of exit pupil aberrations.

The ES 24mm has always had a conical taper undercut on the barrel. I've seen them since the 2009 beginning, and they've always had that. It's a conically tapered undercut rather than a cylindrical one, but it is an undercut nonetheless.

Excellent for deep sky: Great for planetaries, globulars, double stars. Not great on the Moon (a bit too much internal scattered light), and edge of field astigmatism is more noticeable on the Moon because it fills the field. And there is residual chromatic aberration. However, the sharpness and astigmatism is f/ratio dependent. At f/5, it's so-so. At f/10, it's excellent. So it might be very good for the Wookie with all those long f/ratio scopes!

Yes, correct. If the scope has significant field curvature, like a 60mm F/6 that is not field flattened, a flat field eyepiece won't necessarily be the best image quality across the field. | + ) = ) In narrow 45-60° fields, field curvature is less of a problem that when the apparent field gets wider. The field stop widths of the eyepieces in question: Panoptic 24mm--27.0mm ES 24mm x 68--27.2mm APM 24mm UFF--27.3mm Having used all 3, it seems to me that if all 3 were stopped to 27.0mm, they'd all be sharp to the edge. But the APM 24mm, though the most comfortable one of the 3 to use in the field, has the most issue with star image quality right at the edge. I think that can be ignored because you don't seriously look at any object, even a double star, right at the very edge of the field. It isn't as sharp at the edge as the Panoptic, but it does have noticeably less pincushion distortion.

The coma corrector will require some in focus. Whether it will substitute for any of your extensions, I can't say. That eyepiece has its focal plane 9mm above the 2" shoulder it sits on, so add 9mm to the height of the top of the proposed coma corrector to get the distance from the lens to the focal plane of the eyepiece. Subtract that figure from 73.5-75mm to get the length of the spacer you need to add in between the lower section of the CC and the upper. Once you've added that spacer, you place translucent scotch tape across the 2" opening of the CC in an X pattern. Put the CC in the scope, point the scope at the moon and focus the moon on the tape. Remove spacers, adapters, or extensions in your focuser as needed until you can achieve focus on the tape across the CC. Then, freeze or lock the focuser at that point. If you remove the tape, the 20mm should be close to exact focus as you slide it in. All your other eyepieces will need to be pulled out of the CC to get them to focus (remember, NOT moving the focuser). Where each eyepiece comes to focus, sliding it out, is its correct position relative to the CC lens. For repeatability, you can add parfocalizing rings to the eyepieces so they automatically stop at that point when you slide them in. Eyepieces that require an unsafe amount of pulling out of the CC should have a barrel extender added so the position is not unsafe for the eyepiece. You will essentially parfocalize your eyepiece set so the CC is at the correct position in the light cone from the primary mirror and so each eyepiece is at its correct distance from the CC lens. It is unlikely you'll get everything EXACT, so after you parfocalize everything, you'll still need +/- 1mm of fine focus at the focuser, but that small a difference won't matter. Any new eyepiece you buy will be parfocalized to your other eyepieces so it, too, will be at the correct distance from the CC lens. The need to parfocalize your eyepieces and find a spacer of the correct length is one of the pains of using this coma corrector, but you only need do it once, so it's not that big a chore. The Explore Scientific and TeleVue coma correctors have adjustable tops to do the parfocalizing for you without rings added to the eyepieces, but they are a lot more expensive. And, you can parfocalize all your eyepieces first to save time later. You parfocalize all your eyepieces to the eyepiece that needs the most in-focus of all your eyepieces. In this case, that is likely to be the 20mm Myriad.

One thing to bear in mind: The top is too short to put the eyepieces at the correct distance from the lens, though it would work for imaging as is. An additional spacer needs to be added between the upper barrel and the lens barrel. How much spacer will be determined by the position of the focal planes of your eyepieces that require the most in-focus of all your eyepieces. It is often around 19mm but will vary according to your eyepieces. This thread should make it clear: https://www.cloudynights.com/topic/462985-setting-up-the-gso-coma-corrector/

Look up posts and reviews for the GSO coma corrector, which is what this appears to be (and for a good price, too!!).

I posted the rules as explained to me by reading back in the '60s above. I don't usually pay attention to those rules, though they make sense from the standpoint of magnification and exit pupil. What I typically use is: <100x low power 100-200x Medium power 200-300x High power >300x Good luck with seeing. Ultra high power. In my scope, that is low <8x/inch (exit pupil 5mm down to 3mm) medium 8-16x/inch (exit pupil 3mm to 1.5mm) high 16-24x/inch (exit pupil 1.5mm to 1mm) uber high>24x/inch (I max out about 40x/inch) Exit pupil 1mm down to 0.6mm What do I look at?: low--large star clusters, large nebulae, multi-object fields. Less than10% of use. medium--almost everything except planets and planetaries and Moon, Use about 70% of the time high--moon, planets, planetaries, small star clusters, most globulars, double stars. Use about 20% of the time ultra high--small planetaries, Neptune, Uranus. Use about 1% of the time. It's obvious to me that I could be happy with magnifications from 100-300x and exit pupils of 3mm to 1mm in the 12.5". I cannot apply the rules above to my 4", where I typically use exit pupils from 1mm down to 0.5mm. Why so small? I don't really like magnifications <100x on most objects. The only problem is that makes most objects dim in the 4". If I want really wide fields and super low powers, I'll use binoculars.

Sorry to disappoint, but the eyepiece is from China and sold by other companies as well, notably in the past by Bresser, Meade, Orion, et.al. The Antares name on this one is merely a private label, though that is OK. That doesn't mean anything other than that the eyepiece is not unique to Antares, nor made in Canada. It's a 5 element eyepiece, so don't expect the outer 20° of field to be well corrected below f/6. It stands a chance to being OK in the f/11.4 scope, though. Keep us posted on your evaluation of how it works for you.

[I think there's a fellow on CN named Bill Rose whose collection is large enough he can't photograph them in one shot. "She never mentions the word addiction in certain company" LOL.] I got to thinking about the number of eyepieces that you need to have a full set. Low power: 3.5-10x/inch Medium power: 10-20x/inch High Power: 20-30x/inch UltraHigh power: 30-50x/inch I can see a reason to have 2 eyepieces in each slot = 8 eyepieces. If your seeing is always poor, maybe none in the UltraHigh category = 6. But then there are the observers who like to have specialty eyepieces for planets, so add maybe 4 more. So you can probably rationalize 10-12 eyepieces. Now, if you have a really good 2X Barlow, you can cut the number of eyepieces and use the Barlow, though I rarely see that. Barlows are often added to already considerable collections, LOL.