Don Pensack

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.

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 have a 30mm, which is usable on my 12.5" f/5.75 (f/5, coma corrected) but not the future 16" f/4.3 (f/3.75, coma corrected). It's exit pupil is already larger than my pupil in the 12.5", but the secondary shadow would become visible in the f/4.3. My dark adapted pupil diameter is only 4mm, or a tiny hair larger than that. That makes eyepieces longer than 17.5mm in the 16" progressively more problematic as they get longer in FL. I could deal with up to a 22mm in the 16" (I have a 22mm), but not larger. I may keep both scopes, though, and just assign the 30mm to the 12.5". It also works fine in my 4" f/7. That's not the one likely to go, though. I have an 8mm I almost never use. I skip from 9mm to 7mm and the 8mm gets almost no use. I guess that's one way we know what to sell--an eyepiece that never gets used.

Trimmed down here too. Was 24, now 14. One will become unusable with a new scope (on order), so then 13. I have 9mm, 8mm, 7mm, 6mm in that range and the 8mm never gets used, so I may unload that one. But how do you choose which child to keep? Sophie's choice.

I wonder what the actual focal lengths are. Stellarvue sells the 7mm as 8mm and sells the 16mm as 15mm. I wonder if the measured focal lengths are in between.

That isn't field curvature you photographed, it's pincushion distortion. Field curvature is when the outer edge comes to focus at a different place than the center of the field, which is a different issue than distortion.

And the Mak is a lot shorter, so less of a wind sail for the mount, and less variation in eyepiece height from horizon to zenith, making it more practical for a shorter observer.

No 5 year old should use a telescope unsupervised. Unless the 5 year old is 5 going on 12, the scope would be destroyed in no time, by falling over and maybe on the child! Mom or Dad will need to be present at the scope with the child at all times.

The Pentax is not free of astigmatism at the edge, and would have vignetted in that scope as well. Add in a slight dose of lateral CA and a trace of FC, and yes, the edge is not perfect. See the tests at f/10: http://astro-talks.ru/forum/viewtopic.php?f=32&t=1483#p41976 go down the pages to the 2nd chart, which is significantly more complete. I believe the Lacerta ED is listed under both the Levenhuk brand and United Optics.

This isn't new, but illuminating (pun intended): https://www.cloudynights.com/articles/cat/articles/observing-skills/flocking-materials-test-stray-light-reduction-r82

The 16mm biggest aberration at the edge is astigmatism., even at f/10. The center is sharp but this deteriorates fairly quickly outside the center 25%. Edge stars appear defocused, but cannot be accurately focused because of astigmatism in the star images. I tried it in f/5.75 (coma corrected) and f/7. It was better at f/7, but I think it is better in scopes >f/10, like Maksutovs or Classical cassegrains.

Reminds me of the old joke: A ship went down in the north sea in the night and the people on board got off in their night clothes only. When picked up by a rescue vessel, one of the crew went down to the lifeboat to help people up the rope ladder. One sweet young thing in her nightie was shivering, so the crewman hollered up to the deck, "Is there a MacIntosh up there to help keep this young lady warm?" And a voice from the deck boomed back, "No, but there's a MacDonald here who's willing to try!"

That scope should be able to use 200-250x fairly easily in good seeing (4.8-6mm) There is no question a 7mm would be usable more often due to seeing, so might get more use. You already have an 11mm and a 5.5mm (11mm + Barlow), so what you could use is something in between. 11 + 40% = 7.9mm, so an 8mm eyepiece would be great. Halfway between 11mm and 5.5mm in focal length is 8.3mm, so again an 8mm. Halfway between in magnification, though, is 7.3mm, so 7mm splits the difference better. The problem is that your ability to use the 7mm Barlowed is unlikely, but the 7mm by itself would get a lot of use. The 9mm is a bit close to the 11mm in magnification and 5mm is too close to the 11mm Barlowed. So I second Louis' recommendation: 7mm.

Many people go searching for premium eyepieces looking for a sharper or clearer image on axis. Having owned nearing 400 different eyepieces over the last 6 decades, I can tell you that the axial difference between eyepieces is only a tiny fraction of the difference in seeing and transparency from night to night. You can be happy with a set of £65 eyepieces for nearly every type of object you'll ever view. BUT: --if you want an ultra-wide (or even wider) field of view because you prefer to take off the 'blinders'. --if you want star images that are center-of-field sharp all the way to the edge. --if you want eyepieces with superb contrast across that entire field. --if you want eyepieces that just 'immerse' you in the field so you forget you're looking through an eyepiece instead of a porthole into space. --if you want eyepieces you can use with glasses on to make it easier to see sharp star images and share the view with others without refocusing. THEN: --you will wind your way through series of eyepieces looking for the ones that fulfill your requirements. --you will try this and that eyepiece, always looking for the Holy Grail of eyepieces--the perfect one (hint: it doesn't exist) It is not lunar and planetary observing that pushes you in this direction, it is deep-sky observing. How low a power do I need? How large a field do I need? How high a power is usable? What eyepieces provide the most satisfying views? If I change scopes, will I change eyepieces? Do I need different sets for different scopes? How far apart should I space the magnifications? All of those are questions that take experimentation and experience to answer. You just haven't gone through enough eyepieces to find one that is just perfect for your use. Your scope is a high enough quality to justify some experimentation. Along the way (and you can buy used to save money and resell what you don't like very easily), you'll run into one that will just stay with you. In 1998, I bought a 22mm TeleVue Nagler. I found it immersive, easy to use, a very satisfying low power eyepiece with a nice bright image. It was like an old shoe that is just immediately comfortable when you wear it. It was just a great eyepiece in each of the 4 scopes I owned from 1998-2010, when I replaced it with a 21mm Ethos. But something always kept me from using the 21mm Ethos. It was a great eyepiece, but lacked that indefinable quality of immersiveness and ease of use. I found myself reaching for the 17mm Ethos every time. A trip to Australia in 2014 reacquainted me with a friend's 22mm Nagler again, and I realized what I had been missing since giving up the 22mm Nagler, but I still kept the 21mm Ethos. By 2020, my astigmatism had worsened and I needed to wear glasses at the eyepiece at that focal length, so I replaced the 21mm Ethos with the 22mm Nagler again. It was like coming home. I was once again using that focal length a lot and enjoying the view a lot more. Narrower field, yes, but that simply didn't matter. What did it take to get there? Experimentation. Long term use of both eyepieces. And an understanding that my reaction to the eyepiece was as important, maybe more important, than the eyepiece itself. I wasn't disappointed with the 21mm Ethos. I don't find the 22mm Nagler optically superior to the 21E in any way. But the view it gives just 'gets out of the way' and engages me with the field of view in a way the 21mm Ethos never did. It's an eyepiece that yields the same engagement in my 12.5" and 4" and will likely be my chosen low power eyepiece in my upcoming 16". Delighted? I wouldn't use that word. Finding an eyepiece that engages me in the process of observing? Priceless.

That was >20 years ago and over a hundred eyepieces. Sorry, no. I could be remembering wrong, too, since the groove on the barrel was so narrow and near the top of the barrel of the ones I sold several years later, they simply didn't interfere with insertion or removal. But the ones I owned were the very first production ('90s), and I don't recall them having an undercut on the barrels. If they did have the grooves, it was very different than current undercut grooves.

No question that for moon viewing one needs to suppress any internal reflections a lot more than the manufacturers typically do.

Only the very last version of the XL had an undercut. The set I had did not.

Pentax XW eyepieces have undercuts on the barrels. The older XL eyepieces did not.