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Second Time Around

20-22mm eyepiece with Dioptrx

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Hi, apart from buying from the classifieds this is my first post here.

I've recently returned to astronomy after several decades and, amongst other things,  just bought a used 10 inch tenth wave f/4.8 OOUK Dob and an Explore Scientific Coma corrector.

I've measured my dark-adapted pupil size at 4.5mm, so I'm after trying various wide field 20 to 22mm eyepieces, but as I have astigmatism will be using a Dioptrx.

I've got a 20mm Pentax XW on the way, and have also shortlisted a 22mm Nagler and 22mm Vixen LVW to try if I can find them secondhand.

Any comments on the above 3 would be appreciated.

Are there any other eyepieces I should consider in this focal length that'll take a Dioptrx?

Many thanks.

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I use the 22mm AstroTech AF70 (Celestron Ultima LX, Olivon 70, etc.) and 22mm Nagler T4 with glasses to correct my astigmatism.  The Nagler is wider and slightly better corrected, but more difficult to take in the edges.  I've never tried the 22mm Vixen LVW, but it's supposed to be really good.  The 20mm Pentax XW is supposed to have field curvature, so if you also have presbyopia (think bifocals or progressives), the edges might not be in focus when the center is in focus.

The 20mm APM XWA HDC Hyperwide might be usable with a Dioptrx and gets good reviews.  The 21mm TV Ethos is certainly usable with Dioptrx, but is vastly expensive.

Here's a comparison image of some of my 20mm-ish eyepieces along with their fields of view:

1833175478_18mm-22mm.thumb.JPG.b2a9f1289172154a138f3813b09da0a4.JPG1381562251_18mm-22mmAFOV.thumb.jpg.88386d195597c48c65f2953c28d718d7.jpg

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Many thanks for the advice and all the trouble you've taken, Louis!

Luckily I don't have presbyopia, just myopia.  I've found the most practical way for me to observe is without my glasses as I can then also focus on a tablet showing Sky Safari as well.  I keep my glasses on a cord round my neck and put them on for a naked eye view.

The 20mm  Pentax has now arrived - I just need a clear night to try it.

Thanks for the heads up on the AstroTech and the APM; I'll certainly look into these.  Does anyone any experience with these plus a Dioptrx?

Has anyone tried a 21mm Ethos with a Dioptrx?  Given that the Dioptrx reduces the effective eye relief will there be enough?

Any other suggestions gratefully received.

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I've read that the Dioptrx will grip outer diameters from 41mm to 44mm.  If so, the AT AF70 has a 43mm thread once the eyecup is threaded off, so it should work.  It has more than enough eye relief for comfortable use with eyeglasses, so that shouldn't be an issue.  The AT AF70 is discontinued, but the 22mm Omegon Redline SW is still available new and is identical in all respects but name.

I've read that the top of the Pentax XWs can be screwed off and the Dioptrx placed inside and the top threaded back on.  Since the revealed thread is also 43mm on the Pentax XWs, you could experiment to see if the Dioptrx will fit on it prior to getting the Omegon Redline.

Instead of using Dioptrx, I bought a pair of dedicated distance eyeglasses with my cylinder (astigmatism) correction that I only wear for stargazing.  I got them made with low index plastic lenses to reduce chromatic aberrations introduced by high index lenses.  Having dedicated, single vision glasses reduces the cost of replacement if I scratch them on an eyepiece and reduces the accumulation of microscratches that degrade the viewing experience.

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I use a Dioptrx with a 22mm Nagler and as you would expect it works perfectly.

The 22mm Nagler has good eye relief so you will have no problem with using a Dioptrx or using glasses if you wanted to.

My eyepieces for use with my dobsonian are mostly Delos for the 20mm eye relief, and then a 22mm and 31mm Nagler with 19mm eye relief.

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Thanks, Louis and Paz.

I'm somewhat disabled so am limited to short observing sessions thus I imagine comfort is going to play a big part.   It also means I'm limited to this particular scope for my light bucket. 

I found that with the Orion Optics UK Dobs I can manage a 10 inch, but am limited to an 8 inch with other makes, due to both weight and bulk.  I'd therefore like to get the best quality views I can, and so cost is well down the list of considerations.

Due to inexperience I don't yet know what I'm looking for - eyepieces have certainly come a long way since Ramsdens and Kellners my first time round!  I suspect that I'll end up with the 22mm Nagler, but I'd like to try lots of other candidates.

Thanks again for the input and please keep comments coming - I've got a lot to learn!

Edited by Second Time Around

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Baader Hyperions take dioptrx well - there’s a 21mm in the range I think, though they’re not normally recommended for fast scopes. I had one and liked it - but only used it with an F/10 C8. Probably not the best choice for your dob.

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22 hours ago, Highburymark said:

Baader Hyperions take dioptrx well - there’s a 21mm in the range I think, though they’re not normally recommended for fast scopes. I had one and liked it - but only used it with an F/10 C8. Probably not the best choice for your dob.

As you say, probably not for a fast Dob. However I'm very pleased with my Baader Hyperion Zoom.  The  only downside is the narrow field of view at low powers, which of course is what this new wide angle eyepiece is for.

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22 mm Panoptic takes a Dioptrix, according to the table on the Tele Vue website. Discontinued but available used. Stunningly sharp eyepiece.

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On 5/11/2019 at 15:23, Louis D said:

I use the 22mm AstroTech AF70 (Celestron Ultima LX, Olivon 70, etc.) and 22mm Nagler T4 with glasses to correct my astigmatism.  The Nagler is wider and slightly better corrected, but more difficult to take in the edges.  I've never tried the 22mm Vixen LVW, but it's supposed to be really good.  The 20mm Pentax XW is supposed to have field curvature, so if you also have presbyopia (think bifocals or progressives), the edges might not be in focus when the center is in focus.

The 20mm APM XWA HDC Hyperwide might be usable with a Dioptrx and gets good reviews.  The 21mm TV Ethos is certainly usable with Dioptrx, but is vastly expensive.

Here's a comparison image of some of my 20mm-ish eyepieces along with their fields of view:

1833175478_18mm-22mm.thumb.JPG.b2a9f1289172154a138f3813b09da0a4.JPG1381562251_18mm-22mmAFOV.thumb.jpg.88386d195597c48c65f2953c28d718d7.jpg

Nice rulers. I'm from Iowa, too.

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3 hours ago, munirocks said:

Nice rulers. I'm from Iowa, too.

We can thank my dear, departed dad for making sure I left Iowa with plenty of yardsticks years ago.  Every once in a while, I come up with a good use for them.

Does anyone still give away yardsticks these days?  They were a staple handout at county fairs in the 70s and earlier.

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18 hours ago, munirocks said:

22 mm Panoptic takes a Dioptrix, according to the table on the Tele Vue website. Discontinued but available used. Stunningly sharp eyepiece.

Thanks, I'd missed that one!  Does anyone know how well the 22mm Pan works with a Dioptrx?

I've now managed to buy 3 eyepieces secondhand - a 20mm Pentax XW, a 22mm Vixen LVW, and a 22mm Nagler.  

There's been no clear night since, but using them indoors I can't see the full field of view with the Nagler + Dioptrx.  

The Dioptrx fits the Pentax XW perfectly.  Whilst it doesn't fit the Vixen LVW I think finding the right size O ring will make it do so.

 

 

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2 hours ago, Second Time Around said:

I can't see the full field of view with the Nagler + Dioptrx. 

Yeah, it's tight on eye relief with eyeglasses.  You've got to push in with glasses to see the field stop.  I imagine the same with a Dioptrx would be true.

The 22mm Panoptic might be easier to use with Dioptrx given similar eye relief but smaller AFOV.

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I've put wanted ads up for a 22mm 70 degree and a 22mm Panoptic.

Can anyone help please?

I've already got a 22mm Nagler, 22mm Vixen LVW and a 20mm Pentax XW to test as soon as my 10 inch mirror comes back from recoating from OOUK.

I'll report back here in due course.

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3 hours ago, Second Time Around said:

I've put wanted ads up for a 22mm 70 degree and a 22mm Panoptic.

Can anyone help please?

I've already got a 22mm Nagler, 22mm Vixen LVW and a 20mm Pentax XW to test as soon as my 10 inch mirror comes back from recoating from OOUK.

I'll report back here in due course.

Avoid the 22mm 70 degree versions with the Celestron Ultima LX or Olivon 70 twist up eye guard.  Even all the way down, each version eats up eye relief and is non-removable for Dioptrx usage.  Stick with the AF70, Omegon Redline SW, or TS-Optics Expanse WA versions with the screw-off eyecup.

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