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25585

Big eyepiece, big eye relief, both 2 inch.

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55mm TV plossl v 41mm Panoptic. Which would you choose (or use) to use for finder/zoning in/large FOV?

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  • Field

The true field of view is about the same for both eyepieces, the apparent field of view is more generous in the 41mm. 

  • Exit pupil

You don't want an exit pupil that is too large. When it gets bigger than your own pupil you'll lose light gathered by the telescope. Also, bigger exit pupils tend too show light pollution better. For astronomy, exit pupils up to 5mm are preferred. 

exit pupil = eyepiece focal length / telescope focal ratio

or, this is the same,

exit pupil = telescope aperture / magnification.

Based on a 5mm exit pupil, a 55mm eyepiece gives would be suitable for telescopes slower than f/11, and a 41mm eyepiece for telescopes slower than f/8.2. Few telescopes are slower than f/11, many more are slower than f/8.2.

Particularly if your telescope has a central obstruction, you don't want an exit pupil that exceeds the size of your own. With bigger exit pupils, the shadow of the obstruction will eventually become visible. 

  • Eye relief 

The eye relief of a 55mm Plössl is ridiculously big. Some will find it difficult to keep their head centered on it at the proper distance.

 

Probably, the 41 mm eyepiece better for most telescopes.

 

I used a 55mm TV Plössl on an f/5 refractor. It showed 5.5° of the sky at a magnification of 9.1x. The exit pupil was 11.1mm (no central obstruction to cast any shadow). I saw a parallax effect on nearby chimneys when I moved my own pupil within the exit pupil. This is the only TV eyepiece I ever sold. It went to a video astronomer who used is afocally.

I replaced it with a 9x50 RACI. Less heavy and always on the telescope.

 

 

 

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Thanks. I also have a Genesis. Maybe we are the only 2 remainng owners!  I want an ep to use rather than a piggyback scope or od. The 41mm Panopotic seems a better choice for my Genesis, which will be useful on my other scopes as well.

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I love my 40mm Meade SWA 5000 which has a sharp field stop.  The 41mm Panoptic reportedly does not, though I have yet to look through one.  You could look into the 40mm Maxvision version to save a bundle of cash and get pretty much the same level of correction.  My Meade appears to be pinpoint sharp edge to edge at f/6.  It can be decloaked to save nearly a pound in weight.

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Right now my longesteyepiece is a Maxvision 68° of 34mm. Works really well at f/5. Magnification is 14.7x and the tfov is 4.6° in the Genesis, nine Moons wide. For even wider views I use binoculars.

ES 68°, Panoptic and Maxvision 68° all perform at about the same level. The Meade 5000 SWAs are identical to Maxvision 68°. I almost bought a 40mm Maxvision, but it is about the size of a grapefruit and awfully heavy. I saw it again a month ago or so at Robtics (click to visit). They might still have them. Price is  currently €170. They were cheaper a year or two ago, but they're getting rarer now and more expensive.  

 

Edited by Ruud

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I have had both and now only have the 41mm but take note of Louis D, he's correct edge of the field it not as good as the Meade but it is sharp with regards stars. Unless you are a TV nut like me go for the Meade 40mm or the ExSc less money too. The 55mm is a fine eyepiece though.

Edit by me, meade 400mm, now that would be some eyepiece, mistake corrected.

Alan 

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Thanks all for your advice. In the end I bought a 35mm Panoptic, in a private sale. 

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8 hours ago, 25585 said:

Thanks all for your advice. In the end I bought a 35mm Panoptic, in a private sale. 

Let us know if you detect any field curvature with it.  I've read some CN reports that those of us with little focus accommodation will notice a bit of field curvature in it.

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In the Genesis I used to own, a 31mm Nagler was fabulous, particularly for filtered views under a decently dark sky. 6.2mm exit pupil, with a very flat 4.8 degree field of view. With an OIII filter on the Veil and NAN it was wonderful.

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The 55mm Plossl makes some sense for very slow scopes such as long focal ratio achros or maks where you want the best exit pupil understanding that the field of view won't be any better. I used one for a while with an f20 Mak, still only a 2.75mm exit pupil :) 

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6 hours ago, Stu said:

The 55mm Plossl makes some sense for very slow scopes such as long focal ratio achros or maks where you want the best exit pupil understanding that the field of view won't be any better. I used one for a while with an f20 Mak, still only a 2.75mm exit pupil :) 

its OK for a finder optic in the f5 Genesis. 9x mag and exit pupil + big eye relief means I don't need anything else though use 8x56 binoculars for a wider view familiarisation first.

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12 hours ago, Louis D said:

Let us know if you detect any field curvature with it.  I've read some CN reports that those of us with little focus accommodation will notice a bit of field curvature in it.

Will do. also try with Paracorr to see if any difference on fc.

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