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Commanderfish

41mm Panoptic and big exit pupils

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Hi all,

I am thinking about getting a panoptic 41mm for my VX 16 F4 dob (which has an FL of 1600/1840 with paracorr).  I worked out though, that the Exit Pupil would be 10.25mm, or 9mm with the paracorr.  That's pretty huge, and definitely bigger than anyone's maximum pupil dilation.  It would give me the widest true field possible in my scope though (AFAIK).  Are there any diasdvantages to having an Exit Pupil this big?  Does it rob the view in any way?

If anyone has experience of using a similar combo, that would be great info.  Cheers!

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Pretty sure Derek has a 41mm Pan which he could try in his f4 VX12 for a similar exit pupil.

The two normal issues which occur are the potential of seeing the shadow of the secondary, plus the sky background being too bright. Personally I would not chase wide fields with this scope, at least not beyond sensible exit pupils. Under anything but a very dark sky the sky background will be very washed out and the view will lack contrast.

The benefits of aperture are getting more image scale at the same brightness over smaller scopes. You will see detail not visible in smaller scopes because you are able to enlarge it enough to be detected whilst maintaining the brightness levels.

You have fracs for widefield, so use the Dob to its strengths.

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I tend to use the Pan 41 in my fracs for exactly the reasons Stu suggests. Pushing it too far can result in a very washed-out view, which is fine if you are using it as a finder for bright objects, but not for faint stuff.

The 21mm Ethos tends to be the lowest power EP I use in my dobs.

Where I think the Pan 41mm comes to life is for white light solar viewing through my ED120 or larger as it shows fabulous detail and granulation.

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28 minutes ago, Stu said:

 

The benefits of aperture are getting more image scale at the same brightness over smaller scopes.

You have fracs for widefield, so use the Dob to its strengths.

^^^ This :) 

 

 

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Yeah I had a 40mm widefield which is the precursor to the Pan. As suggested it's far to big an exit pupil and although the view was wide and sharp where you have all but very dark skies it's too bright a sky. I found it a faff in my fracs too given the weight.

Much better would be a 26mm Nagler or even a 22. I like my 24 Pan.

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Thanks guys. This (sky background Issie) would explain why I like the Ethos 21 a little more than the ES 30mm 82 degree, although I must say both gave some great views tonight. 

I think there is a use for the Pan 41 in the big dob with a big exit pupil though, namely with narrow band filters like the Oiii.  However the ES30 already does this fine.

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6 hours ago, Commanderfish said:

Thanks guys. This (sky background Issie) would explain why I like the Ethos 21 a little more than the ES 30mm 82 degree, although I must say both gave some great views tonight. 

I think there is a use for the Pan 41 in the big dob with a big exit pupil though, namely with narrow band filters like the Oiii.  However the ES30 already does this fine.

I have a TMB Paragon which is 2", 40mm and 69 degree afov. You are welcome to give it a go to see how well the large exit pupil works with narrowband filters.

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I use the 41mm Panoptic with a 70mm f/6 APO as a finder. The true field it provides is ideal and the view itself very enjoyable. So that part makes perfect sense to me.  :happy11:

On the other hand, I don't have a dob so best to go with those who know.  :icon_biggrin:

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