Maxvision 40mm or Aero 40mm?

[Chris Hopson]

Hi Alan,

Unfortunately I can't fit 2" eps to 90 or the 125 as they are both de-mounted ETX's, it would be great for quick wider FOV sessions. Although I believe there is an adaptor or something that a 2" diagonal goes in?

Why does it vignette though, just because it's a 2" ep?

Regards

Chris

[michael.h.f.wilkinson]

For these little scopes, get the MV 24mm 68deg: superb EP that gives the maximum FOV of a 1.25 barrel. in the Maks you would not see the difference with the legendary Panoptic 24mm

[alan potts]

Chris,

I can only imagine that the tube through the scope is not large enough to allow enough light through to use a 40mm, the 35mm Panoptic works fine which is good enough. In truth the scope is not intended to be a wide field scope. Interestingly I get the same slight vignette on the SC 12inch using a diagonal with the Panoptic 41mm but didn't with the Meade 40mm. I just live with it now.

alan

[YKSE]

Alan is right about the vignetting caused by smaller rear port size of small Mak/SCTs, here's Celestron page about rear port sizes and vignetting.

There's no visible vigne tting in C8 with 40mm AERO, dispite the 46mm field stop of Aero is larger than 37mm rear port size, since the rear port is some distance away from the focus plan, vignetting does exist, but our eyes are very tolerant with gradual vignetting.

[John]

I guess it's all to do with the diameter of the rear light baffle and port on SCT's and Mak-Cassegrain scopes ?. I seem to recall that even my C8 only had a port / baffle thas was 37mm in diameter and a 40mm 70 degree eyepiece will have a field stop of ~45mm so thats the dilemma - does the internal design of the SCT / Mak-cassegrain prevent full illumination of the field of view of such an eyepiece ?

If vignetting does occur (which I feel is likely) I suspect that it's not going to appear as a sharp reduction in the field of view. What I've not be able to make my mind up about though is whether the vignetting will show itself as a gradual reduction in light towards the edges of the field of view or a general reduction spread across the whole field. The latter seems unlikely at first glance but optical systems work in odd ways sometimes 

Perhaps an optical expert can shed some more light on this ?

Edit: Ah, I see such a person has contributed just above my post !

[Chris Hopson]

For these little scopes, get the MV 24mm 68deg: superb EP that gives the maximum FOV of a 1.25 barrel. in the Maks you would not see the difference with the legendary Panoptic 24mm

It's a good idea Michael, but the MV 24 82deg would be a nice step up from by 25mm BST

[Chris Hopson]

Chris,

I can only imagine that the tube through the scope is not large enough to allow enough light through to use a 40mm, the 35mm Panoptic works fine which is good enough. In truth the scope is not intended to be a wide field scope. Interestingly I get the same slight vignette on the SC 12inch using a diagonal with the Panoptic 41mm but didn't with the Meade 40mm. I just live with it now.

alan

Thank you Alan, I guess that shows just how good the Meade is then, even though it's competing against a TV.

Regards

Chris

[Chris Hopson]

Alan is right about the vignetting caused by smaller rear port size of small Mak/SCTs, here's Celestron page about rear port sizes and vignetting.

There's no visible vigne tting in C8 with 40mm AERO, dispite the 46mm field stop of Aero is larger than 37mm rear port size, since the rear port is some distance away from the focus plan, vignetting does exist, but our eyes are very tolerant with gradual vignetting.

Thank you YKSE for the link.

Regards

Chris

[michael.h.f.wilkinson]

It's a good idea Michael, but the MV 24 82deg would be a nice step up from by 25mm BST

But the 24mm 82° version is 2" not 1.25", so will show vignetting in the small Maks

[Chris Hopson]

But the 24mm 82° version is 2" not 1.25", so will show vignetting in the small Maks

Yes of course, and my Maks are only 1.25 fitting. I can't actually find a MV 24 68deg for sale, everywhere is sold out.

Regards

Chris

[Chris]

Yes of course, and my Maks are only 1.25 fitting. I can't actually find a MV 24 68deg for sale, everywhere is sold out.

Regards

Chris

You could get the 24mm ES68 which is practically the same eyepiece just with waterproofing and a nicer fit and finish. These used to cost 129 pounds but they have recently been reduced to just 69 pounds:

http://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-68-degree-series-eyepieces.html

[Chris Hopson]

You could get the 24mm ES68 which is practically the same eyepiece just with waterproofing and a nicer fit and finish. These used to cost 129 pounds but they have recently been reduced to just 69 pounds:

http://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-68-degree-series-eyepieces.html

Chris, that's a good idea. The only thing that might put me off mate is if it is like when I tried a friends ES82deg and found my eyelashes all over the lens. I find it really uncomfortable and annoying because of the grease it leaves behind.

Regards,

Chris

[Chris Hopson]

Chris, that's a good idea. The only thing that might put me off mate is if it is like when I tried a friends ES82deg and found my eyelashes all over the lens. I find it really uncomfortable and annoying because of the grease it leaves behind.

Regards,

Chris

Sorry scrub that, I've just looked up the eye relief.

[Chris]

Sorry scrub that, I've just looked up the eye relief.

Yeah I have that exact same problem with the ES82's, just can't use them with the eyecup rolled down and with it up you can only see about 55-60 degrees. I much prefer the eye relief on the 68 degree versions.

Now if you want an 82 degree eyepiece with good eye relief try the Celestron Luminos/Axiom. I regret selling mine in all honestly. 

[michael.h.f.wilkinson]

Yeah I have that exact same problem with the ES82's, just can't use them with the eyecup rolled down and with it up you can only see about 55-60 degrees. I much prefer the eye relief on the 68 degree versions.

Now if you want an 82 degree eyepiece with good eye relief try the Celestron Luminos/Axiom. I regret selling mine in all honestly. 

Or the Nagler Type 4s