41mm Panoptic

[Scooot]

I've hankered after a wide field eyepiece for sometime now, maybe a 30mm, but I've see the price of the 41mm has come down quite a bit.

With my scope the exit pupil would be 8.54, I don't know what mine is but I doubt its any more than 6.5, if that. So using this eyepiece, I think I'm correct in saying I'd lose light, but how much?

6.5/8.54 is 0.76 so would it be like looking through a 7.6" scope instead of my 10" or is the maths more complicated than this.

I suspect I would lose contrast as well. It would be good to know to consider whether the wider field was worth the loss in light.

Any words of wisdom will be gratefully received.

[John]

I don't know all the maths either but I stick to an exit pupil of around 6mm max. With larger exit pupils than this I tended to find the background sky gets greyer rather than blacker which didn't help to see the contrast in the sorts of objects you want to view in a low power, wide field eyepiece.

I know folks on here who have moved from eyepieces that give an exit pupil of 7mm to around 5mm and they have noticed DSO's looking more contrasty and brighter so I feel you do loose something with an overlarge exit pupil.

My lowest / widest EP is the Nagler 31mm which gives a 5.85mm exit pupil with my fastest scope. Thats as large as I'll go I think.

[Scooot]

Thanks John, I was looking at the nagler, but haven't summoned up the courage to spend that much yet.

[ollypenrice]

I have direct experience of the exit pupil issue. In our 20 inch F4.1 the 35 Panoptic (which I bought for use in an SCT) gave an exit pupil of over 8mm. When it was killed in action by a half-sticking brass compression ring (stupid things!) I replaced it with a 26 Nagler to have a comparable field of view, more magnifcation and smaller exit pupil. The effect was staggering. The image was so much brighter that it felt like a new telescope.

So I would never again drift into having too large an exit pupil.

Olly

[Scooot]

Thank you Olly, good information.

[NGC 1502]

Olly (post #4) is right on the money here. The effect is very noticeable in any scope I've used, and under good skies and poor.

The only time I'll accept an overlarge exit pupil is just to find an object, with a very low power wide field. I use a WO Swan 33mm for that, fuzzy off axis, but works for that purpose.

Regards, Ed.

[Scooot]

Thanks Ed, I see u have the same scope, what's the longest focul length eyepiece you use with it. I'll probably eventually go for the 26 or 31 nagler.

[Andrew*]

Yes, you will lose light. It's the same effect as using a 7x50 binocular in bright conditions. The eye's pupil diameter in effect stops down the scope. If your eye is indeed 6.5mm, it would stop down the scope as you say, so the contrast decreases. On newtonians you can also sometimes notice a shadow caused by the secondary mirror.

However, don't just assume your eye is 6.5mm. Go into a dark room, let your eye relax for 30 seconds, then take a photo of your eye next to a ruler. Superimpose the ruler scale against your eye and you will no exactly what your maximum pupil is. Mine is over 8mm, which is not unusual.

Also, low power can be a great advantage, so do consider it carefully. I use low power as a finder, then increase power depending on the object. And observing large diffuse objects NEEDs low power, because if you spread it out too much it's difficult to determine the edges. I saw nebulosity in the Pleiades with a 40mm eyepiece in an f/4.5 16" scope. It wasn't visible with higher power - I couldn't make it out!

I know I sound like a stuck record, but it is very worthwhile experimenting with low powers and see how you get on with it - everyone is different in their individual preferences and anatomy.

Andrew

[alan potts]

I use a 35mm Pan in a scope that is giving an exit pupil of 7mm, at this you can start to see the black circle from the secondry mirror, I just get away with it, the 41mm is more or less unuseable in the same scope. I agree with advice given stay to around 6mm.

Alan.

[Scooot]

Thanks Andrew & Alan

i don't think on most nights my pupil would open to the same degree it might in a darkened room because of the moderate light pollution here, its never that dark.

[Andrew*]

If you want to stay on the safe side, I'd get a 30mm Aero. You could always try a 40mm Aero if you get hold of one, and see how you get on.

[Scooot]

If you want to stay on the safe side, I'd get a 30mm Aero. You could always try a 40mm Aero if you get hold of one, and see how you get on.

Thanks again, I ve just found and read John's review on the Aero. Thanks John. As good as it seems, as I'm used to the Delos, I'm becoming more set on the naglers.

[Scooot]

Change of plan.

I've just ordered an Explore Scientific 20mm 100deg from the states for 357usd including shipping. I reckon it will be about £300 with VAT and the post office's service charge. It gives me the same FOV as the 26 mm nagler.

Hope I like it, feeling pretty pleased with myself at the moment.

[Andrew*]

Change of plan.

I've just ordered an Explore Scientific 20mm 100deg from the states for 357usd including shipping. I reckon it will be about £300 with VAT and the post office's service charge. It gives me the same FOV as the 26 mm nagler.

And the 30mm Aero! Good buy. With any luck it will slip through the customs net, but you can never count on that...

[NGC 1502]

Thanks Ed, I see u have the same scope, what's the longest focul length eyepiece you use with it. I'll probably eventually go for the 26 or 31 nagler.

Hi Richard. I use a 33mm William Optics Swan as a 'finder', it gives 36x and a 2 degree field. The view is very 'washed out', but it works to find objects. I also have a 27mm Panoptic, 44x and 1.5 degree field. The Pans are very well corrected, but the 27 does show up the coma inherent in the F 4.8 mirror. My favourite low power EP is a 22mm Vixen LVW, it gives 54x and 1.2 degrees, and is sharp to the edge, and a nice dark field. I always wondered why the LVWs have 8 elements, perhaps that's why they are sharp to the edge in fast scopes ?

1.2 degrees is wide enough to show M81/82 in the same field, the double cluster, and is enough power for wide double stars. The 20mm eyerelief is great too.

My eyes have minor astigmatism, that makes large exit pupils give a fuzzy view. I know I could use specs, but I'm trying to put that day off. I'm 65, so am fortunate to have good long range vision without specs during the day, when my pupils are probably at 2 or 3mm. At night, my pupils are around 5-6mm, that shows bright stars as fuzzy blobs, when the exit pupil from the scope is using all of my dilated eyes. At somewhere around 4 to 4.5mm exit pupil, the view is considerably sharper.

Of course, eye defects are individual things, so everyone needs to factor in how good there own eyes are.

I see you are also in Essex, you would be welcome at Castle Point AS. We are on our summer break at the moment, back on Sept 4th.

Hope that helps, Ed.

Edit - wow, just seen you have ordered an ES 20mm 100 degree EP, should give a fantastic view. I'm not envious, I'm VERY envious

[Scooot]

Hi Richard. I use a 33mm William Optics Swan as a 'finder', it gives 36x and a 2 degree field. The view is very 'washed out', but it works to find objects. I also have a 27mm Panoptic, 44x and 1.5 degree field. The Pans are very well corrected, but the 27 does show up the coma inherent in the F 4.8 mirror. My favourite low power EP is a 22mm Vixen LVW, it gives 54x and 1.2 degrees, and is sharp to the edge, and a nice dark field. I always wondered why the LVWs have 8 elements, perhaps that's why they are sharp to the edge in fast scopes ?

1.2 degrees is wide enough to show M81/82 in the same field, the double cluster, and is enough power for wide double stars. The 20mm eyerelief is great too.

My eyes have minor astigmatism, that makes large exit pupils give a fuzzy view. I know I could use specs, but I'm trying to put that day off. I'm 65, so am fortunate to have good long range vision without specs during the day, when my pupils are probably at 2 or 3mm. At night, my pupils are around 5-6mm, that shows bright stars as fuzzy blobs, when the exit pupil from the scope is using all of my dilated eyes. At somewhere around 4 to 4.5mm exit pupil, the view is considerably sharper.

Of course, eye defects are individual things, so everyone needs to factor in how good there own eyes are.

I see you are also in Essex, you would be welcome at Castle Point AS. We are on our summer break at the moment, back on Sept 4th.

Hope that helps, Ed.

Edit - wow, just seen you have ordered an ES 20mm 100 degree EP, should give a fantastic view. I'm not envious, I'm VERY envious

Yeah can't wait to try it. I think I will come over to castle point later this year some time. Another member from Billericay has also suggested it.

[ollypenrice]

Good luck with the customs. The bar stools have stung me big time (really excessive) with some kit imported via a friend ths month. Hey ho, you win, you lose. If you were self employed you could always get them back. I wouldn't dream of it, of course.

Olly

[alan potts]

Well that is a bit different to where we started, 41mm Pan to 20mm ES 100 degree. Congratulations I hope you enjoy it.

Alan

[Scooot]

Well that is a bit different to where we started, 41mm Pan to 20mm ES 100 degree. Congratulations I hope you enjoy it.

Alan

thanks Alan, same price though. Not quite the same FOV, but not far off the 35mm panoptic.

[Naemeth]

I'm a bit late to the party unfortunately. I personally don't stick to a 6mm exit pupil maximum because even stargazing in heavily light polluted skies I find I can easily use my TeleVue 32mm Plossl in my F/5 (6.4mm exit pupil) as long as I've had a little bit of time for my eyes to adapt - and the skies are inky black - lovely .

Age is a factor though, I am roughly half the age of the average member here (a 3rd of some, that makes me feel young!).

[Scooot]

Age is a factor though, I am roughly half the age of the average member here (a 3rd of some, that makes me feel young!).

good for you, I wish I'd got into it at your age, I'm a bit of a latecomer, not even 2 years yet. I've seen a couple of posts from some real youngsters. That's very inspiring.

[John]

Change of plan.

I've just ordered an Explore Scientific 20mm 100deg from the states for 357usd including shipping. I reckon it will be about £300 with VAT and the post office's service charge. It gives me the same FOV as the 26 mm nagler.

Hope I like it, feeling pretty pleased with myself at the moment.

Thats an interesting move

I bought one used from a member here and I've liked it a lot. If you don't already own an eyepiece of that weight be prepared to consider your scopes balance

[Scooot]

Thats an interesting move

I bought one used from a member here and I've liked it a lot. If you don't already own an eyepiece of that weight be prepared to consider your scopes balance

yes saw its a bit of a beast. I've got plenty of room to slide the OTA down a bit if I need to, hopefully I can arrive at a decent compromise for all the eyepieces.

[ollypenrice]

I'm a bit late to the party unfortunately. I personally don't stick to a 6mm exit pupil maximum because even stargazing in heavily light polluted skies I find I can easily use my TeleVue 32mm Plossl in my F/5 (6.4mm exit pupil) as long as I've had a little bit of time for my eyes to adapt - and the skies are inky black - lovely .

Age is a factor though, I am roughly half the age of the average member here (a 3rd of some, that makes me feel young!).

Show off. But I remember the dinosaurs. My god, they were great. Never been anything like it since. Lions? Pah!

Olly

[Scooot]

One thing I have been wondering, lets say I had gone for a 26 or 31mm nagler instead. Presumably the lower power would let in more light than than the 20mm ES, but the latter would have better contrast. I haven't been able to see all of the western veil from here yet so I'm wondering whether the lower power naglers would have given me a better chance.