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pjmaciw

Got one Nagler ..... what next?

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I decided to get a few Televue eyepieces to work with my Quattro 10" F4 reflector.

I managed to get a Nagler 13mm and very good it is too. I already have a Televue 8mm plossl and Televue 2x barlow,

The question is what to get next? I was thinking of a 19 or 24mm Panoptic or possibly going the other way with a 6mm Delos.

I only want (can afford) one ep for now, so what would be the best choice. All suggestions welcome but must be Televue.

Thanks, Pete.

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To get you some wider field views what about the 31mm Nagler - the Holy Hand Grenade ? A bit of a difference between the two but a great EP. Wish I had one. Cannot prise myself away from my Panoptic 35mm though...

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I started to collect TeleVue EPs about 3+ years ago after I obtained a 13mm Ethos. I am afraid you get hooked. I also have a 10" Newt as a Dob and mind is f4.7. If I was to choose a great EP for your scope it would be a 2" wide field. Whether is a Panoptic or a Nagler depends on finance. I have both a 20mm and 26mm Nagler and they are brilliant. If I had to choose I would keep the 26mm Nagler. Put on a UHC filter and the views of the Veil etc are fantastic.

Pete good luck with your decision.

Mark

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I am with Mark. I think the 26mm Nagler is the best eyepiece I have ever used. That said, given your other eyepieces, the 24mm Panoptic is in the same weight bracket and might be a better option as you won't have to consider balancing issues every time you swap - it's no slouch.

I'd actually also recommend you buy a 2.5 x powermate and sell the 8mm plossl / barlow (did I just say that??). this would be very good for imaging, work very well with the panoptic (effectively a 10mm eyepiece 100x) and the nagler (effectively a 5mm eyepiece 200x) with a much more comfortable eye relief than the 8mm plossl on its own or the 24mm/13mm barlowed.

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The 24mm Panoptic is a great eyepiece as is the 19mm but I think the 13mm Nagler will show as much, if not a bit more, sky as the 19mm Pan so it would have to be the 24mm to get a wider view. Funnily enough those two were my first wide angle Tele Vues as well :smiley:

I got the taste for the ultra wide angles of view though so, even though it's an excellent eyepiece, I found the 68 degree view of the Panoptic a bit "claustrophobic" compared to the Nagler. My Panoptic was replaced by a 22mm T4 Nagler, then I got some more T6 Naglers for higher powers ............ and then I tried an Ethos :rolleyes2:

I've contributed my bit to Al Nagler's pension fund over the years !

With an F/4 Tele Vues "show no field unless it's sharp" philosophy really pays off, more than any other brand I think. With that focal ratio though the 24mm Pan would be the longest focal length that you would want really - even that gives you a 6mm exit pupil. Another argument for ultra-wides I think !

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We don't own one and it's not the cheapest option, but I was very impressed with some views through the 31mm Type 5 Nagler at SGL last year. We have a 35 Panoptic as our wide eyepiece, which is very nice indeed, but the 31 Nagler had something very special about it!

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I have a T2 20mm nagler that were first produced in 1986. I thought this was the 'Holy Hand Grenade' as it weighs over 2lb. Please correct me if I am wrong

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The Nagler 31mm Type 5 weighs 2.2 lbs. The Type 5 20mm (which replaced the T2 that you have) is a lot smaller than it's predecessor and weighs around half as much.

A 31mm eyepiece in an F/4 scope gives an exit pupil of 7.75mm which is rather too large in my opinion. You may have issues with the secondary shadow being visible with such a scope / eyepiece combination too.

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The 31mm Nagler in this case would result in a 7.75mm exit pupil, too large imho unless the op has the eyes of an owl!

The 24mm Panoptic is a lovely eyepiece & would be as long as I would go with an f4 scope, or even better the 22mm Nagler. If money wasn't an issue, the 21mm Ethos will show the same fov as a 26mm Nagler while retaining a 5.25mm exit pupil!

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Interesting stuff. Found this here:

"...Or to state it a different way: If you have a 5-mm eye pupil, you cannot use an eyepiece longer than 20 mm focal length on any f/4 telescope, or 30 mm on any f/6 scope, if you want full use of the aperture. This is true regardless of the telescope's size or anything else. The rule here is e = fp, where e is the eyepiece focal length, p is pupil size, and f is the telescope's f/number (focal ratio)."

Article here:

http://www.skyandtel...cs/3304201.html

Edited by Luke

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I guess the other question that the Pete will need to think about is using the coma corrector for visual. At F/4 with eyepieces like the Naglers and Panoptics quite a bit of coma is going to show I'd have thought ?

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I have the 6mm delos and for what I have seen so far it is a great eyepiece.

I though would go the other end and get either a 24mm or 35mm Panoptic. There is nothing to better them and they would be better value secondhand, more available too I would say than the 31mm Nagler which even S/H will cost a great deal.

Alan.

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Whilst I really like the 35mm Panoptic, I had noticed I was losing some of the view with our f5 dob. Now this has been replaced with a larger dob, at f4.5, I have noticed the 35mm Panoptic view seems to have got worse for me. This is obviously down to the exit pupil.

Televue have a useful Eyepiece Calulator on their website which will give you the exit pupil and Field of View info amongst other stuff.

http://www.televue.com/engine/TV3_page.asp?id=89

With your f4 scope the 35mm panoptic would provide an even worse exit pupil, than the 31mm Nagler, at around 8.8mm.

I am experiencing a slight problem with the 24mm panoptic at f4.5 so presumably I need an eyepiece with a lower exit pupil. My conclusion is I need a 21mm Ethos! Although looking at the cost :eek: maybe I'll have to suffer!

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...I am experiencing a slight problem with the 24mm panoptic at f4.5 so presumably I need an eyepiece with a lower exit pupil. My conclusion is I need a 21mm Ethos! Although looking at the cost :eek: maybe I'll have to suffer!.....

You are experiencing the situation that the Naglers and now the Ethos eyepieces are specifically designed to address - how do you retain an acceptable exit pupil size and a very wide angle, low power, sharp, field of view, in today's fast scopes ?

Unfortunately the optical solutions to this are expensive to design and manufacture. There are other options that get close though from brands such as Explore Scientific and others, although they are not exactly cheap either !

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I am experiencing a slight problem with the 24mm panoptic at f4.5 so presumably I need an eyepiece with a lower exit pupil. My conclusion is I need a 21mm Ethos! Although looking at the cost :eek: maybe I'll have to suffer!

what you need is a used Parcorr. this would increase your focal length by 15% and increase your focal ratio to f5.175 and therefore your exit pupil would reduce to 4.64mm :grin:

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Sarah and John,

I have never seen this in a scope, I have used the 41mm in the F7 115mm and I have never seen it, I will try it in the F5.3 MN tonight as the sky is as clear as I could ever hope it to be. I have used the 35mm in this scope many times and never seen a problem.

I was thinking of a pair of opticron bino ar 11X80 so in them the exit pupil is already too big for my 56 year old eyes, I was just going for the low mag so I could hand hold, for a while anyway.

Alan.

Edited by alan potts

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You are experiencing the situation that the Naglers and now the Ethos eyepieces are specifically designed to address - how do you retain an acceptable exit pupil size and a very wide angle, low power, sharp, field of view, in today's fast scopes ?

Yes, I am beginning to see that now John! Although I experience kidney beaning with the 13mm T6 Nagler, so may be leaning towards to Ethos route! This has got us thinking about our current eyepieces and we may well look at the Ethos now!

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Sarah and John,

I have never seen this in a scope, I have used the 41mm in the F7 115mm and I have never seen it, I will try it in the F5.3 MN tonight as the sky is as clear as I could ever hope it to be. I have used the 35mm in this scope many times and never seen a problem.

I was thinking of a pair of opticron bino ar 11X80 so in them the exit pupil is already too big for my 56 year old eyes, I was just going for the low mag so I could hand hold, for a while anyway.

Alan.

Alan, it will be interesting to see how the 41mm fares for you at f5.3. The exit pupil is around 7.7mm which may be a bit too much. The 35mm has an exit pupil of around 6.6mm at f5.3.

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Sarah,

Looks like it's clear for me to-night, I will give it a go and if that don't show up the mirror then I can go to the next step, if I can find it, the 55mm Plossl, that should be th starw to break the camels back. It will be the fist time it's seen light in a long time. I used to use with the LX 200 before I went mental and stated TV collecting. We should invent a name for it, if some haven't already.

Alan.

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Sarah

Checked this seeing of the mirror out on the Mac/Newt 190 which is F5.3 with a 41mm Panoptic, and I cant say I could see any difference apart from a very wide field, sharp as a razor from edge to edge. I don't know if there was just a hint of it being a little more difficult to use about it. I would say though that at 7.7mm E/P it is only just OTT.

However when I tried the 55mm it was very obivous a big black area in the middle when you just moved you eye away a little and very difficult to get any view at all without moving you head about . What a shock it is to use this EP after all the wide eyepieces I have, the 50 degree field looks tiny after the 68 and 82 I had been using. It is a good job I had not been using an Ethos I would have thought I was looking down a straw.

I also understand why I never had a problem with 41mm in the 115mm, refractors don't have mirrors do they. As well as the E/P is not over large. I do feel a bit of a twit.

Anyway hope this is of some use.

Alan

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Sarah

Checked this seeing of the mirror out on the Mac/Newt 190 which is F5.3 with a 41mm Panoptic, and I cant say I could see any difference apart from a very wide field, sharp as a razor from edge to edge. I don't know if there was just a hint of it being a little more difficult to use about it. I would say though that at 7.7mm E/P it is only just OTT.

However when I tried the 55mm it was very obivous a big black area in the middle when you just moved you eye away a little and very difficult to get any view at all without moving you head about . What a shock it is to use this EP after all the wide eyepieces I have, the 50 degree field looks tiny after the 68 and 82 I had been using. It is a good job I had not been using an Ethos I would have thought I was looking down a straw.

I also understand why I never had a problem with 41mm in the 115mm, refractors don't have mirrors do they. As well as the E/P is not over large. I do feel a bit of a twit.

Anyway hope this is of some use.

Alan

Without an obstruction, you shouldn't see any black in the middle of the eyepiece, but you will possibly be straining your eyes at worst, and at best merely wasting light. It's best to stick with an exit pupil of 7mm maximum, but if you have velvet black skies, you may be able to push to the limit more often.

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Sarah

Checked this seeing of the mirror out on the Mac/Newt 190 which is F5.3 with a 41mm Panoptic, and I cant say I could see any difference apart from a very wide field, sharp as a razor from edge to edge. I don't know if there was just a hint of it being a little more difficult to use about it. I would say though that at 7.7mm E/P it is only just OTT.

However when I tried the 55mm it was very obivous a big black area in the middle when you just moved you eye away a little and very difficult to get any view at all without moving you head about . What a shock it is to use this EP after all the wide eyepieces I have, the 50 degree field looks tiny after the 68 and 82 I had been using. It is a good job I had not been using an Ethos I would have thought I was looking down a straw.

I also understand why I never had a problem with 41mm in the 115mm, refractors don't have mirrors do they. As well as the E/P is not over large. I do feel a bit of a twit.

Anyway hope this is of some use.

Alan

That's interesting Alan. You've got better weather than we have! I find I get a blackening around the edges, like my view is narrower than it should be. And with the 16" dob at f4.4 (I incorrectly said it was f4.5 in my earlier post) the view also seems dimmer with the 35mm than it is in the 12" dob.

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And with the 16" dob at f4.4 (I incorrectly said it was f4.5 in my earlier post) the view also seems dimmer with the 35mm than it is in the 12" dob....

Thats the sort of effect an over large exit pupil gives you. The thing is you only really notice it when you compare two setups almost side by side, where one has a manageable exit pupil and one an oversize one.

I noticed this when comparing 10x80 with 20x80 binoculars. The views of the same objects were dimmer with the 10x80's because my eye could not handle the whole of the 8mm exit pupil - I was in effect only getting the benefit of something like a 60mm aperture, maybe less.

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