Nagler 31mm a widefield step too far?

[moriniboy]

Everyone talks about a Nagler 31mm as if its one of the ultimate widefield ep's to own but they still come up for sale regularly.

I have a Nagler 17mm type 4 already and wonder if it would be better to look at a Nagler 26mm instead of the 31mm because of the darker background due to the magnification but I would then be sacrificing the wider view somewhat.

I have various scopes ranging from a 200PDS, Equinox 120, Lyra Optics F11 and an Ikharus 100ED so quite a varied bag of focal lengths to deal with.

Any comments?

[Moonshane]

I think there are a number of issues at work. this is a fabulous eyepiece and has quite a different feel to the view than even the 26mm Nagler. I have the latter but have looked through the former. you rarely see the 26mm for sale compared with the 31mm.

• value / price - if you are stuck for cash and need to raise money quickly for whatever reason, the 31mm can be sold at the drop of a hat at the right price. many people see the 'finder' / widest field eyepiece as a luxury and it can be replaced with a lesser model (e.g. a SW aero for a third of the price).
• balance - the 31mm is substantially heavier than the 26mm and balance can be overly affected in some designs
• exit pupil - this is one of the main reasons I bought the 26mm not the 31mm. My two bigger scopes are f4 and my site has a lot of light pollution.

I am sure that other people will have different reasons but these are mine, mainly the last one.  in my biggest scope, the 26mm Nagler provides an exit pupil of 5.65mm (I use a paracorr), a true field of approx 1.15 degrees and magnification of 71x. The 31mm Nagler would give 6.74mm, 1.39 degrees and 59x. Given the relatively small differences, the 26mm Nagler is the clear winner for my circumstances. 

[michael.h.f.wilkinson]

I have looked through all Naglers mentioned here, I love the 17T4, have the 22T4 as well (both great) and the 31T5 "Panzerfaust". I had a look through the 26T5 with Olly Penrice's 20" F/4.1 Dob (Sir Isaac), and it is awesome in such a fast scope. I did not have the 31T5 yet, but would think the 7.56mm exit pupil would be a bit much. I use the 31T5 in both my 80mm F/6 and 8" F/10 scopes, so exit pupils are quite OK. Even in an F/5 scope it should be OK if LP is not severe, as I find that exit pupils of just over 6mm are quite OK/ In the 200 PDS I should think the 31T5 should work. In all your other scopes the 31T5 should be outstanding.

If ever I get an F/4.5 or faster Dob I think I would get that 26T5 as well.

Maybe you should try and use a 31T5 in your scope at a star party to see if you like it, before parting with that kind of dosh.

[Stu]

What Shane says makes total sense. I exclusively use mine in a 106mm apo where it gives a 3.68 degree field and 4.8mm exit pupil. It is ideal from dark sites on objects like the Veil. I rarely use it from home because it tends to look washed out in the LP.

Stu

[estwing]

I step in and out of the need to get the 31mm pool...as for now in my scope it's telrad,Finder, 21ethos and it just work so well

[Moonshane]

if I had a large SCT or a medium speed frac, I think I'd be looking to get the 31mm in the future. I'm not though, so I'm not.

[alan potts]

I have both and I don't disagree with a word Moonshane stated.

Before I had the 31mm I used a Meade 30mm UWA and the money savinging is something to consider as I couldn't see much between these two in my scopes, however if one gets to the dizzy hieghts of F4 it may well be a different kettle of fish.

Alan.

[Pig]

The T31 works a treat for me in my 9.25 SCT  probably the best wide field views I have observed.

I have no issues with a washed out background or exit pupil  mind you it is a 3.1 exit pupil in my scope.

My previous eyepiece was a 34mm Maxi and found the FOV etc not quite so good, but there is a big difference in cost.

[swamp thing]

I have the 31mm T5 too. For me it's my wide field eyepiece in my larger scope. I don't mind the larger exit pupil as I use my scope at dark skies exclusively, and for me most objects requiring the giant field (relatively speaking of coarse in a 20" scope) are more about fitting them in than anything else.

I did think of changing to the 26mm but the loss of field for me is more critical at this focal length than the contrast improvement. For better contrast I opt for a 20mm T5, and this really delivers it. I may well look at getting an infill eyepiece between the two though and the 26mm T5 would be my first choice.

As Shane states the weight issues it causes mean I rarely use it in my small scope, and one can count perhaps half a dozen objects that actually need the FOV it provides with a 10" f4.5 scope.

[Uplooker]

Hi Nigel,

I have the 26mm Nagler. If you want I can let you borrow it for a couple of days to see what you think of it.

Ian

Sent from ma fone using Tapatalk 2

[John]

I have the 21mm Ethos and the 31mm Nagler and I'm keeping both 

I did wonder whether a 20 / 21 mm 100 degree eyepiece would render the big Nagler redundant but when I want the max amount of sky the "Terminager" is still the king in my eyepiece box even though the 21mm Ethos will probably see more use.

IMHO the 31mm T5 Nagler is one of Tele Vue's classic eyepieces and I feel lucky to own one  

In my fastest scope the exit pupil with the N31 is 5.8mm which as large as I want to go but not too large I feel.

[Naemeth]

I'd say that you would be fine with the 31T5, as long as you don't have big LP problems . I find, due to no real glare (but very bad sky glow) that I can use about 7mm exit pupil at home, but part of that is due to my age . I think it would be better to wait and see which comes up first 2nd hand, if you get the 31T5 and find it's not for you, you can always sell it for the same price, and it will probably sell within a few hours too .

[moriniboy]

Thanks for all the advice, just had a look at the exit pupils as follows:

Scope - 200pds / Equinox 120 / Lyra F11  / Ikharus 102

31mm - 6.2mm   /  4.13mm       / 2.87mm    / 4.43mm

26mm - 5.2mm   / 3.47mm        / 2.41mm    / 3.71mm

With this in mind I'm being steered toward the 26mm and if I can borrow Ian's I think this would confirm the above findings 

[Moonshane]

to be honest, with that mix, I think I'd go for the 31mm unless looking to buy a bigger faster newt in the future.

[estwing]

Arrrrghhh back in the pool!!!

[moriniboy]

Just got rid of my 300px flextube as well 

[Damo636]

I think I'd also go with the 31 Nagler with your current line up!

[Moonshane]

I have said this before and I'll say it again, buying a different scope with a shorter focal length to get more field out of your current eyepieces is often cheaper than a new wide field eyepiece. I recently bought a 114mm f500mm newt to give me a nce wide field view at lower power to replicate binoculars on camping trips but with a bit more oooomph. with this and my 25mm TV plossl (total cost £75) I get a nice wide 2 degree field which is much more than I can get in my 16" or 12" dobs even with the 26mm Nagler.

[omahaastro]

Speaking of which... the view of the Veil through a cheap 120mm f/5 equipped with the 31T5 (4 degree FOV!) and an OIII filter is stunning... you can enjoy the entire expanse!