Low Power Conundrum?

[Damo636]

Thanks Alan. According to the site in Spacebeagle's link the maximum the eye will open on average for a 40 year old is 6.5mm. I wonder how this would translate at the eyepiece with a 7mm exit pupil

[ollypenrice]

Thanks Alan. According to the site in Spacebeagle's link the maximum the eye will open on average for a 40 year old is 6.5mm. I wonder how this would translate at the eyepiece with a 7mm exit pupil

It would simply mean that you were losing a little light, equivalent to using a slightly smaller telescope. If you could keep the exit pupil down to about 6mm you would be laughing. Big fast Dobs cry out for the 21 Ethos which will give the best possible exit pupil/field of view result.

When I swapped a 35 Pan for a 26 Nagler in our 20 inch F4 Dob the increase in brightness was spectacular.

Olly

[Adrian]

I find the easiest way to calculate exit pupil of a particular eyepiece + scope combo is:

eyepiece focal length/f ratio of scope = exit pupil

So if I have an f5 scope and I want a maximum of 6mm, this is given by a 30mm eyepiece

Simples

[Damo636]

It would simply mean that you were losing a little light, equivalent to using a slightly smaller telescope. If you could keep the exit pupil down to about 6mm you would be laughing. Big fast Dobs cry out for the 21 Ethos which will give the best possible exit pupil/field of view result.

When I swapped a 35 Pan for a 26 Nagler in our 20 inch F4 Dob the increase in brightness was spectacular.

Olly

Thanks Olly, you have helped me arrive at a firm decision. I'm going to wait (unusual for me being an impatient sort!) and save up for either the 26 or the 31mm Nagler. I figure i may as well do it right as i plan to have this ep until i'm old and grey and have to be wheeled to the eyepiece, although i'm already pretty grey if truth is to be told.

[ollypenrice]

FWIW the 31 Nagler doesn't suit everyone. I find the 26 an 'easier' EP to use. If you could get to try the 31 I'd recommed that since it's no small investment.

Olly

[johninderby]

One other thing to consider is that the 26mm Nagler is quite a bit smaller and lighter than the 31mm Nagler. I will be getting another one soon (sold my 35mm Pan with the intention of getting the 26mm).

John

[Moonshane]

told you so!

[Damo636]

Ok guys, i will try to get a look through both before forking out. As you say Olly, its no small investment and i want to make sure i get it right. Everyone raves about the 26mm so i am leaning toward it plus i could as Shane suggested sell my 24mm Panoptic to soften the blow.(I do love that ep though).

[Moonshane]

if you can try then it's definitely worth it. the 26mm Nagler is the best eyepiece I have ever looked through (including 21mm Ethos) and owned (including 35mm Panoptic). I have also owned a 24mm Pan and it's also superb. if you can keep it for a short time then you can compare the two (or find someone with a 26mm and compare them side by side in your scope). It's a very different experience.

[Damo636]

Wow, that's high praise indeed Shane! I honestly don't think i would buy an Ethos even if i could afford it. I struggle to see the entire fov with the Nagler's! Of course i am commenting here having never looked through an Ethos and probably would be as well not after what has happened after i looked through a friends Panoptic Two Nagler's (picked up a used once 9mm T6 yesterday on Astro Buy and Sell for a great price) and a Panoptic later and i'm still spending You now have me lusting after the 26mm

[ollypenrice]

With the ultra widefields you do have to move your head to peer into the corners, so to speak. But that's part of the buzz!

Olly

[Damo636]

With the ultra widefields you do have to move your head to peer into the corners, so to speak. But that's part of the buzz!

Olly

I have found this out with the Nagler's Olly. I have been acustomed to the 68 degree of the Hyperion's until now. I was used to getting my eye right in and seeing the whole fov without any effort.