Best EP for DSO

[YKSE]

2 hours ago, John said:

All that said, I'm not sure that I'd splash out on Ethos and Naglers if my scopes were all around F/10.

I think John hit the nail on the head here

Your C6 has quite some amount of field curvature, the wide FOV EP you're using, the more field curvature will be seen, i.e. focused stars in center, but out of focus stars in edge. Ethos will clearly show you more out of focus stars than any narrower FOV EPs, simply because of wider FOV.

If you're sticking with C6 as your primary scope for DSO and wider FOV eyepieces, a f6.3 reducer might be a first upgrade to start with, it will flatten the field of C6, its clear aperture of 24mm should cause very little vigetting in 24mm Pan or 32mm plossl (both have 27mm field stop). The reducer brings down the focal ratio to f6.3, both 32mm and 24mm will give about 1.7deg TFOV, also very useful exit pupil 5mm (32/6.3) and 3.8mm (24/6.3) for large extended DSO.

Saving to buy stuffs you really want is a good way, in the meaning, have a better understanding of the whole optical chain involved can help you to make even better decisions.

http://starizona.com/acb/basics/equipmentbasics.aspx

[Richard Hather]

Thank you everyone for your help I will probably upgrade to a 8se OTA in a few years that is but I wanted to first build up my EP collection and get all the other bits and pieces storage for tripod and OTA storage etc...

So much to consider I will at least go for the TV 24mm PAN and decide after that.

[rockystar]

On ‎07‎/‎06‎/‎2016 at 22:00, Stub Mandrel said:

From the 24m Explore Scientific EP linked above:

"Although Nitrogen is a fine choice that will last for many years, Argon is a larger molecule that maintains its protective properties over a wider range of temperatures, and is even more resistant to diffusion thereby further extending the protective waterproof environment of the eyepiece body. "

This didn't seem right and has sent me off on a meaningless voyage through some physical chemistry!

The atomic radius of argon is 71pm (picometres) and the atomic radius of Nitrogen is 65pm.

BUT they are clear they are clear they mean molecules, and the nitrogen in your eyepiece is in pairs of two atoms in a sausage shape. Atomic radius is meaningless for molecules, but we can use the Van der Waals radius, which models the size of a molecule or atom for modelling some of their properties. In this case Argon still wins with 188pm and Nitrogen loses with 155pm.

But, hey! We are worrying about diffusion and for this we need the kinetic diameter which is what determines how they behave in collisions (which determines how fast the gas can diffuse). The kinetic diameter of  nitrogen is 361pm and that of Argon is 341pm.

I'm sure ES will argue that the Van der Walls radius is what counts, but I reckon your nitrogen filled EP will last 6% longer than if they were filled with Argon - perhaps!

^^^^^ this is what i love about amateur astronomers: "let's just dip into a bit of molecular chemistry to make sure that statement is accurate" ?