Posts Made By: Alexis Cousein

Lee Spain said:

I've seen a lot of really long focal length 2" eyepieces (53mm to 80mm) on a nonsponsor site. That would give about 15x on my 8" Dob. Is magnification that low worth having for seeking DSOs?

Not really. Those eyepieces are meant for "slower" scopes.

In fast scopes, it's better to use eyepieces with a larger apparent field of view that show the same true field, so that you can look at the same piece of sky under higher magnification. Given that a 40mm Paragon or Pentax XW and Nagler 31T5 have a field stop close to the maximum reachable in a 2" eyepiece, there's little point in anything longer if the exit pupil will be too large to be optimal anyway.

While you *can* use exit pupils larger than your fully dilated eye pupil, there is no point in it other than to show more sky - extended objects are smaller but the surface brightness is the same (or smaller), and point objects become dimmer.

Darren Drake said:

Is there a point when the level of CO2 in the atmosphere no longer adds to the amount of energy that becomes trapped?

If you don't mind an atmosphere much like that of Venus -- sure, there probably is a limit. It's most probably not a comfortable one, though.

I'll bite:

26T5
16T5
13Ethos
9T6
2x barlow (1.25").

26T5/16T5 can be replaced with 31T5/20T5 if you want.