|
Hi Rob, that's not quite what I was asking. The human eye can generally dilate to around 7mm, although this decreases with age. So, one school of thought is that an exit pupil that is larger than your own dilated pupil means you are 'wasting' light.
The question I am asking relates to large exit pupils in reflectors, i.e. scopes with a central obstruction. I have read that if the exit pupil gets too large, then you start to see the secondary mirror, which obviously degrades/ruins the image of the object you're trying to look at. This isn't an issue in refractors as there is no central obstruction.
I am 37 years old, so my pupil may not be able to dilate tp 7mm any more, but the lower the magnification the brighter the object will appear. More importantly (for this discussion) the wider the field of view will be.
Therefore, the real question is how wide a field can I obtain with either an 8" f/6 Dob or a 10" f/5 Dob, subject to the limitation of exit pupil?
To give the question more context, this thought process was sparked off by the fact that I couldn't fit the whole Eta Carina Nebula in the fov of my 8" Dob with my widest eyepiece, a GSO 32mm wide view.
Hope some experts out there can provide an answer!
Thanks
Morton
|