Understanding exit pupil and filters in deep sky observing

[John]

I've just been experimenting. Going from viewing M76 (the Little Dumbell Nebula) straight to Jupiter it took some time, about 10-15 minutes, for my eye to adjust to the brightness of Jupiter so that more than the 2 main belts were seen.

Then I tried coming inside to a lighted room, spent a few moments looking at the ceiling light, then went straight back to the eyepiece and Jupiter......

.......fell over the step on the way out and broke my darn nose......

Only joking ... .... my observing eye adjusted quite a lot more quickly to Jupiters brightness, I'd estimate around 1/3rd of the time and then I was seing multiple coud belts plus a nice equatorial festoon in the EQ zone.

The scope was my 12" dob and the eyepiece an 8mm Tele Vue plossl for 199x. No filter used.

[Piero]

I also experimented a bit although the clouds gave me a very tough time! 

Tried the OIII filter (normal sky, stars ~4.0 mag) (just preliminary results).

M42, the extension is the nebula with the Pan 24 (15x, 4.0mm ep) is well defined and nice to see. I prefer the view with the OIII than the UHC under this sky condition with the Pan24 and Plossl20 (my old and first serious eyepiece, 18x, 3.3mm ep but actually showing very similar brightness than the Pan 24). Again, I have a feeling that the contrast is improved with the Plossl 20. The image is not really darker, but the nebula borders seem more defined.

Quite happy about this as it could become a nice eyepiece for nebulae, removing the problem of adding/removing the filter on the diagonal. 

I didn't have time to test further with the Nag7 (51x, 1.2mm ep)... clouds... 

After a nice chat with Gerry (jetstream) in another thread, I gave a try to C49-C50 (Rosette nebula with associated cluster). I was literally chased by the clouds which were covering Orion and shortly coming to Monoceros. Therefore, I left the OIII filter on the diagonal and with the Pan24 I followed the line Meissa->Betelgeuse. I am quite sure I saw the cluster as the structure matched quite closely in Carte du CIel. I cannot say to be confident regarding the nebula instead. Have to say though that I was in a rush due to the coming clouds and these things require time, patience and proper adverted vision (beside a better sky!). Next time, next time.. certainly I won't give up!  

  

Jupiter

The clouds were reaching C49/C50, so I moved quickly to east pointing at Jupiter. I only looked though it with my Nag7 and Vixen5 (72x, 0.8 ep). Although I believe that these magnifications are a bit too low for seeing subtle details on this planet, as John said, also for me it took a couple of minutes for seeing (in this case) the two major bands. 

p.s. very nice to see Ganymede coming out on the left (as seen on my refractor) of the planet at about 7pm. 

5 minutes later I didn't know whether there were more clouds on earth or on Jupiter! 

M81-82

well, I cannot say much except that the challenge continue here.. I saw them under this sky with my previous bins 15x70, and hoped to see them with the TV60, but... clouds again.. nevermind, next time! 

Luckily, a patched of clear sky at the zenith to west! Yuppie!! OIII packed, I just continued for a quick wide field look at the double cluster, M31, and Cepheus's beauties. 

[jetstream]

Hi Piero, great that you got out try some things!   In order to see some of these faint nebula (Rosette is a bright faint nebula) there should be no cloud up there- even dust etc that can't be seen will hurt the sky transparency and sky darkness should be at least in the high 5's NELM. To see these things well I go to the darkest skies available, here that is 21.2-21.7 mag, depending on the time of year. I can see the veil under lighter skies, but it does better under darker skies.

Good luck with the pursuit!