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Just curious though: why IC342? It's listed as having a surface brightness of mag 15.0 - have you ever come close to seeing something as faint as that? As far as I can tell, SAC have even de-listed it from their 10,000+ object database (new version 7.5).
I found visual magnitudes for this one of 8.4 (U2K deep sky field guide 1st ed) and 12.0 (SAC previous version 7.2) - which one do you think is correct?

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Mark

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IC 342 has an area of (18x17) about 300 square arcminutes. Also has an Sb of about 15.0.

A gain of 5 magnitudes corresponds to 100x area and 6 magnitudes corresponds to 250x area. So, it's visual magnitude would be about 6.2 magnitudes brighter than it's Sb. Therefore MagV is about 9. But that is just about so useless in this case as to be meaningless.

"Observing Handbook and Catlogue of Deep Sky Objects", Lughinbuhl and Skiff, reports IC342 is 18x17, Sb 15.2 and B=9.1. Also that it is seen as approx 12 arcmin diameter in small apertures (80mm-200mm under mag 7? skies).

NSOG states 22x22 = 484 SQ arcmin with Sb 15.0. At 484x area, that would be equivalent to about a 6.8 mag differece. They list Mv at 8.4, a 6.6mag difference.

So, it seems the MB and MV around 8.4 to 9.0 are correct.

I just posted the other day on some of the faintest Sb objects I've seen, in the Limits of 25x100 thread.. I've reached about Sb 14.0 to 14.5, depending on which source.

edz

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