Quote:
Originally Posted by Scooter
I guess the problem is going to be knowing what objects are just not going to be worth chasing due to the light polution hence my original comment regarding magnitude. Its it fair to say if I can't see something of mag X then don't bother looking for anything less or equal? Also what role does seeing play (should I be working out what the seeing is first and then if it is x I could target these objects vs y only bother with these?
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CdC, as mentioned by Terry, gives surface brightness for extended objects (M83:12.8). While you were looking in the right place for M83 I'm sure you must have seen stars fainter than M83's mag of 7.6 - but the light M83 emits is spread out over a larger area than a star's pinprick. M33 is an infamous example: mag 5.7, surface brightness 14.2. In Coonabarabran I can see it with my naked eye - not even trying... but here in Sydney my 8" has trouble finding it, unless there is Absolutely No Cloud (for whomever can remember those days.)
Seeing does not so much decide whether or not we can see some object, but rather how much detail we can discern - or in simple terms, how sharp things are. Whilst darkness does not change much over time, seeing may vary on a scale of seconds (provided your mirror is at thermal equilibrium), so patience is often rewarded.
There is no hard and fast formula to decide what objects to try for under any given set of conditions - even after many years I do a lot of trial and a lot of error, too. The surprises are the best, though!
I cannot judge whether Australian skies can compare to the altiplano - but one thing many Australians underestimate is how easily accessible our dark skies are - and how much of it there still is.
