goober
18-01-2008, 04:21 PM
I'm on the lookout for a workable scale for judging transparency when observing.
http://www.iceinspace.com.au/index.php?id=63,196,0,0,1,0
I used to the above scale, but it really doesn't seem to work. From my light polluted back yard, I can always see Omega Centauri and 47 Tucanae, although I have sky glow. So I guess by this scale the transparency is always around 5.5-6.5 out of 7 for me - which feels wrong.
I then moved on to an "out of 10" scale, where I'd just guestimate it, but that was worse.
Nortons, and several other books, mention using a known constellation and determining how "faint" you can go with the naked eye. That seems to be the best solution. In fact, Nortons even provide a magnitude map of the south celestial pole, so your reference stars are always there. Harrington gives us Crux in his Star Ware book, but that is too hard to pick out over summer as it wheels low in the south.
I may go with the Nortons/SCP method, but through I'd throw it out there to see if there's something better.
http://www.iceinspace.com.au/index.php?id=63,196,0,0,1,0
I used to the above scale, but it really doesn't seem to work. From my light polluted back yard, I can always see Omega Centauri and 47 Tucanae, although I have sky glow. So I guess by this scale the transparency is always around 5.5-6.5 out of 7 for me - which feels wrong.
I then moved on to an "out of 10" scale, where I'd just guestimate it, but that was worse.
Nortons, and several other books, mention using a known constellation and determining how "faint" you can go with the naked eye. That seems to be the best solution. In fact, Nortons even provide a magnitude map of the south celestial pole, so your reference stars are always there. Harrington gives us Crux in his Star Ware book, but that is too hard to pick out over summer as it wheels low in the south.
I may go with the Nortons/SCP method, but through I'd throw it out there to see if there's something better.