Anyone ever do this?...
Since last night was about the most transparent night in the last several weeks, I took some RGB subs of M51, even with the moon. (Since M51 was the current project - M95 was WAY too close to the moon. Maybe I should have tried H-alpha, but that is another thread...)
Anyway, a colleague had taken a few 5 minute RGB subs a week ago. Seeing was ~3/10 both times. The background counts on the reduced "moon" subs are ~2-8x of the "non-moon" subs. Only a moderate amount in red, more in green, and quite a bit in blue. (It is as if the atmosphere scattered more blue light!) I have never tried this, but I am tempted to subtract a constant value from the reduced moonlit subs before combining them with the moon-free subs. It is easy to come up with a value, by subtracting the processed subs and getting an average pixel count. Anyone ever do this? What are the down sides? (Besides the moon versions being much noisier.) Thanks for any thoughts on this.
Charlie
Since last night was about the most transparent night in the last several weeks, I took some RGB subs of M51, even with the moon. (Since M51 was the current project - M95 was WAY too close to the moon. Maybe I should have tried H-alpha, but that is another thread...)
Anyway, a colleague had taken a few 5 minute RGB subs a week ago. Seeing was ~3/10 both times. The background counts on the reduced "moon" subs are ~2-8x of the "non-moon" subs. Only a moderate amount in red, more in green, and quite a bit in blue. (It is as if the atmosphere scattered more blue light!) I have never tried this, but I am tempted to subtract a constant value from the reduced moonlit subs before combining them with the moon-free subs. It is easy to come up with a value, by subtracting the processed subs and getting an average pixel count. Anyone ever do this? What are the down sides? (Besides the moon versions being much noisier.) Thanks for any thoughts on this.
Charlie
Fort Lewis Observatory: (37.238, -108.052) ~2360m (7744 ft.) elevation.
Darkness - typically 6.5+
Scope - Meade 16" LX200; f6.3 focal reducer
Focus - JMI Smart focus
Camera - SBIG ST-10XE; (~.5"/pixel)
Guiding - AO-8 and/or Meade 5"/DSI/PHD
http://www.fortlewis.edu/observatory
