Astrophotography: July Misc

[comet61]

AKWabbit....The Televue is an APO? or ED version? I do not have a APO scope, however I do have color planetary corrective filters for my 6" achromatic lenses for truer colors and too eliminate the halo affect of the moon. I have had great success using a polarizer filter through my 6" SCT at a tad bit shorter focal length and longer exposure time.

I was wondering if you could write down your exposure formulas for the certain objects you have captured, I could use a better guideline to experiment with later on....I have to literally re-learn everything since I do not use film anymore. I am in the market for a decent CCD camera that won't break the bank. I was hoping the CCD process would have gone down some by now in cost. I do have a monochrome CCD for moon and planets with color filters using the RGB method of stacking. It works, but tedious. And not altogether great for even the more brighter deep sky objects such as Orion or even Andromeda Galaxy, Did pretty will on M13 Glob cluster or the Double Cluster in Cassiopeia.... 

[CptTrips]

Yep, its an APO.  For only 4" of glass it can really kick some butt.  With the focal reducer it gives an amazing field of view and its TACK SHARP.

I don't really have any formulas.  I do my deep sky imaging with a consumer grade Canon XTi that has been modified to remove the IR filter to make it more sensative to red light.  (I used to get good results with a Canon 10d that was unmodified too.)  I haven't use the new camera like the Deep Sky Pro etc but I hear good things.  On my camera, I look at the histogram of a test exposure.  If I have the sky-hump separated off the left edge I just gather as many sub-frames as I can and stack them.  Here is a good discussion: http://www.samirkharusi.net/sub-exposures.html.

But really its even simpler than that.  For the most part I just do 5 min exposures and get as many sub-frames as possible (as well as a set of dark frames to calibrate).  The exception would be something like M42 or M13 if I think 5 min subs would over saturate the cores. If I go past 5 min, I start to get some amp glow showing up in my frame so I just don't bother going longer, I just take more sub-frames.

When I used to use the 10d I didn't have guiding capability so I kept sub-frames to 1 min and used to get some pretty descent images even at that.

Planetary stuff is an entirely different discussion.   

Wab