M81 / M82 in HaRGB

Comment

Comment by spike77 on May 20, 2011 at 3:21am

nice neil great work got the red kicking in m82

Comment by Neil Heacock on May 20, 2011 at 2:58am

Sorry for the delay Al.

That sounds right to me. Here is the formula I use for these various calibration frames:
Darks - Shot with the cap over the scope at the same ISO, temperature, and shutter duration as the original light frames.

Flats - shot against an evenly illuminated background with a diffuser over the scope/lens until the mean signal is ~25k - the histogram spike is 1/3 or so from the left wall. I use a piece of polyurethane and shoot the daytime sky. ISO, temp and duration are not important, we're trying to get the signal in a certain place here.

Flat Darks - Shot with the cap over the scope at the same ISO, temperature and shutter duration as the flats. I've only done this one picture with them and I'll probably not use them again as they had no apparent benefit over the bias frames and essentially contain the same dark signal as the bias frames.

Bias - Shot with the cap over the scope at maximum shutter speed.

I hope that helps. Please let me know about any guiding questions you may have and if I can help you I will.

-Neil

Comment by Al McAdam on May 13, 2011 at 1:36pm

Great stuff Neil, I am about to get into guiding so I may ask other questions later. I have been taking flats using a white T-shirt folded over the front of my scope, Dark flats scope cap on and shooting the same length of time and the same temp, Bias I shoot the scope cap at 1/4000th and then darks I pull the camera out put the T on a black suface and shoot the same length of time as the images all the above at the same iso and temp. How does that sound? I was amazed at the number you took and was that from a library of shots you had taken or done at the time of the images? I really can't wait for the guide stuff to arrive.