Ha Help

[Gary Beal]

Thanks Eric, and again, thanks to all.
Eric from memory I used a bank of about 6 darks, and yes, median (or was it Sigma??) combined them. I do recall using just the one darl for the first real look, but after that used the combo.
This is perhaps academic now, as I sold the ST8, and am looking another camera, probably one shot colour. Same old problem though, darks and flats.
Great to have all this help around me though, I appreciate it.
Gary

[optwebman]

Gary,Yes the best darks are always the one you take at the time of the image and also flats are best done right after the darks. MaximDL allows for a giant library of darks to pick from and again "Medium" combine them for use as your master. If you want to add the smooth soft pillow effect seek out Neat Image you will find it to be a complete processing tool all on it's own with a plug-in for Photoshop so you don't need to exit the program. It is a must tool for the Ha Nebula kind of guy, like us!

OPTwebman

[neilfleming]

Hey there, Gary. The advice above is indeed sound.

Take a look at CCDStack some time. With it, you can use RMS scaling when applying the calibration, and adjust for both time AND temperature scaling.

That being said, I still find it best to build up a large library of assorted time and temperature darks and temperature-scaled bias frames.

Depending on your camera and observing conditions, I'd strongly suggest 25+ individual dark subexposures (subs), combined into a master dark. I find that a clip min/max combine works best. This approach throws away the outlying pixel values, and mean combines the remainders.

...Neil