I was up early this morning to do an imaging run on the Orion nebula (M42), with my 8" f5 imaging newt. Of course this is a pretty bright object, and having not imaged it before I was uncertain of what sort of Sub time was appropriate and what ISO?
Having been working with some fainter DSOs I had the camera set for ISO800 (Camera is a Canon 450D DSLR and this seems to be a good choice for this camera). I tried an initial few test shots at 40 seconds (guided BTW), and that looked good. So I ran 40 subs at 40 seconds. Later after putting them through DSS, with 40 Darks, and 10 Offset/bias frames, the resulting stacked image has burned out the trapezium significantly - but great gas cloud detail. I tried to fix up the over-exposed trapezium with Photoshop but it turns out to be a compromise.
So from the experienced folks, what is correct technique for imaging for detail in an object like M42? How do I get the Trapezium and the gas clouds?
In my old film processing days you used to be able to hold back over-exposure when printing simply by using a waved paddle to obscure the light burn on the paper. Is there a modern equivalent?
The Orion Nebula has a very wide brightness range, so you have to take sets of subs at different exposures. Long exposures for the faint outer cloud and short ones (just a few seconds) for the trap and bright core. They are then combined with masks, layers or feathered selections in a program like photoshop.
