Quote:
Originally Posted by Merlin66
Who's been a busy boy then...
I've been using the few minutes of sunshine to image with the SM60 ( and get practise in processing Ha images) The nights have still been too cloudy to be able to do ANY imaging!!!
Al, I think the fall off of the camera responce below 4000 and above 7000 is so rapid/ steep that the smallest error in compensation with throw things out dramatically. I know I have that problem with the Canon 350 ( the 300D has the Baader UV-IR filter fitted, and that gives a very clean cut-off at 3950 and 7000)
Certainly try different reference stars, you may be able to find a compromise.
What if you calibrate on the Betelgeuse and then "correct" the Sirius spectra????
|
G"Day Ken.
I've been playing about with similar arcane ideas
.
Another thing that could influence this is the black point on the image. This lot of spectra that I took has the black point at about 11000 counts on the intensity axis. Probably the result of either not having the brightness control set up zero, or maybe from using so much gain in order to keep exposure time down (due to seeing). 11000 divided by next to nothing gives a fantastic lie for camera response...
That zero error or black point noise I think could be contributing to the spurious camera response curves. What do you think?
I started having a play with subtracting a constant from the spectrum and I think that's part of the way to go. I'm about the call it quits for the night though.
So, I'm starting to think I need to put a step into my work flow, that I subtract the black point offset from the raw spectrum before doing any other operations.
I think that if that doesn't fix the problem, then that combined with averaging the response curves (across the star classes) should.
Ideas?
Al.