Quote:
Originally Posted by Merlin66
The Imaging Source curve for the DMK21 chip (ICX098BL) shows about 50% at 4000 and 7000.... this seems to match the Pink curve??????
Very interesting stuff!
A dark and sky correction may make some difference , but looking good...
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I'll have to examine the curve again
... from my memory of it - based on shape only, I thought the green curve was better.
Quote:
Originally Posted by Terry B
Al
I think the camera response curves are going to be dodgy for a few reasons. I'm not sure how we can avoid this. The A stars (like sirius) arn't very bright in the IR so the levels are low compared to the green etc. When you try to divide another spectrum by this curve it enhances the IR more than it should. I tried this with a red star and got a vastly enhanced IR end to the spectrum that wasn't real.
The same problem will occur if you use a red M star as the response curve and try to calibrate a hotter star but with the opposite effect of over enhancing the blue end.
I suppose a more realistic result would be achieved by making a curve from a "B G and M' star and averaging them. The difficulty here would be how to normalise them first so that the weighting for each spectrum was even. Maybe normalise all of them at a specific green frequency and go from there. 
In the end I don't think it matters terribly as we arn't measuring the flux at a particular frequency although this is possible with reference stars etc. |
I agree. In theory, if we had a uniform light source across all frequencies, we could very simply get a perfect camera response.
Because we are using non-uniform light sources, any area where the signal is low becomes very inaccurate.
I think I can see 2 possible ways to establish a wide spectrum camera response curve:
- Average the normalised camera response curves from B, G and M stars as you suggested (if necessary expand that to include the other classes too, but I don't think that would be necessary);
- Join the low wavelength section from the B spectrum, to the middle from the G, to the long wavelength section of the M class. Might be a bit fiddly scaling the connections, but this should address the magnification of errors/noise that a low signal causes.
Al.