Quote:
Originally Posted by Glenpiper
I think a 0.6sec exposure is way too short, unless you have a very large scope and a very bright target. I assumed you were using a C8+DSLR, is this correct and if so, is the DSLR a CMOS sensor? I'm using a C8 with a monochrome, binned, CCD and still need to stack 5 x20sec exposures to get a reasonable SNR.
Bernard
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I used the C8, with an f/6.3 FR, the SA and my DMK 21. I find that with brightness =0, Gain = 1023, and exposure = 0.6s the eta spectrum uses most of the histogram without clipping and the homunculus is just starting to appear in the zero order image.
Quote:
Originally Posted by Glenpiper
Ooops, error ... my exposures were 5x 5sec (where the star was included) but I reduced it to 5x 4sec for just the spectrum.
As the attached raw image shows, the star and Ha are saturated but the areas of interest have a reasonable SNR. The stars are out of focus, which is normal when the spectrum is focused.
Bernard
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Very interesting - thanks for posting Bernard. I haven't been exposing my spectra anywhere near as much as that!
I've attached a jpg copy of the spectrum as captured from the eta impostor the other night, and two previous eta spectra including the zero order.
Part of the reason I think I ballsed up the eta the other night was I was practicing taking spectra without the zero order. Maybe I'd have noticed the lack of homunculus in the zero order if I'd done it the old way
.
Al.