Quote:
Originally Posted by RickS
I have tried combining a best FWHM integration with a best SNR integration a few times in the past with a blend function favouring the FWHM integration for bright areas and the SNR integration for dim areas. Sounds very similar to what you've done, Lee.
I found that it works, but I haven't convinced myself that it gives a better result than applying a little careful noise reduction to the FWHM integration. If I was scrabbling really hard to find enough good quality subs I'd try it again, I guess.
I don't see why you'd get an actual reduction in FWHM. Sounds like you've just confused the measuring algorithm 
Cheers,
Rick. |
Yeah, there's definitely something not right with the FWHM measurements. For the record, I'm not suggesting it actually did go down in FWHM, that doesn't make any sense.
Fair point on doing the noise reduction instead. When you tried a similar thing, do you know what the approximate ratio of bad to good subs was? In this case it was roughly 2:1 in favour of bad subs, and I still need a lot more data on this subject, so I expect to be gathering more
and applying noise reduction.
Quote:
Originally Posted by Atmos
I had thought of doing something similar to that Lee in an attempt to salvage TERRIBLE data. Had really nice red and blue data but green was bad due to the auto guider going on the fritz. Wanted to use PixelMath and mask the green FWHM with the red and turn lines into fainter dots 
Didn't work so well but what you've done sounds good. As for the lower FWHM, what you have done is increased the central region with the poor data which has increased the "half maximum". You've created an artificial cone |
Cheers Colin. I'm not sure I follow you though: why would increasing the half maximum decrease the FWHM? I suppose it's likely that dimmer stars would have had their profiles altered to some extent due to it being an intensity-based mask, but I still don't follow how adding the bad data to the good data improves on the good data's FWHM.