Fat blue stars
Posted: Sun Jun 24, 2018 9:22 pm
Hi Everyone,
I have a color image of NGC 6791 having blue stars that seem to indicate that they are brighter than they actually are. Please compare my image with this one:
http://darkhorseobservatory.org/images/ ... 1_full.jpg
(Sorry, east is up in their photo but north is up in mine.)
What might account for this?
1. My scope is a 71mm f/5.9 ED doublet from William Optics.
2. Their scope is a 250mm f/5 Takahashi Baker-Ritchey-Chretien.
3. My camera is an Altair 290M uncooled monochrome CMOS camera.
4. Their camera is a SBIG ST-10XME cooled monochrome CCD camera.
5. My filters are Optolong LRGB.
6. Their filters are Astrodon Series E.
In conversations with 'turfpit' he recalls experts saying that blue filters are noisy. If this is true, which I don't doubt, why should a blue star appear fatter in my image?
Any thoughts will be GREATLY appreciated.
EDIT: I wonder if this could be mitigated by increasing the number of darks from 30 to 50 or more?
Brian
I have a color image of NGC 6791 having blue stars that seem to indicate that they are brighter than they actually are. Please compare my image with this one:
http://darkhorseobservatory.org/images/ ... 1_full.jpg
(Sorry, east is up in their photo but north is up in mine.)
What might account for this?
1. My scope is a 71mm f/5.9 ED doublet from William Optics.
2. Their scope is a 250mm f/5 Takahashi Baker-Ritchey-Chretien.
3. My camera is an Altair 290M uncooled monochrome CMOS camera.
4. Their camera is a SBIG ST-10XME cooled monochrome CCD camera.
5. My filters are Optolong LRGB.
6. Their filters are Astrodon Series E.
In conversations with 'turfpit' he recalls experts saying that blue filters are noisy. If this is true, which I don't doubt, why should a blue star appear fatter in my image?
Any thoughts will be GREATLY appreciated.
EDIT: I wonder if this could be mitigated by increasing the number of darks from 30 to 50 or more?
Brian