ASTRO: M82

Another windy night in April gave me a rather low detail colour image of
M82, so I combined it with a b/w image I took two or three years ago.

Taken from the middle of Berlin, luminance with a C8 at f/6.3 on an EQ6
Skyscan, SXV-H9 camera, 62x5 minutes, colour with a 10" Meade ACF at f/6.4
on a G11 mount, QHY8 camera, 9x10 minutes.

The picture can also be found at
http://ccd-astronomy.de/temp2/M82colourgut.jpg

Stefan

Stefan Lilge wrote:
Another windy night in April gave me a rather low detail colour image of
M82, so I combined it with a b/w image I took two or three years ago.

Taken from the middle of Berlin, luminance with a C8 at f/6.3 on an EQ6
Skyscan, SXV-H9 camera, 62x5 minutes, colour with a 10" Meade ACF at f/6.4
on a G11 mount, QHY8 camera, 9x10 minutes.

The picture can also be found at
http://ccd-astronomy.de/temp2/M82colourgut.jpg

Stefan


You've been busy with all these new images. One thing I notice about
the new camera, looking at the channels, is that it appears weak in
blue, strong in green and red. I've seen that in some others using the
camera. Some are seem far too strong in green though yours don't seem
to have that issue. Not sure if that's due to the two green to one red
and blue pixel of the matrix with blue being low sensitivity of the chip
or what. Works well for something like M82 but 4088/Arp 85 comes out
rather red compared to the LRGB images I see of it including your 8"
f/6.3 MX716 shot of it.

Have you tried shooting a G2 star high in the sky to see if it comes out
equal in the color channels?

Rick


--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

Rick,

the raw pictures have an extreme bias to green, which is reduced by using a
flat from my electroluminiscent flatfield foil (which also has it's
intensity maximum in green). If I use a skyflat the outcome is rather red,
obviously because the flat is blueish.
After flatfielding I usually have to turn down green to about 50% and boost
blue by about 30-50% to get colours that are "close" to what I expect. I'll
have to try a G2 star, but when colour is concerned my approach is usually
to play with the sliders until it looks OK to me :-)

Stefan

"Rick Johnson" schrieb im Newsbeitrag
ster.com...
Stefan Lilge wrote:
Another windy night in April gave me a rather low detail colour image of
M82, so I combined it with a b/w image I took two or three years ago.

Taken from the middle of Berlin, luminance with a C8 at f/6.3 on an EQ6
Skyscan, SXV-H9 camera, 62x5 minutes, colour with a 10" Meade ACF at
f/6.4 on a G11 mount, QHY8 camera, 9x10 minutes.

The picture can also be found at
http://ccd-astronomy.de/temp2/M82colourgut.jpg

Stefan


You've been busy with all these new images. One thing I notice about the
new camera, looking at the channels, is that it appears weak in blue,
strong in green and red. I've seen that in some others using the camera.
Some are seem far too strong in green though yours don't seem to have that
issue. Not sure if that's due to the two green to one red and blue pixel
of the matrix with blue being low sensitivity of the chip or what. Works
well for something like M82 but 4088/Arp 85 comes out rather red compared
to the LRGB images I see of it including your 8" f/6.3 MX716 shot of it.

Have you tried shooting a G2 star high in the sky to see if it comes out
equal in the color channels?

Rick


--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

Stefan Lilge wrote:
Rick,

the raw pictures have an extreme bias to green, which is reduced by using a
flat from my electroluminiscent flatfield foil (which also has it's
intensity maximum in green). If I use a skyflat the outcome is rather red,
obviously because the flat is blueish.
After flatfielding I usually have to turn down green to about 50% and boost
blue by about 30-50% to get colours that are "close" to what I expect. I'll
have to try a G2 star, but when colour is concerned my approach is usually
to play with the sliders until it looks OK to me :-)

Stefan

Yep, I use that as a starting point though usually find little change is
then needed. I have a library of G2 data of the same star at various
altitudes. Above about 60 degrees altitude there's little change, below
that blue has to be boosted and if I get down to 30 (bad seeing usually
limits this) I have to do a light green boost as well.

Your comment about sky flats making the image red explains why I see
some using that camera that turn out over red images. I can see the
green issue as light pollution favors it as well as two of the 4 pixels
being green. Those red images were giving me fits to understand. I've
never used one shot color so am totally in the dark about it. I'm
slowly getting filtered mono down. Not sure I'd want to even try OSC as
yet. My brain can only handle one type of problem at a time.

Rick


--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".




--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".

Rick,

Not sure I'd want to even try OSC as yet. My brain can only handle one
type of problem at a time.

actually I find OSC imaging and especially processing much easier than LRGB.
Only problem is that results with a mono camera are _much_ better, at least
for me...

Stefan