ASTRO: NGC6946

Back in September I took a single 6 minute frame of this galaxy due to
clouds rolling in. It came out surprisingly well. Two nights later, I
took 4 more Lum frames and some RGB but they were through clouds.
Since, at the time I didn't know how to handle this I didn't process
them. I found them the other day and decided to see if I could salvage
something. Unfortunately, I don't have any flats from that stint.
Never took any and realigned the camera the next day figuring those were
a bust. So I had to use flats from a few days earlier and they don't
quite work at the corners where, due to my old Meade focuser, I had some
rather deep vignetting. So ignore the bright corners. I found I had no
darks from that time frame either. The camera has changed quite a bit
since then so using a modern dark put a few holes into the galaxy. I
probably should have scaled a 5 minute dark from that era but I didn't.
Some other time. Why these were taken at 6 minutes I don't know. I
know the single frame was an accident but why repeat it? That though
was taken at -5C while this was at -25C. I find scaling over that
temperature difference never works with this camera. It will have to do
until next year.

I see several faint fuzzies and one not so faint one. NED is still down
and SIMBAD seems not to know a thing about any of these guys, even the
bright one much to my amazement.

14" LX200R@f/10, L=5x6 min, RGB=3x6 each all binned 2x2, STL-11000M,
Paramount ME

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, great result for something you almost forgot about. You get the hang
of colour processing fast, colours look very good. I almost have given up on
colour as I never seem to get satisfactory results.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
...
Back in September I took a single 6 minute frame of this galaxy due to
clouds rolling in. It came out surprisingly well. Two nights later, I
took 4 more Lum frames and some RGB but they were through clouds.
Since, at the time I didn't know how to handle this I didn't process
them. I found them the other day and decided to see if I could salvage
something. Unfortunately, I don't have any flats from that stint.
Never took any and realigned the camera the next day figuring those were
a bust. So I had to use flats from a few days earlier and they don't
quite work at the corners where, due to my old Meade focuser, I had some
rather deep vignetting. So ignore the bright corners. I found I had no
darks from that time frame either. The camera has changed quite a bit
since then so using a modern dark put a few holes into the galaxy. I
probably should have scaled a 5 minute dark from that era but I didn't.
Some other time. Why these were taken at 6 minutes I don't know. I
know the single frame was an accident but why repeat it? That though
was taken at -5C while this was at -25C. I find scaling over that
temperature difference never works with this camera. It will have to do
until next year.

I see several faint fuzzies and one not so faint one. NED is still down
and SIMBAD seems not to know a thing about any of these guys, even the
bright one much to my amazement.

14" LX200R@f/10, L=5x6 min, RGB=3x6 each all binned 2x2, STL-11000M,
Paramount ME

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".

One of the whiz kids at the school I help with astronomy showed me a
method that seems to work (well not for PacMan. First process the Lum
frame to where you want it for a black and white shot. Save that. Then
process one of the color frames. But note every setting for every step.
Since I use only curves this is easy as I save each curve used. I
have now a stock set of curves for various things. Usually it takes two
or three applications of the same curve, as they are rather gentle.
Once I get the first color frame (red if that's the dominant color, Blue
if it is and if the object is mostly white forget using color or try
green first. Anyway I then process the other two the exact same way
saving each result as a TIFF file. Then I make an empty RGB frame and
paste in the three colors. Then I find I need to up the saturation to
about +35% or the colors will be washed out. I save that RGB (that's
the PacMan photo right there but without the upped saturation. Then I
reopen the Lum frame, change it to RGB with the Mode menu and paste in
the RGB image. Then change the layer from Normal to Color (way down the
list near the bottom). Flatten and you're done. If the color is too
washed out then go back and increase the saturation of the RGB image and
try again. As a last step I try to set the background to black.
Usually, as in the case of 6946 this is a very small change. For some
reason it threw the Veil shot into wild colors. I've since fixed the
green cast even better than in the second posted image by finding a dim
G1 star (couldn't find a G2 dim enough) so that it had a max ADU count
of about 15,000 (60,000 is max for the 11000 chip). I then set that to
the same RGB levels and that got rid of most of the green cast. While
there is a way to do that in Photoshop CS I need the whiz kid to show
that to me again. In the meantime I used a tool in Elements that does
this with a simple mouse click. But Elements only works with 8 bit
files so it has to be a very last step before converting to JPEG.
Fortunately it will read 16 bit TIFF files, just not work in that mode.

Oops, forgot one step. After processing the three color frames the same
I do check a dark area to see if the background is really at the same
level. I do this by opening the levels box, with preview checked and
then watch the info box to check K for that area. If one is brighter
than the others (usually green is if any are) I use the black level
adjustment arrow and move it off 0 and up to whatever it takes to change
the background to the about the same as the other two. Sometimes I need
to adjust two but usually just the green. I'd blame it on light
pollution but there is none out here. Maybe its starlight reflecting
off all the green pine trees. In order to do this step process the
color images so there is some room to do this without clipping the
object's histogram I leave about 10 to 20 unit counts below the dark
end of the image when making my curves adjustments.

Rick



Stefan Lilge wrote:

Rick, great result for something you almost forgot about. You get the
hang of colour processing fast, colours look very good. I almost have
given up on colour as I never seem to get satisfactory results.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
...

Back in September I took a single 6 minute frame of this galaxy due to
clouds rolling in. It came out surprisingly well. Two nights later, I
took 4 more Lum frames and some RGB but they were through clouds.
Since, at the time I didn't know how to handle this I didn't process
them. I found them the other day and decided to see if I could salvage
something. Unfortunately, I don't have any flats from that stint.
Never took any and realigned the camera the next day figuring those were
a bust. So I had to use flats from a few days earlier and they don't
quite work at the corners where, due to my old Meade focuser, I had some
rather deep vignetting. So ignore the bright corners. I found I had no
darks from that time frame either. The camera has changed quite a bit
since then so using a modern dark put a few holes into the galaxy. I
probably should have scaled a 5 minute dark from that era but I didn't.
Some other time. Why these were taken at 6 minutes I don't know. I
know the single frame was an accident but why repeat it? That though
was taken at -5C while this was at -25C. I find scaling over that
temperature difference never works with this camera. It will have to do
until next year.

I see several faint fuzzies and one not so faint one. NED is still down
and SIMBAD seems not to know a thing about any of these guys, even the
bright one much to my amazement.

14" LX200R@f/10, L=5x6 min, RGB=3x6 each all binned 2x2, STL-11000M,
Paramount ME

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".

Thanks for the detailed explanation Rick. I have saved it to my harddisk for
future reference.
I recently got myself a new filter wheel (unmotorized unfortunately, the
motorized ones are so incredibly expensive...), so I'll probably do some
colour shots in the next clear nights.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
...
One of the whiz kids at the school I help with astronomy showed me a
method that seems to work (well not for PacMan. First process the Lum
frame to where you want it for a black and white shot. Save that. Then
process one of the color frames. But note every setting for every step.
Since I use only curves this is easy as I save each curve used. I have
now a stock set of curves for various things. Usually it takes two or
three applications of the same curve, as they are rather gentle. Once I
get the first color frame (red if that's the dominant color, Blue if it is
and if the object is mostly white forget using color or try green first.
Anyway I then process the other two the exact same way saving each result
as a TIFF file. Then I make an empty RGB frame and paste in the three
colors. Then I find I need to up the saturation to about +35% or the
colors will be washed out. I save that RGB (that's the PacMan photo right
there but without the upped saturation. Then I reopen the Lum frame,
change it to RGB with the Mode menu and paste in the RGB image. Then
change the layer from Normal to Color (way down the list near the bottom).
Flatten and you're done. If the color is too washed out then go back and
increase the saturation of the RGB image and try again. As a last step I
try to set the background to black. Usually, as in the case of 6946 this
is a very small change. For some reason it threw the Veil shot into wild
colors. I've since fixed the green cast even better than in the second
posted image by finding a dim G1 star (couldn't find a G2 dim enough) so
that it had a max ADU count of about 15,000 (60,000 is max for the 11000
chip). I then set that to the same RGB levels and that got rid of most of
the green cast. While there is a way to do that in Photoshop CS I need
the whiz kid to show that to me again. In the meantime I used a tool in
Elements that does this with a simple mouse click. But Elements only
works with 8 bit files so it has to be a very last step before converting
to JPEG. Fortunately it will read 16 bit TIFF files, just not work in that
mode.

Oops, forgot one step. After processing the three color frames the same I
do check a dark area to see if the background is really at the same level.
I do this by opening the levels box, with preview checked and then watch
the info box to check K for that area. If one is brighter than the others
(usually green is if any are) I use the black level adjustment arrow and
move it off 0 and up to whatever it takes to change the background to the
about the same as the other two. Sometimes I need to adjust two but
usually just the green. I'd blame it on light pollution but there is none
out here. Maybe its starlight reflecting off all the green pine trees.
In order to do this step process the color images so there is some room to
do this without clipping the object's histogram I leave about 10 to 20
unit counts below the dark end of the image when making my curves
adjustments.

Rick



Stefan Lilge wrote:

Rick, great result for something you almost forgot about. You get the
hang of colour processing fast, colours look very good. I almost have
given up on colour as I never seem to get satisfactory results.

Stefan

"Rick Johnson" schrieb im Newsbeitrag
...

Back in September I took a single 6 minute frame of this galaxy due to
clouds rolling in. It came out surprisingly well. Two nights later, I
took 4 more Lum frames and some RGB but they were through clouds.
Since, at the time I didn't know how to handle this I didn't process
them. I found them the other day and decided to see if I could salvage
something. Unfortunately, I don't have any flats from that stint.
Never took any and realigned the camera the next day figuring those were
a bust. So I had to use flats from a few days earlier and they don't
quite work at the corners where, due to my old Meade focuser, I had some
rather deep vignetting. So ignore the bright corners. I found I had no
darks from that time frame either. The camera has changed quite a bit
since then so using a modern dark put a few holes into the galaxy. I
probably should have scaled a 5 minute dark from that era but I didn't.
Some other time. Why these were taken at 6 minutes I don't know. I
know the single frame was an accident but why repeat it? That though
was taken at -5C while this was at -25C. I find scaling over that
temperature difference never works with this camera. It will have to do
until next year.

I see several faint fuzzies and one not so faint one. NED is still down
and SIMBAD seems not to know a thing about any of these guys, even the
bright one much to my amazement.

14" LX200R@f/10, L=5x6 min, RGB=3x6 each all binned 2x2, STL-11000M,
Paramount ME

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".