ASTRO: NGC 4605 at f/10

I imaged NGC 4605 in March at f/7 and in April decided to revisit it at
f/10. Both times the moon was shining brightly, but NGC 4605 is bright
enough for decent signal even under bright skies.
I'm posting both the b/w and the colour version here.

Taken from the middle of Berlin with an 8" SCT at f/10, G11 mount, SXV-H9
camera, 22x5 minutes.

The picture can also be found at
http://ccd-astronomy.de/temp/4605-22x5F10gut.jpg
Colour version is at http://ccd-astronomy.de/temp/4605-22x5F10colourgut.jpg
The old f/7 version is at http://ccd-astronomy.de/temp/4605-43x3gut.jpg

Stefan

Stefan Lilge wrote:
I imaged NGC 4605 in March at f/7 and in April decided to revisit it at
f/10. Both times the moon was shining brightly, but NGC 4605 is bright
enough for decent signal even under bright skies.
I'm posting both the b/w and the colour version here.

Taken from the middle of Berlin with an 8" SCT at f/10, G11 mount,
SXV-H9 camera, 22x5 minutes.

The picture can also be found at
http://ccd-astronomy.de/temp/4605-22x5F10gut.jpg
Colour version is at http://ccd-astronomy.de/temp/4605-22x5F10colourgut.jpg
The old f/7 version is at http://ccd-astronomy.de/temp/4605-43x3gut.jpg

Stefan


Those came out well. What was the exposure time on the color data?

I can't seem to process images worth a darn when the moon is bright. I
have color gradients all over the place I can't deal with effectively.
Last night was clear too but I just continued my new T-Point map after
regreasing the mount and refining polar alignment. T-Point says I'm
now off 8" in altitude (high from the refracted pole) and 12" west in
azimuth. That changes slightly depending on nightly temperature and air
pressure changes so I doubt I can refine it further. Did try a 15
minute shot on the celestial equator at 1x1 binning, 0.51" per pixel and
saw no hint of guiding error even at 15 minutes! Except for long
exposure narrow band stuff I can forget the guider. I even tried it low
in the west on the equator to see how much problem refraction would be
and T-Point handled it, again, perfectly round stars at 15 minutes. I
started to see elongation if I blew up the shot to 300% when going 20
minutes however so 15' is my limit. Now if the dang moon will just get
out of the way.

Right now I'm fighting a shot I took in which high clouds fogged the red
images but didn't hurt the green and blue ones as they had moved out. I
hadn't realized that so didn't retake the red. Now I find if I get rid
of the red cast to the background the red is just too weak to show the
HII objects as pink. They come through blue green as seen by the eye!
If I turn up the red then everything gets a red cast. Since I took that
on a night of super seeing (best of the year so far) redoing it is
impossible. Similar to my moon processing problem. I've got a lot to
learn!

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 colour is 3x5 minutes per channel. Actually NGC 4605 is so bright
that even a single 5 minute shot for each colour would have been enough,
even with city lights and the moon.

Must be fun to have a mount that works that well. My G11 can't guide
reliably at f/10 (0,66"/pixel) even with an autoguider, unless the object is
at a high declination (NGC 4605 is at +61 degrees, no problems there).
Near the celestial equator I am restricted to imaging with the focal
reducer.

Stefan


"Rick Johnson" schrieb im Newsbeitrag
...


Stefan Lilge wrote:
I imaged NGC 4605 in March at f/7 and in April decided to revisit it at
f/10. Both times the moon was shining brightly, but NGC 4605 is bright
enough for decent signal even under bright skies.
I'm posting both the b/w and the colour version here.

Taken from the middle of Berlin with an 8" SCT at f/10, G11 mount, SXV-H9
camera, 22x5 minutes.

The picture can also be found at
http://ccd-astronomy.de/temp/4605-22x5F10gut.jpg
Colour version is at
http://ccd-astronomy.de/temp/4605-22x5F10colourgut.jpg
The old f/7 version is at http://ccd-astronomy.de/temp/4605-43x3gut.jpg

Stefan


Those came out well. What was the exposure time on the color data?

I can't seem to process images worth a darn when the moon is bright. I
have color gradients all over the place I can't deal with effectively.
Last night was clear too but I just continued my new T-Point map after
regreasing the mount and refining polar alignment. T-Point says I'm now
off 8" in altitude (high from the refracted pole) and 12" west in azimuth.
That changes slightly depending on nightly temperature and air pressure
changes so I doubt I can refine it further. Did try a 15 minute shot on
the celestial equator at 1x1 binning, 0.51" per pixel and saw no hint of
guiding error even at 15 minutes! Except for long exposure narrow band
stuff I can forget the guider. I even tried it low in the west on the
equator to see how much problem refraction would be and T-Point handled
it, again, perfectly round stars at 15 minutes. I started to see
elongation if I blew up the shot to 300% when going 20 minutes however so
15' is my limit. Now if the dang moon will just get out of the way.

Right now I'm fighting a shot I took in which high clouds fogged the red
images but didn't hurt the green and blue ones as they had moved out. I
hadn't realized that so didn't retake the red. Now I find if I get rid of
the red cast to the background the red is just too weak to show the HII
objects as pink. They come through blue green as seen by the eye! If I
turn up the red then everything gets a red cast. Since I took that on a
night of super seeing (best of the year so far) redoing it is impossible.
Similar to my moon processing problem. I've got a lot to learn!

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".