ASTRO: NGC 4631 color

With the very cold weather we had -- Temps approaching -40C/F I
developed a new problem, frost on the front of the optical window. The
STL-11000 has heaters that are supposed to prevent this. They draw
their energy from the Peltier heater. But if it isn't running very hard
they aren't either. If I cool the CCD much below -35C I start to get
blooming that makes the stars triangular. Keep the temp at -35C or
below and all is fine. Can't do that when that's the outside temp. To
regulate the temperature at all I need at least 5C difference so dropped
to -40C for taking images. That put frost around the edges of the CCD
window, especially across the guider chip. Had to change to the off
axis ST-7 for guiding. Then I have to severely crop the image to avoid
the frost areas. I've found that if I turn off the fan and wrap the
camera in insulation the heat from the electronics and those two heaters
do limit the frost to the outside edge enough that I can image in the
center of the chip. That is why this image is severely cropped. It was
the only frost free region. About all I can do is wait for warmer
weather now or reduce the sensitivity of the camera, that is supposed to
cure the bloom. Not sure I want to do that however.

Anyway the galaxy itself came out fine, just I lost a lot of other faint
fuzzies in the field.

I'm posting two versions, the color version processed "normally" -- at
least my version of normally. And a black and white version with the
levels pushed to bring out the faint tidal distortions caused by NGC
4656 (posted earlier) and NGC 4627 just above 4631 in this photo. NGC
4627 looks pretty normal in this shot but it sure isn't when you see the
pushed version.

14" LX200R@f/10, L=8x5' RGB 3x5' 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".

Hi Rick,

Have you tried baking the desiccant? That's supposed to clear up both
fogging and frosting problems.

--
Tandy W. Carter Jr.

http://home.att.net/~tandy.carter/


"Rick Johnson" wrote in message
...
With the very cold weather we had -- Temps approaching -40C/F I
developed a new problem, frost on the front of the optical window. The
STL-11000 has heaters that are supposed to prevent this. They draw
their energy from the Peltier heater. But if it isn't running very hard
they aren't either. If I cool the CCD much below -35C I start to get
blooming that makes the stars triangular. Keep the temp at -35C or
below and all is fine. Can't do that when that's the outside temp. To
regulate the temperature at all I need at least 5C difference so dropped
to -40C for taking images. That put frost around the edges of the CCD
window, especially across the guider chip. Had to change to the off
axis ST-7 for guiding. Then I have to severely crop the image to avoid
the frost areas. I've found that if I turn off the fan and wrap the
camera in insulation the heat from the electronics and those two heaters
do limit the frost to the outside edge enough that I can image in the
center of the chip. That is why this image is severely cropped. It was
the only frost free region. About all I can do is wait for warmer
weather now or reduce the sensitivity of the camera, that is supposed to
cure the bloom. Not sure I want to do that however.

Not the problem. That's for the inside of the glass. This frost is on
the outside, exposed to the air. The desiccant plug works on the sealed
inside of the glass. The inside is frost free. Normally the insulation
of the glass plus the exhaust heat of the Peltier cooler plus two
heaters for that purpose will keep the outside frost free but at the
extreme temps we were having that doesn't begin to provide enough heat.
Wrapping the camera in insulation helps reduce the problem. Since the
CCD blooms very strongly much below -35C I can't run the temp down to
say -65 C which would run the cooler hard and provide a lot of excess
heat for the front of the glass without the blooming getting very bad.
I can reduce the CCD sensitivity at the expense of longer exposures but
that means taking the power supply apart in the camera to get at the pot
I need to adjust. Then putting it back in trying it, then repeating
until I get it "right". I'm not comfortable with that route. Nor with
the loss of quantum efficiency that would cause.

Now that the winter temperatures are above -30C the problem should go
away. Then the heater runs hard enough to provide the warmth needed to
keep the outside of the glass frost free with a wrapped camera body.

SBIG has a third heater that can be added (think it has to be returned
to the factory). I don't know if the camera has had that modification
made or not. I bought it used from a guy who also bought it used. I've
got an email into SBIG to find out if that has been done. If not I'll
have to bite the bullet and give up imaging for a while and send it back
to them for the additional heater. But those only run when the cooler
is running and at the level of the cooler so might not even help much
when the cooler is barely needed.

I still have a few highly frosted images to try and salvage.

Rick


Tandy W. Carter Jr. wrote:

Hi Rick,

Have you tried baking the desiccant? That's supposed to clear up both
fogging and frosting problems.


--
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,

that's a very detailed and beautiful image. At least the chip of the ST11K
is large enough to allow for quite a lot of cropping.
-40 C degrees? The coldest temperature I can remember here in Germany was
around -20 C. The "worst" we had this winter was in the region of -5 C and
today we almost had +10 degrees. Winter doesn't seem to happen this year, we
are going straight from autumn to spring. Not that I miss winter that much,
but it does feel a bit strange...

Stefan


"Rick Johnson" schrieb im Newsbeitrag
...
With the very cold weather we had -- Temps approaching -40C/F I
developed a new problem, frost on the front of the optical window. The
STL-11000 has heaters that are supposed to prevent this. They draw
their energy from the Peltier heater. But if it isn't running very hard
they aren't either. If I cool the CCD much below -35C I start to get
blooming that makes the stars triangular. Keep the temp at -35C or
below and all is fine. Can't do that when that's the outside temp. To
regulate the temperature at all I need at least 5C difference so dropped
to -40C for taking images. That put frost around the edges of the CCD
window, especially across the guider chip. Had to change to the off
axis ST-7 for guiding. Then I have to severely crop the image to avoid
the frost areas. I've found that if I turn off the fan and wrap the
camera in insulation the heat from the electronics and those two heaters
do limit the frost to the outside edge enough that I can image in the
center of the chip. That is why this image is severely cropped. It was
the only frost free region. About all I can do is wait for warmer
weather now or reduce the sensitivity of the camera, that is supposed to
cure the bloom. Not sure I want to do that however.

Anyway the galaxy itself came out fine, just I lost a lot of other faint
fuzzies in the field.

I'm posting two versions, the color version processed "normally" -- at
least my version of normally. And a black and white version with the
levels pushed to bring out the faint tidal distortions caused by NGC
4656 (posted earlier) and NGC 4627 just above 4631 in this photo. NGC
4627 looks pretty normal in this shot but it sure isn't when you see the
pushed version.

14" LX200R@f/10, L=8x5' RGB 3x5' 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,
SBIG reports my camera doesn't even have the two standard heaters so
it's no wonder I'm having trouble. It's two years older than when they
started making them with the heaters. It's a free upgrade but I'll be
without a camera for a while. Think I'll try and survive until summer
when we hit the road for a few weeks and send it in then.

We've had no snow this year which is really bad. Means a nasty fire
season this spring and lots of wild life that depends on snow cover to
survive the cold likely didn't make it. Normally there's nearly a meter
on the ground but this year it isn't 6 cm deep! Cold isn't that much of
a problem if you are prepared but every year someone isn't and pays with
their life. Septic systems also use the snow cover to remain unfrozen
so the steamers are making a fortune thawing out systems. I put in an
insulated system so no problem but older systems didn't have that option
and are freezing up. Thaw has hit, it's above freezing two days in a
row, and cloudy for 5 with many more forecast.

Rick


Stefan Lilge wrote:
Rick,

that's a very detailed and beautiful image. At least the chip of the
ST11K is large enough to allow for quite a lot of cropping.
-40 C degrees? The coldest temperature I can remember here in Germany
was around -20 C. The "worst" we had this winter was in the region of -5
C and today we almost had +10 degrees. Winter doesn't seem to happen
this year, we are going straight from autumn to spring. Not that I miss
winter that much, but it does feel a bit strange...

Stefan


"Rick Johnson" schrieb im Newsbeitrag
...

With the very cold weather we had -- Temps approaching -40C/F I
developed a new problem, frost on the front of the optical window. The
STL-11000 has heaters that are supposed to prevent this. They draw
their energy from the Peltier heater. But if it isn't running very hard
they aren't either. If I cool the CCD much below -35C I start to get
blooming that makes the stars triangular. Keep the temp at -35C or
below and all is fine. Can't do that when that's the outside temp. To
regulate the temperature at all I need at least 5C difference so dropped
to -40C for taking images. That put frost around the edges of the CCD
window, especially across the guider chip. Had to change to the off
axis ST-7 for guiding. Then I have to severely crop the image to avoid
the frost areas. I've found that if I turn off the fan and wrap the
camera in insulation the heat from the electronics and those two heaters
do limit the frost to the outside edge enough that I can image in the
center of the chip. That is why this image is severely cropped. It was
the only frost free region. About all I can do is wait for warmer
weather now or reduce the sensitivity of the camera, that is supposed to
cure the bloom. Not sure I want to do that however.

Anyway the galaxy itself came out fine, just I lost a lot of other faint
fuzzies in the field.

I'm posting two versions, the color version processed "normally" -- at
least my version of normally. And a black and white version with the
levels pushed to bring out the faint tidal distortions caused by NGC
4656 (posted earlier) and NGC 4627 just above 4631 in this photo. NGC
4627 looks pretty normal in this shot but it sure isn't when you see the
pushed version.

14" LX200R@f/10, L=8x5' RGB 3x5' 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".

wow.



Rick Johnson wrote:

With the very cold weather we had -- Temps approaching -40C/F I
developed a new problem, frost on the front of the optical window. The
STL-11000 has heaters that are supposed to prevent this. They draw
their energy from the Peltier heater. But if it isn't running very hard
they aren't either. If I cool the CCD much below -35C I start to get
blooming that makes the stars triangular. Keep the temp at -35C or
below and all is fine. Can't do that when that's the outside temp. To
regulate the temperature at all I need at least 5C difference so dropped
to -40C for taking images. That put frost around the edges of the CCD
window, especially across the guider chip. Had to change to the off
axis ST-7 for guiding. Then I have to severely crop the image to avoid
the frost areas. I've found that if I turn off the fan and wrap the
camera in insulation the heat from the electronics and those two heaters
do limit the frost to the outside edge enough that I can image in the
center of the chip. That is why this image is severely cropped. It was
the only frost free region. About all I can do is wait for warmer
weather now or reduce the sensitivity of the camera, that is supposed to
cure the bloom. Not sure I want to do that however.

Anyway the galaxy itself came out fine, just I lost a lot of other faint
fuzzies in the field.

I'm posting two versions, the color version processed "normally" -- at
least my version of normally. And a black and white version with the
levels pushed to bring out the faint tidal distortions caused by NGC
4656 (posted earlier) and NGC 4627 just above 4631 in this photo. NGC
4627 looks pretty normal in this shot but it sure isn't when you see the
pushed version.

14" LX200R@f/10, L=8x5' RGB 3x5' 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".

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