ASTRO: Cassiopeia A

Rick's recent very impressive picture of the supernova remnant Cassiopeia A
showed me that this object can be imaged by amateurs. For some reason I
always thought it was reserved for the "pros".
I started with the Halpha filter, but the nebula was not visible in the raw
frames, so I changed to OIII. With the OIII filter the nebula was clearly
visible. I then added 5 minutes each for RGB to "soup up" the star colours a
bit.
OIII was taken over two night, unfortunately the second night had only good
seeing (in the first night it was perfect), so I lost some detail to gain a
smoother image.

There is a star to the left from the nebula itself that has the same teal
colour as the SN remnant in my image because it is only clearly visible in
the OIII channel. Actually it is quite bright in OIII, while it is just
visible in the Halpha images. None of the RGB exposures captured it. Maybe
it is not a star but a planetary nebula? On the other hand it looks red in
Rick's image, which makes it look rather unlikely that it is a PN.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount, SXV-H9
camera, 28x10 minutes for OIII, 4x10 minutes for Halpha, 5 minutes each at
3xbinning for RGB.

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

Stefan

Stefan Lilge wrote:
Rick's recent very impressive picture of the supernova remnant
Cassiopeia A showed me that this object can be imaged by amateurs. For
some reason I always thought it was reserved for the "pros".
I started with the Halpha filter, but the nebula was not visible in the
raw frames, so I changed to OIII. With the OIII filter the nebula was
clearly visible. I then added 5 minutes each for RGB to "soup up" the
star colours a bit.
OIII was taken over two night, unfortunately the second night had only
good seeing (in the first night it was perfect), so I lost some detail
to gain a smoother image.

There is a star to the left from the nebula itself that has the same
teal colour as the SN remnant in my image because it is only clearly
visible in the OIII channel. Actually it is quite bright in OIII, while
it is just visible in the Halpha images. None of the RGB exposures
captured it. Maybe it is not a star but a planetary nebula? On the other
hand it looks red in Rick's image, which makes it look rather unlikely
that it is a PN.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount,
SXV-H9 camera, 28x10 minutes for OIII, 4x10 minutes for Halpha, 5
minutes each at 3xbinning for RGB.

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

Stefan
------------------------------------------------------------------------


Interesting!!

I looked at the DSS plates at 23h 24m 05s +58d 48' 54". The object
shows clearly in red but is completely gone in blue yet obviously bright
in OIII. I checked both SIMBAD and NED and they show nothing within one
minute of that location. I checked my RGB images. Like the DSS it
shows no hint of it down to well below magnitude 20 in the blue image.
It does show in the green image but my software won't give me any
magnitude estimate other than it is below 20. It is just barely above
the noise level. On the red image it is magnitude 18.7, same with the
luminosity image. It is far brighter than that in your OIII image. My
FWHM is 2.6" (super good for me) which is in line with other stars in
the image. So it is below my resolution abilities.

Do you have software to determine the OIII magnitude?

I wonder if you might have discovered a planetary! Some are red in
LRGB. Something unusual is going on, that's for sure. It's obviously
not a false signal as the shape exactly matches the nearby stars.
Something sure is putting out a lot of OIII and some red though most of
it is OIII. Does it show in your HII? That might explain the the red
image. But it is really bright in OIII compared to the red or blue
images I took or that the DSS shows. That's not a star like any I know.

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".

I once had a star similar to that in an image and we took it for a carbon
star... but I had no OIII data to compare with. Mine did show nothing in
blue, a bit in green and a lot in red though.

--
Regards, Doug W.
www.photonsfate.com
"Rick Johnson" wrote in message
...


Stefan Lilge wrote:
Rick's recent very impressive picture of the supernova remnant Cassiopeia
A showed me that this object can be imaged by amateurs. For some reason I
always thought it was reserved for the "pros".
I started with the Halpha filter, but the nebula was not visible in the
raw frames, so I changed to OIII. With the OIII filter the nebula was
clearly visible. I then added 5 minutes each for RGB to "soup up" the
star colours a bit.
OIII was taken over two night, unfortunately the second night had only
good seeing (in the first night it was perfect), so I lost some detail to
gain a smoother image.

There is a star to the left from the nebula itself that has the same teal
colour as the SN remnant in my image because it is only clearly visible
in the OIII channel. Actually it is quite bright in OIII, while it is
just visible in the Halpha images. None of the RGB exposures captured it.
Maybe it is not a star but a planetary nebula? On the other hand it looks
red in Rick's image, which makes it look rather unlikely that it is a PN.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount,
SXV-H9 camera, 28x10 minutes for OIII, 4x10 minutes for Halpha, 5 minutes
each at 3xbinning for RGB.

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

Stefan
------------------------------------------------------------------------


Interesting!!

I looked at the DSS plates at 23h 24m 05s +58d 48' 54". The object shows
clearly in red but is completely gone in blue yet obviously bright in
OIII. I checked both SIMBAD and NED and they show nothing within one
minute of that location. I checked my RGB images. Like the DSS it shows
no hint of it down to well below magnitude 20 in the blue image. It does
show in the green image but my software won't give me any magnitude
estimate other than it is below 20. It is just barely above the noise
level. On the red image it is magnitude 18.7, same with the luminosity
image. It is far brighter than that in your OIII image. My FWHM is 2.6"
(super good for me) which is in line with other stars in the image. So it
is below my resolution abilities.

Do you have software to determine the OIII magnitude?

I wonder if you might have discovered a planetary! Some are red in LRGB.
Something unusual is going on, that's for sure. It's obviously not a
false signal as the shape exactly matches the nearby stars. Something sure
is putting out a lot of OIII and some red though most of it is OIII. Does
it show in your HII? That might explain the the red image. But it is
really bright in OIII compared to the red or blue images I took or that
the DSS shows. That's not a star like any I know.

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,

actually I am starting to think that the "strange" star is caused by my OIII
filter not rejecting IR light. It is the "visual" OIII filter from
Astronomik, which is not optimised for CCD. As it is for visual use there is
no need to block IR. The transmission curve can be seen at
http://www.astronomik.com/english/eng_oiii.html (the blue line).
The filter rejects wavelenghts longer than 520 nm, but the graph ends at
720nm, so I can't exclude the possibility that it opens up again at even
longer wavelengths. In this case it could simply be a star with a lot of IR
signal, which would match the red colour it has in your image.
All the other filters I used (Astronomik Ha and RGB) definately reject
IR-light, so that could explain why a star with a lot of IR signal is
brightest in the OIII filter.

Do you have software to determine the OIII magnitude?

No, but in the OIII image it is the same brightness as a mag 13.9 star
nearby.

Does it show in your HII? That might explain the the red image.

It is faintly visible in the Halpha image, but only at a small fraction of
the brightness ist has in the OIII image.

Did you use a "clear" filter for your luminance channel that cuts the IR? Or
is you luminance unfiltered?

If I find the time I may reimage this field with the OIII filter stacked
with an IR-block. And I might even try my IR-pass filter. If it is bright in
the IR-pass then I would definately know that the OIII leaks IR.

Stefan




Interesting!!

I looked at the DSS plates at 23h 24m 05s +58d 48' 54". The object shows
clearly in red but is completely gone in blue yet obviously bright in
OIII. I checked both SIMBAD and NED and they show nothing within one
minute of that location. I checked my RGB images. Like the DSS it shows
no hint of it down to well below magnitude 20 in the blue image. It does
show in the green image but my software won't give me any magnitude
estimate other than it is below 20. It is just barely above the noise
level. On the red image it is magnitude 18.7, same with the luminosity
image. It is far brighter than that in your OIII image. My FWHM is 2.6"
(super good for me) which is in line with other stars in the image. So it
is below my resolution abilities.

Do you have software to determine the OIII magnitude?

I wonder if you might have discovered a planetary! Some are red in LRGB.
Something unusual is going on, that's for sure. It's obviously not a
false signal as the shape exactly matches the nearby stars. Something sure
is putting out a lot of OIII and some red though most of it is OIII. Does
it show in your HII? That might explain the the red image. But it is
really bright in OIII compared to the red or blue images I took or that
the DSS shows. That's not a star like any I know.

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,

actually I am starting to think that the "strange" star is caused by my
OIII filter not rejecting IR light. It is the "visual" OIII filter from
Astronomik, which is not optimised for CCD. As it is for visual use
there is no need to block IR. The transmission curve can be seen at
http://www.astronomik.com/english/eng_oiii.html (the blue line).
The filter rejects wavelenghts longer than 520 nm, but the graph ends at
720nm, so I can't exclude the possibility that it opens up again at even
longer wavelengths. In this case it could simply be a star with a lot of
IR signal, which would match the red colour it has in your image.
All the other filters I used (Astronomik Ha and RGB) definately reject
IR-light, so that could explain why a star with a lot of IR signal is
brightest in the OIII filter.

Do you have software to determine the OIII magnitude?


No, but in the OIII image it is the same brightness as a mag 13.9 star
nearby.

Does it show in your HII? That might explain the the red image.


It is faintly visible in the Halpha image, but only at a small fraction
of the brightness ist has in the OIII image.

Did you use a "clear" filter for your luminance channel that cuts the
IR? Or is you luminance unfiltered?

Yes I did use an IR block filter for the Lum images. The filters came
with the camera (used) and I was told it was IR blocking. This may be
the proof it is! So you may be on to something. My old (bought when
they first came out) Lumicon OIII visual filter passes no H-alpha but a
friend who bought one a few months later has one that passes a ton of
H-alpha, enough to turn bright emission nebula from green in my filter
to pink in his. I figure that his definitely passes IR without much, if
any, loss. Don't know about mine, it may as well. I can't see those
frequencies -- darned eyes anyway!

Doug said he's seen this with RGB pattern with a carbon star and they do
have a ton of IR. Many peak down there in fact. You might try a short
shot of a known carbon star with the OIII and with the red filter to
see. V Aquila would make a quick 10 second test subject. It's always
been my favorite visual carbon star. To my eyes it is the reddest
though does fade some during part of its cycle.

I have a digital camera that doesn't block IR. It sees a TV IR remote's
LED's as a bright search light beam on the view screen. If you have
such a camera see if you see your remote's IR LED through the filter
with it. That would answer the question.

I use an IR beam that bounces off a mirror on the back of the telescope
as a safety interlock so I don't roll the roof with the scope up (it
saved me once already). Aiming it was a problem until I thought of that
camera. It shows the beam hitting the wall or scope just fine so made
aiming the beam very easy. Only problem is that the beam is modulated
as I used an off the shelf system. That's to keep false signals out.
But if I roll the roof by day the sun's IR swamps the detector so it
doesn't see the modulation, thinks the scope isn't there and stops the
roof partly open. I need to block the sun but its so bright any
reflection off anything that hits the detector causes the problem. I
even built a tube a foot long and a quarter inch wide center pointed at
the mirror. That did the trick but I kept hitting it and soon it was
history. So still looking for a solution. May put in an override that
works only when I'm in the observatory. Though at Hyde (poor mans
Kopernik) the founder rolled the roof with the C14 up while he was
watching. Said he had a brain fart. It hit the scope so hard it popped
a mounting bolt right out of the concrete and bent the other two but the
scope didn't even have a dent! Boy those are strong tubes -- heavy too.
It's an original C-14 ordered right after they hit the market about
1975. The OTA takes three to lift it. Far heavier than today's
version. I suppose that would have been toast.


If I find the time I may reimage this field with the OIII filter stacked
with an IR-block. And I might even try my IR-pass filter. If it is
bright in the IR-pass then I would definately know that the OIII leaks IR.

Have you done any imaging in IR with that filter? Don't recall you
posting anything. I've been tempted to try IR but this camera falls off
in IR. I'd need a better IR chip so haven't gone that route as yet.

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".

Have you done any imaging in IR with that filter? Don't recall you
posting anything. I've been tempted to try IR but this camera falls off
in IR. I'd need a better IR chip so haven't gone that route as yet.

Until now I have only used the IR-pass filter for Mars (hoping to tame the
seeing).
I will try it on some bright deep sky objects to see if I can get better
detail (because of less seeing effects in IR) than without. I'll probably
also do some nebula shots (like the Flame nebula or M42) to show some of the
stars that are hidden in the nebula.

Stefan

i took a shot at it last night with halpha and after 3.5 hours it was barely
visible.

it appears that the very faint halpha is offset from the o3 in stefan's
image

there may be a blob on the right side of my image but that may be a problem
with the flat field ....


"Stefan Lilge" wrote in message
...
Rick's recent very impressive picture of the supernova remnant Cassiopeia
A
showed me that this object can be imaged by amateurs. For some reason I
always thought it was reserved for the "pros".
I started with the Halpha filter, but the nebula was not visible in the
raw
frames, so I changed to OIII. With the OIII filter the nebula was clearly
visible. I then added 5 minutes each for RGB to "soup up" the star colours
a
bit.
OIII was taken over two night, unfortunately the second night had only
good
seeing (in the first night it was perfect), so I lost some detail to gain
a
smoother image.

There is a star to the left from the nebula itself that has the same teal
colour as the SN remnant in my image because it is only clearly visible in
the OIII channel. Actually it is quite bright in OIII, while it is just
visible in the Halpha images. None of the RGB exposures captured it. Maybe
it is not a star but a planetary nebula? On the other hand it looks red in
Rick's image, which makes it look rather unlikely that it is a PN.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount, SXV-H9
camera, 28x10 minutes for OIII, 4x10 minutes for Halpha, 5 minutes each at
3xbinning for RGB.

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

Stefan

by the way I do have a faint star in the same location as your green star in
your image

could be a planetary....

needs more investigation

"Richard Crisp" wrote in message
t...
i took a shot at it last night with halpha and after 3.5 hours it was
barely visible.

it appears that the very faint halpha is offset from the o3 in stefan's
image

there may be a blob on the right side of my image but that may be a
problem with the flat field ....


"Stefan Lilge" wrote in message
...
Rick's recent very impressive picture of the supernova remnant Cassiopeia
A
showed me that this object can be imaged by amateurs. For some reason I
always thought it was reserved for the "pros".
I started with the Halpha filter, but the nebula was not visible in the
raw
frames, so I changed to OIII. With the OIII filter the nebula was clearly
visible. I then added 5 minutes each for RGB to "soup up" the star
colours a
bit.
OIII was taken over two night, unfortunately the second night had only
good
seeing (in the first night it was perfect), so I lost some detail to gain
a
smoother image.

There is a star to the left from the nebula itself that has the same teal
colour as the SN remnant in my image because it is only clearly visible
in
the OIII channel. Actually it is quite bright in OIII, while it is just
visible in the Halpha images. None of the RGB exposures captured it.
Maybe
it is not a star but a planetary nebula? On the other hand it looks red
in
Rick's image, which makes it look rather unlikely that it is a PN.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount,
SXV-H9
camera, 28x10 minutes for OIII, 4x10 minutes for Halpha, 5 minutes each
at
3xbinning for RGB.

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

Stefan

My brain finally clicked into gear. Doug suggested it was a carbon star
as it is invisible in blue light, rare for a planetary. Also it is
nearly invisible in my green shot but obvious in the red, far brighter
than your H alpha image. Stefan said his OIII is a visual filter and
thus may not block IR light. After seeing your post by brain finally
clicked. Check the IR DSS image (attached). It's very bright in IR.
Carbon star is looking like the answer.

Since neither of you got much of the remnant in Halpha I wonder if the
red I got was "cool" nitrogen. Possibly sulfur but I lean toward
nitrogen as more likely in a SN blast. It's often the red in planetary
FLIERs

Rick


Richard Crisp wrote:

by the way I do have a faint star in the same location as your green star in
your image

could be a planetary....

needs more investigation

"Richard Crisp" wrote in message
t...

i took a shot at it last night with halpha and after 3.5 hours it was
barely visible.

it appears that the very faint halpha is offset from the o3 in stefan's
image

there may be a blob on the right side of my image but that may be a
problem with the flat field ....


"Stefan Lilge" wrote in message
...

Rick's recent very impressive picture of the supernova remnant Cassiopeia
A
showed me that this object can be imaged by amateurs. For some reason I
always thought it was reserved for the "pros".
I started with the Halpha filter, but the nebula was not visible in the
raw
frames, so I changed to OIII. With the OIII filter the nebula was clearly
visible. I then added 5 minutes each for RGB to "soup up" the star
colours a
bit.
OIII was taken over two night, unfortunately the second night had only
good
seeing (in the first night it was perfect), so I lost some detail to gain
a
smoother image.

There is a star to the left from the nebula itself that has the same teal
colour as the SN remnant in my image because it is only clearly visible
in
the OIII channel. Actually it is quite bright in OIII, while it is just
visible in the Halpha images. None of the RGB exposures captured it.
Maybe
it is not a star but a planetary nebula? On the other hand it looks red
in
Rick's image, which makes it look rather unlikely that it is a PN.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount,
SXV-H9
camera, 28x10 minutes for OIII, 4x10 minutes for Halpha, 5 minutes each
at
3xbinning for RGB.

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

Stefan

"Rick Johnson" wrote in message
...
My brain finally clicked into gear. Doug suggested it was a carbon star
as it is invisible in blue light, rare for a planetary. Also it is
nearly invisible in my green shot but obvious in the red, far brighter
than your H alpha image. Stefan said his OIII is a visual filter and
thus may not block IR light. After seeing your post by brain finally
clicked. Check the IR DSS image (attached). It's very bright in IR.
Carbon star is looking like the answer.

Since neither of you got much of the remnant in Halpha I wonder if the
red I got was "cool" nitrogen. Possibly sulfur but I lean toward
nitrogen as more likely in a SN blast. It's often the red in planetary
FLIERs

Rick

Stefan and Rick and others:
I asked the Deep Sky Hunters group on Yahoo about this and Matthias
Kronberger replied:

Hi Richard,

this is interesting ... I checked the POSS plates to see in which
colour bands the star is brighter and in which fainter;
interestingly, the stars turned out to be BRIGHTEST in IR, rather
faint on the DSS-I and DSS-II red - and INVISIBLE on all three blue
plates. Especially the blue DSS2 plate should've shown it since its
sensibility on the OIII line is in the range of 90% ! So (at least)
four possibilities remain:

- a new planetary
- a variable star
- the OIII filter has a large bandpass in the near-IR regime
- something even more enigmatic ... ?

are you intending to monitor this star during the next days ? And: do
you know if Stefan took all single-colour images during a single
night ?

----
and then he followed up with this:

Some more notes on the object:

coordinates (USNO B1.0):
23 24 04.87 +58 48 53.8

The object is indeed extremely red; the 2MASS catalogue gives a
colour index J-H = 1.7 ( which is unusually high ); the brightness in
Ks band is 6.8. The star has also a detection in the MSX6C Infrared
Point Source catalogue.

BR

----








Richard Crisp wrote:

by the way I do have a faint star in the same location as your green star
in
your image

could be a planetary....

needs more investigation

"Richard Crisp" wrote in message
t...

i took a shot at it last night with halpha and after 3.5 hours it was
barely visible.

it appears that the very faint halpha is offset from the o3 in stefan's
image

there may be a blob on the right side of my image but that may be a
problem with the flat field ....


"Stefan Lilge" wrote in message
r-online.net...

Rick's recent very impressive picture of the supernova remnant
Cassiopeia
A
showed me that this object can be imaged by amateurs. For some reason I
always thought it was reserved for the "pros".
I started with the Halpha filter, but the nebula was not visible in the
raw
frames, so I changed to OIII. With the OIII filter the nebula was
clearly
visible. I then added 5 minutes each for RGB to "soup up" the star
colours a
bit.
OIII was taken over two night, unfortunately the second night had only
good
seeing (in the first night it was perfect), so I lost some detail to
gain
a
smoother image.

There is a star to the left from the nebula itself that has the same
teal
colour as the SN remnant in my image because it is only clearly visible
in
the OIII channel. Actually it is quite bright in OIII, while it is just
visible in the Halpha images. None of the RGB exposures captured it.
Maybe
it is not a star but a planetary nebula? On the other hand it looks red
in
Rick's image, which makes it look rather unlikely that it is a PN.

Taken from the middle of Berlin with an 8" SCT at f/6.5, G11 mount,
SXV-H9
camera, 28x10 minutes for OIII, 4x10 minutes for Halpha, 5 minutes each
at
3xbinning for RGB.

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

Stefan