Horsehead and Flame Nebula
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Robert Chandler
Feb 18, 2021, 5:29:21 PM2/18/21
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Taking the opportunity to do some imaging tonight.
Attached is a screen grab of a continuing live stacking session currently 35 x 2 minute images, (flats, darks and bias included).
ASIAir Pro
Rasa 8
AZ EQ6 GT
ZWO ASI294MC Pro cooled camera
Guiding ZWO ASI120MM Nini
There is also a youtube video that I did for some friends - https://youtu.be/bQfTngMdqSs. I apologise for the sound quality and my lack of knowledge of my description of the Horsehead and Flame Nebulas. There is some star trailing possibly due to some gusts of wind. It will never be APOD material but I am happy with this.
Bob
William Bottaci
Feb 18, 2021, 7:39:07 PM2/18/21
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Very nice Bob. I'll comment better when I get to a computer. William
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William Bottaci
Feb 28, 2021, 9:47:55 AM2/28/21
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Hello Bob, a surprisingly good image from live stacking, though of
course it benefits from the calibration frames to remove noise and
there's not much noise visible here.
Obviously the mount shook for a while, and because it's only visible
on bright stars indicates that it wasn’t for long, so unlikely to be
wind gusts for instance, and the wind would not shake it so far. Could
it have been knocked?
Live stacking is excellent for instant results, very useful for outreach.
Have you since processed this in any way? Hoping you won't mind, I've
attached a quick simple processed version - just levels, brightness,
contrast, colour - a simplified standard fare, and I haven't done it
justice. For me I prefer your original up close and the simple
processed one when looking at it from further away, but particularly
the smoothness of yours.
I've said it before, to me processing often swaps one aspect of the
image for another; meaning that some aspects look better and other
others less so.
One thing I've come across recently, bias frames are not recommended
for CMOS sensors but good for CCD sensors. With CCD a bias frame can
perfectly well double as a dark-flat because the thermal noise built
up in very short flat exposures is insignificantly different from that
found in the bias. This isn't true for CMOS cameras. Bias signal may
not depend on temperature.
A dark-flat is the same as a flat (same exposure setting) but with the
lens covered.
When Deep Sky Stacker came out I think what the person had in mind was
CCD sensors.
There is some information here why this is (it's a good introduction):
https://nightskypix.com/calibration-frames/
and a diagram here:
http://deepskystacker.free.fr/english/theory.htm#CalibrationProcess
The explanation is quite simple, it's to do with what frame captures
what signal and noise. A bias frame captures ONLY the bias signal and
read noise. A dark frame captures bias signal, read noise AND dark
signal. In a word, there is duplication.
This image is a good indication of your equipment. Do you intend to
process this further, or leave that for future takes?
And many thanks for sharing. Also looking forward to your moon image, William
=Horesehead_IMG_0142_BobC_LCBCN.jpg (237K)=
On Thu, 18 Feb 2021 at 22:29, Robert Chandler <rob...@appendixb.co.uk> wrote:
Taking the opportunity to do some imaging tonight.
Attached is a screen grab of a continuing live stacking session
currently 35 x 2 minute images, (flats, darks and bias included).
ASIAir Pro
Rasa 8
AZ EQ6 GT
ZWO ASI294MC Pro cooled camera
Guiding ZWO ASI120MM Nini
There is also a youtube video that I did for some friends:
https://youtu.be/bQfTngMdqSs
course it benefits from the calibration frames to remove noise and
there's not much noise visible here.
Obviously the mount shook for a while, and because it's only visible
on bright stars indicates that it wasn’t for long, so unlikely to be
wind gusts for instance, and the wind would not shake it so far. Could
it have been knocked?
Live stacking is excellent for instant results, very useful for outreach.
Have you since processed this in any way? Hoping you won't mind, I've
attached a quick simple processed version - just levels, brightness,
contrast, colour - a simplified standard fare, and I haven't done it
justice. For me I prefer your original up close and the simple
processed one when looking at it from further away, but particularly
the smoothness of yours.
I've said it before, to me processing often swaps one aspect of the
image for another; meaning that some aspects look better and other
others less so.
One thing I've come across recently, bias frames are not recommended
for CMOS sensors but good for CCD sensors. With CCD a bias frame can
perfectly well double as a dark-flat because the thermal noise built
up in very short flat exposures is insignificantly different from that
found in the bias. This isn't true for CMOS cameras. Bias signal may
not depend on temperature.
A dark-flat is the same as a flat (same exposure setting) but with the
lens covered.
When Deep Sky Stacker came out I think what the person had in mind was
CCD sensors.
There is some information here why this is (it's a good introduction):
https://nightskypix.com/calibration-frames/
and a diagram here:
http://deepskystacker.free.fr/english/theory.htm#CalibrationProcess
The explanation is quite simple, it's to do with what frame captures
what signal and noise. A bias frame captures ONLY the bias signal and
read noise. A dark frame captures bias signal, read noise AND dark
signal. In a word, there is duplication.
This image is a good indication of your equipment. Do you intend to
process this further, or leave that for future takes?
And many thanks for sharing. Also looking forward to your moon image, William
=Horesehead_IMG_0142_BobC_LCBCN.jpg (237K)=
On Thu, 18 Feb 2021 at 22:29, Robert Chandler <rob...@appendixb.co.uk> wrote:
Taking the opportunity to do some imaging tonight.
Attached is a screen grab of a continuing live stacking session
currently 35 x 2 minute images, (flats, darks and bias included).
ASIAir Pro
Rasa 8
AZ EQ6 GT
ZWO ASI294MC Pro cooled camera
Guiding ZWO ASI120MM Nini
https://youtu.be/bQfTngMdqSs
Robert Chandler
Feb 28, 2021, 5:37:22 PM2/28/21
to croydo...@googlegroups.com
Hi William,
Thank you for the observations. I just assumed it was a gust of wind as I was inside and nowhere near the tripod at the time of imaging. Due to the temperature I mainly image remotely from the shed at the bottom of the garden.
I only do live stacking currently, although I have all the individual fit files. I haven't the time recently to process any of my targets but if you or anyone else would like me to share the data to process yourself (including calibration frames) please let me know.
I have two telescopes that I predominantly image from - the RASA 8 and the Skywatcher 120ED from a Bortle 6 back garden in Coulsdon. If anyone has any ideas for targets I would also be grateful.
Bob
Thank you for the observations. I just assumed it was a gust of wind as I was inside and nowhere near the tripod at the time of imaging. Due to the temperature I mainly image remotely from the shed at the bottom of the garden.
I only do live stacking currently, although I have all the individual fit files. I haven't the time recently to process any of my targets but if you or anyone else would like me to share the data to process yourself (including calibration frames) please let me know.
I have two telescopes that I predominantly image from - the RASA 8 and the Skywatcher 120ED from a Bortle 6 back garden in Coulsdon. If anyone has any ideas for targets I would also be grateful.
Bob
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Trev S
Mar 1, 2021, 6:40:11 AM3/1/21
to croydonastro
Hi Robert, I like the Horsehead nebula image. As William says, a bit of processing would really bring it out.
As far as the star movement goes, I once had a cat jump up at my scope while I was imaging causing a similar effect. It doesn't look like wind effect but lots of things can cause it. Just walking near the mount on a loose paving stone or wooden deck is another possible cause.
As a suggestion for targets, the Jellyfish Nebula (IC443) and the Monkeyhead Nebula (NGC2175) in Gemini are good bright targets and well placed at the moment.
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