Good morning,
Last week I captured 12x 300s luminance frames of the interior of M31, centered on the variable star M31 V0619. I did get some good photometry out of the two best frames, but yesterday I thought that I might want to make an actual image out of all of the data.
I used tools that I was familiar with: AstroImageJ for calibration, alignment, and stacking, and StarTools for post-processing. (I have used APP but my license expired since I don't do that much AP now.)
My image came out very nicely except for dust donuts along the periphery of the image. I handed the data off to my friend who is an APP wizard. I've attached his image, minus denoising so you can clearly see the donuts.
We had a look at the 6 flat files provided at the Calibration link. These appear to be Sky Flats. The first two files used a 1-second exposure and the remaining four used a 2-second exposure. The mean of the histogram was well-below 32,000 ADU with the 1-second frames and around 49,000 ADU in the 2-second frames, but there was a lot of variability due to the sky brightness, I would assume.
The 2-second Flats showed many more donuts along the edges of the frame. That's a good thing in my estimation. The one thing that is most pronounced is the high degree of vignetting which would be expected with a 36x24mm sensor.
When I image here at home I take 30x flats. Could the problem I see with dust donuts be a combination of:
a. Too few flats.
b. Exposure too short.
Thanks,
Brian
PS: Also, I've noticed "banding" in Pier 12 images, even those published by others here. I find this very odd since banding is usually a problem with CMOS cameras.
Last week I captured 12x 300s luminance frames of the interior of M31, centered on the variable star M31 V0619. I did get some good photometry out of the two best frames, but yesterday I thought that I might want to make an actual image out of all of the data.
I used tools that I was familiar with: AstroImageJ for calibration, alignment, and stacking, and StarTools for post-processing. (I have used APP but my license expired since I don't do that much AP now.)
My image came out very nicely except for dust donuts along the periphery of the image. I handed the data off to my friend who is an APP wizard. I've attached his image, minus denoising so you can clearly see the donuts.
We had a look at the 6 flat files provided at the Calibration link. These appear to be Sky Flats. The first two files used a 1-second exposure and the remaining four used a 2-second exposure. The mean of the histogram was well-below 32,000 ADU with the 1-second frames and around 49,000 ADU in the 2-second frames, but there was a lot of variability due to the sky brightness, I would assume.
The 2-second Flats showed many more donuts along the edges of the frame. That's a good thing in my estimation. The one thing that is most pronounced is the high degree of vignetting which would be expected with a 36x24mm sensor.
When I image here at home I take 30x flats. Could the problem I see with dust donuts be a combination of:
a. Too few flats.
b. Exposure too short.
Thanks,
Brian
PS: Also, I've noticed "banding" in Pier 12 images, even those published by others here. I find this very odd since banding is usually a problem with CMOS cameras.
Yes Ray, I have been working on a solution for this issue. It seems that although calibrating the flats before calibrating the light does make a significant difference there is still noticeable banding left over in the lower signal frames.
In the mean time if you are running an older version photoshop there is an action by Noel Carboni in his 'Astronomy tools' that will deal with vertical and horizontal banding.
Hopefully we will get the sorted very soon.
regards
Peter
In the mean time if you are running an older version photoshop there is an action by Noel Carboni in his 'Astronomy tools' that will deal with vertical and horizontal banding.
Hopefully we will get the sorted very soon.
regards
Peter
Peter Shah - Collimation & Telescope servicing.
Visit my personal imaging website at astropix.co.uk
For Image Processing Tutorials
Contact: pete@ccdimaging.co.uk
We can supply your new high quality Newtonian or Dall Kirkham Astrograph
Visit my personal imaging website at astropix.co.uk
For Image Processing Tutorials
Contact: pete@ccdimaging.co.uk
We can supply your new high quality Newtonian or Dall Kirkham Astrograph
Peter Shah
Roboscopes Observatory Controller
This is 6x600s using the L filter. Processed with APP. I used the new bias frames and the latest flats (only the 2s frames). The donuts were removed and there is no sign of banding. I think with APP the bias frames are applied to the flats as a first step - which is what Peter was suggesting .
Anyway all this is moot now as Pier 12 looks like it is getting a new camera with 16803 sensor.
Dave
Anyway all this is moot now as Pier 12 looks like it is getting a new camera with 16803 sensor.
Dave
Looks great, Dave.
The KAI-11002 seems to favor long exposures. Last week I tried to do G2V Analysis on a magnitude 12.2 star using Pier 12. A 60-second exposure was needed to keep the star from saturating. The frames were utterly useless. Severe Venetian Blinds and gradients probably due to the 80% Moon meeting the Avoidance Parameters by a matter of arc-seconds. I did use the latest calibration frames but the results were terrible. I am happy to see that a new camera is being fitted but I am not very happy with the Moon Avoidance algorithm.
Brian
The KAI-11002 seems to favor long exposures. Last week I tried to do G2V Analysis on a magnitude 12.2 star using Pier 12. A 60-second exposure was needed to keep the star from saturating. The frames were utterly useless. Severe Venetian Blinds and gradients probably due to the 80% Moon meeting the Avoidance Parameters by a matter of arc-seconds. I did use the latest calibration frames but the results were terrible. I am happy to see that a new camera is being fitted but I am not very happy with the Moon Avoidance algorithm.
Brian
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Hi guys
I agree a replacement camera is the singularly best option. The banding issue is well known and only obvious as mentioned by Brian with short exposures or narrow band in low signal to noise areas of an image.
Very nice and smooth image Dave and I appreciate your taking the time and effort regarding this, fortunately to be no longer, issue.
Cheers
Ray
I agree a replacement camera is the singularly best option. The banding issue is well known and only obvious as mentioned by Brian with short exposures or narrow band in low signal to noise areas of an image.
Very nice and smooth image Dave and I appreciate your taking the time and effort regarding this, fortunately to be no longer, issue.
Cheers
Ray
Ray
Roboscopes Guinea Pig
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Hello Dave,
With regards to a mosaic of M31, from what I've seen of all your lunar mosaics, you'd do a really great job. I cannot recall offhand exactly what the replacement will be, but I think it will be a square format, hopefully requiring less panels to create the mega M31 image.
Hope you're keeping well, clear skies
Cheers,
Ray
With regards to a mosaic of M31, from what I've seen of all your lunar mosaics, you'd do a really great job. I cannot recall offhand exactly what the replacement will be, but I think it will be a square format, hopefully requiring less panels to create the mega M31 image.
Hope you're keeping well, clear skies
Cheers,
Ray
Ray
Roboscopes Guinea Pig
Ray
The lunar mosaics were all composited with Microsoft Image Composite Editor. I have only ever done one deep sky mosaic (M81 + M82 Luminance) but will be using the mosaic capability in APP. I will start off with 2 panels and see how it goes. My wallet is hoping that the new 16803 camera does provide a larger FOV.
Dave
The lunar mosaics were all composited with Microsoft Image Composite Editor. I have only ever done one deep sky mosaic (M81 + M82 Luminance) but will be using the mosaic capability in APP. I will start off with 2 panels and see how it goes. My wallet is hoping that the new 16803 camera does provide a larger FOV.
Dave
SSSSHHH Ray 
I have to get my money back for this mount somehow!!
http://astrograph.net/Planewave-L-500-Direct-Drive-Mount-includi-EQ-Wedge
I have to get my money back for this mount somehow!!
http://astrograph.net/Planewave-L-500-Direct-Drive-Mount-includi-EQ-Wedge
Please ignore my dylexia wherever possible, just be thankful I can control my Tourettes ;)
Things to do, so little time!
Steve
Roboscopes Tea Boy
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Dave'
I used ICE for the first time and it worked miracles, two huge panels, and I've yet to find a join. I think it may have been your mentioning it that I downloaded and tried it, so many thanks. If APP has it then so much the better for a multi panel I guess.
Regards, Ray
I used ICE for the first time and it worked miracles, two huge panels, and I've yet to find a join.
I think it may have been your mentioning it that I downloaded and tried it, so many thanks. If APP has it then so much the better for a multi panel I guess.Regards, Ray
Ray
Roboscopes Guinea Pig
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Hi Steve,
If you recall I did have a booking on it which I cancelled just in case the target disappeared below the horizon for several months before you got there. Really keen to use it and will place a booking very soon, as I'm sure many others will.
Hope that reassurance helps keep the blood pressure a bit lower, something we all need to think about as we get older.
Cheers,
The old man of the forum.
Postscript
Crikey just went to that link and saw the cost. Mind you Steve how much did Del boy want from you for his fire damaged one?
If you recall I did have a booking on it which I cancelled just in case the target disappeared below the horizon for several months before you got there. Really keen to use it and will place a booking very soon, as I'm sure many others will.
Hope that reassurance helps keep the blood pressure a bit lower, something we all need to think about as we get older.
Cheers,
The old man of the forum.
Postscript
Crikey just went to that link and saw the cost. Mind you Steve how much did Del boy want from you for his fire damaged one?
Ray
Roboscopes Guinea Pig
In APP when you load in the flats, bias, darks etc. The calibration is done automatically in the right order.
(I'm the forum moderator and co developer on it.
)
Good luck for those in Spain right now, stay safe and I hope the calibration data gets to be nice on 1 and 3 as well, anxious to take more data.
(I'm the forum moderator and co developer on it.
)Good luck for those in Spain right now, stay safe and I hope the calibration data gets to be nice on 1 and 3 as well, anxious to take more data.
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