As the curse of all deep sky imagers is approaching (full moon), this is typically the time of the month I plan future deep sky acquisitions instead of collecting data (no point wasting my time in obtaining crap data). So during this period, I thought I’d share some data I acquired a while back for a stellar processing challenge. At the time, I could not think of a better challenge than a wide field version of the open cluster M7.
So, I have provided two versions of the R, G, B files (small and large).
The small is a crop of the cluster (16-bit TIFF files - around 5.2Mb in size each) and can be downloaded here;
The large is the STL11k full frame FIT files which are 42Mb in size. I’ve kept the data in FITs IEEE float format as some stars are greater than 65k pixel values (I think the R channel has a few 77k value stars). Providing the 16-bit FIT files would have possibly dropped the file size, but I'm not certain of your image processing routines so feel its best to give you the maximum dynamic range possible.
All frames are reduced (dark, flat, bias), registered and are a combine of 5x5min subs per colour channel (25min). They are ready for your processing pleasure. I would recommend a starting colour ratio of R:1.5,G:1.0,B:1.5 if you want to get close to the correct colour balance.
I have no intentions to use this data for anything else. I was simply going to trash it. Put bluntly, it’s not the best data I’ve acquired. Stars aren’t perfectly round. Those who process the full frame fit files will see stars in the top left corner have elongated and you’ve got a reasonable gradient to deal with. I did say it was a challenge! What? You wanted magnificent data present to you on a silver platter? If it was that good, I wouldn’t be giving it away so easily.
So, don’t be shy – have a go. There are no rules, just have fun and post your results and some info on what you did so we can check’em out.
Below you’ll find my first cut of the star field. These are low res because of the IIS upload limit. If you want to see a higher-res full frame version, you can click here (3.1Mb).
Last edited by jase; 27-07-2007 at 05:30 PM.
Reason: typos
Here is an initial try.
Digital Development of fits files
Pixel math green x 0.66
Richardson Lucy on each colour fit 3X3 for ten cycles
Recombine with IP to colour tiff
Adjust in PS for levels and crop to get rid of black bits
Convert 16 bit tiff to LDR image with EasyHDR
Adjust levels in PS
Another cycle of RL as before
Convert to JPG 3.6MB
All frames are reduced (dark, flat, bias), registered and are a combine of 5x5min subs per colour channel (25min). They are ready for your processing pleasure. I would recommend a starting colour ratio of R:1.5,G:1.0,B:1.5 if you want to get close to the correct colour balance.
So, don’t be shy – have a go. There are no rules, just have fun and post your results and some info on what you did so we can check’em out.
Nice image Jase!
OK, I'll give it a go - I need the practice! Besides, not much else to do this Sunday arvo.
The following shows the same cropped area in your and my version. Stars are a bit smaller, but I dropped some colour depth. I didn't try to increase the star sizes in the cluster - that might make the image more appealing. I highlighted the darker areas a bit 'cause I like that.
Thanks Bill, Mike and Dr. Nick – though my intentions were not to display this image as a master piece, but I’ll acknowledge your compliments anyway.
Quote:
Originally Posted by avandonk
Here is an initial try.
Digital Development of fits files
Pixel math green x 0.66
Richardson Lucy on each colour fit 3X3 for ten cycles
Recombine with IP to colour tiff
Adjust in PS for levels and crop to get rid of black bits
Convert 16 bit tiff to LDR image with EasyHDR
Adjust levels in PS
Another cycle of RL as before
Convert to JPG 3.6MB
Thanks Jase I will keep playing with the data.
Bert
Good stuff Bert. I find it interesting how you individually worked on each channel before combining them. I typically find it easier to combine the data before manipulating it primarily because if a routine changes the brightness of a channel more than the other channels, you’ve lost your colour weightings (sure you can get them back, but it easier to prevent).
Why did you increase the pixel values on the green channel with pixel math? The KAI-11000 chip is rather green sensitive so you it needs to be compensated by boosting up the other channel weights. Was this specifically done to provide more information for the deconvolution process?
How did you find the LDR process working with 16-bit data? In your opinion, are there greater benefits over 12-bit for this process considering the increase in dynamic range? The star centers aren’t white, but a subtle pink hue, was this caused by LDR process or incorrect colour weightings do you think?
Quote:
Originally Posted by ballaratdragons
Jase, here is the best I could get it. It was hard converting them from Black & White to colour before I added them together!
Not real good is it
Ken, your colours are nearly non-existent. What happened? If you want the quick and dirty way of doing things and you’re only using photoshop, open up the R channel, the convert the image to RGB. Then select the channels tab. Copy and paste the G, B images in to the G, B channels. This is a rather crude and nasty way of doing things (in my opinion) as it not always easy to get colour balance right. It’s all experience mate. Have a couple more goes if you’re having fun.
Quote:
Originally Posted by marc4darkskies
Nice image Jase!
OK, I'll give it a go - I need the practice! Besides, not much else to do this Sunday arvo.
The following shows the same cropped area in your and my version. Stars are a bit smaller, but I dropped some colour depth. I didn't try to increase the star sizes in the cluster - that might make the image more appealing. I highlighted the darker areas a bit 'cause I like that.
OK, I enlarged the stars in the cluster to make them stand out more. I just did a quick & dirty - not knowing which stars belong to M7, I may have selected too many. http://www.pbase.com/gailmarc/temp
But it IS fun! Hey!! Maybe some artificial diffraction spikes next??!!
Ken, your colours are nearly non-existent. What happened? If you want the quick and dirty way of doing things and you’re only using photoshop, open up the R channel, the convert the image to RGB. Then select the channels tab. Copy and paste the G, B images in to the G, B channels. This is a rather crude and nasty way of doing things (in my opinion) as it not always easy to get colour balance right. It’s all experience mate. Have a couple more goes if you’re having fun.
Jase, I don't understand what you just said. I take it you are speaking in Computer talk (R Channels, Channel Tabs etc)
It took me just on Two hours of frigging around to get them from Mono to colour and I almost gave up, until I tried using PS Actions.
I found that I could convert them one at a time by using 'Fake H-Alpha' for the Red, 'Fake OIII' for the green, and I forget the one I used for Blue.
Then I tried to layer them. I've never been able to work out how to do layers, and I still couldn't. I spent Four and a half hours working thru the tutorial and trying it as I read!!!! It still didn't work properly
In other words, I wasted a total of 8.5 hours to get my mess
This is the Main reason I don't want a Monochrome camera.
OK, I enlarged the stars in the cluster to make them stand out more. I just did a quick & dirty - not knowing which stars belong to M7, I may have selected too many. http://www.pbase.com/gailmarc/temp
Not too sure about the enlarged stars Marcus. This may work if you stopped the white clipping with specific curve before enlargement. Look like you being to look some colours associated with them as well. None the less, interesting way of processing a cluster. Wouldn't have thought to enlarge the stars only because if there is something else in the frame, things may not be proportioned as such. I guess with a cluster only frame it doesn't make much difference.
Quote:
Originally Posted by ballaratdragons
Jase, I don't understand what you just said. I take it you are speaking in Computer talk (R Channels, Channel Tabs etc)
It took me just on Two hours of frigging around to get them from Mono to colour and I almost gave up, until I tried using PS Actions.
I found that I could convert them one at a time by using 'Fake H-Alpha' for the Red, 'Fake OIII' for the green, and I forget the one I used for Blue.
Then I tried to layer them. I've never been able to work out how to do layers, and I still couldn't. I spent Four and a half hours working thru the tutorial and trying it as I read!!!! It still didn't work properly
In other words, I wasted a total of 8.5 hours to get my mess
This is the Main reason I don't want a Monochrome camera.
In images Plus
Digital Development of fits files as before
Pixel math green x 0.66 (same as mult R&B by 1.5) without blowing out either.
Convert each R,G&B Fits to three corresponding R,G&B Tiffs
In RegiStar
Align R,G&B Tiffs with RegiStar and simply sum.
Save as 16bit Tiff
In Photo Shop
Resultant colour tiff levels adjusted in PS
GradientXterminator used settings Coarse and Low
Levels adjusted again in PS
In Images Plus
Richardson Lucy for ten cycles 5x5
It is really important to carefully choose lower and upper levels when using RL enhancement otherwise you can enhance noise and introduce unwanted artefacts into the brighter stars.
Convert to JPG 90%
I think Registar does a better job of aligning images than any other method.
I could be imagining it but the faint backgroud stars are clearer.
GradientXterminator seems to have got rid of the gradient which often plagues wide fields.
Thanks again to Jase for letting us play with his data.
Nice work Bert. When blinking your original and the latest, the stars might be a little sharper, but not by much. Certainly nothing really obvious. The colours look quite muted, but still looks good. Pleased you're making the most of the data and enjoying it in the process.
Hi Barb,
This is great. Really like the effort you've put in to bring out the colours. I enjoyed your second image more than the first. Vertical or horizontal flipping the image can add an extra twist. Keep at it.
I would recommend a starting colour ratio of R:1.5,G:1.0,B:1.5 if you want to get close to the correct colour balance.
There are no rules, just have fun and post your results and some info on what you did so we can check’em out.
There is not right or wrong - just have fun.
Hey!! Maybe some artificial diffraction spikes next??!! 
