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M31 processing


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I've been imaging our neighbor a few nights, so roughly 7 hours of integration time with my setup under fairly high LP. I'm somewhat pleased with it, but I'm missing colour completely. I'm sure the Astronomik clip-on filter is shaving a lot of it away, but my inferior post processing skills must also have something to say.

Here is the stacked picture, consisting mostly of 600s ISO 400 subs: https://www.dropbox.com/s/9va9dqovppryugj/M31 - second stack.TIF?dl=0

Here is what I managed to do with it. StarTools and then just a a tiny colour curve correction in GIMP2:

M31_-_Second_stack_-_first_process_gimped.thumb.jpg.8ee91f2df71a106e8e05a8e08ccdaabd.jpg

If anyone can give me pointers to how I can improve this, I'd be grateful.

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Hi Datalord. I tried but struggled with your data to get anything reasonable from it. I wonder should you have used a higher iso. When i was using a canon dslr i used 800-1600 iso and got decent results. The other thing that might be an issue is the astronomik filter. People tend to complain about colour issues with it. Anyway this was all i could get out of it using PS levels, gradient exterminator. Your image above looks like you clipped the blacks.

Richard.

5980cf73d161a_M31-secondstack.thumb.jpg.3d041013d3c8f2139845c8d76fbdddf5.jpg

 

 

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2 hours ago, Allinthehead said:

Also can you explain the above? Did you stack different sub lenghts/iso?

I had some 2 min, 5 min, but mostly 10 min subs. 

Your process does look a lot better. I did clip the black, just because of the black being a lot less than actual black, which might have been a mistake. 

I think, next night I have I'll try to image without the filter and see what result it yields. 

Thank you! 

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Try upping the iso to 800 and only stack sub lengths of the same duration. How bad is the lp as this may be the reason the data is poor. 7 hrs should get a good result. You may also find reducing your exposure times on a target as bright as andromeda might help. Also my advice comes with the caveat that most of my imaging is done with a mono camera so my experience with dslr's is fairly limited.

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I don't use startools, I use photoshop, so I don't suppose my processes will be of much use, but I upped the colour intermittently using Match colour, did one iteration of gradient exterminator and tried to deal with the horizontal colour banding in Actions, but I don't think it worked.   Datalord, do you download to the laptop?  If so, do you have the SD card in the camera?  If so, try removing it,  it seems to significantly reduce the horizontal banding without the SD card.  

I think 600secs at 400iso or 300secs at 800 iso is about right, I would not do 600secs at 800 iso I think it might make it too noisy.

c987bb7f6d7a839be5faac739b73c038.1824x0_

 

 

 

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1 hour ago, carastro said:

I don't use startools, I use photoshop, so I don't suppose my processes will be of much use, but I upped the colour intermittently using Match colour, did one iteration of gradient exterminator and tried to deal with the horizontal colour banding in Actions, but I don't think it worked.   Datalord, do you download to the laptop?  If so, do you have the SD card in the camera?  If so, try removing it,  it seems to significantly reduce the horizontal banding without the SD card.  

I think 600secs at 400iso or 300secs at 800 iso is about right, I would not do 600secs at 800 iso I think it might make it too noisy.

c987bb7f6d7a839be5faac739b73c038.1824x0_

 

 

 

Also a very nice result. Looks like I should learn to use PS instead. 

I do use an SD card and I save to both laptop and card. I had no idea it could affect image quality, that seems crazy to me, but... Gremlins. 

Regarding iso, I actually considered doing iso 100 after hearing someone saying that higher iso conceals colour. Also,  and this makes sense to me, iso should not actually change anything, because we stack the frames and then stretch them post stack. So regardless of iso, I should end with the same result, as long as I don't hit the well depth of the pixels.  Is that off? 

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Hi Datalord.

I've been following your topic because I have also been imaging M31 of late (when lack of clouds permit) in an attempt to learn LRGB processing with my new Atik 428ex and Baader filters - I've been throwing in some Ha as well just to see what effect it has.

That aside, M31 was the first dso I imaged when I started last November using an out-of-the-box Canon 70D and shooting 5 images at every ISO between 100 and 1600 each for 60s. I really didn't know what I was doing! I took an 'appropriate number' (I had no idea what was appropriate mind you) of darks, flats and bias frames, threw then all into DSS together into the Main Group and then processed the resulting autosave.tif in PI (trial at the time) and PS - and this was the end result! At the time I was quite pleased. All very unscientific and I have no idea which ISO contributed what in terms of colour.

59818ae3db52d_M31_integration_ABEps.thumb.jpg.44996a2991becdbef63cb337aa2bb006.jpg

This was taken 'unguided' as at this stage as I hadn't bought a guide camera or introduced myself to PHD2 - I just spent half the night doing a polar alignment and hoped the NEQ-6 would do the rest. I was pleasantly surprised I even got it in the frame!

This probably doesn't help other than to show what you can get when you have no idea what you are doing regarding ISO or exposure time.

Adrian

SW ED80 DS-Pro + F/R + Canon 70D + NEQ6

BackyardEoS + CdC + PI + PS

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Quote

I do use an SD card and I save to both laptop and card. I had no idea it could affect image quality, that seems crazy to me, but... Gremlins. 

Yes it does sound crazy, but some-one suggested it on another forum, so I tried it and it did seem to make a difference. Some-one else explained it in more technical terms which I can't quite remember and never understood anyway, but it's something to do with the downloading to laptop when an SD card is in place.   I'll see if I can find the thread and copy the quotes. 

Well it doesn't do any harm to try it out because as you get more advanced you will be wanting to stretch your images more and the horizontal banding can spoil your images.

HTH

Carole 

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OK this is the original post in 2012.

Quote

 I have had a lot of issues with ny Canon 30D where with long exposures I get horizontallines. These are beyond just gradient and appear no matter what I was imaging and irrespective of moon etc.

So i whipped out the memory card..no more issues.

Can only assume there is stuff happening in between the physical process of writing an image to the card and pushing it through to the PC. Somewhere, electrical charge is being introduced into the image file

This is one of the explanations:

Quote

The banding happens because the camera is trying to capture to the card and the outside device at the same time and the onboard processor just isn't up to it.

I have also heard that it might depend on the quality of your SD card. 

HTHs.

Carole 

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3 hours ago, Adreneline said:

Hi Datalord.

I've been following your topic because I have also been imaging M31 of late (when lack of clouds permit) in an attempt to learn LRGB processing with my new Atik 428ex and Baader filters - I've been throwing in some Ha as well just to see what effect it has.

That aside, M31 was the first dso I imaged when I started last November using an out-of-the-box Canon 70D and shooting 5 images at every ISO between 100 and 1600 each for 60s. I really didn't know what I was doing! I took an 'appropriate number' (I had no idea what was appropriate mind you) of darks, flats and bias frames, threw then all into DSS together into the Main Group and then processed the resulting autosave.tif in PI (trial at the time) and PS - and this was the end result! At the time I was quite pleased. All very unscientific and I have no idea which ISO contributed what in terms of colour.

 

Very nice. What were your skies like in terms of light pollution? And I assume you didn't use an LP filter?

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Hi. From what I can remember the LP was quite low - M31 was pretty much straight overhead by the time I'd spent far too much time getting a decent PA. I didn't use any filters at all - the 70D was attached directly to the R/F which was screwed onto the ED80 drawtube. At the time I used PI to do a DBE and then used PS to process the image.

I now use an IDAS UV/IR cut filter when I use the 70D and as far as I can tell that has helped to improve the focus - I've not noticed it has affected the colour content. I now use PI for all the post-processing as overall I find it far easier to get consistent results than using PS. I am still happy to use DSS; in most cases I find it hard to tell the difference between using DSS and PI to calibrate, register and stack (pretty much as per the LightVortex article on comparing DSS and PI).

Hope this helps - good luck!

Adrian

P.S. For what it is worth the SD card would have been in the 70D at the time even though I was downloading both RAW and JPG images to the PC (an Intel NUC).

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On 2017-08-01 at 17:11, Datalord said:

I've been imaging our neighbor a few nights, so roughly 7 hours of integration time with my setup under fairly high LP. I'm somewhat pleased with it, but I'm missing colour completely. I'm sure the Astronomik clip-on filter is shaving a lot of it away, but my inferior post processing skills must also have something to say.

Here is the stacked picture, consisting mostly of 600s ISO 400 subs: https://www.dropbox.com/s/9va9dqovppryugj/M31 - second stack.TIF?dl=0

Here is what I managed to do with it. StarTools and then just a a tiny colour curve correction in GIMP2:

M31_-_Second_stack_-_first_process_gimped.thumb.jpg.8ee91f2df71a106e8e05a8e08ccdaabd.jpg

If anyone can give me pointers to how I can improve this, I'd be grateful.

If this is your filter

http://www.astronomik.com/en/filter-gegen-lichtverschmtzung-filters-against-lightpollution-lpr/astronomik-cls-filter.html 

than I can understand your colour problem. This is the filter transmission spectrum:

astronomik_cls_trans.png

The filter blocks most of the yellow/red signal, leaving only blue and some green.

Compare this to the Baader filter:

Spektralkurve des Mond & Skyglowfilter

The Baader filter clips only light from common pollution sources, such as sodium and mercury lamps.

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The graph is at it's maximum again for Ha (656 nm), but the sensor's QE curve is on it's way down. This means that for targets that emit Ha, you'll get red. But for targets without (much) Ha, a lot of red and yellow is suppressed. The original image was of M31, which has mostly 'rgb', and only very little Ha.

It also depends on the type of modification that was done on the camera, and even the type of camera. My unmodded Pentax K20d picks up slightly more Ha than most unmodded Canons. And depending on what was used to replace the original IR blocking filter (= type of modification), you'll also get different results. The graph I have in my previous post only shows the difference in response between an Astronomik CLS and a Baader Neodymium filter. Both manufacturers have various types of filter, and I'm not even sure which exact type the op has. That's why I wrote "If this is your filter"

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17 hours ago, wimvb said:

If this is your filter

http://www.astronomik.com/en/filter-gegen-lichtverschmtzung-filters-against-lightpollution-lpr/astronomik-cls-filter.html 

than I can understand your colour problem. This is the filter transmission spectrum:

astronomik_cls_trans.png

The filter blocks most of the yellow/red signal, leaving only blue and some green.

Compare this to the Baader filter:

Spektralkurve des Mond & Skyglowfilter

The Baader filter clips only light from common pollution sources, such as sodium and mercury lamps.

Hi Wim,

I had the same problem (lack of colour on M31) with the Astronomic UHC filter. Would the filters spectrum predict the same?

Thanks, Tim.

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1 hour ago, StargeezerTim said:

Hi Wim,

I had the same problem (lack of colour on M31) with the Astronomic UHC filter. Would the filters spectrum predict the same?

Thanks, Tim.

This one?

http://www.astronomik.com/en/visual-filters/uhc-filter.html

Even more so. According to the transmission graph, only cyan (between green and blue) light, as well as deep red light (Ha, towards the ir) is let through. But beyond Ha wavelength, the camera sensor has poor response (QE), so that light isn't detected anyway. This filter is as if you're shooting narrowband (Ha, Oiii, Sii) in one shot colour. And it is intended as such: to make emission nebulae and pn's stand out against a dark background. It efficiently blocks out any light except that emitted by nebulae. The Astronomik uhc filter simply was not designed for galaxy imaging. It isn't a general purpose light pollution filter, which, imo, should block light from artificial light sources, such as sodium and mercury lights.

With this filter, you can probably get great results on M27 but not on M31, from a light polluted area.

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4 minutes ago, wimvb said:

This one?

http://www.astronomik.com/en/visual-filters/uhc-filter.html

Even more so. According to the transmission graph, only cyan (between green and blue) light, as well as deep red light (Ha, towards the ir) is let through. But beyond Ha wavelength, the camera sensor has poor response (QE), so that light isn't detected anyway. This filter is as if you're shooting narrowband (Ha, Oiii, Sii) in one shot colour. And it is intended as such: to make emission nebulae and pn's stand out against a dark background. It efficiently blocks out any light except that emitted by nebulae. The Astronomik uhc filter simply was not designed for galaxy imaging. It isn't a general purpose light pollution filter, which, imo, should block light from artificial light sources, such as sodium and mercury lights.

With this filter, you can probably get great results on M27 but not on M31, from a light polluted area.

Thanks Wim...

It's the clip in rather than the visual but i think the transmission curve is the same or similar. To be fair to myself, i would have removed it if i was targeting it from the start of the session but i just went there when the veil disappeared and i was too tired to re-focus!

Tim.

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Here is my go at injecting some colour.

Its a bit artificial but I did tease some out. Processed in photoshop. Boosted blues by using curves in blue channel and also boosted yellows with LAB colour with various other bits of smoothing, Camera Raw filter, Level, star reduction, etc etc. I'm sure the best way is to leave the filter off if possible! 

598b5a1cce2d2_M31-secondstack.thumb.png.0ec3dfaebf5e7890a02c5c2db97911b9.png

 

Edit...oops...a bit browny...

 

598b5e21f1678_M31-secondstack1.thumb.png.3e72e6af5d17fbc65b176d3f421b8a60.png

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Thanks for trying, Tim, but as the thread progresses, I don't think it can be saved with the current data. I won't throw it away, but I'll add more data without the clip-on filter. If the bloody clouds will ever disappear from this cursed island...

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If you decide to reshoot this target, you may be able to use the subs that went into this image as part if a synthetic luminance. If you can get the framing near identical.

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4 minutes ago, wimvb said:

If you decide to reshoot this target, you may be able to use the subs that went into this image as part if a synthetic luminance. If you can get the framing near identical.

Should be quite simple to do that. This image already consists of two separate sessions of near identical framing.

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12 minutes ago, Datalord said:

Thanks for trying, Tim, but as the thread progresses, I don't think it can be saved with the current data. I won't throw it away, but I'll add more data without the clip-on filter. If the bloody clouds will ever disappear from this cursed island...

The clouds will go away... just as the moon goes past 90%. They will return as the Moon wanes...

 

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