Can't get the hang of it!

[Astrosurf]

To start with, I do about two or three stretches in Levels, balance colour if necessary (as Olly said), then I go into Curves and play around. For colour images (not mono), I generally aim for an 'S' shape with the bottom left (dark areas) pulled over to the right and the opposite for the top.

To control specific levels of brightness in the image, hold down the Ctrl key and click on the image in a few places and the Adjustment Points relating to that brightness will be placed on the Curves line. If you don't want an area to be affected by your stretching, put an Adjustment Point closely either side of it and it'll stay put.

To remove a Point, pull it hard over to the right and off the chart.

Do check Levels repeatedly when doing Curves, to ensure the black isn't clipped. Just have a play around to see what happens.

Good luck!

Alexxx

[ollypenrice]

As Alex suggests, processing is all about lots of little and selective steps, each punctuated by a careful check, notably of the black point which easily gets nibbled away!

Olly

[Herzy]

Does anyone know why my image has these streaks going through it? They are visible on both images and they go up diagonally. Very strange...

Update: I downloaded startools and I played around with it. I tried all of the advice I got and I was able to get a decent image. 

[The Admiral]

21 hours ago, Nejim said:

Yes star tools is very good. I can't get my files into it anymore though.  I have only TIFF files and it won't accept them. Grrrrr

The tiff output by DSS I think is a compressed file, and may be ST doesn't like those. You could try opening the tiff in a photo processing application and re-save as an uncompressed tiff.

Ian

[alacant]

I think DSS saves in 32bit tif which StarTools maybe can't do(?). It can do 16bit tif fine.

[The Admiral]

10 hours ago, alacant said:

I think DSS saves in 32bit tif which StarTools maybe can't do(?). It can do 16bit tif fine.

I opened a FITS file in DSS and saved it as 16-bit TIFF, and as 32-bit rational and integer TIFFs, all uncompressed, and ST opened all. On the other hand, I'm under the impression that autosaved  TIFFs are compressed by default. However, as I don't use autosaved TIFFs as the input to my ST processing, I can't check whether ST will load them, though I've reason to believe it will.

So why ST won't open Nejim's files is still a mystery!

Cheers - Ian

Edit. Ah, I remember now, when I tried to open Herzy's M42 image that he'd placed in a dropbox (https://stargazerslounge.com/topic/268432-failing-miserably/?do=findComment&comment=2938993) I found that ST couldn't open it. However, having opened it in Picture Window Pro and re-saved it as an uncompressed tiff, it would open.

[The Admiral]

10 hours ago, Herzy said:

Does anyone know why my image has these streaks going through it? They are visible on both images and they go up diagonally. Very strange...

Update: I downloaded startools and I played around with it. I tried all of the advice I got and I was able to get a decent image. 

Glad you are moving on to a proper astro package Herzy, wishing you every success with it.

As to the streaking, my guess is there is noise from your sensor, which on individual frames appear as pixel points, but of course your image has drifted over the sensor throughout all your exposures. So when the images are stacked, the stars and target are aligned, but of course the background noise will then appear as though it has moved. With lots of frames that noise will appear as a line, tracing out the movement of the target/stars. I presume that is what wxsatuser means by 'walking noise'. I don't know what ISO you are using, but I'd keep it around 1600. Also, darks and flats will help correct your image for this.

Ian

[happy-kat]

There is no short cut to good images without calibration frames I don't think.

[wxsatuser]

1 hour ago, The Admiral said:

Glad you are moving on to a proper astro package Herzy, wishing you every success with it.

As to the streaking, my guess is there is noise from your sensor, which on individual frames appear as pixel points, but of course your image has drifted over the sensor throughout all your exposures. So when the images are stacked, the stars and target are aligned, but of course the background noise will then appear as though it has moved. With lots of frames that noise will appear as a line, tracing out the movement of the target/stars. I presume that is what wxsatuser means by 'walking noise'. I don't know what ISO you are using, but I'd keep it around 1600. Also, darks and flats will help correct your image for this.

Ian

Yes, the noise tends to walk with any drift.

It's obvious on the hot pixels and when the image is stretched the colour mottle walks with the drift.
Because it's not a random movement it's hard to kill, unlike dithering where a random movement will cancel the noise.

I once spent 4hours on M101 and had drift that I did'nt realise, the walking noise was terrible and could'nt remove it.
I tried calibration frames, actually took some for that target but I could'nt shift the noise.

Now I have no real drift apart from the obvious displacement of dithering.

[Herzy]

Tonight I was able to get 2 hours of data. I can't wait to process it tomorrow morning! This time I have calibration frames.  

[Astrosurf]

Please show us the results. Good luck!

[Herzy]

I'm not too good at processing so it could definitely be better, but this is the kind of results that I never imagined I would be able to get. These galaxies are millions of light years away and I'm imaging them in my backyard... That's pretty cool! 

[The Admiral]

Well done Herzy, you got there in the end! Great news, and you're feeling what keeps most of us at it.

Can you supply more details please? Like name of object, number of subs and sub length. What did you process in? If you're using Star Tools, don't be afraid to use the colour module, if you don't like the results you can always cancel.

Ian

[Herzy]

Target: M101

Exposure: 110 x 1m, 16 x 1m darks, 16 x flats. 

Equipment: AVX, C6-N, and Nikon D3200.

I processed in Nebulosity and Startools. I'll try to further process it, this was just a rough process. Thanks for all the help everyone!

[Astrosurf]

Excellent job for such short exposures! Did you use Wipe in ST? It gets rid of vignetting, gradients and light pollution.

[Herzy]

I tried that but it made some weird colors. :/ Your supposed to run auto develop to bring out the imperfections in your image and then use wipe to fix them. Once fixed, you run auto develop again to bring out detail, correct? I tried that but I couldn't remove much of the imperfections/gradients with wipe. 

I ended up just stretching it in Nebulosity and then using some of the various tools in Startools to clean the image up.

[Astrosurf]

I wish I could help. ST hates me! I just remembered what Wipe does.

[The Admiral]

Always worth cropping the borders before doing a wipe, as ST always seems to warn you about stacking artefacts! Also, you don't have to use auto dev when you re-do the global stretch, you can use standard develop and adjust according to taste. I also find that I get a better result if I increase the dark anomoly filter, though it does take much longer to process.

Ian

[bottletopburly]

Drop box your file  

[Herzy]

5 hours ago, bottletopburly said:

Drop box your file  

https://www.dropbox.com/s/dieyvqlvmjlhblj/Stacked%20-%20M101.tiff?dl=0

There you go! You can mess with it and see if my processing was any good or if it can get a lot better.

[Marky1973]

Herzy, I had a quick fiddle - very quick as I am supposed to be cooking my wife's dinner, but it does show you how more data really helps the image come out. When I was playing, I noticed that there were some donut shaped stars, which suggests a slight focus problem - donuts can also be caused in DSS (are you using that) if you stack with the Hot Pixel Detection/Removal boxes checked in the COSMETIC Tab in the stacking settings.

Not sure it is much better than yours, and I ended up over-sharpening it in my hurry, so I won't bother posting it - but I think you did a good job with the processing. It's all about practice though, so keep at it and keep taking more and more data.

Thanks for letting us play - I'm still learning, so its helpful to fiddle!

 

 

[Herzy]

It was a focus problem. They are visible in the single frames as well. I will fix that in the future.

[Herzy]

This thread is getting big and I feel bad for being so annoying asking so many questions but I have one more. What should my plan for the future be? Should I just work on getting more data? I read somewhere that once you get to about an hour of data, getting more data doesn't help very much. Is the key to those insanely beautiful shots just hours upon hours of exposure time?

[Astrosurf]

I had a go, but unfortunately without GradientXTerminator as it's not working for me now . Plus what I did - Word doc. It's very simple! it's late and I should be in bed, so rather rushed! The image is too blue, but I didn't try too hard to remove that. I'll leave that up to you!

 

For SGL.docx

[geordie85]

2 hours ago, Herzy said:

This thread is getting big and I feel bad for being so annoying asking so many questions but I have one more. What should my plan for the future be? Should I just work on getting more data? I read somewhere that once you get to about an hour of data, getting more data doesn't help very much. Is the key to those insanely beautiful shots just hours upon hours of exposure time?

 That's not true. Theres a recent thread on here showing the difference between 4 hours of data and 12 hours. The results are quite impressive.