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Costas Soler

DSS will only stack one image! Please help! :(

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Hi!

I did an imaging run on the Flame/Horsehead Nebulae last night, and I got about 2 hours of data. About 20 minutes worth are with my hydrogen alpha filter. To my dismay, when I went in to stack my subframes on DSS, I get a message saying that only one out of my 52 frames will be stacked. I've been tinkering with the settings today, but I'm not sure if the problem lies with my DSS settings or with the frames. These were the first i've taken at ISO 800, so I'm worried that my stars may be a little too big/burnt out for DSS to actually recognize them as stars. Perhaps I haven't focused well enough? I think that's a distinct possibility with my hydrogen alpha frames. I did use my trusty Bahtinov mask, so I hope I didn't goof on that! Anyway, I'm including some representative subframes if you'd like to take a look. 

I'm taking the average for the subframes and calibration frames) 

DSC_0540.jpg

DSC_0580.jpg

Edited by Costas Soler

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Hi. The blue ones should stack fine but to my eyes, the red is out of focus. Maybe refocus on Alnitak and make sure the camera is at the same angle after any filter change? HTH.

Edited by alacant

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Have you tried changing the register settings under advanced? What does the star count come out as? Some people say to set it around 60 - 150 stars I personally leave it at 10% check also under lights that it is under standard or median. I only use sigma kappa clipping when I have a lot of frames but no darks or flats. 

If nothing works do a reset to default on DSS and try again. Let us know how you get on. 

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1 hour ago, alacant said:

Hi. The blue ones should stack fine but to my eyes, the red is out of focus. Maybe refocus on Alnitak and make sure the camera is at the same angle after any filter change? HTH.

By the way I also agree the red frames look out of focus. Try stacking the blue ones first. 

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Hi everyone, thanks a lot for your responses :)

So I'm trying to set the register settings to 10%, and this ends up showing several thousand stars! This is really unusual; I've used around 10% and even 2% on pictures with dimmer stars than this and ended up with good results (usually about 150 stars just  like Gerry recommended). DSS is freaking me out haha.

Any thoughts?

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It might be worth trying the register setting at the other end of the scale - say 75 - 80% and seeing if that brings the number of stars down?

Also, try eliminating (or at least unchecking) the frames with low scores.  

As well, try stacking each set separately. 

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Several thousand! When I did the Rosette nebula I got around 2,000 stars but there is that amount there so I left it at 10%. 

I would reset it and just do a straight stack without touching anything of your blue frames. I think your H alpha you will need to do again. 

Lets see the result! 

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what version of dss are you using. I had this before and it was down to using an old version.

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This is a frustrating one, I am guessing that you are finding stars on individual frames but when you go to stack them no stars are being detected?

If this is the case its because you need to change the background calibration setting in DSS....I think to per channel background calibration....or maybe the other way around, either way there are only two settings...

When you are processing narrow band images taken with an OCS camera like a DSLR it fails to see the stars because they are only appearing in one the three channels and can be calibrated out as a result as would be the case with a hot pixel. As such no stars are detected for alignment and you end up with the exact message you have. 

That solved it for me but it was a long long time back and I have not messed with those setting since so I cant 100% remember what I did.  

Good luck!

Edited by Adam J
  • Thanks 1

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Hi everyone! And thanks again for the responses - VERY helpful!

So here's the deal: I tinkered with he register settings, trying all the way from 2% to 80%, and I was getting nowhere. And the other parameters have never failed me before, and so I kept those how they were ("changing one variable at a time," as they say in my lab classes). So I went through all of my subframes ne by one, and about half of them had streaked stars! I would normally suspect I messed up the auto guiding, but I think that the problem lies with my roof. The roof of my apartment building is a bit rickety, and I think that my presence up there alongside the telescope (the whole time breathing, shifting in my chair, etc) caused vibrations that shook the scope. In all honesty, about half of the frames were not acceptable for use in a final image, so I ended up putting in only the frames in which the stars showed up as perfect circles. I tried stacking these with my stacking settings were at 46%, and it did the trick! I've attached the image below. It's waaaaay lower quality than the rest of my work, but at least it stacked this time! This is a jpeg of the original DSS output. I tried processing it a bit, but there is a really bad moonlight gradient, and not too much detail. I included this version in case it is more useful as a diagnostic tool.

I think the main sources problems in my initial data were the full moon and the shaky roof. My plan to combat this on the next imaging run (this weekend if the weather holds) is to avoid shooting in moonlight (which should be a bit easier this weekend) and to set up at a better site. Luckily, my astronomy department gave me approval to set up my AP setup on their roof and image from there - a far more stable platform that even has a permanent 17" telescope dome (hope to take that out for a spin in the coming months!!!). Anyway, do you have any tips on how to get an improved version of this image besides more data and the improved site?  

Thanks so much, you guys are heroes!!!

horsehead first stack.jpg

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Hi are you trying to stack H-a frames along side other filters?

 

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I'm planning on stacking Ha frames alongside the images I took with an Astronomik CLS filter, and possibly with my Baader Oiii filter. Also great work PeterPCP. Thanks a lot!

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