Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

LRGB Alignment

  • Please log in to reply
6 replies to this topic

#1 SuperJustin

SuperJustin

    Vostok 1

  • *****
  • topic starter
  • Posts: 163
  • Joined: 29 Mar 2017
  • Loc: Kissimmee, Florida

Posted 16 April 2018 - 12:39 PM

So there is lots of threads about this topic but not my issue specifically.. Quick back story I just purchased StarTools and am trying to hold off on PI for atleast a year if possible BUT now wondering if the $$$ or headache is worse! I have an ASI1600mm-p which I’m finally getting the hang of with some decent data. So now the issue..

I use DSS for Alignment of the LRGB stacks as I’ve seen quite a few others do too. One thing I have not seen anyone mention is the wierd patterns DSS adds to the stacks after Alignment. It took forever it seems to figure out the best settings for calibration frames and seeing the clean stacks is a reward! It seems a bit silly to lose all that effort during Alignment.. the strange patterns on the aligned stacks are only clearly visible after hitting equalize twice in PS but combining four separate stacks three of which have anomalies from alignment over into StarTools adds a lot of grief that isn’t there to begin with!

So it seems DSS is more then capable of properly aligning the final stacks but there is some setting under “Alignment” tab that’s doing some weirdness to the stacks in the end. Changing the Alignment method give me different patterns. Also reducing the Star detection threshold seems to make the patterns less apparent. But even at minimum values talking 5-6 stars, still there!

In short my question is has anyone else ever noticed this? Am I overlooking something simple and that’s why I can’t find any other users experiencing this issue? Should I just buy PI and say no more headaches (until I try using PI that is 😂)

Thanks for any advise or suggestions!

#2 Alex McConahay

Alex McConahay

    Fly Me to the Moon

  • *****
  • Posts: 6724
  • Joined: 11 Aug 2008
  • Loc: Moreno Valley, CA

Posted 16 April 2018 - 12:41 PM

Could you please post a picture of what you are talking about.

 

Alex


  • SuperJustin likes this

#3 SuperJustin

SuperJustin

    Vostok 1

  • *****
  • topic starter
  • Posts: 163
  • Joined: 29 Mar 2017
  • Loc: Kissimmee, Florida

Posted 16 April 2018 - 01:02 PM

Hey sorry I'm using remoteview.. it works great just takes forever here they are!

 

Green Stack (Equalized x2 in PS to show artifacts)

M84-Green_Stack-Raw.jpg

 

Green Aligned Stack (Equalized x2 in PS to show artifacts)

G.jpg

 

Green is my worst quality stack so most obvious issues I can post more if needed..

 

I get these same issues on ALL my stacks besides the reference frame obviously when aligning in DSS not just this data one night!


Edited by SuperJustin, 16 April 2018 - 01:09 PM.


#4 SuperJustin

SuperJustin

    Vostok 1

  • *****
  • topic starter
  • Posts: 163
  • Joined: 29 Mar 2017
  • Loc: Kissimmee, Florida

Posted 16 April 2018 - 01:24 PM

Blue Stack (Equalized x2 in PS to show artifacts)

M84-Blue_Stack-Raw.jpg

 

Blue Aligned Stack (Equalized x2 in PS to show artifacts)

B.jpg

 

I tried aligning this one over a dozen times this was the best I could get.. change in pattern to almost like grid shape not as noticeable but still there! also I was using the L Stack for reference in this one that's why it doesn't match the Green aligned stack in orientation.. just throwing that out there in case someone notices!


Edited by SuperJustin, 16 April 2018 - 01:30 PM.


#5 SuperJustin

SuperJustin

    Vostok 1

  • *****
  • topic starter
  • Posts: 163
  • Joined: 29 Mar 2017
  • Loc: Kissimmee, Florida

Posted 16 April 2018 - 03:23 PM

I've checked all my old data stacks and all of them have some form of this anomaly from using DSS to align. Could anyone else that uses this method confirm if they are having the same issue on their DSS aligned stacks? That could at least reasonably rule out user error!

 

Also if your using StarTools and stacking as recommended with no background calibration but using kappa sigma instead of average/median you will have a whole separate problem with weird grid patterns on your stacks before even aligning. You can increase the kappa figure to hide but I found it's best so far to use per channel calibration and in options turn RGB background calibration to none



#6 Alex McConahay

Alex McConahay

    Fly Me to the Moon

  • *****
  • Posts: 6724
  • Joined: 11 Aug 2008
  • Loc: Moreno Valley, CA

Posted 16 April 2018 - 03:24 PM

PI is not the answer to this. 

 

And Registration is not the issue. If it were, the stars would not be properly aligned.

 

What were your exposure times? You may not have enough data here to separate the low signal from the background of the chip itself. Then, when you double stretch it, the engineering of the chip itself is showing. 

 

Did you use bias frames and darks?

 

Ps....do these weird patterns show when you do a simple stretch of the whole image?

 

There is this thing called the "Flashlight Test" that people use to see if their mirror is dirty. THe Test ALWAYS shows dirt and dust. So,  "What to do if the Flashlight Test shows dust?"  Well, "Stop using the Flashlight Test. It always shows dust."

 

Alex


  • SuperJustin likes this

#7 SuperJustin

SuperJustin

    Vostok 1

  • *****
  • topic starter
  • Posts: 163
  • Joined: 29 Mar 2017
  • Loc: Kissimmee, Florida

Posted 16 April 2018 - 03:37 PM

PI is not the answer to this. 

 

And Registration is not the issue. If it were, the stars would not be properly aligned.

 

What were your exposure times? You may not have enough data here to separate the low signal from the background of the chip itself. Then, when you double stretch it, the engineering of the chip itself is showing. 

 

Did you use bias frames and darks?

 

Ps....do these weird patterns show when you do a simple stretch of the whole image?

 

There is this thing called the "Flashlight Test" that people use to see if their mirror is dirty. THe Test ALWAYS shows dirt and dust. So,  "What to do if the Flashlight Test shows dust?"  Well, "Stop using the Flashlight Test. It always shows dust."

 

Alex

Thanks Alex.. I think you might have just solved my issue... 30s for L and 65s for RGB.. After calibration frames subtracted I'm at a median value of a little over 100 16bit DN.. Initially when I collected my data I thought the bias value was about 250 so I was exposing in APT to about 800 @ 0 gain. After talking to Jon Rista and showing him the older graph I was looking at he corrected my thinking to bias value more like 800 so indeed I am under exposed and all my efforts to correct in DSS have been to fix something that should have never been an issue if the data was exposed properly... Got to love this hobby haha thanks for the sanity check. Disregard my DSS settings posted above clearly user error!




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics