DEEP SKY STACKER problem - stacking on comet

[frewi808]

Ok guys, I have stacked a few comets over the last few weeks and all get different results, some good and some bad.

I just want to now what the best settings are for stacking ON come AND stars..

I'm using the new 3.3.4 DSS program..

LoveJoy A.tif

[frewi808]

This is the stacked image.

[frewi808]

anybody familiar with this problem ????

[happylimpet]

comet and star stacking has never worked for me!

[carastro]

I had a problem with DSS and comet stacking when I tried to use it.  It would stack on the stars OK, but then the comet head trailed.  I managed to get away with this on my first image by just blurring the head of the comet as it hadn't trailed too far.  

I guided on the comet and tried the comet mode stacking, but it registered the comet OK, but just wouldn't save consistently and then when it tried to stack, it said it would only stack one frame, so i gave up with DSS and stacked manually in Photoshop.  It also worked OK in Registax with my Mono camera, but Registax couldn't latch onto the head of the comet with the DSLR.

If you want any further information on how I did the stacking in photoshop just shout.

Is there a mode for stacking on both comet and stars in DSS?  Can't see how it would work.  I thought you always got star trails if you stacked on the comet.  

Carole 

[happy-kat]

Yes there is and I use it. It essentially runs two stacking passes then I guess merges them takes ages but works.

You have to mark the comet position on every light frame saving every frame as you do it then stack.

[carastro]

You have to mark the comet position on every light frame saving every frame as you do it then stack. 

OK maybe I don't have a late enough version of DSS.  Having said that just trying to stack on the comet, I did mark and save every light frame, but it was inconsistent in saving and I had to keep re-doing some of them, but even when they were all saved it decided it was only going to stack on one frame.

Carole 

[happy-kat]

I am using 3.3.4.

Register all files first.

Then pick one light at a time and using the comet tool mark the centre position holding shift key and save. Repeat for all lights.

Select Stack and on the comet tab I have been choosing the last option.

That has worked for me.

[happylimpet]

I'd yr images are time stamped you only need to locate the comet on the first and last.

[happy-kat]

Mine images are not totally regular on time intervals but I could try that next time, though I have just don't another dss process following my normal approach and it worked.

[carastro]

I am using 3.3.4.

Register all files first.

Then pick one light at a time and using the comet tool mark the centre position holding shift key and save. Repeat for all lights.

Select Stack and on the comet tab I have been choosing the last option.

That has worked for me. 

Just went to try that, but couldn't see where to register the files.  

I had already tried to align the first image comet core in comet mode, but it wouldn't save.

So I tried seeing what would happen if I went into the register images mode in the normal stacking method, and it then went on to stack, so I was expecting it to align on the stars as per normal.  However it stacked the whole lot using the comet head I had selected once and not been able to save as the alignment feature.

There is no logic in this, but I got an aligned comet with trailed stars by completely the wrong method.

Any comments on this?

Carole 

[happy-kat]

Hi

This is more than you are asking for but it might help someone else.

After loading all the images into DSS ensure to select Check All.

Then select Register checked pictures (marked as 1 on the last image).

On the resulting dialog do not select Stack after registering.

Now that all images are registered select the first light in the sequence.

See last image.

On the menu on the right hand side select the comet icon (marked as 2 on the last image). For my light it is showing the circle where I had previously saved the comet's position.

Using your mouse wheel you can zoom in and out to get a better view for finding the comet.

Once located I hold the shift key and carefully position the mouse pointer in the middle of the comet and then pick the mouse left click button.

Now select the save icon on the same little menu.

Repeat for all Lights (this is what I do).

Now select Stack checked pictures and then Stacking parameters now select the Comet tab and chose what you want and fiddle with any other settings of choice on the other tabs.

And wait... takes a while.

[Leveye]

What if you want to get a picture of just the comet without any stars at all? I've seen it done but have yet to be successful using DSS. Can anyone run through the exact procedure please?

I've gotten a really great comet picture using just comet only mode with star trails like this..

Removing these trails in PS using a clone stamp can be done but it is a real time consuming challenge.

I have a pretty decent starfield only shot but want to combine this and the comet only shot without any trails at all in PS for a more natural look. When i try using the Sigma Kappa settings the program tried to stack but fails to after a few minutes.

 Using comet and star stacking mode the starfield looks great but the comet's head has breaks in it and it's green color is way way off with lots of banding. It's most likely from me having to get rid of a few bad pictures in the series of 25 so there are breaks now.

Any help would be greatly appreciated. 

[Psychobilly]

I tried various stacking parameters in DSS the results can be seen here...

http://stargazerslounge.com/topic/234742-inspired-by-steppenwolf-c2014-q2-lovejoy-variations-on-a-theme/?p=2540821

There was a link to a tutorial the other day with a better method... which involved splitting your subs up into groups so that the stars weren't overlapping in subsequent subs staking each group then stacking the results of the stacks - probably explained that incorrectly or at least very badly...

Here's the link to Tonk's thread...

http://stargazerslounge.com/topic/235241-someone-might-find-this-useful-star-freeze-comet-images-tutorial/?hl=%2Bcomet#entry2546900

Peter...

[Leveye]

Thank you for the links. Very helpful!

[Psychobilly]

Your welcome

[Tonk]

"I'd yr images are time stamped you only need to locate the comet on the first and last."

If your reference frame isn't the first (or last) you should also mark the comet in the reference frame as well. The images *don't* have to be a regular intervals - they just need a time stamp (your camera normally does this for you and sticks the data in the RAW header section)

 

I nagged Luc in 2007 to add the time-stamp interpolation feature to DSS to get perfect alignments. He had it all working perfected in less than a day - but the feature has never been fully documented (at least not on the DSS site).

 

[Tonk]

Forgot to say - don't use the DSS star freeze method - the comet-only and star-only image combination step is the fragile bit and frequently goes horribly wrong.  Its best to do the "comet aligned" and "star aligned" stacks yourself - do the clean ups - and then use "screen" blending mode to combine the two results (if Photoshop) or if you have software that does pixel math - then "screen" blend is just the same as a straight image pair addition.

 

The key steps are comet aligned stack should use kappa-sigma with iterations around 10 and a kappa value of 1.5 down to 1.2 (experiment - the trade is less star trail remnants vs. noisier final image) to remove the unwanted stars. The star aligned image should use median combine followed by a standard background extraction technique to loose the softly blurred out comet.

 

One of my tutorials is linked to above - it doesn't discuss the blending mode but as I reveal above its "screen blend" or "add". ...... A tip here - make sure that after you have done the background extraction with the stars-only image that you a ) offset the background so that the average "deep space" pixel values are (15,15,15) and b ) add some noise back to the image - in Photoshop I use the add noise filter set to 0.1 to 0.3  (background extraction leaves the image unnaturally smooth). For the comet-only image you can use horizontal / vertical de-banding filters to get the final star trail artefacts removed (rotate the image to make the faint trails horizontal or vertical - and when done reverse the rotation) and set the background "deep space" pixel values to  (10,10,10) - (15,15,15). After the screen blend when combining the two images the background values add together to give (25,25,25) to (30,30,30) which is an ideal background brightness (for a 0 - 255 RGB brightness scale)

Also Kerry-Ann Lecky Hepburn has written up the standard technique (in not too much detail regarding settings and tool options I'm afraid - but she has at least got screen shots of the steps so you can at least see what is expected) - http://www.weatherandsky.com/blog/2013/5/comet-processing-for-non-trailing-stars-and-comet

 

 

[Stub Mandrel]

2 minutes ago, Tonk said:

Forgot to say - don't use the DSS star freeze method - the comet-only and star-only image combination step is the fragile bit and frequently goes horribly wrong.  Its best to do the "comet aligned" and "star aligned" stacks yourself - do the clean ups - and then use "screen" blending mode to combine the two results (if Photoshop) or if you have software that does pixel math - then "screen" blend is just the same as a straight image pair addition.

 

The key steps are comet aligned stack should use kappa-sigma with iterations around 10 and a kappa value of 1.5 down to 1.2 (experiment - the trade is less star trail remnants vs. noisier final image) to remove the unwanted stars. The star aligned image should use median combine followed by a standard background extraction technique to loose the softly blurred out comet.

 

One of my tutorials is linked to above - it doesn't discuss the blending mode but as I reveal above its "screen blend" or "add". ...... A tip here - make sure that after you have done the background extraction with the stars-only image that you a ) offset the background so that the average "deep space" pixel values are (15,15,15) and b ) add some noise back to the image - in Photoshop I use the add noise filter set to 0.1 to 0.3  (background extraction leaves the image unnaturally smooth). For the comet-only image you can use horizontal / vertical de-banding filters to get the final star trail artefacts removed (rotate the image to make the faint trails horizontal or vertical - and when done reverse the rotation) and set the background "deep space" pixel values to (5,5,5) - (10,10,10). After the screen bland when combining the two images the background values add together to give (20,20,20) to (25,25,25) which is an ideal background brightness (for a 0 - 255 RGB brightness scale)

Also Kerry-Ann Lecky Hepburn has written up the standard technique (in not too much detail regarding settings and tool options I'm afraid - but she has at least got screen shots of the steps so you can at least see what is expected) - http://www.weatherandsky.com/blog/2013/5/comet-processing-for-non-trailing-stars-and-comet

 

 

That's useful. I will check that out and revisit my badly stacked comet shots!

[Tonk]

What if you want to get a picture of just the comet without any stars at all? I've seen it done but have yet to be successful using DSS. Can anyone run through the exact procedure please?

 

See post above - use kappa-sigma stacking and a de-banding filter