More DSS help needed!

[StargeezerTim]

DSS is doing my head in. I have 44 of these:-

When i stack in DSS i get this:-

I have tried different stacking modes, tried stacking just a few, tried stacking with or without calibration frames, all I get is more of the same.

I even tried it on the previous version (3.3.2). I could stack the lights OK but it changed the image size of the light so they wouldn't stack with the Flat and bias frames.

In the past, I have changed from Auto to Bicubic stacking mode but I can't seem to solve it this time . Another image I took last night stacked OK. The only thing I can think is that the images were quite bright with the histo towards the right, but it has stacked similar stacks in the past. Any ideas anyone?

 

[Knight of Clear Skies]

I've had the same thing before, adjusting (usually reducing?) the star detection threshold when registering often fixes it.

[StargeezerTim]

Thanks... Didn't work I'm afraid. I've now tried detection thresholds from 10% (11000 + stars) to the highest that will detect stars (56%).  

[StargeezerTim]

Still in need of some wisdom here!

I've run through the stacking about 25 times with different settings with little success. I did find a way of stacking half of the subs but thats the most I can do. I did that by opening all the subs in camera raw, reducing exposure of the subs so the histo was towards the left then saved them as DNG files before stacking in DSS. Despite all the subs looking the same, 20 stacked but any more and i get the same result as before. They were taken in last nights moonlight but I have done this before without problems.

All suggestions welcome...

[Knight of Clear Skies]

It's very frustrating when this happens, I've usually been able to work around it but I have a few data sets I can't stack. Here's a previous thread on the subject. I believe it's some kind of registration problem, DSS is aligning the top of the image correctly but failing at the bottom. I found adjusting the star detection threshold reduces the arc at the bottom even when it doesn't eliminate it. If you do find a solution I'd be very interested to hear it.

I don't know what causes it, I wonder if something changes over the course of the run - seeing, focus creep or drifting too much off target. Or it could be the DSS alignment isn't quite up to scratch. From memory the 'apply median filter to reduce noise' option fixed it but left me with a soft image. Here's a few suggestions:

- Crop the subs down a little (easy to do in Canon DPP, crop one, copy recipe and apply to all others, then batch convert to 16-bit .tiff). Could help if DSS is failing to align at the edges.

- Put the subs on Dropbox and see if anyone else is willing to stack with a different program.

- Try stacking without calibration frames.

- Try reducing the brightness more before stacking (thanks for the tip on that one). I'm a little suspicious of DSS and bright subs as I've had problems when working at fast focal ratios.

 

Hope that's some help. Good to hear you've at least had some success - 20 subs may be enough for a good cluster image.

[wxsatuser]

So there is some thing wrong in the other 20 subs.
There does appear to be a bright arc near the bottom, could be throwing the stacking out.

Can have a bash with PI and Registar if you can post the subs somewhere.

 

[StargeezerTim]

2 hours ago, Knight of Clear Skies said:

Hope that's some help. Good to hear you've at least had some success - 20 subs may be enough for a good cluster image.

Thanks...   I have tried again this morning, reducing exposure more and cropping in Adobe Raw. I cant even replicate my 20 sub stack of yesterday! Never mind, as you say, I've got 20 subs which is enough for a nice image.

This is very frustrating... time to forget about it and do something else for a while... I blame the pesky moon!

[StargeezerTim]

2 hours ago, wxsatuser said:

So there is some thing wrong in the other 20 subs.
There does appear to be a bright arc near the bottom, could be throwing the stacking out.

Can have a bash with PI and Registar if you can post the subs somewhere.

 

Thanks Mike,

I don't think there is anything wrong with the subs apart from be exposed to the right. I'll try and work out how to 'dropbox' them this evening and I'll send you the link. It would be good to know if PI stacks without problem. Don't spend much time on it though if its not straightforward or doesn't stack first time. Cheers, Tim. 

[wxsatuser]

Ok Tim I had a play.

PI did'nt like them, had an error could'nt match star pairs or something like that.

So went to DSS and I think I may have found a problem that can cause this smearing.
By accident I registered and stacked in super pixel mode this gives a half the image size.
This stacked ok and nice image but I wanted the full res, restacked in normal mode, low behold a smeared image.

Seems if you register in super pixel mode and stack in normal this will happen, I suppose it will do vice versa as well.

Here is the image full res but slightly cropped to lose stacking artifacts.
Still some gradients that DBE in PI would'nt remove, did'nt bother to much with that.

So stacked in DSS latest version, normal mode, DBE and masked stretch in PI and some fiddling in PS CC.

[Knight of Clear Skies]

29 minutes ago, wxsatuser said:

So went to DSS and I think I may have found a problem that can cause this smearing.
By accident I registered and stacked in super pixel mode this gives a half the image size.
This stacked ok and nice image but I wanted the full res, restacked in normal mode, low behold a smeared image.

Thanks, I will give this a try on one of my problematic images. I had to dig around to find this option, it's under 'recommended settings' I think.

[wxsatuser]

2 minutes ago, Knight of Clear Skies said:

Thanks, I will give this a try on one of my problematic images. I had to dig around to find this option, it's under 'recommended settings' I think.

Yes it is, if it's green it's active, if blue not.

Also remember to clear all the old stacking info files

[StargeezerTim]

Thanks Mike,

I have pm'd you as I never use the superpixel mode so I'm not sure would account for the problem. I'm having a play now...

Update... they stacked OK in superpixel mode, so thats progress... now to clear out stacking files and try in normal mode...

[StargeezerTim]

No luck I'm afraid. The solution has not worked for me. I registered and stacked in the same mode, checking the Raw settings prior to both registering and stacking. I tried both bilinear and AHD interpolation. Cleared out file and stacking settings between each go...

Perhaps I'll try uninstalling and reinstalling and see if that works... 

Thanks for trying Mike.

[wxsatuser]

The settings I use.

Bilinear debayer
Kappa Sigma clipping
Use RGB background calibration
Mosaic mode
Align RGB
Alignment automatic
 

 

[StargeezerTim]

Just managed to stack them, on the umpteenth try! The only differences were I didn't use mosaic mode or align RGB. The first time it didn't work so I went back and created a new file list and bingo! Thanks for you help. As usual, this site solves the problem through its helpful stargazers... 

[StargeezerTim]

2 hours ago, wxsatuser said:

The settings I use.

Bilinear debayer
Kappa Sigma clipping
Use RGB background calibration
Mosaic mode
Align RGB
Alignment automatic
 

 

Arrrrgh! I spoke to soon....

There is still some smudging at the bottom centre of the image. What star detection threshold did you use Mike?

[StargeezerTim]

Ha ha ha ha.....

This is getting ridiculous. Latest try, after reinstalling and following all the same steps. I give up!

[carastro]

Is there still a DSS yahoo forum?  I would suggest posting these up on there, they are most peculiar expecially the one in the last post.

Carole 

[wxsatuser]

4 hours ago, StargeezerTim said:

Arrrrgh! I spoke to soon....

There is still some smudging at the bottom centre of the image. What star detection threshold did you use Mike?

Star detection 10%

Were you using you calibration frames?

I did'nt bother using them just the lights.

[StargeezerTim]

1 hour ago, wxsatuser said:

Star detection 10%

Were you using you calibration frames?

I did'nt bother using them just the lights.

Da Daaaa....

Case Solved! After at least 30 unsuccessful stackings I finally got there. Its the registration process, I unticked the 'automatic detection of hot pixels' and it now stacks perfectly. No problem with calibration frames either. I can only assume that it was mistaking hot pixels for stars... answers on a postcard please. Perhaps this need to be unticked on bright images as its never caused problems before.

This hobby really firms up your problem solving and persistence. 

[dph1nm]

I recommend going into the manual star editing mode when you have problems and check what DSS has actually identified as stars. Also, cut the number of detected stars right down. DSS only needs 8 stars in common between the frames to align correctly, and it is easy to check this number by hand with the editor. There is no point in having huge numbers of stars as DSS only corrects for linear x,y shifts and rotation - it does not try to fit distortion terms.

NigelM

[Knight of Clear Skies]

On 8/13/2017 at 18:54, StargeezerTim said:

Its the registration process, I unticked the 'automatic detection of hot pixels' and it now stacks perfectly. No problem with calibration frames either. I can only assume that it was mistaking hot pixels for stars... answers on a postcard please. Perhaps this need to be unticked on bright images as its never caused problems before.

Hi, was it just for the registration that you unticked this option please? I'm having trouble stacking some new data.

[StargeezerTim]

Yep, just registration if i remember correctly. I also remember having a simalar problem shortly after where that didn't work. I've had no trouble recently, it seems to be just in images exposed to the right. Best of luck... when DSS works its great, when it doesn't, its a pain.

[Knight of Clear Skies]

Thanks. I tried that option with no success, but converting the lights to TIF files in Canon DPP (which filters out hot pixels) and stacking with no calibration files worked. My next step is to convert the calibration files as well and see if it still stacks OK, if so it's probably hot pixels causing the misalignment.

Stacking the TIF files gave me this, which looks OK at a small size but the stars have black halos around them.

 

[StargeezerTim]

I know its frustrating, but i hope the calibration stacking cures the halos. Thanks for sharing your workaround, that could prove very useful when i next have problems...