DSS only stacking 15% of live stacked subs

O5w77p3o

On the 10 and 11 of August I imaged mosaics of the Cygnus Loop at 20 seconds per sub using my S50. I was using live stacking and got 491 subs on one night, 507 the other. The targets were different areas of the Loop. Not a particularly impressive success rate, but that’s not the issue.
I checked the subs over, discarded none, downloaded them to my PC and then ran them separately through the DSA Seestar Mosaic pre processing script in Siril. Only 15% of the subs stacked, which was a huge surprise, as normally 100% of my subs stack when I use this process (I always live stacked cos I like to check in and see the image building).
I then reloaded the subs to my S50 and stacked them using DSS. Only 15% stacked. This should, I thought, be impossible, because my understanding is that DSS uses the same process to stack as does the live stacking therefore 100% should have stacked.
Anyone any idea what could be going on? Or any suggestions?
I’m just about to restack (in DSS) a non mosaic target from last night to see how that does…..

Support@Seestar

This issue is most likely caused by the saved subframes being of poor quality, which results in them being automatically rejected by the stacking algorithm during post-processing. Perhaps you could check these FIT files.

O5w77p3o

Support@Seestar .

Are you saying that live stacking in the S50 allows poorer quality subs than DSS? I thought that DSS used the same parameters as live stacking, can you confirm that they are in fact different?

As stated in my original post, all of these subs were saved as part of a live stacking session, but 85% of them were rejected in DSS.

Support@Seestar

O5w77p3o
I don't know, I'd have to see the original image to know because and judge based on the specific situation, this is not a problem of shooting options.

Lilo

O5w77p3o
I'm not familiar with DSS but there must be some criteria in it's settings for subs filtering and some log, which subs were rejected and why.
And why did you assume that DSS an Seestar use the same parameters?

O5w77p3o

Support@Seestar I’m sorry, but I don’t understand your response.
Can you confirm if Live stacking in the Seestar app and DSS (Deep Sky Stacking) in the Seestar app are using the same logic and programming, or are they not?

I’m suspicious about this because the first time I used DSS after upgrading to V2.6 it only managed to stack 15% of my subs, where as on every single other occasion where I have used it (maybe 50 or 60 times) it stacked 100%.

If your answer is ‘they use completely different methodology to stack’ I would firstly be very surprised, but also would start looking elsewhere for the cause of the problem. If your answer is, ‘they use exactly the same methodology to stack’ then version 2.6 would appear to have introduced a bug.

O5w77p3o

Lilo
DSS (Deep Sky Stacker to give it its full title) is part of the Seestar App. It’s the option you take when you want to restack subs (they may have been live stacked initially and you want to restack them because of satellite trails, for example) or perhaps you didn’t use live stack and are stacking several sessions.
There are no options, filters or setting on it.
My understanding was that DSS uses the same stacking logic, methodology and algorithms as live stacking. That was borne out in my previous experience by DSS always stacking 100% of the subs I required it to stack. Always, that is, until 11th August, when restacking only stacked 15% of the subs.

Lilo

O5w77p3o
Ok, got it.
That part in seestar app is named Deep Sky Stack.
DSS is common abbreviation for PC software Deep Sky Stacker.

Support@Seestar

O5w77p3o
This can't be a Bug.
DSS does not evaluate individual frames—it stacks all of them—whereas live stacking will directly discard problematic frames.
This is because you were using mosaic mode. In live stacking, problematic frames are discarded immediately, but in mosaic mode, the shots are taken by rotating and moving from the center, and DSS selects the order in which these single frames are stacked differently. The first frame used for stacking may change—for example, it could start stacking from the last frame. In our next version, we can offer users the option to choose the reference frame.
That said, your DSS result is indeed a bit poor. You might want to try capturing again, as I haven’t actually checked your files.

O5w77p3o

Lilo Re DSS, I’m aware of Deep Sky Stacker (and still have it installed on my PC, but never use nowadays), and it caused me some confusion when I first heard of DSS to do with Seestar. DSS has become a common way to refer to the Seestar Deep Sky Stack as well.

O5w77p3o

Support@Seestar ok, thanks. This does answer my question, which is that live stacking and DSS work differently, so I need to look elsewhere for the solution. Interestingly, one of the other issues I have had in the last few days is also to do with mosaics, so more testing needed.