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Has anyone used both (expensive) Astro Pixel Processor and (free) Sequator for image stacking, and found APP to be definitely better?

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#1 Those Who Squirm!

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Posted 12 April 2024 - 05:02 PM

And what is it about APP that justifies the cost?

 

About six months ago I had a little cash in my pocket and plunked it down for a lifetime ownership license to Astro Pixel Processor.  I had used APP in the past, on a rental basis, when I was unaware of any alternatives, and I'd been satisfied with it at the time.

 

Over several years, I let my rental license lapse, and then discovered Sequator, which is freeware.  It's truly free, not "trialware" or "downloadware" that doesn't let you save anything.   

 

I'm continuing to use both, and I can't convince myself that APP is any better than Sequator, and in fact it seems that it may be worse.  I list below my impressions.

 

Sequator advantages

  • Completely free
  • Very fast, needing only about a minute or two to process a stack of nine exposures
  • Outputs a final stacked image which is useable/presentable as is

Sequator disadvantages

  • None that I can find.

Astro Pixel Processor advantages

  • None that I can find

Astro Pixel Processor disadvantages

  • Expensive
  • Requires user intervention to launch several steps of the process
  • Extremely slow, taking maybe fifteen minutes to process a stack of nine exposures
  • Produces an ugly, washed out, and vignetted output image which is unusable without further editing

 

I'm not saying that I altogether regret having bought APP.  I'm continuing to use both, and I suppose at some point I'll understand what I'm missing.   Another consideration is that a free app can potentially be taken away, if its builders decide to stop supporting it; whereas if you buy a license, the vendor has some kind of obligation to you.

 

Here's an image output from APP:

53649697411_c571ed78a8_c_d.jpg

 

And here's the same view, processed by Sequator:

 

53649697236_4ac7c2b71e_c_d.jpg

 

 

I know which image I would rather work with in future projects, for example if I wanted to put the stars in a natural sky over a landscape.

 

Maybe APP just isn't particularly good for starscape shots?   FTR I'm still not using anything other than light frames.  I've tried darks and biases, and I honestly can't see any improvement.  That might be different if I were doing deep sky astrophotography through a telescope.


Edited by Those Who Squirm!, 12 April 2024 - 05:05 PM.


#2 maxsid

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Posted 12 April 2024 - 05:14 PM

I often use Sequator for widefield.

Especially if there's landscape included.

Works well.

 

I use APP for DSO.

Works well.

It is slow, yes.



#3 rhart426

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Posted 12 April 2024 - 05:52 PM

Those subframes are so radically different from each other that they clearly had different processes run on them, so I don't think I'd use them as a comparison.  The top one looks like you forgot the flat frames, and then either remembered it for the bottom frame or just turned down the contrast hard enough to hide it.  There are also artefacts on the right side of the bottom subframe that don't appear in the top subframe, so the stacking algorithms are not aligned enough to make a proper comparison.


Edited by rhart426, 12 April 2024 - 05:54 PM.

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#4 Those Who Squirm!

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Posted 12 April 2024 - 07:25 PM

Those subframes are so radically different from each other that they clearly had different processes run on them, so I don't think I'd use them as a comparison. The top one looks like you forgot the flat frames, and then either remembered it for the bottom frame or just turned down the contrast hard enough to hide it. There are also artefacts on the right side of the bottom subframe that don't appear in the top subframe, so the stacking algorithms are not aligned enough to make a proper comparison.



#5 happylimpet

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Posted 12 April 2024 - 07:30 PM

Hmmm. Everything you wrote made perfect sense, and then i got to the example stacks, and, aside from the residual gradients in the APP version, everything about it is vastly better than the sequator stack.

 

However I wonder if the sequator stack has been implemented and/or processed badly.

 

I dont feel this is a fair test. If those are both examples of the best each can do, its APP hands down, but i dont think this is the case.


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#6 Those Who Squirm!

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Posted 12 April 2024 - 07:35 PM

Those subframes are so radically different from each other that they clearly had different processes run on them, so I don't think I'd use them as a comparison. The top one looks like you forgot the flat frames, and then either remembered it for the bottom frame or just turned down the contrast hard enough to hide it. There are also artefacts on the right side of the bottom subframe that don't appear in the top subframe, so the stacking algorithms are not aligned enough to make a proper comparison.

I've never routinely used flats in any case, but maybe Sequator somehow corrects for that. I notice that it doesn't provide the option to process flats, although you can use noise and vignetting frames.

Other than that, you've just given me a reason to try using flats in APP and see if there's any improvement.

Edited by Those Who Squirm!, 12 April 2024 - 07:40 PM.


#7 KuiperBeltKing

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Posted 12 April 2024 - 10:03 PM

However I wonder if the sequator stack has been implemented and/or processed badly.

 

I dont feel this is a fair test. If those are both examples of the best each can do, its APP hands down, but i dont think this is the case.

 

It looks like that perhaps the OP stacked in Sequator with the option to reduce light pollution checked and sigma-clipping not selected as the composition (stacking) mode.

 

I've never routinely used flats in any case, but maybe Sequator somehow corrects for that. I notice that it doesn't provide the option to process flats, although you can use noise and vignetting frames.

Sequator calls flats "vignetting frames" and it calls darks "noise frames".



#8 topcode

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Posted 14 April 2024 - 07:31 PM

Ignoring the discussion about flats and settings, clearly the sequator stack has sat trails, which APP, has corrected for (probably with sigma clipping by my guess) so that is at least one point for APP with the given sample images.


Edited by topcode, 14 April 2024 - 07:32 PM.

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#9 gordtulloch

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Posted 14 April 2024 - 11:34 PM

And what is it about APP that justifies the cost?

I don't use Sequator, but I think you have some misunderstandings about APP - I just load up all of my (occasionally very complex multi-filter) lights and calibration images, go to the last tab, and click INTEGRATE and let it run. Generally it will produce a nice image that I can work on in other tools and also results in master calibration images.  If there's an issue with the resulting image(s), I may go back and tweak a few settings, then hit INTEGRATE again, and it'll redo anything it needs. Substantial time savings over tools where you need to do things manually in most tools (except Siril with Sirilic which I also use but you would also find unsuitable for your use).

 

It is extremely good at mosaics that I do a lot and they are almost as automatic as other DSO  images. This image for example is three panes taken of M31 which it stitched together perfectly with just a couple of settings changes to put it in mosaic mode.

 

You're using a professional tool to do some very basic/simple things if you're not calibrating your images (not to mention doing them in 5-6 different filters), so yeah, it's going to be more cumbersome and not going to spoon-feed you a result. Sequator sounds suitable for your current requirements, but you may grow into APP.


Edited by gordtulloch, 14 April 2024 - 11:36 PM.

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#10 maxsid

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Posted 15 April 2024 - 04:35 AM

OK.

I mentioned here that I do use Sequator for astroscape images.

 

Sequator is able to freeze the background and stack stars and the background separately.

APP or any other stacking software cannot handle this.

 

Note: Sequator also can use flats and darks. Reject satellites and planes and other outliers.

 

Here's the recent example.

Bortle 3 location but shooting in the direction of a large city. Huge light dome.

(the opposite direction was pitch black).

 

I took 64x10s exposures for the stars.

Then I took 600s for the background.

No Moon.

Ricoh GRII basic camera.

 

Stacked the stars with the background frozen in Sequator.

Combined stars and background in Photoshop.

 

stars_plus_bckg-sm.jpg


Edited by maxsid, 15 April 2024 - 04:49 AM.

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#11 Astronomy4You

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Posted 19 April 2024 - 04:09 PM

Since Sequator is pretty fast at stacking I'll frequently use Sequator to stack my images with darks (Noise Images) and flats (Vignetting) to see what I have then move it into APP or Pixinsight for true stacking and Processing. Sequatror can output a linear image or a stretched image. I've had images that did not stack well in either APP or Pixinsight that SEQ handles just fine. So I'll run a stretched version and an unstretched version and see what I get.

 

But I agree for Night landscapes it's the only real option. 



#12 Astronomy4You

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Posted 19 April 2024 - 04:13 PM

I don't use Sequator, but I think you have some misunderstandings about APP - I just load up all of my (occasionally very complex multi-filter) lights and calibration images, go to the last tab, and click INTEGRATE and let it run. Generally it will produce a nice image that I can work on in other tools and also results in master calibration images.  If there's an issue with the resulting image(s), I may go back and tweak a few settings, then hit INTEGRATE again, and it'll redo anything it needs. Substantial time savings over tools where you need to do things manually in most tools (except Siril with Sirilic which I also use but you would also find unsuitable for your use).

 

It is extremely good at mosaics that I do a lot and they are almost as automatic as other DSO  images. This image for example is three panes taken of M31 which it stitched together perfectly with just a couple of settings changes to put it in mosaic mode.

 

You're using a professional tool to do some very basic/simple things if you're not calibrating your images (not to mention doing them in 5-6 different filters), so yeah, it's going to be more cumbersome and not going to spoon-feed you a result. Sequator sounds suitable for your current requirements, but you may grow into APP.

When you do that, does it run through all the other steps such as calibration, registration and normalization? Or does it just stack them? I'm not sure, but I don't think it does all the other steps. You mention it creates master calibration frames, but what about the registration and normalizations etc...?



#13 gordtulloch

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Posted 19 April 2024 - 04:50 PM

When you do that, does it run through all the other steps such as calibration, registration and normalization? Or does it just stack them? I'm not sure, but I don't think it does all the other steps. You mention it creates master calibration frames, but what about the registration and normalizations etc...?


It does all that.


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