Binning and stacking

Discussions of Electronically Assisted Astronomy using the Live Stacking feature.
39N84W
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Binning and stacking

Post by 39N84W » Thu Feb 21, 2019 11:55 am

Using a 294c.
I can successfully stack at 1x1 but not at 2x2 binning. What adjustments should I be making in the Alignments tab? Thank you. Nick

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admin
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Re: Binning and stacking

Post by admin » Thu Feb 21, 2019 4:54 pm

Hi,

Most likely the problem is to do with detection of stars not working correctly at 2 x 2 binning, so that the alignment cannot work. Keep an eye on the number of stars being detected in the alignment tab and while doing that are just some of the star detection parameters. You might need to lower the minimum star width or make other changes. Sometimes a good thing to do is to press the reset button to put all the star detection parameters back to their defaults and then work from there.

If none of this helps, please capture a single frame by using the snapshot button and share that frame and we will be able to look into it further.

Cheers, Robin

39N84W
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Joined: Sat May 19, 2018 4:02 pm

Re: Binning and stacking

Post by 39N84W » Mon Feb 25, 2019 3:52 am

Okay I tried your suggestions. It didn't work.

Attached is a screenshot of what I'm talking about. With these settings I can stack using a 7nm narrowband filter. If I remove the filter and set binning to 2 it will stack. However if I keep binning at 2 and then reinstall the 7nm it won't stack.

What's going on here?
Nick
Attachments
not working, same as 2x binning, with 7nm.JPG
not working, same as 2x binning, with 7nm.JPG (188.8 KiB) Viewed 489 times

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oopfan
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Re: Binning and stacking

Post by oopfan » Mon Feb 25, 2019 2:25 pm

Hi Nick,

You must have a very fast scope to capture anything in Ha with 30s exposures. I take 200s exposures at f/5.9. According to calculators I've used I need to go longer because the signal-to-noise ratio is barely acceptable:

https://astrotuna.com/soul-nebula-in-ha/

Here's another but still a work in progress:

https://astrotuna.com/m101-pinwheel-galaxy-ha/

I know people who start at 5 mins and others who go 30 minutes.

Brian

39N84W
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Re: Binning and stacking

Post by 39N84W » Mon Feb 25, 2019 2:40 pm

I've been doing 30s subs, live narrowband EAA (ha, oii, and sulfur) for over a year with an Ultrastar as well as Lodestar cameras and Starlight Live software. With an on the fly dark subtraction. With a 71mm f6 doublet. In a city. Binning at 2 helps with integration.

Waiting to hear from Robin.... thank you.

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oopfan
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Re: Binning and stacking

Post by oopfan » Mon Feb 25, 2019 2:49 pm

Nick,

Minos images in narrowband with 30s exposures. There may be some helpful info in his post:

viewtopic.php?f=16&t=1124

Brian

39N84W
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Re: Binning and stacking

Post by 39N84W » Mon Feb 25, 2019 4:05 pm

Does the brightness level affect the live stack feature... stacking vs unstacking frames ?

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Re: Binning and stacking

Post by admin » Mon Feb 25, 2019 6:55 pm

Hi,

I can see from your screenshot that the star detection is definitely a problem – in the star detection status area you can see that zero stars are being detected. I suspect this may be because you are using the display stretch features either in the live stacking histogram of the mini histogram to pull up the brightness of the stars that are visible. Neither of these stretches affects the star detection settings in live stacking, so you need to adjust those separately to help it find enough stars to align.

The things that you can do to make it more likely to detect stars are:

Turn down the black level threshold
turn down the noise reduction value
turn down the minimum star width
turn up the digital gain

Also while you are adjusting the settings you should tick the box that says 'highlight detected stars' so you can see if any stars are being detected.

Cheers, Robin

39N84W
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Re: Binning and stacking

Post by 39N84W » Mon Feb 25, 2019 7:00 pm

With the filter on and binning at 1 it stacked.
With the filter on and binning at 2 it did not stack.

Why?

Thanks Robin

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Re: Binning and stacking

Post by admin » Mon Feb 25, 2019 7:02 pm

The most likely cause is going to be your minimum star width of 3 – with the binning applied the stars will be smaller and maybe they would be narrower than 3 pixels so that they would be excluded by this limit.

Cheers, Robin

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