Live Stacking Beginner help

Discussions of Electronically Assisted Astronomy using the Live Stacking feature.
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turfpit
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Re: Live Stacking Beginner help

Post by turfpit » Fri Sep 21, 2018 8:33 pm

Don

Thanks. I was were you are now about 18 months ago and asking the same questions, then a few things started to fall into place. Its all about the histogram at the end of the day.

https://docs.sharpcap.co.uk/2.9/#Using% ... 20Stacking
was only using the brightness/contrast tool and curves
My usual route is curves/levels repeatedly to extract the image, then satuaration, brightness/contrast, black level/exposure. Here there already was an object, so nothing really to dig out plus when I went into curves the histogram had vertical lines (gaps). I take that as the image being stretched to breaking point and will only deteriorate after that. This was from the book Photoshop Astronomy by Stephen Ireland (not cheap but very informative).
resigned myself to studying the GIMP user manual
None of the examples are really targeted at Astro images, what I did was to find out how to do something in Photoshop and translate it to GIMPish. With a better understanding of processing, I can manage within GIMP entirely. I am at the point of stopping my Photoshop subscription.
you also changed the output level to 60
Oops! I must have caught something switching between Gimp, Word and the Snipping Tool. I have rerun my notes and 0 is ok. keep is simple.
"scaling" and "re-sizing" an image
The same thing. Size is a personal thing, which really comes about by experimentation. With 700x500 there has to be compromises and trade-offs. I always go for 'looks better'.
At least if I can properly center the image
I used to have a Nexstar 6SE so I understand where you are coming from. I used to carry out the initial alignment using finderscope + eyepiece. As confidence (ability) grew I started using finder scope + camera. I turn on the reticule in SharpCap that way I am not guessing where centre is in the FOV. I also noticed that changing optics from eyepiece to camera resulted in centre being shifted. I now align using the optics that I will be imaging with i.e. camera + focal reducer (for example). When I am aligned, I stay aligned. Best to practice this on partially cloudy nights.
beautiful image of M27
I didn't know I had a beautiful one, must have been lucky that night. Where is it?
Would you recommend saving the SharpCap live capture as a RAW FITS file and use other software for further processing (e.g., Deep Sky Stacker, Nebulosity), or using the tools in SharpCap and saving the as viewed png file as I did
My view is that with the single PNG, if something goes wrong, then there is nothing. My personal preference is save the RAW frames and save the stack. That gives instant gratification and some data to practise with for stacking and processing. I am very much of the mindset 'capture data and take it away to process'. For me Sharpcap is for capture and Nebulosity etc are for processing. I mainly use Siril now for calibration & stacking with GIMP to process.
picture appears rotated
To be honest I never really bother about orientation, just grateful to get something on the sensor. You can upload your image to astronometry.net to have a look. For me correct orienation will be part of my evolution.

BTW, I use a Bahtinov Mask for focusing - best £20 I ever spent.

I will not edit the document yet, wait to see if there is any other feedback - I did write it fairly quickly (< 3 hours, untested and not proof read, which is pretty shoddy by my standards). If the document turns out useful to others, it might end up being put in the Tutorials forum (Robin might have a view on that?).

Dave

donstim
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Re: Live Stacking Beginner help

Post by donstim » Fri Sep 21, 2018 9:18 pm

I was referring to your M27 image here: viewtopic.php?t=297&sid=2a146e59dcc4c8a ... f6b6b109cb

I didn't realize SharpCap has a reticule. I will have to start using that. For alignment, I start with using the GoTo function for the aligned scope, then center the object in a wide FOV eyepiece, switch to an eyepiece with a similar FOV to the Imager, center that, then switch to the imager. If I have good scope alignment, I can skip using the wide FOV eyepiece. I find it somewhat difficult to make alignment adjustments in SharpCap with the imager because: 1) there is a delay between slewing the scope and when you see it in SharpCap; and 2) the slew direction is not always what is expected (which I assume is due to the orientation of the imager in the diagonal).

I will look into getting a Bahtinov Mask. Even with the focusing tool in SharpCap, focusing is not easy. Do you have a view on whether an add-on fine focuser is worth it?

Just to be a little more complete on what I used for this image in addition to what I state above -- I used the 0.5x focal reducer and UV/IR filter supplied with the Revolution Imager 2. My backyard night sky is not all that dark and there was a Gibbous moon that was fortunately not too close to the nebula. I have a DGM NTB nebula filter, but did not try using it for this image. (I wish I had, though I don't know if there would have been a significant difference.)

Thank you again for the hours you spent on this. I hope it ends up helping many others besides me.

Don

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turfpit
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Re: Live Stacking Beginner help

Post by turfpit » Fri Sep 21, 2018 9:46 pm

Ah that one. Note the histogram in that post - that is what to aim for - logarithmic setting.


Reticule here https://docs.sharpcap.co.uk/2.9/#Reticule%20Overlays
orientation of the imager in the diagonal
I always put the camera into the telescope with the same orientation. That way, no surprises with slewing directions.

Do you have a view on whether an add-on ... worth it?
On my Celestron C8, I have a JMI MotoFocuser, excellent for hands off focusing. My Altair Lightwave 66ED comes with a 10:1 dual focuser. The fine focus is very helpful for those final adjustments. For imaging M27, I would focus on Altair, then slew to M27 - minimal travel, less chance of any mirror flop or flexure. I use the Bahtinov and the Zoom tool to get from Auto to 100 or 125%. The final image will only be as good as the focus, so time spent here is not wasted.
I used the 0.5x focal reducer and UV/IR filter
I always use an IR filter with a smaller camera - I found it cuts down star bloat. With the Altair 183C the better sensor (= more ££££'s) negates the need for the IR cut filter.

Additional material I have included in the doc is about Saturation.
GIMP-saturation.PNG
GIMP-saturation.PNG (128.56 KiB) Viewed 1061 times
The time spent on the document was worth it - I learnt/clarified something for myself by writing it.


Dave

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turfpit
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Re: Live Stacking Beginner help

Post by turfpit » Sun Sep 23, 2018 10:00 am

Don

After sleeping on this one, here is some more information that might be useful to yourself and others. I have really only just started to get a handle on this part of image processing - the M52+NGC7635 image was captured about 3 weeks ago.

See my Astrobin https://www.astrobin.com/365064/D/?nc=user and
this forum post viewtopic.php?f=16&t=1085.

The Astrobin entry contains 4 revisions. These are 4 attempts at processing the same stack - 60x60s which were calibrated, registered & stacked using Siril, the resultant stack being processed in GIMP 2.10. Thanks to the kind 'nudging' of Brian (@oopfan) and Minos (@mAnKiNd) - cheers Gents - you can see how the same stack was improved. Don't worry, they are not a pair of forum bullies, we have had some fairly deep and robust discussions outside the forum about how to acquire better data and improve processing techniques. I think that has pushed all three of us on.

Here is a summary of the histograms resulting in 4 different attempts to process the same data stack.

histogram-revisions-for-M52+NGC7635.PNG
comparison of histogram for 4 processing revisions
histogram-revisions-for-M52+NGC7635.PNG (152.41 KiB) Viewed 1048 times

Dave

donstim
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Re: Live Stacking Beginner help

Post by donstim » Mon Sep 24, 2018 6:47 am

Dave,

Well, that's way beyond where I ever expect to get to! I am more interested in EAA and saving good images as photos than getting deeply into actual astrophotography.

One of the main lessons I think you are trying to convey to me is to really pay attention to the histogram to get the black/white levels and colors right (assuming the shot is well focused and aligned properly in the FOV).

Why do you use SIRIL, and what type of file do you capture/save with SharpCap -- a SER video or a series of FIITS frames for stacking with SIRIL?

Don

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turfpit
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Re: Live Stacking Beginner help

Post by turfpit » Mon Sep 24, 2018 9:23 am

Don
I am more interested in EAA and saving good images as photos than getting deeply into actual astrophotography
Yes - slightly different approach for EAA only
really pay attention to the histogram to get the black/white levels and colors right (assuming the shot is well focused and aligned properly in the FOV)
You are then now once all that is realised - keep practising, it does take time.

I have used Nebulosity a lot - it is a good program. I stumbled across Siril by accident, what impressed me most was the excellent documentation provided with the software, the multi-os offering and the online training.

https://www.siril.org/ docs at https://free-astro.org/siril_doc-en/#Re ... umentation. You will like the M27 on the front page of the doc.

Very traditional imaging for me - I use Sharpcap to capture FITS, Siril for calibration, registering and stacking then GIMP to finish off.

For lunar planetary - SharpCap then Autostakkert, Registax, GIMP. Siril has the capablity to carry out the functions provided by Autostakkert and Registax but I haven't delved into this area yet.


Due to some interest shown outside this thread, I will write up the above notes into a document to place in the tutorial forum where it will be more visible. Am I ok to use your image for the example and give you recognition in the doc? As you have a good eye for detail, perhaps you can test the doc when it is uploaded.

Dave

donstim
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Re: Live Stacking Beginner help

Post by donstim » Mon Sep 24, 2018 9:19 pm

Dave,

Yes, that would be great if you could write up the notes and put them into the tutorial forum. Feel free to use my image and and who's to blame for taking it! I would be glad to go through and give a test use to the document when it is uploaded.

Another very basic question -- You said you used SharpCap to capture FITS for your 60x60s exposure. Do you do that all at one time, i.e., have SharpCap auto-save every minute for an hour, or are some of those exposures done at different times? If they are at different times, how do you ensure your alignment is the same each time?

My first attempted captures were of Saturn and Jupiter using SharpCap to capture 1000 or so frames in a SER video, then stack and adjust wavelets with Autostakkert/Registax. Was not satisfied with the results (no real detail in my images), which I'm not sure whether that was due to inadequacy of the camera, poor environment for imaging (both planets are pretty low in the sky at my location and set pretty early), or just plain ineptitude of the user. I didn't use the focal reducer for the planets, but I still wasn't able to capture any detail to bring out with Registax.

I tried taking a few photos of the full moon last night, but haven't tried to do anything with them yet. Just took a few "snapshots' since there doesn't seem to be much point in needing to stack frames. Used the focal reducer, but the area covered is still pretty small. With a full moon, I would rather be able to take a shot of the complete moon.

Don
Last edited by donstim on Tue Sep 25, 2018 3:51 pm, edited 1 time in total.

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turfpit
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Re: Live Stacking Beginner help

Post by turfpit » Mon Sep 24, 2018 10:42 pm

Thanks for that Don. I will link back from here once uploaded.
used SharpCap to capture FITS for your 60x60s exposure. Do you do that all at one time
Yes from the Capture Menu, just specify the number of frames. I have a Celestron AVX equatorial mount which tracks, so no issues with field rotation.
using SharpCap to capture 1000 or so frames in a SER video, then stack and adjust wavelets with Autostakkert/Registax
That is the usual process.

Some pointers to help you
viewtopic.php?f=7&t=211
viewtopic.php?f=16&t=736
viewtopic.php?f=16&t=256
http://docs.sharpcap.co.uk/howtos/jupiter/

My first Saturn took 3 nights to get on the camera chip.
saturn.PNG
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Dave

donstim
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Re: Live Stacking Beginner help

Post by donstim » Tue Sep 25, 2018 2:10 am

Thanks Dave for posting pointers to your tips on getting good planetary images. I'm sure that will help a lot.

Here were my first attempts at Saturn and Jupiter. A little overboard on the sharpening I think, but I was trying to find at least some level of detail. There are major differences between what you posted in this thread (your first Saturn pic) and what you posted in the first linked thread. Were they from the same camera and telescope?

Saw the thread where you did a mosaic of the full moon. Very nice! I will have to try that!

Don
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Re: Live Stacking Beginner help

Post by turfpit » Tue Sep 25, 2018 3:26 am

Don

The planets in the first link were captured using a ZWO ASI120MC. Any of the £150 cameras should be capable of this. I was using a 2x Barlow lens to 'zoom in'. Planets tend to come out well at 640x480.

The first Saturn was Nexstar 6se plus Celestron Solar System Imager. The other images are all Celestron C8 on a CG5 mount.

On the moon mosaic, Robin liked it so much he has it in the gallery on the SharpCap website. It proves useful things can be done with a small budget. I have the material to write that one up as well.

This is my big mosaic https://www.astrobin.com/343145/?nc=user click on the full resolution button for best effect. Looking at the histogram for that I need to reprocess it.

If you keep old images, then as you learn about the processing techniques go back over and improve them.

Dave

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