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coma galaxy cluster


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Hi everyone

Set for all night, alas curtailed by haze from the onshore -damp- easterlies with about 3 hours of darkness remaining:(

Thanks for looking and do post your dslr examples if you've had a go at this.

700d on pn208:  ISO800

1185342850_1-4889(1)_01.thumb.jpg.214e12eb52380726d415074f57a0c7eb.jpg

 

Edited by alacant
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Very nice. I started imaging this again last night with my dual rig. I lost 2 and a half hours due to falling asleep just before doing a focus check so the scope just followed the target without taking any images.

Hope to carry on collecting data tonight.

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@alacantSo I followed through after you pointed me in the direction of the galaxy cluster. Here is my capture from last night using a 61mm 275mm FL scope and astromodified Canon EOS 550D with no filter 36x240 seconds. APP for stacking and to get rid of gradients and light pollution and StarTools1.7 for finishing.

Coma_Galaxy_Cluster_WF-lpc-cbg.jpg

Edited by Avocette
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Posted (edited)
2 hours ago, Avocette said:

StarTools1.7 for finishing

Lovely shot. There are certainly many non stellar light sources. Well done.

Please note that you cannot use StarTools to advantage with anything other than linear data. By pre-processing, you removed a lot of its power. Starting from a linear stack, you'll probably find e.g. StarTools' Wipe module does a far better job on gradients than app, and with the unique advantage of retaining your data in a linear form throughout.

Cheers

Edited by alacant
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4 hours ago, alacant said:

Lovely shot. There are certainly many non stellar light sources. Well done.

Please note that you cannot use StarTools to advantage with anything other than linear data. By pre-processing, you removed a lot of its power. Starting from a linear stack, you'll probably find e.g. StarTools' Wipe module does a far better job on gradients than app, and with the unique advantage of retaining your data in a linear form throughout.

Cheers

So far I have found the StarTools Wipe module less effective than the APP tool for light pollution and gradient removal. APP’s tool requires much manual intervention. For this image I carefully drew 80 or so pixel boxes of various sizes in places where my eyes thought there was no specific stars, galaxies or nebulosity. I agree that once you’ve done something of that nature StarTools can no longer track the noise for definitive removal, but for this kind of image I think it didn’t do a bad job! If Ivo reads this and disagrees, I’ll stand corrected!

I have found that my 550D doesn’t have fully even illumination and there is a strip at the bottom of every image (i.e. top of the sensor) which has a different contrast and brightness from the rest. So in the image above I couldn’t correct it, and ended up cropping. I’ll make a new posting on the subject.

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Posted (edited)
10 hours ago, Avocette said:

my 550D doesn’t have fully even illumination

Hi

The flipped up mirror will cast a shadow on all mirror eos' at anything wider than f6-ish. Flat frames cancel it though.

10 hours ago, Avocette said:

it didn’t do a bad job!

If you wish, post -a link to- your linear data.

Cheers

Edited by alacant
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Thanks! I had assumed that it was due to the position of the closed up mirror, also emphasised because in this image, the magn 4.3 bright star rho Virginis is just at the bottom edge of the image, and shows a bright diffraction spike due to the mirror straight edge I presume. My scope is f4.5 so that ties up with your explanation.

The fact is I’m struggling with Flats so your suggestion makes me more keen to sort them out. I have made them in the past using a white image on my iPad screen with SharpCap Pro. But more recently I bought a 30x30 cm square LED panel intended for room lighting, not special purpose, and it’s rather bright and since then I seem to have lost the plot. I know Flats are important for dust doughnuts and suchlike but I was guessing it couldn’t do anything for the ‘shadow’ as you describe.

I tried shooting Flats with Ekos but the KStars Fits Viewer histogram confused me and I gave up..... for the moment anyway.

I’ll put in some serious effort and have another go with Flats and Dark Flats.

 

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54 minutes ago, Avocette said:

struggling with Flats

Check there are no bright spots on the panel; take a shot of it from close range using a kit lens as per the camera's own exposure calculation. 

With your eos set at Av, place several sheets of paper between the light panel and the telescope aperture until the exposure reads at least 2s. Return the camera to M and use EKOS to capture say, 20 frames at that same shutter speed 

To avoid confusion with your light frames, set the capture type to Flat in the same tab. That way, the folder names will be self explanatory. 

Lose any dark frames, dither between light frames and stack using a clip algorithm having processed the light and flat frames with bias. I'd recommend Siril to do this.

HTH

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I've actually just set up the 10" Newt with my unmodded DSLR (for field of view) and taken my first of 50 x 180 sec subs on the Coma Cluster.

I'm hooked! :)

image.thumb.png.c49f67076bcaad9fe3b7d8d00abf1a91.png

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Hi, here's my attempt at the Coma cluster. ISO800, 3min subs, ~ 1h imaging time.

I'm struggling with PEC at the moment, so only ended up with 1h of usable images out of about 2.5h 😞 so it's a lacking in as much 'data' as it should have achieved! PEC training on the HEQ5 is a bit of a joke (well it is when you're doing it by eye) to be honest. Looks like I'm going to have to invest in a guide camera at some point...

It's a fantastic target though, thanks for highlighting this one. Many years ago I had a favourite poster of a galaxy cluster from the HST. They really are mind blowing huh!

Cheers,

Rob

Coma cluster.jpg

Edited by Robculm
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On 09/04/2021 at 23:01, Avocette said:

So far I have found the StarTools Wipe module less effective than the APP tool for light pollution and gradient removal. APP’s tool requires much manual intervention. For this image I carefully drew 80 or so pixel boxes of various sizes in places where my eyes thought there was no specific stars, galaxies or nebulosity. I agree that once you’ve done something of that nature StarTools can no longer track the noise for definitive removal, but for this kind of image I think it didn’t do a bad job! If Ivo reads this and disagrees, I’ll stand corrected!

A bit late to this discussion, but I think providing you save the image as a standard background corrected tiff file, the data remains 'unstretched'. Yes it has been modified, but no more than using flats or bias frames. I use the APP background correction before working in Startools or other software for exactly this reason. (Depending on the image this could be each channel individually or the combined RGB).

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