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First Light for Star Adventurer, M31 :-)


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Good evening all.

Well the SA arrived this morning and following an early evening of what looked to be perpetual cloud, I stepped outside at 9:30 to find clear skies. 

I pratted about rolling around on the floor for 20 minutes trying to get PA before finally starting shooting.

 

I used the optional counterweight etc so that I could still see through the polar scope.

Nikon D810 with Nikkor 70-200F4, at F4 with 2 minute exposures @ ISO800. Also took 10 darks and 20 bias.

out of 11 lights, 7 frames were of reasonable quality, I used DSS to stack the best 5 of these and then did some (admittedly poor) post processing in PS CC and Lightroom. 

 

Considering ive only spent 20 mins or so stretching this (and in all honesty I can do no better), and then using a mask to underexpose some of the surrounding area to rid the noise from the LP, I am made up with the result.

 

In order to make the stacking quick I also cropped heavily before any stacking (1900 x 1200 pixels approx).

 

Would love to post the data somewhere to see if anyone of you wizards can pull any more from it, any takers?

 

Comments always welcome :-)

 

 

STACK4 MEDIAN edit.jpg

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wasnt too bad I dont think, definitely needs to be better at this focal length though. it was 200mm at full frame but with this crop its almost effectively 800mm I think... (1920 pixels on long edge occupies 9.3mm of sensor length), or is that 400mm? 

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That's a very nice first result.

To improve the quality of the image, you really need flats. Once you have an even background, you may try

If you stop the lens down, it will have better optical properties, but also diffraction spikes. If you don't like the spikes, make a diaphragm from black paper/plastic, and put this in front of the lens.

If you put the DSS autosave.tif in dropbox, or attach it to a post, I can try cleaning up the background for you. Just post a link here, or PM me.

Cheers

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That's a great 1st image, well done. especially at 200mm your PA must have been pretty good worth the contortions to get it. A right angle finder is a great help on the camera viewfinder saves a  lot of backache.

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Here's a roughly processed version of your image. Just to show what was hiding in the light pollution.

STACK4 MEDIAN.jpg

I removed the background gradient, which was part vignetting and part sky glow. Then I did a rough noise reduction, followed by stretching (level stretch).

Also some HDR processing to reveal a little more detail near the core. Colour saturation using a lightness mask, followed by some star reduction. Topped off with more noise reduction.

To improve, you will need to start adding flats to the calibration process and take many more light frames. I think you can aim for maybe 50 light frames and try to stack all.

Images taken under light polluted skies will always be noisy after removing gradients and doing a colour calibration. The only way to minimize this noise is to add light frames.

Your lens has some chromatic aberration and coma, but you can minimize this by stopping it down one or two steps. (Use a black paper or plastic sheet with a ca 35 mm diameter round hole cut out, if you want to avoid diffraction spikes.)

I also add the background corrected and colour calibrated tiff for you to process further.

STACK4 MEDIAN_DBE.tif

Cheers,

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Wow, thanks very much! 

can I just ask what you used to remove the back ground gradient?

 

Im worried about stopping down despite its obvious gains due to the relatively short exposures Ill be taking. I am looking forward to doing some real wide fields with the 14-24 mind which is supposed to be very good even at F2.8.

 

Thanks again

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I use PixInsight for processing. If you use photoshop, you can use Gradient Xterminator.

If you stop down your lens, you can still use 2 min exposures, if you increase iso to 1600. Your camera should be able to handle that, noisewise. Just increase the number of exposures to subdue the noise.

Edited by wimvb
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Yes. € 230 but I consider it one of the more important pieces of my equipment. If you're serious about astrophotography, it's worth every cent of that price. There is a 45 day trial license. An alternative to PixInsight is PhotoShop, which has a subscription plan that is cheaper short term. But for AP, you will also need to buy some plugins, I believe. PhotoShop can't do stacking, so you'll still need DSS or an alternative for that. PI has everything you'll need in one program.

Hth,

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