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First go at M81 and M82

SkyExplorer

By SkyExplorer
in Getting Started With Imaging

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SkyExplorer

SkyExplorer

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Well everything just worked last night, PHD2 guided with my QHY5T camera without a hitch.  I used APT for the first time with my 450d, set up a plan and got it to "talk" to PHD so I could using Dithering.

I left the scope outside for a few hours and took 110 x 2 minute images.

Yesterday I also too 180 bias, 100 flats and 2 hours of darks.

So I combined all of these in DSS and stacked them (with default settings, except for Dark Optimisation on)

After a little playing in DSS I ended up with this.

What is the best way to process this image now?  Is there a basic tutorial that explains what you are trying to achieve with "levels and curves" for DLSR images.  Also be good to understand what I am trying to achieve by moving the sliders in levels and curves (I know I am trying to stretch the image) but what does each specific thing do.

Thanks

M81M82_zps6fc405d9.png

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SkyExplorer

SkyExplorer

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Would it both adding my exposures from a few nights earlier to the this image?  I have 63 in total (29 x 60s and 34 x 90s), these were taken without dithering so not sure if they will bring down the overall image quality.

I have some exposures that were effected by some high cloud, you can still see the stars and galaxies, the images just look a bit more orange due to the reflection of the light pollution, are these ones for the junk pile or can they be used?

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SkyExplorer

SkyExplorer

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Well done! I've yet to get a decent image of a galaxy - or a nebula!

How did you get your qhy5t working in the end?

Louise

Thanks Louise,

I think there maybe a dry solder in the QHY5T, yesterday I was testing during the day and it started to show the "white screen" for every other exposure, for no apparent reason (oh I moved the scope).  So I wiggled the USB connection slightly on the QHY5T and it started to behave itself again.

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SkyExplorer

SkyExplorer

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If you have Photoshop you could watch Doug German's series of lessons on You Tube. Just search for him. I found these very useful when starting out. Results or processing in my Flickr link below.

Impressive images Chris.  

How many and how long were your exposures for your M81/M82 image?

I guess it's either photoshop or PixInsight, however maybe photoshop is more versatile as it can be used for other image editing.

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Owmuchonomy

Owmuchonomy

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Impressive images Chris.  

How many and how long were your exposures for your M81/M82 image?

I guess it's either photoshop or PixInsight, however maybe photoshop is more versatile as it can be used for other image editing.

For that image I took 22 x 300 sec lights.  Usual darks etc.  I'm not that happy with it though. I pushed the Ha a bit too much to bring out the core of M82.  From memory I also layered it such that I could pull out M81 separately as it is significantly dimmer than M82.

Kit: HEQ5 pro, AA 102 EDT, 1x field flattener, Canon 60D modded, stacked in DSS and processed in Photoshop (rental version). You can get a 1 month free trial of PS.

PI gets good reviews on here for AP processing and I get the feeling it has a steep learning curve.  I don't have any experience of it so am not qualified to comment. I use the rental version of Photoshop as I also use it outside of AP processing.

Looking at your DSS image it looks like you have plenty of data to go at. Looking forward to seeing the final version.

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SkyExplorer

SkyExplorer

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Having looked at the two options, I think PI is worth a go, I have requested a trial license.  I feel if I have to learn something I may as well learn a tool designed for the job.

Plus it's a lot cheaper than PS when I come to buy a license.

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BenDavis

BenDavis

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Having looked at the two options, I think PI is worth a go, I have requested a trial license.  I feel if I have to learn something I may as well learn a tool designed for the job.

Plus it's a lot cheaper than PS when I come to buy a license.

I've been thinking the same. Start watching those you tube PI tutorials as I have found out this week there's a lot to learn!!

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gnomus

gnomus

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I've been thinking the same. Start watching those you tube PI tutorials as I have found out this week there's a lot to learn!!

I like PixInsight.  Can you do everything you need to do within it, though?  

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SkyExplorer

SkyExplorer

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Just watched a few by Harry Page, so Calibration and Stacking,then "Auto Stretch" the image, crop the image, then Dynamic Background Extraction.

My first go I ended up with a lot of background noise, not sure how to get rid of this though, the M81 galaxy looked pretty amazing, just very noisy.

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gnomus

gnomus

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Had a quick play with PixInsight and have come up with this.....

It has a uneven background and lots of noise, but not sure how to make this better.

Maybe_zpsc56a5961.jpg

There's a tool in PixInsight for "de-greening". I'd give that a try.

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frugal

frugal

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Had a quick play with PixInsight and have come up with this.....

It has a uneven background and lots of noise, but not sure how to make this better.

In PixInsight there is a Script called CanonBandingReduction that will help get rid of some of the banding in the image. It only works on horizontal banding, so you will need to rotate your image, run the script, and then rotate it back.

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glowingturnip

glowingturnip

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might want to try another run of DBE, picking sample points on the greener and the blacker bits of the background.

MLT and TGV for denoising.

colour calibration is off, use background neutralisation and colour calibration.  Then use SNCR if you're still not happy with the green.

you can remove some of the background blotch with MLT too - mask for the background only, MLT set for chrominance,7 levels, turn off levels 4-7 and apply

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SkyExplorer

SkyExplorer

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Hi,

So I take the fit that was created after calibration and stacking and I Auto stretched with STF, the image was green, so I applied SNCR to remove the green and ended up with this blue tinged image.  I then cropped it down a bit.

Should I run SNCR again to remove the blue, or has the green SNCR been too aggressive?

Thanks

SNCR_Crop_zps4b45c91c.png

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glowingturnip

glowingturnip

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SNCR has been too aggressive, imho.  I usually don't apply it until near the end of my processing, and often I leave it out altogether nowadays.

Have a look at Harry Page's Colour Calibration video tutorials, that's what you need to do next - http://harrysastroshed.com/pixinsight/pixinsight%20video%20files/2013%20pix%20vids/ccfinal/ccfinal.mp4

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SkyExplorer

SkyExplorer

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Thanks Stuart,

I have looked at Harry's videos and a set by Jason Brown from utube.   They always seem to use nice "clean" images though rather than a nice dslr image with light pollution.

Do you know what you are trying to achieve with the DBE tool?  I've seen the videos for it, but they just tell you what they are doing, not explaining what the points are for, why you need to add them, etc.

Thanks for your help

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glowingturnip

glowingturnip

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DBE flattens the background.  Take for example your blue pic above, the bottom is quite light, especially in the corners, whereas the top, especially in the middle, is darker.

With DBE, you generate a set of points which represent what should be the true background of the image, then it will fit a smooth 3D surface for each colour channel that fits to each sample point that it can subtract from the image, result being that the sample points after the DBE application should all have approx the same values as each other, and everywhere else has been adjusted in a nice smooth fashion inbetween.  In short, it will set the background to a uniform level, removing any vignetting, gradients etc.

A few points to remember:

- make sure the points are only on true background - delete any that fall on faint nebulosity, outer arms of galaxies, etc.

- make sure none of them fall on stars (good way to check is to do a stretch of the background model it generates - any white patches on that could be because a sample point has fallen on a star, so check the ones in that area and move if necessary)

- I usually run it 2 or 3 times - after the first time, check the 'normalise' checkbox so that it doesn't get darker and darker each time.  I do a wild stretch so I can see where any darker or lighter background blotches are and add a few more sample points to those areas, as necessary.

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