M57 - my first serious attempt at DSO AP - any comments and tips would be much appreciated

[Adrian23]

Here is my 1st serious attempt at DSO AP (using my new kit - a SW 80ED DS Pro on a VX mount coupled to a Canon 500d DSLR). I don't know if M57 is the best target for a newbie but it just seemed to be in the right place at the right time for me. I tried posting this yesterday elsewhere in SGL - guess I chose some backwater of the site that no one visits as I've yet to have any replies. I'm sure someone can help guide me -

Any tips or comments would be greatly appreciated as I'm really keen to climb this steep learning curve that is DSO AP.

Here's a little background info to help you evaluate my effort a bit better:

• 10 x 60sec unguided lights (in my eagerness to start imagining I neglected to follow the ASPA routine for a really accurate polar alignment which is why I kept the subs to 60 secs; will certainly use ASPA next time to hopefully push the lights exposure time up a notch...)
• 10 x 60sec darks
• 5 flats
• 5 bias
• stacked in DSS
• levels adjusted in GIMP

I have had to heavily crop the final image to upload it to SGL (limited to 1Mb max)

One problem I DID encounter which someone might be able to help me with: I had real problems restoring any colour to M57 after the stacking in DSS. I tried following Steve Richards' really useful section on post-processing in "Making Every Photon Count" but no matter how I tweeked the saturation using GIMP, I still could not get much colour back (each sub of M57 was a vivid blue). In the end, I started again in DSS and boosted the saturation there before moving on to GIMP to adjust the levels. Any ideas on how to bring back the colour in GIMP? As I understand its best to do all post-production away from DSS, or have I got that wrong?)

Really looking forward to your helpful comments and tips everyone...

Adrian

[PhotoGav]

Well, first off, I think that is a remarkable result for such a tiny target with the kit that you have! You are obviously suitably crazy to go very far in this AP challenge.

There is some trailing in the stars, so you really should try and get a more accurate polar alignment. Well worth spending time on that bit of the set-up process. Make sure that everything is good and level too. The best solution to star trails is guiding, which I have no doubt you will get into very soon anyway. Definitely the way forward with DSO imaging and, while complicated, is not difficult.

Processing wise, that's really not a bad effort. I think you are probably going to struggle with such a small target in the field of view. I suggest that you go for something much much larger next time. Cygnus is starting to climb ever higher now and is full of gorgeous nebulosity that the ED80 and DSLR will be perfect for.

In all, longer subs with good PA and / or guiding will start to give you good data that will be easier to process.

Great start though, well done, and enjoy the painful climb up that learning curve!!

[jambouk]

First of all, lovely result!

Did you use a light pollution filter?

There is a setting in DSS where you can tick a box to "auto align RGB" which can correct some of the colour distortion when using a light pollution filter and may work even when not.

I agree, tighten up your polar alignment, and even if you don't want to guide yet, just do hundreds of 60 second subs

I thought the dslr did bias frames for you, so maybe spend this time doing more darks and more flats, or just collecting more data. What iso did you use?

But a lovely first go.

Jd

[Adrian23]

Thanks guys for your encouragement and helpful tips. I shot at ISO 800 so that I didn't get too much noise and didn't use a light pollution filter. I took some test shots at longer exposure lengths right up to 180 sec just to see the limitation of my unguided kit. 180 sec produced really noticeable star trails even before I zoomed in for a closer look (I guess accurate PA would help this). As for light pollution here in Rotherham, the image was extremely orange. Even at 60 sec there was a noticeable LP tinge but DSS seemed to do a fine job of getting rid of this.

I will have to check my user manual to see if the DSLR takes bias shots for me, although they are the easiest of all the calibration shots to take so it would be easier to take a lot more. On the night I was soo eager to get "some" results, all my reading on the subject seem to go out the window. I'm sure I'll be a lot more level headed next time, and follow all "the rules" (or most of them, anyway).

Sounds like Cygnus will be my next target then, although that will mean I will have to sell more of my sole to "the dark side" that is AP post-processing! See you on the other side guys :-)

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[Guest]

Hi,

When stacking id DSS, after the stack has finished tick the box that says "embed changes but do not apply them" then you will have all the origional data there to work on in PS, if you apply the changes you can lose a lot of data and colour from the image and can look quite greyscale.

This maybe what your problem is, as I had a similar problem and this works.

MM

[JulianFR]

I know NOTHING about the techniques of astro-photography but I love M57 and I really like your image. Wish I could do that. Thanks for sharing.

[todd8137]

Great first attempt at least you now no how your kit performs for next time for a un modded camera ,so next time more data

Pat

[Adrian23]

Thanks MagnaMan - I will try that next time. Do you tick the box in DSS WITHOUT making any changes whilst in DSS, just doing all the manipulations in PS/GIMP?

JulianFR - many thanks for your encouragement. Always good to hear I'm gradually getting there :-)

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[Adrian23]

Thanks too Todd8137 - definitely more data next time!

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[wxsatuser]

It's a tiny target, not easy for a small scope.

Thats not to bad for 60sec subs, for much longer you will want to guide.

A decent LP filter will help for longer subs as well.

As to colour.

Your sky brightness will determine the exposure length, sometimes 60secs will

be the limit and sometimes it will be possible to go as far as 20minutes or more, if you guide.

Don't be tempted to over expose as colour will be lost, the longer you expose the more to white

everything will appear, once clipped it ain't coming back.

Colour can be added later but thats another story.

The correct exposure for a dslr, for the sky brightness is around the 25% in camera histogram mark.

You can give and take a little either way but 25% will get the data out of the read noise but should not clip any data.

[Adrian23]

Thanks wxsatuser - I'll try and take your suggestions on board.

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[Guest]

Thanks MagnaMan - I will try that next time. Do you tick the box in DSS WITHOUT making any changes whilst in DSS, just doing all the manipulations in PS/GIMP?

JulianFR - many thanks for your encouragement. Always good to hear I'm gradually getting there :-)

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Just do your normal stacking routine, at the end I do nothing just tick that box and send to PS or whatever you use, anything that you do in DSS won't be saved anyway as your just embedding the changes but not applying, if you wan to play around with the stuff in DSS just to see what your image is like roughly then go ahead, but those changes will be lost when exporting using the method I described, then you can use a dedicated programme for all the editing, as DSS is very very basic to say the least.

Also any changes that occurred during the stacking, which is usually unwanted in my experience, will also be lost too, so basically all you are doing with DSS is stacking the images and NOTHING else.

Hope that helps a little.

MM

[Adrian23]

Thanks MM - that's clarified that point well.

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