First go with new scope, DSS advice

[MikeMc]

Hi all,

After some initial problems I now have my new setup (see signature) and I am well happy!! Some fantastic sites and I have only been out 3 times :-)

I took my very first pictures last week (a mix of 15, 20 and 30 sec subs @ 800 ISO) the best single sub (15 secs) shown below, any advice or comments welcome.

My question is why is the DSS stacked image so 'grey', the Moon was up by the time I found M57 and the sky was quite light so this may have had an effect on the final image but the individual subs are all darker?

9 usable lights at 30sec and only 4 at 20 with 20 Darks and 20 Bias (although all my darks are 20 secs - does this matter?)

Given this is my very first go I think a slightly bigger target may have made sense.

Any suggestions,

Many thanks,

[VigdisVZ]

Hi

The images in DSS always look wonky until you stretch the histogram properly.

There seems to be a lot of information in your image so I think it may just be a matter of learning the quirks of DSS.

http://flintstonestargazing.com/2009/06/26/my-quick-deepskystacker-tutorial/ Start here and see if you can find something useful.

[Stargazer33]

Hi,

Your single frame looks good. Not the easiest of targets to start with!

I am new to this imaging lark myself, but I think as dark frames are taken to eliminate camera noise, I would take them on the longest exposure used for the lights. So in your case 30". If you are getting noise effects appearing at 30" then you will miss them if you do your darks at 20" and they therefore will not be subtracted from your final image during processing.

I've also never understood why my dark sky images always come out light grey in DSS!

[LukeSkywatcher]

The image on the left really is pretty good. The Ring is a small target and you would not have been helped by the fact that the Moon was up. I can only say to you to try even shorter exposures (less then 15 seconds) and take many of them.................as many as possible really. Then stack them with DSS. Also play around with the ISO setting. With my camera (same as yours), i find the best settings i can use and end up with a black sky and bright stars etc is ISO 800 @ 8 seconds. Thats due to light pollution etc where i live. Every location is different.

As it is, i also think there is a lot more data/detail to be dragged out of the image using an imaging package such as Photoshop or Gimp. Its just a case of tweaking the levels. I am not an imager by any stretch of the imagination so my advice is pretty null and void. I just know how to do a couple of tweaks here and there so that i arrive at an image that i am happy with and that is all that counts.

Paul.

[ronin]

Very likely the camera settings. Oddly they are not Black and White but operate on a grey scale.

Point a camera at a white wall or a snow scene and the result is a shade of grey, to get white from a white wall you need to adjust the white balance.

If you go to a wedding you need to do the same so the brides dress comes out white and not looking a bit grubby and as if it needs a good wash.

[MikeMc]

Thanks for all the advice, I will look at the White balance and start some reading on post processing. I didn't want to go too far without knowing if the grey DSS image was 'normal'. The single frame also seems to have suffered in the upload as the jpg on my PC is fine but the upload seems to have artefacts? Thanks for the web link too. I think I'll try a bigger target next!

[Neeken]

Just another tip, if you have a powerful enough computer, you could try and use 2x Drizzle in DSS since the ring nebula is such a small target. You do have to select a smaller area on the image within DSS to be able to use drizzle without getting an error after it's done processing. (Just by dragging over the preview image after loading in the lights, you get a red box whilst holding down and dragging where it says how big your crop can be with 2x drizzle.)

I took this whilst the moon was up a few days ago, without tracking/guiding. Used 2x Drizzle in DSS from 100 ish subs. Not the best of course, since I don't have tracking. I just wanted to test the drizzle option..

[ollypenrice]

The fundamental skill in DS image processing is the use of Levels and Curves to stretch and de-noise the image effectively. Without this skill you are totally lost and DSS is not the place to do it. The original tool was Photoshop, older CS3 versions of which are not ridiculously expensive. You can, I think, do it in GIMP and certainly in Pixisight. For an introduction to Levels and Curves try this one by Rob Hodgkinson, whose images need no comment from me. http://www.middlehillobservatory.co.uk/articles-primers/Levels%20and%20curves.htm

Trust me, read up everything you can on Levels and Curves. Get this wrong and there is nothing much you can do to rescue an image.

Olly

http://ollypenrice.smugmug.com/Other/Best-of-Les-Granges/22435624_WLMPTM#!i=2277139556&k=FGgG233

[MikeMc]

Nice one thanks Olly,

I have just had a quick go at the levels (moving the mid point slider slightly right in RGB) and curves (no idea what as going on in there :-)) I also tried the drizzle x2 too but my results were still better on a single sub rather than the fully stacked DSS version?

I'll upload the best results once I have a bit more time to have a play

Many thanks once again and it's a good job I enjoy the challenge and learning curve as figuring the EQ mount, polar alignment, my first scope, the camera and post processing is really going to keep my busy!

[ollypenrice]

Moving the levels midpoint to the left is 'stretching.' It gives you a pure logarithmic stretch and for starters that is fine. In Curves you can do the same thing, more or less, but shape the stretch differently, maybe stretching the faint signal by much more than the bright. Don't run before you can walk.

All good fun!

Olly

[MikeMc]

Again the same pics as above (single sub and a stacked version) but now with some very basic stretching and messing with the levels and curves. I seemed to have got slightly better results by moving the black spot (far left in levels) to the right to remove 'empty space' in the histogram and then playing with the middle slider.

I think the colour in the single sub is better but the bottom of the frame seems to have some bad noise, the stacked version is slightly more uniform but seems to lack colour as does the drizzle x2

I have kept my data so I may well go back to the beginning and re stack after doing some more reading.

thanks all for getting me started!

[MikeMc]

Sorry I don't know what happened to the pics but here they are again,

[ollypenrice]

Yes, moving the black point slider to the right gets rid of noise in the background sky. The usual beginner's mastake is to cut back too harshly and so irrevocably remove faint but real data. Always leave a little flat bit on the left and use the colour sampler tool in Ps, if you have it, to measure tha background sky. Something like 23 in all channels is good. Less is likely to be clipped. Some like blue to be a little higher though personally I don't.

Olly

[MikeMc]

OK thanks for the quick intro, this is the best I can get so far.

To be honest I have seen so many images and histograms now I can't tell what's best!

Also how do you guys manage all the images, I must have LOADS of various attempts at just this shot which all have to be named so I know what process I have applied to each!?

is this one any better?

Thanks,

[MikeMc]

central star!

[MikeMc]

Hmm, there is something about the previous one I posted at 1:02 am .... I assume it all subjective?

[MikeMc]

what do you people use to convert to jpg?

You work all this time and effort on TIFF and RAW images and then convert to JPG to upload here!?

I don't get it?

Mike

[Chris-B]

Nice start mike, similar to my first go at the ring neb. The guide vigdisVZ posted earlier is what i have been using as gospel, small changes in the dss histogram seems to make a huge difference. If you can upload the original .tiff somewhere, maybe the pros will have a go at extracting the best info from it.

[Chris-B]

jpegs are needed for the 1mb limit! I just resize and save as .jpg in photoshop