Perkil8r Posted March 30, 2012 Share Posted March 30, 2012 Just been trying a few different stacks of M42 in an attempt to improve on what I already have. Instead of stacking the whole lot I decided to stack shorter subs together to create a tif for the core detail, and then a stack of the longer subs for the outer detail. Even at the unprocessed stage the difference in quality is very strange. Around M42 in the longer stack I have what I can only discribe as contour lines. No matter what I do I can't seem to get rid of them. They also seem to divide any colour in the nebula into bands which looks horendous! In the shorter stack this effect is not pressent at all, and I can get more detail from the shorter exp stack than the longer one, allbeit with a lot more noise. That's not what I want to do, what I am trying to do is get the detail of the main nebula from the long exp stack, then mask and use the short exp stack for the core detail. Any ideas as to what is causing the contour lines and loss of data (or at least that's what it seems to be.) Link to comment Share on other sites More sharing options...
Perkil8r Posted March 30, 2012 Author Share Posted March 30, 2012 Pics to show what I mean, first pair are short exp, second pair long exp. in both pairs 1st is as it comes out of DSS, 2nd is very rough levels and curves to show a bit more of the effect and difference between the 2. Link to comment Share on other sites More sharing options...
Perkil8r Posted March 30, 2012 Author Share Posted March 30, 2012 Having played around all afternoon and night, it seems that the 30 sec exposures are causing it. I don't know why though? I'm leaving it to cool between frames around 20-30 secs and so far have only gone as far as 30 sec exp times. I shoot in RAW format, and save image from DSS as 16 bit TIF tile for processing in Photoshop Cs5 Extended. All the shorter exp time data I had up untill I started with the 30 sec stuff behaved perfectly well. Link to comment Share on other sites More sharing options...
Perkil8r Posted March 30, 2012 Author Share Posted March 30, 2012 Anybody wanting to have a play with one of the RAW files: http://dl.dropbox.com/u/70152981/IMG_6604.CR2 is a single RAW file of 30 secs @ 400 ISO Link to comment Share on other sites More sharing options...
+Graham Posted March 31, 2012 Share Posted March 31, 2012 Hi Mike I have had a quick play with this in Picasa and have got the following result. It is way to big to upload so here is a link to it https://picasaweb.go...feat=directlink I have also attached a reduced version. Link to comment Share on other sites More sharing options...
Perkil8r Posted March 31, 2012 Author Share Posted March 31, 2012 You mentioned about WB being set to manual and that it might be causing it, what should the WB be set to? I seem to remember when I got the camera it was set to "custom" I put it to Tungston for the first couple of nights or so, then switched it back to Custom. I would hazzard a guess and say all of the 30 sec exp were on the custom setting. Do you think this might be affecting it then? Link to comment Share on other sites More sharing options...
+Graham Posted March 31, 2012 Share Posted March 31, 2012 Hi Mike The DSLR set up is my next step so I am not rearly in a position to answer, that will have to be down to someone far better qualified than me. I have been doing some reading on using the cannon and the Tungston setting seems to be ringing a bell in my memory as the one to use. All I can say is when I switched my Samsung to manual white balance I got the same effect as you have been getting. This only became apparent when I put the images through DSS or registax. If I switched it back to auto the problem dissapeared. Hope this helps. Graham Link to comment Share on other sites More sharing options...
Perkil8r Posted March 31, 2012 Author Share Posted March 31, 2012 (edited) Hi Graham, Thanks. I will play with the settings and see what I come up with. Although a quick check just now and the camera is set to tungston. I know it seems to be related to the number and length of the exposures, so guessed it was something to do with the original image rather than the processing, but not knowing a lot I wasn't sure. I think M42 will pass me by now untill winter due to houses and LP being an issue. I'll have to hunt down another relatively easy target to find and image to get some practice in. It's one of those things that is going to take a lot of learning I guess. Mike. Edited March 31, 2012 by Perkil8r Link to comment Share on other sites More sharing options...
+Graham Posted March 31, 2012 Share Posted March 31, 2012 Mike I have all this to look forward to when I finally get my Cannon. It has taken me nearly a year to figure out how to get the best from this Samsung and I am still learning. All good fun. I will ask my mate what settings he uses on his Cannon. best of luck with it. Graham Link to comment Share on other sites More sharing options...
Perkil8r Posted March 31, 2012 Author Share Posted March 31, 2012 Anybody wanting to play with the stack of 50 x 30 secs, 20 x 2.5 secs, 10 x 5 secs, 10 x 10 secs with darks the link is http://dl.dropbox.com/u/70152981/Autosave.tif that's the autosave from DSS. Link to comment Share on other sites More sharing options...
glider Posted March 31, 2012 Share Posted March 31, 2012 Looking at the images out of DSS I can see dust bunnies. Have you used flats? If not then I think your contours are just an effect of you stretching an uncorrected image with low dynamic range. How is the camera attached to the scope, the pattern looks like you have vignetting? Link to comment Share on other sites More sharing options...
Perkil8r Posted March 31, 2012 Author Share Posted March 31, 2012 The camera is direct onto a t-ring and onto the focuser. By dust bunnies do you mean the 3 doughnut type things? I've since done a sensor clean thing from the camera menu. (Meaning I've not taken it apart to clean it as such). I don't have any flats. Tbh I don't really know how to do them. I know about the t-shirt method, but I'm not sure how to get a light source to that even enough for it. I've just had another look at the data myself. I aligned the RGB in dss and then also altered the curves whilst still in DSS. whilst it looked like it was still not quite right, it was a lot better than before. I opened it in PS and had a quick play, and it was a lot better. Maybe I should alter the curves in the first instance in DSS on a fresh stacking of the whole lot so I know exactly what I have there and try again. What would cause Vignetting? Link to comment Share on other sites More sharing options...
glider Posted March 31, 2012 Share Posted March 31, 2012 There are several causes of vignetting, http://en.wikipedia.org/wiki/Vignetting I only balance the colours by lining up their histograms and boost the saturation to 13% before saving as 16bit tiff, with changes applied. Link to comment Share on other sites More sharing options...
Perkil8r Posted March 31, 2012 Author Share Posted March 31, 2012 I was doing that, but it was giving the above results. Tried it with a quick curves adjustment before saing and it seems a lot better. Link to comment Share on other sites More sharing options...
Perkil8r Posted April 2, 2012 Author Share Posted April 2, 2012 Will adding some flats help a lot do we think? If so, what sort of exposure times should I be looking towards for them? I read somewhere that it doesn't have to be the same as the lights, but shorter will do. Is this correct? I realise that I need to leave everything set up before doing the flats, so can't really add them in at this stage of the game, but moving forward I need to improve on things. Link to comment Share on other sites More sharing options...
andyboy1970 Posted April 2, 2012 Share Posted April 2, 2012 Have you put the raw frames in different groups on DSS and stacked them. Link to comment Share on other sites More sharing options...
Perkil8r Posted April 2, 2012 Author Share Posted April 2, 2012 No, Ijust bunged 'em all in together. I intend trying that next. I did make an attempt at a couple of flats. I know they are not "correct" in the fact they were done after the event, but I got things as close as I could to how they were just to try it out. It did make a small improvement though. So moving forward I will probably start over in the winter with M42. Meanwhile I will start on another target. This time taking flats, bias and darks for each individual session. Then stack into groups before finally stacking the stacks. At least I have learnt something from it all. Link to comment Share on other sites More sharing options...
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