DSS Software Question

[Langy]

I watched the video on YouTube at http://www.youtube.com/watch?v=e0JSTF8SGi4&list=WLpWIx6AVA0qogAX0syRenFPf3pGFWEB6K which gave me an idea on going out an capturing some of the distant starts without using a Telescope.

My first attempt worked reasonably well as per the Orion Nebula image that is in my gallery and a previous post.

So last night I decided that I would try a wide angle lens to capture more of the sky and hopefully show a lot more stars. Now I live in a small town and therefore get a bit of the dreaded LP. However when I'm in my small postage stamp back garden near to the house you do get quite a bit of cover and the southern skies start to light up as the eyes adjust.

My original shots of Orion were 1.6 seconds where I only had about 60 of which 30ish were stacked in DSS.

With the wide angle lens I upped it to 2 second exposures, moved the ISO from 400 to 800 and was also shooting at F3.5 rather than 5.6 so more light should be getting through. Unfortunately with the speed of the CF card in my camera (just ordered a much faster one) I can continuously shoot at around every 12 seconds. The clouds were about last night but regularly cleared to get quite a few images. In all I managed to capture around 180 images and was hoping that DSS would work well.

I've attached several versions of the process all now saved as jpg for ease in here.

CRW_3829-Original.jpg - The original shot as captured on the camera.

CRW_3829-Adjusted.jpg - How I can change the levels in Photoshop to show the hidden content including hot pixels

DSS-First-2.jpg - Less than 30 of the 180 images stacked and adjusted to show the hidden content

DSS-Latest.jpg - When I went through the stacking process again but for some reason on one image stacked

So my first question is that it doesn't matter what I do in DSS when I try and process the original images again is that it only ever ends up advising that only one image will be stacked. Now I'm guessing is that when I first select the light images there is a tick box to have them read only. So I expect that DSS is modifying the RAW images as it processes them and then sees them as all the same. For example when you open a RAW image in Photoshop you get the RAW utility open where you can then tweak the image. If you open the image again later on the RAW image has been left how you last adjusted it, even though you don't save it.

Any thoughts on why DSS only will use 1 image now?

My second question which I think I can answer myself is how to get more content? I guess that it is a simple case of using longer exposures. I'm not using any tracking so need to make sure I don't get trailing stars. Now using the 600 rule 600/(18*1.6) gives me 20.83 seconds and even if you go as low as the odd person does and use a 400 rule then 400/(18*1.6) gives me 13.88 seconds. So perhaps next time we get some clear skies I will try 8 or 10 seconds exposure.

So is the above the right answer for more content?

Oh and for anyone who is after a nice easy way to take lots of continuous images with their DSLR I purchased one of these a while ago for only around £15 off eBay. You can set how often you want the image taken, how log an exposure and even set the quantity of images to take. So for lots of stacking images or some nice time lapse photography they are well worth the money.

[badgerchap]

DSS may be set up so that you've only got one image that it considers acceptable, as per the settings. Make sure you have 'check all'ed then press 'register checked pictures'. In one of the settings, can't remember which, there is an option to change the threshold of star detection. Have a mess around with that and see if it helps. 

[davefrance]

As a general rule I start with 10 secs @ F5.6 on my 18-55 standard Nikon Kit Lens set at 18mm. 20 lights and 20 darks sufficient to get decent image. You may need to increase sensitivity in DSS to get it to stack more than one frame. Depends on how many stars and how bright in image.

[Langy]

I've tried messaging around with various settings in DSS I've reduced the Star Detection to 2% where it initially comes up with 5 stars, so I switch off the Median Filter and get 63 stars.

I also tried changing the stacking parameters for Light, Dark and Bias and all do the same.

[davefrance]

I think increasing your exposure length will do the trick

[Langy]

Yes Dave, I think I will get more content that way.

I'm just miffed as to why when I run the DSS again it only stacks one image, now testing again.

[davefrance]

Increasing the exposure will give you more stars that DSS can register with. I don't think it can find enough bright stars in your frames. I have had that problem with frames that have few bright stars.

[Langy]

It's just strange though that the first time I ran through the process it stacked about 20ish images out of 223 (yes just checked and it is 223 lights) but now it only ever does one. So I suspect DSS has written something back to the RAW files.

[davefrance]

Just a thought and you may not think it worthwhile, how about taking 20 lights and increasing brightness/contrast or stretching histogram and reprocessing see if it will then stack them.

[Langy]

Just been out again tonight in the brief clear skies out there. 10 Seconds F3.5 got about 20 stacked in this image.

This time I've set RO to all the files to see if it works better.

[davefrance]

Just been out again tonight in the brief clear skies out there. 10 Seconds F3.5 got about 20 stacked in this image.

DSS-01-PS.jpg

This time I've set RO to all the files to see if it works better.

Well done.

[Langy]

Final revision, I suspect the brighter noise around Jupiter is due to the brightness of it.

If I take it back then I start to lose the fainter stars in the background.

Should this be a final presentation image then I would mask the remainder out in PS and bring down the levels around Jupiter.

All this a good example of AP in a built up area plagued with the wonders of the orange street lights.

Looking forward to my Barlows and T Mount being delivered this week and some clear skies. I'm sure I will soon be ordering the RA motor for my mount.

[davefrance]

I'd be proud of that.

May all your Barlows be little one's.