Completely confused

[CThody]

Hi. I am baffled by Deep Sky Stacker. When I take images on the DSLR I can review the image on the screen and all looks well... When downloaded into lghtroom the data is there and I can see the nebula (in the latest example I was imaging Bodes) but when I then put the files into DSS and stack etc (with darks and flats) all goes dark and the nebulosity disappears (along with any colour saturation).

I can't work out what I'm doing wrong - so any advice very much apreciated.

Latest image taken at ISO 1000, 110 second exposures through a Celestron C8. All I have to show is black with a few stars in DSS...

Very frustrating!

[Demonperformer]

Have you tried adjusting the RGB and Luminence settings on the final image?

[Zakalwe]

OK, when you initially load the lights, click on one of them and wait a moment or two. You can then adjust the gamma setting in the top right hand corner (there's a slider there). This won't affect the image, it just allows you to see what's there so you candrag a Region of Interest box around.

I use this tutorial, once it has stacked. It seems' to work well for me.

[CThody]

Have you tried adjusting the RGB and Luminence settings on the final image?

Hi. Yep, tried that in many different ways, and it's making it worse for some reason...

[CThody]

OK, when you initially load the lights, click on one of them and wait a moment or two. You can then adjust the gamma setting in the top right hand corner (there's a slider there). This won't affect the image, it just allows you to see what's there so you candrag a Region of Interest box around.

I use this tutorial, once it has stacked. It seems' to work well for me.

Thanks for this. That's a usefuil tool, I used it to reset the image but, when stacked, it wernt back to the dark result. Should I have saved somethng once I'd adjusted that slider?

[Zakalwe]

Thanks for this. That's a usefuil tool, I used it to reset the image but, when stacked, it wernt back to the dark result. Should I have saved somethng once I'd adjusted that slider?

From the DSS help file:

"To the top and the right a slider may be use to change the gamma of the previewed image which may be useful to view faint objects.

Of course no modification is made to the real image as it is only a previewing trick."

So, in answer to your question, the adjustment has no affect on the images...it is only there to help locate faint objects.

Once you stack it, then you can fiddle with the settings at the bottom of the preview screen. I normally select the midpoint of each RGB slider and use the arrow keys to align then. Then I go to Luminance, and use the bottom slider in the Mid-Tone to brighten or darken as required. I don't touch anything else, as it is very easy to clip the data. On nebulae, I will probably go to the Saturation tab and boost the saturation by about 10%. Again, overdoing this will result in a lot of noise.

Then I save the file as a 16bit TIFF, applying the changes. Then into PS, where I normally end up frustrated, in a bad mood and with a poor result!

[dph1nm]

The slider in to top right does not affect the stacked image at all. You need to use the RGB Luminance and Saturation sliders at the bottom, as per the tutorial mentioned by Zakalwe. I always use a saturation of 20%. Use the central triangle on the RGB sliders to align the three coloured histograms (if you have asked DSS to do RGB background calibration you should not have to move these very far). Be careful - they are very sensitive! BTW, you should have log sqrt showing down the left hand side of the sliders (the default I think). In the luminance section the lower of the two Midtone sliders is the important one. You need to move this to the left (clicking on apply each time), until the background in your image starts to show (usually when the solid S shaped curve passes through the RBG histograms about 1/3 of the way up. Again this is quite sensitive. A change of only a few tenths of a unit can make a big difference once you are close to the correct value). This should give you a sensible image. You can then experiment with the other luminosity sliders (the upper midtone increases the contrast when you decrease the amount - I usually do this).

NigelM

[MG1]

From the DSS help file:

"To the top and the right a slider may be use to change the gamma of the previewed image which may be useful to view faint objects.

Of course no modification is made to the real image as it is only a previewing trick."

So, in answer to your question, the adjustment has no affect on the images...it is only there to help locate faint objects.

Once you stack it, then you can fiddle with the settings at the bottom of the preview screen. I normally select the midpoint of each RGB slider and use the arrow keys to align then. Then I go to Luminance, and use the bottom slider in the Mid-Tone to brighten or darken as required. I don't touch anything else, as it is very easy to clip the data. On nebulae, I will probably go to the Saturation tab and boost the saturation by about 10%. Again, overdoing this will result in a lot of noise.

Then I save the file as a 16bit TIFF, applying the changes. Then into PS, where I normally end up frustrated, in a bad mood and with a poor result!

Have you tried the free NASA/ESA plugin for PS? FITS liberator..,.you can then import the fits files and stretch them at the same time....Each channel separately.

[CThody]

This sounds interesting, but as a complete novice I have no idea what a FITs file is. Any advice for a layman would be helpful...

[Demonperformer]

FITS is an image file format (like jpg, tif, raw, etc). Whether you can get them or not depends on your camera.

[MG1]

FITS is an image file format (like jpg, tif, raw, etc). Whether you can get them or not depends on your camera.

I believe some cCd cameras output fits, but I use them from DSS.

I'm shooting with a DSLR so DSs takes my raw cr2 files and creates a fits.