HDR with image sets of multiple exposure times

[markcasazza]

I am currently evaluating StarTools. I have images of NGC6992 with exposures at 6, 3, 1.5, and .75 minutes. It took exposures as short as 45 seconds to avoid burning out the core. Is there a way to combine these after each group is stacked with StarTools in a HDR manner to replace the burnt out regions with the same area from an image with a shorter exposure?

Thanks,

Mark

[admin]

Hi Mark,

Have a look at this YouTube video to see how to quickly and painlessly create HDR composites (in particular towards the end around 8:11).
http://www.youtube.com/watch?v=WqYim2phWLo

I'm not familiar with any areas that require more than two different exposure times to capture their full dynamic range though.

Happy holidays & clear skies!

[markcasazza]

Thank you. I did not get to that video yet, but I will watch it these next few evenings. I quoted the wrong object in my question. The object is NGC7023. It has a huge dynamic range from the center of the nebula to the dark nebula surrounding it. I think I can compose a good picture with the 6 minute exposures and either the 1.5 minute or 45 second exposures. I am currently stacking each set and I will decide what to use when the time comes. I took as many as I did at the time because my plans were to stack and pre-process then all the same way, then use Photoshop to HRD merge them. I did not know your tools existed at the time.

So far with just a few hours working with the demo I am impressed. I only wish I could save a 16-bit file with a HUGE "Demo" watermark all over it. That would let me experiment with the output in Photoshop and still ensure the end result was unusable.

Regards,

Mark

[Starry Eyes]

Looks good

? Does the HDR Composite function do any aligning internally between the two files? If I'm using DSS to create different stacks they will differ slightly. Even with the same equipment they may be different pixel count, dithered, slight rotation, or shifted in x,y. Same pixel scale. If not, how do I deal with it? I use BYEOS, DSS, & StarTools .

[admin]

Looks good

? Does the HDR Composite function do any aligning internally between the two files? If I'm using DSS to create different stacks they will differ slightly. Even with the same equipment they may be different pixel count, dithered, slight rotation, or shifted in x,y. Same pixel scale. If not, how do I deal with it? I use BYEOS, DSS, & StarTools .

StarTools doesn't do any preprocessing like that (yet), so you'd have to do that in DSS. I think alignment is possible by using the shorter exposure as a reference frame. Might want to ask around on the DSS Yahoo forums though... Simple X, Y alignment in StarTools is possible in the Layer module though.

[Jeff2011]

If I'm using DSS to create different stacks they will differ slightly

Pick a frame from one of your stacks as a referenced frame. I usually move this frame to a higher level directory to differentiate it from the others. Then in each stack include this frame, but leave it uncheck for the stacks that it does not belong in. One caveat is that this frame must be registered first, so I process that the stack that is belongs to first. If this does not work, try putting the reference frame by itself in the main group and put the stack frames with darks flats, etc in the second group tab. I used this technique once to align LRGB stacks taken with my QHY5L-II mono and all of the frames were aligned and sized to the reference frame and they all loaded correctly into StarTools using the LRGB load without me having to align them manually.