StarTools

When imaging some objects with my DSLR, it seems useful to take stacks with different exposure length and/or ISO, to better draw out the dynamic range of some targets. What I've been doing so far is:

1. Making a stacked image in DSS for each exposure/ISO combination separately, each time saving the file (there could be 2 to 10 different combinations here, it varies)

2. Reloading all stacked images I saved in step 1, and then aligning/compositing these in DSS using the dynamic image merging (i.e. entropy-weighted average, EWA) method, so as to create a final HDR image
(Based on the advice of Luc: https://groups.yahoo.com/neo/groups/Dee ... opics/1414)

3. Saving the HDR composite image and loading this into StarTools

This method seems to work reasonably well, BUT it doesn't give any real control over how to combine the stacks (EWA makes all the 'choices' based on its algorithm). So I wondered if there was a way to do this with more flexibility, using StarTools (and Layers?), whereby I use DSS to create each exposure/ISO stack and to align each against a reference frame, but then let StarTools take care of the actual final image compositing?

Kind of like this, but instead using the power of ST! http://www.astropix.com/HTML/J_DIGIT/LAYMASK.HTM

Hah, I (kind of) found what I was looking for, here: http://www.startools.org/forum/viewtopic.php?f=7&t=247

One thing though:

StarTools comes with a super easy way of compositing two (or more) exposure lengths

I'm not clear how to composite >2 images. Do it sequentially?

Amaranthus wrote:Hah, I (kind of) found what I was looking for, here: http://www.startools.org/forum/viewtopic.php?f=7&t=247

One thing though:

StarTools comes with a super easy way of compositing two (or more) exposure lengths

I'm not clear how to composite >2 images. Do it sequentially?

Yep, sequentially.

*However*, there are usually no good reasons to treat data this way, except perhaps for a handful of objects (for example M42) that have extremely bright cores. Even then, 2 exposure lengths should typically suffice.
For virtually all other objects, a single exposure length should be able to capture all detail, which can subsequently be brought out using other post-processing means.

Thanks Ivo -- fewer combinations certainly makes life at the telescope simpler! I've been reading "Imaging the Southern Sky" and they typically use one or two sets of exposure durations (and only once or twice, three).

I've been mucking about with various ISO/exposure combinations for my alt-az mount and Sony NEX-3 DSLR, whilst I wait for my new kit to arrive (the hold up is the delivery of the new AZ-EQ6 mount). Once I'm running with this (damn I can't wait to get stuck into mono CCD imaging!), I'll look forward to spending some time on fewer, longer and more targeted subs!

But until then, I'm having great fun mucking about with StarTools and my collections of sub-par, but useable, short stacks.