Mark Bednarczyk wrote:

I would like to use GIMP to tweak astrophotography images. These are usually faint images of DSO (Deep Space Objects). Anyone have links to a tutorial or hints. I'm sure someone has done something with GIMP and astrophotography.

Thanks,
mark...

Look for any post processing tips. Most can be done in GIMP. I will say it will be nicer when GIMP supports deeper color depths.

One thing that I have read is making multiple exposures with digital cameras and then adding the photos together.

I am just about to get into astro photography as well.

Robin Laing writes:

One thing that I have read is making multiple exposures with digital cameras and then adding the photos together.

One common operation is "stacking": as you add layer N to the image, make the layer mask's transparency be 1/N. So the first layer is the background at 100%, the next layer goes in at 50%, the next at 33%, etc. This enhances the contrast of a bunch of short exposures without enhancing the noise much; it apparently also sharpens lunar/planetary images, by reducing the effect of temporary bad seeing in one part of the image.

I don't know of a gimp plugin to do stacking, but it would be fairly trivial to write. (I'm not really an astrophotographer myself and have never stacked more than four images, so I didn't look very hard for a plugin, nor bothered to write one.)

Of course, you have to make sure all the images are accurately aligned (easy if you have pinpoint stars, not so easy if you're shooting something with soft edges like Jupiter). 2.2's transform tool previews should make this important part a LOT easier.

It would be a bit easier still if there were a way to alternate between rotation (transform tool) and translation (the move tool) while previewing without having to actually do the rotation (there's presumably a quality loss every time you free-rotate an image) but the only way I've found is to remember the rotation amount in the transform tool, cancel, select the move tool, move the layer, then transform again and type in the rotation where you left off. That comes up a lot with panoramas, too. Anyone know a better way to combine rotation and translation?

Though with a real astrophotography CCD and a rock solid mount you may not need any rotation/translation.

...Akkana

On Fri, Dec 03, 2004 at 07:08:15PM -0800, Akkana Peck wrote:

Robin Laing writes:

One thing that I have read is making multiple exposures with digital cameras and then adding the photos together.

I don't know of a gimp plugin to do stacking, but it would be fairly trivial to write. (I'm not really an astrophotographer myself and have never stacked more than four images, so I didn't look very hard for a plugin, nor bothered to write one.)

if you have images that are named sequentially (like img_0001.jpg img_0002.jpg), gap will make them into one single image, with each image being a different layer.

you could use gap to make the changes to each image, like changing the transparency before making them into one layer (for the viewing).

carol

On Sat, Dec 04, 2004 at 06:57:33AM -0500, Mark Bednarczyk wrote:

I'm fairely novice at this and this is interesting. Is this right "GAP = Gimp Animation Package".

close, GIMP Animation Plug-in.

Also could briefly describe how to import multiple images into gimp with the _00X.jpg sequential filenames?

i have this problem right now. to the best of my knowledge, at this point there is no way to rename an existing image set like that. however, this is the way that images come off from my camera.

Lastly how would you apply gap to change a property for all the layers, 1 expample is probably enough to get me started.

i wrote a tutorial for this. gap gui is a little different, yet so is the fact that it works on a bunch of images.

http://carol.gimp.org/gimp/2.1/gap/layers/

carol

On Sat, 4 Dec 2004, Carol Spears wrote:

Also could briefly describe how to import multiple images into gimp with the _00X.jpg sequential filenames?

i have this problem right now. to the best of my knowledge, at this point there is no way to rename an existing image set like that. however, this is the way that images come off from my camera.

A simple script to do that, provided you have a file containing the name of the files in the order you want them, is this:

#!/bin/sh # Usage: ./script

for i in $(seq -w 1 $(sed -e '/^$/d' $1 |wc -l | sed -e 's/ *\([^ ][^ ]*\) .*/\1/')); do mv `head -$i $1 | tail -1` $2_$i.jpg done

The index file should have one filename per line.

This script was created in 1-2 minutes, with minimal testing. Use with care.