Rotational image alignment

[redstamp]

I have been trying to capture 'whole sky' images with my Nikon D7000 and using my 18-200mm VR lens opened up to 18mm to get the widest angle.  Setting the lens to the fastest aperture, I still need to take quite a few images of 10-20s and try to stack them to get a decent image.

As my garden is surrounded by hedges and trees, I have to direct the camera almost straight up.  I then export my RAW images to my PC and have tried both Astrostakkert and Registax to stack the images, but I am still left with what looks like a rotation problem, as one part of the final image will be aligned, but rest of the image has star trails.

I can only assume these programs seem to align multiple images well if the movement in the images is in one direction, but they don't seem to cope well with images that have both translational and rotational movement.  Is this a known issue or am I just missing a setting or method of using the image stacking software?

Any clues on how to solve, or am I just trying something that isn't possible....?

[wxsatuser]

You really want something like Deep Sky Stacker.

[Knight of Clear Skies]

As wxsatuser says, Deep Sky Stacker should sort this out for you. I've used it to stack several minutes worth of data taken from a fixed tripod before.

When you say 'whole sky images' are you pointing the camera in different directions to make a mosaic? If so, you'll need to stack each section separately, then stitch the panels together in software. Microsoft ICE is free and usually works well.

[dph1nm]

Hmm - if you have too much rotation I think lens distortion at 18mm might make stacking pretty difficult. I don't think DSS can correct for that, although there may be software out there that can.

NigelM

[redstamp]

Just taking a single shot and not mosaic, so should be OK - will give DSS a go - looks much more suited to my needs and far simpler!

Thanks for the advice chaps.