How to rotate darks?

[Nigan]

Hello everyone,,,
This may be a pretty dumb question – but here goes anyway.
When using Dawn I want to use darks that have been rotated by 180 degrees so that their orientation will correspond with the lights being used. So far as I understand it Dawn only accepts fits files so the rotated darks will need to be in fits format. I can't use Fits Liberator to convert the revs check darks for two reasons (1) it only allows for “flipping” not rotating and (2) it only seems to save tiff files. I've tried using Photoshop but although I can rotate each dark and save the result as a fits file Dawn objects when I try to load the rotated files with the message “Error loading FITS file – Image not recognised as an Atik image”.

So how do I do it? Any help will be appreciated.

[LaLucina]

Why do you need to rotate Darks? By definition they are to reduce long exposure noise and hot pixel reduction, and as such should not allow any light through to the sensor by having the lens cap on. You can build a library of calibrated darks that can be used with any light frames. In practice only Flat frames require correct orientation with lights.

Edit. I get what you’re trying to do now. Surely any Darks you have taken will be in natural sensor orientation with the Lights, unless you have flipped the Lights by 180 yourself in an editing program or the capture program for Dawn itself. If that’s the case you’ll need an editing program that deals with fits such as Nebulosity, PixInsight etc. There are a few Fits file viewers out there that can also rotate images, I think NASA has one that you can download, or there are a few others I’ve seen.