Quote:
Originally Posted by Octane
You needn't find the angle of rotation by trial and error.
Use the ruler tool (I) and draw a line, left to right on something that should be level.
Go to Image -> Rotate -> Arbitrary, and it'll have the required angle of adjustment already pre-filled for you. Click OK, and you're done.
H
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Thats what I mean by "trial and error" The problem is just working out what is the actual true base line you wish to work to.
When I prepare a texture to insert into Stellarium it likes to be "up" = North. and its size 256 x256, 512 x 512 or 1024 x1024 pixels. The first thing I do is locate a known star at what I can use as the centre and use its J2000 coords. I place the picture into TheGimp and locate the pixel coords of its centre I can then crop the picture in Photoshop to give me the required size.
Next I put the picture back into TheGimp and get the pixel coords of some other known stars near the edges of the picture.
I then use a program I wrote in QBasic that takes all this information and calculates the coords of the corners of the picture on a spherical surface and writes an insert to place in the textures.json file that will display the picture as an overlay in stellarium.
The program uses a lot of maths to calculate the corner coords to 4 decimal places and saves me quite some time in getting the picture to actually overlay the stars.
We can display pictures from the DSS in stellarium but the feature is not activated at the moment. The DSS textures have the coords of the corners in the header so there is no problem displaying them. That is why we use the "json" system.
Barry