The image solver script allows you to plate solve an image, meaning it will identify the images coordinates, rotation, resolution, pixel size and more. The image solve script is a great option for combining images together to create a mosaic. This approach simply uses image solver to help find the center of a mosaic image.
PixInsight Image Solver is a script, located at Script – Image Analysis – Image Solver. Once loaded, the image parameters must be supplied.
Although you can use the search button within Image Solver to identify the right ascension and declination coordinates, this might fail for larger mosaics. Depending on what tool you use to manage your imaging runs, you can probably get these coordinates from the sequence.
For example, in Sequence Generator Pro, I can select each frame of the mosaic to get the RA/Dec values and enter these into PixInsight Image Solver
The easiest way to gather these system parameters is to simply upload one of the frames to Astrometry.net. Once processed and solved, Astrometry.net will provide the subframe scale in arcseconds/pixel.
An alternative method is to use the formula
Arcseconds/Pixel = 206.2648 * ((Camera_Pixel_Size_in_μm) / (Telescope_Focal_Length_in_mm))
My calculations are:
- Telescope Aperture: 304.8mm (12 inches)
- Telescope Focal Ratio: 6.3
- Telescope Focal Length: 1920.24mm (Aperture * Focal Ratio)
- Camera Pixel Size: 3.8
- Camera Pixel Size (Drizzle 2x): 1.9
This yields the following values
- No Drizzle: 40.8
- With Drizzle (2x): 20.4
Once the parameters are set, running PixInsight Image Solver should come up with a solution for the image.
This information is now stored within the FITS header for the image. Remember to save the image and take a screen shot of the data within the process console as we will use these later.
With the image solver script complete, the next step in the mosaic workflow is to Annotate the image to help visualize the center and overall dimensions.