Which catalogue do I need?

arcsec needs a star catalogue that suits the size of your field. Enter your telescope and camera below to find which one, or enter the field of view directly if you know it.

Start from

Telescope and camera Field of view

Focal lengthmmInclude any reducer or barlow.Pixel sizeµmUnbinned, from the camera's data sheet.Sensor widthpxSensor heightpx

I also want a photometric catalogue, for colour calibration

How it chooses

This is the same rule arcsec catalog recommend uses, so the two always agree:

• The pixel scale is 206.265 × pixel size (µm) × binning ÷ focal length (mm) arcseconds per pixel, which is how arcsec reads XPIXSZ, XBINNING and FOCALLEN from an image header.
• The field of view is the pixel scale times the sensor size, on each side. Binning does not change it.
• The catalogue is chosen for the longer side of the field, as arcsec catalog recommend --like image.fits does when it reads your image.
• Of the catalogues whose published field range includes that size, it suggests the smallest download. A denser catalogue also works, and can help on crowded or faint fields, but there is no need to download 1.2 GB when 102 MB will do.

The photometric catalogues (the V-series) add Johnson-V magnitudes and colour, for photometry and colour calibration in software that reads ASTAP’s databases. arcsec can solve with them too, but the picker recommends a solving catalogue for that. The blind index set is only needed to solve with no position hint, and even then arcsec finishes the solve against a solving catalogue, so you need one of those as well.

The catalogue guide lists every catalogue, where they are installed and how to share them with ASTAP.