PhoSim Tutorial 4: How to Generate a Field of Stars and Galaxies

To simulate a field of astronomical objects you can do the following command:

phosim examples/small_catalog -c examples/nobackground

It should look like this (log scale and zoomed in):

The small catalog file has the following commands:

rightascension 0

declination 0

moonalt -90.0

stars 18.0 30.0 0.1

galaxies 18.0 30.0 0.1

This specifies a set of stars and galaxies in the 18th through 30th magnitude range covering a circle with diameter of 0.1 degrees. The stars and galaxies have a range of realistic spectral energy distribution and sky densities. The galaxies have a detailed set of morphologies.

If you increase the exposure time in the small_catalog to obtain a much deeper image as:

vistime 150000.0

Then the following image will be obtained:

The angular size of the image can be chosen to be larger than the focal plane and PhoSim will correctly trim away objects that do not contribute photons.