2/14/2023 0 Comments Diffraction limit calculatorRight: result of processing middle frames in RegiStax. Middle: individual atmospherically perturbed frames. 0 degrees is a target at zenith, 90 degrees a target at the horizon. The variable zenith_angle_deg allows you to simulate how seeing degrades due to observing targets nearer the horizon (hence with an greater airmass). 2 arcseconds is considered moderately good for an amateur site, 0.7 arcseconds is considered excellent for a professional observatory. Right: Jupiter observed 10 degrees above the horizon.īy setting the variable seeing_arcsec_500nm you can vary how "good" the seeing is. Simulate varying levels of atmospheric seeing: Right: Diffraction limited image for an 8" telescope.īy setting atmosphere = False the image is rescaled as described above and processed to produce a diffraction limited image 3. Produce diffraction limited images for a given telescope: The input image is rescaled as if it were sampled by the above described detector attached to the above described telescope. angular_pixel_size_input_image = the angular width of each pixel (for example if Jupiter is taken to be 50" in diameter on sky, divide this by the number of pixels across it is in the input image).telescope_focal_length_m = the effective focal length of the simulated telescope.If you are interested in diving into the physics behind this simulation here is a talk aimed at the level of the interested amateur: pixels_per_ro: leave at 30 by default but always keep above 7 to ensure accuracy in simulating atmospheric perturbations.CCD_pixel_size: a few to a few tens of microns (1e-6 to 20e-6 meters).wavelength: typically the visible wavelength range, 380-740 nanometers (380e-9 to 740e-9 meters).zenith_angle_deg: between 0 (at the zenith) and 70 (close to the horizon) degrees.seeing_arcsec_500nm: between 0.7 and 2 arcseconds is a typical range from excellent to moderately poor seeing.telescope_focal_length_m: of order a few hundreds of mm to a few meters (300e-3 to 5 meters).Due to the nature of how the atmospheric perturbations are simulated the upper limit on the diameter will depend on the level of seeing, with worse seeing reducing the maximum telescope diameter that can be simulated telescope_diameter_m: of order a few hundreds of mm upwards (100e-3 upwards).There are descriptive comments alongside each parameter which are not repeated here however below is a suggested range for each parameter: The parameters which can be reconfigured are under the comments #physical parameters (line 90) and #simulation parameters (line 102) in the main file, Telescope_simulator.py. Once the installation described above is complete Telescope_simulator.py can be run as is and will by default produce 10 images of Jupiter as seen by an 8 inch telescope with an effective 3.6-meter focal length under average seeing conditions. This script is designed to be as simple as possible to get started with. This script has the following dependenciesĪll of which can be installed by the command pip install "module name". There are likely more efficient ways of writing this code but for the sake of clarity they have not been used. The script is written to be easy to read as it is in part used as a teaching tool. Not only does this script resample the image, it also simulates the effects of diffraction limited resolution and perturbations due to atmospheric seeing. Right: is the output of the simulation, the image of Jupiter as would be seen by an 8" telescope with a focal length of 1.2 meters, using a 3x Barlow lens and a CCD with 2-micron sized pixels.Ībove is an example of the simulation in action. Left: is the input, an image of Jupiter taken by the Hubble space telescope. A python script for not just simulating the field of view but also atmospheric seeing and diffraction effects of a telescope.
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