AstroPlan

Based on James Lamb's Astroplan software detailed on his YouTube channel: https://www.youtube.com/@Aero19612.

Assumptions

• Earth is a sphere
• Earth's orbit is circular
• Earth spins but does not precess
• Sun is fixed in space
• "Darkness" is when Sun's altitude at Lat, Lon < -12 deg
• All distances are small compared with distance to a DSO

Where to get the latest Stellarium DSO Catalog

It is available in text format in their GitHub repo.

Specifically the file is here.

Run Configurations

Run configurations (such as observer's latitude, etc) are configured using an .ini file.

By default, the system will look for astroplan.ini in your app's directory, but you can override this when starting the app to use any other .ini file - this allows you to keep multiple configuration profiles and run AstroPlan based on whatever config you want. For example you could use this to store configurations for different observation locations, object sizes, catalog subsets, etc.

To do so, use the command line switch -i or --ini, for example:

python astroplan.py --ini astroplan_full.ini

These .ini files look like this:

[Observer]
Latitude = 33.0
Longitude = -95.0
HorizonFile = ./horizon.txt

[Filters]
MinObservationHours = 4.0
MinObservationPeakAltitude = 30.0
MinObservationAltitude = 15.0
MinDSOSize = 10.0

[Catalog]
# Set MinCatalogIndex to 1, and MaxCatalogIndex to blank to process all entries
CatalogFile = ./stellarium_catalog.txt
MinCatalogIndex = 1
MaxCatalogIndex = 

[Parallelism]
MaxParallelJobs = 6

[Output]
# Specifies an output folder where all data files are written
#   Path can be relative to where the app is running, or an absolute path
#   For a relative path, use ./ (on *nix, .\ on Windows)
# Set ClearResultsBeforeRunning to `true` to delete any pre-existing results folder
Results = ./results2
ClearResultsBeforeRunning = yes

Parallelism

AstroPlan uses Python's multiprocessing facilities to process simulations and chart generation in parallel. How many jobs are run concurrently is determined by the MaxParallelJobs settings.

So, question is : how should you set that value for your system?

Best is to try it out with various values, usually ranging from half to just less than the number of cores on your computer.

For example, on a Mac M1 Max, a pure linearized strategy takes about 172s to run the full catalog.

With the same settings, only changing the value for MaxParallelJobs we see the following:

MaxParallelJobs	Total Runtime
2	90s
4	48s
5	39s
8	28s
9	25s
10	26s
12	28s

As you can see, the sweet spot for that system appears to be 9 parallel workers.

Sample Run Console Output

When AstroPlan runs, you will see console output letting you know what stage the app is at, and the time taken by various processes.

Starting...
	Load horizon data: 0.00 s
	Running simulations:
		- (2) M_45
		- (3) M_8
		- (4) SH2_155
		- (182) NGC_147
		- (216) NGC_185
		- (236) M_110
		- (254) M_31
		 ...
	Simulations completed: 143.41 s
	Identified:
		- Galaxies: 29
		- Nebulas: 177
	Generating outputs:
		- Data files: 0.00 s
		- DSO plots: 31.55 s
		- Horizon plot: 0.09 s
		- Global plots: 0.36 s
Completed: 175.41 s

Development

Python black and isort are configured for this project.

These tools simply reformat Python code uniformly (following PEP8 standards).

The isort tool organizes and sorts the import statements in modules, while the black tool reformats a variety of things like indentations, quotes, etc.

If you are on a *nix machine, simply use the Make command:

make lint-fix

On Windows, you can instead run this from a prompt:

 isort .

followed by

black .