Target Visibility by Month

Overview. For a given target and observing site, this tool estimates how much time the target is above a minimum altitude during astronomical darkness for each month.

1. Resolve target → coordinates. It searches a relatively small local catalog (due to resource limitations), then Astropy’s name resolver, then parses RA/Dec strings.
2. Observer & site. The site’s latitude/longitude/timezone define an astroplan.Observer.
3. Altitude window. Using the site latitude φ, target declination δ, and minimum altitude h₀, the tool computes the hour-angle limit H₀ where altitude ≥ h₀.
4. Night window. For sample nights (days 1, 10, 20) each month, the tool computes astronomical dusk/dawn and convert them to local sidereal time (LST).
5. Overlap. The tool computes overlap the target’s LST visibility interval with the night’s LST interval to get usable minutes for that sample night.
6. Monthly value. The tool takes the median across sampled nights to get each month’s usable nightly time (minutes → hours for the chart/table).

API. The chart calls a small JSON endpoint:

GET /api/visibility/<target>?location=<name>&year=<YYYY>&min_alt=<deg>

Script Libraries. Flask · Astropy/astroplan · astroquery/SIMBAD · Chart.js

Notes: The uses a few sample nights per month to maximize application speed and preserve resources; exact results will vary slightly night-to-night and with different min-alt settings.