best_observation_date

[pclp007]

Hi,

I've recently come across skycalc_ipy and would like to use it to determine what the best observation date for a target would be at the VLTI. Is this possible?

I'd also like to make altitude and airmass plots for a target and the moon. Is there a way I can do this with skycalc_ipy?

[gotten]

In what respect are you interested in the best observation date for VLTI ?

To properly take into account the visibility of the targets as seen from all the VLTI UT and AT telescopes (both due to obstructions caused by other telescopes and the limits on the delay lines) I recommend using aspro2 (https://jmmc.osug.fr/english/tools/proposal-preparation/aspro/) for this.

I think that for all current VLTI instruments that operate in NIR/MIR the moon will not be a constraint in terms of in brightness, in fact VLTI-UT is only scheduled during bright time.

You can easily make a star altitude plot in astropy with various targets and the moon, example notebook: https://docs.astropy.org/en/stable/generated/examples/coordinates/plot_obs-planning.html

[pclp007]

Hi,

Thank you for your response. For any target, I'm interested in knowing when it is best observable at the VLTI, i.e., longest observability (assuming I have no idea about a particular date). Apart from ASPRO2, is there a solution implemented in Python that can take into account delay line constraints and shadowing from the UT's?

[gotten]

I don't know of any python implementation. I have asked around. With any luck there will be a reply.

The shadowing by other telescopes can be implemented in python by comparing the Azimuth and Elevation or declination and hour angle against masks for each of the UT and AT configurations. The sky shadowing maps can be found as images on the ESO website.

The delay line implementation of aspro2 is here: https://github.com/JMMC-OpenDev/aspro/blob/master/src%2Fmain%2Fjava%2Ffr%2Fjmmc%2Faspro%2Fservice%2FDelayLineService.java

It does not look like an easy task to convert to or wrap in python (also you would have to check the software license to see if this is allowed).

Maybe it is easiest to use aspro2 to extract delay line limits expressed in hourangles versus declination of the target in steps of several degrees and then interpolate this lookup table in python.

[pclp007]

This is very helpful, thank you very much. Yes, please let me know if you receive any response as I'd very much like to figure out the optimal date in the year for an arbitrary target.