How to access the Astrometry star catalogue's star id and magnitude of the result?

[Andreas Hornig]

Hi,

I need the magnitude of stars to compare them with the brightness of satellites in the same image[0,2].

How could I do that with Astrometry directly?

I currently obtain the magnitude by using the results of the Astrometry.net .corr file and use their ra/dec values with the Simbad API (cds University of Strasbourg) to query for the closest star to that position. With that result I have the magnitude.

So, with that I have to be careful to not run into the api limit. And It also takes a bit of time.

My hope is now, that there is a way to directly either get the magnitude, or at least get an ID/Name/else unique identifier that I can use to directly query the CDS database.

The main goal is to see how the SpaceX Starlink satellites are blinding /interfering with astronomy and how SpaceX managed to dim them down with their "visors" during the different hardware versions[1].

[0] https://photos.app.goo.gl/uc544z63ZpWGsMtj7
[1] https://arxiv.org/ftp/arxiv/papers/2210/2210.17268.pdf
[2] https://twitter.com/andreashornig/status/1599648693476823040 (alternative for [0] for those who do not use google photos)

Best regards, Andreas

[Dustin Lang]

Hi,

If you're using the solve-field command-line program, you can add the "--tag-all" argument to copy extra data from the index files into the RDLS files.  The 4100-series index files include magnitudes from Tycho-2.  The 5200-series "Heavy" version includes data from Gaia-DR2 (magnitudes, proper motions, etc).

On the nova.astrometry.net site, that information isn't available (yet).

cheers,

-dustin

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[Andreas Hornig]

Hi Dustin,

thank you a lot for this hint.

I am using the solve-field on a raspberry pi and I already tried it. It is working and I get the magnitudes now. thank you :)

I still have a fre questions:

On Tue, Dec 6, 2022 at 4:49 PM Dustin Lang <dstn...@gmail.com> wrote:

Hi,

If you're using the solve-field command-line program, you can add the "--tag-all" argument to copy extra data from the index files into the RDLS files. 

I tried two ways and I got different results.

Firstly I added --tag-all and --overwrite to my normal task. Then I received the magnitudes in .corr. That is great. I did not find anywhere an ID or the name of the stars.

Then I solved the photo without these arguments as before. When the different files were stored, I just used "solve-field --tag-all --overwrite SAMEPHOTO" Then Also thre PNGs were also created with markers for the stars, the hashgraph, and one with the star names and constellations. That is cool.

But these PNGs I did not get with the first described way. And I now saw that somewhere needed to be the starnames, because they were printed into the PNGs. But I did not find them in the different files.

I would like to avoid this extra step anyways to save some computation time.

So maybe I did not fully understand how to apply it and/or where to find the star IDs or names.

 

The 4100-series index files include magnitudes from Tycho-2.  The 5200-series "Heavy" version includes data from Gaia-DR2 (magnitudes, proper motions, etc).

Ah, great. I use the 4100 because of my FOV=45° Sony Alpha7s videos.

 

On the nova.astrometry.net site, that information isn't available (yet).

:), I will be happy when I can make my raspi do this already. BUT I can just repeat that I like nova api. This is how I started here and how you caught me.

In related news:
I now added a log curve fitting to determine the satellite brightness. I updated the google photos album already. There you also see that the star names are missing, because I did not search via CDS for them. I just used the astrometry.net magnitudes.

 

Best regards,

Andreas

[Dustin Lang]

Hi,

The "--tag-all" option is supposed to be totally independent of whether the plots and made, and what goes on the plots.  If you add "-v" to your solve-field command, you may get more details about why a plot was or wasn't created.

I usually use the "--continue" option (rather than "--overwrite") if I'm re-running.

You're right that the 4100-series index files do not contain any IDs, they just contain Tycho-2 magnitudes.  The Tycho-2 star identifiers are just like "Tycho2 3028-814-1"... if you want names for the very brightest stars, you can look in the bright-star table, https://github.com/dstndstn/astrometry.net/blob/main/catalogs/brightstars.fits  .  Only about 500 stars have real names.

cheers,

dustin

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