The NOMAD catalog for Cartes du Ciel

[oleg_astro]

The NOMAD catalog

The Naval Observatory Merged Astrometric Dataset (NOMAD) contains astrometric and photometric data for over 1 billion stars derived from the Hipparcos , Tycho-2 , UCAC2 , and USNO-B1.0 catalogs for astrometry and optical photometry, supplemented by 2MASS near-infrared photometry.
http://www.ap-i.net/skychart/_media/...omad.png?w=400
Thank to the effort of Oleg Maliy we can now use this catalog with Cartes du Ciel!
The catalog is available to download by Bittorrent. It is presented in the form of text file for each zone area (South Polar Distance).
You need to run Catgen to use this data with Skychart but this as the advantage to let you select the data you need for the catalog size you want.
This also make it easy to use this data outside of Skychart.
For each star the files contain:

• NOMAD identifiers.
• A flag for each source catalog.
• Coordinates ICRS, with mean error and source flag.
• Mean epoch of the position.
• Proper motion, with mean error.
• Magnitude B, V, R with indication of origin.
• Magnitude J, H, K from 2MASS
• A flag if the star is a recommended astrometric standard.

Source: http://www.ap-i.net/skychart/en/news/nomad

[2stroke (Jay)]

Wow 48gb in size lmfao, now thats a catalog

Think ill pass on this one

[oleg_astro]

Yes, it's my biggest catalog for Cartes du Ciel

[mithrandir (Andrew)]

Jay, 48GB is the final size. The compressed raw data files are around 30GB. You have to unpack the raw data to do the conversion and that needs around 160GB, and then several CPU hours to create the files CdC will use. If you only want some of the sky - eg I have no real use for beyond 56N - you don't need all the raw data files.

[bojan]

Something is wrong with some of the torrents..
I downloaded 1/3 of files, but for the rest of them there is an error (invalid URL).
Still keep trying..

[2stroke (Jay)]

Just the trackers? don't worry about it

[oleg_astro]

Originally Posted by bojan

Something is wrong with some of the torrents..
I downloaded 1/3 of files, but for the rest of them there is an error (invalid URL).
Still keep trying..

Solution from Patrick [skychart-discussion] Nomad torrent download halt after 24 GB


Hi,

I remark the only tracker present in the torrent files is down, so it rely only in DHT to find peers and this may take time.

So I update the torrents to add more tracker including one on my own server.
If you are currently downloading the files do the following.

- from your BT client stop all the nomad torrent and remove them (not the data files!)
- download http://www.ap-i.net/pub/skychart/nom...ad_torrent.zip
- extract the zip to replace the torrent files.
- add the torrent to your BT client again.

This not affect any parts you already download as the hash the same. It will just check the files again on startup.

It is good if any people who is seeding the files can update the torrent to connect to the new tracker too.

Patrick

[mithrandir (Andrew)]

Originally Posted by 2stroke

Just the trackers? don't worry about it

It improved after Patrick provided the new torrent files. 090-099 and 100-109 only took a few hours to download.

[bojan]

Working now.

[oleg_astro]

I think about editing the NOMAD txt-files for deleting many unreal stars

http://www.astroclub.kiev.ua/forum/i...ch=22573;image