Calibration Server

The main address of the server at the moment is: http://gsaweb.ast.cam.ac.uk/followup

Authorization

• In order to access the server you need a so called "hashtag" which is an authorization key. In order to get one you need to ask Lukasz Wyrzykowski and give him also

the lon,lat of your observatory and list of filters you have.

• If you have the hashtag, you can use the login form of the server to authorize yourself. Or if you are doing some scripting, you will need to specify hashtag option in the GET, POST requests.

Preparing your data

In order to obtain the sextractor file with [Ra, Dec] coordinates required by the photometric server, the following steps have to be performed.

• Obtain the Equatorial coordinates for you photometry fits file by using Astrometry.net.
• Download the Astrometry.net output file (new-image.fits by default) from the site and use it as the sextractor input.
• Run sextractor:

sex new-image.fits -c /path_to/default.sex

• IMPORTANT! The following fields must be selected in sextractor default.param file: [MAG_AUTO, MAGERR_AUTO, ALPHA_J2000, DELTA_J2000]
• Upload the sextractor output catalogue (by default test.cat) to the Cambridge Photomretric Server.

Calibration of your photometric data

The main url for calibration of your sextractor catalogs is http://gsaweb.ast.cam.ac.uk/followup

You can also do that from the command line using HTTP POST protocol

curl -F matchDist=2 -F EventID='ivo://110610' -F sexCat="@path_to_your_sex_catalog;filename=test.cat" 
     -F "hashtag=XXXX" -F "MJD=2" -F expTime=1 -F noPlot=1
     -F forceFilter=no -F dryRun=1 -F outputFormat=json "http://gsaweb.ast.cam.ac.uk/followup/cgi/upload"

Parameters of the http://gsaweb.ast.cam.ac.uk/followup/cgi/upload

• matchDist -- matching radius in arcseconds
• hashtag -- your authorization key
• MJD -- mjd of the observations
• expTime -- exposure time
• comment -- comments
• EventID -- the ivorn of the alert
• dryRun -- the value of 1 allows you to check the results of the calibration without inserting anything into our DB
• forceFilter -- "no" means that the calibration will be fully automated. But You can also specify APASS/V if you want to calibrate using a particular survey/filter
• sexCat -- that's the Sextractor catalog you are trying to submit
• outputFormat -- at the moment the only allowed values are json and html

It is important that you can upload the data for the alerts which are in the database (e.g. which are listed here http://gsaweb.ast.cam.ac.uk/followup/list_of_alerts ). If the alert is not in our DB, you can insert it http://gsaweb.ast.cam.ac.uk/followup/newevent/

The allowed formats for the sextractor catalogs are plain ascii and FITS. Obviously those catalogs must contain RA, DEC and MAG columns.

Review of the data in the Database

You can view the list of followup_data which are in the DB http://gsaweb.ast.cam.ac.uk/followup/list_of_followups

You can view the list of alerts which are in the DB http://gsaweb.ast.cam.ac.uk/followup/list_of_alerts , and the subset of them which have followup data http://gsaweb.ast.cam.ac.uk/followup/list_of_alerts?observed_only=1. From these pages you can also see the light curves for those alerts which do have followup data. Here is the example of the light curve: http://gsaweb.ast.cam.ac.uk/followup/get_alert_lc?alert_id=2999

Source code

The calibration server is written in python using Flask framework. If you'd like to help/implement something, ask Sergey Koposov for the access to the git repository on http://bitbucket.org