deepS82

A sky map of deep SDSS Stripe 82 imagery

About

This software provides an interactive skymap of SDSS stripe 82 based on leafletjs and fitsjs. See https://deepS82.aspect-ui.de for a running setup.

Features

• panning in the map
• go to celestial coordinates (RA, DEC decimal) by the coordinate search on the left (magnifier symbol on the right)
• jump to coordinates by URL-Parameters: e. g. [http://deeps82.aspect-ui.de/map.html?ra=333.7997&dec=-0.7638]
• set minima and maxima values for plotting from the original fits files (contrast symbol on the right)
• click into the map and get popup showing RA, DEC and Links to SDSS Explorer/Navigator for the clicked coordinates
• extracting regions as fits files by the use of the selection tool (rectangle/circle under the still unfunctional +/- buttons in the upper right)

Planned features (in no particular order)

• change plot limits by mouse click and move similar to what DS9 provides
• user defined base for log plotting
• more plot scales (linear, quadratic, ...)
• more intuitive limit definition for inverse plotting
• automatic horizontal or vertical panning with user defined speed
• Zoom in/out

Setup

The software only provides the interface. The image data has to be generated. The setup at https://deepS82.aspect-ui.de is based on the the data of (http://www.iac.es/proyecto/stripe82/).

This data consists of 1100 FITS files of size 4553x4553 pixels, the naming scheme of which is described in section 3.1 in the paper (http://www.iac.es/proyecto/stripe82/media/2016MNRAS.456.1359F.pdf). These FITS files are way too large to be downloaded and rendered by a browser. To this end each of the FITS files was cut into 29 by 29 cutouts measuring 157 by 157 pixels. DeepS82 expects these files in a directory structure named according to

/tiles/FIELD/X-Y.fits

where FIELD has to be replaced by the FIELD identifier as described in the mentioned paper and X and Y are the coordinates of the cutouts within the field. X and Y each range from 0 to 28.

Preparation of the images

• install Swarp (is included e.g. in Fedora, Ubuntu package repositories)
• install Montage (is included in Ubuntu package respository, easy to make and install in Fedora)
• download FITS images for the appropriate filter from source mentioned above
• create swarp.default config file with background subtraction set to N and useful projection, e.g. AIT (See the SWARP documentation for other projections
• run SWARP on the downloaded FITS files, the result is one large FITS image of Stripe 82
• use montage's mSubimage to create tiles in the needed size, the result is the image tiles needed for the web frontend [TODO: provide command line example]