Introduction

Other digitised sky survey material from similar machines is available for a variety of broad-band surveys. However the SuperCOSMOS Sky Surveys should be particularly valuable to astronomers for several reasons:

1. The pixel size is 10 micron (0.67 arcsec), much smaller than the old DSS-I (25 micron) and still smaller than the new DSS-II (15 micron).

2. Pixel images and object catalogues (to the full exposure depth) are available together in a single FITS file. We recommend using the GAIA software package, which can browse the image and associated catalogue simultaneously in a convenient way.

3. Colours, proper motions, and variability information are available for the first time in the general SuperCOSMOS digitised sky surveys.

4. Specifically here we make available access to the new H-alpha survey of the Southern Galactic Plane which offers a combination of area coverage, sensitivity and depth that is currently unsurpassed in a survey of galactic gaseous emission in terms of these combined properties.

GALACTIC PLANE COVERAGE. Eventually the whole Southern Galactic Plane and Magellanic Cloud regions will be available on-line covering over 4000 sq.degrees. Narrow-band H-alpha images are complemented by contemporaneous matching broad-band Short-Red (SR2) exposures taken on non-standard 4-degree field centres (due to the nature of circular aperture of the interference filter used).
Click HERE for more information on the special filter.

Both exposures were taken using fine-grained Tech-Pan film based emulsion which has improved resolution and depth c.f. traditional glass-based emulsions such as IIIaF. Further details of the properties of Tech-Pan can be found in Parker & Malin (1999).

Ultimately both the I-band and first epoch SR data (SR1) in the Plane will also be incorporated. These were taken on standard 5-degree field centres on glass plates with the IV-N and IIIaF emulsions. These data will additionally permit H-alpha-R and R-I colours plots for point sources in the Galactic Plane, whilst the first epoch SR1 will enable proper motions to de determined for many stars wrt SR2. These data will greatly assist in the identification of variables, true H-alpha emitting objects etc.

To view the Galactic Plane fields currently on-line in the matched H-alpha/SR2 pass-bands go to Galactic Plane coverage. The survey data will be released in tranches of contiguous regions but users may request special access to an individual field prior to general release if urgently required.

GENERAL SUPERCOSMOS SURVEYS. The whole Southern sky is already available in two colours (blue (UKJ) and red (UKR)). The South Galactic Cap (SGC, 5000 sq.degrees at b < -60) has been scanned in J(B), I, and twice in R. All these data are currently on-line. Data for the rest of the southern sky in I and ESOR are being placed on-line piece by piece. These surveys can be accessed here

A 5x5-degree square deep-field image centred at 21h28m -45 (UKST field 287) will be available soon.

STYLE OF ACCESS. There are four ways to access the SuperCOSMOS Galactic Plane data.

• GENERAL IMAGE/CATALOGUE EXTRACTION. Download a specified Galactic Plane region up to 30 arcmins across returning both the pixel image and associated object catalogue for the selected region. Note that by default only the H-alpha data are returned but the user may select either H-alpha/SR or both survey bands if desired.

  The object catalogue is selected on the fly from a larger database including any detections at the other wavebands currently available (e.g. H-alpha or SR2 and later I and SR1). Note that the IAM parameters in the object catalogue come from an Image analysis of the base SuperCOSMOS pixel data where the pixel data has not been Flat-Field corrected.

  If you select the H-alpha survey, your catalogue will have everything seen on the H-alpha exposure together with all the other available magnitudes (SR2, I, SR1) and a selection of associated IAM parameters, all retured in matched blocks of four columns for each parameter.

• LARGE CATALOGUE. Download object catalogue from a large area (up to 10 degrees across). Again, this is created on the fly from a larger database, taking one particular Plane survey as the base-survey. You can control the list of parameters returned.

• BATCH MODE. You can specify a disjoint list of regions (coordinates) to extract. Tar savesets of the images and associated catalogues are returned.

• ALL GALACTIC PLANE SEARCHES / ANALYSIS. It is not currently possible to download the whole database. However searches through the entire survey material can be done (e.g. "find all the objects brighter than X with proper motion larger than Y") by arrangement with the WFAU on our own machines - contact Mike Read (mar@roe.ac.uk) to discuss the possibilities. Later we hope to provide this as an automatic service.

DATA FORMAT RETURNED. If you specify that you want to see a GIF image you will see your piece of sky returned on the web page, but by default we just return the files for you to use with your own software. The images have 0.67 arcsec pixels and are returned in FITS format with a built-in World Co-ordinate System (WCS). The FITS file automatically contains FITS tables listing the associated object catalogues, and if your image viewer is smart enough (like GAIA) you can browse them simultaneously. However you can also download the catalogue separately.

The object catalogues can be returned either as FITS tables, ASCII lists, or tab-separated lists. Various database query and analysis packages (e.g. CURSA) can understand all of these formats. The parameters returned include the obvious things like RA, Dec, l,b, magnitude, ellipticity but also some less obvious but often useful things like image area, quality and blend flags, and so on.

More detail on all these issues can be found in the various sections in the menu bar to the left, especially under Documentation.