Phase 2 Proposal Instructions for Cycle 10

3.6 Source of Specified Coordinates
[Coordinate_Source]

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In this field please specify the source of the celestial coordinates that you list for each target. Most faint targets will use ÒOther_Source.Ó Valid entries are:

Guide_Star_Catalog

To be used if the source is the HST Guide Star Catalog. Include the Plate ID (from the ÒPltÓ column in the GSC) with your coordinates. Note: If the Plt value is 56, then the true source is the Hipparcos Input Catalogue, which should be listed (see below, and please note that Plate ID should not be specified).

GSC_Survey_Plate

To be used if coordinates were measured from a Guide Star Catalog survey plate. Include the Plate ID with your coordinates, taking it from the PLATEID keyword in the FITS header.

HST_Image

To be used if coordinates were measured from an existing HST image. Include the Plate ID, which can be determined from the guide star IDs listed in the observationÕs Standard Header Packet. All HST observations have at least one guide star ID in the Standard Header Packet (SHP). SHP data are in the _jif.fits file for WFPC2 observations, or in the .spt file for STIS data.

The guide stars that were used during any pointing of HST will be recorded in the SHP as character strings associated with specific header keywords. The primary, or dominant, guide star is given by the GSD_ID keyword, while SGESTAR lists the secondary, or sub-dominant, guide star. The guide star ID is a concatenation of the star number, the region number (from the Guide Star Catalog), and the particular FGS used in the pointing. For example, Ò0123406789F2Ó means guide star 01234 06789 was used with FGS2.

To find the Plate ID, go to the GSC web site:

• http://www-gsss.stsci.edu/support/RGSCID_FORM.html

The form will prompt you for the guide star ID (in two fields); you should use only the primary guide star. You should then be given the coordinates, estimated magnitude, associated errors, flags internal to the catalog structure, and the PLATE-ID. For most guide stars there will be multiple entries (and multiple PLATE-IDs because the fields of the plates overlapped. The first line of the output lists the primary plate, and this is the one you should list.

If the observation used only a single guide star then it is possible that a a secondary plate was used; contact your Contact Scientist.

Image_Tied_To_GSC_Frame

To be used if you measured several visible stars on a Guide Star Catalog survey plate and then used them to determine pseudo-GSC coordinates for a target imaged with another telescope. Include the Plate ID (from the PLATEID keyword in the FITS header) with your coordinates.

PPM_Star_Catalogue

To be used if coordinates are from the PPM (Catalog of Positions and Proper Motions).

Hipparcos_Input_Catalogue

To be used if coordinates are from the Hipparcos Input Catalogue, or, equivalently, they are from the Guide Star Catalog and the ÒPltÓ column lists Ò56Ó (in this instance please do not specify plate ID). Because of systematic differences in coordinates, we urge you not to use the HIC as a coordinate source; the Hipparcos/Tycho Catalogue should be used instead.

Hipparcos/Tycho_Catalogue

To be used if the coordinates are from the Hipparcos/Tycho missions. Note that coordinates from the Hipparcos/Tycho_Catalogue have equinox J2000 but epoch 1991.25. This earlier epoch means that it is important to provide a proper motion for your target if it is at all significant. In some cases the Catalogue of Positions and Proper Motions (PPM) may be a better source for proper motions because of its longer time baseline.

Other_Source: <text>

To be used if none of the above apply to your coordinates. You must include a short description of where the coordinates are from, for example:

Coordinate_Source: Other_Source: HDF Catalog (Williams et al. 1996, AJ, 112, 1335)

The explanation cannot be very long, and so we recommend an entry like ÒCoordinate_Source: Other_Source: See commentÓ if you need more space.