If you intend to observe minor solar system bodies (minor planets or comets), you should execute script UpdateEph, which downloads ephemerides for objects of interest from the Minor Planet Center (MPC) web site and adds them to the moving object database.

Since this will be the first time you run UpdateEph, you should take some time to customize the script to suit the needs of your telescope's users. This is done by editing the text file TAO\targets\UpdateEph.cfg, whose contents are shown below:

startOffset = 0                     ' Start ephemeris no later than now + N hours
UToffset = 0                        ' Offset of computer clock with respect to UT (hours)
obsCode = 860                       ' Observatory code
maxIntrpDist = 60.                  ' Maximum allowed displacement (arcmin) of objects between two 
                                    ' ephemeris dates
timeOut = 240.                      ' Timeout for ephemeris requests to the MPCES (sec)
autoDownloadUnusualMPs = True       ' True to automatically download ephemeris for unusual minor 
                                    ' planets which are not in the local ephemeris database; False 
                                    ' otherwise
magLimUnusualMPs = 19.              ' Limiting magnitude for the automatic download of ephemeris 
                                    ' of unusual minor planets not in the local ephemeris 
                                    ' database; ephemeris will not be downloaded for unusual 
                                    ' objects currently fainter than this limiting magnitude even 
                                    ' if they are not in the local ephemeris database. This option 
                                    ' has no effect if the previous option is set to False
autoDownloadComets = True           ' True to automatically download ephemeris for observable 
                                    ' comets which are not in the local ephemeris database; False 
                                    ' otherwise
cometRenewPeriod = 7                ' Automatically renew comet ephemeris which are older than N 
                                    ' days (even though they may have not expired yet)

The various parameters which may be specified in this configuration file are explained below:

• startOffset. This parameter (expressed in hours) specifies that new downloaded ephemerides will have start dates which are no later than the current time plus the specified number of hours. For example, if startOffset = +3, then new downloaded ephemerides will have start dates which are no later than the current time + 3 hours. Note that ephemerides downloaded from the MPC web services always start at 0h UT.

• UToffset. This is the offset of your computer's clock with respect to UT (expressed in hours).

• obsCode. This is your observatory's MPC observatory code. If you don't have an observatory code, you may use a nearby station's code.

• maxIntrpDist. The TAO scheduler computes the positions of solar system targets by interpolation on the topocentric ephemerides stored in the moving object database. This parameter (expressed in arcminutes) serves to adjust the interpolation accuracy. For example, if you set maxIntrpDist = 60, UpdateEph will adjust the time interval between successive dates in each ephemeris it downloads from the MPC web site so that the angular displacement of the object between two successive dates is at most 60 arcminutes. In this way, fast-moving objects such as NEOs close to the Earth will automatically have ephemeris with higher temporal resolution than slow-moving objects. Higher interpolation accuracy is obtained by decreasing the value of maxIntrpDist.

• timeOut. This is a timeout value (expressed in seconds) for ephemeris requests to the MPC web site. For example, timeOut = 240 means that UpdateEph will wait for 240 sec after sending an ephemeris request to the MPC web server before giving up on that request. The value of this parameter should be considerably larger than the average time it takes to receive the output of an ephemeris request from the MPC web site.

• autoDownloadUnusualMPs. If you set this to True, UpdateEph will automatically download ephemerides for unusual minor planets (NEOs, Centaurs, trans-Neptunian objects, etc.) which are not present in the local moving object database. This option is very useful to maintain your database up-to-date in an automated fashion: newly discovered unusual objects and objects which become bright enough to be observed will be automatically added to the database whenever UpdateEph is executed (which may be done automatically at regular intervals as a Windows Scheduled Task).

• magLimUnusualMPs. If you set autoDownloadUnusualMPs to True, UpdateEph will only automatically download ephemerides for unusual minor planets which are currently brighter than this limiting magnitude and which are not on the moving object database. The current magnitudes of unusual minor planets are read from the complet list of dates of last observation of unusual objects at the MPC web site. Since these magnitudes may be inaccurate, you should set this limiting magnitude to perhaps one magnitude fainter than your actual limiting magnitude. If you set autoDownloadUnusualMPs to False, this parameter is ignored.

• autoDownloadComets. If this is set to True, UpdateEph will automatically download ephemerides for all currently observable comets which are not present in the local moving object database. This option is very useful to maintain your database up-to-date in an automated fashion: newly discovered comets and comets which become observable will be automatically added to the database whenever UpdateEph is executed (which may be done automatically at regular intervals as a Windows Scheduled Task). Observable comets are here defined as those listed in the list of dates of last observation of comets at the MPC web site.

• cometRenewPeriod. Expired ephemerides are always automatically renewed (by downloading new ephemerides with a near-current start date) by UpdateEph. However, to ensure that the comet ephemerides in the database were generated from the latest orbits, it is useful to periodically download new comet ephemerides, even though they may have not expired yet. This parameter specifies the maximum age (in days) which a comet ephemeris may have before a new ephemeris is downloaded. An analogous parameter for minor planets is not necessary because UpdateEph automatically reads the Daily Orbit Update MPECs and downloads new ephemerides for all minor planets in the database whose orbits have been updated.

Save the file TAO\targets\UpdateEph.cfg after you have edited it. Open a DOS window (Command Prompt) and cd to the TAO\targets directory. To review the command line options for script UpdateEph, type the command

C:TAO\targets\>cscript UpdateEph.vbe ?

This will print the following help information:

Microsoft (R) Windows Script Host Version 5.6 Copyright (C) Microsoft Corporation 1996-2001. All rights reserved. Usage: cscript UpdateEph.vbe file Argument: file A text file containing a list of designations of minor planets and/or comets, whose ephemeris will be downloaded from the Minor Planet & Comet Ephemeris Service. If the file argument is omitted, the script will perform a fully automated update of TAO's local ephemeris database. If the file argument is a question mark (?), this help information will be printed.

To start the automated initialization of the moving object database, type the command

C:TAO\targets\>cscript UpdateEph.vbe

The script may take a pretty long time to execute, since it may have to download ephemerides for a large number of objects. Subsequent updates will usually be much faster.

After the script executes you will see a screen message like this:

Logs written to: UpdateEph_20030930_213941.log Split_UpdateEph_EphToUpdate_FileList.log

These log files will contain a detailed record of the initialization process, including error messages. Both log files will be found in directory TAO\targets. You will notice that after the database initialization the TAO\targets directory will contain a number of files with extension .elm and/or .vsl. These plain text files contain ephemerides for individual objects. Ephemerides are downloaded from the MPC web site in blocks of up to 30 objects, and are then split by UpdateEph into individual ephemeris files.

If some of your minor planet targets are not considered unusual by the MPC, you may take this opportunity to add them to the moving object database (you may also choose to add them later, when you update the moving object database). To do this, you should prepare a text file listing the designations of the minor planets you wish to add to the database. One example file would be

(13421)
2003 SR128
2002 CH43
2000 TV51

Let us suppose that this file is saved to the TAO\targets directory as myObjects.txt. To add these objects to the moving object database, you would type the command

C:TAO\targets\>cscript UpdateEph.vbe myObjects.txt