Manual Observing


Joachim Köppen Strasbourg 2010


Operating the telescope manually is the best way to learn how to use the telescope, what data it records, what problems exist, and all the rest of the real life of observing!

After you have started up the system described here, and waited for the first spectrum displayed at the stow position, it is a good idea to watch the displayed power which is averaged over the spectrum.

Under normal conditions the power level in the stow position will be in the ballpark of 2000 cts. In this position the telescope points to the wall of the library, which radiates thermal emission, like a 290 K blackbody. Pointing it to the 'empty' sky gives about 1500 cts.

A major part of the software's screen is covered by a display of the sky as viewed by the telescope. The shaded areas show buildings and trees which obscure the view. The rectangle with red lines indicates the region outside which the telescope is not permitted to be moved. A number of sources are marked:

Clicking on one of the dot sources will make to telescope move to that position. It may take some time to reach the position.

If you want to move to a certain azimuth and elevation, enter the numbers in the textfields at top right and hit the 'return' key.

Important: The antenna is slightly offset from the real AzEl positions. At the moment, we simply enter the values -0.5 and -3.5 in the textfields labeled PointCorr and hit 'return' key. Since the telescope actually looks up in elevation by 3.5 degrees, this will ensure that it will now point in the exact position given by AzEl ... although from the map you find that it appears to point somewhat below a source!

The sources displayed in the sky view are determined in the file 'srt.cat'. You can open this file with a text editor and change or add sources. The keywords and the syntax are explained on one of the pages in the Help menu. For instance, adding the galactic position of l=180 and b=-4 would require the entry
GALACTIC 180 -4 G180.4n
where the last string is the name under which the source is displayed. Having saved the srt.cat file, you click the reReadCat button. The display will then be updated. One hint: do not reread the catalog file while you are measuring a source, because of the renumbering of the source list the telescope may move to the source that received the same number as your original source.

Once you started the software, it will measure the spectrum all the time in regular intervals (about every second in the mode with 500 kHz). It will display the spectrum and the power, but it does not record data in a file, unless you click the Record button and its text appears in blue colour. In manual mode one can easily forget to do that, and you would lose precious and useful data. (BTW: It happens to everyone! ;-)


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last update: Apr. 2010 J.Köppen