|Links||UNC Skynet||20m skynet interface||Log of 20m results.||NRAO Skynet main||observing advice|
Details for various kinds of observing projects
|Main Observing Advice||Mapping/Imaging Advice||Spectrum Observing Advice||Pulsar observing|
the mode is selected in one of the "Add Radio Observation" dialogs:;
Select High Resolution Mode Set the two frequencies to 1420 and 1420 MHz Set Number of channels to 1024 or 4096 Galactic Hydrogen on the galactic plane: pattern: Track; duration: 60 seconds; integration time: 1 sec Extragalactic objects: pattern: On/Off; duration: 200 seconds; integration time: 1 sec; Offset: 3 degrees And repeat the on/off 4 or more times. Calculate the frequency of the HI line for the velocity of the object, and set one of the frequecies (or both) to that frequency, in MHz.
Select High Resolution Mode Set the two frequencies to 1664 and 1664 MHz Set Number of channels to 1024 or 4096 Select a source that is likely to have OH emission such as Orion A or W3 Pattern: On/Off; duration 120 seconds; integration time 1 sec; Offset: 4 deg. For both HI and OH: Set the two frequencies to 1418 and 1668
NOTE: in high resolution mode, it is not recommended to do maps or daisies, as there is no software available to process such data. If you do mapping in high resolution mode, use integration time recommendations from the mapping advice page.
|Receiver||Feed||Filter||Center Frequency||Available Bandwidth|
|Rx1_2||21cm||1355-1435 MHz||1395 MHz||80 MHz|
|Rx1_2||18cm||1600-1730 MHz||1680 MHz||100 MHz|
|Rx8_10||3.3cm||8000-10000 MHz||settable by user||500 MHz|
|Rx1_2||21cm||1000 + n*15.625 MHz|
|Rx1_2||18cm||2000 - n*15.625 MHz|
|Rx8_10||3.3cm||Fc +250 - n*15.625 MHz|
You may enter any desired two frequencies into the Skynet web form, and the actual frequencies used will be the closest possible ones. For example, if you specify 1420 MHz, the band will be centered at 1421.875 MHz.
The same filters as listed above are used in both modes; thus if the 21cm feed
is in use, the frequencies should be between 1355 and 1435 MHz.
Number of Channels
The number of channels may be selected from the following table, which shows the channel spacing in each case.
|Number of Channels||channel spacing in frequency||velocity spacing (21cm)|
|1024||15.26 kHz||3.22 km/sec|
For high resolution data the display looks different from what you are used to for low resolution. Here is an example for a daisy scan on Cass-A.
|Example quick-look web display for a high resolution observation|
Track: In the Skynet web form, you need to specify the duration of the track, and the integration time.
On/Off: The duration is the time to spend on the source and the time off source, so the total time for the observation is twice the duration.
The "On/Off" pattern is used for fainter sources, in which the "off" data needs to be subtracted from the "On" data in order to emphasize the spectrum of the desired object.
Some handy quick advice:
| For observing the 21 cm line of Hydrogen
Set the two frequencies to 1421 and 1405 MHz Set Number of channels to 1024 or 4096 Galactic Hydrogen on the galactic plane: pattern: Track; duration: 60 seconds; integration time: 1 sec (use longer duration for better signal-to-noise) Extragalactic objects: pattern: On/Off; duration: 200 seconds; integration time: 1 sec; Offset: 3 degrees And repeat the on/off 4 or more times.