Daily Image
18-04-2023
A week of hydrogen
| Submitter: | Tammo Jan Dijkema |
| Description: | This image shows about one week of spectra from the Dwingeloo telescope, in drift scan mode. That means, the telescope was not moving, and pointing at its 'show position' at 30 degrees elevation, 30 degrees azimuth from South, i.e. south-southwest. Some interesting features are visible in this plot. Every day around 6:30UTC, the Galactic plane passes through the beam of the telescope, at a galactic longitude of about 29.4 degrees, close to the Galactic center. In the evening, around 19:00UTC, the galactic plane passes the beam again, this time at galactic longitude 216.4 degrees, away from the Galactic center. At both times the Galactic plane passes through the beam, hydrogen emission from other spiral arms is clearly visible. The times the Galactic plane passes through the beam nicely shift forward by 4 minutes every day, as expected. Also visible is a nice sinusoidal shape of the hydrogen line. This is caused by the rotation of the Earth around itself and around the Sun. The Sun itself is probably visible as the continuum features symmetric around 13UTC, which is the time the Sun passes closest to the beam (10 degrees above the beam). This marks this the n+1-th time that I have 'discovered' the Sun in radio. Some more mundane features of the plots show that it is hard to keep a system running for a week. Black patches in the plot are where the observation was not running (for example, during a tour of the telescope). There are dark spots in the graph where the system was running, but for some unknown reason a relay in the receiving chain switched itself to the wrong position, causing the signal to drop completely. While trying to debug this issue on Saturday, the system got into a state where an amplifier started oscillating, causing the system to be oversaturated starting 15 April 17:15 UTC (when everyone just wanted to go home for dinner). We are currently debugging this issue. A last very unwanted feature is some spikes of interference at 1421MHz. This is certainly caused by equipment in the telescope or the test field. This feature is present in the entire observation (except where the relay was in the wrong position), but varies in intensity. We are trying to find the source of this interference, since the protected radio astronomy band around the hydrogen line should be kept very quiet, specially in a radio quiet zone. |
| Copyright: | CC-BY 4.0 CAMRAS / Tammo Jan Dijkema |
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