meteorology – A Darker View

We were just setting up the telescopes when I looked up and spotted it.

Waikoloa School was hosting a community picnic, a couple bands, food, performances by a karate club and a halau, plus a few telescopes provided by Keck and the West Hawaii Astronomy Club. It promised to be a fun evening.

What I spotted was a hole-punch cloud above the school. OK, that was unexpected. A high thin layer of altocumulus perforated by a neat circular hole.

The hole had a thickened edge as if something had pushed the cloud layer aside. Otherwise it was completely clear in the center and nearly perfectly circular.

Hole punch clouds are often formed when something passes through a cloud layer, such as an aircraft, disturbing and destabilizing it. This does not appear to be the case here, rather I would guess that an updraft from below pushed its way into this particular cloud from below.

The hole was short lived, fading in about 15-20 minutes as the cloud layer reformed.

One of the miscellaneous systems in the observatory that I have inherited is the weather station. A critical set of gear that has been neglected far too long. Neglected to the point our telescope operators had been complaining, loudly, about a system that frequently gives erroneous data or provides wildly oscillating readings.

Weather mast covered with several inches of ice — The Keck weather mast covered with several inches of ice

The weather station is critical in protecting the all important optical surfaces of the telescope. The mirrors that gather light from distant galaxies depend on a thin coating of aluminum that is easily damaged. Snow, ice, fog or even simple dew can damage the coating and require the mirror segments to go through a laborious re-coating process. Thus the operators monitor the weather closely, when fog and humidity roll in, alarms go off, and the great shutters are closed to protect the telescope.

The first part I have replaced is the humidity and dew point sensor. In many ways the most important part of the system. The new unit is a modern sensor with a direct ethernet interface, simple to link into the observatory network. This is the same sensor used by the National Weather Service in their remote weather stations. All I had to do was spend a little money, and spend a day hanging off the weather tower on the observatory roof installing it. It was a beautiful, warm, sunny day up there, I got the job done, and got a slight sunburn in the process.

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