Varuna occultation from Stellenbosch (2010 Feb 20)

posted: 2827 days ago, on Wednesday, 2010 Feb 24 at 06:03
tags: astronomy, occultation, Stellenbosch.

For weeks leading up to the morning of February 20, there was a buzz about an upcoming occultation of an 11th magnitude star in Gemini by Varuna (once a god of the sky in Vedic tradition, now a minor planet and maybe even a dwarf planet).

The predicted track would was just north of Cape Town, but it's always good to confirm a southern limit. With this in mind, Dr Dieter Willasch in Somerset West would provide the necessary observations.

However, it became apparent that at the time of the event, the altitude of the little star would be too low for Dieter's observatory, so the troops were mobilized.

We finally settled on the Stellenbosch Flying Field as an impromptu observing site. The aerodrome's co-ordinates are S 33° 58' 50", E 18° 49' 22" at an elevation of 106 metres.

Our group setting up: (from left-to-right) Dieter Willasch, "Maphefo" with her red light, Ernst Jordaan with "Palesa", Edward Foster with "Lorenzo", and Martin Lyons with his 9-inch SCT.
Also visible on the photo are Castor and Pollux, Mars at upper-centre, and the light pollution seen towards Stellenbosch (some 10km away).

One logistical problem included getting a useable time signal, since I was observing visually.

The solution was to make a video of the events, as follows: set your cellphone to its stop watch function (which should give split-second readout), and place the cellphone next to a laptop (or in this case, Martin's iPhone) that is displaying UT updated live over the internet. Keep the video recording, and take camera and cellphone back to your telescope. All your comments will be recorded on the audio track, while the video track of course shows the time on your cell phone's stop watch display.

In this way, I was able to record that I was constantly seeing the 11th mag target star from 01:00:58 SAST (23:00:58 UT) until 01:21:00 SAST (23:21:00) positively confirming a southern limit to the occultation. I was using "Maphefo" (an 8-inch Dobsonian) and the star was plainly visible throughout.

See Prof Bruno Sicardy's web page for further details.

nothing more to see. please move along.