Observing from Dubai

Jeremy Shears

When I was asked by my company if I was interested in an assignment to the Emirates, I thought that with a latitude of 25° N and a desert climate, it should be excellent for observing. Indeed, the first time I went out into the desert to a truly dark site I was amazed by the huge number of faint stars, and confused by the enormous star clouds in the Sagittarius–Scorpio region. They really do look like storm clouds approaching from the south! However, observing from Dubai itself is not without frustration. Firstly, the light pollution is terrible (I had previously lived in Belgium – one of the most light-polluted countries in the world), and it is necessary to go some distance outside the city to encounter really dark skies. However, if a barbecue is taken an enjoyable night can be made of it, so long as the ubiquitous (but not very inquisitive) camels keep their distance. I try to restrict the use of torches to a minimum, as the light attracts huge camel spiders. The guide books say they are harmless, but I do not want to get close enough to find out! Other hazards are the heat and humidity, which preclude any serious observing from June to September. Even in the middle of the night the temperature can still be 35° C (it is more than 45° C during the day), with humidity levels around 100%. During the rest of the year, however, shorts or thin trousers can be worn all night.

Instrumentation In spite of the light pollution, I carry out most of my observing from my garden in Dubai. The main telescope is a Celestron C8 on a Vixen Super Polaris mount. This is an excellent mount, and performs well, even though it is somewhat overloaded with equipment (I may one day upgrade to the DX). The mount is very rigid – especially as it is supported by a pedestal rather than a tripod – and the motors are very accurate, with very little periodic error. In fact, I prefer German equatorials to fork mounts, especially when different instrument configurations are required, and would not hesitate to recommend this set-up. The mount is controlled by a Vixen Skysensor 3D computer which allows GOTO control. This control unit was available long before the Meade LX200, although the search speed of the Vixen is slower. I can usually place a new object somewhere on my CCD chip at the first attempt, so it really helps with finding objects. Vixen has recently launched the Skysensor 2000PC, which appears to be a serious contender to the LX200. The telescope is normally fitted with an f/6.3 focal reducer, as for most of the time it is used for imaging or for visual observation of deep-sky objects. There is a 60-mm finder/ guidescope of 420-mm focal length. Many deep-sky objects can be seen in this directly, which also helps in locating them. I thoroughly recommend a large-aperture finder (I may upgrade to the 70-mm Vixen). I also use a Telrad finder in the intiial finding stages. Normally I associate these useful units with large Dobsonian light buckets, but they are perfect for use with the C8, as the tube is too short to sight along easily. Because of the light pollution, I also employ a Dewstar dew cap. I leave the mount outside, so it is always permanently polar aligned. It is protected from the elements (such as dust and the Sun) by an inverted dustbin, the lid of which has a hole to accommodate the pedestal (the lid can be seen in the photograph). When I want to observe, I remove the dustbin and place the C8 tube on the mount, a procedure which takes about five minutes... nearly as good as having an observatory.

CCD imaging

Last year (1997) I bought a Starlight Xpress SX CCD, but have only recently had sufficient time to experiment with it, and the images presented here are some of my first results. I use a Toshiba P133 lap-top to control the camera and capture the images. Processing is carried out later on a P200 in my study. As I travel a lot, I quite enjoy passing the time on aeroplanes and in airports by doing some image processing. Although I have really only just started, using the camera is easier than I thought, although proper focusing is a constant challenge. I tend to use the SX ‘track and accumulate’ option. which allows automatic stacking of multiple exposures, typically of 15s duration. However, because of the relatively high ambient conditions here, it is difficult to cool the camera below –15° C, even with the optional cooling fan.

M2 and M15. 1998 November 7. Each image obtained with ten 15-s exposures.