Thursday, 6 June 2013


For a change, I'm adding a planetary image, obtained using the society's Celestron 9.25" f/10 Schmidt-Cassegrain Telescope. I used the society's Imaging Source DBK camera and IR block filter in a 2x barlow lens, slid back to achieve more like 3x, thus giving a focal length of about 7m at f/30. This telescope works better for planetary detail than the stopped down 20" f/4.8 Newtonian, although it had to sit outside for well over an hour to cool to reduce internal air currents, while seeing also slowly improved. I recorded about 2000 frames at 1/30" on high gain and stacked the best 40% or so using Registax 6. This was taken a little after opposition (when Earth passes between the Sun and Saturn) on 7th May, at 21:31UT.

Asteroid 1998 QE2 drifts silently by

Here's around 50 minutes of footage of the asteroid 1998 QE2 drifting by us on the evening of the 2nd of June. I recorded 10 second exposures with intervals of 30 seconds on the 20 inch telescope, as the 11th or 12th magnitude asteroid culminated in the southern sky, in the constellation of Libra. You will see the imperfections in the tracking of the stars, and the apparent rotation, as the mounting is Alt-Az (altitude-azimuth, i.e. up-down left-right). The field is about 38 arc minutes across. The asteroid is quite large, much larger than the actual QE2, so it's a good job it passed a few million miles from us. Look out for the 'flash' of a (man-made) satellite trail and a(nother man-made) geostationary satellite near the end of the sequence. The geostationary satellite appears to move but in reality the right-to-left motion is because the stars are being tracked.