17th January 2010

M42 Nebula in Orion
10" Newtonian, Canon 350D, 77*30 seconds

The ten inch scope was used. Compare with image from January 2009 using the six inch.


Different processing


29th January 2010

Mars near opposition

John Clarke suggested on the SPA website that it would be interesting to image Mars during its 2010 close encounter, from different locations on the Earth. Parallax would enable a calculation to be made of how far away Mars was at the time. Some images are on his website here.

I managed to get some images on the 29th, 30th and 31st. Below is a composite of several images, superimposed on a DSS sky map.
  The weather was not kind to us. Very seldom did clear skies exist simultaneously at the various observing sites.
However on the 31st, Kos Coronaios in South Africa (Louis Trichardt) had clear skies and so did the UK.
  An image from Kos

One problem is that Mars is so bright that any shots long enough to get any background stars will have Mars very much over-exposed. My technique was to draw a circle over Mars and then find the centre.

  My reflector produces long diffraction spikes on Mars. The intersection should give a fairly accurate location for the centre of the planet.

  Kos took two images at times on either side of my image. Mars was moving across the sky at a fairly linear pace so it was possible to extrapolate (the blue dot) a position where Mars would have been at 10pm. My position is the red dot.

The distance between red and blue dots equates to 19.9 arcseconds. The distance between Kos and me was 8202km (straight line through the Earth). Making the assumption that this baseline is perpendicular to the line to Mars gives a distance of 84,858,612km.
The software Cartes du Ciel gave a value of 99,617,222km. This is an error of 14.8%.

Not quite up to NASA standards but a fun exercise!


On the 5th February the process was repeated. This time images were almost simultaneous, at 7pm GMT.
The distance to Mars came out as 125,402,168km. Cartes du Ciel gave a value of 100,694,414km.
Our average over the two days = 105,130,390km. Cartes du Ciel average = 100,155,818km
  Oleg Toumilovitch in Johannesburg took two images at 6:15 and 7:15 on the 31st. Extrapolating (green dot) showed where Mars would be at the time of my image at 10pm (red dot).

The parallax was 26.012 arcseconds. A baseline of 8393.7km gives a distance to Mars of 66,558,529km.

This is quite a large error, undoubtedly due to errors in the extrapolation process.
  An image of Mars, taken by Oleg on January 27th when Mars was at its closest to Earth.