Monthly Archives: January 2011

Piggyback adventure

Orion, piggyback with Fuji S9500 at 28 mm, stack of two 30 second exposures, ISO 1600 with dark frame removed

Imaging a wide field of view of the sky and overcoming the problem of star trails can be achieved by piggybacking a camera on top of a telescope on a motorised equatorial mount. Things never being straightforward there was no obvious way to easy way to achieve the piggyback with the equipment that I already had. However, this was rather straightforwardly resolved by buying an additional mounting ring and piggyback camera mount direct from Orion Optics.

The maximum exposure time on my Fuji S9500 is only 30 seconds, even on the B setting, however I set out not thinking that this would be a problem since I was intending to stack multiple images allowing me to throw away any ruined by stray car headlights and the build up of thermal noise. To compensate for the “short” 30 second exposures it is always possible to increase the cameras ISO setting (it’s rather quaint still using this description from the days of film, increasing the ISO setting is of course just increasing the gain applied to the signal captured by the cameras CCD).

Pleiades, piggyback with Fuji S9500, stack of three 30 second frames at ISO 1600 with dark frame removed

Now, how long do I need to wait for a night that is clear and dark? It’s Friday night and it has been a long week and a very long day, one final look outside to see if the cloud has cleared before going to bed… I see stars! Tiredness disappears, telescope and camera appear!

After failing (probably due to haste) to get the Synscan EG3 goto mount aligned with a 3-star alignment, a quick check of tripod and better alignment with Polaris, followed by a 1-star goto alignment and we are off! The 1-star alignment seems perfectly adequate. There’s a bit of cloud around so I hop to the easy target of the Pleides first and snap a few images with the new piggyback mounted camera. Next I slew across to the Orion Nebula, what a glorious site through the 20 mm eyepiece. I do a couple more experimental piggy back shots of Orion, then with midnight approaching and tiredness catching up I take a quick look at the Andromeda Galaxy before packing up for the night.

Pleiades - NASA/courtesy of

There are some lessons learned from this experience:

  • a bit less speed in setting up the tripod and mount;
  • I need curtains in the garden to stop stray car headlights (this is not a joke!);
  • use of the cable release on the camera is better than pressing the button by hand;
  • Long exposure, but lower “ISO” is probably the way forward;
  • A little way to go to match NASA…