Wednesday, 20 August 2014

Zubenelgenubi gets some guests!

While testing my planetary imaging demo for the talk I'm giving next month (see: ) I spotted Saturn and Mars setting in the South West. I got a snap and looked at the image and spotted a star. I then ran across the field with the tripod to get a pic of the planets above the dome and observatory. So not such a 'far away thing'. It's one of those mind-blowing distance ratios. I also caught Andy walking back to the observatory who came back telling me the star was alpha Librae - aka Zubenelgenubi, my favourite star name! So from top to bottom we have Saturn, Zubenelgenubi (alpha-2 and alpha-1 next to it) then Mars. A beautiful scene I realised when processing it to bring out the faint details, giving pleasing pastel shades on the sky. Just 1/4" second exposure at ISO 1600, I had to turn the gamma down again as blogger overdoes it!

Comet E2 Jacques

A night at the observatory and a moonless clear spell coincided! Not wanting to waste the opportunity I wheeled the society's new iOptron mount out and set up the 9.25inch Schmidt with the help of a busy crowd. I put my modified Canon on the back of it along with a f/6.3 focal reducer. Time constraints meant a full perfect drift-align wasn't possible, so I limited exposures to 30 seconds to reduce any star trails. Auto-guiding is not quite ready with this set up yet, but once we get the equipment together, beautifully long exposures will become possible! During the 20 minutes or so it took to get 22 good exposures, Comet Jacques had slid past a star and moved quite considerably! This required a special star then comet stack in Deep Sky Stacker. The result had a fair bit of star ghosting in the direction of the comet's motion and there is still a small ghost of the comet's nucleus left in the image that I couldn't remove easily. Several runs through Carboni's horizontal and vertical banding removal routine got rid of the bias pattern noise in the camera sensor, but the faint ghost trails were still a little annoying. I tilted the image until these trails were horizontal and ran another horizontal banding removal routine on the image. Then I tilted it back. Above's the result, and below with the faint parts smoothed. Not too much exposure, but am I right in thinking there's a hint of a tail to the right at about 110º CW from vertical? The green emission in the coma ('swan bands' in the spectra) comes from the molecules C2 and CN and their positive ions.