Carl Sagan taught me that our Galaxy is always spelled with a capital G. Here it is. I used a slightly different technique with my Canon to get this image. I have an old 135mm f/2.8 lens with a thin M42 to Canon adapter. I thought this lens was no good, but aha! I was assuming that setting the lens to infinite focus gave infinite focus, mainly because it looks to all intents like it is throught the viewfinder. However, a slight tweak to the focus ring and it gives sharper focus. Still not perfect, but at least it does focus; it could have been out the other way and never reach infinity. Anyway... I'll stop that laborious explanation and say how I enjoyed polar scope aligning and then polar aligning an Autostar mount. I then piggybacked the camera on a scope and pointed it out of the dome to the beautiful summer milky way. I worked at ISO 800 so I could get longer exposures (6 x 1' plus a 2'). I think the trick was to get flats 'in situ' as well as darks and flat darks. These were obtained by scrunching a bit of bubble wrap in front of the lens and repeating 5 blurry shots close to the same area, covering the camera for 5 seconds when cars came past. I had to stack using 'Kappa-Sigma clipping' as opposed to 'Mean' even though one of the pics was 2 min and would effectively get ignored. Is that right? ... OK. Now let's play spot the objects!
Monday, 12 July 2010
Looking across our Galaxy
Carl Sagan taught me that our Galaxy is always spelled with a capital G. Here it is. I used a slightly different technique with my Canon to get this image. I have an old 135mm f/2.8 lens with a thin M42 to Canon adapter. I thought this lens was no good, but aha! I was assuming that setting the lens to infinite focus gave infinite focus, mainly because it looks to all intents like it is throught the viewfinder. However, a slight tweak to the focus ring and it gives sharper focus. Still not perfect, but at least it does focus; it could have been out the other way and never reach infinity. Anyway... I'll stop that laborious explanation and say how I enjoyed polar scope aligning and then polar aligning an Autostar mount. I then piggybacked the camera on a scope and pointed it out of the dome to the beautiful summer milky way. I worked at ISO 800 so I could get longer exposures (6 x 1' plus a 2'). I think the trick was to get flats 'in situ' as well as darks and flat darks. These were obtained by scrunching a bit of bubble wrap in front of the lens and repeating 5 blurry shots close to the same area, covering the camera for 5 seconds when cars came past. I had to stack using 'Kappa-Sigma clipping' as opposed to 'Mean' even though one of the pics was 2 min and would effectively get ignored. Is that right? ... OK. Now let's play spot the objects!