Early Autumn Skies

In Early Autumn, you can catch a nice glimpse of the Milky Way in dark skies, rising from the SSW, where we look into the centre of the galaxy. Unfortunately it is very low down so we look through a lot of interfering atmosphere and consequently light pollution (produced by either ignorant, paranoid, or uncaring folk that install inappropriate outdoor lights). Despite this impedance, the power of long exposures, stacking and a lens that runs at f/2 (stopped to f/2.2 in an attempt to cut down abberrations) can be used to produce a good image. Cloud, twilight and mist were threatening to spoil my attempt but the moon was out of the way at last! There is so little time for astronomers to get good viewing conditions we have to seize opportunities like this. I have stacked 7 x 1 minute images taken at ISO 800 tracked with an RA motor, with my modified Canon 1000D, with a 100mm prime f/2 lens from a quiet, dark site south of Norwich. The region is North Sagittarius/Scutum and it contains M24 - the sagittarius star cloud, M17 the swan nebula, M16 the eagle nebula, and numerous other nebulae and clusters.

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!