Friday, 16 April 2010


We have a good range of planets up at the moment. I trained the recently collimated 235mm Celestron on all of them. I used a -5D Barlow I found lying around and took a few snaps of each planet on my Canon EOS 350D through it, giving a focal length of about 4.5m at f/20. Exposure bracketing was done and I stacked the best few images of each planet. After contrast enhancements and aligning the red, green and blue channels etc., I put all 4 together to compare size for size & colour for colour. I worked my way round the sky from twilight to opposition, i.e. in order of increasing Right Ascension hour. Then I checked out the view of Saturn. Very sharp! I saw a very interesting alignment of moons next to the rings (Monday 12th April), so checked it out on the 20". This was brighter, but fuzzier. I attempted to image the moons but the tracking / vibration wasn't good enough on either scope. Shame - there were four moons above 12th magnitude within about 3 arc seconds.

Saturday, 3 April 2010

The Whirlpool

This fine galaxy is filled with fascinating features. The Whirlpool galaxy (M 51) is now climbing high in the sky and can be found near the tail star of the Plough, Alkaid. It is not one but two galaxies, the second (NGC 5195) has been shown by computer simulation to have passed through the main one twice. I am pleased to have revealed in this image the glowing areas of stars surrounding NGC 5195 that are the result of the aforementioned collision. To get this image I have combined the 10 least trailed shots with 19 very badly tracked ones, which I detrailed using Paint Shop's Layer/Darken function. I stacked the first 10, then all 29, and processed them both separately, applying a careful smoothing blur to the faint areas. Only by stacking all 29 shots could I clearly see the filament shooting out at the top of the image. I then cropped both to the same area and blended them in the ratio about 2:1 in favour of the sharper 10 frames. The total exposure time was just 15 minutes at f/3. I was quite taken aback when my stacking program output showed me the extremely deep areas to the left, which have incredibly subtle contrast against the sky background.
Another great thing in this picture is the exceedingly thin splinter of IC 4277, a 16.5 magnitude galaxy hiding just to the left of the main galaxies. This has one of the highest aspect ratios I've seen although it has been a little blurred in the processing. IC 4278 is also here, lying below NGC 5195.
Imaging reveals so much more than the eye will ever see directly. Even the Sixth Earl of Rosse would never have seen anything like this when he made his famous drawing of this object on his 72-inch Leviathan telescope at Birr Castle.

Thursday, 1 April 2010

Equinox Sunset

Here, at 6 p.m. old local time on March 21st, our Sun is being refracted up over the horizon at the midpoint of its biannual, azimuthal journey (also known as due West). This astronomical occurrence is called the vernal equinox and has the historical significance of marking the transition to the growing season in the northern hemisphere. In this picture, as well as industry creeping into this once pure event, an aircraft contrail has formed a cirrus cloud that obscures part of the Sun. Both signs of humans' influence on nature. [Canon EOS 350D Ljpg ISO 100 1/4000" 400mm lens @ f/15].

The Glorious Orion Nebula

This was an exercise in using a telescope that doesn't give sharp resolution stars, to generate an extra-sharp picture. The idea came to me at the telescope, while peering at the Orion Nebula. The secret is that it is a mosaic of 15 pictures. Each was a 15-second exposure taken at f/4.8 on the 20" scope during a full moon last year, all except for the central nebula, which was 4 seconds. The Canon Photo Stitch software has never given me an acceptable result, so I spent a few days correcting numerous patches of the background until I decided I'd just make it all an even black. Hence it is not an accurate representation of the sky - no photo ever is. It's still a little grainy in some areas and not a very deep image, but it's so much more aesthetically pleasing to have sharp stars!