Andrew’s Astronomy Blog

Having bought the book ‘The Caldwell Objects - and how to observe them’ it’s only fitting that I identify this object with it’s Caldwell number rather than the rather nondescript NGC 4755. Located in Crux, The Southern Cross, at a declination of -60 degrees this is a Southern Skies cluster only.

Also known as The Jewel Box this compact cluster is just 10′ in size and could be mistaken for a 4th magnitude star with the naked eye. 5,000 light years away , the stars in it are about 15 million years old.

This image is comprised of 28 3 minute LRGB exposures (12,6,6,4).

There’s been rather a trend on this blog towards pairs recently and to continue this theme here’s an image of NGC 4567 & NGC 4568, sometimes known as the Siamese Twins. This pair of interacting galaxies are part of the Virgo cluster and for some years were considered a line of sight pairing as there’s no visual evidence of interaction.

This image is the result of a stack of 14 five minute frames taken on GRAS-4 over two nights.

This picture was taken with the Canon 75-300 zoom before I bought the Williams Optics refractor. The focal length is 190mm and this image is about one quarter of the original field. Sixteen 3 minute exposures were combined and despite the short exposure time and mis-shapen stars some detail is visible in the galaxies. Also in the frame are two more smaller galaxies, NGC 2976 is on the right and NGC 3077 is at the bottom.

After I noticed the stars were trailing on the images of M51, I rechecked the polar scope picture when I’d re-positioned for the Double Cluster in Perseus. It required a small tweak in azimuth and I then took 10 3 minute exposures at ISO 400 that were combined in Maxim. The trailing was eliminated and although there was some coma apparent in the corners of the image I removed some of this by cropping the picture. Looks like a field flattener will be required.

Whilst spending the weekend with my Dad, we stopped off at Astronomia in Dorking, Surrey. There on the shelf was a Williams Optics 70mm Zenithstar. I’ve been looking for something small and light to replace the Canon zoom lenses on the AstroTrac and this fitted the bill exactly. Having parted with some money, I took it home and contrary to known astronomical principles, the following night was clear!

First target, M51. This being a first attempt I wasn’t too sure what to expect at the longer focal length and the tracking wasn’t perfect so I finished the run with just 5 images of 3 minutes each. With the Canon 350D attached, the 420mm focal length yields 3.14″/pixel.