Pacman, Bubble and the Tulip – astro-imaging showcase

Society member Keith Elliott has submitted the following images for your viewing pleasure. Here’s his report – you can click on the images for larger versions.

NGC 281, The Pacman Nebula in Cassiopeia

This picture is a composite of 12, 15 minute exposures made through a Hydrogen-alpha filter, so, the otherwise red image, has been desaturated to black and white. It was taken in my back garden in Chelmsford at the beginning of October this year.

Pacman Nebula NGC 281


The nebulous area is about 35 arc minutes across and 10,000 light years distant. It is an area of new (about a million years old) and forming stars, probably in the dark, dust lane, regions of the nebula. The very small open cluster (IC 1590) near the centre contains the smaller group of bright stars that is illuminating this nebula.

NGC 7635, The Bubble Nebula and M52 in Cassiopeia

This picture is a composite of 9, 15 minute exposures taken under the beautiful dark skies of Kelling Heath at this years Autumn Equinox Star Camp.

They are an often photographed pair, ideal for wide field imaging with small, short focal length telescopes.

M52 is the small open cluster of more than 150 stars, of magnitude 8 or fainter, and 13 arc minutes across, in the right half of the picture. It was first recorded by Charles Messier in 1774. The distance is not well known, but is in the ball park of 5,000 light years.


Bubble Nebula NGC 7635


The spectacular Bubble Nebula (NGC 7635), on my astronomical A-list, is an apparent bubble floating in a sea of red gas. It is 3 arc minutes or 6 light years across and 7,000 light years away. The bubble is expanding at the unbelievable speed of 4 million miles per hour! It was formed by the stellar wind from the blue, 8th magnitude, central star blasting into the surrounding denser material. This central star, at some 40 times the mass of our own Sun, is living a predictably short and very violent life.

Sh2-101, The Tulip Nebula in Cygnus

The second Sharpless catalogue (Sh2), published by Stewart Sharpless in 1959 is a catalogue of over 300 large nebulae, many of which are suitable for wide field, narrow band imaging. In other words great for small refractors under light polluted skies.


The Tulip Nebula Sh2-101

This tulip flower shaped nebula, taken in June this year, in Chelmsford, is a composite of 24, 10 minute exposures, taken over two nights, using an H alpha filter. The star that looks over exposed, but is in fact surrounded by nebulous gas, in the top right, is Eta Cygni.

The Tulip is an emission nebula about 20 arc minutes across and 8,000 light years distant.

Just over half way back to the Tulip from eta cygni on the picture, and making an angle of about 45 degrees is a close pair of bright stars. The brighter, 9th magnitude star, has an optically invisible, but strongly x-ray emitting partner, the famous Cygnus X-1. This was the first object discovered that was considered likely to be a Black Hole.

Hardware and Software

  • Modified Canon EOS350D DSLR. The internal infra red filter has been replaced with a sharper cut off filter to extend the red end of its spectral response, particularly to give improved sensitivity to the hydrogen alpha line.
  • Starlight express SXV guide camera in a separate, piggy backed, guiding telescope (70mm f/10).
  • Televue x0.8 focal reducer/field flattener to give a plate scale of 2.2 arc seconds per pixel (1.8 without the reducer).
  • William Optics ZS 105, f/7 apochromatic refractor.
  • Losmandy GM8 mount.
  • MaxIm DL for camera control, guiding input and focusing, via a laptop, and for image calibration and registration.
  • Photoshop CS3 for post processing.


Keith Elliott

October 2008


Posted on 11 October, 2008, in Astronomy News, astrophotography, Popular Science, Society News and tagged , , , , , , , , . Bookmark the permalink. Comments Off on Pacman, Bubble and the Tulip – astro-imaging showcase.

Comments are closed.

%d bloggers like this: