So, what do you look at when the sky is clear but there is a huge full moon beaming down from above? There was a time when I abandoned all thoughts of deep sky observing until the moon was past - by which time it would always be cloudy again. Visually, I think this is still the case because the eye is just unable to dark-adapt to the high levels of background light. But a ccd camera doesn't have an iris, at least mine doesn't, so all the camera sees is a vast increase in sky background values. By increasing the exposure time and compensating for the high background (it seems to throw the camera bias way off but this can be experimentally subtracted out) we can still use this observing 'dead time' to our advantage - if we choose the right subjects.

We know the planets are virtually unaffected by moon glow because they are so bright. On the other hand galaxies are not a good bet because they tend to be very faint and have very low surface brightness's at the best of times. Imaging galaxies with a big moon in the sky results in washed out, colourless and generally low-contrast images. A no-go really. Similarly, bright nebulae are not really that bright and you really need dark skies to do these beautiful objects justice. Star clusters, both open and globular varieties are, however, a really good bet and some very nice images can be captured under full moon conditions.

Last week, it was really clear, cold and dry - a most unusual combination of conditions here in Weymouth - but the moon was quite bright. I decided to do some imaging anyway and chose a subject that would hopefully give me a good result through the moon light. I decided to have a look at some planetary nebulae, which usually exhibit very strong colour saturation on my MX5C camera.

I chose ngc 40, ngc 1501 and ic 289, 3 planetaries nice and high in the sky and hopefully all showing different emission characteristics.

Here is ngc 1501 which is a magnitude 11.5 object in Cam. It's surface brightness is high, 10.9 mags per square arc min. and it is reasonably big for a planetary, 56" x 48". My image consists of 40 x 60 second exposures summed and processed in AstroArt3. 3 cycles of Maximum Entropy deconvolution were performed on the luminance frame. The effects of the nearly full moon can be seen as an increase in the background colour noise levels. Gradient removal and Gaussian blurring were performed on each RGB colour frame in turn. The RGB frames were then re-combined and finally an LRGB synthesis was performed to achieve the final result.