Paul Dodd's Horsehead

Paul is one of my oldest friends. I was at school with him back in the 1970s. Paul is the lean-in type who has never done anything in a half measure, and is now an accomplished wildlife photographer.

Like me, Paul has an interest in astronomy, and has always been fascinated with the idea of photographing the Horsehead Nebula.

In order to do this, he got himself a telescope. Showing that lean-in personality again, it's a Celestron 1100 EdgeHD Scmidt-Cassegrain, mounted on a CGEM-II equatorial mount. This is a big scope, and big scopes have complications, as we found.

The camera he used is a Nikon D810a, which is specifically for astrophotography, having the built-in IR filter modified to allow longer wavelengths to the sensor. This is important for the Horsehead as it's in a region rich in hydrogen, which emits light at this wavelength.

Last week, I went with Paul and his wife Ruth (also a photographer) to the ASV's dark sky site. This was the scope's first light.

The procedure with a big mount and a long scope is the same as for other equatorials. It's just that everything is harder.

We set the rig up during the day, aligning it as close as we could to the celestial pole. We also aligned the finderscope to a distant tree.

In the evening we did a 2-star alignment and added two calibration stars. But the test exposures were terrible. Poor polar alignment was compounded by the long focal length of the Edge 11. Frustrated, we had to align better.

Polar aligning a Celestron is not a straightforward procedure, and the huge focal length complicated matters. The mount slews off a guide star and you re-centre using the adjustment bolts, but even a small slew pushed the guide star right out of view. We muddled through with the finderscope.

After this, Paul went to the Horsehead, and found he was able to get round stars in a ten second exposure. The 327 subexposures were dark - so dark that he wasn't confident he'd get anything.

But this is what he got.

Barnard 33 - the beautiful Horsehead Nebula.

I think Paul's hooked.