I decided that I wanted to try a Bahtinov mask for focus tests on the 3 inch refractor, after having tried one on a telephoto lens with some success. The Moon was about so I thought it could be a good test. This image is what I managed purely by using live view to focus. The live view was monitored on a tablet, by using the HDMI output from the camera, and a video capture dongle. Continue reading →

Yesterday’s image of M44 Praesepe, or the “Beehive” cluster. This was taken using my old 135mm Pentax fitting lens, with a mild Barlow in the Pentax to Nikon adapter. I use it because it’s faster than my other lenses; f/2.8 as opposed to f/5.6 on a telephoto set at 200mm, or f/4.5 on a zoom set at 70mm. The image quality is not as good as that from the Nikon zoom set at 200mm, but exposure times are much shorter. I need to be patient!

The image is from a total exposure of 240s, and (at last!) with a flat field applied. I took a set of twilight sky flats for all my lenses, so that I can do more experiments.