A summary of December’s main meeting

Chris Hooker of Newbury AS has graced us before, and this time his offering was ‘Solar System imaging with a webcam’.

Ironically he immediately set about explaining that astro images are no longer made with basic webcams as a whole.  They were designed for surveillance originally.   Nowadays you can get proper ones designed specifically for planets.  (exx. Celestron, Meade, Orion Optics) The top end ones can cost up to £800.

They may not necessarily have more pixels but will be less noisy. Chris gave us plenty of advice on getting the best out of a webcam. The important thing is to be able to stack images and use processing software like Registax.  This is quite old but still does most things and is free.  The more images you can stack the better.  It also means you can make observations even if seeing is not great.  In the Antoniadi scale of seeing where 1 is excellent and 5 is rubbish even 4 can give you glimpses of good seeing, so you can select the good images.

For planetary imaging it is always best to use a long focal length.  He uses an 8” telescope with a Barlow at x2 or x3, and set at f/30 he can take 1/80th of second shots at 60 frames a second.Don’t get the polar alignment too spot on because if the camera’s CCD has a few duff pixels they won’t be in the same place on each image. He also tells us not to worry too much about getting the focus spot on: scan through the range where it comes into focus and goes out again then put it somewhere in the middle of that acceptable range. The focus is likely to change a bit anyway, as the scope’s tube shrinks as it gets colder during the session.

He does not recommend colour cameras as they are a black and white matrix with a colour matrix overlay, so the resolution will be far better with a black and white camera and superimposing images taken through red, green, and blue filters. Chris finished off with some of his specials.

He likes the Aristarchus area on the Moon because there are so many different features in a small area.  The Sun is best in monochrome and Venus’ clouds are best through a UV filter.  He has even managed some good shots of the International Space Station.

If you want more advice on using webcams, we have quite a few experts in the society and the Committee can point them out to you.

Gwyneth Hueter.

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