Observing Log for 2005-10-19

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Location: Billingborough (South Lincolnshire, UK)
From: 2005-10-19 21:40 UT
To: 2005-10-19 22:11 UT
Equipment: Cheap Telescope
Temperature: 7.9C
Humidity: 89%

A fair bit of cloud about with the sky washed out by a waning gibbous Moon (around 96% illumination). This wasn't really a problem as the purpose of this little session was to see how well a little telescope would perform against the Moon.

Test of telescope against the Moon

From: 2005-10-19 21:40 UT
To: 2005-10-19 22:11 UT

Doing another test of a rubbish little telescope that I first tested back in July this year. The 'scope has been sat doing nothing for quite some time and, having recently purchased a sheet of Baader solar filter, I've been thinking about making a filter for it and using it as a cheap little solar telescope.

I mounted the 'scope on a photographic tripod, lined it up on the Moon and worked through each of the lenses. With the 17.5mm, 12mm and 9mm the Moon easily fitted in the field of view (obviously increasing in size with each lens). In all three cases the image appeared to be sharp with no fringing or false colour.

Next I tried each lens with the 3x barlow that came with the 'scope. In this case there did appear to be fringing and false colour in the image and the focus never seemed to be very sharp. The 17.5mm plus barlow combination gave an image of the Moon that was still fully visible, the 12mm gave an image that more or less filled the field of view and the 9mm gave an image that exceeded the field of view.

Given that a filter for this 'scope wouldn't use up much of the Baader sheet (the objective is just 50mm in diameter) I think I'll have a go at making one and seeing how it performs. Even if the images aren't that good with the barlow in place the size of the images without it are acceptable. It might work out to be a handy tool to have alongside the Solarscope when doing some solar observing.

Page last modified: 2013-04-09 09:19:19 UT
Dave Pearson <davep@davep.org>
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