Farnham Astronomical Society » Eric Grieve

National Astronomy Day at the Alexander Telescope

Danny Thomas — Sun, 25 Apr 2010 21:25:11 +0000

Members of Farnham Astronomical Society marked National Astronomy Day (on 24 April 2010) at Aldershot Observatory with the Patrick Alexander telescope.

Society member Eric Grieve opened up the dome to the afternoon sunshine and talked through the operation of the telescope with members and their guests.

The telescope was positioned to project the Sun safely onto a sheet of cupboard.

Considering the age of the optics, the image of the Sun was relatively clear but there were no sun spots to enjoy!

Despite the fact that the telescope is over 100 years old, the clockwork drive was still able to track the movement of the Sun across the afternoon sky.

Thanks to Adam Thomas for taking the photographs.

Solar Disk Imaged by Eric Grieve

pcburns — Mon, 03 Aug 2009 16:51:33 +0000

A sunspot is an area on the Sun’s surface (its photosphere) that appears dark because they are cooler than the surrounding area – approximately 4,000–4,500 K compared with the 5,800 K of the surrounding material at about 5,800 K . They are visible as a dark spot because the intensity is a function of temperature to the 4th power (Stefan–Boltzmann law). Sunspots are caused by intense magnetic activity which inhibits convection, forming areas of reduced surface temperature.

Image taken on 01 July 2005

Sun Dog and Circumzenithal Arc Photographed by Eric Grieve

pcburns — Mon, 03 Aug 2009 16:35:13 +0000

A sun dog or sundog is a type of ice halo. It is a colored patch of light to the left or right of the sun. The circumzenithal arc is similar in appearance to a rainbow. It is caused by refraction of sunlight through horizontally-oriented ice crystals.