Partial Eclipse of the Sun October 12th, 1996

Solar Telescope

The partial eclipse was observed using an old brass 4" refractor and Herschel wedge solar / star diagonal loaned to me by the Manchester Astronomical Society. The instrument has been adapted specifically to undertake solar photography. The brilliant reflection from the front surface of the Herschel prism, even at 3% reflectivity, was attenuated by the incorporation of a polarising filter and a neutral density ND 2.0 filter placed about 1" inside prime focus of the telescope.

The refractor is, perhaps, late nineteenth century, made by James Parkes and Son of Birmingham, England. The history of the instrument is not known but it was given to the MAS about 10 years ago. The original eyepiece threads were very finely cut and these were recently re-cut to accept standard 1.25" RAS threaded eyepieces and accessories. Presumably the telescope predates the introduction of RAS threaded eyepieces in the UK.

The telescope is mounted on a spar-type equatorial mount made by the late Mr John Rustige, an MAS member and very active contributor to the Solar Section of the British Astronomical Association. John was a retired engineer and built his equipment to be functional rather than aesthetic. Used with the solar diagonal, the mounting allows comfortable, seated observations to be made. The picture shows the set-up. The mounting is designed to be very robust but to allow declination movement only within the limits needed to observe the Sun from Manchester (53.5 N). It could also be used for lunar observations.

Partial Eclipse

Crater Profile

I had hoped that the optical set-up would allow sunspot photos but as it turned out there were no surface details visible that day. Clouds did interfere but I got about twenty slides, at about 5 minute intervals, taken on Kodachrome 200, with between 1/500 and 1/60 sec. These were automatic exposures with my Pentax ME Super camera body. I have photographed several partial and two total solar eclipses with telephoto lenses on a similar set-up so most of my pictures were rather routine. However, as the moon's disk encroached onto the sun, a large crater was clearly seen in profile. This was observed directly through the telescope as well as photographically. The seeing was not good but one image was reasonably steady, as can be seen from the smooth solar limb, and this shows the crater profile quite well. Even a central peak is visible. Please look at the pictures.

Crater Profile

To be seen in such profile, the crater has to be near the Moon's south pole. It is also big, perhaps 150-200 miles in diameter. Can anyone identify it for me ? What is the big plateau to its left ?

I am quite pleased with my first attempts at solar photography through a reasonably-sized telescope but I will be modifying the system to replace the polarising filter with a second ND filter to minimise image degradation. Otherwise I can then take pictures of sunspots, seeing permitting.

Kevin J Kilburn

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