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I asked Frank about the details of his observation of an inferior
conjunction of Venus, with a telescope.

He replied-
> A fairly ordinary six-inch reflecting telescope  with magnification around
> 75x on an equatorial mount with basic RA/Dec setting  circles. The trick
> is to
> look for Venus, in daylight around high noon. You aim  the telescope at
> the
> Sun, projecting the Sun's image, not looking directly. Then  adjust for
> the
> setting circles to match the Sun's position, and offset from  there to
> Venus. As
> long as the sky is very clear, Venus is visible immediately.

I hope Frank will back me in warning sky viewers about the dangers of
peering so near to the Sun. Not, that is, unless they have such an
instrument, which can be preset in such a way that it can't be accidentally
pointed into the Sun. Ideally, it should have the ability to be locked to an
automatic motor-drive, as I imagine was the case with the instrument that
Frank used. If a tripod stand is used, there's always the danger of knocking
it. In no circumstances should a hand-held telescope, such as that of a
sextant, be pointed anywhere near so close to the Sun, without its dark
Sun-shade. The risks are too great.

As we have discussed before, the telescope doesn't make a Sun image
intrinsically brighter; only bigger, on the retina. Nevertheless, the
brightness of any Sun image on the retina is enough to quickly cause
irreverseable damage. Be warned!

George.

contact George Huxtable at george@huxtable.u-net.com
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

   

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