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Finding the Planet Mercury in Daylight Skies

Ernie Piini

The author with his telescope that he built back in 1970. Photo courtesy of Ernie Piini.
Mercury as seen in daylight. Photo courtesy of Ernie Piini.


Currently 76 years of age, with eyesight not as good as years ago, seeing the planet Mercury with the unaided eye even in the evening sky had become not viable for me. That's why I enjoy looking at Venus which is three or more magnitudes brighter.

Then I read an article in the June issue of Astronomy magazine pertaining to the June 27, 2005 conjunction of the planets Venus and Mercury. The event took place around 9:00 a.m. on a Monday when the planets were separated by about 4.8 arc-minutes (Moon diameter approximately 30 arc-minutes). Encouraged, the possibility of seeing Mercury during the daytime gave me an idea and a challenge. I have seen Venus and Jupiter many times during daylight hours but never Mercury. I thought if I can easily find the planet Venus I should be able to see or photograph Mercury along side during this conjunction.

I brought out my 8-inch Newtonian telescope, home built in 1970, and mounted a Canon "Rebel" digital camera at the prime focus. The "Rebel" SLR camera can be attached to any telescope with a readily available T-Mount. It is also ideal in that the ISO film speed can be quickly changed. Each digital photo registers the date and time to within a second, records the exposure used, provides a photo ident number, and each photo is instantly reviewable as a thumbnail view. Unwanted photos are easily deleted to make room for more exposures.

To begin, I pointed my telescope at the sun, the input protected with a Baader Density-5 solar filter. I then set my setting circles to the sun's current Right Ascension (RA) and Declination positions. The telescope is then repositioned to Venus' RA and Dec settings (removing the solar filter in between). Finding Venus was fast but I could not see Mercury in my 1.25 x 0.82 degree field-of-view. I photographed Venus anyway and down loaded my results to my eMac computer. With the use of my iPhoto software, which has a tremendous enhancement capability, I found that my photo included the planet Mercury too!



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