Monday 5 March 2018

Venus and Mercury - Part II: Sunday March 5, 2018

The secret to taking photos of stars and planets in the twilight is to choose a long focal length, a large F/ratio and not be afraid of a fast shutter speed - like 1/125sec. The sky is bright, surface brightness is high - so anything that primarily reduces surface brightness will increase the contrast between point-like sources, planets and stars, and the background sky. Be brave and try: every camera lens has its own story.

So Vicki and I returned Sunday evening just in time to catch the sunset:

And then we were surprised - we don't read the script!

Mercury is so much closer to us than Venus is, that Mercury's apparent motion is dominant for now:
(Mercury is 1.187 AU away vs Venus' 1.655AU where 1 AU is the nominal distance of the Earth from the sun, but really 0.992AU on Sunday since the Earth was at perihelion on Jan4)  Maybe the following graphics will help. Recall that planets move counterclockwise around the Sun.)

I credit John Walker for the model of the inner solar system.
We are looking forward to March 18 when the crescent Moon will be back in the picture.



  1. Very informative. Excellent photography. And your enthusiasm is contagious. Thanks so much for these last two postings.