While we’ve been at home for the Great Distancing, I have been experimenting with what I can see from my suburban driveway.
I know that I can’t see the Milky Way from my driveway. A long time ago, when I went to a star party in a rural area, I learned that Messier objects that are easily seen with my telescope with dark skies couldn’t be seen from my driveway. But I can see the bright planets and the major constellations from my driveway.
I’ve been trying to figure out the limit on what I can see by going out with a sky map on my phone (I’m using GoSkyWatch), and looking at constellations and trying to find the dimmest star I can see. With a quarter-full moon not in my field of view, I can see stars as dim as magnitude 3.5. With no moon, I can see stars as dim as magnitude 4.
My next steps are to figure out the dimmest object I can see with the finder scope on my telescope, with the telescope itself, and with my camera.
What’s the dimmest star you can see in your skies?
Friday was another day when, because we didn’t get the predicted rain, I was able to enjoy some astrophotography: in this case, a conjunction of Venus and Mercury. (A conjunction is when two objects appear near each other in the sky.) Note that, even in the picture, you can see that Venus is a crescent. Like the Moon, Venus has phases, depending upon how much of its sunlit side we can see. In fact, it is even more of a crescent than it looks in the picture – only about 5.3% illuminated – as you can see in this neat animation. If you zoom in, you can see that Mercury is also not a circle – it is 67% illuminated. The two are different because they’re in different parts of their orbits relative to the Earth. Venus is close to passing between the Earth and the Sun, so we see very little of its sunlit side. The lines between Mercury and the Sun and the Earth and the Sun are almost perpendicular, so we see a much larger percentage of its sunlit side.
I have rarely seen Mercury, so this was a real treat. It’ll be visible for a few more weeks in the evening sky, so if the clouds stay away, I’ll have another look.
Camera Geek Info
- Canon EOS 60D in manual mode set at f/5.6, 1/30 second exposure, ISO 800
- Canon EF 70-300mm f/4-5.6L IS USM lens, set at 300 mm, manual focus