What to look for when looking above in October
Ah — October! October can be one of the best times to visit the wonders in the night sky. This is because the temperatures are more moderate and because some of the clearest, steadiest skies can often be seen.
The observer with a good southwest horizon can still see Saturn to advantage but soon, just like Jupiter and Venus, Saturn will only be visible at dawn or shortly before when it is still dark enough to have good contrast. It is not so much that Saturn has moved a great deal along its orbit but that we have! Earth has a much shorter path around the Sun than does Saturn so we change our viewing position pretty rapidly and soon it will be visible only before the Sun rises.
The Milky Way is still visible, but again, we are shifting in our orbit so that as winter comes on, we look ‘outward,’ away from the center of our galaxy, toward the faint outer arms of the Milky Way and into intergalactic space. On a clear October night however, look for the Milky Way overhead and them setting in the west as the hour grows late.
In October, and extending into the winter months, our vantage point gives us a chance to see the closest, large, nearby galaxy, designated M31. M31 is roughly 2.5 million light years away and it is one of the bigger spiral galaxies available for easy viewing by amateurs. Even humble binoculars will show it against a dark October sky. It is located near the constellation Pegasus, the flying horse from Greek mythology. All of the stars in Pegasus are relatively close and located in the Milky Way. Of course, M31 has to be located somewhere and it just happens that the stars in Pegasus serve as a convenient guide for finding it. If you want to spot it, you can get on your favorite browser and type in something like ‘find M31 in the night sky’ and there should be some form of star map that you could use. Binoculars are a good instrument to begin with but even a small telescope, say 60mm in aperture, will show it nicely. M31 is a bit bigger than the Milky Way. Our galaxy is about 100,000 light years across; M31 is a bit bigger than 120,000 light years across. [It is a bit difficult to measure exactly the diameter of a large galaxy—they may not have sharp edges or boundaries.] When I use my 10-inch reflector, I can see the extensive arms of this spiral and two smaller dwarf galaxies that are held by the gravity generated by M31.
If one stayed up very late, one could see the next big constellation of amateur interest — Orion the Hunter, again from Greek mythology. [Perhaps if you were a sheep herder, lying on a hillside in 300 B.C. and watching your sheep, you would try to see patterns in the night sky stars. You wouldn’t have much else to do …]
Orion the Hunter is the harbinger of winter. We are not there yet so the Autumn night sky is our night-time feast for the imagination. On a very clear night sky in October, one can try to do what very many humans have tried to do over the ages— count the number of visible stars. This takes real concentration and many people have just nodded off into sleep as they have tried to do this! Theoretically, under a dark country sky, one could count as many as 6,000 stars visible in a single evening. Most people lose count but you can try it if you want! The usual method for counting the stars at night is this: get a bag of very many dry beans and every time you count a star, throw a bean into a box or can. Later, you can count the beans. This may seem like a useless thing do, but somebody did it, otherwise we would not have the number 6,000!
Many wonders can be found in the night sky… I will continue to describe them and point them out to you each month — l never tire of finding these remarkable wonders.