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70 Falmouth Street Portland, Maine 04103
43.6667° N 70.2667° W
Founded January 1970
Julian date: 2457674.16
"A nurse walks into a doctor's office and says, "Doctor, the Invisible Man is sitting out in the waiting room. The Doctor replies, 'Tell him I can't see him.'"
From "Plato and a Platypus Walk Into a Bar"
THE DAILY ASTRONOMER
Tuesday, October 11, 2016
Tip Queries
Yesterday's posting about night sky watching tips generated a lot of response from subscribers asking questions about those tips. We posted that tip list yesterday in conjunction with an announcement about yesterday's "Astromomy Cafe." So today's DA addresses some of the questions we received about this list. Alas, we cannot count these as pandora questions because we haven't even bothered to inscribe them on parchment paper and stuff them into the vessel. Instead, we'll address them all at once.
"You told us to use red light to read a star chart. Does it have to be red?"
-M.P.
One should use monochromatic light to read star charts so as not to diminish dark sky adaptation. "Monochromatic" means light of a single wavelength. (A red gel will not produce purely monochromatic light, as a laser would, However, its close) We strongly recommend red because that color hardly diminishes dark adaptation at all. Using another color, such as blue or green, won't be as effective. And, no, to be honest, I don't know why red affects this adaptation less than other colors.
"Is it true that colder nights are better for star gazing?"
-S.B.
It can be. First, the winter night sky is adorned with an abundance of bright stars, such as those within the Winter Hexagon. Secondly, star watching is often easier in the winter because there is less radiational cooling, so the atmosphere is less turbulent. In the summer when the temperatures are humane, the ground is warmed by the benevolent Sun throughout the day. At night, some of that residual heat radiates away, disturbing the atmosphere. Winter is colder and so the ground isn't radiating as much heat at night and the atmosphere is less turbulent.
The Winter Hexagon. Many sky watchers prefer the winter night sky because it contains bright stars, such as those comprising the "Winter Hexagon," as seen above in this image by NASA. Secondly, night time radiational cooling is at a minimum in the winter, so the atmosphere experiences less turbulence
"Will we see better if we're on top of a hill or a mountain?"
-L.P.
The higher your altitude, the thinner the air. Remember that at sea level, the atmosphere will obscure a lot of incoming celestial light. (It sort of makes up for this by sustaining life on Earth.) If you're observing the sky from a mountain summit, you will enjoy magnificent views that one won't generally see at a lower altitude. However, this effect is negligible if you're on a hill that is only a few hundred feet above sea level. Trek up a mountain that is at least a mile high to truly start to notice a difference.
"If we're using a telescope, should we let it sit outside for awhile before viewing?"
-R.G.
Absolutely! It is best to have a telescope at thermal equilibrium with its surroundings to avoid the same air turbulence you would have in the summer. If you're viewing objects in the winter, you don't want to be using a telescope that is at room temperature. The telescope will cool as you're using it, producing air ripples that will render viewing more difficult.
"Do you happen to know what sky watching apps are good for the phone?"
-C.C.
Disclaimer: I am afraid I do not have a smart phone, let alone any app for one. I have heard good things about the Night Sky 4 and Stellarium. There are undoubtedly others of comparable quality, but I am only basing this answer on hearsay.