Summer Triangle low in morning

Event Date: August 5th
Time: 5:30 AM


Brief
 
   The Summer Triangle dominated the sky all night long during July, albeit only dark enough to see it easily for about 11 hours at our latitude; some of that being during nautical twilight time.  Now that the sky is staying darker longer, and the Triangle is setting about four minutes later each morning, Vega and Altair become a little tougher to see through atmospheric pollution during morning twilight.  Deneb is still far enough north and east to see for awhile longer.
After showing the Triangle transiting a few times this season, I will show it low in the west-northwest this morning, seen below.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   As the Sun starts setting about a minute later each day starting late this month, Altair will be seen setting before Vega, being a little less than 30º closer to the celestial equator.  Vega is far enough north that it gradually sinks towards the horizon.  I have shown this before when placing the celestial grid in, and you can remind yourself of that HERE (include link).  Deneb is a little further north than Vega and east enough of it that as seen from our latitude, it sets about three hours after Vega.  Watch these two stars as they reach atmospheric pollution: Vega refracts enough light that it gives off a "rainbow-y" appearance, while dimmer Deneb has a green hue to it.  Other stars that resemble Vega are those a little brighter or just about as bright: Sirius is one of them, although we have to wait a few weeks until we see it rise further from our star's glare.  I will talk more on Sirius tomorrow looking east-southeast.