Don't claim to be an expert, but the Summer Triangle would be rising in the spring north in the evening. That way it would be in the zenith around midnight around the start of summer. It would be setting earlier and earlier as autumn passes until it sets with the Sun.
Where I live (latitude +55.60587), the Summer Triangle is glorious all autumn. It's splendid in the western part of the evening sky all of November, for example. On Christmas Day, December 25, Altair is admittedly getting a little low, but I can still see it.
The Summer Triangle is as high as it can get at midnight on August 11.
The reason why the Summer Triangle seems to dominate the western sky for months on end in the autumn is that while the Summer Triangle admittedly sinks lower and lower, darkness is falling earlier and earlier. On Christmas Day, for example, the sun sets at around 3.35 p.m. where I live, and it's pitch dark at 5 p.m. And at 5 p.m., the Summer Triangle is still high and glorious in the western sky.
In January the Summer Triangle is really sinking, and daylight is very slowly returning to our late afternoons. But on January 25 it is still dark at 5 p.m., and Altair of the Summer Triangle is still visible in the western sky. Deneb and Vega never sinks below the horizon at my latitude.
Ann wrote:
The reason why the Summer Triangle seems to dominate the western sky for months on end in the autumn is that while the Summer Triangle admittedly sinks lower and lower, darkness is falling earlier and earlier. On Christmas Day, for example, the sun sets at around 3.35 p.m. where I live, and it's pitch dark at 5 p.m. And at 5 p.m., the Summer Triangle is still high and glorious in the western sky.
In January the Summer Triangle is really sinking, and daylight is very slowly returning to our late afternoons. But on January 25 it is still dark at 5 p.m., and Altair of the Summer Triangle is still visible in the western sky. Deneb and Vega never sinks below the horizon at my latitude.
The Summer Triangle should be visible at sometime of the night (with sun below 18º) for all latitudes north of 42º even in the winter.
Ann wrote:
The reason why the Summer Triangle seems to dominate the western sky for months on end in the autumn is that while the Summer Triangle admittedly sinks lower and lower, darkness is falling earlier and earlier. On Christmas Day, for example, the sun sets at around 3.35 p.m. where I live, and it's pitch dark at 5 p.m. And at 5 p.m., the Summer Triangle is still high and glorious in the western sky.
In January the Summer Triangle is really sinking, and daylight is very slowly returning to our late afternoons. But on January 25 it is still dark at 5 p.m., and Altair of the Summer Triangle is still visible in the western sky. Deneb and Vega never sinks below the horizon at my latitude.
The Summer Triangle should be visible at sometime of the night (with sun below 18º) for all latitudes north of 42º even in the winter.
You've underestimated the latitude range of year-long visibility by about 16°.
The closest the Sun gets to Altair (an thus the most limiting condition for Summer Triangle visibility for northern latitudes) occurs on Jan 21 or 22. For latitude ~26°N, Altair rises when the Sun is ~18° below the horizon, and is further below the horizon for all latitudes north of 26°N. Of course for latitudes <26°N, the Sun gets closer, eventually leading to periods of invisibility during the year.
A pessimist is nothing more than an experienced optimist
neufer wrote:
The Summer Triangle should be visible at sometime of the night (with sun below 18º) for all latitudes north of 42º even in the winter.
You've underestimated the latitude range of year-long visibility by about 16°.
The closest the Sun gets to Altair (an thus the most limiting condition for Summer Triangle visibility for northern latitudes) occurs on Jan 21 or 22. For latitude ~26°N, Altair rises when the Sun is ~18° below the horizon, and is further below the horizon for all latitudes north of 26°N. Of course for latitudes <26°N, the Sun gets closer, eventually leading to periods of invisibility during the year.
I knew I was being conservative but my statement is technically not wrong (for a change).
(I also took the most limiting condition for the Summer Triangle as being four days earlier than Jan 21/22.)
neufer wrote:
I knew I was being conservative but my statement is technically not wrong (for a change).
(I also took the most limiting condition for the Summer Triangle as being four days earlier than Jan 21/22.)
Yeah, I certainly wasn't intending to demean or judge your estimate. I thought you might be interested in a more accurate answer.
Nice job with that, btw.
A pessimist is nothing more than an experienced optimist
The Summer Triangle over the Great Wall
