What is Vega's maximum altitude in the sky as observed from?

Question

What is Vega's maximum altitude in the sky as observed from the Scottish Highlands (latitude 57°N, longitude 4° W)?
(Vega's right ascension is 18.5° and its declination is +39° )

Will Vega ever disappear from the sky and, if not, what will its minimum altitude be?

this is the question and it can be answered with the information provided

Answer 1

From any location at latitude L in northern hemisphere:

Looking at the southern horizon, the celestial equator crosses the meridian at altitude 90-L.

Declinations are measured from the celestial equator.

Therefore, altitude of a star above southern horizon = (90-L)+DEC.

If this angle is greater than 90 degrees, then the star's azimuth is north instead of south (however, mathematically, it is OK to say that the altitude is 110 degrees above the southern horizon).

In your problem:
L = 57
D = 39

Altitude at upper transit (measured above south horizon):

Alt = (90-57)+39 = 72 degrees.

For a fixed star, upper transit (a.k.a. meridian passage) is the highest altitude that a star can reach in your local sky.
----

Will the star set?


The altitude of the celestial pole (DEC=90) over the northern horizon, is the same as the latitude. At lower transit, the body is (90-D) degrees below the celestial pole. Therefore, altitude is L - (90-D)

For Vega in the Highlands, at lower transit:
Alt = 57 - (90-39) = 57 -90 +39 = +6

By definition, lower transit is the minimum altitude that the star can reach. Since Vega is still 6 degrees above the horizon at lower transit, then it does not set (it's altitude never decreases to zero).

However, in the highlands, you may be located where there are mountains blocking your northern horizon, higher than 6 degrees above the theoretical horizon (defined as 90 degrees from the zenith). So, depending on your exact location, it is possible that Vega "sets" behind a mountain.

Answer 2

At latitude 57° N, the equator is never more than 33° degrees up, so an object at declination +39° would culminate at an altitude of 72°.

(90-57) + 39 = 72

Answer 3

I set Sky Map Pro to 57N latitude.

Just to review, the farther N you go, the more objects become circumpolar. If you are on the N pole every star you can see is circumpolar. Circumpolar means they never rise nor set. These calculations are based on the assumption of the Earth as a perfectly flat sphere. It may be you have a tree line or a mountain range that will cause a circumpolar star to disappear from view, but formally, it is still circumpolar. At the equator, no star is circumpolar.

And the answer is: at 57 N latitude Vega achieves a maximum altitude of +71 degrees 47 minutes 45 seconds of arc, and minimum altitude of +5 degrees 56 minutes 13 seconds of arc.

Lyra culminates in early July, which means that is the time the constellation crosses the meridian at midnight. Vega culminates on the 1st of July (night of 30 June - 1 July) from the Greenwich meridian which isn't far from you. It will always be at its highest crossing of the meridian at *night*. By day, it will cross the meridian again, and be at its lowest point.

hope that helps,

GN

Answer 4

Do you ever do any research just for the fun of it?

If you did, you would know that the Earth's axis wobbles ever so slowly, and in about 25,000 years it will have wobbled its way around to where Vega is our "north star", not Polaris.

I really don't know the point of your question. You have the angles and I presume you have the base time at which the angles occur. These are the means for your answers.

Essentially, if Vega is viewed at the same ascension as Polaris (using the proper time of night and time of year), then it's declination is added or subtracted to get the max and min values with respect to the present northern horizon.

Answer 5

only on thursdays, otherwise icecream doesnt have wheels; therefore, you can not paddle a rollercoaster through a cubicle wall