GENERAL ASTRONOMY ARTICLES

THE CONSTELLATIONS : Part 3
CULMINATION TIMES

CULMINATION of the CONSTELLATIONS

A culmination occurs when some star or constellation crosses the local meridian to reaching its highest (or lowest point) in the sky, and knowing when this occurs is very useful to both visual or telescopic observations of the night sky. By knowing when some celestial object crosses the local meridian, means that their general appearance will be at their very best, and without the hindrance of the atmospheric effects; such as seeing, refraction or air mass.

Culminations for non-circumpolar stars, that do rise and set below the horizon, will happen once per day. However, because of Earth’s orbital motion around the Sun, the time for each successive culmination falls earlier by about four minutes for every day that passes. Its exact instant of local time crossing the local meridian is formally called the Sidereal Time, which is exactly corresponds to the local meridian’s Right Ascension. In other circumstances, if some constellation or celestial object appears circumpolar — never setting below the local horizon — two culminations can occur. These are an upper culmination (highest) and lower culmination (lowest).

Calculation of culmination times is no exactly simple, as the width of the constellation means that we need to determine the time of the mid-point. This can be approximated by the difference between the eastern and western constellations limits, but this should probably be better determined but knowing the right ascension of half area of the constellation — something far more difficult to calculate. A slightly more accurate way it the constellation centre of both right ascension and declination, and this requires knowing the extrema of all the boundaries.

Furthermore, culmination times are also dependant on the precession of the equinoxes, so they should include the current epoch. Many tabulated culminations are still based on the B1950.0 epoch, meaning the culmination times are only out be a day or so. Most tables on culminations are only accurate to several days, but this is still quite adequate for most visual observation purposes.

The TABULATED DATA

Table 1 shows the dates when this occurs are conveniently expressed for midnight (12pm) and in the early evening at 9pm, when most observers would be looking at the nighttime sky. Sometimes it can be given at 6pm, but the only is useful in the winter months when it is dark at that time. Finding culmination times for other times of the year, subtract 15 days for ever hour that is earlier than this date. For times that are later; add fifteen (15) days for every hour. If the date is different than specified, then add or subtract twenty-eight (28) minutes for each week that has elapsed or is to come.

This page shows three main tables. These are the culmination times of the constellations and for the bright stars at either midnight (12pm) and the evening (9pm.) Culminations are listed below as;

Table 1. The Constellations (By Date)

Table 2. The Constellations (By Name)

Table 3. Bright Stars, plus Large and Small Magellanic Clouds.

COMMENTS

An average difference between dates in the tables below, is 45.66 or 45½ days. It is possible to calculate for other specific times. I.e. Finding for 12pm, by adding 45½ to the 9pm tabulated date, or even finding 3pm, by adding 91 days to the 9pm tabulated date.

Traditionally, all culminations at a fixed date are given in some form of tabulated list, but a planisphere can also easily provide this same information.

Observers are mostly interested in the dates corresponding to their upper culmination, which are the dates in the Tables below. If the lower culmination is required to be known, the difference in dates is exactly earlier or later by six months.)

NOTES : Table 1 lists Eighty-Nine (89) constellations culminations, where divided Serpens, lies on either side of Ophiuchus. These constellations are termed Serpens Cauda and Serpens Caput, whose culminations are about ten days apart.

NOTES : Table 2 lists Eighty-Nine (89) constellations culminations, where divided Serpens, lies on either side of Ophiuchus. These constellations are named individually as Serpens Cauda and Serpens Caput, whose culminations are only about ten days apart.

Bright Star Culminations

Last Update : 17th June 2015

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