When is the next 13.00 Local Sidereal Time for a UK observer?

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Discussion Overview

The discussion centers on determining the next occurrence of "13.00 Local Sidereal Time" for a UK observer, including calculations and implications for celestial observations. Participants explore the relationship between local sidereal time and the position of celestial objects, as well as the significance of stars and the center of the galaxy at that time.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests calculating the next 13.00 LST by determining when the Sun's right ascension reaches 13h00m, noting that local noon may vary based on timezone.
  • Another participant inquires about which star is directly overhead at 13.00 LST for a UK observer, questioning whether the center of the galaxy is above or below the observer.
  • A participant provides information from a sidereal time calculator, indicating that the star "Phecda" and the galaxy "M109" are nearly overhead at the calculated time, while the center of the Milky Way is positioned southeast and below the horizon.
  • Further questions arise regarding named stars near the nadir and the significance of celestial objects for observers located at different latitudes, including the equator and the north pole.
  • One participant asks about the location of the center of the galaxy cluster to which the Milky Way belongs in the sky.

Areas of Agreement / Disagreement

Participants express varying viewpoints on the celestial objects' positions at 13.00 LST, with no consensus on the significance of stars near the nadir or zenith for observers at different latitudes.

Contextual Notes

The discussion includes assumptions about local noon and its variability based on geographical location, as well as the dependence on specific celestial coordinates that may not be universally applicable.

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When is the next "13.00 Local Sidereal Time" for a UK observer?

Anyone with software or equations to work that out?
 
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You can work it out yourself fairly easily. When the Sun passes through your local meridian (i.e. - noon), your local sidereal time is whatever right ascension the Sun is at. Right now, the Sun is at ~2h54m. To get to 13h00m, you therefore need to wait 13:00-2:54=10:06. That would mean that 13h00m passes overhead at 12:00pm + 10:06 = 10:06pm.

Though that presumes that your local noon, when the Sun is in the middle of the sky, is in fact 12:00pm! Depending on where you are in the timezone this may be incorrect, and you would have to add (or subtract) whatever is the difference.
 
Thanks.

What star is directly above an observer at 13.00 LST? (Observer at Britain's latitude and longitude).

Is the centre of the galaxy directly above?

Is the centre of the galaxy in the opposite direction perhaps? (Directly below the feet of the observer).

Is there some important star directly above (or directly below)?
 
A google for "sidereal time calculator" yields lots of hits. Here's the first: http://tycho.usno.navy.mil/sidereal.html

According to Starry Night, the star "Phecda" and the galaxy "M109" are almost directly overhead at that time (given in the previous post) and the Milky Way is tilted roughly 30 degrees from the horizon from north to south (imagine a hula hoop around your waist, tilted up 30 degrees). The center of the Mikly Way is to the southeast, 20 degrees below the horizon. There is no named star within 10 degrees of the nadir.
 
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That's impressive. Thanks Russ.

Any named star within 1 hour (+/-15 degrees) from the nadir?

What if the observer is north or south of the UK, all the way to the equator or the north pole? Anything significant near the nadir or zenith for this observer?
 
Do we know where the centre of the cluster that our galaxy belongs to, resides on the sky?
 

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