# Standard and solar time

TyErd

## Homework Statement

Given:

Consider the following: city: Córdoba, Argentina
Longitude = 64 deg 10 min W
Latitude = 31 deg 28 min S
Time zone = GMT -3
Date = 01 August
On this date, the equation of time = -6 minutes. Assume no daylight saving time

(a) Determine the standard time at solar noon.
(b) Determine the hour angle at 8 AM standard time.

## Homework Equations

earth rotates 15degrees per hour

## The Attempt at a Solution

15(3) = 45
64.1667 - 45 = 19.1667degrees.
if Earth rotates at 15Degrees per hour then that means for 19.1667degrees it needs to rotate about 1hour 17minutes.

thus standard time at solar noon is 12.00 - 1hour and 17 minutes + 6minutes
= 11.49am

is that right so far?

using above answer, for part b i did the following:

from 8am to 11.49am there is 3hours 49 min difference.

(3 + 49/60) * 15 = 57.25degrees.

is that right?

Last edited:

## Answers and Replies

JohnRC
In your attempt at a solution in the first part, your method is fine, but there is a very simple arithmetic slip in your working.

Your calculation for the second part seems fairly right, except that the mistake in the first part has carried through. Do you know the sign convention for hour angle? Remember that the sun travels anti-clockwise around the sky in the Southern hemisphere. Does that make a difference? Or does the fact that it still travels from East to West make a calculation the same as in the Northern hemisphere? You do need to think carefully about that aspect before you hand your work in.

TyErd
No I'm not familiar with the sign convention.

for the first part should it be 12.00 + 1hour and 17 minutes + 6minutes= 1.23pm??

JohnRC
check the sign convention by google hour angle

for the first part no, that is not the slip -- you have said that standard time is an hour and a bit before noon -- does that match the time you have arrived at?

TyErd
Im not sure what you mean by what time I arrived at.

JohnRC
is 11.49 an hour and a bit before noon?