Question

You are at 94° west longitude in the Mountain Time zone of the United States. The date is July 14, and daylight savings time is in effect. If your watch reads 13:55:23 hours, what is the corresponding local solar time? 

Answer 1

Concept required - Local solar time is the time set as per the position of sun in the sky .

It is calculated by the formula -

where LSt - local sun time

LT -local time

4 - minutes taken by earth to rotate 1 deg

Lsite - longitude of site

LSTM - local standard time meridian

Eot - Equation for time

One thing to be noted is that latitudes left to reference latitude (GMT , say) is -ve , and to right is +ve

Step by step solution -

Lsite = 94 deg W= -94  

LSTM = 105 deg W = -105

From the equation of time graph - EoT = 5 m 52s = 0:05:52 ( from the EoT table 2019)

LT = 13:55:23 hours

So putting the values in our formula -

Now 430 min 8 sec is- 7 hours 10 min 8 sec

So we have :

LST = 13-7 : 55-10 : 23-8 (subtracting corresponding units of time )

LST = 6:45:15  

Thus Local solar time is 6 hour 45 min 15 sec