Chapter 11, Sidereal Time.
1) Calculate the sidereal time on 1st October at 10 pm. using both the methods.
Method 1:- Month Method:
Sidereal Time on 7th of month at 7.0pm LMT = 2 X (no. of Month as per calendar year)
∴ On 7th October at 7.00 pm. LMT = 2 X 10 (October is 10th month in Calendar)
= 20 Hours
∴ On 1st October, 6 days before = 20 Hours - ( 6 days X 4 minutes per day)
∴ = 20 Hours - 24 minutes (at 7.00 pm.)
= 19 Hours 36 Minutes (at 7.00 pm.)
S.T. on 1st October at 10.00 pm. = 19 hrs. 36 Mt + 3Hr 00 mts (Over 7.00 pm.)
= 22 Hours 36 Minutes
Method 2:- Cardinal Day Method:
Sidereal Time on 22nd September at Noon LMT = 12 Hours
∴ Sidereal time on 1st October at 12 noon i.e. 9 days after = 12 + (9 days X 4mt per day)
= 12 Hours + 0hr 36 minutes
∴ Sidereal time on 1st October at 12 noon = 12 Hours 36 Minutes
∴ Sidereal time on 1st October at 10.00 pm. = 12 Hr 36 Mt + 10Hr 00 Mt
= 22 Hour 36 Minutes
2) Calculate the sidereal time on 14th March at 5 pm. using both the methods.
Method 1:- Month Method:
Sidereal Time on 7th of month at 7.0pm LMT = 2 X (no. of Month as per calendar year)
∴ On 7th March at 7.00 pm. LMT = 2 X 03 (March is 3rd month in Calendar)
= 06 Hours
∴ On 14th March, 7 days after = 06 Hours + ( 7 days X 4 minutes per day)
∴ = 06 Hours + 28 minutes (at 7.00 pm.)
= 06 Hours 28 Minutes (at 7.00 pm.)
S.T. on 14th March at 5.00 pm. = 06 Hr 28 Mt - 2Hr 00mts (Less in 7.00 pm.)
= 04 Hours 28 Minutes
Method 2:- Cardinal Day Method:
Sidereal Time on 21st March at Noon LMT = 00 Hours (or we can say 24 hrs.)
∴ Sidereal time on 14th March i.e. 7 days before = 24 - (7 days X 4mt per day)
= 24 Hours - 0hr 28 minutes
∴ Sidereal time on 14th March at 12 noon = 23 Hours 32 Minutes
∴ Sidereal time on 14th March at 5.00 pm. = 23 Hr 28 Mt + 5Hr 00 Mt
= 28 Hour 28 Minutes -24 hrs.
= 04 Hour 28 Minutes
3) Calculate the sidereal time on 29th November at 5.30 pm. using both the methods.
Method 1:- Month Method:
Sidereal Time on 7th of month at 7.0pm LMT = 2 X (no. of Month as per calendar year)
∴ On 7th December at 7.00 pm. LMT = 2 X 12 (December is 12th month in Calendar)
= 24 Hours
∴ On 29th November, 8 days before = 24 Hours - ( 8 days X 4 minutes per day)
∴ = 24 Hours - 32 minutes (at 7.00 pm.)
= 23 Hours 28 Minutes (at 7.00 pm.)
S.T. on 29th November at 5.30 pm. = 23 Hr 28 Mt - 1Hr 30mts (Less in 7.00 pm.)
=21 Hours 58 Minutes
Method 2:- Cardinal Day Method:
Sidereal Time on 22nd December at Noon LMT = 18 Hours
∴ Sidereal time on 29th November at 12 noon i.e. 23 days before = 18 - (23 days X 4mt per day)
= 18 Hours - 1hr 32 minutes
∴ Sidereal time on 29th November at 12 noon = 16 Hours 28 Minutes
∴ Sidereal time on 29th November at 5.30 pm. = 16 Hr 28 Mt + 5Hr 30 Mt
= 21 Hour 58 Minutes
4) Calculate the sidereal time on 17th February at 6.30 pm. using both the methods.
Method 1:- Month Method:
Sidereal Time on 7th of month at 7.0pm LMT = 2 X (no. of Month as per calendar year)
∴ On 7th February at 7.00 pm. LMT = 2 X 2 (February 2nd month in Calendar)
= 4 Hours
∴ On 17th February, 10 days after = 4 Hours + ( 10 days X 4 minutes per day)
∴ = 4 Hours + 0h 40 minutes (at 7.00 pm.)
= 4 Hours 40 Minutes (at 7.00 pm.)
S.T. on 17th February at 6.30 pm. = 4 Hr 40 Mt - 0Hr 30mts (Less in 7.00 pm.)
= 4 Hours 10 Minutes
Method 2:- Cardinal Day Method:
Sidereal Time on 21st January at Noon LMT = 20 Hours
∴ Sidereal time on 17th February at 12 noon i.e. 27 days after = 20h + (27 days X 4mt per day)
= 20 Hours + 1hr 48 minutes
∴ Sidereal time on 17th February at 12 noon = 21 Hours 48 Minutes
∴ Sidereal time on 17th February at 6.30 pm. = 21 Hr 48 Mt + 6Hr 30 Mt
= 28 Hour 18 Minutes (Above 24hrs. -24h)
= 04 Hour 18 Minutes
