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By K S Chadha, Jun 18 2016 06:27AM

When the Orion’s Sword in Vertical or Near Vertical as shown in first image, then the Orion’s Sword points to the spot in the horizon that is close to due South.

Important Points:-

1) It is less dependable when the Orion’s Sword is well off-vertical. (See Image 2)

2) It is less dependable when the Constellation of Orion is lower in the sky.

By K S Chadha, Jun 17 2016 05:18AM

The constellation, Orion, rises in the east and sets in the west. Orion’s belt, the only three bright stars (as marked in the image) that form a short straight line in the whole night sky rise very close to due east and set very close to due west.

If you want to be really accurate then the first star in the belt to rise and set, called Mintaka (Among three stars in the Orion Belt it is towards the Betelguese), will always rise and set within one degree of true east and west wherever you are in the world.

By K S Chadha, Jun 16 2016 07:20AM

Steps Involved:-

1) Shoot an imaginary line directly out of bottom of the Constellation Cross.

2) Shoot an imaginary line directly between the pointers and perpendicularly bisect the line between the pointers.

3) Where these lines meet is the approximate position of South Celestial Pole.

4) Face the point where these lines meet in the sky and you will be facing directly South.

By K S Chadha, Jun 15 2016 07:06AM

Place of observation : NEW DELHI, INDIA


1) At solar noon (merpass) sun sits highest above the horizon for that day.

2) This means the sun casts the shortest shadow at that time.

Steps and Procedures

1. Place a whit sheet on the cardboard. The cardboard needs to be secured and levelled. (See Image)

2. To collect data note and record time, then mark end of the shadow of the nail. (See Image)

3. Prefer to start at 1000 hrs zone time.

4. Take first few recordings with 20-30 minutes apart and then reduce the time period to 5-10 minutes. Finish your observations at 1400 hrs zone time. (See Image)

5. Determine time for the shortest shadow. In this case it is 1220 hrs zone time. (See Image)

6. Now we have to relate our local noon time to time in Greenwich.

7. We know time zone in India is (UTC +5:30), so the solar noon occurred in NEW DELHI, INDIA was at 0650hrs GMT.

8. We know that merpass approximately takes place at 1200hrs LMT. That means earth has to rotate for about 12h – 0650h = 5hrs 10min in order for sun to reach Greenwich.

9. At rotation speed of about 15°/hr, the earth has to rotate for 5h 10min (5.167 hrs) to reach Greenwich.

10. Total rotation by earth in 5.167 hrs = 5.167 * 15 = 77.51°

11. Thus calculated longitude is 077.51° E (E because our local time is ahead of GMT).

12. GPS Longitude = 077.21°E

By K S Chadha, Jun 3 2016 05:03PM

The IMO ship identification number is made of seven-digit number. This consists of a six-digit sequential unique number followed by a check digit. The integrity of an IMO number can be verified using its check digit. This is done by multiplying each of the first six digits by a factor of 2 to 7 corresponding to their position from right to left. The rightmost digit of this sum is the check digit. For example, for IMO 9074729: (9×7) + (0×6) + (7×5) + (4×4) + (7×3) + (2×2) = 139.

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