1/C MTRA Celestial Navigation Assessments
Starting junior year at the Academy, MTRA cadets learn how to use a piece of equipment that has been used in their industry for hundreds of years. This important equipment is called a sextant.
Here is a labeled diagram of a sextant.
A sextant is used to measure the altitude of celestial bodies. Sextants were the sole means of finding locations without using electricity. If a ship in the middle of the Atlantic Ocean were to lose power, they would be out of luck unless they knew how to use a sextant properly. As a part of their educational responsibilities onboard, 1/C MTRA cadets are required to complete a celestial navigation booklet using their sextant.
This shows the reading numbers on the sextant.
These shades prevent the sun from blinding the user when he/she looks at it.
This is the handle and the eyepiece.
Here is the assessment booklet that the cadets must complete. Out of the ten assessments, this cadet earned ten perfect scores!
During Alongside Week, each cadet received their own sextant to complete this project. The project takes a while to complete because there is a total of nine assessments with three being part of exams. The remaining six assessments require three practice problems to be done before a cadet make take the assessment.
As of now, 1/C Mac Halperin-Reiss is the only cadet to finish his entire Celestial Navigation project. The Marine Transportation Training department onboard, led by Captain John Belle, set forth benchmarks that required cadets to have so many assessments completed before they were able to enjoy liberty. For Barbados, only three assessments need to be done, Puerto Rico requires four assessments, Tortola five, and the cadets should be done before we reach Miami. On the cover of the Assessment booklet there are three quotes.
“The beauty of celestial navigation is that you don’t have to know where you are to determine where you are.”- Anonymous
“A compass can go wrong, the stars never.”- Tongan Saying
“If you rely solely on GPS to cross an ocean, you will not know if you are correct until the last day.”- Anonymous
These quotes relate to how the Training Department feels about the knowledge of sextants. They believe that learning this unique yet relevant skill will aid their cadets in their maritime careers.
This brief video will introduce you to the sextant.
How To Guide For Learning To Use A Sextant
After watching the 1/C Cadets complete assessment after assessment with their Sextants, I wanted to learn how they work and how to properly use them. I met up with 1/C Erin Sullivan from Texas A&M Maritime Academy to get my answers.
Before assessments began, Mate McCrae did a quick introduction lesson to refresh the 1/C cadets on how to use a sextant and complete the math related to finding your location. In this three-hour class, cadets take shots of the sun and then work out the problems together. Erin explained the proper way to use a sextant in basic language so I would understand. To first use a sextant, you have to correct it. There are three different types of errors that may happen with sextants. They are side error, index error, error of perpendicularity.
The side error occurs when the larger mirror on the sextant is not completely perpendicular with the frame. Perpendicularity is when the smaller mirror is not perpendicular with the frame. Finally, index error is when the two mirrors are not parallel to each other. Correcting a sextant can take a while but it needs to be done because it can cause inaccurate shots.
Once you’ve corrected your sextant you can move on to actually taking your shots of the stars and sun. A shot is the reading taken from the sextant to find how high the celestial body is from the Earth. When the shot is taken, you then proceed to use different publications and math formulas to calculate a bearing of the body to get a rough estimate of your position.
If done correctly, you would be able to predict where you would be in the following hour. Erin has five assessments completed and is on track to finish them tomorrow. She is one of the first cadets to finish the entire booklet and is looking forward to being done.
Here is another assessment sheet.