Astronomy Learning and Research / Beginning Astronomy / Observational Astronomy

Amy’s Analemma

I’m working on an observing program called the Analemma program. I chose this one for a few reasons, one being I don’t have to get bundled up in the middle of the night, drive out to the middle of nowhere only to be clouded out – again.  This one is done during the day, observing something we see everyday – the sun. I still get clouded out, but I’m only in my front yard so it’s no problem!

Analemma refers to the changing declination of the sun. Basically all you need to do is make an observation of the sun about twice a week for a year. You’re not observing the sun itself, (please – no looking directly at the sun) but rather the length of the shadow it creates. You need to make the observation at the same time (noon) and in the same place every time. You are measuring the length of a shadow, placing a dot on a piece of paper where the shadow ends. Over the course of a year the dots will form a figure eight.

Here’s my setup. I used an 11×14 picture frame and put a dowel on one end. Yes – that’s zebra stripe duct tape. Don’t ask. The trick here is the length of the dowel. It can’t be too long because in the winter the shadow will be too long to fit on the paper (it has to fit on a normal piece of paper) I actually started thinking about this in the winter, so on December 21st (the shortest day of the year) I went outside with a piece of paper and a pencil. I put the paper down on the driveway and stood the pencil next to it to measure the length of the shadow. That’s how I figured out how long to make the dowel. Time will tell if my not so scientific method works out!

Here’s my analemma so far. I’m at the half way mark! You can see the small end of the figure eight forming. The dots aren’t always in line, that’s due to the timing of placing the dot. I think I’ve got that worked out now! An atomic watch works great for this! There’s also that bloppy dot I made with a regular marker, big mistake. I now use a fine point marker. I’m really not looking forward to doing this in the dead of winter, but it may help make winter  move a little faster.

I think I should tell you that after the figure eight is complete there’s some fun math involved to finish the program. Yes, I do mean fun!

I’ll keep you posted on my progress!

Amy

2 Comments

  1. Pingback: That Darn Dog

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