NavList:

Hello!

As we've get a nice four-day-long holiday till next Monday, so I'm taking my sextant to the Finnish Gulf shore to practice a bit. Still no scope, only the ghost ring attached.

After the index mirror adjustment and horizon mirror tuning-in - I guess only the excentrisity error remains.

I found a book from 1976 on the navigator's equipment handling and adjustments. Among other things it explains how to calibrate a sextant by star-star measurements. This particular topic was already discussed here some time ago.

Here's what that book says on the topic:

• to measure the six certain angles, star-Polaris;
• properly clear the data;
• compare with the given table.

The suggested stars are (see p-045):

• Kocab;
• Alioth;
• Capella;
• Vega;
• Alpheratz;
• Altair.

One can easily calculate the current angle values from the current NA.

But the book goes on and gives the table (see p-290) with per-month star-Polaris angles. Some of those angles do change noticeably though the year.

What is this? A parallax by Earth's orbiting the Sun, right?

Since I'd like to make an estimation of the excentrisity in my sextant - where can I get the modern parallax data (per-month) of those stars?

Please comment.

Regards,

Tony