Michael Hotka's
Activity 12 - Measuring - 30 Navigation Stars Results

Use your astrolabe and/or quadrant to measure the positions of at least 30 of the 57 navigation stars (https://en.wikipedia.org/wiki/List_of_stars_for_navigation) visible from your location.

If you live too far north you won’t be able to see all of the navigation stars.

Use the astrolabe/quadrant in transit mode for at least fifteen of the stars. For these fifteen stars record the local sidereal time of the observation.

For all of the stars record the data as altitude (height), azimuth (direction), date and clock time to the minute. From the alt/az data and your location calculate the right ascension and declination. You can find sidereal clock software on the Internet. You may use a compass to help measure the positions when not using the transit method. See the document “Converting Horizontal Coordinates to Equatorial Coordinates” in the Link section below.

Results

My Observations

I tried to use my Jacob's Staff for this Activity but found it impossible to determine a reliable ground reference in my neighborhood that represented the actual hotizon. You can see the one measurement I tried to use the Staff for on Pollux was not even close to the correct altitude.

I decided to just used my Quadrant and Astrolabe, which didn't depend on an accurate horizon, for this Activity.

The way I converted from the horizontal coordinates of azimuth and altitude to equatorial coordinates of RA and Dec was to use Stellarium's conversion interface.

I started Stellarium on my PC. When the program was fully running, I moved the mouse cursor to the left hand side of the screen. There a menu appears and I selected the first icon, the Location window. I used the search interface to find Broomfield, Colorado, USA as my location and made this the default location.

To convert the quadrant coordinates to RA and Dec, I did the following:

1. Stop Stellarium's current time from advancing. Move the mouse cursor to the bottom of the screen and a menu appears. Click the fourth icon from the left to change the solid arrow head to two vertical lines. You will notice the time on this part of the screen stops incrementing.
2. Move the mouse cursor to the left hand side of the screen until a menu appears. Click the second icon from the top, the Date/time window. Enter the date and time of your observation you want to convert.
3. Move the mouse cursor to the left hand side of the screen until a menu appears. Click the fourth icon from the top, the Search window. In the Position tab, change the Coordinate System to Horizontal.
4. Enter your azimuth and altitude readings you took with your quadrant.
5. In the Position tab, change the Coordinate System to Equatorial.
6. Read the RA and Dec values and put them into the results spreadsheet for this observation.