Point count: 6
1. Observe at least 6 solar system objects. Draw a sketch using the jpg or pdf observing form, being sure to note the location, telescope used, etc. Use a different page for each session. One of your objects can be the Sun (use safe techniques!) or a sky view of a planetary conjunction (sketch or photo).
You may do them on any Saturday evening at George Observatory, at any Rice Observatory Open Houses, or during class sessions. We will have "Observe the Moon Night" on October 3. If you are out of town, find a local astronomy club! Or, you can sign up to observe using SLOOH.
Limiting magnitude: The "limiting magnitude" is the magnitude of the dimmest star you can see with your naked eye. (check a star chart to see what the magnitude of various stars is)Field of View: You can use the Moon to judge your field of view (the Moon is a half-degree across). Or given Jupiter's or Mars' size in your field of view, you can estimate the field of view of the eyepiece by seeing how many Jupiters or Marses fit across the field of view. Or, if you are attaching a photograph from an eyepiece, or photograph of a planetary conjunction, estimate the field of view of your photo.
To use Jupiter: Find out how far away Jupiter or Mars was the day you observed (you can use Stellarium, for example). Use its physical size to get its angular diameter; from that you should be able to calculate the field of view.
Angular size: The angular size of an object in RADIANS is its diameter divided by its distance (both must be in the same units!). Once you know the angle in RADIANS, multiply by 57.3 to get the angle in DEGREES, or multiply by 206,000 to get the angle in arc seconds.
NOTE: once you calculate the field of view using one eyepiece/telescope combination, it stays the same for other objects using that eyepiece and telescope.
Magnification: Equals the focal length of the objective divided by the focal length of the eyepiece. The Focal Length of the observatory 16 inch telescope is 4 m; of the 11-inch Celestron is 2m; of the 8 inch, 1 m.
Download the jpg or pdf of the observing form. Save it and print it from a print program, or print at 50% from your browser.
There will be at least four evening sessions, but we get clouded out a lot, so be sure to come to the first possible session you can!
Or, you can go the "George Observatory" (in Brazos Bend State Park) any clear Saturday evening.
last revised: 8/30/2025
