How closely spaced are the grid lines in the chart annotation?
The “heavier” dotted lines are spaced 5 degrees apart (which is 20 minutes of right ascension); the lighter lines are spaced 1 degree apart (4 minutes of right ascension). 4. Errata 4.1. Why do some annotations appear below the horizon or behind land objects? The annotations are created using a mathematical model which doesn’t take account of the horizon (or objects near the horizon, such as mountains, buildings, trees, etc), so some stars are annotated even though they are not visible in the photograph. 4.2. Why are some photographs not annotated? In many cases, it’s because I’m lazy and haven’t gotten around to annotating several photographs, though I hope to do this soon. 5. Miscellaneous 5.1. What is the absolute limiting magnitude on these photographs? It varies per photograph, but 7th magnitude stars are visible in most of the better photographs, and 8th magnitude stars are visible in some of the photographs. I believe I’ve seen blue stars with visual magnitudes as high as 9.0 in
