I. Introduction: The visibility of the night sky is constantly changing. Thick clouds obscure stars completely while haze in the sky reduces the contrast of the night sky and limits the view of the stars. The Earth's moon acts as natural light pollution against our background of stars and artiicial light pollution from human sources inhibits views of the sky.
When viewing through a telescope, the features of this instrument also play a role in how the stars are seen. For example, magnification or quality of the optics. As we study the sky, we want to quantify this variability of the night sky. We can label this as the limiting magnitude. The limiting magnitude is the magnitude of the faintest star in the sky we can see. When we take this measurement from observing through a telescope, either visually or digitally, we ind our Limiting Telescopic Magnitude. This magnitude is a simple way to keep a record of the variability. With the right information, this limiting magnitude can be accumulated every night. By providing pictures of some open clusters and their respective magnitudes, an observer can take a telescope and their look of the sky, and determine the limiting magnitude. Using this information is easy: simply determine the orientation of your telescope and choose one of the clusters you can see in your sky below. Then, determine the faintest star with aid from our gif and note its magnitude. In this way, the Limiting Telescopic Magnitude can easily be determined and the data collection of variability of the night sky has begun.
II. Right Acension and Declination:
M34: 02 42 07.40 +42 44 46.1 -- Bright Stars (East-left) (East-right), Faint Stars (East-left) (East-right)M67: 08 51 20.13 +11 48 43.1 -- Bright Stars (East-left) (East-right), Faint Stars (East-left) (East-right)
M39: 21 31 48.32 +48 26 17.4 -- Bright Stars (East-left) (East-right), Faint Stars (East-left) (East-right)
III. Citations:
Inspired by Pitcairn's informational piece in the annual Observer's Handbook, we wanted to make similar charts for astronomy students in and near Bowling Green, Ohio to find their Limiting Telescopic Magnitude. By releasing these charts online, we hope to inspire and assist with finding your own limiting magnitudes.
"Limiting Magnitudes" by Douglas Pitcairn, Observer's Handbook 2016, The Royal Astronomical Society of Canada Images: NASA STScI Digitized Sky Survey Magnitude Data: AAVSO's APASS database Gif Rendering: Kapwing Studio
