AST 3722C
summary for lecture on tuesday january 8, class #1.
warning: this is not supposed to be a substitute for reading
the textbook.
Textbook Chapter 5:
What astronomers do is measure I  photon flux.
I is a function of a lot of things:
wavelength
direction
time
polarization
I = I(lambda, Omega, t, P)
So in this class you're going to learn about how we measure this
function. We must infer everything physical about the Universe just
from interpreting the samples of this function that we get. And we
often don't get to sample across a very
large range of parameter
space. But you could imagine a hypothetical situation where you
sample the whole cel. sphere at every wvln in very short intervals
of time with very good spatial resolution. This is not possible
techn. Yet but we can approach some interesting things, e.g.: LSST
PanSTARRS are 2 projects that will soon go online to sample the
sky at visible wavelengths to a faint magnitude at fewday intervals
at good spatial res at 4 wavelengths.
Textbook Chapter 7:
recall the celestial sphere from AST 2002.
The cel sph spins around earth, though that's just a model  Earth
is spinning. Stars are more or less fixed on the acrylic. Planets,
Sun, Moon for the most part move with the acrylic too but not
entirely. We'll get to more on all of this later.
spherical trig terms:
great circle  shortest distance between 2 points on the sphere.
a great circle has to enclose the center of sphere.
small circle  a circle on the sphere that doesn't enclose the
center of the sphere
spherical angle  2 great circles intersect.
spherical triangle  3 great circles intersect.
note that I didn't clearly make this distinction in class but: in
a spherical triangle, you have 3 "sides" and 3 angles. those angles
are indeed spherical angles  and you can measure or calculate the
numerical value of the angle between the 2 "sides" that are making
each angle. the sides are represented by angles too  the relevant
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '09
 Fernandez
 Astronomy, textbook chapter, right hand rule, great circles

Click to edit the document details