Here is how to make overlays and find objects with them.
I assume that many of you already know many of the major constellations.
Constellations are landmarks to help one learn the sky and to find what star
to star hop from. You don't have to learn the little insignificant ones but
learning majority of the major ones is an absolute must.
The night sky is represented as a globe simular to the Earths grid. There
are two coordinate lines. Right Ascension is the lines that are vertical
east and west. It is measured in hours dividing the sky in 24 one-hour
lines. Each of those one-hour lines is divided with 60 one-minute lines.
Each one-minute line is divided in 60 one-second lines. Declination is the
horizontal north and south lines. At the north celestial pole near where
Polaris is, is the + 90 degrees declination mark. 0 degrees is where the
celestial equator is and -90 degrees is the southern celestial pole. Just
like on Earth. We measure distances between two stars or galaxies or any
other object by degrees. For example, the distance between Rigel and
Betelgeuse is 18.6 degrees. Armed with this knowledge one can invent many
ways to locate deep sky objects.
There are other things you need to know and that is field of view of your
eyepiece, finder and Telrad. Some people ask me which should I get a telrad
or a finder scope. The Telrad is an absolute must period. There are other
zero power pointing devices, such as the daisy sight. The daisy sight is no
good because it is just a point of light and you can't measure distances
with it. The telrad on the other hand has three circles the smallest is half
a degree, the mid sized is 2 degrees and the largest is 4 degrees. That will
allow for measuring and will make star hoping easier. The finder scope is an
optional luxury that is used in conjunction with the Telrad. If you choose
to get one you will need to have a 50mm objective or larger. The eyepiece
you use to find objects needs to be one degrees or more in field of view. To
find out the field of view of your eyepiece you divide the apparent field of
view by the magnification that eyepiece will yield with your scope. You can
find out the apparent field of view from the manufacture of the eyepiece or
documentation supplied with the eyepiece.
Making and using overlays greatly helps one find object. One of the best
ways is transparency paper. To make an overlay for the Telrad you will need
a marker and a compass. The inner smallest circle it is so small there is no
need to measure just make a little circle. The mid sized circle is two
degrees. The distance between the point and the marker of a compass is the
radius of the circle. With that in mind use your atlas as a guide. Open the
compass to match one degree on your atlas. With the large outer circle open
it two degrees. For the eyepiece and finder scope you will use the compass
to make the circle to scale with your atlas. Those of you with computers
programs like Guide and Skytools will print eyepiece, Telrad and finder
scope overlays on the charts.
Overlays will help you know where to aim your Telrad in relation to the
stars and let you know what stars are in the field of your finder scope and
eyepiece. It takes the guesswork out and makes it harder to get lost.