Last night, the Austin
Astronomical Society sponsored an “Out of the Box Clinic” for new astronomers
with unused or under-used instruments.
The event was held at our Canyon of Eagles “Eagle Eye” Observatory near
Lake Buchanan, about 80 miles northwest of Austin. (I did not attend.) Following
that, today the club president issued an email to make further recommendations
based on the interactions between newbies and sages. He was wrong on every
point.
"1) A decent finder is crucial: Some of your scopes had no finder.
Others had the old fashioned tube finders that are very hard to calibrate with
their three thumbscrews. I recommend you pick up an inexpensive Red Dot
Finder for your beginner scopes. We can help you install it or swap it
with your tube finder."
A. I
started as a kid with the old-fashioned tube with crosshairs and six screws:
three front and three back. It was
easy to use and the crosshairs were a reliable reference for moving the
telescope up-down-left-right when I lost the object under higher magnification.
(See #3.) I now have a new, modern telescope with a Red Dot Finder. It is a
pain in the neck, literally. I usually sit on the ground to look through it.
B. Nothing
is ever where the dots may (or may not) line up. Do this for yourself: Use your
index fingers pointing upward about a foot apart, and not lined up with your
eye. Now, sight some object in the room and move your head back and forth until
both fingertips line up with it. You are off-center. You are not lined up. But
you think you are. With the little
red dots and the little bright stars, it happens all the time.
C. The
best thing for me is to put some bright star in the telescope center and then
align the viewer to it, using the two insufficient screws to set it. I say
insufficient because two points make a line, but three are needed to fix a
plane and the viewing field is planar
D. You
will need their help installing a new finder because you will have to drill
holes in your telescope, mount screws washers and nuts – and not drop anything down the tube to damage the mirror or lens.
"2) Calibrating the view in your scope to the view in your finder is a
necessary first step. With some of you, we spent time trying to dial it
in during the daylight hours so you'd be prepared when the sun went down.
For those of you without finders, you experienced a lot more challenges getting
your tubes pointed at the objects you want to see."
A.
Turn Left at Orion. The sages with their huge Dobsonian “light
buckets” often do not have finder scopes at all. They know the sky and “star
hop” to find what they want to see.
B.
Because my Red Dot Finder is so useless, I
often sight up along the tube to locate an object. You get close then make small moves. That was the advice
that Ellie Arroway’s dad gave her with the ham radio, and which she followed as
an astronomer: small moves. (See Contact by Carl Sagan.)
C.
The sages should have been pretty good at
teaching this because it is what they do with their own Dobsonians. (See A
above.)
"3) Get a low-magnification eyepiece. For beginner scopes, nothing
beats a good 40mm Plossl-type eyepiece. Most of you showed up with a
24mm or a 20mm eyepiece as your lowest magnification eyepiece. There's
nothing wrong with those magnifications. However, you will find it easier
to bring your target into view with a low-magnification eyepiece. Once
your target is identified, then you can swap to your higher-power eyepiece(s)
for viewing."
A.
Now you tell me. (And what is a "Plössl"? Note the umlaut-o: "Play-sell.")
B.
I bought a
beginner telescope, a Celestron 130-EX refractor. It came with a 20mm ocular
and a 10mm ocular. Then I bought a
box of eyepieces for beginners. The biggest is 32 mm. But, you know what, my first telescopes were not much
different. I never had a big eyepiece. I learned with the little ones – not the
littlest; admittedly, the largest of them; and the middle one. The laws of optics
are against high magnification on a little telescope.
C.
Speaking of the
laws of optics, the diameter of the
ocular is only one factor in the equation of magnification. M = f/d. The Magnification is the focal
length of the telescope, divided by the diameter of the ocular lens. So, a
small telescope with a 24mm eyepiece will have lower magnification than a larger (longer) one. Lower
magnification is easier to work with when hunting objects – especially without
a finder scope. But that is not just a function of the ocular.
D.
Moreover, the
other factor is the light-gathering area of the main lens or main mirror, the “aperture.” A 10-inch mirror gathers
four times as much light as a five-inch mirror: area increases by squares. So, a beginner with a 3-inch telescope
will gather 40% more light than a beginner with a 2-1/2 inch instrument.
E.
That’s nice to
know… but if you did not buy a 3-inch telescope but got the smaller one, then
the point is moot. The reason for the
“Out of the Box Clinic” is supposed to be to help you get the most from your
instrument, not make you wish that you worked at Mount Palomar.
F.
And once you have
your object in the low-power field of view, moving to higher power is also
another thing to be learned. If you are off center by little bit, when you drop
that higher power eyepiece in the viewer, you may well have to start over finding
the object. There is no way around
it. It is not like flipping TV channels with the remote.
G.
Finally, the AAS
should have had eyepieces at the ready. These things are pretty standard and
come in only a few diameters. That would have been more productive than telling
people what they should have done.
"4) Several of you asked about choices for your next, "better"
scope. We have some suggestions on an FAQ page on austinastro.org. http://austinastro.org/index.php/f-a-q/#bestscope"
A.
Buy the most
telescope you can afford. It is like any other tool. Any mechanic, craft
worker, or technician will tell you the same thing. None of the advice I saw
actually explains that when you buy a telescope, you are getting three things:
a telescope, a mount, and a tripod.
B.
Every instrument
I have seen for consumers is a collection of junk because compromises are made
for the production of each component.
But it does not need to be that way.
C.
For the AAS
magazine, Sidereal Times, I
interviewed a member who is a mechanical engineer. He broke the problem down
and bought the best telescope, the best mount, and the best tripod that he
could afford, each from a different
source.
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