celetron c-150 hd?

I just purchased one of these. I am a beginner and this is a 6 inch
reflector. Is this ok to start out with? One thing, the finder scope needs
to be replaced since it is a 6 by 30. Anyone have any recommendations on
what I should buy and what mail order offers the best price? What about
thoseTelrads?
thanks

Hi,

I have a CR-150, they are reasonable scopes. One of the first tests you
should do is to take it out and point it at a bright star. Look around the
star for a purple haze. If you see none, you have a very nice scope. If
you see some, you still have a very nice scope. If you have a lot of purple
haze, then the scope can be corrected... Head out to a photo store, and get
a light yellow filter, or spring for a Minus Violet filter, and screw it
into the base of the 2 inch to 1 1/4 inch adapter, then leave it there.

The filters should be 48 mm in diameter. With regards to eyepieces?
Download "to-Calc" from www.nexstar11.com, select "Downloads". It is a
calculator for eyepiece/telescope combinations. You should look at the max
power your scope will perform, (on to-calc), and not buy an eyepiece that
will get close to that power. Start with low power eyepieces, then creep up
on the high poser limits.

Hope this helps...

Thanks,
Dave
For Nexstar11GPS tips, tricks, and general information visit
http://www.nexstar11.com. astronomy software visit www.nexstar11.com, select
"Downloads"
The UNOFFICIAL site for NexstarGPS information.
All information is "In my opinion" and not to be taken as fact.


"n3drk" wrote in message
news
I just purchased one of these. I am a beginner and this is a 6 inch
reflector. Is this ok to start out with? One thing, the finder scope needs
to be replaced since it is a 6 by 30. Anyone have any recommendations on
what I should buy and what mail order offers the best price? What about
thoseTelrads?
thanks

Forget the finder.

Get a Telrad.

"n3drk" wrote in message
news
I just purchased one of these. I am a beginner and this is a 6 inch
reflector. Is this ok to start out with? One thing, the finder scope needs
to be replaced since it is a 6 by 30. Anyone have any recommendations on
what I should buy and what mail order offers the best price? What about
thoseTelrads?
thanks

Here is some information about finders.

FINDERS FOR ASTRONOMICAL TELESCOPES

The use of some sort of sighting instrument, or "finder" is required in
order to put celestial objects in the main telescope's relatively narrow
field of view. There are two basic types of finders: finderscopes, and
unity-power "sight" finders.
FINDERSCOPES are small low-power wide-field secondary telescopes mounted
alongside the main instrument in adjustable mounting rings for aligment with
the main telescope. They usually have an eyepiece with crosshairs for object
centering, and a wide field of view which is several times that of the lowest
power field of the main telescope. Once the finderscope properly aligned
with the main telescope, the user can put an object in the telescope's field
by merely moving the main scope around until the object of interest appears
centered in the finderscope's crosshairs. It should then be in the field of
the main telescope. Some finderscopes have a light source for low-level
illumination of the crosshairs, which can be useful on a dark sky, as long as
the illumination does not wash out the target stars. Many finderscopes use
a star diagonal to put the viewing eyepiece in a more convenient position,
although it does reverse the field, making reference to star atlases more
difficult. Some equipment manufacturers have introduced right-angle "correct
image" finderscopes with amici prisms inside their star diagonals. This
produces an upright and correct right-to-left field of view in a very
convenient viewing location.
The minimum aperture for a finderscope is a subject of some debate. The
tiny finders provided with smaller department store telescopes are almost
useless, since they have only a single-element objective lens followed by a
tiny aperture stop, cutting the effective aperture to under 10mm. Many
observers have difficulty seeing many fainter stars through finderscopes with
objectives smaller than 30mm, and for a "standard" finder, a 50mm aperture is
often recommended. As for magnification, the finder should have at least 7
power and at least a 5 degree field of view, so that objects may be located
easily. Some seasoned observers who go for very faint targets with large
telescopes will even recommend using 60mm to 80mm finders in the 8 to 15
power range, although with the larger sizes, the number of faint stars
visible with these large finders may end up confusing the inexperienced
amateur.
1X FINDERS: These are just what the name implies: finders which do not
magnify or enhance the view. They range from simple sighting tubes or
gunsight-like devices, to illuminated reticle-type systems. The simple tube
sights will get you in the ballpark, but in dark skies they can be a little
hard to use. The "reflex" sights with illumination put a small red dot on a
tilted glass plate, allowing the user to look through the plate at the sky,
see the dot and place objects on it for finding. However, the object should
be visible to the unaided eye for this to work well. Many amateur
astronomers have built their own inexpensive dot-reflex finders from simple
ones found on some gunsight systems. In some cases, these simple reflex
finders can be a little easier for the beginner to use initally than an
optical one.
One of the best known commercial 1x finders is the TELRAD, a reflex-type
finder which puts an unique three-ring reticle of adjustable brightness in
the viewer's field. These rings are 0.5 degrees, 2 degrees, and 4 degrees in
diameter on the sky, and are most useful, not just as a simple bulls-eye, but
as a "pattern maker", for star hopping. By using overlays which resemble the
Telrad's reticle pattern on star atlases, and centering the target object's
chart location in the overlay, star patterns and alignments with the Telrad
rings in the area around deep-sky objects can be worked out which can then be
duplicated by looking through the Telrad at the night sky. The Telrad rings
can also be used as measured "steps" in extended star hops. This can make
finding even faint non-naked eye objects much easier than with the simple
"dot" finders. Those people who insist on downplaying the Telrad's
usefulness based on merely using the unit only as a "bull's-eye" centering
finder like the "dot" sights do not really understand how to use a Telrad!
It is the pattern making or stepping-off field size which makes it a truly
valuable finding device for the telescope.
The Telrad is a bit bulkier than some of the simpler "dot" sights, but its
low cost (less than many telescopic finders) and simplicity have made it very
popular, especially among Dobsonian telescope users. For smaller scopes,
another popular reflex finder is the Rigel Quickfinder, which is smaller and
lighter than the Telrad. However, it only produces two rings in its window
instead of the Telrad's three, and is a bit more fragile physically.
As for which is better (Telrad Vs. Finderscopes), it really depends on
the individual's preference. Many amateur astronomers use both a finderscope
and a Telrad on their instruments for locating objects in the night sky.

Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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