F
REQUENTLY
A
SKED
Q
UESTIONS
Can I take the optical tube off of the mount when I move the scope?
The optical tube on Zhumell Dobsonian telescopes can easily be
taken off of its base. Removing the optical tube assembly from the
base makes moving your Dobsonian much easier and will help
prevent damage to the mount or optical tube during transport.
To remove the optical tube from the mount, simply unscrew the
spring system bolts which screw into the side of the optical tube,
slide the springs off of the spacers, and lift the optical tube out of
the mount cradle. Be sure to screw the spring system bolts back
into the optical tube so that they do not get lost.
How do I know when I need to collimate my telescope?
When the optics of a telescope are out of alignment, image clarity
will be lost. In extreme cases, you may not even be able to focus
on an image. If you notice that you are having problems achiev-
ing focus, try collimating your telescope. It is reccommended that
reflector telescopes be collimated every time they are used.
Can I take astrophotographs through my Dobsonian?
Astrophotography generally requires long exposure times in or-
der to compensate for the limited amount of light available for
shots of stars and planets. Since long exposures are required, your
Dobsonian telescope will not work well for astrophotography.
Due to the rotation of the Earth and the apparent movement
of the stars, a tracking motor is needed for astrophotography. If
you are considering trying astrophotography, we reccommend
looking into purchasing an equatorial (EQ) mount with a motor
drive.
What is the small, inner dust cover on the front of the optical tube
assembly for?
The small cover inside the full dust cover on the front of the
optical tube is designed to limit the amount of light which enters
the tube. The only time this opening should be used is in con-
junction with a solar filter. During normal nighttime viewing,
the entire front dust cover should be removed to maximize the
light which enters the optical tube.
Can I use the optical tube from my Dobsonian on any other mounts?
The optical tube from you Dobsonian telescope will work on
any type of mount, as long as the mount is able to support the
weight and size of the optical tube while still moving freely. In
order to use the optical tube from your Dobsonian telescope on
an equatorial mount, you will need to purchase the correct size
tube rings and a dovetail plate which will allow you to attach the
optical tube to the mount. Tube rings can be purchased in many
difference sizes and are available through many astronomical
retailers. In order to determine the suze tube rings you would
need, measure the diameter of the optical tube (which is larger
than the diameter of the primary mirror). If you have questions
about whether a particular mount will work with the optical
tube, please check with the mount manufacturer about the speci-
fications for the mount.
Why is it called a Dobsonian telescope?
Although it is based on the Newtonian optical tube design, the
Dobsonian gets its name from the person who developped the
type of mount used on most Dobsonian telescopes. John Dobson
revolutionized the world of astronomy by making telescopes out
of „junk“. One of his first telescopes was made from a ship’s
porthole window (ground into the primary miror), scrap wood,
and cardboard. Mr. Dobson’s approach to design drastically
reduced the price of telescopes and made the price of large aper-
ture telescopes accessible to amateur astronomers. John Dobson
was known for both his ingenuity in using common materials
and his outreach to the general public through the San Francisco
Sidewalk Astronomers.
The image I see in my finderscope is not the same as the image I see
through my telescope. What is wrong?
In order for the finderscope to show the same part of the sky
which your telescope should see, the finderscope must be aligned.
Since the finderscope has less magnification and a wider field of
view than the telescope, it will help you to zero in on stars once
it is properly aligned with the optical tube.
Summary of Contents for Dobsonian
Page 1: ...DOBSONIAN TELESCOPES...
