Orion STARBLAST User manual

INSTRUCTION MANUAL
IN 293 Rev. C 02/09
Providing Exceptional Consumer Optical Products Since 1975
Customer Support (800)-676-1343
E-mail: [email protected]
Corporate Offices (831)‑763‑7000
89 Hangar Way, Watsonville, CA 95076
Orion®StarBlast™Imaging
Optical Tube Assembly
#9974

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Figure 1. The StarBlast Imaging OTA.
Focuser
Focus knob
Thumbnuts
Primary mirror cell
Secondary mirror
holder

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Congratulations on your purchase of an Orion StarBlast
Imaging optical tube assembly (OTA). Your StarBlast
Imaging OTA is a Newtonian reflector telescope with high qual-
ity optics and excellent mechanical construction. It has been
specially optimized for use with astronomical CCD imaging
cameras that utilize chips up to 1⁄2" in size. These instructions
will help you set up and use your telescope.
Getting Started
The StarBlast Imaging OTA comes nearly fully assembled from
the factory. The telescope’s optics have been installed and col-
limated, so you should not have to make any adjustments to
them.
Please keep the original shipping box! In the unlikely event you
should need to ship the telescope back to Orion for warranty
repair service, you should use the original packaging. The box
also makes a very good container for storing the telescope
when it is not in use.
Attaching the StarBlast Imaging OTA to a Mount
The StarBlast Imaging OTA can be attached to a mount by the
use of optional tube rings. Tube rings with an inner diameter
of 140mm (5.5"), such as Orion item #7373, are needed. First
attach the tube rings to your telescope mount, then place the
optical tube in the tube rings.
Use of Optional Finder Scope and Eyepieces
The StarBlast Imaging OTA does not come with a finder scope
or eyepieces in order to grant the user the greatest versatility
in customizing the instrument to suit their tastes. However, cer-
tain rules for using accessories still apply.
To use any Orion finder scope that has a dovetail bracket,
an optional dovetail holder (Orion #7214) is required (Figure
2). To attach the dovetail holder to the tube, first remove the
thumbnuts from the screws located near the focuser (Figure
1). Then, remove the screws themselves by unthreading the
exposed hex nuts. Keep the tube in a horizontal position when
doing this in order to prevent the screws from falling inside the
telescope and onto the primary mirror. Now, use the hex nuts
and screws that come with the dovetail holder to attach the
holder to the tube. The dovetail holder should be oriented so
the notch (Figure 2) is facing the rear (primary mirror cell) of
the telescope.
To connect the finder scope, simply unthread the thumbscrew
on the dovetail holder, and insert the base of the finder scope
bracket. Retighten the thumbscrew to secure the finder scope
and bracket in place. Finder scopes that do not use a dovetail
bracket will need to be attached by some other means.
The StarBlast Imaging OTA can use almost any 1.25" eye-
piece. Insert the eyepiece into the focuser and secure it with
the thumbscrews on the focuser’s drawtube. Focus the eye-
piece by rotating the focus knob.
Calculating Magnification (Power)
It is desirable to have a range of eyepieces of different focal
lengths to allow viewing over a range of magnifications. To
calculate the magnification, or power, of a telescope, simply
divide the focal length of the telescope by the focal length of
the eyepiece:
Telescope Focal Length (mm)
= Magnification
Eyepiece Focal Length (mm)
For example, the StarBlast Imaging OTA, which has a focal
length of 450mm, used in combination with a 25mm eyepiece,
yields a magnification of
450 mm
= 18x
25 mm
Every telescope has a useful limit of power of about 45x-60x
per inch of aperture. Claims of higher power by some tele-
scope manufacturers are a misleading advertising gimmick
and should be dismissed. Keep in mind that at higher pow-
ers, an image will always be dimmer and less sharp (this is
a fundamental law of optics). The steadiness of the air (the
“seeing”) will usually limit how much magnification an image
can tolerate.
Always start viewing with your lowest-power (longest focal
length) eyepiece in the telescope. After you have located and
observed the object with it, you can try switching to a high-
er-power eyepiece to ferret out more detail, if atmospheric
conditions permit. If the image you see is not crisp and steady,
reduce the magnification by switching to a longer-focal-length
eyepiece. As a general rule, a small but well-resolved image
will show more detail and provide a more enjoyable view than
a dim and fuzzy, over-magnified image.
Astroimaging with the StarBlast Imaging OTA
Because of its “fast” F/4 optics, the StarBlast is a great tele-
scope for wide-field astroimaging. This version of the StarBlast
telescope has been optimized specifically for use with astro-
nomical CCD imaging cameras, like the Orion StarShoot
cameras. Unlike most telescopes, it provides full illumination
across the entire field of view of a CCD chip up to 1⁄2" in size.
The focal plane position has also been optimized so CCD
cameras will reach focus without any user modification to the
tube required.
Figure 2. To attach an Orion finder scope, an optional dovetail
holder is required.
Thumbscrew
Notch

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To use your CCD camera with the StarBlast, it must have a
1.25 inch “nosepiece”. All Orion StarShoot cameras have this
nosepiece (Figure 3). Due to the large amount of inward focus
travel required, however, digital SLRs equipped with a 1.25”
nosepiece (via T-ring connection) will not reach focus in the
StarBlast Imaging OTA.
First, acquire and center the object to be imaged with an
eyepiece. Then, remove the eyepiece and insert your CCD
camera into the telescope’s focuser. Secure the camera with
the thumbscrews on the focuser’s drawtube. Use the focus
knob to bring the image into focus.
Collimating the Optics
Collimating is the process of adjusting the mirrors so they are
aligned with one another.Your telescope’s optics were aligned
at the factory, and should not need much adjustment unless
the telescope is handled roughly. Accurate mirror alignment is
important to ensure peak performance of your telescope, so it
should be checked regularly. Collimating is relatively easy to
do and can be done in daylight.
To check optical alignment, remove the eyepiece and look
down the focuser drawtube. You should see the secondary
mirror centered in the drawtube, as well as the reflection of
the primary mirror centered in the secondary mirror, and the
reflection of the secondary mirror (and your eye) centered in
the reflection of the primary mirror, as in Figure 4a. If anything
is off-center, proceed with the following collimating proce-
dure.
The Collimating Cap and Primary Mirror Center Mark
Your StarBlast comes with a collimating cap. This is a simple
cap that fits on the focuser drawtube like a dust cap, but has a
hole in the center and a silver bottom. This helps center your
eye so collimating is easy to perform. Figures 4b through 4e
assume you have the collimating cap in place.
In addition to the collimating cap, you’ll notice a small ring
label on the exact center of the primary mirror. This “center
mark” allows you to achieve a very precise alignment of the
primary mirror; you don’t have to guess where the center of
the mirror is. You simply adjust the primary mirror position
(described below) until the reflection of the hole in the col-
limating cap is centered inside the ring.
Figure 3. To use a CCD camera with the StarBlast, the camera
must have a 1.25” nosepiece, like the Orion StarShoot Imaging
cameras.
1.25" nosepiece
drawtube
Reflection
of primary
mirror clip
Figure 4. Collimating the optics. (a) When the mirrors are properly aligned, the view down the focuser drawtube should look
like this. (b) With the collimation cap in place, if the optics are out of alignment, the view might look something like this. (c)
Here, the secondary mirror is centered under the focuser, but it needs to be adjusted (tilted) so that the entire primary mirror
is visible. (d) The secondary mirror is correctly aligned, but the primary mirror still needs adjustment. When the primary mirror
is correctly aligned, the “dot” will be centered, as in (e).
a.
b. c.
d. e.

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Note: The center ring sticker need not ever be removed from
the primary mirror. Because it lies directly in the shadow of the
secondary mirror, its presence in no way adversely affects the
optical performance of the telescope or the image quality. That
might seem counter-intuitive, but it’s true!
Aligning the Secondary Mirror
It helps to adjust the secondary mirror in a brightly lit room with
the telescope pointed toward a bright surface, such as white
paper or wall. Placing a piece of white paper in the telescope
tube opposite the focuser (i.e. behind the secondary mirror)
will also be helpful in collimating the secondary mirror.
With the collimating cap in place, look through the hole in the
cap at the secondary (diagonal) mirror. Ignore the reflections
for the time being. The secondary mirror itself should be cen-
tered in the focuser drawtube. If it isn’t, as in Figure 4b, it must
be adjusted. Typically, this adjustment will rarely, if ever, need
to be done.
Note: When make adjustments to the secondary mirror posi-
tion, be careful not to stress the spider vanes, or they may
bend.
To adjust the secondary mirror left-to-right in the focuser draw-
tube, use a 2.5mm hex key to loosen the three small alignment
setscrews in the center hub of the 4-vaned spider several
turns. Now hold the mirror holder stationary (be careful not to
touch the surface of the mirror), while turning the center screw
with a Phillips head screwdriver (Figure 5). Turning the screw
clockwise will move the secondary mirror toward the front
opening of the optical tube, while turning the screw counter-
clockwise will move the secondary mirror toward the primary
mirror. When the secondary mirror is centered left-to-right in
the focuser drawtube, rotate the secondary mirror holder until
the reflection of the primary mirror is as centered in the sec-
ondary mirror as possible. It may not be perfectly centered, but
that is OK for now. Tighten the three small alignment setscrews
equally to secure the secondary mirror in that position.
To adjust the secondary mirror up-and-down in the focuser
drawtube, adjust the length of the two spider vanes perpen-
dicular to the focuser. This is done by tightening the knurled
thumbnuts that secure the vanes to the tube (Figure 6). Loosen
one thumbnut, then tighten the other until the secondary mirror
is centered in the drawtube.
The secondary mirror should now be centered in the focuser
drawtube. Now we will shift our attention to the reflections with-
in the secondary mirror.
If the entire primary mirror reflection is not visible in the sec-
ondary mirror, as in Figure 4c, you will need to adjust the tilt
of the secondary mirror. This is done by alternately loosening
one of the three alignment setscrews while tightening the other
two, as depicted in Figure 7. You will need a 2mm hex key to
do this. The goal is to center the primary mirror reflection in the
secondary mirror, as in Figure 4d. Don’t worry that the reflec-
tion of the secondary mirror within the primary mirror reflection
(the smallest circle, with the collimation cap “dot” in the center)
is off-center. You will fix that in the next step.
Figure 5. To center the secondary mirror under the focuser, hold
the secondary mirror holder in place with your fingers while adjusting
the center screw with the Phillips head screwdriver. Do not touch the
mirror’s surface.
Figure 6. To center the secondary mirror up-and-down in the
focuser drawtube, make adjustments to the two knurled spider vane
thumbnuts that are perpendicular to the focuser.
Spider
vane
thumbnuts
Figure 7. Adjust the tilt of the secondary mirror by loosening one
of the three alignment set screws then tightening the other two.
Alignment set
screws (3)

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Once the secondary mirror is centered in the focuser draw-
tube, and the primary mirror reflection is centered in the
secondary mirror, the secondary mirror is properly aligned,
and no further adjustments to it should be needed.
Aligning the Primary Mirror
The final adjustment is made to the primary mirror. It will need
adjustment if, as in Figure 4d, the secondary mirror is cen-
tered in the focuser drawtube and the reflection of the primary
mirror is centered in the secondary mirror, but the small reflec-
tion of the secondary mirror (with the “dot” of the collimating
cap) is off-center.
The tilt of the primary mirror is adjusted with the three large
knurled thumbscrews on the rear end of the optical tube (back
of the mirror cell) (Figure 8). The small thumbscrews (with
slots in them) serve to lock the mirror in place. Start by loos-
ening each of these smaller thumbscrews a few turns. Use a
screwdriver in the slots, if necessary. Now adjust the tilt of the
primary mirror by turning one of the large thumbscrews either
clockwise or counterclockwise. Look into the focuser and see
if the secondary mirror reflection has moved closer to the
center of the primary mirror reflection. You can determine this
easily with the collimating cap and primary mirror center mark
by simply watching to see if the “dot” of the collimating cap is
moving closer or farther away from the “ring” on the primary
mirror. If it isn’t getting closer, try turning the thumbscrew in
the opposite direction. Repeat this process for the other two
large thumbscrews, if necessary. It will take a little trial-and-
error to get the feel for how to adjust the primary mirror to
center the dot of the collimating cap in the ring of the primary
mirror center mark.
When you have the dot centered as much as possible in the
ring, your primary mirror is aligned. The view through the colli-
mating cap should resemble Figure 4e. Make sure the smaller
thumbscrews on the back of the mirror cell are tightened to
lock the primary mirror in position.
A simple star test will tell you whether the optics are, in fact,
accurately aligned.
Star-Testing the Telescope
When it is dark, point the telescope at a bright star and accu-
rately center it in the eyepiece’s field of view. Slowly de-focus
the image with the focus knob. If the telescope’s optics are
correctly aligned, the expanding disk should be a perfect cir-
cle (Figure 9). If the image is unsymmetrical, the optics are
out of alignment. The dark shadow cast by the secondary mir-
ror should appear in the very center of the out-of-focus circle,
like the hole in a donut. If the “hole” appears off-center, the
optics are out of alignment.
If you try the star test and the bright star you have selected
is not accurately centered in the eyepiece, the telescope will
appear to need optical alignment, even though the optics may
be perfectly collimated. It is critical to keep the star centered,
so over time you will need to make slight corrections to the
telescope’s position in order to account for the sky’s apparent
motion.
Care & Maintenance
If you give your telescope reasonable care, it will last a life-
time. Store it in a clean, dry, dust-free place, safe from rapid
changes in temperature and humidity. Do not store the tele-
scope outdoors, although storage in a garage or shed is OK.
Small components like eyepieces and other accessories
should be kept in a protective box or storage case. Keep the
dust cover on the front of the telescope and the dust cap on
the focuser drawtube when it is not in use.
Your StarBlast requires very little mechanical maintenance.
The optical tube has a smooth painted finish that is fairly
scratch-resistant. If a scratch does appear on the tube, it will
not harm the telescope. If you wish, you may apply some auto
touch-up paint to the scratch. Smudges on the tube can be
wiped off with a soft cloth and household cleaning fluid.
Figure 8. The tilt of the primary mirror is adjusted by turning the
three larger thumbscrews.
Figure 9. A star test will determine if the telescope's optics
are properly collimated. A defocused view of a bright star through
the eyepiece should appear as illustrated on the right if optics are
perfectly collimated. If the circle is unsymmetrical, as illustrated on the
left, the scope needs alignment.
Out of collimation Collimated

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Cleaning Mirrors
You should not have to clean the telescope’s mirrors very often;
normally once every year or so is fine. Covering the front open-
ing of the telescope with the dust cover when it is not in use
will prevent dust from accumulating on the mirrors. Keeping
the dust cap on the focuser’s 1.25" opening is also a good
idea. Improper cleaning can scratch the mirror coatings, so the
fewer times you have to clean the mirrors, the better. Small
specks of dust or flecks of paint have virtually no effect on the
visual performance of the telescope.
The large primary mirror and the elliptical secondary mirror of
your telescope are front-surface aluminized and over-coated
with hard silicon dioxide, which prevents the aluminum from
oxidizing. These coatings normally last through many years of
use before requiring re-coating.
To clean the secondary mirror, first remove it from the telescope.
Do this by keeping the secondary mirror holder stationary while
completely unthreading the Phillips-head screw in the center
hub of the spider vane assembly (see Figure 5). Do not touch
the mirror surface when doing this. Be careful, there is a spring
between the secondary mirror holder and the Phillips head
screw; be sure it does not fall into the optical tube and onto the
primary mirror. Once the Phillips-head screw is unthreaded,
the secondary mirror and its holder can be removed from the
telescope. Then follow the same procedure described below
for cleaning the primary mirror. The secondary mirror does not
need to be removed from its holder for cleaning.
To clean the primary mirror, first carefully remove the mirror
cell from the telescope. For the StarBlast, you must completely
unthread the three screws on the exterior perimeter of the mir-
ror cell (Figure 10). Then pull the cell away from the tube. You
will notice the primary mirror is held in the mirror cell with three
clips held by two screws each. Loosen the screws and remove
the clips.
You may now remove the primary mirror from its cell. Do not
touch the surface of the mirror with your fingers. Lift the mirror
carefully by the edges. Set the mirror on a clean soft towel. Fill
a clean sink free with room temperature water, a few drops
of liquid dishwashing detergent, and if possible, a capfull of
100% isopropyl alcohol. Submerge the mirror (aluminized face
up) in the water and let it soak for a few minutes (or hours
if it’s a very dirty mirror). Wipe the mirror under water with
clean cotton balls, using extremely light pressure and strok-
ing in straight lines across the mirror surface. Use one ball
for each wipe across the mirror. Then rinse the mirror under
a stream of lukewarm water. Any particles on the surface can
be swabbed gently with a series of cotton balls, each used just
one time. Dry the mirror surface with a stream of air (a “blower
bulb” works great). Cover the mirror surface with tissue, and
leave the mirror in a warm area until it is completely dry before
replacing it in the mirror cell and telescope.
Specifications
Optical tube: Steel
Primary mirror: Parabolic, center marked
Aperture: 4.5" (114mm)
Effective focal length: 450mm
Focal ratio: f/3.9
Minor axis of secondary mirror: 1.85" (47.0mm)
Mirror coatings: Aluminum with silocon
dioxide (SiO2) overcoat
Focuser: Rack-and-pinion, accepts
1.25" eyepieces
Weight: 3.7 lbs.
Length: 17.25"
Figure 10. To remove the mirror cell from the telescope, the
three small Phillips-head screws on the perimeter of the mirror cell
must be completely unthreaded.
Small Phillips-head screws (3)

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One-Year Limited Warranty
This Orion StarBlast Imaging OTA is warranted against defects in materials or workmanship for a period
of one year from the date of purchase. This warranty is for the benefit of the original retail purchaser only.
During this warranty period Orion Telescopes & Binoculars will repair or replace, at Orion’s option, any
warranted instrument that proves to be defective, provided it is returned postage paid to: Orion Warranty
Repair, 89 Hangar Way, Watsonville, CA 95076. If the product is not registered, proof of purchase (such
as a copy of the original invoice) is required.
This warranty does not apply if, in Orion’s judgment, the instrument has been abused, mishandled, or
modified, nor does it apply to normal wear and tear. This warranty gives you specific legal rights, and
you may also have other rights, which vary from state to state. For further warranty service information,
contact: Customer Service Department, Orion Telescopes & Binoculars, 89 Hangar Way, Watsonville CA
95076; (800)-676-1343.
Orion Telescopes & Binoculars
89 Hangar Way, Watsonville, CA 95076
Customer Support Help Line (800)‑676‑1343 • Day or Evening