Specifications
Optical Design Rowe-Ackermann Schmidt Tube Dimensions 24.7” length, 9.3” diameter
Aperture 203 mm Tube Weight 17 lbs
Focal Length 400 mm
Back focus
(from top of lens group housing)
29 mm
Focal Ratio f/2.0
Back focus
(with M42 camera adapter)
25 mm
Central Obstruction 93 mm (46% of aperture diameter) Spot size < 4.6 μm RMS across FOV
Optical Coatings
Enhanced aluminum,
Starbright XLT multi-coatings
Wavelength Range 400 – 800 nm
Optical Window 46 mm Ø, removeable Off-axis Illumination 93% at 11 mm off-axis
Focuser Ultra-Stable Focus System Image Circle 22.0 mm Ø , 3.15°
Cooling Fan 12V DC, MagLev Usable Field
32.0 mm Ø, 4.6°, only minimal performance loss
at edge of FOV
Telescope Instruction Manual
Model: 91073
CELESTRON TWO YEAR LIMITED WARRANTY
A. Celestron warrants this product to be free from defects in materials and workmanship for two years. Celestron
will repair or replace such product or part thereof which, upon inspection by Celestron, is found to be defective in
materials or workmanship. As a condition to the obligation of Celestron to repair or replace such product, the product
must be returned to Celestron together with proof-of-purchase satisfactory to Celestron.
B. The Proper Return Authorization Number must be obtained from Celestron in advance of return. Call Celestron at
(310) 328-9560 to receive the number to be displayed on the outside of your shipping container.
All returns must be accompanied by a written statement setting forth the name, address, and daytime telephone
number of the owner, together with a brief description of any claimed defects. Parts or product for which replacement
is made shall become the property of Celestron.
The customer shall be responsible for all costs of transportation and insurance, both to and from the factory of
Celestron, and shall be required to prepay such costs.
Celestron shall use reasonable efforts to repair or replace any product covered by this warranty within thirty
days of receipt. In the event repair or replacement shall require more than thirty days, Celestron shall notify the
customer accordingly. Celestron reserves the right to replace any product which has been discontinued from its
product line with a new product of comparable value and function.
This warranty shall be void and of no force of effect in the event a covered product has been modified in design
or function, or subjected to abuse, misuse, mishandling or unauthorized repair. Further, product malfunction or
deterioration due to normal wear is not covered by this warranty.
CELESTRON DISCLAIMS ANY WARRANTIES, EXPRESS OR IMPLIED, WHETHER OF MERCHANTABILITY OF
FITNESS FOR A PARTICULAR USE, EXCEPT AS EXPRESSLY SET FORTH HEREIN. THE SOLE OBLIGATION OF
CELESTRON UNDER THIS LIMITED WARRANTY SHALL BE TO REPAIR OR REPLACE THE COVERED PRODUCT, IN
ACCORDANCE WITH THE TERMS SET FORTH HEREIN. CELESTRON EXPRESSLY DISCLAIMS ANY LOST PROFITS,
GENERAL, SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES WHICH MAY RESULT FROM BREACH OF ANY
WARRANTY, OR ARISING OUT OF THE USE OR INABILITY TO USE ANY CELESTRON PRODUCT. ANY WARRANTIES
WHICH ARE IMPLIED AND WHICH CANNOT BE DISCLAIMED SHALL BE LIMITED IN DURATION TO A TERM OF TWO
YEARS FROM THE DATE OF ORIGINAL RETAIL PURCHASE.
Some states do not allow the exclusion or limitation of incidental or consequential damages or limitation on how long
an implied warranty lasts, so the above limitations and exclusions may not apply to you.
This warranty gives you specific legal rights, and you may also have other rights which vary from state to state.
Celestron reserves the right to modify or discontinue, without prior notice to you, any model or style product.
If warranty problems arise, or if you need assistance in using your product contact:
CELESTRON, LLC. Customer Service Department
2835 Columbia Street • Torrance, CA 90503 • Tel. 800.421.9649
Monday-Friday 8AM-4PM PST • ©2018 Celestron • All rights reserved • 10-18
NOTE: This warranty is valid to U.S.A. and Canadian customers who have purchased this product from an authorized
Celestron dealer in the U.S.A. or Canada. Warranty outside the U.S.A. and Canada is valid only to customers who
purchased from a Celestron’s International Distributor or Authorized Celestron Dealer in the specific country. Please
contact them for any warranty service.
FCC NOTE: This equipment has been tested and found
to comply with the limits for a Class B digital device, pursuant
to part 15 of the FCC Rules. These limits are designed to
provide reasonable protection against harmful interference in
a residential installation. This equipment generates, uses, and
can radiate radio frequency energy and, if not installed and used in accordance with the instructions,
may cause harmful interference to radio communications. However, there is no guarantee that
interference will not occur in a particular ninstallation. If this equipment does cause harmful interference
to radio or television reception, which can be determined by turning the equipment off and on,
the user is encouraged to try to correct the interference by one or more of the following measures:
• Reorient or relocate the receiving antenna.
• Increase the separation between the equipment and receiver.
• Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
• Consult the dealer or an experienced radio/TV technician for help.
This product is designed and intended for use by those 14 years of age and older.
3. Point the astrograph at a bright star and focus the camera. Center the star in the camera’s
field of view.
4. Defocus the star by about one turn of the focus knob.
5. Inspect the defocused star diffraction pattern. When collimated, the pattern should look like a
concentric donut. If the pattern is concentric, no adjustment is necessary. If the “donut hole” is
not centered within the pattern, then some adjustment is needed.
OUT-OF-FOCUS STAR IMAGE FOR COLLIMATED TELESCOPE
6. There are three pairs of collimation screws. Each pair works together as a push-pull tilt adjustment.
Using the hex keys, adjust the collimation by loosening and tightening one of the pairs of collimation
screws. Always loosen one of the screws first, then tighten the other one. Adjust one pair of
screws at a time.
7. If the defocused star pattern is thin on one side, adjust the collimation screws so the star moves
towards the thin side, then adjust the position of the astrograph to re-center the star. Repeat this
until the defocused star image is concentric.
OUT-OF-FOCUS STAR IMAGES FOR TELESCOPE NEEDING COLLIMATION
2.0
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