Specifications
Optical Design
Rowe-Ackermann Schmidt
Aperture
355.6 mm
Focal Length
790 mm
Focal Ratio
f/2.2
Central Obstruction
158 mm (44% of aperture diameter)
Optical Coatings
Enhanced aluminum, Starbright XLT multi-coatings
Optical Window
104 mm Ø, removeable
Focuser
New focuser design, minimizes focus shift
Cooling Fan
12V DC, MagLev
Tube Dimensions
42.5 inches length, 16 inches diameter
Tube Weight
75 lbs
Back focus (from top of lens group housing)
77.5 mm
Back focus (with M48 camera adapter)
55 mm
Spot size
< 6.3 μm RMS across FOV
Wavelength Range
400 – 900 nm
Off-axis Illumination
83% at 30 mm off-axis
Image Circle
60.1 mm Ø , 4.3 degrees
Usable Field
70 mm Ø, 5.1°, only minimal performance loss at edge of FOV
Telescope Instruction Manual
Model: 91077
CELESTRON TWO YEAR LIMITED WARRANTY
A
. Celestron warrants your telescope mount 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 telescope mount 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 telescope.
If warranty problems arise, or if you need assistance in using your telescope mount 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 • 04-18
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.
5
. Inspect the defocused star pattern. When collimated, the pattern should look like a
concentric doughnut. If the pattern is concentric, no adjustment is necessary. If the
“donut hole” is not centered within the pattern, then some adjustment is needed.
6
. There are three pairs of collimation screws. Each pair works together as a push-pull tilt
adjustment. 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 star pattern is thin on one side, adjust the collimation screws so that 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.
3 mm
Hex key
2 mm
Hex key
