Manual Celestron Rowe-Ackermann Schmidt Astrograph

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Speciﬁcations

Optical Design Rowe-Ackermann Schmidt

Aperture 279 mm

Focal Length 620 mm

Focal Ratio 2.22

Central obstruction diameter 114 mm

Optical Coatings StarBright XLT

Total Telescope Kit Weight 35 lbs

Optical Window Broadband AR fully-multicoated removable optical window

Focuser FeatherTouch MicroFocuser, 10:1 ﬁne focus ratio

Cooling Fan 12V DC, tip positive polarity

Optical Tube Length 33 in

Backfocus from included camera adapters 55 mm

Total back focus from ﬂat surface above optical window 72.8 mm

On-axis RMS spot size <2.00 µm

RMS spot size 21 mm off-axis <2.25 µm

Relative illumination 21 mm off-axis 83%

Optimized Image Circle Diameter 43.3 mm

Total Usable Field 52 mm

Rowe-Ackermann Schmidt Astrograph

Telescope

INSTRUCTION MANUAL

Model: 91075

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 de-

sign 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

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.

Dew Prevention

The Schmidt corrector is especially susceptible to condensation forming because the glass is

immediately exposed to the outside air, just like the windshield on your car. If the temperature

outside drops below the dew point, dew may form on the corrector within minutes.

The easiest way to prevent dew is to add an optional dew shield, available from Celestron,

which shrouds the corrector and keeps the air immediately surrounding the corrector slightly

warmer than the ambient temperature. If conditions are more severe, a dew heater, commonly

available from other manufacturers, can be added to apply slight heat to the corrector lens to

keep it dry all night.

If dew has already formed on the corrector, point the telescope downward and allow the

telescope to dry. You can also use a hairdryer to heat the corrector and evaporate the moisture

to dry the telescope.

Dew does not harm the telescope, but can lead to faster dust build up. Do not store the

telescope if covered in dew. Allow the telescope to dry ﬁrst.

Care and Cleaning of the Optics

Dust should normally be removed with a pressured air can, or a camel hair brush. Spray at an

angle to the lens for approximately two to four seconds. Then, use an optical cleaning solution

and white tissue paper to remove any remaining debris. Apply the solution to the tissue and

then apply the tissue paper to the lens. Low pressure strokes should go from the center of the

corrector to the outer portion. Do NOT rub in circles!

You can use a commercially made lens cleaner or mix your own. A good cleaning solution is

isopropyl alcohol mixed with distilled water. The solution should be 60% isopropyl alcohol and

40% distilled water. Or, liquid dish soap diluted with water (a couple of drops per one quart of

water) can be used.

To minimize the need to clean your telescope, replace the dust cap once you have ﬁnished

using it.

Internal adjustments and cleaning should be done only by the Celestron repair department. If

your telescope is in need of internal cleaning, please call the factory for a return authorization

number and price quote.

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Celestron Rowe-Ackermann Schmidt Astrograph - 91075 Manual

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