Orion Schmidt-Cassegrain Telescopes 8", 9.25", & 11" User's Manual
Contents
1. in positions that are physically more comfortable than if you looked straight through the scope To insert a star diagonal 1 Turn the set screw on the visual back until its tip no lon ger extends into i e obstructs the inner diameter of the visual back Figure 1 Cutaway view of the light path of the Schmidt Cassegrain optical design Attaching the Visual Back The visual back is the accessory that allows you to attach all visual accessories to the telescope The optical tube should 2 Slide the chrome portion of the star diagonal into the visu al back Tighten the set screw on the visual back to hold the star diag onal in place Finder scope come with the visual back installed If it is not already on the tube it can be attached as follows Finder scope bracket Visual back Dovetail finder scope base 1 Remove the rubber cover on the rear cell isual bac 2 Place the knurled slip ring on the visual back over the threads on the rear cell Fig 2 3 Hold the visual back with the set screw in a convenient position and rotate the knurled slip ring clockwise until tight Once this is done you are ready to attach other accessories such as a diagonal prism and eyepiece Diagonal To remove the visual back rotate the slip ring counterclock wise until it is free of the rear cell Focus knob Figure 2 Rear cell A onenerser Orion ozs scr Orion 11 SCT Inserting an Eyep2. in collimating the optics Orion Two Year Limited Warranty Orion warrants this telescope to be free from defects in materials and workmanship for two years Orion will repair or replace such product or part thereof which upon inspection by Orion is found to be defec tive in materials or workmanship As a condition to the obligation of Orion to repair or replace such prod uct the product must be returned to Orion together with proof of purchase satisfactory to Orion The Proper Return Authorization Number must be obtained from Orion in advance of return Call 800 676 1343 to receive the number to be displayed on the outside of your shipping container Items should be sent to Orion Warranty Repair 89 Hangar Way Watsonville CA 95076 This warranty is for the benefit of the original retail purchaser only 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 Orion and shall be required to prepay such costs Orion shall use reasonable efforts to repair or replace any telescope covered by this warranty within thirty days of receipt In the event repair or replacement shall require more than thirty days Orion shall notify the cu
3. 5 to the telescope Line up the through holes in the base with the threaded holes in the rear cell of the telescope tube Then insert the two supplied screws through the base and thread them into the telescope holes until secure Figure 3a Now you re ready to attach the finder scope 2 Unthread the two black nylon thumbscrews until the ends are flush with the inside of the bracket Figure 3b Remove the O ring from the foot of the bracket and slide it over the back of the finder it will NOT fit over the objective end of the finder It may need to be stretched a little Slide it until it seats into the slot in the middle of the finder tube 3 Slide the eyepiece end narrow end of the finder scope into the end of the bracket s cylinder opposite the align ment screws while pulling the chrome spring loaded ten sioner pin on the bracket with your fingers Figure 3c Push the finder scope through the bracket until the O ring seats just inside the front opening of the bracket cylinder Release the tensioner pin and tighten the two black nylon thumbscrews a couple of turns each to secure the finder scope in place 4 Now insert the foot of the finder scope bracket into the dovetail base Lock the bracket into position by tightening the knurled thumbscrew on the dovetail holder Aligning the Finder Scope Accurate alignment of the finder scope makes it easy to find objects with the telescope especially celestial objects To make a
4. INSTRUCTION MANUAL Orion Schmidt Cassegrain Telescopes 8 9 25 amp 11 Customer Support 800 676 1343 gt ORIO IN E mail support telescope com TELESCOPES amp BINOCULARS Corporate Offices 831 763 7000 Providing Exceptional Consumer Optical Products Since 1975 PO Box 1815 Santa Cruz CA 95061 IN 265 Rev A 8 05 Congratulations on your purchase of an Orion Schmidt Cassegrain telescope The Schmidt Cassegrain opti cal system uses a combination of mirrors and lenses and is referred to as a compound or catadioptric telescope This unique design offers large diameter optics while maintaining very short tube lengths making them extremely portable and versatile The Schmidt Cassegrain system consists of a zero power corrector plate a spherical primary mirror and a secondary mirror Once light rays enter the optical system they travel the length of the optical tube three times exiting through a hole in the center of the primary mirror to the eyepiece Orion brand Schmidt Cassegrain tube assemblies are made by Celestron International in the U S A The optics feature Starbright XLT coatings enhanced multi layer coatings on the primary and secondary mirrors for increased reflectivity and a fully coated corrector for the finest anti reflection characteristics fl Inserting a Star Diagonal A star diagonal is a prism that diverts the light at a right angle to the light path of the telescope This allows you to observe
5. corrector plate pointing toward the collimation screws The shadow of your finger should be visible when looking into the eyepiece Rotate your finger around the tube edge until its shadow is seen closest to the narrowest portion of the rings i e the same direction in which the central shadow is skewed 3 Locate the collimation screw closest to where your finger is positioned This will be the collimation screw you will need to adjust first If your finger is positioned exactly between two of the collimation screws then you will need to adjust the screw opposite where your finger is located 4 Use the hand control buttons to move the de focused star image to the edge of the field of view in the same direction that the central obstruction of the star image is skewed 5 While looking through the eyepiece use an Allen wrench to turn the collimation screw you located in steps 2 and 3 Usually a tenth of a turn is enough to notice a change in collimation If the star image moves out of the field of view in the direction that the central shadow is skewed then you are turning the collimation screw the wrong way Turn the screw in the opposite direction so that the star image is moving toward the center of the field of view Figure 8 In a well collimated telescope a defocused star image should appear symmetrical with the dark central obstruction centered in the stars ring pattern Warning The secondary mirror should never be r
6. e accessories from the rear cell of the telescope Place the telescope in a dust free environment and point it down This will remove the moisture from the telescope tube To minimize the need to clean your telescope replace all lens covers once you have finished using it Since the rear cell is NOT sealed the cover should be placed over the opening when not in use This will prevent contaminants from entering the optical tube Internal adjustments and cleaning should be done only by an authorized repair department If your telescope is in need of internal cleaning please call Orion for a return authorization number and price quote Collimation screws Figure 6 The three collimation screws are located on the front of the secondary mirror housing Collimation The optical performance of your telescope is directly related to its collimation that is the alignment of its optical system Your telescope was collimated at the factory after it was completely assembled However if the telescope is dropped or jarred severely during transport it may have to be re collimated The only optical element that can be adjusted is the secondary mirror To check the collimation of your telescope you will need a light source A bright star near the zenith is ideal since there is a minimal amount of atmospheric distortion Make sure that tracking is on so that you won t have to manually track the star Figure 7 Even though the star patter
7. emoved Adjustments to collimation can easily be made by turning the screws on the secondary mirror mount without ever having to remove the secondary mirror 6 If while turning you notice that the screws get very loose then simply tighten the other two screws by the same amount Conversely if a collimation screw gets too tight then loosen the other two screws by the same amount 7 Once the star image is in the center of the field of view check to see if the rings are concentric lf the central obstruction is still skewed in the same direction then con tinue turning the screw s in the same direction If you find that the ring pattern is skewed in a different direction then simply repeat steps 2 through 6 as described above for the new direction Perfect collimation will yield a ring pattern that s symmetrical just inside and outside of focus Figure 8 Well collimated optics deliver the optimal performance specifications that your telescope is built to achieve If seeing i e air steadiness is turbulent collimation is dif ficult to judge If stars are twinkling that s a tipoff that the see ing is bad In that case you might want to wait for a night with better seeing i e when stars aren t twinkling to perform the collimation procedure or you could try pointing the telescope to a part of the sky that appears to have steadier air Note Laser collimators will not work with Schmidt Cassegrains and should not be used
8. iece An eyepiece magnifies the image focused by the telescope The eyepiece fits into either the visual back directly or the star diagonal To install an eyepiece 1 Loosen the set screw on the star diagonal until the tip no longer extends into the inner diameter of the eyepiece end of the diagonal 2 Slide the chrome portion of the eyepiece into the star diag onal 3 Tighten the set screw on the star diagonal to hold the eye piece in place To remove the eyepiece loosen the setscrew on the star diagonal and slide the eyepiece out You can replace it with another eyepiece purchased separately Eyepieces are commonly referred to by focal length and bar rel diameter The focal length of each eyepiece is printed on the eyepiece barrel The longer the focal length i e the larger the number the lower the eyepiece magnification the shorter the focal length i e the smaller the number the higher the magnification Generally you will use low to moderate pow ers when viewing For more information on how to determine power see the section on Calculating Magnification Attaching a Finder Scope A finder scope is a small wide field telescope used to help locate and center objects in the field of your main telescope The finder scope has a built in crosshair reticle that shows the optical center of the finder s field of view 1 To install an Orion finder scope you must first attach a dovetail finder scope base 721
9. ligning the finder as easy as possible this proce dure should be done in the daytime when it is easy to find and identify objects The finder scope has two perpendicular adjustment screws and a spring loaded pin that allow easy adjustment of the finder scope horizontally and vertically To align the finder Figure 3a Attaching the optional dovetail finder scope base Alignment Padus thumbscrews Su Eyepiece lock ring N Objective lens lt Tensioner lt Finder scope bracket lt Dovetail foot Figure 3b The Orion 6x30 finder scope Figure 3c Pull the spring loaded tensioner outward then insert the finder scope into the finder scope bracket 1 Choose a target that is in excess of one mile away This eliminates any possible parallax effect between the tele scope and finder 2 Release the altitude and azimuth clamps of your telescope mount and point the telescope at your target 3 Center your target in the main optics of the telescope You may have to move the telescope slightly to center it 4 Now look in the finder scope Is the object visible Ideally it will be somewhere in the field of view If not some coarse adjustment to the finder scope bracket s alignment thumb screws will be needed until the object comes into the finder scope s field of view 5 With the image in the finder scope s field of view adjust the alignment thumbscrews one at a time to ce
10. n appears the same on both sides of focus it is asymmetric The dark obstruction is skewed off to the left side of the diffraction pattern indicating poor collimation Or if you do not want to power up your telescope you can use Polaris Its position relative to the celestial pole moves very little thus eliminating the need to manually track it Before you begin the collimation process be sure that your telescope is in thermal equilibrium with the surroundings Allow 45 minutes for the telescope to reach equilibrium if you move it between large temperature extremes Use a medium to high power ocular something in the range of 12mm to 6mm focal length It is important to position a star in the center of the field of view to judge collimation Slowly cross in and out of focus and judge the symmetry of the star If you see a systematic skewing of the star to one side then recol limation is needed To accomplish this you will need to adjust the secondary mir ror collimation screw s located on the secondary mirror holder see Figure 6 To make collimation a simple procedure follow these easy steps 1 While looking through a medium to high power eyepiece center a bright star in the field of view then de focus it until a ring pattern with a dark shadow appears see Figure 7 Notice in which direction the central shadow is skewed 2 Place your finger along the edge of the front cell of the tele scope be careful not to touch the
11. nter the object on the intersection of the crosshairs Focusing the Finder Scope If when you look through the finder scope the images appear somewhat out of focus you will need to refocus the finder scope for your eyes 1 Loosen the lock ring located behind the objective lens cell on the body of the finder scope see Figure 3b 2 Back the lock ring off by a few turns for now Refocus the finder scope on a distant object by threading the objective lens cell in or out of the finder scope body Precise focusing will be achieved by focusing the finder scope on a bright star 3 Once the image appears sharp retighten the locking ring behind the objective lens cell The finder scope s focus should not need to be adjusted again Image orientation through the finder scope is upside down This is normal for any finder that is used straight through Because of this it may take a few minutes to familiarize yourself with the directional change each screw makes on the finder Focusing the Telescope The Schmidt Cassegrain focusing mechanism con trols the primary mirror which is mounted on a ring that slides back and forth on the primary baffle tube The focusing knob which ec moves the primary mirror is on the rear cell of the telescope To focus turn the focusing knob until the image is sharp If the knob will not turn it has reached the end of its travel on the focusing mechanism Turn the knob in the opposite direction
12. stomer accordingly Orion 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 ORION DISCLAIMS ANY WARRANTIES EXPRESS OR IMPLIED WHETHER OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE EXCEPT AS EXPRESSLY SET FORTH HEREIN THE SOLE OBLIGATION OF ORION UNDER THIS LIMITED WARRANTY SHALL BE TO REPAIR OR REPLACE THE COVERED PRODUCT IN ACCORDANCE WITH THE TERMS SET FORTH HEREIN ORION 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 Orion reserves
13. t to right i e inverted This is nor mal for the Schmidt Cassegrain design 2089837 alijo ny ES arica wr K 302 a Chaa a r but no diagonal image in telescope is inverted l Normal image orientation as seen with unaided eye With star diagonal image in telescope is reversed Figure 5 Image orientation in Schmidt Cassegrains Calculating Magnification You can change the magnifying power of your telescope by changing the eyepiece ocular To determine the magnifica tion of your telescope simply divide the focal length of the tele scope by the focal length of the eyepiece used In equation format the formula looks like this Telescope Focal Length mm TOSCO TOFA ens niin Magnification Eyepiece Focal Length mm For example if you are using a 26mm eyepiece in the 8 Schmidt Cassegrain divide the focal length of the telescope 2032mm by the focal length of the eyepiece 26mm That yields a magnification of 78 Although the power is variable each instrument has a limit to how much it can practically achieve The general rule is 60x magnification per inch of aperture So an 8 aperture telescope can achieve a maximum useful magnification of 480 power This level of magnification assumes you have ideal conditions for viewing however The clearest sharpest views will always be achieved at lower powers Keep in mind that as you increase magnification the bright ness of the object
14. the right to modify or discontinue without prior notice to you any model or style of telescope If warranty problems arise or if you need assistance in using your telescope contact Orion Telescopes amp Binoculars Customer Service Department 89 Hangar Way Watsonville CA 95076 800 676 1343 This warranty supersedes all other product warranties Orion Telescopes amp Binoculars Post Office Box 1815 Santa Cruz CA 95061 Customer Support Help Line 800 676 1343
15. until the image Foc Figure 4 The emblem on the end of the focus knob shows the correct rotation direction for focusing your telescope is sharp Once an image is in focus turn the knob clockwise to focus on a closer object and counterclockwise for a more distant object A single turn of the focusing knob moves the primary mirror only slightly Therefore it will take many turns about 30 to go from close focus to infinity For astronomical viewing out of focus star images are very diffuse making them difficult to see If you turn the focus knob too quickly you can go right through focus without seeing the image To avoid this problem your first astronomical target should be a bright object like the Moon or a planet so that the image is visible even when out of focus Critical focus ing is best accomplished when the focusing knob is turned in such a manner that the mirror moves against the pull of grav ity In doing so any mirror shift is minimized For astronomical observing both visually and photographically this is done by turning the focus knob counterclockwise Image Orientation The image orientation changes depending on how the eye piece is inserted into the telescope When using a star diago nal the image is right side up but reversed from left to right i e mirror image If inserting an eyepiece directly into the visual back i e without a star diagonal the image is upside down and reversed from lef
16. viewed will decrease this is an inherent principle of the laws of physics and cannot be avoided If mag nification is doubled an image appears four times dimmer If magnification is tripled image brightness is reduced by a fac tor of nine The F number of a telescope stands for the ratio between the focal length and the diameter of the light gathering element The 8 Schmidt Cassegrain optical tube has a focal length of 80 inches and a diameter of 8 inches This makes the system an f 10 focal length divided by diameter An optional focal reducer is available to reduce the effective focal ratio to f 6 3 Determining the Field of View Determining the field of view is important if you want to get an idea of the angular size of the object you are observing To calculate the actual field of view divide the apparent field of the eyepiece supplied by the eyepiece manufacturer by the magnification In equation format the formula looks like this Apparent Field of Eyepiece AP A True Field Magnification As you can see before determining the field of view you must calculate the magnification Using the example in the previous section we can determine the field of view using the same 26mm eyepiece A 26mm Pl ssl eyepiece has an apparent field of view of 52 Divide 52 by the magnification which is 78 This yields an actual field of 1 5 To convert degrees to feet at 1 000 yards which is more useful for terrestrial obser
17. ving simply multiply by 52 5 Continuing with our example multiply the angular field 1 5 by 52 5 This produces a linear field width of 78 8 feet at a distance of 1 000 yards Care and Cleaning of the Optics Occasionally dust and or moisture may build up on the correc tor plate of your telescope Special care should be taken when cleaning any instrument so as not to damage the optics If dust has built up on the corrector plate remove it with a brush made of camel s hair or a blower bulb Then use an optical cleaning solution and white tissue paper to remove any remaining debris Apply the solution to the tissue not to the glass and then apply the tissue paper to the lens Low pres sure 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 Occasionally you may experience dew build up on the correc tor plate of your telescope during an observing session If you want to continue observing the dew must be removed either with a hair dryer on low setting or by pointing the telescope at the ground until the dew has evaporated If moisture condenses on the inside of the corrector remove th
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