Celestron CGEM 925 manual

C C G G E E M M S S e e r r i i e e s s INSTRUCTION MANUAL C C G G E E M M 8 8 0 0 0 0 ● ● C C G G E E M M 9 9 2 2 5 5 ● ● C C G G E E M M 1 1 1 1 0 0 0 0[...]

2 INTRODUCTION ............ ............ ............ ............ ............ ............ ............ .................. ............ ............ ............ ............ ............ ............ ............ ............ ............ ..... 4 Warning........... .............. ....... .............. .............. .............. .............[...]

3 Home Position .............. ....... .............. .............. .............. .............. ....... .............. .............. .............. ....... .............. .............. .............. ...... 29 Light Control .............. .............. ....... .............. .............. .............. .............. ....... .............. [...]

4 Congratulations on your purchase of the Celestron CGEM Series telescope! The CGEM Series is made of the highest quality materials to ensure stability and durability. All this adds up to a telescope that gives you a lifetime of pleasure with a minimal amount of maintenance. Furthermore, your Celestron telescope is versatile — it will grow as you[...]

5 AS 1 Optical Tube 7 Tripod Center Leg Bra ce/Accessory Tra y 2 Telescope Mounting Pla tform 8 Counterweight(s) 3 Equatorial M ount 9 Counterweight Bar 4 Latitude Adjustment Knob 10 Azimuth Adjust ment Knob 5 Hand Control 11 Dovetail Mounting Ba r 6 Tripod 12 Schmidt Corrector Lens CONTROL PANEL C Hand Control Port A On/Off Sw itch D Aux Port B 12[...]

6 This section covers t he assembly instructions for your Celes tron Telescope. Your tele scope should be set up indo or the first time so that it is easy to identi fy the various par ts and familiarize yoursel f with the correct assembly proc edure before attempting it outdoor. #11097 #11098 #11099 CGEM 800 CGEM 925 CGEM 1100 Diameter 203mm (8&quo[...]

7 Before securing t he mount to the tripod as sho wn in Fig. 2-3: 1. Locate the Azi muth Adjustment Knobs fro m the box containing the CGEM mount. 2. Thread one knob into each of t he holes located o n either side of the mount. 3. Only thread the knobs abo ut half way in, lea ving enough space for the tripo d Alignment Pe g which will need to fit b[...]

8 A A t t t t a a c c h h i i n n g g t t h h e e A A c c c c e e s s s s o o r r y y T T r r a a y y 1. Slide the accessory tray over t he central rod so that each arm of the tra y is pushing against the inside of the tripod legs. 2. Thread the accessory tray kno b on to the ce ntral rod and tighten. I I n n s s t t a a l l l l i i n n g g t t h h[...]

9 A A t t t t a a c c h h i i n n g g t t h h e e H H a a n n d d C C o o n n t t r r o o l l H H o o l l d d e e r r The telescope com es with a hand control holder to place the computerized hand control. The hand control holder comes in two pieces: the leg clamp that snap s around the tripod leg and the holder which attaches to the leg clamp. To [...]

10 A A t t t t a a c c h h i i n n g g t t h h e e V V i i s s u u a a l l B B a a c c k k The visual bac k is the accesso ry that allows you to attach all visual accessories to the telesco pe. The telesco pe optical tubes come with the visual back installed . If it is not alread y on the tube it can be attached as follo ws: 1. Remove the rubber co[...]

11 I I n n s s t t a a l l l l i i n n g g t t h h e e F F i i n n d d e e r r s s c c o o p p e e The CGEM 800 and 925 telescop es come with a 6x30 finderscope used to help you locate and center o bjects in the main field of your telescop e. To accomplish this, the finder has a built -in cross-hair reticle that sho ws the optical center o f the fi[...]

12 3. Place the mounting bracket over the two holes of the rear cell as shown in the figure 2-10. 4. Insert the scre ws through the bracket and into t he rear cell. WARNING : If you remove the mounting bracket, do not completely thread the screws back into the rear cell of the telesco pe. The scre w s may be long enough to obstruct t he movement o [...]

13 2. Point your telescope at the objec t you selected and center it in the main op tics of the telescope. 3. Lock the azimuth a nd altitude clamps to hold the telescop e in place. 4. Check the finder to see where the obj ect is located in the field of view. 5. Adjust the thumb screws o n the finder bracket, until the cross hairs are centere d on t[...]

14 B B a a l l a a n n c c i i n n g g t t h h e e M M o o u u n n t t i i n n D D E E C C Although the telescope do es not track in declinatio n, the telescope should also b e balanced in this axis to pr event any sudd en motions when the DEC lock lever is loose. T o balance the telescope in DEC: 1. Loosen the R.A. cl utch lock lever and rotate th[...]

15 The latitude adjustment on the mount has a ra nge from approximately 15° to 70°. It is best to always make final adj ustments in latitude by moving the mount agains t gravity (i. e. using the rear latitude adjustment scre w to raise the mount). Adjusting the Mount in Azimuth For rough adjustments in azi muth, simply pick up the telescope and t[...]

16 All Celestron co mputerized telescope come with a hand control designed to give you instant access to all the functions that your telescope has to offer. With auto matic slewing to o ver 40,000 objects, and common sense menu descriptions, even a beginner can master its variet y of features in j ust a few observing sessions. B elow is a br ief de[...]

17 4. Catalog Keys: The hand con trol has keys on the hand control to allow direct access to each of the catalogs in its database. T he hand control contains the followin g catalogs in its database: Messier – Complete list of all Messier obj ects. NGC – Complete list of all the deep -sky objects in the Revi sed Ne w General Catalog. Caldwell ?[...]

18 the telescope will automaticall y slew to. One Star Align uses the same time/location information but only uses one star for alignment. Solar System Align will display a list of visible daytime objects (planets and the moon) available to align the telescope. Quick-Align will ask you to input all the same information as you would for the Auto Ali[...]

19  Select the ti me zone tha t you are ob serving fro m. Again, use the Up a nd Down buttons ( 10) to scroll thro ugh the choices. Refer to Ti me Zone map in Appendix for more infor mation. Date - Enter the mont h, day and year of your observing session. Select one of the alignment methods as described below. Note: If incorrect infor mation is [...]

20 O O n n e e S S t t a a r r A A l l i i g g n n One-Star Alignment works much the same way as T wo-Star Align but uses only a single star i n the sky for alignment. T his method of alignment is not as accurate as the t w o-star alignment and is reco mmended only for telescopes that are per man ently and a ccurately polar aligned. S S o o l l a a[...]

21 L L a a s s t t A A l l i i g g n n m m e e n n t t The Last Alignmen t method will auto matically recall the last stored index positio ns to continue using the align ment that was saved when the telescop e was last po wered do wn. T his is a useful fea ture should your tele scope accidentally lose p ower or be powered down. NOTE: Just like with[...]

22 Pressing any of the other catal og keys (M, C ALD, NGC, or STAR) will displa y a blinking c ursor belo w the name o f the catalog chosen. Use the nu meric ke y pad to enter the number o f any object w ithin these sta ndardized catalogs. For e xample, to find the Orion Nebula, pres s the "M" key and enter "042". Slewing to an [...]

23 Direction Buttons The hand control has four dir ection buttons (3) in the center of the hand contro l which control the telescope's motion in altitude (up and do wn) and azimuth (left and right). The telescop e can be controlled at nine d ifferent speed rate s. Rate Button Pressing the RATE key (11) allows you to instantly cha nge the speed[...]

24 Tracking Rate In addition to being able to move the telescope with the hand c ontrol buttons, your telesco pe will continually track a cele stial object as it moves across t he night sky. T he tracking rate can be changed depending on what t ype of object is being observed: Sidereal This rate compensates for the rotation of the Earth by moving t[...]

25 To replace the contents of any of the user defined objects, simply save a new object using one of the existing identification numbers; the telescope will re place the pr evious user defined obje ct with the current one. Get RA/DEC - Displays the r ight ascension and declinatio n for the current po sition of the telescope. Goto R.A/ Dec - Allows [...]

26 Anti-backlash – All mechanical gears have a certain amo unt of b acklash or play b etween the gears. This play is e vident b y how long it takes for a star to move in the eyepiece when the hand control arro w button s are pressed (especially when changing directions). The CGEM anti-backlash feat ures allows the user to compensate for backlash [...]

27 and clockwise (negative altitude) then make sure that the buttons used to center the alignment stars also move the telescope in the same d irections. Autoguide Rate – Allows the user to set an autoguide rate as a percentage of sidereal rate. This is helpful when calibrating your telescope to a CCD auto guider for long expo sure phot ography. O[...]

28 RA Limits - Sets the limits that the telescope can slew or track in Right Ascension (R.A.) before stopping. The slew limits are represented in degree s and by default set to 0º , being the position of the telescope when the counter weight bar is extended out horizontally. However, the slew limits can be custo mized depending on your needs. For [...]

29  R.A. switch - this proc edure records the offset error when the right ascension i ndex mark is alig ned at start-up. Calibrating the R. A. Index will improve the acc uracy of your initial star align ments when alig ning the telescope in the future.  GoTo Calibration – Goto Calibration is a useful to ol when attaching heav y visual or ph[...]

30 Scrolling Menu This menus allo ws you to change the rate of speed that the text scrolls across the ha nd contro l display.  Press the Up (number 6) button to increase t he speed of the text.  Press the Do wn (number 9) button to decr ease the speed of the text. Set Mount Position The Set Mount Position menu can be used to maintain your ali[...]

31 MENU TRACKING MODE RATE EQ NORTH EQ SOUTH SIDEREAL SOLAR LUNAR UTILITIES CALIBRATE MOUNT SCOPE SETUP VIEW TIME-SITE SETUP TIME - SITE HOME POSITION ANTI - BACKLASH FILTER LIMITS DIRECTION BUTTONS GOTO APPROACH AUTOGUIDE RA TES OTA ORIENTATION MERIDIAN LIGHTS CONTROL FACTORY SETTINGS VERSION GET AXIS POSITION GO TO AXI S POSITION HIBERNATE SUN ME[...]

32 Figure 4-1 A A c c u u t t a a w w a a y y v v i i e e w w o o f f t t h h e e l l i i g g h h t t p p a a t t h h o o f f t t h h e e S S c c h h m m i i d d t t - - C C a a s s s s e e g g r r a a i i n n o o p p t t i i c c a a l l d d e e s s i i g g n n Actual image orientation as seen with the unaided eye Inverted image, as viewed with the[...]

33 Figure 4-3 - The emblem on the end of the focus knob shows the correct rotational direction for focusing your telescope . Focusing The Schmidt-Cassegrain focusing mechanism controls the primary mirror which is mounted on a ring that slides back and forth on the primary baffle tube. The focusing knob, which moves the pri mary mirror, is on the re[...]

34 thousand yards. T he appare nt field of each eyepiece that Celestron manufactures is found in the Celestron Accessor y Catalog (#93685). General Observing Hints When working with any op tical instrument, there are a few things to re member to ensure you get t he best possible image.  Never look through window glass. Glass found in household w[...]

35 Up to this point, this manual covered the assembly and basic operation of your telescope. However, to understand your telescope more thoroughly, you need to know a little about the night sky. This section deals with o bservational astronom y in general and includes infor mation on the night s ky and polar alignment. The Celestial Coordinate Syst[...]

36 Motion of the Stars The daily motion of the Sun across the sky is familiar to even the most casual observe r. This daily trek is not the Sun moving as early astrono mers thought, but the result of the Earth's rotation. The Earth's rotation also causes the stars to do the same, scribi ng out a large circle as the Earth co mpletes one ro[...]

37 Latitude Scale Polar Aligning the Mount Latitude Scales The easiest way to polar align a telescope is with a latitude scale. Unlike other methods that require you to find the celestial pole by identifying certain star s near it, this method works off of a kno wn constant to dete rmine how high the polar axis should be pointed. T he CGEM mount ca[...]

38 2. Then accurately center the star in your e yepiece and press ALIGN. The telescope will then "sync" on this star and slew to the position that star should be if it were accuratel y polar aligned. 3. Use the mounts latitude and az imuth adjustme nts (see figure 2-15) to place the star in the center of the eyepiece . Do no t use the dir[...]

39 Polar Finderscope Cover Polar Axis Cover Figure 5-4 photography. This must be done in t he dark when Polaris is visible and can b e done usin g the hole in the polar axis or with the help of the optional polar a xis finderscope. See Optional Accessory section. 1. Set the telescope up so that t he po lar axis is pointing towards north (see fi gur[...]

40 With your telescop e set up, you are ready to use it for observing. This section covers visual observing hints for both solar system and deep sky obje cts as well as general o bserving conditions which will affect you r ability to observe. Observing the Moon Often, it is tempting to lo ok at the Moon when it is full. At t his ti me, the face we [...]

41 Solar Observing Hints  The best time to observe the S un is in the earl y morning or late afternoon whe n the air is co oler.  To center the Sun without loo king into the eyepiece, watch the shado w of the telescop e tube until it forms a circular shadow.  To ensure accurate tracking, b e sure to select t he solar tracking rate. Observi[...]

42 Figure 6-1 Seeing conditions d irectly affect image quality. These draw ings represent a point source (i.e., star ) under bad seeing c onditions (left) to e xcellent conditions ( right). Most often, seeing conditions produce i mages that lie some where between these two e xtremes.[...]

43 After lookin g at the night sky for a while you may want to try photograp hing it. Several forms of celestial photograp hy are possible with your telescope, including short exposure prime focus, eyepiece projection, long exposure deep sky, terrestrial and even CCD imagi ng. Each of these is discu ssed in moder ate detail with enough information [...]

44 1. Load your camera with film that ha s a moderate-to-fast speed (i.e., I SO rating). Faster films are more desirab le when t he Moon is a crescent. When the Moon is near full, and at its brightest, slower films are more desirable. Here are some film recommendations:  T-Max 100  T-Max 400  Any 100 to 4 00 ISO color slide film  Fuji S[...]

45 Because o f the high magnifica tions during eyepiece pr ojectio n, the field of view is q uite small which makes it d ifficult to find and center obj ects. T o make the job a little easier, ali gn the finder as acc urately as possible. T his allo ws you to get the object in the telescope's field based on the finder's view alo ne. Anoth[...]

46 Once you have mastered the technique, experiment with different films, different focal length eyepieces, and even differe nt filters. Long Exposure Prime Focus Photography This is the last form of celest ial photograph y to be attempted after others have been mastered. It is intended pri marily for deep sky obj ects, that is objects outside our [...]

47  3M 1000 (color slide)  Scotchchrome 400  T-Max 320 0 (black and white print)  T-Max 400 (black and white print) Periodic Error Correction (PEC) PEC for short, is a system that improves the tracking accuracy of the drive by reducin g the number of user corrections needed to keep a guide star centered in the eyepiece. PEC is designed [...]

48 7. Point the telescope at the obj ect you want to photograp h and center the guide star on the illuminated cross hairs and you are ready to play back the period ic error correction. 8. Once the drive 's periodic error has been recor ded, use the Play back function to begin playing back the corr ection for future photographic guiding. If you[...]

49 Another way to reduce vibratio n is with the Vibration Sup pression Pads (#9350 3). These pads rest between the ground and tripod feet. They reduce the vi bration a mplitude and vibration time. CCD Imaging SCT telescope's versatility allo ws it to be used in many different f-number configuration s for CCD imaging. It can be used at f/6.3 (w[...]

50 F F i i g g u u r r e e 8 8 - - 1 1 The three collimation scr ews are located on the front of the second ary mirror housing. While your telescope requires little maintenance, there are a few things to reme mber that will ensure your telescope performs at its best. Care and Cleaning of the Optics Occasionally, dust and/or moisture may build up on[...]

51 Figure 8-3 A collimated tele scope should appear symmetrical with the central obstruction centered in the star's diffraction pattern. Before you begin the collimation process, be sure that your telescope is in thermal equilibriu m with the surroundings. Allow 45 minutes for the telescope to reach equilibrium if you move it between large tem[...]

52 7. Once the star i mage is in the center of the field o f view, check to see if the rings are concen tric. If the central obstructio n is still skewed in the same direction, t hen continue tur ning the scre w(s) in the same direction. If you find that the r ing pattern is ske wed in a different direction, than si mply repea t steps 2 through 6 a[...]

53 You will find that additio nal accessories enhance your viewing pleasure and expand the usefulness of your telescope. For ease of ref erence, all the acce ssories are listed in alphabetical order. Barlow Lens - A Barlo w lens is a negative lens that increases the focal length of a telescop e. Used with any eyepiece, it doubles the magnification [...]

54 Series 2 – #94119-20 Deep Yello w , Red, Light Green, ND25% T (#s 1 2, 25, 56, 96ND-25) Series 3 – #94119-30 Light Red, Blue, Green, ND5 0% T (#s 23A, 38A, 58, 96ND-50) Series 4 – #94119-40 Yellow, Deep Yello w, Violet, Pale Blue (# s 8, 47, 82A, ND96 -13) Flashlight, Night Vision - (#93 588) - Celestron’s pre mium model for astronomy, u[...]

55 Reducer/Corrector (#94175) - This lens reduce s the focal length of the telescop e by 37%, making your C8-S a 1280 mm f/6.3 instrument. In addition, this unique lens also corrects inherent aberrations to produce crisp images all the way across the field when used visually. When used photographically, there is some vignetting that produces a 26mm[...]

56 Appendix A – Technical Specifications CGEM Series 11097 11098 11099 CGEM 800 CGEM 925 CGEM 1100 Specifications: Optical Design 203mm (8") Schmidt- Cassegrain 235mm (9.25") Schmidt- Cassegrain 280mm (11") Schmidt- Cassegrain Focal Length 2032mm F/10 2350mm F/10 2800mm F/10 Finderscope 6x30 6x30 9x50 Mount CGEM Computerized Equato[...]

57 Appendix B - Glossary of Terms A - Absolute magnitude The apparent magnitude that a star would have if it were observed from a sta ndard distance of 10 parsecs, or 32.6 light-years. The absolute magnitude of the Sun is 4.8. at a distance of 10 parsecs, it would just be visible on Earth on a clear moonless night away from surface light. Airy disk[...]

58 J - Jovian Planets Any of the four gas giant planets that are at a greater distance form the sun than the terrestrial planets. K - Kuiper Belt A region beyond the orbit of Neptune extending to about 1000 AU which is a source of many short period comets. L - Light-Year (LY) A light-year is the distance light traverses in a vacuum in one year at t[...]

59 telescope at this rate. The rate is 15 arc seconds per second or 15 degrees per hour. T - Terminator The boundary line between the light an d dark portion of the moon or a planet. U - Universe The totality of astronomical things, events, relations and energies capable of being described objectively. V - Variable Star A star whose brightness vari[...]

60 Appendix C - RS-232 Connecti on You can control your telescope with a computer via the RS-232 port on the computerized hand control and using a n optional RS-232 cable (#93920). Once co nnected, the telescope can b e controlled using popular astronomy software programs. Communication Prot ocol: The CGEM Mount communic ates at 9600 bits/sec, No p[...]

61 Additional RS232 Co mmands S S e e n n d d A A n n y y T T r r a a c c k k R R a a t t e e T T h h r r o o u u g g h h R R S S 2 2 3 3 2 2 T T o o T T h h e e H H a a n n d d C C o o n n t t r r o o l l 1. Multiply the desired tracking rate (arcseco nds/second) by 4. Example: if the d esired trackrate is 150 arcseconds/second, then TR ACKRATE = [...]

62 A PPENDIX D – MAPS OF TIME ZONES[...]

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CELESTRON TWO YEAR WAR RANTY A. Celestron warrants this telescope to be free from defects in materials and workmanship for two years. Celestron will r epair or replace such product or part there of which, upon inspection by Celestron, is found to b e defective in materials or workmanship. As a condition to the obligation of Celestron to repair or r[...]

Celestron 2835 Columbia Street Torrance, CA 90503 U .S.A. Tel. (310) 328-9560 Fax. (310) 212-5835 Web site at http//www.celestro n.com Copyright 2008 Celestron All rights reserved. (Products or instructions may change without notice or obligation.) Item # 11097-INST $10.00 11-08 - Rev2[...]