CGEM Series INSTRUCTION MANUAL CGEM 800 ● CGEM 925 ● CGEM 1100
INTRODUCTION....................................................................................................................................................................................................................... 4 Warning.......................................................................................................................................................................................................... 4 ASSEMBLY.............................................................
Home Position ..................................................................................................................................................................................... 29 Light Control ....................................................................................................................................................................................... 29 Factory Settings................................................................................................
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 your interest grows. The CGEM Series ushers in the next generation of computer automated telescopes.
AS Figure 2.
This section covers the assembly instructions for your Celestron Telescope. Your telescope should be set up indoor the first time so that it is easy to identify the various parts and familiarize yourself with the correct assembly procedure before attempting it outdoor. Diameter Focal Length Eyepiece Finderscope Diagonal Mount Tripod Software Counterweights #11097 CGEM 800 #11098 CGEM 925 #11099 CGEM 1100 203mm (8") SchmidtCassegrain 2032mm F/10 25mm - 1.25" (81x) 6x30 90° - 1.
Before securing the mount to the tripod as shown in Fig. 2-3: 1. 2. 3. Locate the Azimuth Adjustment Knobs from the box containing the CGEM mount. Thread one knob into each of the holes located on either side of the mount. Only thread the knobs about half way in, leaving enough space for the tripod Alignment Peg which will need to fit between the screw tips.
Attaching the Accessory Tray 1. 2. Slide the accessory tray over the central rod so that each arm of the tray is pushing against the inside of the tripod legs. Thread the accessory tray knob on to the central rod and tighten. Installing the Counterweight Bar To properly balance the telescope, the mount comes with a counterweight bar and at least one counterweight (depending on model). To install the counterweight bar: 1.
Attaching the Hand Control Holder The telescope comes with a hand control holder to place the computerized hand control. The hand control holder comes in two pieces: the leg clamp that snaps around the tripod leg and the holder which attaches to the leg clamp. To attach the hand control holder: 1. 2. Place the leg clamp up against one of the tripod legs and press firmly until the clamp wraps around the leg.
Attaching the Visual Back The visual back is the accessory that allows you to attach all visual accessories to the telescope. The telescope optical tubes come with the visual back installed. If it is not already on the tube it can be attached as follows: 1. Remove the rubber cover on the rear cell. 2. Place the knurled slip ring on the visual back over the threads on the rear cell (Fig 2-8). 3.
Installing the Finderscope The CGEM 800 and 925 telescopes come with a 6x30 finderscope used to help you locate and center objects in the main field of your telescope. To accomplish this, the finder has a built-in cross-hair reticle that shows the optical center of the finderscope. The CGEM 1100 comes with a 9x50 finderscope. Start by removing the finder and hardware from the plastic wrapper.
3. 4. Place the mounting bracket over the two holes of the rear cell as shown in the figure 2-10. Insert the screws through the bracket and into the rear cell. Figure 2-10 WARNING: If you remove the mounting bracket, do not completely thread the screws back into the rear cell of the telescope. The screws may be long enough to obstruct the movement of, and possibly damage the primary mirror.
2. Point your telescope at the object you selected and center it in the main optics of the telescope. 3. Lock the azimuth and altitude clamps to hold the telescope in place. 4. Check the finder to see where the object is located in the field of view. 5. Adjust the thumb screws on the finder bracket, until the cross hairs are centered on the target. Removing the Lens Cap The 8, 9.25 and 11" lens cap utilizes a bayonet-type locking mechanism to hold it in place.
Figure 2-14 Balancing the Mount in DEC Although the telescope does not track in declination, the telescope should also be balanced in this axis to prevent any sudden motions when the DEC lock lever is loose. To balance the telescope in DEC: 1. Loosen the R.A. clutch lock lever and rotate the telescope so that it is on one side of the mount (i.e., as described in the previous section on “Balancing the Mount in R.A.”). 2. Tighten the R.A. lock lever to hold the telescope in place. 3.
The latitude adjustment on the mount has a range from approximately 15° to 70°. It is best to always make final adjustments in latitude by moving the mount against gravity (i.e. using the rear latitude adjustment screw to raise the mount). Adjusting the Mount in Azimuth For rough adjustments in azimuth, simply pick up the telescope and tripod and move it side to side until it is roughly pointing towards north. For fine adjustments in azimuth: 1.
All Celestron computerized telescope come with a hand control designed to give you instant access to all the functions that your telescope has to offer. With automatic slewing to over 40,000 objects, and common sense menu descriptions, even a beginner can master its variety of features in just a few observing sessions. Below is a brief description of the individual components of the computerized hand controller: 1. 2. 3.
4. Catalog Keys: The hand control has keys on the hand control to allow direct access to each of the catalogs in its database. The hand control contains the following catalogs in its database: Messier – Complete list of all Messier objects. NGC – Complete list of all the deep-sky objects in the Revised New General Catalog. Caldwell – A combination of the best NGC and IC objects. Planets - All 8 planets in our Solar System plus the Moon. Stars – A compiled list of the brightest stars from the SAO catalog.
the telescope will automatically 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 Align procedure.
Select the time zone that you are observing from. Again, use the Up and Down buttons (10) to scroll through the choices. Refer to Time Zone map in Appendix for more information. Date - Enter the month, day and year of your observing session. Updating Your Location - Since you may not need to update your observing location as often as the date and time, it is not displayed each time you update the date and time. To update your city, press UNDO at any time when updating your date and time.
One Star Align One-Star Alignment works much the same way as Two-Star Align but uses only a single star in the sky for alignment. This method of alignment is not as accurate as the two-star alignment and is recommended only for telescopes that are permanently and accurately polar aligned. Solar System Align Solar System Align is designed to provide excellent tracking and GoTo performance by using solar system objects (Sun, Moon and planets) to align the telescope with the sky.
Last Alignment The Last Alignment method will automatically recall the last stored index positions to continue using the alignment that was saved when the telescope was last powered down. This is a useful feature should your telescope accidentally lose power or be powered down. NOTE: Just like with Quick-Align, you can use the Re-alignment feature (see below) to improve your telescopes pointing accuracy after using the Last Alignment method.
Pressing any of the other catalog keys (M, CALD, NGC, or STAR) will display a blinking cursor below the name of the catalog chosen. Use the numeric key pad to enter the number of any object within these standardized catalogs. For example, to find the Orion Nebula, press the "M" key and enter "042". Slewing to an Object Once the desired object is displayed on the hand control screen, choose from the following options: Press the INFO Key.
Direction Buttons The hand control has four direction buttons (3) in the center of the hand control which control the telescope's motion in altitude (up and down) and azimuth (left and right). The telescope can be controlled at nine different speed rates. Rate Button Pressing the RATE key (11) allows you to instantly change the speed rate of the motors from high speed slew rate to precise guiding rate or anywhere in between. Each rate corresponds to a number on the hand controller key pad.
Tracking Rate In addition to being able to move the telescope with the hand control buttons, your telescope will continually track a celestial object as it moves across the night sky. The tracking rate can be changed depending on what type of object is being observed: Sidereal This rate compensates for the rotation of the Earth by moving the telescope at the same rate as the rotation of the Earth, but in the opposite direction.
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 replace the previous user defined object with the current one. Get RA/DEC - Displays the right ascension and declination for the current position of the telescope. Goto R.A/ Dec - Allows you to input a specific R.A. and declination and slew to it. To store a set of coordinates (R.A.
Anti-backlash – All mechanical gears have a certain amount of backlash or play between the gears. This play is evident by how long it takes for a star to move in the eyepiece when the hand control arrow buttons are pressed (especially when changing directions). The CGEM anti-backlash features allows the user to compensate for backlash by inputting a value which quickly rewinds the motors just enough to eliminate the play between gears.
and clockwise (negative altitude) then make sure that the buttons used to center the alignment stars also move the telescope in the same directions. 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 autoguider for long exposure photography. OTA Orientation- Some users may wish to use an optional tandem bar adapter which allows you to attach to the mount two optical tubes at the same time.
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 degrees and by default set to 0º, being the position of the telescope when the counterweight bar is extended out horizontally. However, the slew limits can be customized depending on your needs.
R.A. switch - this procedure records the offset error when the right ascension index mark is aligned at start-up. Calibrating the R.A. Index will improve the accuracy of your initial star alignments when aligning the telescope in the future. GoTo Calibration – Goto Calibration is a useful tool when attaching heavy visual or photographic accessories to the telescope.
Scrolling Menu This menus allows you to change the rate of speed that the text scrolls across the hand control display. Press the Up (number 6) button to increase the speed of the text. Press the Down (number 9) button to decrease the speed of the text. Set Mount Position The Set Mount Position menu can be used to maintain your alignment in cases where you wish to disengaged the clutches or similar situation.
LIST ALIGN MENU NAME STAR TRACKING SELECT LOCATION NGC MODE EQ NORTH SET TO INDEX SAO ENTER TIME SOLAR SYSTEM EQ SOUTH RATE TOUR SIDEREAL DLS/ST SOLAR VARIABLE STARS TIME ZONE LUNAR ABELL VIEW TIME-SITE ENTER DATE – MM/DD/YY SCOPE SETUP SETUP TIME-SITE TWO STAR ALIGN ANTI-BACKLASH ASTERISM CALDWELL CCD OBJECTS SOLAR SYSTEM ALIGN FILTER LIMITS DIRECTION BUTTONS CONSTELLATIONS LAST ALIGNMENT DOUBLE STARS GOTO APPROACH AUTOGUIDE RATES QUICK ALIGN IC ONE STAR ALIGN MESSIER OTA
A telescope is an instrument that collects and focuses light. The nature of the optical design determines how the light is focused. Some telescopes, known as refractors, use lenses. Other telescopes, known as reflectors, use mirrors. The SchmidtCassegrain optical system (or Schmidt-Cass for short) uses a combination of mirrors and lenses and is referred to as a compound or catadioptric 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 primary mirror, is on the rear cell of the telescope just below the star diagonal and eyepiece. 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 until the image is sharp.
thousand yards. The apparent field of each eyepiece that Celestron manufactures is found in the Celestron Accessory Catalog (#93685). General Observing Hints When working with any optical instrument, there are a few things to remember to ensure you get the best possible image. Never look through window glass. Glass found in household windows is optically imperfect, and as a result, may vary in thickness from one part of a window to the next.
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 observational astronomy in general and includes information on the night sky and polar alignment. The Celestial Coordinate System To help find objects in the sky, astronomers use a celestial coordinate system that is similar to our geographical coordinate system here on Earth.
Motion of the Stars The daily motion of the Sun across the sky is familiar to even the most casual observer. This daily trek is not the Sun moving as early astronomers thought, but the result of the Earth's rotation. The Earth's rotation also causes the stars to do the same, scribing out a large circle as the Earth completes one rotation. The size of the circular path a star follows depends on where it is in the sky.
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 stars near it, this method works off of a known constant to determine how high the polar axis should be pointed. The CGEM mount can be adjusted from 15 to 70 degrees (see figure 5-3).
2. Then accurately center the star in your eyepiece and press ALIGN. The telescope will then "sync" on this star and slew to the position that star should be if it were accurately polar aligned. 3. Use the mounts latitude and azimuth adjustments (see figure 2-15) to place the star in the center of the eyepiece. Do not use the direction buttons on the hand control to position the star.
photography. This must be done in the dark when Polaris is visible and can be done using the hole in the polar axis or with the help of the optional polar axis finderscope. See Optional Accessory section. 1. Set the telescope up so that the polar axis is pointing towards north (see figure 2-3). 2. Remove the polar finderscope cover and the polar axis cover from both sides of the mount.
With your telescope set up, you are ready to use it for observing. This section covers visual observing hints for both solar system and deep sky objects as well as general observing conditions which will affect your ability to observe. Observing the Moon Often, it is tempting to look at the Moon when it is full. At this time, the face we see is fully illuminated and its light can be overpowering. In addition, little or no contrast can be seen during this phase.
Solar Observing Hints The best time to observe the Sun is in the early morning or late afternoon when the air is cooler. To center the Sun without looking into the eyepiece, watch the shadow of the telescope tube until it forms a circular shadow. To ensure accurate tracking, be sure to select the solar tracking rate. Observing Deep Sky Objects Deep-sky objects are simply those objects outside the boundaries of our solar system.
Figure 6-1 Seeing conditions directly affect image quality. These drawings represent a point source (i.e., star) under bad seeing conditions (left) to excellent conditions (right). Most often, seeing conditions produce images that lie some where between these two extremes.
After looking at the night sky for a while you may want to try photographing it. Several forms of celestial photography are possible with your telescope, including short exposure prime focus, eyepiece projection, long exposure deep sky, terrestrial and even CCD imaging. Each of these is discussed in moderate detail with enough information to get you started. Topics include the accessories required and some simple techniques.
1. Load your camera with film that has a moderate-to-fast speed (i.e., ISO rating). Faster films are more desirable when the 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 400 ISO color slide film Fuji Super HG 400 Ektar 25 or 100 2. Center the Moon in the field of your telescope. 3. Focus the telescope by turning the focus knob until the image is sharp. 4.
Because of the high magnifications during eyepiece projection, the field of view is quite small which makes it difficult to find and center objects. To make the job a little easier, align the finder as accurately as possible. This allows you to get the object in the telescope's field based on the finder's view alone. Another problem introduced by the high magnification is vibration. Simply tripping the shutter even with a cable release produces enough vibration to smear the image.
Once you have mastered the technique, experiment with different films, different focal length eyepieces, and even different filters. Long Exposure Prime Focus Photography This is the last form of celestial photography to be attempted after others have been mastered. It is intended primarily for deep sky objects, that is objects outside our solar system which includes star clusters, nebulae, and galaxies. While it may seem that high magnification is required for these objects, just the opposite is true.
3M 1000 (color slide) Scotchchrome 400 T-Max 3200 (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 reducing the number of user corrections needed to keep a guide star centered in the eyepiece. PEC is designed to improve photographic quality by reducing the amplitude of the worm errors. Using the PEC function is a three-step process.
7. Point the telescope at the object you want to photograph and center the guide star on the illuminated cross hairs and you are ready to play back the periodic error correction. 8. Once the drive's periodic error has been recorded, use the Playback function to begin playing back the correction for future photographic guiding. If you want to re-record the periodic error, select Record and repeat the recording processes again.
Another way to reduce vibration is with the Vibration Suppression Pads (#93503). These pads rest between the ground and tripod feet. They reduce the vibration amplitude and vibration time. CCD Imaging SCT telescope's versatility allows it to be used in many different f-number configurations for CCD imaging. It can be used at f/6.3 (with the optional Reducer/Corrector), f/10, and f/20 (with the optional 2x Barlow) making it the most versatile imaging system available today.
While your telescope requires little maintenance, there are a few things to remember that will ensure your telescope performs at its best. Care and Cleaning of the Optics Occasionally, dust and/or moisture may build up on the corrector 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 can of pressurized air.
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. To verify collimation, view a star near the zenith. Use a medium to high power ocular — 12mm to 6mm focal length. It is important to center a star in the center of the field to judge collimation. Slowly cross in and out of focus and judge the symmetry of the star.
7. Once the star image is in the center of the field of view, check to see if the rings are concentric. If the central obstruction is still skewed in the same direction, then continue turning the screw(s) in the same direction. If you find that the ring pattern is skewed in a different direction, than simply repeat steps 2 through 6 as described above for the new direction. Perfect collimation will yield a star image very symmetrical just inside and outside of focus.
You will find that additional accessories enhance your viewing pleasure and expand the usefulness of your telescope. For ease of reference, all the accessories are listed in alphabetical order. Barlow Lens - A Barlow lens is a negative lens that increases the focal length of a telescope. Used with any eyepiece, it doubles the magnification of that eyepiece. Celestron offers two Barlow lens in the 1-1/4" size.
Series 2 – #94119-20 Deep Yellow, Red, Light Green, ND25% T (#s 12, 25, 56, 96ND-25) Series 3 – #94119-30 Light Red, Blue, Green, ND50% T (#s 23A, 38A, 58, 96ND-50) Series 4 – #94119-40 Yellow, Deep Yellow, Violet, Pale Blue (#s 8, 47, 82A, ND96-13) Flashlight, Night Vision - (#93588) - Celestron’s premium model for astronomy, using two red LED's to preserve night vision better than red filters or other devices. Brightness is adjustable. Operates on a single 9 volt battery (included).
Reducer/Corrector (#94175) - This lens reduces the focal length of the telescope by 37%, making your C8-S a 1280mm 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 circular image on the processed film. It also increases the field of view significantly and is ideal for wide-field, deep-space viewing.
Appendix A – Technical Specifications CGEM Series 11097 CGEM 800 11098 CGEM 925 11099 CGEM 1100 203mm (8") SchmidtCassegrain 2032mm F/10 6x30 CGEM Computerized Equatorial 25mm Plossl (81x) 1.25" Yes 2" Stainless Steel 235mm (9.25") SchmidtCassegrain 2350mm F/10 6x30 CGEM Computerized Equatorial 25mm Plossl (94x) 1.25" Yes 2" Stainless Steel 280mm (11") SchmidtCassegrain 2800mm F/10 9x50 CGEM Computerized Equatorial 40mm Plossl (70x) 1.25" Yes 2" Stainless Steel 480x 29x 14 .68 arc seconds .
Appendix B - Glossary of Terms AAbsolute magnitude Airy disk Alt-Azimuth Mounting Altitude Aperture Apparent Magnitude Arcminute Arcsecond Asterism Asteroid Astrology Astronomical unit (AU) Aurora Azimuth BBinary Stars CCelestial Equator Celestial pole Celestial Sphere Collimation DDeclination (DEC) EEcliptic Equatorial mount FFocal length The apparent magnitude that a star would have if it were observed from a standard distance of 10 parsecs, or 32.6 light-years.
JJovian Planets KKuiper Belt LLight-Year (LY) MMagnitude Meridian Messier NNebula North Celestial Pole Nova OOpen Cluster PParallax Parfocal Parsec Point Source RReflector Resolution Right Ascension: (RA) SSchmidt Telescope Sidereal Rate Any of the four gas giant planets that are at a greater distance form the sun than the terrestrial planets. A region beyond the orbit of Neptune extending to about 1000 AU which is a source of many short period comets.
telescope at this rate. The rate is 15 arc seconds per second or 15 degrees per hour. TTerminator UUniverse VVariable Star WWaning Moon The boundary line between the light and dark portion of the moon or a planet. The totality of astronomical things, events, relations and energies capable of being described objectively. A star whose brightness varies over time due to either inherent properties of the star or something eclipsing or obscuring the brightness of the star.
Appendix C - RS-232 Connection You can control your telescope with a computer via the RS-232 port on the computerized hand control and using an optional RS-232 cable (#93920). Once connected, the telescope can be controlled using popular astronomy software programs. Communication Protocol: The CGEM Mount communicates at 9600 bits/sec, No parity and a stop bit. All angles are communicated with 16 bit angle and communicated using ASCII hexadecimal.
Additional RS232 Commands Send Any Track Rate Through RS232 To The Hand Control 1. 2. 3. 4. Multiply the desired tracking rate (arcseconds/second) by 4. Example: if the desired trackrate is 150 arcseconds/second, then TRACKRATE = 600 Separate TRACKRATE into two bytes, such that (TRACKRATE = TrackRateHigh*256 + rackRateLow). Example: TrackRateHigh = 2 TrackRateLow = 88 To send a tracking rate, send the following 8 bytes: a. Positive Azm tracking: 80, 3, 16, 6, TrackRateHigh, TrackRateLow, 0, 0 b.
APPENDIX D – MAPS OF TIME ZONES 62
CELESTRON TWO YEAR WARRANTY A. Celestron warrants this telescope 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.
Celestron 2835 Columbia Street Torrance, CA 90503 U.S.A. Tel. (310) 328-9560 Fax. (310) 212-5835 Web site at http//www.celestron.com Copyright 2008 Celestron All rights reserved. (Products or instructions may change without notice or obligation.) Item # 11097-INST $10.
