
NOTE: This product is currently shipping, however, due to overwhelming demand, we are accepting preorders for May 2010 fulfillment.
The CGEM 1100 HD combines Celestron's newly designed CGEM Computerized Equatorial mount with its new EdgeHD optical system. With an optical tube assembly weighing only 28 lbs., this telescope is still portable enough to be taken to dark skies, and has 89% more light gathering power than an 8" telescope and 40% more than the 9.25". For astrophotography, the German Equatorial mount offers easier balancing, unlimited space at the rear of the telescope tube to mount a camera, and whole sky access. Now you can enjoy all of the NexStar software and database features with the extra stability and portability of a German Equatorial mount.
New Optical Design
The EdgeHD optical system takes all of the compact power popularized by the SCT and combines it with an improved high definition optical system for wide field, astrograph quality
images.
As a visual instrument EdgeHD optics deliver pinpoint images even with your widest field eyepiece. You can search for all of the Messier Catalog objects, and see hundreds of other
equally interesting NGC, IC and Caldwell objects with amazing clarity. For astroimaging, the EdgeHD optics produce aberration-free images across your favorite CCD or DSLR camera. All EdgeHD
optics are designed to produce an extremely flat focal plane precise enough to match the strict tolerances of the largest commercial ccd detectors, allowing all stars to be in tight focus to
the very edge of the chip.
Diffraction Limited
Some companies boast that their telescopes give diffraction limited stars in the very center of the field of view. EdgeHD optics not only produce diffraction limited stars on axis, but
maintain diffraction limited stars across the entire field of view of many of the most popular astrophotography cameras. Even at the very edge of a full frame camera
chip, the EdgeHD 11" delivers star sizes of less than 2 arc seconds.
The EdgeHD 11" optics produce a focal plane three-times flatter than the standard equivalent SCT telescope with diffraction limited stars to the very edge of the Nikon 300 or Canon 40D sensor!
Along with the newly designed optics, the EdgeHD also has a re-designed optical tube guaranteed to help you get the maximum performance from your instrument.
Features Include:
Mirror Locks – To hold the mirror in place and reduce image shift during imaging.
Tube Vents - Each vent has an integrated 60 micron micro-mesh filter allowing hot air to be released from behind the primary mirror.
Fastar Versatility – All EdgeHD optical tubes are equipped with a removable secondary mirror for fast f/2 ccd imaging. Not only does imaging in the FASTAR configuration allow for exposure times that are 25 times faster than at f/10, but also yields a field of view five times wider. A perfect combination for imaging your favorite wide field objects in a fraction of the time. (FASTAR imaging requires a third party lens assembly in place of the secondary mirror).
Axiom Eyepiece - EdgeHD 11" optical tubes come with Celestron's top of the line Axiom eyepiece. With a 23mm focal length and 82° AFOV you get an incredible combination of power and wide field of view. Plus each Axiom eyepiece is optimized to deliver pinpoint images when used with a flat field telescope.
Learn more about the benefits and features of this new optical system by going to the Edge HD web page.
CGEM™ Mount
The CGEM™ mount has a fresh, attractive, bold appearance and is capable of carrying Celestron's higher-end SCT optical tubes (up to 11") securely and vibration free which is ideal for both imaging and visual observing.
Ergonomic Design - CGEM was designed to be ergonomically friendly with large Altitude and Azimuth adjustment knobs for quick and easy polar alignment adjustment. The internal RA and DEC motor wiring provides a clean look and an easy and trouble free set up.
Innovation - The CGEM series has a new innovative Polar alignment procedure called All-Star™ (patent pending). All-Star allows users to choose any bright star, while the software calculates and assists with polar alignment. Another great feature of the CGEM, sure to please astroimagers, is the Permanent Periodic Error Correction (PEC) which will allow users to train out the worm gears periodic errors, while the mount retains the PEC recordings.
Performance - For objects near the Meridian (imaginary line passing from North to South), the CGEM will track well past the Meridian for uninterrupted imaging through the most ideal part of the sky. The CGEM mount has a robust database with over 40,000 objects, 100 user defined programmable objects and enhanced information on over 200 objects.
Celestron's CGEM mount is the perfect fit between the Advanced Series and CGE Series. Offering the portability of the Advanced Series and the precision of the CGE.

CELESTRON TWO YEAR LIMITED WARRANTY
A. Celestron warrants your 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. 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 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 contact:
Celestron
Customer Service Department
2835 Columbia Street
Torrance, CA 90503
Tel. (310) 328-9560
Fax. (310) 212-5835
Monday-Friday 8AM-4PM PST
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.


Navigate through this section to get detailed information on how XLT is designed, and how XLT measures up against our current StarBright coatings. We have also used this site as a resource to provide information on our testing methods and we offer a section detailing which models this new coating will be available with and the cost breakdown for each model.
OVERVIEW
COATINGS OVERVIEW
STARBRIGHT XLT SYSTEM
CURRENT STARBRIGHT
OUR MEASUREMENTS
To find a Celestron Dealer near you who carries telescopes with StarBright XLT, please click here for our Dealer Locater.
StarBright XLT & Our Commitment to Quality TOP
We strive to design and engineer products with quality components using a state of the art manufacturing process that is followed up with uncompromising quality assurance. You can see it in the design and quality of our entire product line. And our new StarBright XLT coating system is no exception.
Design - We design and test our optical coatings with the aid of thin film design software in wide use throughout the optical, semiconductor, aerospace, and telecommunications industries. Using this software we have improved on our multi-layer enhanced mirror coatings, shifting the peak reflectance to the center of the visible spectrum. We have designed a completely new multi-layer anti-reflective coating and have introduced a new low absorption, high transmission glass for our corrector lens. This unequaled combination is standard with every StarBright XLT system.
Quality Components and Process - Our coating process uses state-of-the-art thin film vacuum deposition technology. To ensure consistent optical coatings of the highest quality the process is tightly monitored and controlled by highly trained coating technicians. Prior to coating, each optical element is thoroughly cleaned and inspected to ensure proper adhesion of the films during the coating process. The materials used in our reflective and anti-reflective coatings including Aluminum, Hafnium Oxide, Titanium Dioxide, Silicon Dioxide, and Magnesium Fluoride are the purest available, exceeding 99.99%.
Quality Assurance - Our QA process is designed to prevent any optical element from passing if it does not meet our strict standards of optical quality. Witness plates are included in each coating run, and are subjected to spectrophotometric analysis to determine if the minimum acceptable transmission or reflectance has been achieved.
Optical Elements of the Schmidt-Cassegrain Telescope TOP
A telescope is a group of optical elements that collects light and focuses it for observation by an eyepiece or some other imaging device. There are two types of optical elements: mirrors and lenses. Mirrors reflect light and lenses refract, or bend light. The Schmidt-Cassegrain telescope uses both mirrors and lenses. The diagram below shows a cross-section of a Schmidt-Cassegrain. In this telescope, light first passes through the corrector lens, and then reflects off the primary mirror. Finally, it reflects off the secondary mirror and comes to a focus at the focal plane.
Optical Coatings
The purpose of a telescope is to collect as much light as possible. The amount of light collected affects the brightness of the resulting image. Unfortunately, there are sources of light loss at each optical surface, and within each lens. Fortunately, we can design optical coatings and choose lens materials that minimize the amount of light lost to these sources.
Optical coatings are very thin layers of material that are applied to the glass in a process called 'vacuum deposition '. The physical properties and thickness of each layer in the coating, as well as their orientation with each other and the glass to which they are applied, determine how well they will do their job.
Since the function of a mirror is to collect light by way of reflection, we use highly reflective metallic coatings on these optical elements. A mirror without coatings reflects about 4% of the light that hits its surface. A mirror coated with standard Aluminum coatings reflects about 86 - 88%, and a mirror coated with StarBright XLT reflects 95%.
Light traveling through a lens is a little more complicated. In this case, light is lost to both reflection and absorption. When light first strikes an uncoated lens, about 4% is reflected back and never has the chance to make it through. Some of the remaining 96% will be absorbed on its way through the glass, and then the second lens surface reflects another 4%. To minimize unwanted reflection, dielectric materials are used in pairs of alternating high and low refractive index. A good anti-reflection (A/R) coating for telescope lenses is one that will deliver very low, very 'flat ' reflectance across the entire visible spectrum.
Although A/R coatings can dramatically reduce the amount of light lost to reflection, no optical coating can reduce the amount of light lost to absorption within the glass. To reduce this source of light loss, it is important to choose a glass that absorbs as little light as possible.
For many A/R coating applications, it is standard to measure the reflection of the coated surface and to ignore the amount of light that is being absorbed by the glass. But for a telescope lens, stating how well an A/R coating suppresses reflection without also revealing how much light is lost to absorption within the glass can be quite misleading. For this application, actual transmission, which accounts for light lost to both sources, should be measured directly. You can learn more about how we did these measurements in the section titled Our Measurements.
Telescope System Transmission
System transmission is the percentage of light that arrives at the focal plane compared to the light that enters the telescope, and is calculated by taking the product of the corrector lens transmission, the primary mirror reflectance, and the secondary mirror reflectance. Here is an example; if the corrector lens transmits 92% of the light, and the primary and secondary each reflect 89% of the light, then:
Total System Transmission = .92 * .89 * .89 = .73 (73%)
StarBright XLT - An Optical System Breakthrough! TOP
Celestron has brought its renowned StarBright technology to an even higher level of light transmission with the introduction of our new optional StarBright XLT High Performance Optical Coating System.
StarBright XLT Optical System Design - You'll See The Light.
One of the most important factors in the evaluation of a Schmidt-Cassegrain telescope's optical system performance is its transmission - the percentage of incoming light that reaches the focal plane. The design of the XLT System accomplishes two crucial objectives: Develop a coating system that is optimized for visual use and for CCD/Photographic imaging.
The StarBright XLT System - What Makes It Different Makes It Better
There are three major components that make up our StarBright XLT high transmission optical system design:
1. Unique enhanced multi-layer mirror coatings
Our mirror coatings are made from precise layers of Aluminum (Al), SiO2 (quartz), TiO2 (Titanium Dioxide), and Si02. Reflectivity is fairly flat across the spectrum, optimizing it for both
CCD imaging and visual use. Click here to see a plot of the reflectivity of XLT's Mirror Coatings.
2. Multi-layer anti-reflective coatings
Made from precise layers of MgF2 (Magnesium Fluoride), and HfO2 (Hafnium Dioxide) A rare element costing nearly $2000 per kilogram, Hafnium gives us a wider band pass than Titanium, used in
competing coatings. Click here to see a plot of XLT's corrector transmission.
3. High Transmission Water White glass
Celestron Schmidt-Cassegrain optical systems with optional StarBright XLT coatings use Water White glass instead of Soda Lime glass for the corrector lens. Water White glass transmits about
90.5% without anti-reflective coatings. That is 3.5% better transmission than uncoated Soda Lime glass. When Water White glass is used in conjunction with StarBright XLT 's anti-reflective
coatings, the average transmission reaches 97.4% - an 8% improvement! Click here to see a plot of water white glass versus soda lime.*
These three components of our StarBright XLT coatings result in one of the finest coatings available. The peak transmission for the systems is 89% at 520 nm. The overall system transmission is 83.5% averaged over the spectrum from 400 to 750 nm. The plot below shows the entire system transmission over the spectrum.

This plot is obtained by measuring the reflectivity of the secondary mirror and the primary mirror and measuring the amount of light transmitted through the coated corrector lens. Each of
those values are multiplied together calculate the system transmission. The overall system transmission peaks at 88.9% while the average transmission is 83.5% over the spectrum from 400 to
750nm.
*Percent differences are calculated by taking the comparison data percentage divided by the baseline data. Example: Measured average system transmission for current StarBright is 72%. XLT average system transmission is 83.5%. 83.5% divided by 72% = 1.16 or 16% improvement. Measurement results are rounded to the nearest whole percentage.
StarBright XLT vs. Current StarBright Coatings TOP
StarBright XLT system transmission gives a 16% improvement compared to the current StarBright coatings. The average system transmission for the current StarBright coatings is 72% where the average system transmission StarBright XLT is 83.5%. Current StarBright uses soda lime glass correctors where StarBright XLT uses water white glass, which improves the corrector throughput dramatically.
The average system transmission of StarBright XLT 83.5% compared to current StarBright at 72%. StarBright XLT is a 16% improvement over current StarBright .* The peak transmissions of each being 89% and 80% respectively.
StarBright Mirror Reflectivity Comparison
StarBright XLT mirror reflectivity peaks at 95% and has an average reflectance across the spectrum of 93%. Click on the link above to show how XLT compares to current StarBright and UHTC.

Mirror Reflectivity for StarBright XLT and current StarBright. StarBright XLT reflectivity peaks at 95% and has an average reflectance across the spectrum of 93%. Current StarBright peaks
at 94% with an average reflection of 91% across the spectrum.
StarBright Corrector Transmission Comparison
XLT's corrector transmission is 97.4% versus current StarBright with 87% and UHTC with 91% across the spectrum from 450 to 750 nm.
Average XLT transmission of 97.4% versus current StarBright with 87% across the spectrum from 450 to 750 nm. StarBright XLT is a 12% improvement over current StarBright transmission.* StarBright XLT has peak transmission at 99%, while current StarBright peaks at 91%.
*Percent differences are calculated by taking the comparison data percentage divided by the baseline data. Example: Measured average system transmission for current StarBright is 72%. XLT average system transmission is 83.5%. 83.5% divided by 72% = 1.16 or 16% improvement. Measurement results are rounded to the nearest whole percentage.
Testing Methods: TOP
Total telescope light throughput can be measured in two different ways; either by measurement of the assembled optical system, or by measurement of the reflectance of each mirror (or reflective element), and the transmission of each refractive element in the optical path. In the case of a Schmidt Cassegrain telescope, there are two reflective elements (the primary and secondary mirrors), and one refractive element (the corrector plate, or Schmidt Corrector). See diagram below:
Assembled Telescope vs. Individual Optical Element Analysis:
To measure the throughput of the assembled telescope, a beam of light is passed through the telescope and compared to a beam of equal intensity light passing through air only. Total telescope throughput is then the ratio of light intensity measured through the telescope divided by the light intensity measured through air. This is easily said, but very challenging to execute correctly. Great care must be taken to ensure that the reference beam is of constant intensity, and that its light is collected in a manner which does not bias the results. Errors introduced by beam geometry (f ratio) at the entrance to the detector, less than perfect alignment of the optical elements, including placement and dimensions of internal light baffles, will tend to reduce the intensity of light measured through the telescope.
The second method of measuring total telescope throughput, by spectrophotometric analysis of each element in the optical path, is not susceptible to these sources of error. Furthermore, individual element analysis provides specific information about each optical element, while measuring the throughput of the assembled optical tube does not. Results obtained in this manner represent an upper limit to the actual throughput of the assembled telescope. Total Telescope Throughput (%TT) is less than or equal to Corrector Plate Transmission (%TC) times Primary Mirror Reflectance (%RP) times Secondary Mirror Reflectance (%RS).
Corrector Plate Transmission (%TC):
We use a Shimadzu UV1601 spectrophotometer for analysis of corrector plate transmission. This is a double beam instrument with a spectral range of 190 to 1100nm. Transmission data is typically collected in the visible region from 400 to 750 nm. Small samples of corrector material called witness plates are included in each corrector coating run. In order to minimize handling and the possibility of scratching a full size corrector plate, we use these witness plates to represent the transmission characteristics of our correctors.
Our instrument is capable, however, of measuring the transmission of correctors up to 8" diameter. If this is necessary, the corrector plate is measured at 4 points roughly 90� apart, and the results are averaged. Before and after each measurement, baseline (100%) measurements are made to ensure light source and/or detector drift is negligible.
Primary and Secondary Reflectance (%RP, %RS):
The preferred method of measuring reflectance of primary and secondary mirrors involves the use of witness plates as well. These are small (1" to 2" diameter) flat polished glass substrates, which are coated along with the primary and secondary mirrors. Since the coating process is the same, and the surfaces are equally well polished, the reflectance of the witness plate is the same as that for the primary and secondary mirror. The reasons for using flat witness plates are 1) the primary and secondary mirrors are not themselves subjected to a measurement process which can potentially cause scratches, and 2) very simple test methods and readily available reference standards can be used to measure the reflectance of flat surfaces.
Typically, the reflectance of a surface is measured against a standard reference of known reflectance. Our standard reference is an enhanced aluminum coated quartz flat, calibrated against a NIST (National Institute of Standards and Technology) specular reflectance standard. To measure the reflectance of a flat sample, the baseline measurement is made using this standard, and the reflectance of the sample is compared to this baseline. The sample reflectance factor (%RS) is equal to its reflectance relative to the reference standard (%RSR) times the reference standard's known reflectance (%RR):
However, if the sample to be measured has a curved surface like a secondary or a primary mirror, and there is no witness plate available, then special care must be taken to ensure that the method used to measure reflectance is insensitive to this curvature. If we compared the reflectance of a curved surface directly to that of a flat reflectance standard, our results would not be accurate, since the converging or diverging beam generated by a curved surface would direct either less light (in the case of a secondary mirror), or more light (in the case of a primary mirror) onto the detector than was directed by the flat reference standard.
The most widely used tool for measuring the reflectance of curved surfaces is called an integrating sphere. This device collects and then measures the intensity of light in a manner which is insensitive to beam geometry, hence, insensitive to surface curvature of a reflective sample being measured. However, integrating spheres can be quite expensive, and they are time-consuming to set up and calibrate. We developed a method which is equally insensitive to surface curvature, but much less costly and time consuming to perform. We made our own reference standards from secondary and primary mirrors with the same surface curvature as those we wished to test.
We obtained samples of the secondary and primary mirrors which we wished to test, stripped the existing coating, and replaced it with one for which we also obtained flat witness plates. These flat witness plates were calibrated against a NIST specular reflectance standard. Since the flat witness plates were coated along with the curved samples, and since we have adequate data to show that our coatings are very uniform from part to part in any given coating run, we can apply this reflectance data to our curved samples. Using these curved surface reflectance standards we are able to measure other mirrors of the same curvature just as we use our flat reflectance standard to measure the reflectance of flat samples.
To perform these measurements, we use an Ocean Optics USB2000 Spectrometer with an LS-1 Tungsten Halogen Light Source. This is a single-beam instrument with a 0.3nm resolution, a scanning range from 340nm to 1024nm, and is equipped with a fiber optic curved-surface reflectance measuring probe.
Reporting the Data:
Collecting the data and reducing it to yield total telescope throughput (%TT) (system transmission) is simply a matter of multiplication. We find the average of each data set (%TC, %RP, and %RS) for each wavelength measured, and multiply them together.
NexRemote Control Software
for Celestron Computerized Telescopes
OVERVIEW
SYSTEM REQUIREMENTS
NEXREMOTE KIT
DOWNLOADS
Celestron has been in the forefront of computerized telescope technology for over two decades. We have taken this expertise in telescope technology one step further by introducing the NexRemote™ Telescope Control Software. NexRemote allows the user to control their Celestron computerized telescope from their personal computer. Everything that is done using the telescope’s hand control can now be done remotely from a PC or laptop. This software was developed for Celestron’s high-end telescopes that use the NexStar control system including the NexStar "i" Series, Advanced Series, NexStar GPS Series and CGE Series.
NexRemote provides full emulation of every aspect of the Celestron Computerized Hand Control including:
NexRemote began shipping in March 2005 with select high-end computerized Celestron telescopes including NexStar i Series models, NexStar GPS models and CGE models. Contact your Celestron dealer to find out availability of upgraded models that include NexRemote. Software will also come with an RS-232 cable to connect your Celestron telescope to a PC. For those who already own a compatible Celestron computerized telescope and want to take it to the next level of convenience and enjoyment, the software can be purchased separately as a kit through an authorized Celestron dealer (item# 93710). Kit includes the NexRemote software & license, RS-232 cable and a Serial-to-USB adapter.
Compatible Telescopes:
Computer:
Port:
Cable:
Gamepad:
NOTE: Virtually any gamepad can be configured to work with NexRemote. Read the help files for details.
Now Celestron Advanced Series GT, NexStar “i” Series, GPS, and CGE Series telescopes can be set up and operated remotely from a PC or laptop! NexRemote duplicates all of the functions and features of our NexStar software on the standard NexStar Hand Control plus much more! See our section on NexRemote for more information.
Kit Includes:
NexRemote Software CD with license
RS-232 Cable to connect telescope to PC or Laptop
Serial-To-USB Adapter
Features include:
*NexRemote is included with select NexStar "i" Series, GPS, and CGE Series telescopes beginning in March, 2005 (contact your Celestron Dealer for availability of models with NexRemote).
For the telescopes that have this technology feature, users can upgrade their telescope's operating software via the Internet.
The following products have this feature:
Current upgrades can be found through our downloads section and on each telescope's product page. To receive an announcement when upgrades have been added, make sure you are subscribed to our mailing list.
| Learn about EdgeHD Optics straight from Celestron's engineers: |
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EdgeHD is an aplanatic Schmidt telescope designed to produce aberration-free images across a wide visual and photographic field of view. The optical system was designed to reduce more than just off-axis star coma, but also to give an astrograph quality flat focal plane all the way to the edge of the field of view.
Many optical designs that advertise themselves as "astrograph" quality actually only produce pinpoint stars across a curved focal plane. While this may be acceptable for visual observing, stars will appear out of focus at the edge when used with a flat chip sensor of a digital camera. EdgeHD optics produce a focal plane more than three-times flatter than a standard Schmidt Cassegrain telescope and dramatically flatter than other competing coma-free designs. This guarantees you visibly sharp stars across some of the largest ccd chips available today.

Above: A curved focal plane does not perfectly coincide with a flat CCD chip and therefore will appear out of focus at the edges.
Even when focused sharply in the center of the field of view, a curved focal plane will produce out of focus stars at the edges. The wider the field of view the more pronounced the defect becomes. Compare the two images below. Both images were taken with the same camera under the same conditions. When focused on-axis both appear to be sharp in the center of the image. But as you view the stars closer and closer to the edge, the stars in the first image (taken with a competing coma-free design) become larger and less focused until finally, at the very corners, the star images are de-focused so much that they appear as rings instead of pinpoints.
Competing Coma Free Optical Design
Celestron EdgeHD Optics
Fig 1 - Competing Coma Free design focused on axis, shows sharp stars in the center of the image, but dramatically out of focus stars (donuts) at the edges.
Fig 2 - EdgeHD focused on axis, focuses sharply across the entire FOV.
Both M3 images taken with a 35 mm chip (42 mm diameter focal plane) camera
Superior edge performance not only creates rounder, more pleasing stars but actually improves the resolution and limiting magnitude when compared to telescopes of equal aperture.
Celestron's High Definition optics let you resolve smaller spot sizes all the way to outer edge, revealing finer detail and greater contrast.
EdgeHD optics give you smaller (more concentrated) stars that create brighter images and allow you to see down to a fainter magnitude than other equally sized telescopes. Poor edge quality can spread out starlight so much that the brightness of a star appears the same as the sky background, making it undetectable to your eye (or camera). With EdgeHD optics you will be able to capture the faintest of galaxies all the way to the corner of your full frame camera chip.
The image below is one 60 second guided image taken with the EdgeHD 11" and Canon 5D (full frame) camera. The field of view represents almost one full degree from corner to corner. Enlarge this image to 100% and inspect the star images on-axis and all the way out to the Edge.
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Coupled with Celestron's XLT coating group on every surface, EdgeHD optics give you maximum light throughput across the widest visual and photographic
spectrum.
For more information about Celestron's XLT coating, go to the XLT coating web page.
In addition to Celestron's new optimized optical design, the EdgeHD tube has been redesigned to make sure you get the most from your optics each and every night.
Mirror Support - Flexible tension clutches hold the mirror in place and reduce image shift when rotating the tube around the mount. The flexible rods allow the mirror to be held in place without putting any force or pressure on the mirror assembly, keeping the image centered in the eyepiece (or chip).
Tube Vents - Cooling vents located on the rear cell allow hot air to be released from behind the primary mirror. Each vent has an integrated 60 micron micro-mesh filter guaranteed to let warm air out without letting dust in.
Fastar Versatility -The EdgeHD are the most versatile imaging scopes available today. At its native f10 you can achieve the image scale neccesary to capture the
smallest of deep sky objects. With the optional reducer lens (coming soon) you can increase your field of view without sacrificing optical performance. A barlow gives you the added power
for high resolution planetary, lunar and solar imaging. And of course all EdgeHD optical tubes are Fastar compatible for ultra fast f/2 wide field imaging*. Each tube has been fitted with a
removable secondary mirror and are opto-mechanically aligned on a laser bench to ensure they are axially symmetric in any configuration.
*requires the use of the Hyperstar lens assembly
Easy Collimation - With precision machined mechanics and a spherical secondary mirror, EdgeHD optics can be collimated accurately and easily to guarantee that they perform to their potential every time you use them.
All-Star Polar Alignment Technology
German Equatorial Mounts (GEM) have long since been recognized as the mount of choice for astrophotography. Needing to track in only one axis for long exposures; adjustable counterweights and tube position for perfect balance, the GEM has few short comings when it comes to imaging. However accurate tracking still depends on an accurate polar alignment. Even with a visible star very near the North Celestial Pole (NCP), the true celestial pole can be a very elusive place to find without assistance.
Now select Celestron mounts can utilize a new innovative Polar alignment procedure called All-Star™. All-Star allows users to choose any bright star, while the software calculates and assists with polar alignment.
Here's how it works.
Once your telescope is aligned with two bright star, All-Star allows you to choose any bright star listed in the NexStar hand control to assist in accurately aligning your telescope's mount with the North Celestial Pole. Using the telescope's Sync function, the mount is able to point and center a bright star with a high degree of accuracy. Once centered, the mount will point the telescope to the exact position that the star should be if the mount were precisely polar aligned. By simply adjusting the mounts altitude and azimuth controls to re-center the star in the center of the eyepiece, you are actually moving the mounts polar axis to the exact position of the North Celestial Pole.
FAQ
Can I use Polaris to polar align my telescope?
Since Polaris is very close to the NCP and not very bright, it is actually not a recommended star for the "All-Star" method. The advantages of being able to use stars other than Polaris are
two fold:
Which stars are best to use for polar aligning?
For best results choose a bright alignment star that is near the Meridian, preferably close to the celestial equator. Try to avoid stars that are close to the west/east horizon or directly
overhead because they can be more difficult to center using the mount's altitude and azimuth controls. Also stars too near the celestial pole are less accurate than those further away.
Will I lose my alignment after I polar align?
No, the mount will retain its alignment but some amount of accuracy may be compromised depending on how much the mount has been moved during polar alignment. Although the telscopes tracking
may be very good, pointing accuracy may need to be improved, especially if you are trying to located small objects on a ccd chip.
What are the steps to polar align my telescope using "All-Star" polar alignment?