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REVIEW OF MEADE LX850 ASTRO-IMAGING SYSTEM
REVIEW OF MEADE LX850 IMAGING SYSTEM
New-comers to deep-sky astrophotography are faced with two very daunting questions:
1. Which telescope and mount to buy, and which autoguider, camera,
and software will go well with it?
2. How do I get all this equipment to run together smoothly?
In the design of the LX850 Astro-Imaging System, Meade have set out to solve these problems for the novice.
The LX850 mount is a complete imaging system. You just need to add a telescope and Camera; all other hardware and software needed for astro-imaging is already included.
The Meade LX850 mount can be purchased on its own, for you to add a telescope of your choice. But the mount is also suuplied as a package deal with one of four Meade telescopes:
a 130-mm f7 APO Refractor, and Advanced Coma Free Schmidt-Cassegrains with apertures of 10 inch, 12 inch, and 14 inch f8 .
REVIEW OF REVIEWS
MEADE LX850 ASTRO-IMAGING SYSTEM
Assembling the LX850
The Meade LX850 mount is large and heavy - in order to move the telescope (even a short distance) you will need to break the telescope down into its components. The heaviest component is the equatorial head (78 lbs including counterweight shafts). The giant tripod weighs in at 36 lbs. The weight of the optical tubes are 130mm APO (25 lbs), 10" SCT (33 lbs), 12" SCT (48 lbs), and 14" SCT (63 lbs). And of course, each optical tube will require a similar counterweight to balance the tube.
The LX850 is cleverly designed. Only two Allen wrenches (supplied) are required to assemble the mount. Putting it all together might take 30 minutes first time out, but will down to 15 minutes with a little experience.
Polar Alignment of the LX850
Once the LX850 is assembled, the mount can be polar aligned and ready for imaging within about 15 minutes. This "quick" method of polar alignment is good for exposures up to about 5 minutes, but requires having a clear view of the celestial pole.
Without a clear view of the celestial pole, you need to use the "Drift Alignment Assist" polar alignment method. The process takes 15 minutes longer, but is fully automated by the StarLock system. It produces more accurate polar alignment, good for razor-sharp 10 minute, and longer, exposures.
Finding targets (GoTo)
The Meade LX850 is a German equatorial mount with a built-in autoguider. The electronics of the autoguider (StarLock), are built into Meade's tried and tested Autostar II hand controller.
Thekey to the StarLock system is a pair of digital sensors that attach directly to the mount or to the main telescope.
After polar alignment, any one of thousands of objects in the LX850 database can be found by pressing a few buttons on the hand control. The LX850's default setting uses the pair of sensors built into the StarLock autoguider to precisely center each deep-sky object by offsetting from nearby bright stars. This process can be turned off, but it is completely automated and adds less than a minute to the GoTo time. It's very accurate, and extremely useful when working with faint deep sky objects which are invisible to the eye.
Within 15 or 20 seconds of slewing the LX850 to a target, StarLock will automatically find a guide star and begin tracking on it. You can then open your camera's shutter start imaging.
Tests show that the LX850's tracking accuracy is very good indeed.
The mount can also be used with any modern autoguider. It is plug-and play compatible with guiders connected to the "aux autoguider" port, the StarLock system automatically deferring to command sent to this port.
The Meade LX850 SCTs are corrected for off-axis Coma, but retain field curvature. A number of professional reviewers have confirmed this. Such a curved focal plane could cause softness at the edge of the field of view. But in tests, the scope was found to produce sharp images up to at least 10mm off-axis.
The similarly-priced optical tubes in the Edge HD series by Celestron, promise edge sharpness over a wider area, backed up by data published by Celestron.
No tests directly comparing the two brands have been published, but available evidence would suggest to this writer that the Celestron 9.25 Edge HD telescope remains the most accomplished SCT available to the amateur for wide field astro imaging. My review of the Celestron Edge HD range is here.
SCHMIDT-CASSEGRAIN TELESCOPES - FOR AND AGAINST
Schmidt-Cassegrain telescopes are wonderful system telescopes. The major manufacturers, particularly Celestron and Meade, provide a wide range of accessories for the telescopes.
Other advantages are the closed tube, which reduces air currents and prevents dust and corrosion of the optical elements; the folded optical design which makes the scopes compact for their aperture and focal length, and so good portability and ease of mounting.
The main disadvantage of the schmidt-cassegrain is the size of the central obstruction, which is typically 34% to 36% of the diameter. This is not just a case of some light loss; as explained elsewhere
central obstuctions of that size can reduce the telescopes resolution, so that, in resolution terms, the SCT will have the resolution of a smaller scope of other designs. But the reduction is not a deal-breaker, and must be balanced against the convenience of the SCT desgn, having so large an aperture in a folded-optic, compact tube design.