Equipment
Meade
RCX400 10" Ritchey-Chretien
In October 2005 I purchased a Meade RCX400 10" Ritchey-Chretien. It has the same GOTO and PEC function as the LX200 but has a number of advantages for the CCD imager. The Ritchey-Chretien optical design has a fixed primary mirror, so there is no possibility of the mirror moving during a long exposure and affecting focus and/or image position. Focus is achieved electronically using the Autostar to control the movement of the secondary mirror so very precise adjustments are possible with no shift of the image. A USB hub is provided on the OTA which allows up to three CCD imagers/autoguiders to be connected, eliminating dangling cables and cable wrap which may affect tracking. The USB hub is connected to the PC via a single cable attached to the base of the telescope. This USB attachment also allows the PC to control the telescope using the supplied Autostar suite or other third party software, eliminating the need for the serial cable required on the LX200. All cameras and the telescope can now be controlled from one USB connection to the PC. The RCX400 also supports electronic collimation via the Autostar hand controller or PC with Autostar Suite. Good collimation is very important if you want to produce good images, especially of the planets. On the LX200 collimation of the secondary mirror has to be done by manual adjustment of screws on the secondary. This can be very awkward as you constantly have to move from the eyepiece to the secondary and back making small adjustments until collimation is achieved. With the RCX400 you just use the arrow keys on the Autostar to adjust the secondary mirror while looking through the eyepiece the whole time. It makes collimation a whole lot easier. Another useful feature is the built in heater around the corrector lens, which removes the need for third party dew removal systems. The RCX400 comes with a much sturdier tripod than the LX200 helping reduce vibrations during a CCD exposure. Meade has produced a new Superwedge for use with the RCX400. However I found the RCX400 and its new tripod fits my old LX200 Superwedge perfectly and the combination works well. Overall, my impression of the RCX400 has been very favorable so far.
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In March 1999 I added a Meade LX200 10" SCT to the equipment used at Woodlands. Its main advantages over the 8 inch LX10 (other than aperture) are computerised GOTO, a more accurate RA drive with periodic error correction and sturdier fork mounts. I use this telescope as my main CCD imaging instrument The optics are excellent. I got stunning views of the Orion Nebula on my first night out. The GOTO works as advertised and is very accurate. The RA drive is indeed more accurate than the LX10. With the PEC trained I can take unguided exposures of 2-3 minutes without guiding. This improvement in drive accuracy over the LX10 has allowed me to take long duration exposures with far fewer guiding corrections. The LX200 is shown here attached to the Meade Superwedge. This is proving to be very sturdy and much easier to adjust than the LX10 wedge when performing precise polar alignment.
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The LX10 was the first telescope to be used at Woodlands, though I sold it a couple of years after purchasing the LX200. I found it to be extremely portable and easy to set up. Its optics (the same as the 8 inch LX200's) are excellent and the field tripod and fork mounts provide a very stable observing platform. I have seldom been troubled by any vibration even when taking CCD images. The LX10 has a DC regulated RA drive. This drive is perfectly adequate for visual observation. However, when taking CCD images the drive is only accurate enough to take exposures of approximately 20 seconds without the need to make guide corrections in RA. RA corrections can be accomplished on the LX10 by means of the (optional in the UK) hand controller. It can either stop the RA drive for Eastward correction or run the drive at 2x sidereal speed for Westward correction. With the addition of an optional DEC motor, the hand controller can also be used make 2x corrections in DEC. In my opinion the hand controller and DEC motor are essential items for anyone considering using the LX10 for astrophotography, as is the purchase of a guide scope or an off-axis guider. I believe the LX10 is excellent value for money as an entry level SCT which is capable of producing good astrophpotographs providing the user is willing to do a fair amount of guiding.
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The Meade ETX is a 90mm Maksutov Cassegrain Telescope. It is very compact making it easy to take aboard aircraft as hand luggage or backpacked to a remote dark sky location. It is fork mounted and has a battery powered motor drive for tracking in RA. The fork mount can be tilted equatorially by screwing three small tripod legs into the base of the RA drive. Polar alignment is achieved by extending the centre tripod leg to read your lattitude on the inscribed scale. The RA drive can be slow to engage after the RA axis has been locked but once it is going it tracks the sky well for visual obervation. However, the RA tracking of the ETX is much less accurate than the LX10 and, unlike the LX10, the ETX does not have any means of making RA corrections using a handcontroller. This means that the ETX is only suitable for taking CCD images or photographs with exposure durations of a few seconds. Any longer and star trails will be evident. This restricts astrophotography with the ETX to bright objects such as the sun, moon and planets. The ETX has very good optics and so far has given superb lunar views (in my opinion better than the LX10) as well as good views of M13, though, as expected, M13 was not as highly resolved as with the LX10. We mainly use the ETX for solar observation and when there isn't time to set up the bigger LX10 or LX200. Its portability makes it ideal for us to take away for use on vacations as both a terrestrial and astronomical telescope. As a terrestrial telescope it is excellent. I have been able to see lights in peoples' living rooms on an island 2 miles offshore! The ETX could also be used as a guidescope for either the LX10 or LX200 although I have not used it for this purpose yet. As well as the solar filter we have bought a couple of other accessories for the ETX. The first was a JMI right angle finder. The standard straight through finder is virtually unusable when using the ETX on its equatorial tripod legs as the finder eyepiece is too close to the ground or table top to be able to look through it unless you are viewing an object very close to the horizon. The second accessory was a JMI wedgepod. This is an adjustable height tripod with an equatorial wedge designed to fit the ETX. This lets you use the ETX as a fully fledged astronomical telescope as it provides a much more rigid mounting than the standard screw in legs and can be adjusted to a comfortable viewing height. |
