IMPORTANCE OF BALANCE
Subject: Balancing Your Fork-mounted ETX or LX 90 is Crucial Sent: Thursday, May 10, 2001 01:29:37 From: email@example.com (Clay Sherrod) THE IMPORTANCE OF BALANCE IN THE FORK-MOUNTED ETX AND LX 90 TELESCOPES Lately, with more and more accessories for the ETX and LX 90 telescopes being offered in the marketplace, I am getting inquiries regarding the importance of BALANCE of the telescope and its mounting for proper use and continued good service of the telescope system over time. Also, I am beginning to see coming in for my Supercharge tune ups MANY telescopes whose mountings are suffering badly from excessive wear and slop due to use in severely imbalanced conditions over time. Indeed, improper balance of the fork-mounted ETX or LX 90 telescope is crucial and definitely WILL adversely affect accuracy, GO TO's tracking and random slewing conditions if balance is not maintained in BOTH axes. In addition, it will greatly shorten the precision and life-expectancy of your tracking system as well. This is particularly true, more difficult difficult to achieve, and perhaps more crucial when your telescope is mounted in POLAR mode. In Alt-Azimuth, care must be taken for good balance (you want a little "load" on the front of the optical tube assembly to assist in maintaining minimum backlash of the mechanical aspects of the drive/slewing motors), but primarily in the ALTITUDE axis. In Polar, balance should be achieved in both Declination (altitude) and Right Ascension (azimuth) axes and is not easily done, as the center of gravity will shift on you in different parts of the sky. This is particularly true when heavy accessories are added to the front or back of the telescope optical tube assembly, such as the electric focuser, a piggybacked camera or guide telescope, a heavy eyepiece (such as Meade's heavy 14mm UWA) or a camera body mounted at the prime focus of the telescope. It does not matter whether you are using the ETX 90 or the LX 90.....balance is important and crucial to the life of the mechanical parts of your telescope! In Alt-azimuth mode, you must simply unclamp the altitude ("up-down") axis prior to observing and check to see if the telescope tube unduely wants to swing one way or another too freely; merely add an appropriate amount of weight to the opposite end (usually the front end if a camera or other heavy accessory is added) until the excessive weight seems to be compensated for. The fork mount balance point will CHANGE as your direction pointing changes in the sky in Polar mode and hence the sliding counterbalance systems are necessary in the LX 90 to compensate for this shifting center of gravity. On my LX 90 I have an 80mm ST refractor piggyback, the #1206 heavy focuser, the 2" diagonal and the heavy aluminum Meade dew shield (plus a few tin cans hanging on it from time to time) and balance is always a problem and will most definitely cause poor tracking as well. If using Polar - and more and more ETX and LX users are doing just that - adjust your balance according to which position of the sky you are in; since you cannot unclamp your LX 90 once you have gone to a position (you will lose your alignment) you must do this through trial-and-error; I do this in the daytime and make notes of what is required in "southeast", "near-meridian", "northwest" and so on, sketching little diagrams of what weight is necessary where after a GOTO....then I merely add on the weight while the drive is running after each GO TO and the scope does fine. You will notice from some trial-and-error balance testing that many times you may be well balanced in declination, yet your right ascension (your main driving axis) is severely out of balance....this can be particularly true when pointing the telescope far southeast or southwest with heavy accessories on the eyepiece end. If you do not balance properly not only is your accuracy and tracking affected, you will slowly wear out the small motors, add looseness to your gear trains and cause excessive slow in your clutches. Take care of your ETX or LX 90 telescope by assuring proper balance at all times and in all positions! P. Clay Sherrod Arkansas Sky Observatory
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