David's Astronomy Pages 12" LX200 GPS/ R Observatory Construction   Home Page   Telescope Accessories

Autostar II Settings

Back to Top

LX200 GPS/R Notes

• Autostar version 4.2g 
   
• Only the RS232 port next to the HBX port can be used for upgrading the handbox.
  
• Newsgroup  postings suggest that GPS-UTC Offset should be set to 0 (not the +13 default value)
  (GPS-UTC Offset is not described in the LX200R User Manual. It lies on the Setup menu, between "Setup/Daylight Savings" and "Setup/Telescope). The parameter was originally to allow for the fact that the precise "satellite" time transmitted by the GPS system has drifted compared to UTC time which has "leap seconds" added as the earth's rotation slows. However the majority of LX200GPS scopes and all LX200R scopes use self-correcting GPS receivers. Leaving a value of +13 is understood to produce a 13 second clock error when using a GPS fix, leading to pointing error of 13 * 15.0417arcsec/sec = 3.25 arcmins (at the celestial equator, but diminishes by the cosine of DEC as poles are approached) - postings by Dick Seymour  [ newgroup item ]   To test- *your* Autostar. let it take a Fix, and then compare its time against a to-the-second time standard.
  
• When not using a GPS Fix at Startup  (GPS Alignment = Off), time be entered correctly at start-up (AutoStar will try to use a default value of ~ 20:00 hrs (not sure why time isn't retained between sessions ?).  Unlike the Classic LX200, the newer GPS and ACF/R models with Autostar have no provision to keep time and will always revert back to the last date and time entered during that power cycle.
  
  The Autostar only -remembers- (across power cycles) dates which are set at the keypad, or via the GPS. Dates which are set via classic LX200 serial commands are -not- written to the Flash Memory.
  
  There is a new command :hIyymmddhhmmss# which sets the date and time and invokes other initialization procedures. It uses local
  time ( not known if that method gets written to Flash or not.)
  
• :gps#   returns the lat/long coords determined by the GPS
  
• If Scope is not Parked on Power-down, then the next time it is powered-up, the telescope will think: (a) that it is *in* the defined PARK position (even if it's not) (b) it will know that it was NOT parked, so will ask for alignment.
  
• To ensure quick GPS acquisition, park the scope with the fork arm with the Antenna 'higher' than the other arm - so that you maximise sky visibility.  Finder scope may interfere with reception and need to moved to RHS or taken off during GPS fix.  
  
  horizontal,pointing west puts the antenna in the best position for receiving GPS signals.
  
• Quality of the positional signal you receive is directly related to this, it's also called "Dilution Of Precision" (DOP). DOP values range from 0 to 50 with 50 being the worst. You can go to trimble.com and download their planning software along with the current satellite almanac (both are free), install it, enter your current location, date and the time you will be acquiring a GPS signal and it will provide you with graphs of the DOP. DOP values of <1.5 are understood to normally give a GPS confirmation in three asterisks.
  
• When Scope turns on it moves c. 15 deg W from its start-up (parked psition) in order to find/align its PEC sensor. If you park with your RA PEC ON, the next time you start, it wont do the spin. Even if you haven't done PEC, do a factory reset to zero the RA PEC and turn it ON. It has no effect on the tracking, but it stops the spin at boot after park.
  
• Change the GPS setting to acquire GPS at start-up rather than when first needed.
• Coin battery (CR2032) on the Autostar's main board, behind the power panel
•  
• Recommendations from Newgroups : do NOT attempt to "define" a Custom Park after a two-star alignment. Use One Star before doing the Define Park.   
  
  Try setting the PARK to "Use Default"[enter], power it down, power it up, slew it to put it in the "proper" Polar Home position and do a "real" One Star alignment (just tap [enter] to accept where it thinks Polaris
  
• Training Drives on Polar Mounted LX200GPS/R scope  :  Setup/Telescope/Train Drive ..if you're running 4.2g, setting the Targets to Terrestrial[enter] (which stops the motors) and doing the RA Train Drive.
• Getting Battery Level ;
   Send/do the following: (not the parts between the (parens))
  
  (a) :EK11#:ED#
  (b) if the returned string does not contain the word "Battery", then
  (c) :EK68#:ED#
  (d) go to (b)
  (e) ...after you get your answer, you might want to send :EK9#
  to escape from the Status displays.
  
  
• Remember, when training, to start the Dec or RA cycle with the right beginning. ie: If in RA, and the scope slews to the right at first, center your target in the eyepiece, then slew left, and carefully come back to the target and recenter. The, start the Training process. This is important, to remove the backlash at the beginning of the whole process.

        If you -overshoot-, slew back further than you have to, and -then- slew to center the Training target.

• Other links/info : Guide to Polar Alignment of a Meade LX200GPS Telescope by Dale Chamberlaiink
• LX200GPS Autostar Issues (MAPUG) 
• Software and Hardware Autoguiding Issues with the LX200GPS by David Suder 
• Precise Polar Alignment Boot Camp (incl LX200GPS 10" Case Study)   
• Autostar Menu
•  
• RA problems at startup - posting

• Back to Top

8" LX200 Classic Comments

My own experience and comments with regard to the 8" LX200 are in the process of being added here (please check back again soon).  All of the comments are my own. I hope that they will compliment and extend the advice and hints posted by other LX200 users.

• 8" LX200 - Good Points

• 8" LX200 - Bad Points

• Advice and Hints

8" LX200 - Good Points 

• The telescope is highly compact for its aperture.

• The front lens provides protection to the primary mirror (compare with a simple reflecting telescope or Dob where the primary mirror is at the mercy of the elements.

• It comes with a sturdy Tripod (and provides a firm viewing base until the time you can get a Pier).

• The scope allows high precision pointing and tracking.

• The LX200's GOTO facility allows quick access to finding planets and hundreds/thousands of stellar and deep sky objects.

• Periodic error in telescope tracking can be corrected for by 'training'.

• The scope can be controlled remotely from a computer using appropriate software if required.

• There are loads of accessories for the LX200.

• There is relatively large and active user group

8" LX200 - Bad Points

• Image shift whilst focussing the LX200 can be large - and annoyingly so. Whilst mechanical tuning of the focussing mechanism can reduce the amount of shift it doesn't seem to make it go away (use of an alternative focussing equipment - such as the JMI -NGS-F focusser - is considered a vital necessity).

• The stability of a telescope is only as good as its weakest point. The LX200 and equatorial wedge make a pretty stable combination, but play in the telescope's bearing where they attach to the forks seem to be the LX200's weakest point.   Doc G's comprehensive mechanical analysis of the LX200 gives a lot more info on mechanical stability of the LX200 (note: this external link will open in a separate window).

• The telescope's standard ViewFinder  is pretty useless - the cross-hairs can't be seen when viewing a dark sky (very little help for aligning the telescope to a star) and the absence of a right angle-viewer means its very difficult for looking at objects high in the sky. Trying to see Polaris can be a real pain in the neck ! (use of an alternative finding equipment - such as a Telrad Sight - is considered a vital necessity, you will need a 1.25" diagonal however).

• Fitting of the telescope direct to tripod (as used in altazimuth mode) is a highly awkward process. requiring balancing the telescope scope on top with one hand whilst screwing in a threaded rod into the base with the other  (fitting is much easier once an equatorial wedge is used and of course this gives advantages of allowing polar alignment).

Advice and Hints

• Choose your telescope size with care (8",10" or 12")
  Which LX200 scope size is best ? It depends ....
  The larger aperture provided by the 12" scope will generally provide better access to smaller and/or dimmer sky objects  (0.375 arc sec resolution vs only 0.56 arc sec for 8") but it's considerably heavier (telescope tube+fork weight  is 70% heavier than for the 8", 80 vs 41 lbs, tripod 57 vs 26lbs) and it's much more expensive (70% more expensive than 8").    
  Overall I would suggest that the 10" scope represents the best value (0.45 arc sec resolution, and only 15% more expensive than the 8").  
  The telescope's tube+fork mount is however still 40% heavier than for the 8" (58 vs 41 lbs) so if mobility is important (and unless you have a permament housing the mobility difference could mean the difference between using the scope and not using it)  then the 8" LX200 is probably the best buy.   
  It has been said 8" LX200 is a good match for the limited seeing conditions which we have in the UK, I can't comment on that myself, as I've only used an 8" scope.  The Meade specification suggests that the limiting visual magnitude of the 8" LX200 (Mag +14.0) is only mag 0.5 less than for the 10" scope and only mag 1.0 less than for the 12".   

• Try to get your LX200 set up on a permanent pier in an observatory of some form. 
  The pier saves a considerable amount of time at the start and end of each observing session. The observatory protects the telescope when not in use and gives some protection from wind during observing.   The observatory can also help block out the impact of direct light from street and house lights, provide some privacy for the observer and provide extra room for storing accessories & cases. Whilst there is some environmental and security risk to the telescope in keeping storing it outside of the house, I believe there is more risk to the telescope in carrying it outside and then inside again each time its used, especially if it's across any icy patio !

• Try to get the best alignment you can
  Once set up on a pier it is worth spending some time to get the very best alignment that you can.  Finding objects will be a lot more easy.   My original alignment has held up pretty well and for visual observation I can get by without any polar alignment checking at all (I just match to a suitable star and then I'm straight into observing).  However if you're needing high-precision pointing and tracking (eg for CCD astronomy) you will need to check the telescopes alignment more regularly.  

• Reduce the Slew Rate Setting down to 6.
  Whilst the 8" LX200 can slew quickly across the sky (up to 8 deg per second), the Meade drives make a lot of noise, especially on a quite still night.  Slowing down the slew rate using Telescope Option #9, makes a lot less noise. I find that a Slew rate of 6 gives the best balance between speed and quietness. Slew rate needs to be set at the start of each session.  (Slew is the term given to moving the pointing direction of the telescope from one part of the sky to another).

• Regularly check/correct the LX200's clock.
  The LX200's clock has a tendency to loose or gain time between observing sessions.  If it shifts by much the pointing accuracy of the telescope is compromised, so it is wish to check and correct the clock every so often and if you haven't used the telescope for a few weeks.

• Don't rely on compass alignment
  The legs of the Meade Tripod carry some magnetism and affect the compass that comes with the Meade telescope/equatorial wedge.

Back to Top