Meade LX200 Pointing Accuracy Test Results
June 6 - 7, 2001
Set up: 10-inch LX200 f10, leveled, Alt-az, two-star alignment (Regulus #1, Vega #2), 12 mm illuminated reticle (about 10 arc-min field of view).
Note: I did NOT re-synch on any other star after completing the two-star alignment. Slew speed did not affect results (either 3 or 8 speed).
I posted these results to the MAPUG list (Meade Advanced Products User Group) and the reply I got from some experienced users is that my pointing accuracy is pretty average and in line with other LX200 telescopes.
From To Separation Pointing Error Vega Deneb 24 deg 2.5 arc-min Vega Altair 34 deg 3.5 arc-min Vega Arcturus 59 deg ~ 20 arc-min Arcturus Altair 81 deg 3 arc-min Altair Denebola 115 deg ~ 23 arc-min Denebola Deneb 106 deg 1.3 arc-min Deneb Vega 24 deg 1 arc-min
June 8 - 9, 2001
I set up the LX200 in equatorial mode with the Meade Superwedge. Here are the results after synching on Antares:
From To Separation Pointing Error Antares Arcturus 56 deg 6 arc-min Antares Vega 72 deg 15 arc-min Antares Denebola 79 deg 8 arc-min Denebola Arcturus 35 deg 9 arc-min Arcturus Antares 56 deg 1.5 arc-min Antares Alphekka 54 deg 9 arc-min Then I re-synched on Alphekka:
From To Separation Pointing Error Alphekka Arcturus 19 deg 4 arc-min Arcturus Vega 54 deg 10 arc-min Vega Deneb 23 deg. 17 arc-min Deneb Altair 38 deg. 14 arc-min Then I refined my polar alignment by using the "iteration" method as described in the MAPUG achives.
I did four iterations between Polaris and Altair. By the third iteration, Altair was 1 arc-min from centre.
Before starting my next set of tests, I synched on Altair. Here are the results:
From To Separation Pointing Error Altair Vega 34 deg 8 arc-min Vega Deneb 23 deg 7 arc-min Deneb Altair 38 deg 1 arc-min Altair Arcturus 81 deg 14 arc-min Arcturus Deneb 80 deg 9 arc-min Finally, I re-synched on Deneb. Here are the results:
From To Separation Pointing Error Deneb Vega 23 deg 5 arc-min Vega Altair 34 deg 9 arc-min Altair Arcturus 81 deg. 16 arc-min Arcturus Mars 69 deg. 14 arc-min My comments on the results:
These results are FAR from Meade's advertised centering accuracy: "...LX200's place objects dead-center in the field of view, first time, every time, to a pointing precision of 2 arc-minutes or better..." (quoted from their LX200 ads).
I achieved better results in alt-az mode (i.e. without the Superwedge). Some things that come to mind that may explain the poorer accuracy in equatorial mode:
- My polar alignment was not as good as it could have been
- My scope is quite a bit off balance, especially in R.A.
- I did not tighten the wedge's tilt-plate bolts very hard (perhaps this allowed for some shift)
Comments from some MAPUG experts:
Although my results are not great, they are average. I was told I should be satisfied with the above results. As soon as I can, I will repeat the tests and I will make sure to take care of the above issues. Stay tuned!
July 8, 2001
Balanced the telescope, polar aligned and tightened all wedge knobs well. The first polar alignment was on Polaris --> Vega, but the pointing accuracy was not that good. I did not like the fact that the LX200 chose Vega as the alignment star, so I re-did the alignment, skipped Vega and synched on Altair. The pointing error was as follows:
From To Separation Pointing Error Altair Deneb 38 deg 5 arc-min Altair Arcturus 81 deg 13.5 arc-min Altair Markab 47 deg 2.5 arc-min Markab Alkaid 106 deg 17 arc-min Altair Vega 34 deg 4 arc-min Vega Alphekka 54 deg 10 arc-min Altair Alphekka 63 deg 10 arc-min
Keep in mind that the field of view of the Meade 26mm eyepiece (in my 10-inch f10) is 13.5 arc-min from center-to-edge, therefore all the above slews landed the target inside the field of view of the 26mm eyepiece, except the slew from Markab to Alkaid (a 106 degree slew!). On the other hand, my LX200 is far from the advertised 2 arc-minute accuracy.The above results are a little better than my previous tests. Still, I cannot beat the pointing accuracy I got when set up in alt-az mode. I also observed M57, M13, M11, M27 and all were within the 26mm eyepiece field of view.
The question that remains unanswered is - did the pointing accuracy improve slightly due to balancing the telescope and by tightening the wedge knobs or did it improve slightly because of a better polar alignment? Only more testing will tell!
July 21, 2001
Set up in Alt-az mode to see if pointing accuracy is better in Alt-az than with a wedge. Two star alignment done on Alkaid and Altair. I then did a GOTO to Alphekka (just 1 arc-min off!) and synched on Alphekka. See the chart below for pointing accuracies:
From To Separation Pointing Error Alphekka Altair 62 deg 1 arc-min Alphekka Vega 39 deg 7.5 arc-min Alphekka Deneb 63 deg. 7.5 arc-min Next I synched on Altair:
From To Separation Pointing Error Altair Deneb 38 deg 7.5 arc-min Altair Markab 47 deg 7.5 arc-min Markab Alkaid 106 deg 6 arc-min Altair Vega 34 deg 7 arc-min Vega Alphekka 54 deg 1.75 arc-min Altair Alphekka 63 deg 1.3 arc-min The above results confirm that it's easier to get better pointing accuracy when set up in Alt-az mode. The accuracy is better and the error is more consitent than when set up in polar mode (ie with a wedge). Further above you can see that when set up in polar mode I was getting errors of 4 to 20 arc-min, but in Alt-az mode I was getting an error of just 1 to 7.5 arc-min.