MEADE ETX-90EC AND AUTOSTAR, PART 2 Last updated: 31 July 1999

This is a continuation of my earlier report on the ETX-90EC and Autostar. This report updates some comments made there and provides some additional comments.

Over the past two months I have been working with Meade on improving the Autostar software. Like many users, I had problems with the initial release of the Autostar software. During my visit to Meade on 18 June 1999, I gained more insights into the workings of the ETX (and DS) line and Autostar. What follows are some notes from that visit.

The HOME position is important for three reasons: 1) keep internal cabling from wrapping around the axis, 2) avoid hitting one of the hard stops during operation, and 3) give the Autostar a known starting point in 3-dimensional space. For non-solar system objects, the Autostar can correct for many HOME position inaccuracies in ETX base leveling; true north pointing; and some date, time, and location errors. For solar system objects, date and time become important parameters due to the continual movement of these objects. However, it is possible to be "too careful" when establishing the HOME position, especially in Polar mode with the Easy Alignment. As we know, version 1.0 of the Autostar software had some errors which were corrected in 1.1. With 1.1 successful alignments were usually quick alignments rather than the careful, time consuming setups.

One other factor that affects the accuracy of the Autostar alignment is the condition of the batteries. A low battery level can create situations where the encoders miss information during slewing. This can result in alignment stars or selected objects not being accurately positioned in the finderscope or eyepiece FOV. If you are concerned about getting an accurate alignment, do a quick battery level check using the Autostar. To do this, hold the MODE button down for a couple of seconds and then release. Use the up scroll arrow to display the battery level. Replace the batteries if the level is down to around 80% and especially if the level drops even lower while slewing the ETX with the Autostar. Alternatively, you can use the Meade AC Adapter (part #541). The adapter comes with the 115v AC converter box and a 25-foot cable to connect the ETX-90EC. The cable can also be used to provide power using a vehicle's cigarette lighter socket. Meade supplied one of these to me and I used it instead of the batteries for most work with the ETX and Autostar (even though the Autostar reported battery level at 100% for a long time).

The following technique was offered to do the initial Polar mode alignment. Put the ETX into the Polar HOME position. Unlock the RA axis and rotate the ETX in RA while looking through the eyepiece. Physically move the ETX to point left or right and/or slew the DEC up or down until stars viewed in the eyepiece appear to rotate around a central point (the pole) within the eyepiece FOV. With this done your ETX is now pointing at the true celestial pole. Now put the ETX back into the RA HOME position but don't change the declination. Then do a One Star Alignment. This will give you the most precise polar alignment possible.

With Autostar versions prior to 1.2, I had problems getting consistently good results in the Alt/Az mounting mode and almost 100% failures to get good results in Polar mode. In Alt/Az, following an Easy Align I would get excellent GO-TOs for all selected objects. Then I would start over and none of the selected objects would appear in the 26mm eyepiece field-of-view (FOV). In Polar mode it was even worse; generally I would have no successes. Meade even checked out my ETX and Autostar and doing real night time tests got good results even though I did not. Consistency and repeatability seemed to be the issue. However, that was the past.

With version 1.2c I have had good results in both Alt/Az and Polar modes. Even though alignment stars might be outside of the finderscope FOV, once aligned, selected objects were generally within the 26mm eyepiece FOV. In general, when there were pointing errors following alignment, they were minor. That made using the ETX-90EC and Autostar a joy!

OK, so what changed? Well, based upon user feedback (yours and mine) Meade determined that there was a certain condition (the details of which are not important) that could occur that the Autostar software was not handling. The software was revised and it now seems to properly handle this condition.

As with a lot of software, bugs can and do get introduced with new revisions. As Meade identifies bugs and gets them fixed they are releasing new Autostar ".ROM" files on their web site. Place these in your Autostar "Empherides" folder and run the Autostar Updater software.

I have experienced some oddities when updating the Autostar software. Fortunately, there is way to recover from bad uploads. One time the Autostar locked up for some reason and could not be RESET and would not power-on normally. Meade supplied the magic keystroke to put the Autostar in a safe load mode (Enter/Scrolldown at power on). In this mode the Autostar software can be downloaded. Another time I received a "failure to erase bank 15" error. When I clicked OK, the software tried to initialize the Autostar. This seemed to take a long time and when I came back to the computer, the Autostar had turned off (power, AC, was still on the ETX). Cycled the power and the Autostar came up. Not knowing what condition it was in I redid the download. It went well this time but when it was done I did notice that the back of the Autostar (behind the display) was VERY warm and that the left half of the display was hard to read (seemed almost blurry with a white-ish background). I powered off and let it cool. Then it was OK and worked normally. On occasion during actual use, I have had the Autostar stop well short of the selected object. Starting over cures the problem. Other times there have been alignment failures. Again, starting over cures the problem.

In my initial report I stated that:

Until all users can report positive results "out of the box", adding the Autostar Computer Controller is a gamble that may result in the wonderful thrill of seeing many astronomical objects with a minimum of effort or it may result in total frustration. But there should not be any hesitancy about purchasing the standard ETX-90EC. It remains an optically fine astronomical instrument, and with the addition of the motorized controls will give even the casual amateur astronomer many hours of viewing pleasure.

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