The following describes an initial description of problems seen with Autostar firmware version 2.1Ek, dated 12 Dec. 1992 (sic), called "2.1Ek" below. The notes refer to an EXT-90EC using an Autostar #497 handbox and Meade #1244 Electric Focuser. The firmware was installed using Autostar Updater V2.4 and no patches have been applied to the firmware save for two items.
First, a user-defined asteroid was entered via the handbox. This is the entry used to allow the scope to track the Sun. Second, three third- party tours were added from the following web site: "Astro & ETX" http://www.carmine.demon.co.uk/astro/astro.htm
The tours are "Double Club", "Caldwell Cruise", and "Tonite's Jewels". The last tour has revealed at least two problems with 2.1Ek. All three tours are interesting tours in their own right and I appreciate the effort Mark Crossley put into writing them.
The telescope was operated in Alt-Az mode and uses the following
Lat.: 40-15 N Long.: 75-18 W Time: UTC-5.0 hrs (EST)
ITEM: Un-commanded two-axis slewing
This is an intermittent problem. It is characterized by simultaneous motion in altitude and azimuth. It appears to be happen during attempts to slew in azimuth alone (that is, either the <- or -> button alone is pressed). It seems to happen more often when the slew rate is a multiple of the basic sidereal rate (that is, after pressing one of the number buttons 1 through 5) as opposed a rate expressed in degrees per minute (buttons 6 through 9). The azimuth and altitude motors appear to use the same rate, causing the scope to track at a 45 degree angle to the desired motion. In all instances observed to date, the altitude motion is always upward and not downward.
This un-commanded motion severely impairs observing.
At present, the only possible work-around is to slew the scope using higher slew rates (6-9) to move away from and back to the desired object. The un-commanded two-axis motion may or may not happen when re- centering the object.
ITEM: Snap-back slewing
This is an intermittent problem. It is characterized by the telescope slewing back to a prior position after adjusting the telescope to re- center the current object. The problem does not occur when slewing over relatively long distances but only when adjusting the telescope's position to adjust an object's place in the field of view (FOV). The prior position often appears to be the last place the telescope was aimed after slewing to the object or, in some cases, after aiming has been adjusted slightly. The rate of motion may be proportional to the distance from the prior position; smaller distances mean the telescope moves more slowly, longer distances mean the slew rate is somewhat faster. This may be a subjective judgement and not what is actually happening. There have been suggestions that snap-back slewing occurs more often when observing planets than other objects. Recent extensive observing showed the problem to be present when observing a series of double stars as well as Jupiter and Saturn. The problem continued after the telescope was re-aligned.
This un-commanded motion significantly impairs observing.
The same work-around suggested for un-commanded two-axis motion seems to work for snap-back slewing. In some cases, using slower slew rates (1- 5) and moving the telescope away from and back to the object may allow the object to be successfully centered.
ITEM: Invalid destination position
This problem has been, so far, observed in one specific case but the problem can be repeated at will. The problem is characterized by motion that appears to direct the telescope 180 degrees in altitude and azimuth from the actual location of an object selected by the tour command "AUTO SELECT USER".
WARNING: Keep all optics covered if doing this test outdoors! There is some risk of sweeping past the Sun as the telescope moves. This motion could cause either permanent blindness or equipment damage. If you are not comfortable following the steps described below, DO NOT DO THEM!
Using the "Tonite's Jewels" tour, the location given above, and using the following time: 12:00:00 30 Jan. 2001, allow the telescope to point at the first two targets (the Moon and Venus). Pressing the MODE button advances the tour and pressing the GOTO button points the telescope correctly.
The handbox display shows the target's name on line 1 and the object's location (RA and Dec.) on line 2. It's also possible to use the scroll buttons to move through other data for each object.
WARNING: The following step can cause damage to your optical tube assembly (OTA) and altitude drive train. Be ready to stop the telescope's motion by either turning the telescope off or pressing the 0 button! If you are not comfortable with the following step, DO NOT DO IT!
On pressing the MODE button, the next object is the open cluster M2, at 21:33:00 -00d49m00s. The telescope begins to move in the appropriate directions, stops, and begins to move away from the proper position. Azimuth motion stops when the telescope is pointing 180 degrees from the proper azimuth. The OTA elevation continues to drop until the OTA strikes the telescope base. Whether the telescope would attempt to return to the correct position is unknown as I, to protect the telescope, stopped all motion.
It is possible to correctly point the telescope at this position by using the menu items OBJECT \ DEEP SKY \ MESSIER to select M2. The tour sequence (Moon, Venus, and M2) can be duplicated with manual entries (that is, using the OBJECT \ SOLAR SYSTEM \ [Moon or Venus] menu items followed by selecting M2 as described above). The telescope will move appropriately and does not try to point the back of the OTA towards M2, as happens from using the tour Tonite's Jewels. Using the Meade- supplied tour Tonight's Best, it's also possible to duplicate the three steps described above (although Tonight's Best steps through several objects before offering M2 - I skipped over the intervening objects and used only the Moon, Venus, and M2) without undesired slewing.
Tonight's Best uses the object type and name command (e.g. "MESSIER 02" for M2) to point to an object. Tonite's Jewels uses AUTO SELECT USER to display different comments about an object than those stored in the basic 2.1Ek object database.
The problem seems to be caused by one or more of three factors. The tour file is very large and may not fit if several tours are already in place. It's possible that the tour's size is a factor in this failure. Another possible cause is the extensive use of the tour command AUTO SELECT USER. See the following problem section for a related problem. The problem may also be tied to the object's position and particularly its declination in degrees (-00d) and the declination of Venus (+00d16m for 12:00:00 EST 30 Jan 2001). Changing signs while holding the value of the degrees (zero) constant might be uncovering an arithmetic error in 2.1Ek.
This problem presents a severe risk to the telescope's OTA and drive trains.
There is no apparent work-around except to avoid tours making extensive use of AUTO SELECT USER commands.
ITEM: Line 2 text crawl doesn't reset
The Tonite's Jewels tour discussed above uncovered a second problem that can effectively disable the telescope. In the tour circumstances described above, the first two objects' position, description, etc. are taken from data included with the 2.1Ek databases. The scroll buttons roll through the position, distance, etc. for the appropriate object as expected. With M2, however, the data is supplied as part of the tour's argument to the AUTO SELECT USER command. When M2 (and subsequent objects) are selected by pressing the MODE button, the text in this command crawls across line 2 of the handbox's display as expected. On pressing GOTO, however, the Slewing... prompt shows briefly and then itís replaced by the descriptive text seen before pressing GOTO even though the telescope is still in motion. More importantly, if the MODE button is pressed repeatedly to exit the tour or to use the handbox's electric focuser function, line 2 of the display continues to display the descriptive text for the object reached in the tour at the time the MODE button was pressed. The focuser, RA & Dec., etc. displays cannot be reached by holding the MODE button down for two seconds or more. In fact, 2.1Ek never responds to an extended MODE button press. 2.1Ek does move up through the level of menus until line 1 shows the Select Item: prompt but the telescope doesn't respond to attempts to drill down in the various menu options. Attempts to access the telescope from PC telescope control programs such as SkyMap Pro V7 fail with a message similar to "unable to communicate with telescope" even though, prior to attempting to leave the tour, the telescope was communicating with the program (as indicated by a moving "telescope position" cursor. The telescope is disabled once 2.1Ek reaches this state. The only recovery technique is to turn off the telescope, return it to the home position manually, turn the telescope on and re- initialize it.
The problem may be the result of the same three factors discussed above.
This problem significantly impacts observing.
There is no work-around except to allow the tour to run to completion or to step through each object by pressing the MODE button briefly.
ITEM: Focus during satellite tracking changes slew rate
This problem happens while the telescope is slewing to track a satellite. Pressing the "0" button (to adjust focus using the Meade Electric Focus motor) causes the azimuth and elevation motors to audibly speed up. Pressing 0 a second time resumes the initial tracking rate(s). Repeating a cycle of enabling focusing with the 0 key and disabling it with the 0 key three more times takes the motors through progressively slower rates and on the fourth cycle the motors stop altogether.
It appears that each cycle of pressing 0 presents the focus motor rate to the slew motors and each subsequent cycle steps through the progressively slower focus motor rates. That is, the rate seems to step through "Fast", "Medium", "Slow", and "Fine" rates in descending order.
The work-around is to not use the focuser while tracking a satellite.
This problem adversely impacts satellite tracking with the telescope.
ITEM: Slow button detection
This problem is most often seen while initializing 2.1Ek. For example, when entering the date, pressing the proper digit may not produce a change on the display. If two buttons are pressed in quick succession, the first button press may be ignored and the second button press is displayed where the first digit was expected. If the handbox displays 23-Jan-2001 and the desired date is 31-Jan-2001, pressing the "3" and "1" buttons may result in the date "13-Jan-2001" or, sometimes "11-Jan- 2001". Although the problem is described during setting the date, it can happen during any data entry process.
Either the handbox's processor is too busy to detect the button presses or processes them incorrectly.
The work-around is to press one button at a time, verifying each button press before attempting the next button press.
This problem makes the handbox difficult to use.
ITEM: Contrast values lost at start-up
When initially powered up, the handbox display contrast setting goes to a value that makes reading the display difficult, particularly because the display is in "full brightness mode" at this point. The contrast is reduced to the point where segments of the display that should be dark are not dark enough to properly form characters. It is not the use of full brightness, per se, that is the problem but the loss of character contrast. This problem persists after the initialization process is complete and the display is no longer at full brightness. Characters remain hard to read at reduced brightness.
The work-around is to view the display from a shallow angle relative to the display plane until the last bright start-up option (daylight savings time yes/no) is made. At that point, the UTILITIES \ CONTRAST ADJ. menu entry can be used to re-set the proper contrast level.
This problem makes reading the Autostar display difficult.
ITEM: Park utility changes
The Park utility accessed by UTILITIES \ PARK presents a potential problem for telescope users who do not leave their telescopes in a permanent location. Specifically, if Park is used to stow the telescope at 0 degrees altitude and azimuth, the telescope is not returned to the home position (that is, with the OTA approximately 120 degrees clockwise from the counterclockwise azimuth motion stop). The Autostar manual does say (and, in fact, italicizes) that "no alignment is required" on a subsequent start up. For those users who, in fact, use a portable tripod and move their telescope to an observing position, it's possible to do an alignment without enough room in the telescope's range of azimuth motion. The problem will not become apparent until the telescope attempts to slew clockwise and reaches the end of travel while the positioning software (mistakenly) assumes another 360 degrees of travel are available.
The work-around is use Park, release the azimuth clutch, rotate the OTA to the home position, and re-lock the azimuth clutch. One possible solution is to give the Park command the option to slew to the home position (alignment required at the next start-up) or slew to the closest 0 degrees altitude and azimuth (alignment not required at the next start-up).
This item is more of a matter of an enhanced feature than a limitation to telescope function.
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