Simulated Home / Park Commands
Subject: Simulated Home Command - Solved? 
From: Dick Green <dick.green valley.net>
As discussed in a previous thread, the idea behind simulating the Home command is to facilitate a completely remote controlled
scope. Some of us CCD users with permanently mounted polar-aligned scopes would like to be able to operate the scope remotely
without having to manually perform the required computer alignment (sync) at startup (i.e., point the scope at a known star
and Sync.) The LX200 16" Home command allows the observer to "park" the scope in a specified position so that
the computer knows where the scope is pointing when the power comes on.
Well, it didn't take but a couple of minutes to determine that the problem might actually be a lot simpler than I and others
thought. First, it appears that the LX200 does in fact have a standard set of startup coordinates in Polar mode, just like
it does in AltAz mode. The scope always starts up thinking that it is pointing at the intersection of the Meridian and the
Celestial Equator. In RA/DEC terms, the startup RA is the local sidereal time (LST) and the DEC is zero degrees. I verified
this by positioning the scope's setting circles to 00HH RA and 0 degrees DEC, turning on the power, then calling up Vega and
doing a GoTo. The scope slewed right to Vega.
As previously mentioned, the scope slews a few minutes in RA at startup. As others have pointed out, it is searching for the
encoder mark on the worm gear. Depending on where the worm was in its cycle when the power was shut off, the shift can be from
0 to 8 minutes. However, the scope sets its coordinates *before* doing this shift, so that the RA reported by the scope after
startup is in fact correct (it's equal to the LST plus the shift.) If you nudge the scope back to its starting RA setting,
the RA will be equal to the LST. In other words, the search for the encoder marks does not invalidate the computer alignment.
This means that it is possible to simulate the Home command after all. Just slew the scope to the intersection of the Meridian
and the Celestial Equator, then shut the power off. The scope will be correctly Synched the next time it is powered up! It's
easier to slew to the AltAz coordinates, because they don't change with time. For remote observers using TheSky, you can do
this by calling up the Move To dialog box and specifying the Horizon-based coordinates of the intersection of the Meridian
and the Celestial Equator. The Azimuth is, of course, 180 degrees (for some wacky reason, Meade thinks the Azimuth of this
position is Zero degrees, which is what the hand control will report.) The Altitude is 90 degrees minus your latitude
Ah, yes, but there is one slight problem. Of course, the scope computes the Meridian's position, and all other RA coordinates,
from the LST -- and the LST is derived from the (oh no!) horribly inaccurate local time clock. I didn't have a chance to play
around with this tonight, but I suspect that if you simply update the scope's local time clock from TheSky after powering up,
the LST and RA will be adjusted correctly. If this is not the case, perhaps it would work to make note of the scope's startup
position as reported by TheSky (i.e., the number of minutes it slewed looking for the encoder marks), then slew the scope back
to the where it thinks the Meridian is (the LST), update the time, power off the scope, and power the scope back on.
Subject: Park Command
From: Dave Bair
Jim Waller wrote:
- > I've been lamenting the lack of a 'home' or 'park' command in the LX200 command
- > set. I remember someone saying that 16" LX200 has this command. If the 12" and
- > smaller has such a command, it's not documented in the appendix showing the
- > serial port control codes. Now I see how to do it. At the end of the night,
- > send the scope a code to go into guide speed and then send the code to slew
- > east. The scope will just stop where it is. At startup the next night, the
- > scope should know exactly (maybe) where it is. Send a the code to stop the slew
- > and start the observing run for the night. Does anyone know if the LX200 will
- > really respond this way?
If a simple 'park' type command is what you're looking for in your LX200, I may have a solution for you that is quite easy
and reliable. This requires/assumes that you will leave the scope mounted in the same position for a period of time and that
your declination circle is calibrated correctly. After you complete a night of observing, set your hand controller to read
your pointing position in altitude/azimuth. Now, slew your scope until the azimuth reading is right on zero (due south) and
cut power to your scope. I don't know why it assumes azimuth at south as opposed to north, but it does.
Now adjust your RA circle to read at the zero hour indicator and make a small mark on the scope housing at the zero position
on the outer scale of the RA circle. Now you can release the locks and put the scope in any position you like for covering,
etc. When ready to begin a new session and before powering up, carefully, manually set your declination to zero (OTA should
be level if in alt/azimuth mode) and lock in place.
Now, manually rotate in RA until your marks line up with zero, lock and power up your scope. Providing you were careful in
making your mark and your clock in the scope computer is relatively close +/- 15 seconds (another matter all together), you
should be able to simply use your GoTo command as if the scope was never powered down. This is the LX200's reset position each
time the computer is powered up. This method works great in my observatory.
Subject: LX200 Parking Tips--part 1 of 2
From: Paul Goelz <pgoelzeaglequest.com>
>I suspect all you need to do to park it with perfect accuracy the next time
>it is powered up is to set it to LAND mode before you park it. Then slew
>to zero degrees alt and az and turn it off
And further to this, I have now tried it and it works fine. This applies to ALT-AZ use. I have not tried it in POLAR mode.
To park the scope so it is aligned the next time it is used, try this (assuming of course that it is currently aligned and
tracking OK):
- Place the scope in LAND mode. At this point, timing becomes non-critical, as the scope will continue to update it's view
of the sky even though it is not moving the OTA.
- Slew to zero degrees ALT and AZ (easy way is to press MODE till you get to the RA and DEC display, press ENTER to go to
the ALT AZ readout, then press GoTo. The display becomes all zeros. Press ENTER twice, and it slews to zero degrees ALT and
AZ.)
- At this point, you can either leave the scope powered up or shut it down. Either way, it will be aligned the next time
you put it back into ALT-AZ mode, no matter how much time has elapsed....... well, I assume it doesn't matter. I have tried
it for about a half hour, but I would assume unless there is a quirk at the change of day, it should work no matter what,
up to the limits of the internal sidereal clock.
And for those of us who have forgotten how to get to LAND mode (like me!), it is the third choice in the ALIGN menu. You choose
it as the "alignment" method. Going back to ALT-AZ mode is the same...... go to TELESCOPE, ALIGN, ALT-AZ and press
ENTER. If you stop there, you have put it back into ALT-AZ mode without disturbing the alignment.
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Subject: LX200 Parking Tips--part 2 of 2
From: Mark Taylor <mctaylormindspring.com>
Park your scope:
If you'd like to leave your scope running continuously to keep alignment (in an observatory or at a long star party) you should
"park" it so the tracking action does not choke the scope/wires during the day.
You can safely switch your scope into "land" mode, and then switch it back to your chosen astronomical mode later
-- the scope will maintain its alignment even if you slew it with the NSEW keys in the meantime. And of course, "parking"
the scope like this minimizes the power consumption since the alt/az motors are off.
Some "parking" notes:
I've found that when I first go into land mode, the motors go quiet and the ammeter goes level as expected. However, if the
NSEW keys are used to move about, I'll sometimes reach an "edge" state where one or both motors are "buzzing"
but going nowhere. Simply tapping the directional keys in the reverse (or sometimes even same) direction will skip into the
"quiet zone" again.
Better visual images on planets:
"Park" your scope when you are using it to look at planets and lunar features. Sure you'll have to keep recentering
manually, but you won't have the vibrating of the alt/az motors fouling your view.
Alt/Az power-down parking:
- Switch your scope to "land" mode
- Slew to alt/az 0/0 (use the mode key to get coordinate display and press GoTo to enter coordinates)
- Power down.
- Powering up, the scope will expect to be at 0/0 (which it is if you haven't moved it during the powerdown)
- Switch back to alt/az mode.
GoTo will be fairly accurate if you were truly level to start with. If you want refraction correction, you'll have to do an
alignment, but at least you can easily GoTo the first star.
Subject: Parking the GPS & Classic Scopes --part 1 of 3
From: Tim Long <Timlong-family.com> Date: Jan 2005
The "classic" LX200 models do not have a park routine built into the hand controller. Some software, such as the
LX200 ASCOM driver, simulate parking the scope. What the ASCOM driver does is to set the telescope alignment mode to "LAND" then
slew the scope back to the home position. It is then safe to leave the scope without fear of it tracking and wrapping the cables.
The power may be left on or turned off, as required. I leave mine turned on all the time. When the ASCOM driver unparks the
scope, it will change the mode back to the correct alignment mode and resume tracking.
The GPS/AutoStar models are somewhat different, I believe. Those models do have a park function accessible from the hand
controller or by software. They also slew back to the home position but then require the power to be turned off. I've seen
some discussion that suggests it might be possible to recover a parked AutoStar without having to turn the power off, but this
doesn't seem to be a well documented procedure, at the moment.
Either way, parking is something you do when you're finished using the scope. The advantage of parking the scope is that
it is always in a known position. Whether you turn the power off or leave it on, the next time you use the scope, you will
just be able to unpark and start observing, without the need to perform the alignment procedure.
----------------------------------------------------
Subject: Parking the GPS & Classic Scopes --part 2
From: Al Arduengo <aarduengosbcglobal.net>
I don't switch to land mode. I simply GoTo alt=0 and az=0. When it gets there, turn it off. When I turn it back on, alignment
is almost not necessary. I usually do this when I set up in the back yard for several days at a time.
----------------------------------------------------
Subject: Parking the GPS & Classic Scopes --part 3 of 3
From: Tim Long
There are a couple of potential pitfalls with not going to LAND mode, which will affect different people to a greater or
lesser degree depending on circumstances.
1. When the telescope is in POLAR or ALTAZ mode, it is tracking at sidereal rate. Therefore, if you slew to Alt=0, Az=0,
when the telescope reaches that position it will resume tracking. If you are really quick on the power switch, it will not
have moved too far, but it will almost certainly have moved a little bit. So when the power actually goes off, the scope will
not quite be at Alt=0, Az=0. This means that when you switch the scope back on, it will not quite be in the right place. Over
time, this error will accumulate. If you're using the scope visually then the chances are you occasionally SYNC the scope so
you can probably live with that, but the problem could be avoided by switching to LAND mode, which stops tracking. The ASCOM
driver for LX-200 uses this technique to good effect, and also supports parking in a non-default position, which can be quite
useful.
2. If the scope is permanently mounted inside an observatory and left permanently powered on, then switching to LAND mode
is about the only safe way to stop tracking. It is safe if there is a power failure, as the scope will power up in the mode
it was last set to (LAND). Conversely, if left in POLAR or ALTAZ mode and there is a power outage, when the power is restored
the scope will continue tracking and will wrap the cables if not caught in time. There is a well known dome controller that
uses a 'reverse slew' to simulate parking and it definitely suffers from this problem.
Subject: Parking the LX200 --Leveling Critical
From: Stephen Speicher
- Paul Goelz wrote:
> >From the tests I ran the resulting accuracy when switching _back_
> >to alignment mode from land mode, turned out to be a function of
> >how well leveled the scope was. The amount of time in land mode
> >was, for all practical purposes, irrelevant.
> >Therefore, if the scope is correctly leveled and permanently
> >mounted, land mode is definitely the way to go.
- > A better test would be to do this at night with a good two star alignment,
> and I have not done that. I seem to remember someone who did it said that
> switching to LAND mode destroyed the two star alignment?
It was I who previously did that test and presented it here, as confirmation of a suspicion by another member as to the cause.
My initial experience was that after a good 2-star alignment, I switched to land mode for a period of time, and when returning
to alt-az the alignment was off. I wondered if the amount that the alignment was off was a function of the amount of time left
in land mode. Someone else thought that it might be a function of leveling.
So, I ran a _long_ series of tests. Each test was preceded by a 'good' 2-star alignment. First I did as good a job of leveling
as I could and experimented by varying the amount of time (from minutes to hours) left in land mode and noted how far off the
alignment was when switching back to alt-az. Then I experimented
by varying the leveling in degrees from my best attempt to grossly unlevel, while fixing the amount of time in land mode.
As I stated before, the results were crystal clear. The amount of time left in land mode was irrelevant, but the degree that
the alignment suffered when switching back to alt-az, was clearly a linear function of the accuracy in leveling.
Subject: LX200 Park (LXpark) Software URL
From: Michael Conte <mcontecrosslink.net>
>Where can I get the LXpark (DOS program). See description below
You can find it at :
<http://www.mv.com/users/wje/astro.html>
Note: should open a new browser window over this one
-----------------------------------------
Subject: LXpark Description
From: Dave Schanz <dave23schvalleytranscription.com> Date: Jan 2002
I have used the LXpark program a few times. It's a very small DOS application but it runs in a DOS window in Windows. It simply
slews the scope to Dec 0 and RA 0 so the next time you power up all you need to do is sync on a star and have at it. It's a
convenience item by eliminating the minute or so it would take to manually enter the 0,0 coordinates into the hand paddle and
slewing to the park position. But, it's a whole lot more accurate than trying to move to the coordinates using the setting
circles.
I unzipped the program into a separate directory (I guess directories are referred to as "folders" now days) that
I created. I then created a shortcut to put on my desktop. The docs say to add the com port the scope is connected to to the
end of the LXPARK.EXE line which is easily done. Simply right click the desktop icon for LXpark created earlier and click on
"properties." In the window that pops up, click on the "Program" tab and add 1 blank space (using the spacebar)
and the com port number to the end of the CMD Line (without erasing anything else!).
It works fine with only one caveat - make sure you are connected to your scope at the time and that you specified the correct
com port or the program will hang and Windows will too. The included docs are very clear and helpful.
Subject: Advice on Parking the LX200 Classic--part 1 of 2
From: Doc G, Date: Jan 2002
I have followed this thread with some interest and make only a few additional points. When you short the East control pin,
you stop the computer from tracking the celestial sphere. But, I believe that the motors, both RA and Dec, are still fully
controlled by the servo system. Thus they can buzz and chatter from noise signals within the control loop. I think the same
is true for putting the scope into land mode and also true for any of the parking schemes I have seen used. (unless the electronics
are turned off) We know that the motors chatter when they are not driving the scope.
Thus, to save any wear on the motors and the gear trains, I believe you have to turn off the power to the electronics. I cannot
show what damage might ensue from leaving the power on all of the time. It may be minimal to none or it may be serious. There
is certainly some advantage to leaving the power on since the electronics compartments will remain well above ambient temperatures
and thus prevent condensation.
On the other hand, I doubt that there would be condensation within the electronics housings anyway. If this is a concern,
an external heater would be a good solution. These comments do not prove one way or another what should be done I fear. Still,
they show that the decision to turn the electronics off or leave them on is not an obvious one.
My inclination would be to park the scope and then turn it off. Note that parking is a different function in general from
stopping the scope. After parking, the scope needs to be initialized with some programed scheme to get it back into synchronization
when it is turned on.
Other factors might be considered as well. I would think it wise to park the scope with the OTA pointed horizontally so that
dust does not settle on the corrector. There may be other concerns about the positioning of the scope for long periods.
---------------------------------
Subject: Advice on Parking the LX200 --part 2 of 2
From: Bruce Johnston
And to compound the problems, remember that if it's always powered up, it's plugged in! And if it's plugged in and lightning
happens to strike nearby... powered up or not... possibly 'goodbye electronics'! (Been there; done that.)
Subject: LX200 Classic Parking Issues --part 1 of 3
From: Doc G, Date: Jan 2002
I like to distinguish between parking the scope and turning the scope off. This might be a fine distinction, but some have
suggested parking programs which move the scope to a specific position. If the scope is left on, one can then continue in
full
synchronization. They involve amazingly complex methods. Some of them even work.
These programs have the limit that when you turn the LX scope off, it does not remember where you left it parked. Subsequently,
when you turn the scope back on and it is in the polar mode, the computer thinks the scope is pointing toward the meridian
and declination zero. Whereas actually, the scope will be pointing where it was when you turned it off.
There is a very simple way to overcome this situation. It requires only that you point the scope toward the meridian and toward
any declination you like. That declination will usually be whatever is horizontal at your latitude. In the northern hemisphere
it would be a negative number like -30 or -43 degrees or something like that. Then turn the scope off.
Now when you turn the scope on, the computer will think the scope is pointing at the meridian and at Dec=0. The scope is actually
pointing at the meridian and the horizon. (which is wrong) All you have to do is move the declination the 30 or 43 degrees,
per the above examples, and it will be pointing to Dec=0. The hand paddle will say something like +30 or +43 degrees.
Then turn the scope off and back on. The scope computer will now think that the OTA is pointing at the meridian and at Dec=0.
Sure enough it is. You can now easily find a star with a GoTo and do an accurate synchronization.
This is a simple solution for a simple problem.
-------------------------------------
Subject: LX200 Parking Issues --part 2
From: Scott Pinkham
In files section of the LX200 Yahoo group I've posted an ActiveX control that can be used to control an LX200 or ETX scope
-- it might be helpful in this application. You can use it with Visual Basic, C, etc... (anything that supports ActiveX controls).
The URL is:
<http://groups.yahoo.com/group/LX200/files/>
You can also get it from my webpage at:
<http://www.geocities.com/scottpinkham/astro/astro_main.htm>
I'm in the process of adding a park command -- I will see if it can be made to park at an arbitrary location. I'm looking
for feedback, so if anyone has any request/suggestions, let me know.
-------------------------------------
Subject: LX200 Parking Issues --part 3 of 3
From: John Teel <mapuglist2yahoo.com>
I think I found the solution to parking my LX200. I tried it last night and it seems to work but I really want to write a
small program that does nothing but park the scope and then another that initializes the scope at power up. My procedure is
to park it at the meridian and some arbitrary declination (-40deg in my case). Turn off power...Turn on power. Sync on meridian
and -40deg. This seems to me to me the simplest solution and can be done in TheSky.
Subject: Parked LX200 in Remote Observatory Know Its Position? --part 1 of 3
From: Ralph Pass <rppassrppass.com> Date: Jan 2003
Don Tabbutt wrote:
>There was a short thread on this a while back where the member wanted to park
>the LX200 Classic at something other than zero declination on the meridian.
>
>It's a relatively trivial matter, given the right software, to find out where
>the scope is pointed in the sky at startup if you know where it was pointed at
>shutdown, but I have another question.
>
>One of the reasons the scope is normally started from the zero dec on the
>meridian position is so that it knows where it physically is with regard to its
>own mount, to avoid hitting same. If the scope is started from some non-normal
>position, it will not know its relationship to its mount, and could hit it.
>
>However, once the scope is synchronized to its true RA/Dec, will it now know its
>physical relationship to the mount, or is that a constant that always assumes it
>was started from the normal position?
Yes, it will know where the mount is once you have sync'ed the LX200.
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Subject: Parked LX200 in Remote Observatory Know Its Position? --part 2
From: Glenn Skinner
I have to disagree, the scope has no way of knowing for sure what position, relative to it's cabling, it was in when it is
repowered and synced. I have had two incidents with a LX200 classic that while tracking an object the power was lost momentarily,
when we regained power and control of the scope, the object that we had been tracking was centered and the scope synced. On
both occasions, within a few GoTo commands the cable became wrapped around the scope and damaged. We have since added an internal
camera in the observatory, if the power is lost or a problem with communications to the scope occur, we visually return the
scope as close as possible, to the "home" position, turn off the scope, repower it, and then GoTo an alignment star
and sync. We've never had a cable wrap problem doing it this way.
-------------------------------------------------------------
Subject: Parked LX200 in Remote Observatory Know Its Position? --part 3 of 3
From: Ralph Pass <rppassrppass.com>
Let me clarify, the question was in response to someone who is stowing the scope in a known but not the home (or park) position.
Then powering it up and after moving to a star syncing on it.
Several items here as noted by Glenn:
- Doing a random GoTo at this point can be dangerous (in that you can run in to the scope
- However, slewing manually to a star and then syncing will cause the LX200 to know where it is and the mount is, and will
perform without running into things
- If you know the position at power off (e.g., ALTAZ) and on power-up your computer where you are (or have your computer
compute where you are) you can then send a GoTo command with biased RA and DEC so that the slew is safe. Once there you can
sync on the appropriate object and the system will then function without running into things.
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