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  1. #1
    Join Date
    Nov 2005
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    Virgil, NY
    Posts
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    Default Intermittent "connect" problem

    Hi all,

    I've had a very interesting, or should I say embarassing, experience in posing an ill-formed problem question to the wrong group - the LX200 Yahoo Group. The question was this:
    Every night when I return to the telescope for the evening and turn it on, the settings from the previous "parked" position are lost. Upon starting up, the telescope readouts say RA=0, Dec=0 even though the telescope is aiming low to the southwest (and nowhere near RA=0; Dec=0). The clock is correct, and the sidereal time is correct, but the telescope will not retain the position/pointing information after turning the telescope off. I don't know whether the PEC data is lost. This sounds like it should be a CMOS battery problem. Is it? Is there a second replaceable battery somewhere else in the innards of the telescope base?
    If you're subscribed to that group, you can read the meandering responses and new topics that various writers introduced into the thread. I realize (now) this was a rather stupid question to have posed on that forum, especially because I really already knew the answer and shouldn't have asked about it the way I did. The answer is that the LX200 Classic does not "park," as many were quick to point out. In this forum we know better, of course, that ACP can drive the telescope to a certain alt/az and park it there.

    There indeed is an EPROM device on the LX200 Classic that keeps some information, such as observer latitude, between power on/off cycles, but the "park" position is not part of that. And the only non-storage-based persistent feature is that the diurnal and sidereal clocks are kept running by a CMOS battery.

    I still have the same question, however. Sometimes, not always but often enough to be bothersome, when I power on the telescope, power on ACP and then "connect the telescope," ACP's readout will have the wrong values for the RA and Dec, that is, RA=0 & Dec=0, and thus crazy wrong Alt/Az values, and I don't understand why this is so. The result is that I have to be at the telescope to manually slew it to a bright star, center it and resync the telescope manually. Once it's close, I can use the SyncScope script to get it right on. But this is bad news for remote observing!

    My question is really, what communication goes on and in what order between ACP and the telescope (in my case the Meade) at connect time that captures, or computes, the parked position of the telescope and presents that information in the console readouts? Somewhere this sequence is failing for me. The correct values of the "park" alt/az are in the ASCOM/Telescope/MeadeEx.Telescope registry. Somehow, in my case, the communication is getting messed up.

    Thanks in advance for any enlightenment.
    Dick
    www.VirgilObservatory.us
    Pier-mounted Meade 12-inch SCT "classic"
    w. focal reducer to f/5.3 ~ FL 1630mm
    Optec TCF-S focuser
    SBIG CFW-8A and ST7-XME
    FOV ~ 15' x 10'
    H-alpha, BVRI, RGB & Clear filters
    MaxIm and, of course, ACP!
    AAVSO Code: BRIC

  2. #2
    Join Date
    Dec 2006
    Location
    San Jose, CA, USA
    Posts
    898

    Default

    Quote Originally Posted by Dick Berg View Post
    My question is really, what communication goes on and in what order between ACP and the telescope (in my case the Meade) at connect time that captures, or computes, the parked position of the telescope and presents that information in the console readouts?

    Hi Dick,

    My guess would be : none.

    ACP just sends a park/unpark ASCOM command to the Meade ASCOM driver, so any mount specific magic for storing a park position will be done by that driver, not ACP.
    After the mount is unparked, ACP just requests the current RA/Dec position as normal.

    It may be worth asking on the ASCOM group, or possibly looking in the Meade ASCOM driver source code if you're feeling so inclined.

    John

  3. #3
    Join Date
    Nov 2005
    Location
    Virgil, NY
    Posts
    5,037

    Default

    Thanks, John... Hmmmmm.... This has never before been a problem until a few weeks ago. Your right about ACP requesting the RA/Dec. I'm just trying to figure out whether it's the request from ACP that not being received, or whether it's the push to the telescope during initialization that not getting there. Could be a loose cable, although that's the first thing I checked.

    The RA and Dec has to be computed somewhere in ACP (or the driver). I've got the telescope pointed at az=190, alt=25 (low in the SSW) - and that's about HA=40m, Dec=-25 degrees. The values 190/25 are stored in the registry in the ASCOM telescope hive. So at startup, some code somewhere picks up those values from the registry, determines the sidereal time, and does the transformation from alt-az to RA-Dec. Those RA-Dec values are then pushed to the ACP control panel display and the telescope (just like a "sync scope" function), or maybe they're pushed to the telescope by the driver and then read back by ACP. But often they're displayed as 0/0 in ACP and in the Meade telescope paddle display as well. It's at those times I have to realign the telescope.

    I've also noticed that there's some relationship of the problem to whether the drive is tracking or not, but I haven't been consistent about finding that relationship yet.
    Dick
    www.VirgilObservatory.us
    Pier-mounted Meade 12-inch SCT "classic"
    w. focal reducer to f/5.3 ~ FL 1630mm
    Optec TCF-S focuser
    SBIG CFW-8A and ST7-XME
    FOV ~ 15' x 10'
    H-alpha, BVRI, RGB & Clear filters
    MaxIm and, of course, ACP!
    AAVSO Code: BRIC

  4. #4
    Join Date
    Oct 2005
    Location
    Mesa, AZ
    Posts
    28,267

    Default

    Well, though I am not the current LX200 drive author, I did write the original. Jon Brewster introduced some fancy stuff to allow arbitrary parking positions. This will have to be a phone call with the sources at hand, and my attempt to understand Jon's code (whick is "tricky").

    Before all that, isn't there a "reset park position" button on the driver's setup window? What happens if you click that? WIll it unpark thereafter. That's a stab in the dark.
    -- Bob

  5. #5
    Join Date
    Nov 2005
    Location
    Virgil, NY
    Posts
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    Default

    Bob, I'll check it out. I haven't seen the driver setup window for years! it's been working so well. The thing is, it's intermittent, which is always bad news for debugging. Don't do anything with this yet, until I check out your suggestion, look at the code in the driver, and then scream back here. Thanks.
    Dick
    www.VirgilObservatory.us
    Pier-mounted Meade 12-inch SCT "classic"
    w. focal reducer to f/5.3 ~ FL 1630mm
    Optec TCF-S focuser
    SBIG CFW-8A and ST7-XME
    FOV ~ 15' x 10'
    H-alpha, BVRI, RGB & Clear filters
    MaxIm and, of course, ACP!
    AAVSO Code: BRIC

 

 

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