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Roll off roof and mount power cutoff

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#1 dariv

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Posted 18 September 2020 - 11:32 AM

I have a roll off roof controlled by a skyroof controller with mount parked sensor. This sensor also cuts power to the roof motor if the scope isn't parked, so the roof can't close on the scope.

I also want to do something similar with the mount. ( an Atlas / EQ6 ) the mount is controlled via EQMOD and SGP.  It is possible to slew the mount with the roof closed, I've done it trying to run a flats sequence. I would very much like this never to happen again. My initial thought was to use the roof opened switch to active a relay that in turn would enable 12VDC to the mount. But I don't think SGP would like that since it would not have communication with the mount unless the roof was open. When I run flats SGP parks the scope first. This will close the roof since it is slaved to the mount. Once the roof moves off the closed switch I'll loss comms with the mount and I suspect SGP wont like that and throw some kind of error. 

How do you ensure that the mount can only slew when the roof is open?

Thanks,

-DaRiv 



#2 rgsalinger

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Posted 18 September 2020 - 12:08 PM

I'll be interested in hearing the answer to this as I have the same Skyroof. What I did was make absolutely certain (short piers) that the roof can never come in contact with my imaging systems when opening or closing. It just seemed way too hard to have a 100 percent failsafe solution. Further, I want the roof to close if the weather gets bad, even if the scope cannot be parked for some reason. I have a separate backup power supply that will do this if I lose power or internet access, etc. 

 

Since I don't image below 30 degrees of altitude I don't really care if my scope is not above the roofline. The observatory walls also help the system on windy nights. Of course this may not work for you if you already have a tall pier and can't swap it out. 

 

Rgrds-Ross



#3 Phil Sherman

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Posted 18 September 2020 - 10:38 PM

There's no way to "lock" the mount with EQMOD when the roof is closed. This doesn't mean, however, that you couldn't effectively lock it. I can think of three possibilities:

 

1. Set up routines that run when the roof is closed and not closed.  These routines would change the mount limits in EQMOD's ini file to prevent the mount from moving. The ini file is a text file which should be relatively easy to edit.

 

2. Write an ASCOM mount control module that monitors the mount's position. This module would issue a park command if it detects the mount has moved from the park position. This module would need to run only when the roof is closed and power is applied to the mount.

 

3. Write an ASCOM mount control module that issues a "park" command to the mount. Trigger this module to run when the roof is closed and the parked indicator changes state to "not parked". The state change is an indication that power is applied to the mount so the program should have no issues connecting to it. When writing this module, include code to fail gracefully if it can't connect to the mount. This module could also be triggered by a weather event that forces closing the roof.


Edited by Phil Sherman, 18 September 2020 - 10:40 PM.


#4 dariv

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Posted 19 September 2020 - 01:50 PM

My scope is an 8" Newt. astrograph, so having it always below the roof line would not work out, plus the fact that my obsy. is only 6'x8' .

I'm not sure how a software routine would know the roof was open or closed, unless it had access to the SkyRoof roof controller. I want to prevent a slew even if I go into EQMOD and tell it to move. I'm biased towards a hardware solution. Something like a switch that activates a relay that allows power to flow to the mount. Simple for me to wrap my head around and debug if necessary. I think I'd have to change the way I capture flats in SGP though. At the moment flats are an event of each target. I suppose I could make a "flats sequence" that only connected to the flat panel and camera?   



#5 rgsalinger

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Posted 19 September 2020 - 02:53 PM

If you are permanently mounted it's really unnecessary to capture flats every night. I do them about once a month and see to get very nice results. I do keep my scope parked below the horizon, though to minimize the amount of dust that gets in. 

Rgrds-Ross



#6 Calypte

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Posted 19 September 2020 - 05:02 PM

If you are permanently mounted it's really unnecessary to capture flats every night. I do them about once a month and see to get very nice results. I do keep my scope parked below the horizon, though to minimize the amount of dust that gets in. 

Rgrds-Ross

Might this not depend upon the type of scope?  Seems to me that an RC with the optics open to the elements might need nightly flats.  I use a refractor, and there's no way for new dust to land on the camera filters or CCD cover glass, provided I keep them attached to the scope.  Dust on the objective is out-of-focus and should manifest only as fractionally reduced throughput..



#7 kathyastro

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Posted 19 September 2020 - 05:24 PM

If you are permanently mounted it's really unnecessary to capture flats every night. I do them about once a month and see to get very nice results. I do keep my scope parked below the horizon, though to minimize the amount of dust that gets in. 

Rgrds-Ross

I am not sure the OP's issue has to do with "every night".  But flats have to be captured some time.  I think the issue is that, when flats are captured, even if it is only once every six months, the scope might have to move (for example to aim at a flat panel), and moving is dangerous with the roof closed.

 

The only way to ensure that the scope doesn't move when the roof is closed is to make it impossible for it to move when the roof is closed.



#8 iwannabswiss

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Posted 19 September 2020 - 08:08 PM

Does the mount have to be on to do a Flats routine? I don't know anything about EQMOD or SGP, but I think something like what @Phil Sherman recommended may work. Is it possible to get SGP to disconnect from the equipment automatically?

I know at least with Voyager, we can run specifics scripts. So, in theory, attaching the mount to an ASCOM switch to either turn on / off the mount, I could park the scope, disconnect the mount, turn on the Flat panel, then run a Flat sequence.


Edited by iwannabswiss, 19 September 2020 - 08:09 PM.


#9 dariv

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Posted 20 September 2020 - 04:46 PM

The issue isn't really about flats, it's about the possibility of the mount moving with the roof closed. My roof controller (SkyRoof) checks an external laser sensor that indicates that the scope is in the parked position. It will not open or close unless the scope is in the parked position. I have also added a relay that works off the same park sensor that enables AC power to the roof motor itself. So unless the sensor is blocked (actually, it's a laser distance sensor, so it has to be blocked between 1" and 1.5" from the sensor) there is no power to the roof motor and no possibility of the roof moving. So even if the roof controller sends a command to open/close, the roof will not move because there is no power to the motor.

What I want to do now is apply the same sort of absolute control over the mount. I want there to be no possibility of the mount moving unless the roof is fully open. But if I simply cut power to the mount, anything communicating with it will loose that communication. The issue with flats is that they are (at least the way they are programmed now) an "event" in SGP. They are part of a programmed sequence that runs at the end of the sequence. The scope parks and the roof closes before the flats are taken. I do not believe SGP will be able to continue once it looses communication with the mount when the roof closes. Come to think of it, the roof controller will not be happy either. It connects to both the roof and the mount. There is a rain sensor connected to the roof controller and it sends a park command to the mount if rain is detected. Once the mount is parked, then the roof closes.



#10 Phil Sherman

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Posted 23 September 2020 - 09:37 AM

....

I want there to be no possibility of the mount moving unless the roof is fully open. But if I simply cut power to the mount, anything communicating with it will loose that communication.

.........

The first thing you'll need to add to your control system is a switch that closes when the roof is fully open. Without this, there's no way to detect that the roof has fully opened. As you suspect, you can't drop power to the mount without all of the software connected to it being very upset when communication with it fails.

 

My remote observatory has the observatory control functions run by a Raspberry Pi computer. It handles power to all devices including mounts, lights, opening and closing the roof, and powering up computers using wake-on-lan. Switches tell the Pi that the roof is fully open or closed and are used by the Pi to shut off the roof motor. A second set of switches are activated if the roof moves 1/4" beyond the shutoff switches. This second set drops power to the roof motor, forcing it to stop. My observatory partner and I each have a scope in the building. both scopes have external parked sensors and normal roof operation requires both scopes to be parked. In addition to the parked sensors, we have a webcam that can be used to determine that the scopes are parked. The control system also has an override that allows the roof to be moved without the scopes parked. This is used if one or both of the parked sensors fails. Fortunately, the roof design allows both scopes full movement with the roof closed. My scope has less than 3" clearance with the roof when parked in a horizontal position.
 


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#11 dariv

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Posted 23 September 2020 - 10:47 AM

I have a SkyRoof controller for the roof motor that has both open and closed roof position switches. I also have a laser position sensor that indicates if the scope is in the custom parked position. When the roof is open, and you issue a "close the roof" command, the controller first issues a park command and then waits for the parked switch to active (and I believe also for the mount to report "parked") before closing the roof. As a backup, the parked switch also controls a relay the enables power to the roof motor. The roof motor only has power if the scope is in the parked position. Closing the roof is not an issue or concern. What I'd like to do is somehow tie the mount to the roof position, so that a slew can only happen when the roof is open. There is nothing to prevent the mount from slewing into a closed roof. 




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