Roll-off roof - automation question

[daz]

Hi guys and gals

I am now thinking about automating the ROR closing if rain is detected. I have the AAG Cloudwatcher - and although I haven't got round to playing with the relay as yet, I assume it will do what I need.

So, what have others done to:

a ) Motorise the roof

b ) Ensure the scope is out of way and parked before allowing the roof to close

c ) Interrupt the image sequence to park the mount

 

Thanks for your thoughts!

 

[Barry-Wilson]

Daz

I asked Dave Jackson of Hitec Astro to fit their ascom roof controller (he installed my ROR observatory) in place of the straightforward motor controller.  This links to my usb hub and so to my pc.

The roof ascom driver is commanded by SGP and you can set various slaving options, eg roof slaved to park/unpark, unpark/park before roof opening or after roof opening, park scope at sequence end which then closes roof.  The AAG Cloudwatcher ascom driver and safety switch also links to SGP: once an Unsafe condition is met the 'End of Sequence' options are triggerd and you can opt to have the scope park which in turn triggers the roof to close.  In SGP (or your scope's ascom driver if available) you can configure the park position to avoid contact with the roof and then choose to close the roof either before or after park depending on the dimensions/proximity of your OTA in its park position and roof structure.  For my WO 132FLT on mym new mount this means parking with the OTA horizontal and unparking after roof opens and parking before the the roof closes.

HTH

Barry

[daz]

Thanks Barry! 

I might have to investigate this further - provided I can retro-fit this to my roof!

One more if I may - does SGP only check the Safe Condition at the start of the exposure? If it does, it could be some time before SGP realises it's raining...

[ncjunk]

It's always good to add limit switches to the mount to confirm park position. On mine I will only enable power to the roof if the scope is in the park position. It's a hardwired safety to avoid the possibility of closing the roof on the scope.

[Barry-Wilson]

2 hours ago, daz said:

Thanks Barry! 

I might have to investigate this further - provided I can retro-fit this to my roof!

One more if I may - does SGP only check the Safe Condition at the start of the exposure? If it does, it could be some time before SGP realises it's raining...

It checks and monitors the switch as soon as you connect to the Cloudwatcher.  So you're protected straight away.  Not sure whether it will close the roof if you aren't imaging though.  You can also use the Boltwood Safe to Image driver.

[daz]

Thanks again Barry

Neil - would you have more details, please? I can't re-engineer the roof so I need to be sure the scope is out of the way!

[ncjunk]

Hi Daz,

 I have the same problem, Ideally the roof should always clear the scope no matter what position the scope is in.

Unfortunately my ROR design doesn´t allow for that so I´ve got to provide a safety mechanism and something to cope with a power outage.

The power outage is straight forward as I´ve got a ups to the PC and the powersupply to the observatory which  provides enough power for a shutdown. So if there´s a power failure I can command it all to park and close up.

To stop the roof hitting the scope you can put switches in the RA and dec which are active, closed = 1, only when in the park position. How these are wired up to the roof motor depends on how the roof is being controlled. I´m using an avidsen automatic gate controller and motor that is used on a driveway sliding gate of up to 350kg, basically one you fit to your gate and use a remote control in your car to open and close.

This has a controller board that has an E-stop connection on it that has a wire shorting it out to ground. I can replace this wire with the RA limit switch and the DEC limit switch in series to ground. If either one is not in position then the controller doesn´t have the E-stop ok signal (the E-stop input isn´t pulled low to GND and the controller knows theres a problem) and cuts power to the motor.

The other alternative is to use the RA and DEC switches in series to apply power to a relay and connect the motor controller power through the relay. You then only provide power to the motor controller when the two switches are closed.

I´ve attached a PDF, sorry it´s in Spanish, with some pictures so you can see what I have. On page 2 the second picture shows the E-stop circuit with 1 estop switch, 1 proximity switch and a second proximity switch in series. Instead of those proximity switches I have the limit switches for the RA and DEC.

Obviously the risk here is that the scope isn´t parked properly and it´s raining. The other risk is a failure in the limit switches whilst raining. The switches are unlikely to very often if installed correctly and all signals are normally low power DC to the switches.

You have two options really 1. add in safety circuit and accept the small possibility it could fail when it needs to close due to weather. 2. Forget about the safety circuit and accept that there is a chance that the park command hasn´t worked and the scope may be in the way.

I don´t really like either to be honest but I prefer 1. to number 2 as I´ve come accross a few software problems over the years.

Hope that helps give you an idea of what I have. Really I need to put a roof that clears the scope but don´t have the money!

 

Neil C

 

IMG_20160504_0001.pdf

[Barry-Wilson]

The Hitec roof controller has DC gates for mount RA and DEC limit switches too (little magnets in a plastic tab attached to the wires, fixed in place on tyhe mount with some silicon glue).  I had these fitted at firtst to give the secure knowledge of a parked scope as Neil has described above.  I did remove these wanting the certainty of a roof closure in the case of rain, I just had to ensure my OTA cleared the roof in a parked position.  The roof mechanism has a resistance routine so it will stop if it collides with an OTA.  No (or little) damage to the OTA if a park fails during roof closure but ingress of rain!  It's all a blanace of what yoou want for yout specific observatory.

[Gina]

I shall have this problem with my MN190 Mak-Newt but no problem with refractors as the roof clears these in any position.  The range of position where there's a problem with the MN190 is quite small so it isn't necessary to park the scope in all circumstances.  I think that even when I have my roof automated, I'll stick to manual control with the MN190 and only image with that when the probability of rain is very low - as I do now.  Automation will really come into its own with the medium FOV 500mm FL triple imaging rig with Esprit 80 ED and 2 x ST80 and the widefield triple rig (when that's built).

I may get back to my roof automation once the weather warms up a bit more.  Same applies to observing or imaging - I feel the cold more these days

[daz]

Thank you all for your input!

I shall go and research