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In my mind, how many columns are used or the lifting capacity of individual columns isn't as important as the overall rigidity of the assembly. As long as the combined lifting capacity of the columns is at least, say, 4 times the expected maximum load on the columns. That is not a scientific conclusion. It is just a subjective one based on experience.
Linak makes columns with different thrust capacities – 1000, 1500 and 2500 Newtons. For my system with AP1600 mount, 16” RC and Lunt 152, I fabricated a lifting column using two of the 2500 Newton Linak units. The total lift capacity is 1124# and I have about 550# of mount, counterweights and scopes riding on them.
When you mentioned using 3 or 4 columns, were you considering using the 1000 Newton units instead of the 2500 Newton Linak columns?
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Piet Tech/Linak columns are great devices when implemented properly.
A simple limit switch interconnected directly with the roof motor can make sure the roof can't close if the pier isn't fully lowered.
However the increased robotic Observatory complexity does come with some risks. Switches can fail, mount power supplies can fail. Robotic columns can fail. Etc.
Personally I would suggest NEVER have a robotic or remote Observatory design that requires a mount and/or robotic column to be in a specific position before a roof/shutter can be safely closed. Inevitably there WILL be an eventual malfunction someplace. And either your roof can't close and everything gets wet, or a scope gets seriously damaged by the roof.
For a Mach1/2, one Linak column is probably good enough. For a 900/1100 I would probably use two columns. For a 1200/1600 I would probably use 3 or 4 columns.
On Mon, Jan 10, 2022, 7:09 AM Dale Ghent <daleg@...> wrote:
I think Bob's point is more along the lines of don't trust *only* software to keep the unwanted from happening. If you're going to automate roof closures, make sure that your roof control system has the appropriate *hardware* safety interlocks installed to prevent the unintentional guillotining of your telescope. This would mean things like making it physically impossible for the roof motor to run if the mount isn't in the correct orientation.
> On Jan 10, 2022, at 12:03, Brian Valente <bvalente@...> wrote:
> >>> Bob Denny put the fear of God in me to not use ACP automation to park and then close the roof.
> I'm not sure what to make of advice not to fully use automation software from an automation software supplier 🤔
> On Mon, Jan 10, 2022 at 8:43 AM Jerome A Yesavage <yesavage@...> wrote:
> Yes, I have the Pier and I get fine images in all positions.
> I park at P5, but Bob Denny put the fear of God in me to not use ACP automation to park and then close the roof. If I use automation, I have to have the pier lower so the roof always clears the scope no matter what the mount position. Now Vito, says you can put a park position sensor on the controller, but I have never gotten this to work. I have the proximity sensor and an extra toggle for showing the pier down, but I cannot get the roof controller to take these inputs reliably. It will open and then raise the pier, but it closes before the pier is down (notta so good).
> This is the proximity sensor:
> The toggle sensor is the same Honeywell that is used on my roof. Rock solid.
> If any of you have this working reliably, please show me your wiring and settings on the roof controller. I fear I am doing something dumb (again).
> Brian Valente
> portfolio brianvalentephotography.com