PAN006: Activity Log

I finished building PAN006 in September of 2017, with the exception of weatherproofing the mount. I was offered a home in a dome at Wheaton College (Norton, MA) which I gratefully accepted. This required me to add software to POCS for controlling the Astrohaven 7 foot dome (i.e. opening at the start of observing and closing when done), which I did; this was my second major contribution, after an earlier re-working of the Arduino code.

Unfortunately, the automation of the dome hasn’t worked as well any of us would like: the Astrohaven system has a very simple control interface, but it is really too simple; it isn’t sufficient to prevent tangling the straps that move the shutters of the dome, which can then result in the dome being stuck open or closed. If it is stuck closed, then you have a very tricky job to open the dome. And if it is stuck open, then you have to rush to repair it before rain next arrives, and in Massachusetts that is a matter of hours or days most of the time.

This problem of tangled straps occurred at least 5 times over 11 months of automated operation, most recently happening just 6 hours after I re-enabled the automated operation. Sigh. Today I pulled the scope out of the dome and brought it home, where I plan to weatherproof the mount, along with replacing the SSD (storage) on the NUC and upgrading Linux to Ubuntu 18.04 (the version we now recommend, which wasn’t the case when I built the scope).

I also need to find a new site for PAN006. I’ve had a couple of offers from folks in the past, but will need to see if they are still willing to host the scope. I’d like to find a nearby location first, as that makes it easier to work out any problems before installing it at a remote site.

I’ve been designing a 3D printable weatherproofing for protecting the RA bearing. To help I also created a 3D model of the iOptron iEQ30 Pro mount so that I could see how the weatherproofing (blue) would be positioned as the mount rotated. See https://github.com/jamessynge/openscad-models for the gory details.

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I printed the part today:

Once I get home I’ll find out if it actually fits. I’m worried that it is too big, either due to miscalculation or due to a lack of ability to accurately measure the diameter of the RA bearing covers.

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Looks good. Do you know about the UV rating of the filament used? Or would you just plan on replacing it every year or so? That said, curious to see how you plan to attach it.

I used PLA, which was available in the makerspace at my office. PLA is made from plant matter, and is advertised as biodegradable, though there are disputes about exactly what that means. I think the answer to that is to paint the exposed surfaces, e.g. with acrylic spray paint, which will also help avoid penetration by water, which could then freeze and crack it.

As I feared, the piece is a tad too big (i.e. I measured the radius as 62mm, but it is probably somewhere nearer to 59 or 60mm). I printed a very small rotary extrusion today based on a 60mm radius, and will check to see if that is a match before printing a larger piece… something I wish I’d thought to do earlier.

Regarding attaching, I don’t have a design yet for a full “collar” for the RA axis, but my thought is to produce segments around the RA axis, the big one that is on top when parked, and two much lower profile parts that clip into it and almost complete the circle, leaving a gap for the RA axis clutch. Adhering it will probably be done with a thin layer of either silicone or a moldable plastic like Sugru (i.e. not with superglue).

And I may try to design the big part as two separately printable pieces, one that attaches to the axis, the other with the overhang. It could help reduce the required build volume, making it possible to produce on smaller 3D printers. Not sure yet about that.

In order to model the DEC axis weatherproofing too, I’ve created a more complete model of the mount, though still omitting most details about the base of the mount. In addition the mount, the animation below includes some “decoration” that shows the axes of the coordinate systems at which the model supports easy addition of additional objects. I should probably add a fifth for the plane of the DEC bearing on the motor side.

animated-axes

The updated model files are on github.

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I’ve continued the design work on this, going through several alternatives, currently settling on a design whose outer shell is printed as the following 5 parts:

I’m now working on designing the supports that actually attach to the moving part of the mount (i.e. the part of the mount shown in the animation). This is fairly challenging because a 3D printer doesn’t perfectly reproduce a model it is given to print; sometimes a hole will be a little smaller or larger than specified.

Another consideration is allowing room for the DEC axis power and control cable. Just yesterday I realized that it would be easier to provide that room if the mount were to park such that the RA clutch ends up on top, with the uncluttered side of the RA axis “facing” down. The cable could then just hang down on that side, with no chance of getting snagged on the clutch, and little chance of getting crushed between the supports and the RA motor; of course, I need to have the chances be zero, but this is still a work in progress!

Hey @james.synge, any update on this project? I’m trying to get PAN008 back on sky pretty soon and the only thing I haven’t done is the weather-proofing. If this is at a point where I can give it a try that’d be great (assuming I can find a big enough printer).

Sorry @wtgee, I became overwhelmingly busy at work, leaving no time for the weatherproofing effort. I’m hoping that I’ll be able to return to it in June after I return from the Society for Astronomical Sciences Symposium, where I’ll deliver a talk about PANOPTES.