Re: CP4 is definitely NOT water tight - VERY suseptible to DEW flooding

Christopher Erickson

If you have a condensation problem with your CP4, simply put a plastic, paper or cloth bag over it. Or put a dew heater patch on the back of the CP4.
More importantly, if you are getting this kind of profound volumes of dew inside of your observatory or around and on the rest of your observing site and equipment while observing, you have other problems that urgently need to be dealt with. Serious problems. All of the rest of your electronics will be much-more vulnerable to corrosion than the CP4 electronics. Not to mention OTA parts and delicate optical surfaces.
The circuit board in the CP4 is dip-sealed and dew is, by definition, non-corrosive, distilled-water. However if your observing location atmosphere has potentially-corrosive gasses or particulates in it, like car/truck/furnace/propane/butane exhaust, that could be, when mixed with water, the source of your corrosion issues.
My suggestion is to stop fixating on the CP4 and start evaluating your entire setup location and see what-all is vulnerable and what can be done about the condensation and corrosive gasses and particulates. Your cameras, optics, computers and everything else are at serious risk, not just the CP4.
I have seen people use a big binder clip to wrap a beach towel around the lower half of their mounts and all of the electronics. Not high-tech and it doesn't involve new holes and machine tools, but is very effective.
I hope this helps. 
-Christopher Erickson
Observatory engineer
Summit Kinetics
Waikoloa, HI 96738

From: ap-gto@... [mailto:ap-gto@...]
Sent: Sunday, October 7, 2018 4:50 PM
To: ap-gto@...
Subject: Re: [ap-gto] CP4 is definitely NOT water tight - VERY suseptible to DEW flooding

    One further note of observation, on my original post on CP4 dew water entry.
    I should emphasize that the CP4’s  “Achilles Heel” – the CP4 Ethernet RJ-45 connector – is most prevalent for those who “Upgrade their CP3 on one of their OLD  AP mounts” and choose to continue using the new CP4 still attached,  angled upward on top of their RA axle. This leaves the gaps in the panel around the RJ-45 fully exposed to its own  dew condensation  as well as the excess dripping down off the OTA surface. There would still remain a slight risk of water going straight down the center plug’s hole, to the circuits inside.
    The best avoidance is to attach it vertically to the AP-900 or AP-1200 pier or tripod, rather than on the RA axle. This will make the CP4 as well protected as on the current model mounts – (AP-MACH-1, AP-1100 and AP-1600, etc.) ... in their vertically oriented position.
    You should still “RTV or Silicone rubber seal” around the Ethernet (and possibly a bit around the Guider) panel connector gaps, and either unplug the corner rubber stoppers from the new CP4 (black) models, or drill the two missing corner DRAIN holes in the first few years released CP4 (white) model versions,  case bottom edge,  backsides.
    Upon closer examination, I notice that WHEN the CP4 is mounted “vertically”, there is an...  additional BONUS in dew protection.
The “upper front cover” (the one with the antenna stick), sticks out in front of the connector panel by 3/4 inch, compared to the old CP3 which stuck out slightly less,  (1/2 inch).
    Although not likely intended, this acts as an “OVERHANGING ROOF”, protecting the panel of connectors below it, from being hit directly by dripping dew from above, such as dew streaming off the far greater OTA surface. Thus, the Ethernet connector’s oversized hole’s gaps (approx.  0.030 inch), would not endure a direct splash, in this configuration.
    Furthermore, if you still wanted a bit more protection, you could even glue a square dowel or piece of wood/plastic,  6-1/4 inches long by whatever extra thickness you like, along the upper cover’s bottom edge, to provide an even further outward diversion of the dew, away from the connector panel. Ideally, you could even locate a triangular prism cross section dowel, or just use a small piece of plastic or metal strip, to angle outward from just slightly above the CP4 top cover’s lower edge, which would divert the water drips even further away,  with a smoother run-off – while presumably still not interfering with the mount’s cabling.
    All of the remaining panel connectors, (except for the Ethernet and the Guider), are seen to be bolted VERY securely from beneath their panel surface,  making those connectors very  likely “water tight”,  to begin with.
     Along with the YOUR now properly sealing the Ethernet connector, and  “opened” DRAIN holes (for insurance), the CP4 should then be truly “water resistant” ... if not finally ....   “WATER PROOFED” -  ready in its vertical attachment position, to challenge dew,  unexpected rain showers,  and errant sprinkler blasts.
Joe Z.


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