Chris,

 

    I don’t know who at AP has been  “talking you up” on this “CP4 corrosion myth”, since I only had Marj posit that theory to me, and she not being technical, probably heard it from someone else on staff, tossing it around the table – likely, the so-called “servo engineer” who declared the first drowned CP4 was definitely not “caused by water corrosion”. Marj then countermanded his errant opinion – actually, she is way smarter than most. So, it was definitely just “plain drowning”. The high water mark, an  inch-wide white scum mark, rubs off easily, like chalk, the copper traces were unaffected, thus the PCB surface was NOT corroded. I just took it for granted that Marj uses the term “corrosion”  someone loosely, as offhand  non-technical parlance, signifying nothing other than  there was a swath,  demarcating the depth of dew built up inside the CP4 case, over a few nights of viewing time – but neither of which had bottom corner DRAIN holes, for the CP4 .... to “relieve itself”.

 

    Now, as you reported in another post’s reply below, as a professional engineer you are quite familiar with and have regularly experienced “acid rain corrosion”, such as at your observatory near the Hawaiian volcanoes. Although you attempted to apply your own circumstance to my pristine site here in Canada, you should realize that if there had actually been ANY outward sign of  “acid rain corrosion” causing the CP4’s to burn out, then the same “acidic dew” would have been raining down on my “nylon tarp”,  covering the scope over the past 6 years, (from May 2012). The nylon tarp would be a very delicate “lace cloth” by now.

 

    You remember, Chris  ---  my nylon “HINDENBURG Tarp”, as you recently referred to - covering my AP-1200, with its 900 WATT automatic dew heater underneath the tarp, keeping it at 60% relative humidity, 24/7/365, when it is not open for a few short hours during a session. Yes .... the tarp is still quite intact, didn’t burn up as you expected, doing well, with not even a single pin-prick hole in its large nylon surface – from anything like acid rain. Besides, Chris, if there were a molecule of sulphuric acid in the dew downpour entering my leaky CP4 – actually BOTH of them -  then the AP-1200 paint job would have yellowed or burned off in spots by now, as would the primary mirror coating,  my backyard lawn wouldn’t be the rich green colour it has been all summer as in every year, the beautiful flowers bloomed in my garden a few feet away, fruit trees nearby didn’t prematurely shed their leaves even until now in the fall, and there wasn’t one single dead bird in the yard – i.e. no equivalent sure-tell “Coalmine Canary”, if you please.

 

    Is that enough evidence to contradict AP’s cockamamie assumption your contact is espousing,  about “corrosion from acid rain” causing my CP4’s to fail – BOTH of them – rather than ending up as a one inch deep baptismal font? I can’t see it being your own professional, well-considered, engineering conclusion – without evidence.

 

    I assume your own CP4,  at the occasionally volcano gassed, “Waikoloa Hawaii,  is on a “new AP model” mount, rather than being attached at your site’s local Latitude angle on top of the RA axle. So I find your claim quite interesting  ... that with all the “sulphuric acid rain” occasionally hitting YOUR own  CP4, it still has not corroded (inside or outside), and yet you presume that MY far cleaner Canadian skies  have an even stronger sulphuric acid content than your VOG in Hawaii. This is Canada  ... not VENUS ! 

 

    You really should check out the pretense your friends at AP may been trying to foist on you – if that really was the case. Unlike the “vog” (volcanic fog, as you called it) near your site, the only “smell of sulphur” here on the North American  mainland, might be emanating from someone’s oval-like office, or more recently coming from under ... “a Bench” ;-)

 

Clear non-VOG skies, Chris -

Joe Z.