Mirror Covers

Friday, August 5, 2016 9:00 AM

Problem(s) Encountered:

We encountered this problem when I opened the 2.4m dome around 11PM:

All of the mirror covers failed to open.

I found two possible solutions.


I found this in the 2.4m manual ( http://mdm.kpno.noao.edu/24_manual/hilt09.html ).

But it seems that I was not allowed to do this.

2) Clearing a hung up mirror cover petal

I found this from the trouble reports: 2.4m, Closing Mirror Covers


But I don''t know I can do this or not because

I am afraid to take the risk of injuries (how much dangerous is it?)

as the solution mentioned.

So, we could not solve this problem.

I figure that none of the staffs will go up to the mountain during weekend.

Please let me know what can I do to fix this.


Found the condensate trap immediately downstream from the compressor had, well, blown up.  I am guessing it became internally clogged with debris over years of use and ultimately, the pressure had to go somewhere.  See attached image.  The plastic collar at the top of the trap completely sheared.  I looked for a spare trap but it does not appear we have one on site.  Nevertheless, I was able to find parts from old traps (o-rings, fittings, pass-throughs) here and there and build my own.  It is now installed and appears to be holding pressure.  The only downside to this kludged trap is that there is no obvious user-set pressure regulation or gauge on it, as there were on the old trap.  Still, checking pressure at the gauge farther down-line in the dome, it is only running a few psi higher than nominal:  the old trap regulated at 80psi, the new “system” is running at ~85psi.  This should be tolerable for the time being.  I’ll plan on buying a new trap soon.

While up here, I also tested out the N2-fed backup to the compressor-driven system.  It works as described.  See images below for the valve that needs to be turned to swap between the two feeds.  This valve is found immediately east of the N2 (orange) bottles in the southwest corner of the dome.

Regarding opening stuck mirror covers—obviously this was not the issue.  Still, you did the right thing by not trying to cycle them by hand if you had any concerns at all. Safety first!  It is a somewhat jolting experience when they pop open suddenly.

All systems are now up and running.  Sorry you lost an entire night for this.