Obstruction in Light Path

Friday, August 18, 2017 12:47 PM

Problem(s) Encountered:

Mysterious large obscuring structure(s), partially in focus, that appears to

move (at one point covering half the visible sky, this at 1x1 binning with the

Andor), then vanishing. Visible in the science images. Later, an obscuration

was seen again, this time with a more complicated structure. Finally, while

attempting morning twilight flats, an obscuration was seen again, this time moving rapidly (about 1/3 the field of view per 10s exposure).

Observers not sure what these structures are. Visual inspection turned up

nothing obvious on the primary or secondary mirror, and nothing obviously

blocking the light path. Attempted closing and re-opening the MIS hatch cover had no effect on the obscuration.

Our best guess is that this might be wildlife of some sort, possibly crawled

into the baffle in the middle of the primary mirror.


Pulled camera and looked up through optical path.  Found nothing obstructing the light path, although that means little when it comes to transitory visitors (aka moths).  Blew some air around inside and haven’t seen any more issues since.