Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Phil Crane on 07/07/2011 22:30:02

Title: Do large earthquakes shake telescopes?
Post by: Phil Crane on 07/07/2011 22:30:02

Phil Crane  asked the Naked Scientists:
   
Hi,

I believe that the recent earthquake in Japan shifted the earth's axis by as much as 10 cm. Would this have affected the alignment of earth based telescopes so that they are no longer exactly aligned with the north celestial pole? How are professional telescopes aligned, do they use the same methods as "goto" telescopes or drift alignment?

Love the show (http://www.thenakedscientists.com/HTML/podcasts/),

thanks,
Phil from Sacramento, CA

What do you think?

Title: Do large earthquakes shake telescopes?
Post by: Phractality on 08/07/2011 05:02:00

Modern telescopes, even many backyard models, calculate their longitude and latitude by homing in on guide stars. You simply set the time accurately, set up the tripod so the mount is roughly horizontal, give it approximate coordinates for your location, and push the start button. It will automatically find several bright stars and calculate its exact longitude and latitude.

During an earthquake, a modern telescope may have difficulty getting a stable image, but professional software can discard time intervals that don't look right and shift all the good images so that their brightest stars match perfectly; the dimmer stars will then match up, as well.

Title: Do large earthquakes shake telescopes?
Post by: CliffordK on 08/07/2011 05:22:45

I believe that many of the large telescopes have some kind of intrinsic image stabilizer.  For example, the Hooker telescope has a mercury float system for smooth operation and image stabilization.  This would help with small earthquakes, and distant earthquakes.

Obviously large earthquakes would exceed the capacity of the system though.

However, apparently the Hooker and Hale telescopes are designed with earthquake protection for their very expensive mirrors.

Even with the cheap manual telescopes, the first thing to do as part of the setup is to find known stars.

Title: Do large earthquakes shake telescopes?
Post by: Phil Crane on 09/07/2011 17:15:18

I understand it's easy enough to realign a "home" telescope but anything on a permanent pier (say, the Keck) is, presumably, aligned once and will not need realigning. With a shift of the earth's axis though will it still be aligned?