Hat Trick?

On my previous post/thread Jim Taylor talked about a "Hat Trick" when doing long exposure astrophotography...

Jim, or anybody that might know, what exactly is this all about? I'm not sure how soon I'll jump into long exposure but I would like to know these things before I do...

Thanks to all for your attention...



Clear dark skies!

Ivan

When you open your shutter on an SLR, the mirror pops up out of the way. This is a mechanical function. The result is some vibration within the camera. If the vibration does not dampen out before the shutter opens, it can result in a disruption to your focus for that portion of your exposure.

The "hat trick" involves covering the lens of the camera (or the objective of the telescope) by holding an object (like a hat) in front of the lens when you depress the shutter, and after waiting several seconds for the vibration to cease, pulling the hat out of the way.

Some SLRs have a mirror lockup function which you can use to move the mirror before depressing the shutter release. Of course, you must focus and compose before moving the mirror as once it is moved you cannot see through the viewfinder.

Hope this helps (and hope it's close to being right).

macnmotion