Problem with Alpha 900 (and 700) with MacBook Pro

I guess I should have made this more clear...and it's only been recently that I've come across the tethering term so it's not a word I think of for what I'm doing. Back when I first tried to do this a few years ago I just knew it as remote camera control and it worked great on my Windows PC (the only thing I've found that works better in Windows since I got my MacBook a few months ago).

I want to be able to connect the Alpha 900 to my MacBook for astrophotography, which usually requires taking a number of photos and inspecting them on the PC screen to ascertain focus, tweaking the focus after each exposure. Once focus is satisfactory, the procedure involves taking a number of exposures of up to 5 minutes each, downloading each to the computer as it's taken so that it can be examined while the next exposure starts. Not only is it a pain to have to remove the USB cable after each exposure and turn the camera off and on, it also introduces the possibility of moving the scope just enough so that the following photo won't align properly for stacking with succeeding photos.

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Mike
http://www.conductorband.com