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Hi Nightsky
I’m not sure of what you understand about polar alignment and astrophotography, so excuse me if the following is kid’s stuff for you.
One of the main reasons for having a wedge (on either a pier or a tripod) is to allow for accurate polar alignment. Polar alignment is very important in long exposure astrophotography, to prevent the stars from trailing and the field rotating. If you never plan to take long exposure astrophoto’s, then the need for a wedge lessens.
If your mount tracks the stars (i.e. it is motor driven at the sidereal rate) but the mount is an alt-azimuth mount, then you will experience what is called field rotation. If you place a star in the centre of the field of view (FOV) on an alt-az mounted scope, then whilst the mount may accurately track that star, keeping it centred in the FOV for 30, 60, 90 minutes etc., you will notice that the stars surrounding this central star will actually rotate around it, as the evening progresses, due to the rotation of the Earth. This is okay for visual observing, but no good for long exposure astrophotography.
However, for purely visual observing, a modern GoTo scope fitted on an Alt-Az mount, once aligned will be able to accurately locate (GoTo) 1000’s of celestial objects and track them for hours at a time without the need for an (expensive) wedge.
Cheers
Dennis
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