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| Meade LX200 8" telescope mounting on a wedge, in polar (equatorial) home position |
(and why it took me a long time to do it tolerably well)
A personal Experience
Why Polar?
There are several reasons why you might want to do an accurate polar alignment of your scope. If you want to take photos of sky objects with exposures longer than around a minute (and less if you are really picky about your results) you'll encounter the problems of bad alignment (in both Alt/Az and Polar (equatorial) mode), tracking problems (backlash and other mechanical errors in your GOTO drive), and if you are trying to take long exposures in Alt/Az mode, rotation.
(In Alt/Az mode, the GOTO scope uses two sets of gears to track an object in the sky by moving the scope in two planes, vertical and horizontal. The cost is that the sky appears to rotate around the object being tracked. With a polar alignment, the scope is oriented along the polar axis of the earth so that one set of gears is no longer needed to track an object, once centred, and rotation is eliminated.)
I have a Meade LX200-ACF 8” (203mm aperture) Schmidt-Cassegrain telescope (SCT). It comes with an Alt/Az fork mount. There are very similar Celestron and other brand GOTO scopes. The default Alt/Az mode for these scopes is fine for viewing but not so good for long exposure astrophotography.
People will tell you that doing a polar alignment is the better way to go for astrophotography, and they're right. There are lots of reasons why, but basically it comes down to 'less moving parts', so less opportunities for error to creep in—but more of that later—and, with an accurate polar alignment, there's no rotation to worry about. Error and rotation equals movement and movement is something you do not want during long exposure photos. Again, more about that later.
To do a polar alignment you either need to have an equatorial mount rather than an Alt/Az fork mount, or if you have an Alt/Az fork mount, you need a thing called a wedge. I have a wedge.
There are several reasons why you might want to do an accurate polar alignment of your scope. If you want to take photos of sky objects with exposures longer than around a minute (and less if you are really picky about your results) you'll encounter the problems of bad alignment (in both Alt/Az and Polar (equatorial) mode), tracking problems (backlash and other mechanical errors in your GOTO drive), and if you are trying to take long exposures in Alt/Az mode, rotation.
(In Alt/Az mode, the GOTO scope uses two sets of gears to track an object in the sky by moving the scope in two planes, vertical and horizontal. The cost is that the sky appears to rotate around the object being tracked. With a polar alignment, the scope is oriented along the polar axis of the earth so that one set of gears is no longer needed to track an object, once centred, and rotation is eliminated.)
I have a Meade LX200-ACF 8” (203mm aperture) Schmidt-Cassegrain telescope (SCT). It comes with an Alt/Az fork mount. There are very similar Celestron and other brand GOTO scopes. The default Alt/Az mode for these scopes is fine for viewing but not so good for long exposure astrophotography.
People will tell you that doing a polar alignment is the better way to go for astrophotography, and they're right. There are lots of reasons why, but basically it comes down to 'less moving parts', so less opportunities for error to creep in—but more of that later—and, with an accurate polar alignment, there's no rotation to worry about. Error and rotation equals movement and movement is something you do not want during long exposure photos. Again, more about that later.
To do a polar alignment you either need to have an equatorial mount rather than an Alt/Az fork mount, or if you have an Alt/Az fork mount, you need a thing called a wedge. I have a wedge.
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| Meade wedge mounted on field tripod |
