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by labcomputer
386 days ago
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That conventional wisdom is because a Dobsonian is a Newtonian telescope on an altaz mount. The altaz mount, not lack of tracking, is what makes it difficult for conventional astrophotography because the image rotates as you track the star. That prevents using a single long exposure. Equatorial mounts keep the image stationary. |
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1. Long exposures require tracking.
2. Dobbies can't track because they have altaz mounts [0].
3. But short exposures don't require tracking. Therefore a Dobbie might work for short exposures iff you can lock down the altaz axes and sufficiently reduce vibration.
[0] It is possible -- and fairly common -- to track with altaz mounts. Both axes require coordinated, computer-controlled stepper motors. In addition you need a third motor to rotate the tube. This was not possible before digitally-controlled motors. So some Dobbies do track but that kind of defeats the purpose of a Dobbie as a cheap light bucket anybody can afford.
In contrast tracking with an equatorial mount only needs a single motor and that motor doesn't need to be digitally-controlled.