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View from a Scope | July 25, 2021

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Mounting Pressure

Mounting Pressure

Choosing the right mount for your telescope is every bit as important as choosing the right telescope. A good mount will allow you scope to remain steady and really enhance your viewing pleasure. Below I will run through some of the common types of mounts available.


The typical beginners scope often come with a simple but crude altazimuth (alt-az) mount. However, with the introduction of smooth yet solid alt-az mounts, Many astronomers are turning again to this type of mount. It allows for a grab and go , no fuss setup and is ideal for smaller telescopes. The alt-az mount is not suitable for deep sky astrophotography because of the way it moves. The mount can move the scope right or left known as Right Ascension or up or down, known as declination but it cant do both at the same time meaning tracking a star as it moves across the sky is done in steps, a little right and little up like climbing stairs.







Like any alt-az mount, the Dobsonian mount moves side to side and up and down, but it cannot track the stairs. However some Dobs offer computerized finding – you push the scope around the sky until the display indicates you are on target. These scopes help you find targets but cannot track them.






German Equatorial

To track objects and keep them centred in the eyepiece, all you need is  equatorial mount with one axis polar aligned and driven at the sidereal rate by simple motor. Computers and fancy programming are not required. However many German equatorial mounts are now equipped with computerized motors that can slew to and find objects and track them once on target. For these functions to work the mount must be polar aligned (the polar axis aligned to the celestial pole) and synced to 2 or 3 stars to calibrate the computer GoTo system.



Auto Tracking

This new class of computerised mount can track the sky but not find things. It is not a GoTo system. You must find objects yourself by electrically slewing the telescope – you cannot grab and push the scope around the sky. This can make using this type of mount awkward. This alt-az mount does not require polar alignment, just a simple initial aiming towards north, then adjusting the angle of the tube to match your local latitude. That information is all the mount needs to track objects well enough for casual viewing. For not much more money you can a full GoTo system on a nearly identical mount.



Full GoTo Mount

This type of scope can find and track objects. The fork mounted models can be set up in altazimuth mode not requiring polar alignment. Each night the scope must be aimed at and synced to 2 or 3 stars to calibrate the GoTo system. After that the telescope can be instructed to slew to any one of thousands of objects. Once on target the computers then pulse the two motors (one on each axis) to keep the object centred. When buying a computerised mount be sure to know its capabilities, Can it find?, Can it track? Can it find and track?



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