“You need a German Equatorial Mount to do proper Astrophotography….”
This used to be true but with modern Alt-Az technology new options has opened up. Professionals have been working with Alt-Az mounts for years. Now with Track The Stars Telescope Mounts you can get the same advantage in a compact and mobile solution.
The Alt-Az Mount has a vertical and a horizontal axis. Therefore balancing the mount is limited to one axis making it simpler and less critical than balancing a German Equatorial Mount. The vertical Azimuth axle can also be placed directly over the pier center giving optimal load conditions. Additionally the movement patterns makes the mount more compact leading to smaller domes for observatory mounts and easier transport for travel mounts.
Taking astrophotos of the night sky with either a German Equatorial or a Alt-Az Mount demands precise continual tracking. Normally this would be reached in the setup process of a Polar Aligned Mounts by carefully aligning the polar axis to be parallel with the earth’s rotation axis. The Alt–Az Mount on the other hand doesn’t need any polar alignment. When powered up the mount must be aligned on 2 known objects in the sky. This gives it enough info to calculate the precise location of other objects in the sky and to precisely track those objects as they move across the night sky. When tracking objects with an Alt-Az mount what is known as Field Rotation will happen. That can be handled by using the Telescope rOTAtor rotating the whole telescope.
For more comparisons between Alt–Az Mounts and German Equatorial Mounts check out: telescopemount.org.
|Storage and transport||2-3 compact bags||Bulky transport cases|
|Setting up time||3-4 minutes||3-15 minutes|
|Levelling pier and mount head||0 minutes||3-5 minutes|
|Polar alignment time||0 minutes||10-60 minutes|
|Starting up mount and star alignment||2-3 minutes||2-3 minutes|
|Total Start up time||5-7 minutes||18-80 minutes|
|Setting up and tracking in daylight (sun, planets)||Yes right away||Possible using a compass|
|Suited for long exposure astrophotography||Yes||Yes|
|Suited for Autoguiding with guide telescope||Yes||Yes|
|Suited for Autoguiding with off axis guider||Yes||Yes|
|Suited for piggybacking equipment (telephoto lenses)||Yes – balancing can be done with normal counter weights||Yes – balancing demands extra counterweight mounted on the OTA. Piggybacked equipment sits below OTA after meridian flip.|
|Avoids Meridian flip that turns telescope upside down placing equipment in awkward positions and stresses telescope collimation||Yes – OTA always stays in the same angle||No|
|Continuous tracking of an object before readjustment of mount||1-3 hours between derotation of telescope rOTAtor. Continuous tracking through south possible.||6-8 hours east or west of south. Continuous tracking through south not possible|
|Eyepieces stays in an optimal angle at all times||Yes||No|
|Useful for binocular telescope||Yes||No|
|Mounting of more telescopes parallel||Yes - can be done with side-mounted dovetail saddles without extra counterweights||Yes – demands dual dovetail saddles or special tube rings. Extra counterweights must be added|
|Internal object catalogues||Yes||Yes|
|Automatic precise GOTO function||Yes||Yes|
|Computer control via ASCOM interface||Yes||Yes (most GEMs)|