I’m looking to buy an inexpensive hobby telescope and have noticed the trend toward azymuth/elevation mounts rather than equitoral. I know equitoral is simpler since it only takes one motor running at a constant speed to track sidereal movement while an az/el mount needs a computerized controller to move in two axes at once.
My question is about photography. Does the sensor need to be rotated during exposures with an az/el mount? I presume it does. Should I stick to equatoral mounts if I want to do photography? I’m guessing that observatory scopes with an az/el mount like the WIYN have a sophisticated enough controller to keep everything coordinated but does anyone make an amateur scope that will do that?
If you are taking photos, you will need an equatorial mount and a clock drive. Also, you must know how to calibrate your telescope with the celestial North pole so your scope will rotate about the same axis as the earth’s… It’ll take some practice. - Jinx
Yes, photography with an alt-az mount requires a third motor to compensate for field rotation. Big research telescopes usually have this built in to the back of the telescope. For amateur telescopes, Meade sells a de-rotator but I don’t know if it’s computer controlled or not. There may be others. Also, for some alt-az mounts you can buy an optional wedge which converts it into an equatorial mount.
But if photography is your primary goal, I’d go with a refractor or a Newtonian with a classic equatorial mount. Just my opinion though, I admit I’m a bit out of date when it comes to modern amateur telescopes.
I have to disagree with this blanket statement. All modern research telescopes use alt-az mounts because they are more stable and compact. Equatorial mounts must be big and heavy to support the telescope at an unnatural angle.
For amateurs though, a 3-axis computer controlled telescope (altitude, azimuth and field rotation) is a very complex instrument and I think you’d need a fair amount of experience to make it work effectively. Especially if you need to set it up in the field rather than a permanent installation.
Thanks for verifying that for me. I got interested in this when a friend graciously loaned me his Meade 10" Schmidt-Cassegrain for an extended period. I got kind of spoiled but had it long enough to get the hang of aligning it so it tracked correctly and started finding some neat sky objects. I think I’ll settle for a 4-4.5" Newtonian with a German mount and maybe add a R.A. motor later. It’s just for fun now and we won’t be able to use it much unless we go out of town because Phoenix has such severe light pollution. My folks live within sight of Kitt Peak and reasonably dark skies.
scr4 isn’t kidding about the difference in mounts. The 4m Mayall scope is equatoral and has a massive steel horshoe structure it rides in. The WIYN is 3.5 meters but has a relatively small, lightweight mount and the building is a fraction of the size of the one the Mayall is in.
Long term I think it would be a fun robotics project to build a 3 axis controller and mount for a jumbo size Dobsonian scope. I thought about learning mirror grinding but not sure I want to be that much of a renaissance man.