Equatorial v Alt-Az

[CSM]

In an observatory what would be the advantages and disadvantages of using, for instance, a fork-mounted Alt-Az Celestron 9.25 v the Equatorial version?

[steppenwolf]

So much depends on whether the mount will be used for observing or imaging. For observing and Solar System imaging, either would be suitable but the AZ mount would be more 'intuitive' in use. For deep sky imaging, it would have to be an EQ mount.

[brantuk]

One advantage of an equatorial mount is that, once polar aligned, you can just park it and go back to it still polar aligned. With an alt/az mount you'd need an equatoria wedge to do that. So you might as well go equatorial anyway. Presumably you'd want the 925 in an obsy for imaging and it can be bought "ota only" in a variety of metals and weights.

[CSM]

Thanks for the replies. Yes - for imaging obviously the EQ, but how about general ease of use? The Alt will be more compact than the EQ so easier to manoevre around? Less problems over balancing? Less noisy slewing? Any differences in GOTO accuracy?

[brantuk]

The alt/az (of which I have the CPC925) though compact is still quite a bulky bit of kit and getting it up on the wedge requires technique. But it's more dependant on your physical condition (it's about my limit lol). The forks and enclosed motors/electronics and ota all together weigh 26kg (58lbs) and don't break down.

Conversely - popping a carbon fibre 925 up on an equatorial mount like the NEQ6 Pro is much less of a lift. Just stand it on a stool at mount height, swing the mount round till the shoe is lined up with the dovetail, nudge together, tighten up shoe and axes, slip on the weights, and it all swings round into the park position quite nicely with little effort.

But this is more relevant if you intend to be portable. With an obsy you only have to lift the alt/az once. So for general use there's little or no difference in handling. Goto accuracy can be tuned on both setups leaving little difference there. And tracking will be guided so any differences will be down to which software you use, accuracy of set up, and how you handle flexure.

Slewing noise is marginally louder on the alt/az but tracking is pretty much silent on both. The alt/az will require a leg under the wedge for secure balance - but on a pier that's not applicable. Initial setup of the alt/az is a little more fussy than the eq - but again it's a once only thing in an obsy. The EQ mount lends itself more naturally to tracking than an alt/az mount requiring a wedge - and for that reason - if I was using an obsy my personal preference would be EQ. But my scopes all depend on portability and I like to have options lol.

Hope that helps a bit more

[crazyjedi]

I agree with brantuk. In an observatory the EQ mount is a little better. As you'll only be setting it up once, ease of set up is a low relevance

[CSM]

Many thanks Brantuk and Crazyjedi. Just the information I needed.