Why no AZ mount for 130mm(5 inch) or larger aperture

[aiesh_kaul]

Hi Everybody,

I am new to astronomy and have been browsing through different telescopes. I thought a Newtonian Reflector with 130mm (5 inch) aperture on a AZ mount would be something good to start with as the EQ mount looks like something complex for me at this stage.

But what I see is after going through different brands, no brand comes with a 130mm (5 inch) or greater aperture on AZ mount. All of them have an EQ mount.

Is there a technical reason behind this? Any suggestions would be much appreciated.

Thanks,
Jimmy

[julianh72]

It's called a "Dob" (Dobsonian)!

[Renato1]

A decent AZ mount for a 5" would be pretty expensive.

If instead of setting the polar axis of the equatorial mount to your latitude, you set it to zero, you have a mount that performs exactly the same as an AZ mount.

Don't get too hung up about using an inexpensive equatorial. Even after you set the polar axis to your latitude, no one says you have to line it up with the South Celestial Pole in order to use it. You can just take it outside, plonk it any position and use it, though you will be using both slow motion control cables to track an object (just as you would an AZ mount). If you do line it up roughly with south, you just won't have to use one slow motion cable as much as the other when you've found you object.
Regards,
Renato

[Tamtarn]

I have this one with goto. A quick 2 star alignment and away you go.
http://www.ozscopes.com.au/skywatcher-130-650-azgt-reflector-telescope.html

Barb

[julianh72]

Looks identical to my Celestron NexStar 130 SLT.

[raymo]

I would suggest that manufacturers assume [rightly or wrongly] that most people that buy scopes larger than around 100mm, are fairly
serious about their hobby, and would like to be able to track the stars
using one axis only. EQ mounts suitable for Newts up to 150mm are
cheap [ EQ3 for example]. With just an R.A. motor and rough polar
alignment you can track well enough for visual work. One session with a basic EQ mount is all that is needed. Just plonk it down with the
counterweights facing approximately South, and the motor will keep the target in view for quite a while. Alt/Az mounts for larger scopes are available, but are pricey. Manually operated Alt/Az mounts are a pain.
raymo

[Merlin66]

http://www.green-witch.com/skywatcher-az-eq5gt-alt-azimuthequatorial-compuerised-go-to-mount--pier-tripod-3074-p.asp
What about this?

[aiesh_kaul]

Thanks for the response guys. But these ones are all GoTo scopes and I am looking for a manual one. Is there a manual one ?

Thanks,
Jimmy

[raymo]

You don't have to use the Go To on these mounts. You can find your own way around the sky using the motors.
raymo

[julianh72]

A basic Dobsonian mount is a fully manual Alt-Az mount.

The Celestron SLT mount only works as a powered mount (you can push it in Altitude, but I think you would damage the Azimuth drive if you pushed it to slew horizontally), but you can just drive it around the sky if you can't be bothered aligning it. (But seriously, it takes about two minutes to do a 2-star align, and then it will find and track any target, so why WOULDN'T you align it at the start of each viewing session?!)

The computerised Go-To fork mounts can be used as a manual mount by just releasing the clutches and pushing it around the sky, or you can drive it with the motors without aligning - but again, alignment on the modern mounts is quick and painless, so it is worth learning how the process works.

If you're asking why it's hard to find a basic Alt-Az mount bigger than an AZ-3 - I think the answer is that there's probably no real call for it - but if it bugs you, as noted by an earlier poster, just put your EQ mount with the polar axis horizontal and Voila! - it is now an Alt-Az mount!

[barx1963]

This http://www.ozscopes.com.au/skywatcher-heritage-5-dobsonian-telescope.html is a Newtonian (remembers all dobs are also newts!) ona full manual AZ mount (remember all dobs are AZ mounts!)

Malcolm

[DavidLJ]

This one has very good reviews and is "as simple as" to use.

http://www.myastroshop.com.au/products/details.asp?id=MAS-033A4