best lightweight alt-az mount for Apo ?!???!

[madbadgalaxyman (Robert)]

Hi All,

I just joined the tribe of "Apo" owners , recently buying a four inch apochromatic refractor. While most of my nights are usually spent navigating through galaxies data, it is now time to have a bit of fun with a high quality "grab and go" telescope!!

I have had a look at the options available for a lightweight altazimuth mount for the 4 inch apo, and I am NOT impressed. Most of them are actually even worse than the traditional very-closely-spaced set of axes, with microscrew controls, sitting at the top of a tripod. (The unitron 3 inch F15 refractor had an altaz mount of this type)

There is obviously a limit to the stability possible with a lightweight mount, but mounts like the AZ4 and the Vixen Porta II mount, are in (in my opinion) very badly designed.

Many reviewers have said that the Vixen Porta mount, for example, is only satisfactory for the shorter tube Apo refractors.....that the extra torque from the longer tubes is too much for the mount.....but this is not surprising when you actually look at the design of this mount!!!

I would like to avoid the size and weight of a full equatorial mount, for a "quick setup observing session" with the four inch Apo, so does anyone have any suggestions as to a stable altazimuth mount for an Apo??

cheers, madbadgalaxyman

(Oh well, I can always put the apo on my 20 year old Super Polaris mount)

[MikeyB (Michael)]

I've got the original model Vixen Porta Mount and your comments are dead right. It was close to perfect for the weight of my 40mm Coronado PST solar scope but is only just adequate for my 60mm Lunt double-stack. When I tried it with an 80mm William Optics Zenithstar (~5kg, from memory), it was woefully overloaded.

It is also incapable of sufficient vertical extension for lengthy comfortable use by an average height man. If I spent too much time using it, I'd end up looking like the Hunchback of Notre Dame! Presumably it was designed with the typical Japanese physique in mind.

[madbadgalaxyman (Robert)]

The design of altazimuth mount that I had in mind as being much better for refractors than the AZ4 Mount and Porta II Mount is well illustrated by the Unitron altazimuth mount, which was commonly in use some decades ago:



This altazimuth mount was a precise piece of machinery which was not particularly heavy, and it offered excellent precision of motion and excellent stability, even when it was used with a long-tube 4inch refractor.


cheers,
madbadgalaxyman

[madbadgalaxyman (Robert)]

Stable precise Unitron altazimuth mount, with long tube four inch on it: (now a collectors item!!!)




Why have the designers of the current altaz mounts for refractors forgot the basic design principles in the old telescope making books?

[mercedes_sl1970]

A couple of other options, but getting more expensive are the Giro and DM4/6 mounts. I have one of the Giro mounts (MKII/III? - bought here) and it is very smooth and easy to use. I mainly use it for a 4" F13 refractor and am very pleased with it. I either use another small refractor on the other side or ad some counterweights.

Andrew

[madbadgalaxyman (Robert)]

Unfortunately, some of the cheap altaz mounts I mentioned, seem to be - to put it bluntly - only a little better than toys...... due to their very limited ability to cope with significant tube weight and length.

I don't see why many of the small altazimuth mounts that are currently on sale have the telescope hanging a long way to one side of the azimuth axis. Its quite obvious that the tube ought to be right on top of the azimuth axis, in order for better balance: that way, a counterweight may not be necessary.

But thanks, Andrew, for the pointer to the Giro Mark II mount and the DM 4 and DM 6.

I note that on the internet, I recently found a mount designed for the larger and longer apo refractors called the Stellarvue M2
(See: http://www.stellarvue.com

[dannat (Daniel)]

look at the cheaper universal astronomics mounts - i had a microstar & am looking for a unistar now - they are compact & well built..you can get guide handles & other bits pieces for them. larry's shipping is reasonable from the states

another option is this one from telescope express in germany Technosky Alt-Az
i know it says its for bins but i heard a german on a forum saying it handled a scope nicely - it just doesn't have slo mo controls

mostly these options require a good tripod with 3/8" thread