Vixen APZ reconfigured with encoders

[Stephenstargazer]

I have had a manual Vixen AP Equatorial for some years and always admired the quality of its mechanical modules which provide very smooth push-to and the silkiest slow motions. The negatives were lack of go-to with the (expensive) motors and quite a bulky mount for limited capacity. I used it in AZ format too. I looked for a possible encoder kit, that might be modified.  I wanted a compact mount with slow motions and digital setting circles, ideally avoiding the weight of motors, a battery and counterweights. An idea came to me that the modules of a Vixen AP can be configured to a half fork AZ mount. I did not need to accommodate long scopes so it could be made very compact. I already had the Astro Devices DSC on a Rowan AZ100 mount to use with longer and heavier scopes.

The body and counterweight of an APZ are replaced by a pair of plates at right angles, which then provide the surfaces to mount encoders. To prove that this was feasible I made a trial with plywood, which worked OK as a manual mount and helped sort out clearances. To support encoders I decided the accuracy of aluminium plates would be better. I worked out a way of adding encoder shafts inside the Vixen modules with minimal modification. A friend kindly did the major machining on the plates, but I did the rest myself.

Although Vixen sell AP modules individually it maybe cheaper to start with a whole APZ. at £570. The CUI AMT102 encoders, metalwork, fixings, wiring, sockets, etc cost less than £75 all sourced in UK. Nothing prevents me from restoring it back to it's Vixen configuration. The 'new' mount has now been tested on the sky and works better than the original for damping and rigidity. It measures 230x78x115mm, weighs 2.3kg, and conservatively will carry 5 kg without a counterweight. The DSC works perfectly with the encoders , which are not hi-res, that part of the project was the easiest!

The photos start from the test prototype, an encoder shaft in a slow motion, parts bought, final assembly, with my smallest scope mounted and the whole kit in a camera case (except an AP tripod!) ready to travel to unfamiliar skies. 

 

 

[Space Hopper]

Ingenious, and a very compact set up with the little Questar 👍🏼

[Franklin]

Looks like a very clever modification to an already remarkable little mount. I love my AP, it's a one-off in the world of mounts, but as you say it does lack capacity. Vixen put it at 6kg, but in the manual APZ mode they increase to 8kg. I have ordered an APZ base but am still waiting on delivery. My AP has dual motors with the Starbook1 but also has the manual modules, when the APZ base arrives I am hoping to use it with the dual motors in alt-az mode but I think the 6kg capacity is the limit on the motors.

[Stephenstargazer]

@Franklin Vixen are good at not overstating capacity. My own take is that the difference between AP and Z is that the Eq base has an extra joint that flexes. It pays to tighten the  polar declination joint once set for latitude.

The motors are slow, but think bearings etc similar to manual, should not be troubled on balanced mount?

May PM you about manual slow motion modules. OK?

@spacehopper It is also my mount of choice for FS60CB!

Edited March 28, 2022 by Stephenstargazer

[Deadlake]

I've seen a TSA-120 on a Vixen APZ in Alt mode.

How realistic would it be to mount a 7 kg scope on the APZ?

I'm after a mount which can take a 7-8 kg with slow mo's, this could be it...

[Stephenstargazer]

I am always wary of overloading mounts as I don't  like much vibration. The weakness (and advantage!) of the AP is the connections between modules. If the scope is too heavy or not well ballanced  then the worm drives or joints can be affected. For the mechanically minded the worm drive clearance and bearings can be re-adjusted in 6 places, as they are during factory assembly. Do not overtighten any of the screws, risk of stripping fine threads  in aluminium ,

If you try an APZ with a larger scope you should use a counterweight bar in place of the fixed weight (based on my experiences). The APP tripod is less rigid than the HAL.

If your 7kg is the total weight of scope and all attachments  then it could be viable. There is a diagram in the AP manual showing the balance requirements.

[StarryEyed]

Thats excellent work. Appriciate your metal work skills. If the plates came of a milling machine it would be a quality upgrade that might even have a market.