ADM MDS Review

I have battled with my home-made ST80 mounting system for long enough. Finally, I conceded defeat and after researching the merits and prices of a number of different types of mounting systems, I settled on the Mini Dovetail System (MDS) manufactured by Anthony Davoli Machining (ADM). On this page I review the MDS.

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Review
Illustrative Images

Ordering and delivery

After an interchange of emails between Anthony and myself, where I sought further information about the MDS system and Anthony diligently responded to each message, I finally ordered the MDS on the 10th of December 2004, paying by PayPal. The ordering process was straight-forward.

The MDS arrived at my address on the other side of the planet (Tasmania, Australia) on December 24 (Christmas Eve) - slightly less than 14 days from the date of order. The various components were well hand packed and each arrived in good order.

First impressions

My order included 2 x dovetail bars, 2 x 125 mm rings, and the counterweight system. At first I was struck by the large size of the 125 mm rings and the sturdiness of the design in general. The aluminium ring screws were large and easy to use. The dovetail bars also were sturdy if not a little weighty by my reckoning. The dovetail blocks that attach to the rings are fitted with plastic head metal thumbscrews that lock the rings at any position along the dovetail bar. When locked there is no lateral movement in the system whatsoever.

All metal components, except for the aluminium screws, are black anodised aluminium. Although the machining workmanship was very good, the finish was imperfect (see below). In no way did this detract from its usefulness. The large aluminium ring screws were noisy to screw, owing to the fit between aluminium and aluminium. This can be rectified by applying a small amount of Vaseline (petroleum jelly). Although the MDS is advertised to attach to the LX90 OTA using the existing mounting screws, it does not. I discovered this the day after receipt when I was attempting to attach it to my OTA. Curiously, on the same day I received an email from Anthony who had correctly anticipated that I might have this problem. He offered to ship some longer stainless steel screws and these recently arrived.

As I see it, here are the pros and cons of the MDS.

Pros	Cons	Suggested con modifications
Excellent design - allows complete freedom for placement of the ST80 and counterweight along the dovetail bars. Locking mechanisms are firm.	Imperfect finish - In some places the black anodising was incomplete leaving a reddish stain and there were various scratches and indentations on the rings and dovetail bars (see mod).	Accept imperfection; its a part of life :-)
Sturdiness - there is no lateral movement after locking the system. It is sufficiently solid to ensure no flexure.	Ridges on the underside of the dovetail bars - unfortunately, these can (and did) indent the OTA when tightened down (see mod).	Dovetail bar spacers - a soft spacer (I used gaffer tape) needs to be used to raise the dovetail ridges off the OTA and to protect the OTA finish. Incidentally, a spacer applied also lifts the bar slightly above the blue painted surface of the LX90, which is needed.
The counterbalance distance from the OTA is easily adjusted by rotating it up and down the threaded rod.	There is no mechanism to lock the counterweight firmly in position (see mod).	Counterweight lock - I used a wing nut and washer and locked the counterweight by screwing it down. Incidentally, the diameter and thread size of this rod exactly matches that of the central tripod rod for the LX90. Many people also use a wing-nut mod for the tripod to ensure even spread of the legs.
Alignment screws have Delrin (an engineering plastic with metal-like properties made by Dupont) tips that guard against scratching the guide-scope finish.
Lighter than competing systems - this is important to reduce wear on the DEC gears.
Good price (including delivery to Oz) - competing systems (eg. Losmandy) appear to be substantially more expensive.
Balances my Sky-Watcher ST80 perfectly (horizontal and vertical) with the supplied 3.5 lb weight.
125 mm rings allow ample movement to align an 80 mm guidescope to stars outside the standard FOV. This is particularly handy for when a suitable guide star cannot be located. I have not yet calculated the range of movement in degrees.

Illustrative Images

Side-on image showing the MDS attaching a Sky-Watcher 80 mm short-tube refractor to Meade's LX90

A close-up view of the MDS and 125 mm rings. You can see the position of the alignment screws and their Delrin tips. Note the method of fixing the dovetail bar to the LX90 OTA was improvised until the the new bolts arrived. Here you can see a screw and rubber washer. The correct bolts fit into a recess and cannot be seen. Also visible is the gaffer tape mod to raise the dovetail bar slightly off the OTA.

Underside of the Lx90 showing the counterweight attached to the underside dovetail bar. The wing-nut modification is being used to lock the weight into position.

ADM Mini Dovetail System - Review