Skywatcher HDT Mount
Gregory Wuestenhagen

Here with the tripod is fully extended, with the Synta 150 (6") f/8 refractor, properly balanced.  The pivot point of the DEC axis with the tripod fully extended and pointed north is at 67.5" in height.   

I purchased this mount from Hoon Hiu, a Synta importer / retailer from BC Canada.  His price was over $200 less  than I've seen from any other source.  He charges $80 for standard shipping (7 business days to the east coast) and  $140 for 3rd day shipping.  He is very pleasant to deal with.

The EQ-6 mount head weighs about 38lbs, the tripod about 17.  It is supplied with two counterweights, which look  like CG5 counterweights, but the bore is smaller, to fit the retractable counterweight shaft on the  HDT. The HDT  counterweight shaft is about 1/8" less in diameter than that of the CG5 / GP series mounts.

The major 'knock' that I have against this mount is the (in my opinion) too short, too small (diameter) counterweight  shaft.  They were too 'cute' on this detail.  I would have preferred a 1" c/w shaft that screwed into the mount and  was at least half again as long.  The stock c/w shaft is 23/32" diameter (smaller than that of the CG5) and extends
only 9.5" from the mount, or 16" from the center of rotation of the RA axis.  As a result, using a large diameter  ota, especially if there are accessories mounted on top (like a super finder),  the ota center of gravity is farther  away from the center of RA axis rotation than the counterweight shaft end.  Since you cannot get the center of
gravity of the counterweights as far away from the RA axis of rotation as the center of gravity of the payload,  it takes more weight on the c/w shaft than ota payload to come to balance.  This should not be the case.  However,  I should tell you that the mount seems to be able to carry the C11 with accessories,  giant rich field viewer, 2"
diagonal, 16x70 Polaris finder, heavy 2" eyepieces etc., even though it takes 36lbs of weight to counterbalance  this payload. And it does so without any hint of strain.

The polar scope is almost identical to the one on the old Super Polaris mount, and much better than that on the CG5.  However, apparently the first of these mounts had the cheaper polar scope.  This mount has a very heavy, think
and nicely made polar scope cover that screws onto the back of the mount - much nicer than the press on covers  that never fit well.  But it's a little hard to get the threads started right - it might need a little cleaning up.

This mount has locking levers that look a little bit like those on the CG5 mount, but they're much heavier duty,  and they work well for setting friction on the axes so that you can move your scope manually but continue
tracking without interruption.  Some have reported that when locking these levers the corresponding axis moved  a little.  My mount does not do this.  In fact, I find the levers to work great as clutches for setting friction / tension to allow me to move my C11 ota by hand, and yet retain accurate tracking.

The counterweight shaft rotates with the DEC axis, and the polar scope rotates with the RA axis. This should make  it easy to fit optical encoders to this mount.  I prefer this type of setup to the type or hand controller that counts motor
rotations to plot celestial coordinates.  With those setups (i.e. they Dynostar), you loose accurate coordinate information  if you move the mount manually (without the motors).  With separate optical encoders, you can slew the scope manually
to your hearts content and maintain accurate coordinate information, even when flopping, as long as you don't do it so  fast as to cause encoder errors.

Over time I will be adding information about my ongoing use of this mount.   Here are some general first impressions  and information:

The azimuth adjustment in the base of the mount uses two opposing screws pushing against a piece of metal that  is screwed into the head plate of the mount.  There are two holes on the mount head plate into which this can
be installed. You can install it to have one one leg pointed south as shown above, or reversed so that one leg is  pointed north.  I strongly recommend installing so that one leg is pointed north, underneath the counter weight bar.  When two or more weights are installed on the counterweight bar preparatory for mounting a large optical tube,
you need that one tripod leg underneath the counterweight bar or the mount wants to tip forward toward the counter  weights.  The tripod head plate can be seen in the picture below.

The RA and DEC setting circles are really nice, very readable, not as finely graduated as I'd like, but they are going to do the trick.  They rotate independently of the axes and can be locked in place with either or both of two small knurled screws, 180* opposite each other, so one will always be in easy reach.  These setting circles are very easy to read, and can be read from one convenient location at the top back of the mount from either side.  These may not be finely graduated, but they are going to be easy to see in the dark with a led flashlight, or one conveniently mounted led light here out of
harms way on the back top of the mount.  The setting circles seem well made, and feel really nice in operation.

If you've seen the hand controller of a CG5 or GP mount, this looks the same, but for the 16x slewing speed.  The phone type cord that connects the hand box to the mount is coiled, and seems heavy duty. However, the RJ type connector fits
loosely into its receptacle on the mount, and the red light indicating power to the mount goes on and off depending on how the cord is moved or stressed.  I used a small piece of tape over the base of the clip to tighten it up.

One of the annoying things about many of these hand controls with separate battery pack is that the battery pack power cord fits into a receptacle on the hand control. With these  you have to watch the position of the battery cord when moving about
with the hand box.  On the HDT mount, the power cord connects directly to the side of the motor box on the mount, so the hand box is not tethered to the battery box - a big usability improvement. However, the tip of the power cord does not
properly fit the connector in the side of the mount - it's loose, and can be very easily and inadvertently pulled out of the mount.  On the other hand, if you've been used to a CG5 mount, the 16x slewing speed is really nice.

The tripod is very nice - pretty much as heavy but more nicely built than my Meade adjustable SCT type field tripod.  Very sturdy even when the legs are extended, though I've read other reviews that have mentioned some periodic vibration with
the legs fully extended.  However, they only have one locking lever per shaft.  I would have preferred the security of two locking bolts per shaft as on the Meade SCT type adjustable field tripod.

The external finish of this mount is much better than that of any EQ4 /CG5 or EQ5 mount I've seen.  And in my opinion it seems very well made, considering that the base and housings are all castings.  The black powder coat finish
is very nicely done.  There are just a few things that detract from what would be a good impression - the latitude scale is sloppily glues into a recess in the side of the mount with glue overruns (The EQ6 medallion is nicely done though!),  the
pointer for the altitude scale looks fragile, the removable panel on the side of the motor housing is not particularly well fitted.  The really important stuff is all there.  It will be interesting to see if future examples of the mount fix a few of these minor detractions.

Oh, an interesting note - I have a handful of vixen GP type mounting plates - NONE of these will fit the HDT head.  It is more than 1/16" too narrow for them.  A C8 dovetail bar fits fine, as do generic CG5 dovetail bars.  The mount comes with one
dovetail bar, extruded aluminum, about 8" long.  I found one CG5 mounting plate - it does not fit either.   On the other hand, the dual bolts that hold a dovetail bar on the HDT mount head should be very secure.

If you've been used to slow motion controls, you wont find them here, which is typical of the heavy mounts.  You won't miss them with this mount.  Just set the friction on the locking levers so that you can move the scope around with a
little effort.  The mount continues to track properly and you can quickly make fine corrections, even through a finder scope, with the 16x slewing speed.

So far I have not used this mount with any OTAs heavy enough to begin to challenge it.  I will tell you that it handles a C11 as though it weighed nothing at all.  Tracking seems to be excellent.  I centered Jupiter in a 26mm crosshair
eyepiece and 2x barlow combination for about 211x in a C11 and left it to track for 45 minutes.  Jupiter had moved about a planet's width in DEC due to inexact polar alignment, but was still exactly on in RA.  Some have reported
some jittering noted at exceptionally high powers - I saw none with this mount at 392x with a 7mm Nagler on Saturn and Jupiter.

I plan to test this mounts tracking with various optical tubes, and also to test for periodic error.  Reviews I have read suggest that the periodic error of these mounts is quite low.

NOTE: If you plan to mount a C11 or C14 on this mount (either of which it will easily handle) you will need to mate a CG5/EQ6 dovetail bar to the Losmandy DC11 or Celestron CI700 dovetail plate supplied with the optical tube. It is best, in my opinion, to work it out so that when the smaller dovetail is attached to the EQ6 head,  the larger is
riding snugly against the top of the RA axis head, even if the smaller dovetail bar does not fully rest on the bottom of the recess in the mount head.  This makes a huge positive difference in vibration characteristics.

Also see Greg's website at http://www.geocities.com/g_wuestenhagen/astro1.htm for more photos.