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A GOTO reunion with a Mark-X

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#1 PawPaw

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Posted 17 August 2020 - 11:18 PM

I wanted to share with you two of my recent finds that became a GOTO reunion.  I have to thank one of our own CN members (Bob) for the opportunity to acquire a GOTO 80mm semi-apo 12.5 OTA.    I had done some research on GOTO before acquiring this gem and in the back of my mind thought what are the chances of mating this classic GOTO with the mount it was designed for?  My intention was to try and find the elusive Mark-X mount that these scopes were designed with.   They show up now and then in the Japanese market but don't last long as they are highly regarded mounts in Japan.   GOTO Opt started the Mark-X project in the 1970's after their market of school telescopes became saturated.  There is an excellent article on the history of the Mark-X on GOTO optical blog site and it is an excellent read.  I won't go into details here on the history but much of engineering details we  find so essential in our modern mounts we owe some of their  lineage to a few Japanese companies and one of those was GOTO.  

 

I want to start with some of the details of my Mark-X mount.  My plan was to use it for several sessions, maybe a month, and then write up my findings.  After a week of putting the Mark-X together and taking it  back apart, confirming the tracking and completely enjoying its engineering from the 1970's I  could not wait any longer.  There is no denying just looking at it there is a clear lineage still used on some of the better GEM mounts being made today.     My goal is not to say this mount is better than  X or Y is better than Z but just to share what I find.  This will likely take  me a few posts, so bear with me, as I want to point out some of the details that still make this  mount a robust "multi purpose equatorial system".   I will start with a few pictures here and try to add something every day.  Note the mount itself is complete and original but minus the original tripod legs......(working on that).  For now it resides on a Vixen aluminum tripod.  

 

The mount came with the following sub-systems: 

 

1:  GOTO MX-1 base model, RA incl polar finder

2:              MX-2 DEC shaft

3:              MX-3 Base mount

4:              MX-4 Universal Plate

5:              MX-50 tube holder for 95mm OTA

6:              MX-10 qty:2 3.3kg counter weights

7:              MX-28 comet tracker motor drive with dual axis control and manual

8:              GOTO Mark-X original catalog  

 

GOTO meet GOTO

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Edited by PawPaw, 17 August 2020 - 11:25 PM.

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#2 PawPaw

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Posted 17 August 2020 - 11:21 PM

A few more pics:

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#3 clusterbuster

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Posted 17 August 2020 - 11:46 PM

Very Nice, I love that BLUE color also.

 Refractors RULE...

 Mark



#4 jcruse64

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Posted 18 August 2020 - 06:05 AM

That is choice!



#5 Van Do9:3

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Posted 18 August 2020 - 06:22 AM

Great work researching and putting together an awesome Goto set. Thank you for sharing. 



#6 PawPaw

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Posted 18 August 2020 - 07:23 AM

According to GOTO they were the first to incorporate a polar finder in a mount.  Before the Mark-X GOTO had a mount called the "Portable Hoshino Photography Equatorial Mount" it was a prototype mount and likely the first to have a polar telescope built in.    The Mark-X was designed for astrophotography so they incorporated the polar telescope in its design.  One main objective was to make the mount portable through simple disassembly.  The whole mount comes in four parts and put together with what GOTO calls an "Inro joint" like the joint of a machine tool. Each part is joined with 4 hexagon socket bolts.  The four main parts are:  The mount, the base model (polar axis), the declination axis, and the tube receiver (OTA cradle).  All put together my mount weighs approx 27lbs with one 7.2 lbs counterweight.  While most of the mount is machined aluminum there are heavier metals used in key locations.  Here is a illustration of how the mount goes together with one allen wrench.

 

 

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#7 starman876

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Posted 18 August 2020 - 07:41 AM

beautiful scope



#8 Dave Trott

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Posted 18 August 2020 - 10:18 AM

What a wonderful write up of a truly significant and overlooked vintage mount! As I understand the picture, you could use the tube cradle by itself or substitute the mounting plate on the declination axis to hold a scope and camera side-by-side for astrophotography. Apparently you could also omit the declination axis completely to make a simpler tracking system with a little guide scope and camera. I imagine a camera on a ball head and a separate tiny guide scope on it's own ball head; like a barn-door mount. Is that right?

 

I wonder if the GOTO Mark X was the inspiration for the Takahashi Space Boy Mount (picture below)?  These modular mounts are completely fascinating! A more modern example is the Takahashi Sky Patrol.  

 

And the first use of a polar alignment scope is remarkable. Typical of GOTO to be one of the major innovators in telescope design.

 

Thanks for a superb thread PawPaw!

 

SPACEBOY


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#9 Terra Nova

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Posted 18 August 2020 - 10:28 AM

What a wonderful scope and mount! I love the color and construction of the GEM and Goto scopes are excellent. I had two of their achromats. Congratulations!



#10 PawPaw

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Posted 18 August 2020 - 01:13 PM

Thank you all for the kind words....I feel very lucky indeed on taking care of this GOTO system.

 

 

"What a wonderful write up of a truly significant and overlooked vintage mount! As I understand the picture, you could use the tube cradle by itself or substitute the mounting plate on the declination axis to hold a scope and camera side-by-side for astrophotography. Apparently you could also omit the declination axis completely to make a simpler tracking system with a little guide scope and camera. I imagine a camera on a ball head and a separate tiny guide scope on it's own ball head; like a barn-door mount. Is that right?"

 

Dave you are spot on.....I have asked permission to use photographs from GOTO's catalog on the Mark-X and have not yet received a response.  As you know a picture (better yet a video) says a thousand words.  The flat mounting plate that came with my mount was specifically designed to broaden the scope of applications.....Plus it could be installed on the end of the declination axis or the polar axis and also the mount base itself.  They designed it to use a variety of camera/universal heads.  In addition to the flat mounting plate a "General Purpose Axis"  (Complete with hole for polar scope) was available and had a pair of symmetrical flat truncated ends for the installation of observation equipment.  Get this it also came with L-Formed mounting plates that bolted to this general pupose axis.  A large sized skygraph could be mounted.    One of the GOTO examples shows a gang of 8 35mm cameras 4 mounted on either side on the L-plates.  The Polar Axis base was also designed so it could be mounted on a variety of camera tripods fitted with a flat plate.  

 

Cheers

 

Don


Edited by PawPaw, 18 August 2020 - 01:18 PM.

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#11 PawPaw

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Posted 18 August 2020 - 05:11 PM

I had some time today to play with the assembly and disassembly of the complete mount.  I decided to time how long it took for both and without rushing here are the results:

 

disassembly:  A  little less than 4 minutes leaving the tripod hub attached to the legs.

assembly:  5.5 minutes.

 

I attached some 95mm rings to the universal plate just to verify they fit.......Yes they do.

 

I will let the  pictures speak for themselves since I don't have Dave Trotts video skills.

 

 

 

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#12 PawPaw

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Posted 18 August 2020 - 05:17 PM

GOTO clearly wanted this system to last....note that each receiver for the hexagon bolts has a helisert installed in the aluminum mount.  They must have been concerned the aluminum threads would strip out over time.  I have never seen a counterweight bolt that had a teflon tip glued into the end of the brass bolt.

 

 

 

 

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#13 PawPaw

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Posted 18 August 2020 - 05:32 PM

The Drive units were called P-type motors, the P standing for pulse.  They are extremely quiet and have the ability to be mounted for either Northern or Southern hemisphere use by simply switching sides.   GOTO measured the eccentricity error of each worm shaft machined where it was fitted with the worm wheel.  According to their records they kept the error within a few microns.

 

The motor itself is mounted in a fashion that reminds me of how Edmund mounted their motors although Edmunds was essentially a Ujoint and not as precise.  GOTO found through testing that  when mounting the Motor drive  on the equatorial mount, it was found that Periodic motion was significantly reduced when the drive was mounted via a long-hole connecting metal fitting that functions as a rotation stopper, rather than being firmly fixed. In response to the test results, a U-shaped connecting fitting like the one in the picture was devised, and the result was very good.  

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Edited by PawPaw, 18 August 2020 - 10:59 PM.

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#14 Dave Trott

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Posted 18 August 2020 - 10:00 PM

Wonderful write-up and pictures, Don!

 

Wow, this thing screams class! It sounds like the engineers at GOTO really put some thought into that clock drive mounting system. I don't think I have seen that innovation on other mounts, though. Seems like it would be a very simple improvement for an inexpensive motor mount.

 

- Dave


Edited by Dave Trott, 18 August 2020 - 10:01 PM.

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#15 PawPaw

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Posted 19 August 2020 - 07:29 AM

I was given permission from GOTO Optical to use pictures from the catalog and literature I received with my mount.  The catalog is not dated but it is likely from 1985 or 86 because the MX-28 (Comet Tracker, more on this later)  was designed in part for the return of Halleys comet.

 

My inadequate explanation in post 10 can be explained so much easier by pictures.  So you can "See"  the versatility:

 

 

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#16 PawPaw

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Posted 19 August 2020 - 07:31 AM

More catalog pictures:

 

 

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#17 PawPaw

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Posted 19 August 2020 - 08:01 AM

It sounds like the engineers at GOTO really put some thought into that clock drive mounting system. I don't think I have seen that innovation on other mounts, though. Seems like it would be a very simple improvement for an inexpensive motor mount.

 

Dave......Goto also came up with another drive accessory for  the Mark-X.....it was called a "deceleration fine movement device".  Essentially it is a reduction fine control device that steps down the rotations of the worm gear at a ratio of 11 to 1.  It enables delicate manual fine-adjustments on either declination or RA.  

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#18 Dave Trott

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Posted 19 August 2020 - 12:34 PM

I have seen pictures of a Takahashi Space Boy mount bristling with multiple cameras in the same way the Mark X is loaded up in one of the pictures. Pedro Rey has a history of Takahashi telescopes at http://www.astrosurf...telescopes.html . He shows the first Space Boy mount in the early 1980’s. It seems reasonable to conclude that the Takahashi Space Boy was inspired by GOTO’s Mark X.

 

And here is a picture of my old Tak Sky Patrol mount that dates from the early 80’s. It seems to mimic the GOTO Mark X. As you said earlier, Don, the lineage of many modern telescopes descends from GOTO.

 

Takahashi Sky Patrol

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#19 PawPaw

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Posted 19 August 2020 - 02:11 PM

Here is the Mark-X system diagram from the catalog.  I have found several other companies such as Carton and Vixen that followed suit and used a similar schematic diagram in their catalogs. 

 

My base mount according to the previous owner is from 1978 but the comet tracker dual axis drive was purchased in the mid 80's and added to the mount.  The only changes in production to the base mount were new releases of the  updated stellar screen for the polar scope however GOTO continued to design upgrades to the Mark-X through its lifetime.  Even though the mount itself ceased production in the late 1980's?  It speaks volumes to the longevity of the design that GOTO's  last upgrade was made available in 2017 which was a new dual axis drive called the Giyo equator 2 axis motor drive......It was available in limited quantities and sold out very quickly.  The motors for this new drive system were mounted in the same configuration as mine.   Here is the link:  http://gototelesco.c...tml#motor_sales

 

GOTO still provides maintenance on these mounts as mine was sent to GOTO for repair maintenance in May of 2019.  The repair was to the counterweight clamp which was likely the replacement of the teflon tip on the bolt.  They also removed old grease, added new and adjusted the worm wheel and gear and tension of free turn.  It is admirable that a company continues to support their product 42 years after the sale.  

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Edited by PawPaw, 19 August 2020 - 02:15 PM.

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#20 Dave Trott

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Posted 20 August 2020 - 10:56 AM

It sounds like the engineers at GOTO really put some thought into that clock drive mounting system. I don't think I have seen that innovation on other mounts, though. Seems like it would be a very simple improvement for an inexpensive motor mount.

 

Dave......Goto also came up with another drive accessory for  the Mark-X.....it was called a "deceleration fine movement device".  Essentially it is a reduction fine control device that steps down the rotations of the worm gear at a ratio of 11 to 1.  It enables delicate manual fine-adjustments on either declination or RA.  

I have been trying to figure out how the "deceleration fine movement device" was supposed to be used. Apparently it was a sort of manual tracker to be used without the clock drive, allowing the mount to function like a basic barn door tracker with a pointer you would turn by hand. This would make simple wide field astrophotos possible with no electronics. This was in the bad old days of film so such a device would have been useful for exposures of several minutes. The real trick would be making those fine adjustments for a few minutes without bumping the camera!


Edited by Dave Trott, 20 August 2020 - 10:58 AM.

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#21 KentTolley

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Posted 20 August 2020 - 02:38 PM

Good job putting the scope back together with its native mount. It's a real beauty. You must be proud. It shows a very high level of care put into an amateur scope and thst is admirable. I expect it will be a joy to use and that it won't disappoint optically.


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#22 PawPaw

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Posted 20 August 2020 - 04:07 PM

Thanks Kent.......The complete system was well taken care of by the previous owner/owners.  I do know that Bob owned the OTA since the late 90's and it is in amazing shape for being all original.  He never removed or cleaned the objective and it still shows very little spotting from dew.  

 

I have a few more notes to share about the mount before I move on to the objective and OTA.....I would be remiss not to share the build quality of it on this thread.  It is after all a reunion of design!

 

I want to speak about the drive system controller.

The MX-28 comet tracker dual axis drive was developed in response to the return of Halley's comet in 1986.  This was the 3rd generation drive designed for the Mark-X mount.  The drives work on 12 vdc and  use a crystal oscillation frequency divider circuit utilizing two internal gears for output.  Both RA and Decl can be set from 0 to 9,999, and it was possible to track according to celestial bodies that move differently from stars such as comets. 

 

The control box can be set for two different modes......a "Fixed mode"  that uses sidereal time and a "comet mode" that can be set from 0 to 9,999.  Tracking can be set for Star (5000), Solar (4986), lunar (4817)  or other celestial body tracking such as a comet.   Tracking speed and turning direction is set by by the "Rate" dials in both RA and Dec.  One (1) set is 4.33' in movement for one day 24 hrs.  

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Edited by PawPaw, 20 August 2020 - 04:32 PM.

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#23 PawPaw

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Posted 20 August 2020 - 04:52 PM

I have been trying to figure out how the "deceleration fine movement device" was supposed to be used. Apparently it was a sort of manual tracker to be used without the clock drive, allowing the mount to function like a basic barn door tracker with a pointer you would turn by hand. This would make simple wide field astrophotos possible with no electronics. This was in the bad old days of film so such a device would have been useful for exposures of several minutes. The real trick would be making those fine adjustments for a few minutes without bumping the camera!

Dave......There is a very nice report by Suzu on the reason for development and how it was implemented  here:

 

https://blog.goo.ne....2bc871e82105596

 

Look under "Mark X Story (10)

 

Here is a snippet of the blog:

Episode 10: A deceleration fine movement device that became a manual MD

As a drive accessory that has been in existence since the Mark X system was released, there was a product called a deceleration fine movement device. When taking astronomical photographs with superfocus photographic lenses and telescopes, the RA can be delicately tracked by the control button of the motor drive (MD), but the worm is turned by hand in the declination direction. Therefore, it was difficult to make subtle movements, and for this reason an accessory was needed to reduce the rotation of the worm by about 1/10.


Edited by PawPaw, 20 August 2020 - 04:54 PM.

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#24 Dave Trott

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Posted 20 August 2020 - 10:32 PM

Don,

 

Thanks for the link. The autobiographical blog of Suzu is fascinating reading for any fan of GOTO Kogaku. And thanks for bringing this significant piece of equipment to our attention!

 

- Dave


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#25 PawPaw

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Posted 22 August 2020 - 08:36 AM

Dave....Thanks I find the Japanese engineering fascinating.   I have one more note on the mount before moving on to the OTA.

 

Yesterday evening I setup to use both the 80mm / Mark-x and my 60mm / ST6.  The only reason I decided to use both was I just completed collimating the ST-6 after much struggle and they are both the color Blue.   I don't think this is a coincidence.  I share this so you can see the evolution in GOTO's color scheme.  While the ST-6 mount is not hammertone it is very close to the same shade of Blue.  I cannot date the ST-6 exactly but the color points to the same timeframe.

 

The MX-28 worked flawless last night on Jupiter, Saturn and some DSO's.  Both RA and Dec motors are so quiet I have to put my ear to them to confirm working.  OK so I can't hear so well, Huh?  but they are quiet even to the touch and introduce no vibration that affects the image.  I did level the mount and used the polar scope for alignment....I tracked Jupiter for over 60 min last night with no adjustment needed after dialed in.  

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Edited by PawPaw, 22 August 2020 - 08:47 AM.

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