31 replies to this topic

[rmorein]

Setting aside ease of use, and the ability of modern mounts to compensate somewhat for mechanical imprecision, has anyone made basic comparisons between older premium mounts and modern, low cost in these metrics?

 

RA backlash

cyclic error

rms error

cone error

any other errors that should be part of this list?

 

Ease of use is not part of the question, because goto is a modern phenomena.

 

As an example, Explore Scientific offers a $500 goto mount based on stepper motors with decent looking gears, and reviews that are all over the place. So let's assume samples that are neither near-rejects or the rare pearls.

 

The classic competition was made by a Japanese cottage craftsman who spent many hours hand grinding a spur/worm to what was then considered a  highly precise result -- though, notably,  actual specifications from that era may have never been published.

Edited by rmorein, 25 January 2025 - 12:23 PM.

[starman876]

Setting aside ease of use, and the ability of modern mounts to compensate somewhat for mechanical imprecision, has anyone made basic comparisons between older premium mounts and modern, low cost in these metrics?

 

RA backlash

cyclic error

rms error

cone error

any other errors that should be part of this list?

 

Ease of use is not part of the question, because goto is a modern phenomena.

 

As an example, Explore Scientific offers a $500 goto mount based on stepper motors with decent looking gears, and reviews that are all over the place. So let's assume samples that are neither near-rejects or the rare pearls.

 

The classic competition was made by a Japanese cottage craftsman who spent many hours hand grinding a spur/worm to what was then considered a  highly precise result -- though, notably,  actual specifications from that era may have never been published.

Unitron equatorial mounts had an adjustment for taking  up slop in the gear train.   Something you do not see hardly at all on mounts these days or even back then.

[Astrojensen]

Unitron equatorial mounts had an adjustment for taking  up slop in the gear train.   Something you do not see hardly at all on mounts these days or even back then.

What? I don't think I've ever seen an equatorial mount that didn't have adjustments to remove slop in the drives, including the cheaply made Chinese ones, like EQ-1 to 6, etc. 

 

It may not always be immediately obvious, and sometimes it's not so easy to work with or require special tools, but it's been there, when I've looked for it. 

 

 

Clear skies!

Thomas, Denmark

Edited by Astrojensen, 25 January 2025 - 12:41 PM.

[hyiger]

I would think electronics/software and ultimately guiding that didn't exist 30 years ago compensate for less than precise mechanical tolerances and other sources of error in modern mounts which lowers the manufacturing costs. Of course for visual use none of this really matters. 

Edited by hyiger, 25 January 2025 - 12:44 PM.

[deSitter]

Setting aside ease of use, and the ability of modern mounts to compensate somewhat for mechanical imprecision, has anyone made basic comparisons between older premium mounts and modern, low cost in these metrics?

 

RA backlash

cyclic error

rms error

cone error

any other errors that should be part of this list?

 

Ease of use is not part of the question, because goto is a modern phenomena.

 

As an example, Explore Scientific offers a $500 goto mount based on stepper motors with decent looking gears, and reviews that are all over the place. So let's assume samples that are neither near-rejects or the rare pearls.

 

The classic competition was made by a Japanese cottage craftsman who spent many hours hand grinding a spur/worm to what was then considered a  highly precise result -- though, notably,  actual specifications from that era may have never been published.

Must distinguish between shaft-based mounts and drum-based mounts. Something like the DEC fork mount of the Sears 6335 and later refractors was a hybrid, which had a drum-based RA mechanism but a shaft-based DEC mechanism. Modern mounts are usually drum-based. Then it comes down to accuracy of the drum - it must be absolutely round to a very high tolerance to control backlash. Modern machining to the rescue - I have a copy of the Orion Astroview incarnation of the Synta EQ3-2 (modern equivalent - CG4) that has less backlash in both axes than any mount I own. The drums are perfect. So cheap need not be - cheap. (This one was free )

 

-drl

Edited by deSitter, 25 January 2025 - 01:31 PM.

[deSitter]

As for shaft-based mounts, my best one is from a AO Monolux 4380 - absolutely perfect in both axes and a wonderful joy to use.

 

-drl

[rmorein]

I've never seen a drum mount, and I can't find any explanatory pictures. These lack a worm reduction mechanism?

[CHASLX200]

U mounts were the only real good classic mounts i have had other than a freaky good 1.5" Edmund mount that was like silk. All Cave- and other mounts like them were never good.

[ccwemyss]

I had a CGEM DX for a while. My impression was that the backlash and cone error were comparable to or maybe a bit better than my AP 706, but not quite as good as the AP 600E, and definitely not at the level of the AP 900. But I never did a head-to-head comparison. 

 

Chip W. 

[CHASLX200]

I had a CGEM DX for a while. My impression was that the backlash and cone error were comparable to or maybe a bit better than my AP 706, but not quite as good as the AP 600E, and definitely not at the level of the AP 900. But I never did a head-to-head comparison. 

 

Chip W. 

My AP800 is also like silk to hand center planets at 450x and up.

[Astrojensen]

I've never seen a drum mount, and I can't find any explanatory pictures. These lack a worm reduction mechanism?

I'm not really sure what was meant, either. What is meant by a "drum" here? 

 

 

Clear skies!

Thomas, Denmark

[deSitter]

I've never seen a drum mount, and I can't find any explanatory pictures. These lack a worm reduction mechanism?

No - the main rotational element is a machined aluminum or brass drum with a azimuthal gear hogged into it. in better modern mounts, the drum rides on a race bearing but also must fit accurately into the cast aluminum housing. When you clamp the scope, a small plate presses on the drum and prevents it from rotating other than via the worm gear. To get the backlash under control. the hogging must be very uniform all the way around. This was a very great advance in mount design. To do it right is a matter of tight tolerances.

 

Part 1-11 in this exploded view of a Vixen SP. Same part used on both axes!

 

https://arnholm.org/...SP/Exploded.jpg

 

-drl

Edited by deSitter, 25 January 2025 - 05:27 PM.

[CHASLX200]

Opps my SP's and GP's are all good as well.

[deSitter]

I'm not really sure what was meant, either. What is meant by a "drum" here? 

 

 

Clear skies!

Thomas, Denmark

That explanation was a little short.

 

The scope and the drum can turn independently. You lock the drum to the other part of the axis when you clamp down. The worms operate against the drums which transfer it through the clamped part. it's pretty clear from that diagram for the SP.

 

The old DEC fork type mount had an inside out drum of brass, that is, a ring for RA. The clamp operated from the inside with an expanding brake ring, sort of like an old minibike centrifugal clutch, bore on the inner surface of the RA ring. When this works right it's fabulous but it is always famously hard to adjust the worm, which rides in eccentric bearings. You get this perfect in one place and then it's too tight 120 degrees later, because the hogging is inaccurate/eccentric. So it's always a compromise of how much is the least slop in use.

 

-drl

Edited by deSitter, 25 January 2025 - 05:41 PM.

[CharLakeAstro]

DEC backlash is more critical than RA backlash, if guiding. 

 

Setting aside ease of use, and the ability of modern mounts to compensate somewhat for mechanical imprecision, has anyone made basic comparisons between older premium mounts and modern, low cost in these metrics?

 

RA backlash

cyclic error

rms error

cone error

any other errors that should be part of this list?

 

 

[Bomber Bob]

So far, I've tested over a dozen Classic small scope EQ mounts:  GOTO [not go-to!], Kenko, Mizar, Questar, Takahashi, Unitron, Vixen, and Zeiss...

 

MOST STABLE (Manual Tracking):  Honest Tie between GOTO and Takahashi.  Big Caveat:  I have no idea how much abuse each mount suffered over the decades!

 

MOST RELIABLE MOTORIZED TRACKING:  Kenko NES EQ -- BUT that's not with the original Kenko drive(s).  Haven't found that (yet).  It's compatible with the Celestron CG-5 dual-axis drives, and is soooooo easy to use, and stays on target for 30+ minutes without corrections.  Original System:  Mizar AR or SP EQ with the MMD-III single-axis system, which runs for Hours on 4 x AA batteries.  * Honorable Mention:  Takahashi Sky Cancer ultra-light EQ w/ s-a drive, mainly because this mount can be slapped on any tripod with a standard 1/4-20 bolt head.

[deSitter]

DEC backlash is more critical than RA backlash, if guiding. 

This is an interesting observation. The system of coordinates has a singularity - the celestial pole - that complicates matters the closer you are to it.

 

-drl

[CharLakeAstro]

Backlash is primarily an issue when an axis reverses direction.

 

For guiding, RA backlash is less of an issue... because when Sidereal tracking, during a small negative guiding correction, the RA axis is still advancing forward but just slower. A larger negative correction could stop the RA axis. A positive guiding correction simply speeds up the RA axis faster than Sidereal rate. But in none of these cases does the RA axis reverse it's direction, making a small amount of RA backlash less critical than DEC backlash.

 

The DEC axis on an equatorial, is normally stopped. A positive guiding correction followed by a negative guiding correction, or vice-versa, results in DEC axis reversal, and this makes minimal DEC backlash more critical than minimal RA backlash.

 

This is an interesting observation. The system of coordinates has a singularity - the celestial pole - that complicates matters the closer you are to it.

 

-drl

[Astrojensen]

No - the main rotational element is a machined aluminum or brass drum with a azimuthal gear hogged into it. in better modern mounts, the drum rides on a race bearing but also must fit accurately into the cast aluminum housing. When you clamp the scope, a small plate presses on the drum and prevents it from rotating other than via the worm gear. To get the backlash under control. the hogging must be very uniform all the way around. This was a very great advance in mount design. To do it right is a matter of tight tolerances.

 

Part 1-11 in this exploded view of a Vixen SP. Same part used on both axes!

 

https://arnholm.org/...SP/Exploded.jpg

 

-drl

Okay, where to start... 

 

First, the gear type in question is called a helical worm gear, not an azimuthal gear. https://www.iqsdirec...ical-gears.html

 

Second, what you call a "drum" is nothing more than the RA worm gear shrunk down to its absolute minimum size. The mechanical principle in the construction, namely a shaft or axle, running in the RA housing, with the DEC housing solidly attached to the axle, and the RA worm wheel spinning freely around it, until braked down or locked to the DEC housing with a knob or lever on the DEC housing, is well over a century old. It has been in use at least since the 1880'ies, possibly much earlier. Repsold used it, as did Cooke, Zeiss, Steinheil and Heyde. I've personally used a Zeiss mount from 1904 that had this design. Mechanically, it's in principle and functionality 100% identical to the RA drive on a Vixen SP mount. Countless mounts have used this mechanical principle. The only thing that differs is the size ratio between components and the method with which the RA worm wheel is clutched to the DEC housing.  

 

Third, the precision with which the parts must be made is not unique to the "drum" design, but is shared by all worm wheel driven EQ mounts. And it's not more difficult to make the "drum", either. In fact, its very compact shape, relative to its diameter, makes it very stiff, and thus much easier to machine quickly to very high tolerances. It can also very easily be machined from automatically feed stock of modest size, in a modestly sized CNC 5-axis lathe/mill, unlike larger RA drives that often must be made one at a time. It's a design that lends itself very well to mass production at low cost. Especially if, like in the Vixen SP and GP series, you use many identical parts on both the RA and DEC axes. 

 

The really revolutionary part of the "drum" design was how compact it was made, not the mechanical principle (but I am not saying it isn't a piece of very clever engineering!). A lot of very handy features were combined into one neat and compact little package. The integrated polar scope was arguably by far the biggest revolution. The earliest mount that I can find, that I definitely know has a polar scope, is the mount for the Takahashi TS-65P from 1972. By 1980, basically every manufacturer in Japan have one or several compact ("drum") mounts with built-in polar scopes.    

 

 

Clear skies!

Thomas, Denmark

[rmorein]

But all things equal, the smaller the gear, the fewer teeth, the lower the reduction ratio --> less precision.

 

What do Astro-Physics, Paramount, and Losmandy use?

Edited by rmorein, 26 January 2025 - 01:10 PM.

[CHASLX200]

But all things equal, the smaller the gear, the fewer teeth, the lower the reduction ratio --> less precision.

 

What do Astro-Physics, Paradigm, and Losmandy use?

No clue. But AP knows how to make a mount no others can do.

[deSitter]

Okay, where to start... 

 

First, the gear type in question is called a helical worm gear, not an azimuthal gear. https://www.iqsdirec...ical-gears.html

 

Second, what you call a "drum" is nothing more than the RA worm gear shrunk down to its absolute minimum size. The mechanical principle in the construction, namely a shaft or axle, running in the RA housing, with the DEC housing solidly attached to the axle, and the RA worm wheel spinning freely around it, until braked down or locked to the DEC housing with a knob or lever on the DEC housing, is well over a century old. It has been in use at least since the 1880'ies, possibly much earlier. Repsold used it, as did Cooke, Zeiss, Steinheil and Heyde. I've personally used a Zeiss mount from 1904 that had this design. Mechanically, it's in principle and functionality 100% identical to the RA drive on a Vixen SP mount. Countless mounts have used this mechanical principle. The only thing that differs is the size ratio between components and the method with which the RA worm wheel is clutched to the DEC housing.  

 

Third, the precision with which the parts must be made is not unique to the "drum" design, but is shared by all worm wheel driven EQ mounts. And it's not more difficult to make the "drum", either. In fact, its very compact shape, relative to its diameter, makes it very stiff, and thus much easier to machine quickly to very high tolerances. It can also very easily be machined from automatically feed stock of modest size, in a modestly sized CNC 5-axis lathe/mill, unlike larger RA drives that often must be made one at a time. It's a design that lends itself very well to mass production at low cost. Especially if, like in the Vixen SP and GP series, you use many identical parts on both the RA and DEC axes. 

 

The really revolutionary part of the "drum" design was how compact it was made, not the mechanical principle (but I am not saying it isn't a piece of very clever engineering!). A lot of very handy features were combined into one neat and compact little package. The integrated polar scope was arguably by far the biggest revolution. The earliest mount that I can find, that I definitely know has a polar scope, is the mount for the Takahashi TS-65P from 1972. By 1980, basically every manufacturer in Japan have one or several compact ("drum") mounts with built-in polar scopes.    

 

 

Clear skies!

Thomas, Denmark

Not really understanding this. The drum I am referring to is something like a car engine piston but instead of a piston ring it has a straight up/down, not helical, gear hogged into the cylindrical surface. The walls of the cylinder ride smoothly inside the cast aluminum housing and a worm block sits over it, attached to the external surface of the housing. The drum is part of the support for the entire axis, not just a passive component like an external gear riding on the end of a solid shaft. Because it is a structural element, it allows a compact head to support much more payload than a typical classic mount.

 

-drl

[elstargazer12]

Ah! This may be the thread I was meant to join to when I signed up to CN like 15 years ago . I've taken apart (and in every case so far reassembled!) lots of EQ mounts over the years... it's like a hobby within a hobby for me. These include in rough age order:

 

- Towa small (ie 60mm class) and large (80mm model 339) EQ mounts

- Not-sure-who-made-it-but-common other small japanese refractor mount (e.g. Mayflower 815)

- B&L 4000 SCT mount

- Takahashi EM-200, EM1-S early 90s, Tak Sky Patrol III, much newer

- Kenko EQ-1 (cute little Vixen Polaris class mount)

- Vixen Polaris, SP-DX, GP, and GP-DX

- ETX mounts, 90RA, 90EC, 125EC

- Meade 4500 reflector mount

- Celestron CG-5 (relatively early version)

 

Ok, I'll talk about these in a sec, but to answer the OP's original questions: I think the quality does not correlate much with time period, but it does correlate a lot with the maker and, of course, price. I'm not a pro machinist, but I'm been in a shop enough to know: basically manual machining can be really bad or really good, depending on the effort (and therefore $) put into it. CNC is consistent and cheaper in quantity, but can't typically hit the peaks of quality of a really well made manually machined part. For example if you turn something on a lathe manually, you can check with a micrometer before the final cut and non-pro like me can make a 1/2 thousandth inch tolerance part (0.0005" or about 13 µm). This takes a lot of time of course and most makers don't do this. CNC has lots of moving parts and, if automated to produce in quantity, can't match those tolerances, but it can economically hit an acceptable threshold.

 

So bottom line, older manufacturing can put out high tolerance stuff that meets or beats anything modern, but modern CNC produced mounts are probably more consistent and better than the cheap older stuff. There are cheap and trashy new stuff too of course, but that's another tier below the ES mount example the OP mentioned. 

 

Ok, now to rank these mounts into five tiers:

 

Tier 1 (OMG I can't believe the maker bothered to do this and I feel a little guilty I paid so little for it)

- ALL of the Taks, EM1, EM200, Sky Patrol. Oh man... they don't play with tolerances here. Sliding a bearing off of a shaft is HARD. If it's slightly tilted, it gets stuck. You have to be so careful. It feels like a 0.001" or 0.002" tolerance part at worst. Definitely tighter than the typical 0.005" from CNC and more usual machining. The other really interesting thing is that ALL THE TAKS, REGARDLESS OF PRICE, ARE LIKE THIS. The Sky Patrol has the same insane tolerances around the axles as the EM200. Wow! When playing with these mounts, I honestly find myself worrying for Takahashi... like is this good business?? Dear Mr. Takahashi, I'm sure people will buy your mounts if you had slightly worse tolerance... are you making money? (joking of course... they've been in business for forever, so obviously don't need business advice from me)

 

Tier 2 (Works well! In practice not far from Tier 1)

- The bigger Vixens, SP-DX, GP, GP-DX. This is an interesting one since I have experience with a range of ages here. With the caveat I don't know about sample-sample variations, I would say NEWER VIXENS ARE A BIT BETTER THAN THE OLDEST. The most interesting comparison is the SP-DX (probably ~1990 or late 80s?) vs. the newer GP-DX (Mine is quite modern, white paint, post 2010). These are designed to be in the same weight and price class. First, the GP-DX uses ball bearings instead of bushings as the SP-DX. There's nothing inherently wrong with well-made bushings, but it's easier to hit a certain tolerance with ball bearings since you just need to machine a decent mating surface and the bearing maker can guarantee the rest. Second, I found it easier with the GP-DX to adjust the worm such that it minimizes backlash without making it too stiff to turn. I'm not sure if these is because they used a slightly higher precision for the gear set or something else. 

 

Tier 3 (Works fine, significant backlash, OK for manual use)

- The Kenko EQ-1. Maybe little surprising given their reputation on par with Vixen. Worm meshing was just OK, axles not well-fitting

- The Vixen Polaris. Significant slop around the axles. But of course, it's by far the cheapest of the Vixens, so it makes sense (although Takahashi is an exception see above).

 

Tier 4 (still usable, but clearly poorly made)

- Early CG-5: Terrible tolerances around the axles so that it wobbles even when locked down. Stability is passable just from the weight of the thing.

- Meade 4500 mount

- ETX 90 and 125 EC mounts. a little hard to compare since it's motorized, but I found these good enough. 

- B&L 4000 mount. People say good things about this online, but, other than made with metal, I don't see how this is any better than the later ETX EC mounts. Puts ALL the torque on a tiny pair of axle ball bearings and wobbles a lot as a consequence.

- The old Towa mounts. Tolerances are pretty terrible and things somehow have a way of coming loose. 4-

 

Tier 5 (Ugh... who designed this? UNUSABLE! I find myself wondering if they forgot a part somewhere... you can see light through some of the axle tolerances!)

- Mayflower 814 style old EQ mount. Even with a lot of adjusting, can't get it to stop flexing

- ETX 90RA mount. Lots of backlash... well documented online

 

 

Interesting pattern here: Tier 1 and 2 consistent of mounts of all ages from two makers, while the dead bottom consists of a lot of very old mounts. 

 

 

 

 

 

 

 

[elstargazer12]

As if my last post wasn't long enough, here is something interesting I've noticed disassembling all these mounts... It's a good way to distinguish a mount built by a craftman proud of his/her work versus one that's meant to be "good enough for the price". 

 

In other words, it's an easy place to cut corners, and mount makers do it. 

 

See sketch... simplified mount highlighting just the RA axis. A and B are axle bearings (ball or bushings). C and D are contacts between the RA mount housing and the axle. These are under compression parallel to the axis direction, enforced by nut E. Now, if you're Takahashi, you just machine all the key surfaces at extreme tolerance (0.001" level), including the interface between the axle and bearings A and B. i.e., even if you loosen nut E completely, the mount becomes loose, but the motion is still smooth and there's no slop. 

 

In contrast, MOST manufacturers do NOT machine these bearing A and B interfaces to the highest tolerance. Instead, they rely on tightening nut E VERY TIGHT, so that the pressure on thrust surfaces C and D are preventing wobbling of the axle, to a large extent. This is a lot cheaper to do, and everything in Tiers 2-5 in my last post do this to some extent. In fact, the early Chinese CG-5 and the old Towa/Mayflower mounts don't really bother mating the axles with bearings A and B AT ALL. You can literally slide a paper clip between the axle and the bearing. Instead, you have to tightening down the end nut E, which makes the mount less smooth, very sensitive to small adjustments, and results in more backlash in the worm gear because the axle is able to shift in the perpendicular-to-axle direction. 

 

 

 

 

Attached Thumbnails

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[CHASLX200]

Ah! This may be the thread I was meant to join to when I signed up to CN like 15 years ago . I've taken apart (and in every case so far reassembled!) lots of EQ mounts over the years... it's like a hobby within a hobby for me. These include in rough age order:

 

- Towa small (ie 60mm class) and large (80mm model 339) EQ mounts

- Not-sure-who-made-it-but-common other small japanese refractor mount (e.g. Mayflower 815)

- B&L 4000 SCT mount

- Takahashi EM-200, EM1-S early 90s, Tak Sky Patrol III, much newer

- Kenko EQ-1 (cute little Vixen Polaris class mount)

- Vixen Polaris, SP-DX, GP, and GP-DX

- ETX mounts, 90RA, 90EC, 125EC

- Meade 4500 reflector mount

- Celestron CG-5 (relatively early version)

 

Ok, I'll talk about these in a sec, but to answer the OP's original questions: I think the quality does not correlate much with time period, but it does correlate a lot with the maker and, of course, price. I'm not a pro machinist, but I'm been in a shop enough to know: basically manual machining can be really bad or really good, depending on the effort (and therefore $) put into it. CNC is consistent and cheaper in quantity, but can't typically hit the peaks of quality of a really well made manually machined part. For example if you turn something on a lathe manually, you can check with a micrometer before the final cut and non-pro like me can make a 1/2 thousandth inch tolerance part (0.0005" or about 13 µm). This takes a lot of time of course and most makers don't do this. CNC has lots of moving parts and, if automated to produce in quantity, can't match those tolerances, but it can economically hit an acceptable threshold.

 

So bottom line, older manufacturing can put out high tolerance stuff that meets or beats anything modern, but modern CNC produced mounts are probably more consistent and better than the cheap older stuff. There are cheap and trashy new stuff too of course, but that's another tier below the ES mount example the OP mentioned. 

 

Ok, now to rank these mounts into five tiers:

 

Tier 1 (OMG I can't believe the maker bothered to do this and I feel a little guilty I paid so little for it)

- ALL of the Taks, EM1, EM200, Sky Patrol. Oh man... they don't play with tolerances here. Sliding a bearing off of a shaft is HARD. If it's slightly tilted, it gets stuck. You have to be so careful. It feels like a 0.001" or 0.002" tolerance part at worst. Definitely tighter than the typical 0.005" from CNC and more usual machining. The other really interesting thing is that ALL THE TAKS, REGARDLESS OF PRICE, ARE LIKE THIS. The Sky Patrol has the same insane tolerances around the axles as the EM200. Wow! When playing with these mounts, I honestly find myself worrying for Takahashi... like is this good business?? Dear Mr. Takahashi, I'm sure people will buy your mounts if you had slightly worse tolerance... are you making money? (joking of course... they've been in business for forever, so obviously don't need business advice from me)

 

Tier 2 (Works well! In practice not far from Tier 1)

- The bigger Vixens, SP-DX, GP, GP-DX. This is an interesting one since I have experience with a range of ages here. With the caveat I don't know about sample-sample variations, I would say NEWER VIXENS ARE A BIT BETTER THAN THE OLDEST. The most interesting comparison is the SP-DX (probably ~1990 or late 80s?) vs. the newer GP-DX (Mine is quite modern, white paint, post 2010). These are designed to be in the same weight and price class. First, the GP-DX uses ball bearings instead of bushings as the SP-DX. There's nothing inherently wrong with well-made bushings, but it's easier to hit a certain tolerance with ball bearings since you just need to machine a decent mating surface and the bearing maker can guarantee the rest. Second, I found it easier with the GP-DX to adjust the worm such that it minimizes backlash without making it too stiff to turn. I'm not sure if these is because they used a slightly higher precision for the gear set or something else. 

 

Tier 3 (Works fine, significant backlash, OK for manual use)

- The Kenko EQ-1. Maybe little surprising given their reputation on par with Vixen. Worm meshing was just OK, axles not well-fitting

- The Vixen Polaris. Significant slop around the axles. But of course, it's by far the cheapest of the Vixens, so it makes sense (although Takahashi is an exception see above).

 

Tier 4 (still usable, but clearly poorly made)

- Early CG-5: Terrible tolerances around the axles so that it wobbles even when locked down. Stability is passable just from the weight of the thing.

- Meade 4500 mount

- ETX 90 and 125 EC mounts. a little hard to compare since it's motorized, but I found these good enough. 

- B&L 4000 mount. People say good things about this online, but, other than made with metal, I don't see how this is any better than the later ETX EC mounts. Puts ALL the torque on a tiny pair of axle ball bearings and wobbles a lot as a consequence.

- The old Towa mounts. Tolerances are pretty terrible and things somehow have a way of coming loose. 4-

 

Tier 5 (Ugh... who designed this? UNUSABLE! I find myself wondering if they forgot a part somewhere... you can see light through some of the axle tolerances!)

- Mayflower 814 style old EQ mount. Even with a lot of adjusting, can't get it to stop flexing

- ETX 90RA mount. Lots of backlash... well documented online

 

 

Interesting pattern here: Tier 1 and 2 consistent of mounts of all ages from two makers, while the dead bottom consists of a lot of very old mounts. 

I would rate all the old school 1.5" shaft mounts as tire 6.  Worst that can be made with jerky and sticky clutches and vibes and jitters that shake and flex at every turn. I had the very first CG4 AND 5 in 1997 and what a huge step down from the Vixen mounts. Tier 7.

Edited by CHASLX200, 26 January 2025 - 03:07 PM.