Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

CRUX Mount Harmonic Drive Equatorial Mount

  • Please log in to reply
89 replies to this topic

#26 contedracula

contedracula

    Messenger

  • -----
  • topic starter
  • Posts: 478
  • Joined: 11 Oct 2011
  • Loc: USA - Italy

Posted 24 February 2017 - 03:39 PM

But these are just guesses we do there is no trace of detailed explanations.

I realize that the excitement of a new product for all of us can bring a great optimism, but when the cost is important I demand an equally important service

 

The only thing I see is a trace with Maxim DL

Ok I expressed myself badly, there isn't periodic error because are direct drive sure, then what is the tracking error?
ASA declares 0,68” peak to peak 1 hour
CRUX declares 17" PtP how many time?????


  • opusone likes this

#27 nmoushon

nmoushon

    Surveyor 1

  • *****
  • Moderators
  • Posts: 1,533
  • Joined: 12 Oct 2011
  • Loc: Wenatchee Valley, WA

Posted 24 February 2017 - 03:56 PM

But these are just guesses we do there is no trace of detailed explanations.

I realize that the excitement of a new product for all of us can bring a great optimism, but when the cost is important I demand an equally important service

 

The only thing I see is a trace with Maxim DL

Ok I expressed myself badly, there isn't periodic error because are direct drive sure, then what is the tracking error?
ASA declares 0,68” peak to peak 1 hour
CRUX declares 17" PtP how many time?????

I want trying to get you to buy it without getting the info. I emailed the person asking for more info. I will PM you his email if you want to ask more specific questions. 

All I was trying to get at was the equipment here is high end so no need to keep the same amount of skepticism as the new CGX has gotten. Like trying to apply the "one half rule" here. But by all mean ask questions and get answers. I would want them if I was dropping $10k on something.



#28 contedracula

contedracula

    Messenger

  • -----
  • topic starter
  • Posts: 478
  • Joined: 11 Oct 2011
  • Loc: USA - Italy

Posted 24 February 2017 - 04:15 PM

ok I got it!  ;)

 

I try to get more info from them 

I'll keep you posted

 

CIAO!


  • nmoushon likes this

#29 orlyandico

orlyandico

    Cosmos

  • *****
  • Posts: 9,783
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 24 February 2017 - 06:50 PM

you don't need to read "oriental" to figure out the specs from that link. i don't read "oriental" myself.

#30 contedracula

contedracula

    Messenger

  • -----
  • topic starter
  • Posts: 478
  • Joined: 11 Oct 2011
  • Loc: USA - Italy

Posted 25 February 2017 - 03:00 AM

I've read many words on mounts.
We discuss on this forum even about the smallest features. If today I were to buy a Crux for the information that are present on their website, I would never do.

 

Also I never give for a fact that a product is excellent I prefer to investigate before, I bought FOUR 10Micron and TWO AstroPhysics before to assert that are wonderful mounts

It is very clear that this company is a typical cross-company, does not live by these products, probably the core business is another and therefore do not need to take care of the marketing aspect and informations.

 

This is a major limitation of the Asian manufacturers, producers are very good but not good for selling.

 

I remember at NEAF of 2012 the Morning Calm Stand of Rainbow Astro
A Mount resting on a table turned off, little information, no examples of features.
Make a fair in this way is like to go at baptism without the baby  :shocked:

 

In fact the result after 5 years was very poor, few sales.
In Europe AstroShop made a discount of 50% off order to sell these mount! I repeat 50% not 10% !!!

Unfortunately I never seen a discount for AP, 10Micron, ASA, Avalon, Losmandy, Takahashi but just for Asian Mounts Celestron, Ioptron, Skywatcher etc. etc. there must be a reason  :waytogo:

 

CIAO!

 

 



#31 tolgagumus

tolgagumus

    Vendor

  • *****
  • Vendors
  • Posts: 3,690
  • Joined: 21 Jul 2014
  • Loc: NJ

Posted 26 February 2017 - 04:52 PM

The Crux sure looks interesting (and strange).

Memo to Tolga: "Bring them in." wink.gif

Thanks for the heads up. I went to their website and checked it out. I'll try to contact them to see if they are willing to work with me but I would doubt if they would send me a mount to test first. For me to carry a product I need to have some sort of first hand experience with it. 


  • CounterWeight, nmoushon and ChrisMoses like this

#32 orlyandico

orlyandico

    Cosmos

  • *****
  • Posts: 9,783
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 26 February 2017 - 08:08 PM

Incidentally the outfit making these mounts also has several MorningCalm mounts on his page. Maybe it's the return of MorningCalm?



#33 CounterWeight

CounterWeight

    Star walker

  • *****
  • Posts: 11,117
  • Joined: 05 Oct 2008
  • Loc: PDX, OR.

Posted 26 February 2017 - 08:10 PM

One thing to add about spec's.  My opinion is that spec's are only that, it is more important what the typical performance is over a period of time.  After many years in high tech and spec's, I came to think of them as 'in general expect this'.  Tracking error?  on what? everywhere?  Toward horizon or near zenith?  How is the tracking measured? centroid? edge?  What type of telescope used?  Long f/l or short f/l...  doublet? triplet, quad? CDK?  RC?  Was it pier mounted or on a tripod? Where was it done and under what type skies? I can ask a thousand questions about any spec.  Not to make them meaningless, but just to show that is all it is.

 

Another part of me always avoids initial release products of any complexity, only because I see it as a difficult task to anticipate everything.  Not because folks can't get it right the first time, some do.

 

Another issue is language barrier.  Going between some languages it is far larger and more difficult than others, and in the technical world more difficult again if the translator is not adept in the subject.

 

Give it some time, I'm sure things will iron out.



#34 orlyandico

orlyandico

    Cosmos

  • *****
  • Posts: 9,783
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 26 February 2017 - 08:58 PM

Well the magic of the CRUX is the harmonic drive.

 

I think the longevity of harmonic drives has been well-established in harsh environments, since those Mars rovers tooling about the red planet have harmonic drives turning their wheels.

 

And because there's only one company making harmonic drives (Harmonic Drive Systems) the quality and accuracy of these drives is a known quantity.

 

In the case of this CRUX, it's a normal stepper motor driving the harmonic drive, so in theory you could ditch whatever controller they are packaging, and use your own stepper motor controller (like the StarGo, or even OnStep).



#35 Yun-Oh

Yun-Oh

    Vostok 1

  • *****
  • Posts: 197
  • Joined: 14 Jan 2012
  • Loc: Gibsonia, PA (Greater Pittsburgh)

Posted 27 February 2017 - 01:35 AM

Here is what I know about Crux mounts.  I have to disclose that I'm not a impartial observer as I will explain a little later.  However, I will try my best to present some facts that would be helpful for people to understand a little bit of history behind Crux.

 

Several years ago, a Korean company called AstroDream Tech introduced high end eq mounts under the brand Morning Calm.  They were featured at NEAF 2012, and I was the one who manned the booth.  The owner (Injoon Hwang) of AstroDream Tech was an old friend of mine and I was asked to represent the company in North America and set up the distribution network.  A few retailers ended up signing a dealer contract, and things started to roll.

 

There were a few MorningCalm mounts shipped to the dealers and after testing them, the tracking accuracy turned out to be way worse than expected.  It was a surprise for all of us including myself.  The dealers, the people in Korea, and I started working together to resolve the issue.  In the mean time, Hwang started a discussion in Korea to sell his company (AstroDream Tech).  The sale was finalized shortly after, and the the company that bought out AstroDream Tech set up a new company called Rainbow Astro.  After the merger, Hwang and the new ownership got into a nasty dispute, and Hwang ended up leaving the company shortly after the merger.  The Morning Clam line has since been dropped and I was relieved of my role as the distributor.  Rainbow Astro soon started promoting its own new design, which is now distributed by Astrofactors with a model number RST-400.

 

In all these changes, the dealers who signed up and took inventory of Morning Calm mounts ended up taking a huge loss.  Rainbow Astro assured the dealers that they would honor the dealer contracts, but there was no more communication afterwards.  As the one who recruited the dealers, I felt responsible and tried to convince Hwang and RainbowAstro to at least compensate for the losses by the dealers, but never received any answer.

 

Now there is this new mount brand called Crux, which is Hwang's product.  Hwang is promoting it out of his personal observatory web site (Hobym Observatory) and also a few Japanese web sites.  I guess he is trying to make a comeback to the mount business.

 

I haven't talked to him since his departure from Rainbow Astro, so have no more information on the mount other than what I see on his web site.  But, since many people started to speculate where the mount is from, I feel that I should share the information on the history of the producer (especially when contedracula and orly mentioned Morning Calm smirk.gif).

 

Anyone who is interested in more information on the history, feel free to PM me.  You can also contact me if you want translation of the Korean literature on Crux mounts.

 

I'm now completely out of astro related business, and enjoying being an amateur again.  Love to be a buyer rather than a seller. wink.gif


Edited by Yun-Oh, 27 February 2017 - 01:36 AM.

  • Ricky, Moravianus, lambermo and 7 others like this

#36 jsuh69

jsuh69

    Lift Off

  • -----
  • Posts: 2
  • Joined: 16 Apr 2015
  • Loc: Seoul, Korea

Posted 13 March 2017 - 08:27 AM

I'm an owner of Crux 170HD in Korea and one of friends of In-Joon Hwang who mentioned by Yun-Oh Whang.

 

This is another story of Crux 170HD.

 

My previous mount was Takahashi EM200 temma PC. It became so heavy to me after getting ages because I have no observatory yet. smile.gif When I visited his observatory last year, I saw that he was making new mount for his own portable mount to go to Chile Atacama Desert without business purpose. (http://www.hobym.net/astro-tour) I was so surprised payload of new mount at that time.

 

So, Crux 170HD is very special mount for astrophoto (no backlash) and overseas mobility. It's only 5kg weight and Max 16kg payload. After his tour of Chile Atacama, many his korean & japanese friends encouraged making new harmonic gear mount for themselves.

 

This is real story of new small harmonic mount not a business purpose mount at first.

 

Regarding to his past business, I think that there are many points of view.

 

He sold his company to his partner (http://www.rainbow-robotics.com/), who is a famous robotics Prof. Oh in Korea and U.S., and left company regardless of any reason, merger company inherited business responsibility. It's normal as my business experience. I don't understand why he is blamed by ex-business partner at here. 

 

He is making mount by himself without any employee, so he can't make many mounts simultaneously and Crux 170HD is "ONLY" for astrophotographer and anyone who want maximum mobility.

 

It's not a general purpose mount for public because it's expensive rather than another commercial mount made by chinese factory. If you have any question about Crux 170HD, feel free asking to me. I will explain about pro and cons about Crux 170HD.

 

I hope that my post helping about Crux 170HD and his history.

 

Clear Skies!!!

No more chinese yellow sand storm to korea!!!


Edited by jsuh69, 14 March 2017 - 02:11 AM.

  • psandelle, nmoushon and starlit like this

#37 radial195

radial195

    Mariner 2

  • -----
  • Posts: 273
  • Joined: 31 Aug 2012
  • Loc: Kingman, Az.

Posted 10 December 2018 - 11:56 AM

I hope I might resurrect this thread with a "real life" story of a Crux mount. This past Saturday, Dec. 8, 2018 I attended a small gathering of astrophotographers at the Mataguay Scout Ranch in NE San Diego County, Ca. by Lake Henshaw. One of the attendees is the first purchaser of one of these mounts in the US. Crux makes 4 sizes of mount; light, med. light, medium, and heavy. His is the med light, 40# payload with counterweights. He had a Stellarvue SVQ100 on it along with a QHY full frame OSC camera, a guider, and a finder scope. After polar aligning he started taking subs while guiding with PHD2. He was having trouble with the mount jumping around while guiding. It was decided to turn off PHD2 and see how the mount behaved with no guiding. It immediately settled down and started tracking perfectly. He took 21 subs of 10 minutes each of the Rosette. Each frame was absolutely perfect- - -tight stars, each registered perfectly to the one prior or after, NO wasted shots. I was amazed at the perfection of the unguided tracking, the silence of the mount when slewing, and just how well executed the entire mount was! Now, I want one!


  • CounterWeight and nmoushon like this

#38 nmoushon

nmoushon

    Surveyor 1

  • *****
  • Moderators
  • Posts: 1,533
  • Joined: 12 Oct 2011
  • Loc: Wenatchee Valley, WA

Posted 17 December 2018 - 01:14 PM

I hope I might resurrect this thread with a "real life" story of a Crux mount. This past Saturday, Dec. 8, 2018 I attended a small gathering of astrophotographers at the Mataguay Scout Ranch in NE San Diego County, Ca. by Lake Henshaw. One of the attendees is the first purchaser of one of these mounts in the US. Crux makes 4 sizes of mount; light, med. light, medium, and heavy. His is the med light, 40# payload with counterweights. He had a Stellarvue SVQ100 on it along with a QHY full frame OSC camera, a guider, and a finder scope. After polar aligning he started taking subs while guiding with PHD2. He was having trouble with the mount jumping around while guiding. It was decided to turn off PHD2 and see how the mount behaved with no guiding. It immediately settled down and started tracking perfectly. He took 21 subs of 10 minutes each of the Rosette. Each frame was absolutely perfect- - -tight stars, each registered perfectly to the one prior or after, NO wasted shots. I was amazed at the perfection of the unguided tracking, the silence of the mount when slewing, and just how well executed the entire mount was! Now, I want one!

Thanks for sharing. 

Even with a harmonic drive mount I would want it to be able to guide. Maybe it just didnt like PHD2, who knows. I would've expected longer subs with that small of a scope on it. Do you know if he tried longer subs? If 10min unguided is the max then there are currently options that can do that with that scope that cost less. 



#39 radial195

radial195

    Mariner 2

  • -----
  • Posts: 273
  • Joined: 31 Aug 2012
  • Loc: Kingman, Az.

Posted 17 December 2018 - 06:50 PM

To my knowledge the owner selected the length of his exposure time to give himself an optimal histogram spread. I don't know if he tried longer exposures, but see no reason the mount would have faltered with longer exposures.

 

As far as the mount not liking PHD2, I suppose that's possible. This was the owners "first light" with this system, so maybe if he spends some time tinkering with PHD2's controls he can achieve steady guiding. If t'was me, I'd first play with unguided exposures and see how long I could go, and how many subs I could take before things started to drift.


  • nmoushon likes this

#40 nmoushon

nmoushon

    Surveyor 1

  • *****
  • Moderators
  • Posts: 1,533
  • Joined: 12 Oct 2011
  • Loc: Wenatchee Valley, WA

Posted 17 December 2018 - 07:33 PM

To my knowledge the owner selected the length of his exposure time to give himself an optimal histogram spread. I don't know if he tried longer exposures, but see no reason the mount would have faltered with longer exposures.

 

As far as the mount not liking PHD2, I suppose that's possible. This was the owners "first light" with this system, so maybe if he spends some time tinkering with PHD2's controls he can achieve steady guiding. If t'was me, I'd first play with unguided exposures and see how long I could go, and how many subs I could take before things started to drift.

Do you know if he is a member here? Would be very interested to follow him and his new toy. grin.gif 

 



#41 radial195

radial195

    Mariner 2

  • -----
  • Posts: 273
  • Joined: 31 Aug 2012
  • Loc: Kingman, Az.

Posted 18 December 2018 - 10:19 AM

I don't know if he is a member of CN, my guess is he's not. He seemed to be on the "private" side!

 

Back in the late 70's I lived in Wenatchee for a while, #2 Canyon, and then off Orondo St. Is the Orondo Tavern still open?


  • nmoushon likes this

#42 orlyandico

orlyandico

    Cosmos

  • *****
  • Posts: 9,783
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 18 December 2018 - 10:34 AM

Well in the other thread (Rainbow Astro RST-150H) one of the owners stated that the periodic error was 30" p-p.

 

A bit of a stretch, but I do know that the Rainbow Astro folks and the Crux folks were formerly affiliated. And they both are harmonic drive mounts.  The best harmonic drives are still made by Harmonic Drive Systems in Japan, so if we assume both mounts use HDS drives, then one could expect similar periodic error. Given the price points, I would expect that they are using HDS drives (a China-made harmonic drive is around $600 each, while a Japan-made HDS drive is about $1200 each).

 

In other words: you need to guide.


  • nmoushon likes this

#43 nmoushon

nmoushon

    Surveyor 1

  • *****
  • Moderators
  • Posts: 1,533
  • Joined: 12 Oct 2011
  • Loc: Wenatchee Valley, WA

Posted 18 December 2018 - 11:42 AM

I don't know if he is a member of CN, my guess is he's not. He seemed to be on the "private" side!

 

Back in the late 70's I lived in Wenatchee for a while, #2 Canyon, and then off Orondo St. Is the Orondo Tavern still open?

I dont believe so. I think that is now called McGlinns Pub. Its a great bar and restaurant. If you ever make it back here its a must stop place to eat. 



#44 nmoushon

nmoushon

    Surveyor 1

  • *****
  • Moderators
  • Posts: 1,533
  • Joined: 12 Oct 2011
  • Loc: Wenatchee Valley, WA

Posted 18 December 2018 - 11:44 AM

Well in the other thread (Rainbow Astro RST-150H) one of the owners stated that the periodic error was 30" p-p.

 

A bit of a stretch, but I do know that the Rainbow Astro folks and the Crux folks were formerly affiliated. And they both are harmonic drive mounts.  The best harmonic drives are still made by Harmonic Drive Systems in Japan, so if we assume both mounts use HDS drives, then one could expect similar periodic error. Given the price points, I would expect that they are using HDS drives (a China-made harmonic drive is around $600 each, while a Japan-made HDS drive is about $1200 each).

 

In other words: you need to guide.

30" p-p is not as good as I would've hoped with a HDS. Maybe its because they are using the "economical" versions that are scaled down? If I have to guide I would rather put that money towards a nicer camera and just stick with a normal mount. 



#45 orlyandico

orlyandico

    Cosmos

  • *****
  • Posts: 9,783
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 18 December 2018 - 02:23 PM

The owner/representative in the other thread said that the value prop of the RST-150H is the compactness and not needing counterweights. Not low periodic error.

 

Harmonic drives are zero backlash devices. I don't think low periodic error was ever part of their design goals.


  • EFT and nmoushon like this

#46 OzAndrewJ

OzAndrewJ

    Skylab

  • *****
  • Posts: 4,092
  • Joined: 30 Nov 2010

Posted 18 December 2018 - 02:52 PM

Gday Orly

Harmonic drives are zero backlash devices. I don't think low periodic error was ever part of their design goals.

I looked at the "mechanical" design of these drives many years ago when they were first mentioned, as i had never heard of them.

As you note, they are virtually backlash free, but still depend on two sets of mechanically cut gears, that are required to have precise spacing across the full 360degrees, each tooth needs to have exactly the same profile, and the inner gear needs to have a different toothcount to the outer gear, so the PCDs need to be exact as well.

This is a lot harder than making a perfect worm, that has low PE for one rev.

When you also look at the fact the drives are a much smaller dia than traditional hi accuracy worm wheels and then do the math, the precision needs to be microscopic, if you expect it to work "unguided" ( ie unassisted by either encoder or guider feedback ).

 

Andrew Johansen Melbourne Australia


Edited by OzAndrewJ, 18 December 2018 - 02:57 PM.


#47 nmoushon

nmoushon

    Surveyor 1

  • *****
  • Moderators
  • Posts: 1,533
  • Joined: 12 Oct 2011
  • Loc: Wenatchee Valley, WA

Posted 18 December 2018 - 03:56 PM

The owner/representative in the other thread said that the value prop of the RST-150H is the compactness and not needing counterweights. Not low periodic error.

 

Harmonic drives are zero backlash devices. I don't think low periodic error was ever part of their design goals.

Thats right. Its the zero backlash thats the draw not PE. I had those two mixed mixed up in my head. 

 

No counterweights is a plus for sure but if you do use them, like in the example radial195 mentioned, I dont see the draw. 



#48 orlyandico

orlyandico

    Cosmos

  • *****
  • Posts: 9,783
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 18 December 2018 - 08:41 PM

IMHO the combination of a harmonic drive and a relative encoder could achieve the necessary results. A harmonic drive almost cannot be "back driven" - which is why they don't need counterweights - and these mounts don't have a clutch - so you cannot move them outside of using the drive system, so technically you don't need an absolute encoder.

 

But now the cost escalates even more if you need to add a 5000 ppr encoder (or similar)



#49 OzAndrewJ

OzAndrewJ

    Skylab

  • *****
  • Posts: 4,092
  • Joined: 30 Nov 2010

Posted 18 December 2018 - 10:16 PM

Gday Orly

 

almost cannot be "back driven" - which is why they don't need counterweights

I always wondered there.

I never found any real details on the tooth forms used and how much friction vs rolling is involved as they transition.

Being smaller in dia than normal drives, and not necessarily having a true "rolling" fit between the teeth as they mate, it may result in extra wear over time as the tooth loadings may be quite high with no CWs.

Never saw any details on that though, so may not be a problem for normal use.

 

Andrew Johansen Melbourne Australia



#50 orlyandico

orlyandico

    Cosmos

  • *****
  • Posts: 9,783
  • Joined: 10 Aug 2009
  • Loc: Singapore

Posted 19 December 2018 - 01:20 AM

The difference is that most (at least half) the teeth are engaged at any given time, whereas with a worm drive at best only a handful of teeth are engaged between the worm and the wheel.

Wear and tear yes. I have several of these drives from ebay that I got cheap but obviously were scrapped because they no longer met their original design parameters. But they still look fine and don’t have obvious wear.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics