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Ovision or Losmandy?

 

The moment has come to update my G11?s autoguide. I want to chance the RA (and DEC, perhaphs) worm to achieve a better autoguide. But, my doubt is choose the Ovision option or Losmandy option. Anyone can bring any light about this theme? Thank you.
 

Hi nmatxin,

If you already have the brass worm gears installed in your mount you already have high precision worms installed and I highly recommend buying the newly redesigned Losmandy one piece worm block for BOTH RA and DEC axes.?If your mount has the old silver colored standard precision worms then I suggest buying the new Losmandy OPW with a new high precision worm installed and install it on the RA axis and an additional new Losmandy OPW for the DEC axis using your existing worm gear. This configuration will get your tracking PE way down and save you $100 over buying a new pair of HP worm OPWs. If money is not an issue bring your G11 up to the current standard with a pair of HP worm loaded OPWs.?

My thinking is this: the first generation Losmandy OPW may have had slightly higher potential to reduce periodic errors because the old OPW fully aligned the gearbox and worm gears on the same axis to eliminate the very small velocity differences inherent when an Oldham coupler is misaligned, this is inherent to the Oldham coupler design. The potential error improvement was very small but cost TWICE as much as the new Losmandy OPW. IMO the still perfect worm bearing alignment, added ease of worm mesh adjustability and the 50% reduction in cost of the new Losmandy OPW design overcomes the slight loss in potential PE reduction and allows mounts without HP worms on the RA axis (the important axis for imagers) to buy the OPW and HP worm for less than the cost of an EMPTY first generation OPW alone!?

This thinking was proven on my own G11 mount. I had previously tested my standard Gemini 2-mini powered G11 mount with 2-piece worm blocks and HP worms on both RA and DEC axes with a Stellarvue 50mm f/4 guidescope, QHY5L-II Mono autoguider camera and PHD2 doing the honors. I typically saw unguided error in the 3.5-5.0 arcsecond range before I did the usual Losmandy G11 modifications and 0.34-0.5 arcseconds RMS when autoguided. After Scott updated my 15 year old G11 to full current G11G specs with the new tucked-in motors, RA Extension Kit, newly redesigned OPWs and reusing my existing worm gears. The mount turned in slightly better results (3.5 arcseconds unguided and 0.31-0.46 arcseconds RMS guided) using the same QHY5L-II Mono autoguider at the prime focus of a Meade 10" f/6.3 SCT OTA on a very cold night which had my mount lagging severely requiring that I adjust the worm mesh to free up both the RA and DEC axis to test.?

This of course is just one mount but I imaging your results would be about the same.?

Chip
tom
 

I don't think that answers his question...

On 10/12/2017 2:10 PM, chiplouie@... [Losmandy_users] wrote:
Hi nmatxin,
If you already have the brass worm gears installed in your mount you already have high precision worms installed and I highly recommend buying the newly redesigned Losmandy one piece worm block for BOTH RA and DEC axes. If your mount has the old silver colored standard precision worms then I suggest buying the new Losmandy OPW with a new high precision worm installed and install it on the RA axis and an additional new Losmandy OPW for the DEC axis using your existing worm gear. This configuration will get your tracking PE way down and save you $100 over buying a new pair of HP worm OPWs. If money is not an issue bring your G11 up to the current standard with a pair of HP worm loaded OPWs.
My thinking is this: the first generation Losmandy OPW may have had slightly higher potential to reduce periodic errors because the old OPW fully aligned the gearbox and worm gears on the same axis to eliminate the very small velocity differences inherent when an Oldham coupler is misaligned, this is inherent to the Oldham coupler design. The potential error improvement was very small but cost TWICE as much as the new Losmandy OPW. IMO the still perfect worm bearing alignment, added ease of worm mesh adjustability and the 50% reduction in cost of the new Losmandy OPW design overcomes the slight loss in potential PE reduction and allows mounts without HP worms on the RA axis (the important axis for imagers) to buy the OPW and HP worm for less than the cost of an EMPTY first generation OPW alone!
This thinking was proven on my own G11 mount. I had previously tested my standard Gemini 2-mini powered G11 mount with 2-piece worm blocks and HP worms on both RA and DEC axes with a Stellarvue 50mm f/4 guidescope, QHY5L-II Mono autoguider camera and PHD2 doing the honors. I typically saw unguided error in the 3.5-5.0 arcsecond range before I did the usual Losmandy G11 modifications and 0.34-0.5 arcseconds RMS when autoguided. After Scott updated my 15 year old G11 to full current G11G specs with the new tucked-in motors, RA Extension Kit, newly redesigned OPWs and reusing my existing worm gears. The mount turned in slightly better results (3.5 arcseconds unguided and 0.31-0.46 arcseconds RMS guided) using the same QHY5L-II Mono autoguider at the prime focus of a Meade 10" f/6.3 SCT OTA on a very cold night which had my mount lagging severely requiring that I adjust the worm mesh to free up both the RA and DEC axis to test.
This of course is just one mount but I imaging your results would be about the same.
Chip
 


Hi Tom,

Based on the number of Ovision worm returns and the often very mixed reviews in testing by people who spent a lot of money for often no better results or worse results than a carefully tuned Losmandy 2-piece worm block setup I think the Ovision worm is an very pricey significantly less reliable option.?

The new Losmandy OPW design offers similar performance to an Ovision worm that tests good but the Losmandy OPWs seem to have more consistent real world test results. Additionally with the the addition of improved worm mesh adjustability with the threaded adjuster and the ability to buy a PAIR of new Losmandy OPWs with a brand new HP worms installed for less than the cost of a single Ovision I think the new design Losmandy OPW is the better way to go. Most imagers are using an autoguider and the results using an autoguider do not seem to get much better than 0.3-0.4 arcseconds RMS which is typically much better than the seeing will allow under ideal conditions.?

If this doesn't clearly answer the OP's questions I'm not sure what the OP is asking.?

Chip?

?? ??
 

Hey gang,

I privately emailed the originator with this opinion also...

--------------------

I'll attach a writeup on improvements that I made to the Losmandy OPW and why I added a Belleville spring washer to it.
The Ovision product has one of these already designed in at the far end, I think.

Chip Louie is correct in that the Ovision mounting does not also line up the gearbox and Oldham coupler.? That lineup is done by the Losmandy OPW system.? An offset in angle between the gearbox shaft and the worm shaft can result in additional oscillation that I think can be corrected by PEC, because the offset creates a 2X worm frequency.? However, it is always better not to have these oscillations in the system.??

-------------------
I no longer know the prices of these things... but once one is going for the ultimate in what the system can do, I don't think that matters.
The question is:? what gets you the ultimate capability if you also put effort into it.
The way the mount is designed, and what was left out of the design, I can see why the really well engineered Ovision system could end up not meeting its PE capability.? The interaction of the worm PE with the Oldham coupler angle or offset is a fundamental issue that is simply not treated by the machinists.? But careful owners can adjust it and test the PE; PEC and autoguiding take you the rest of way below the atmospheric seeing level.??

- Michael


On Thu, Oct 12, 2017 at 3:37 PM, chiplouie@... [Losmandy_users] <Losmandy_users@...> wrote:
?


Hi Tom,

Based on the number of Ovision worm returns and the often very mixed reviews in testing by people who spent a lot of money for often no better results or worse results than a carefully tuned Losmandy 2-piece worm block setup I think the Ovision worm is an very pricey significantly less reliable option.?

The new Losmandy OPW design offers similar performance to an Ovision worm that tests good but the Losmandy OPWs seem to have more consistent real world test results. Additionally with the the addition of improved worm mesh adjustability with the threaded adjuster and the ability to buy a PAIR of new Losmandy OPWs with a brand new HP worms installed for less than the cost of a single Ovision I think the new design Losmandy OPW is the better way to go. Most imagers are using an autoguider and the results using an autoguider do not seem to get much better than 0.3-0.4 arcseconds RMS which is typically much better than the seeing will allow under ideal conditions.?

If this doesn't clearly answer the OP's questions I'm not sure what the OP is asking.?

Chip?

?? ??




--
Michael Herman
mobile: 408 421-1239
email: mherman346@...
tom
 

Hi Chip,

I think you hit it that time. I cannot speak first-hand about the Ovision worm but have thought about going that route and as I understand it they document the PE of the worm and Scott does not. I was hoping medium/long term users of the Ovision worm would chime in with their experience.

Tom

On 10/12/2017 6:37 PM, chiplouie@... [Losmandy_users] wrote:
Hi Tom,
Based on the number of Ovision worm returns and the often very mixed reviews in testing by people who spent a lot of money for often no better results or worse results than a carefully tuned Losmandy 2-piece worm block setup I think the Ovision worm is an very pricey significantly less reliable option.
The new Losmandy OPW design offers similar performance to an Ovision worm that tests good but the Losmandy OPWs seem to have more consistent real world test results. Additionally with the the addition of improved worm mesh adjustability with the threaded adjuster and the ability to buy a PAIR of new Losmandy OPWs with a brand new HP worms installed for less than the cost of a single Ovision I think the new design Losmandy OPW is the better way to go. Most imagers are using an autoguider and the results using an autoguider do not seem to get much better than 0.3-0.4 arcseconds RMS which is typically much better than the seeing will allow under ideal conditions.
If this doesn't clearly answer the OP's questions I'm not sure what the OP is asking.
Chip
 

Tom,?

Scott doesn't need to characterise his worms, obviously measuring them is not particularly valuable as many Ovision worms with glowing certificates performed very poorly. If you get a Losmandy HP worm that is not up to snuff Losmandy usually will help you tune your mount and if it is bad replace the suspect part.?

Chip
tom
 

Thanks Chip...I just have not seen the number of Ovision worm returns and very mixed reviews. Must have missed them.

Tom

On 10/12/2017 7:43 PM, chiplouie@... [Losmandy_users] wrote:
Tom,
Scott doesn't need to characterise his worms, obviously measuring them is not particularly valuable as many Ovision worms with glowing certificates performed very poorly. If you get a Losmandy HP worm that is not up to snuff Losmandy usually will help you tune your mount and if it is bad replace the suspect part.
Chip
 

Hi Tom,

They are out there if you look on some of the European sites and there are several US web pages with these issues too but usually they are resolved by returning the worm to Ovision and getting a replacement. Some continued to have issues and ultimately returned them for refund and later corrected the problem with a Losmandy OPW and HP worm. This was all a few years ago now but there definitely have been some issues with the Ovision worms that were confirmed by replacement with Ovision or Losmandy worms.

Chip?

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