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First Light On a 2021 18" Obsession f/4.2 Ostahowski UC

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#1 Bob S.

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Posted 31 July 2021 - 10:54 AM

Strange times call for changes in one's activities. Since the pandemic, my activities had been mostly limited to golf, autocrossing, motorcycling, hanging around the house reading with my wife, and exercising. Then, an almost new 18" f/4.2 Ostahowski-mirrored UC pops up on the radar and after the umteenth time trying to leave the hobby, I happily got sucked in once again. Last night, in West Central Florida, the Clear Sky Clock finally showed anticipated great skies and it was time to test out the UC=Ultra Compact Obsession.

 

This latest iteration of this UC is not your grandfather's original UC that used a seat belt sling and did not have lateral stiffeners for the hinged altitude bearings of the Virtual Mirror Box. This scope came equipped with a fabulous, very high Strehl Ostahowski primary mirror, coated cable sling and the above-mentioned altitude bearing stiffeners. Upon getting the scope, I spent several full days just reading the operator's manual, adjusting various components and digesting as many of the nuances in the design as my non-engineer brain could absorb. I must say that Dr. Kriege's latest iteration, based on ease of transport, lifting and use is frankly a home run. I can see why he finally migrated away from his beloved and venerable Classic Obsession with their conventional mirror boxes and rocker boxes. Given the design goals of lighter weight and ease in transporting in smaller vehicles, the UC is less rigid than the Classic but has very acceptable damping times on the order of about 2 seconds without a ServoCAT drive which would make the scope track more rigidly. 

 

I had rolled the scope out of my air conditioned house before sunset and left my microfiber towels on the face of the primary mirror and left covered with the mirror cover to let it thermally equilibrate with the steady Florida temps. By the time I had set it ready to view, the primary/secondary was apparently fully equilibrated because the views through my 21mm Ethos in my Paracorr 2 were showing perfectly round, pinpoint stars after I had completed a final tweak of the collimation. I had to use the Ethos 21 to dial in the Telrad 1x finder and the 50mm Stellarvue correct image visual finder. The Summer Triangle was up and I used Lyra to get the finders aligned and then moved the scope to the Double Double in the Lyra constellation. The stars were already pretty pinpoint and I was able to use a 13mm Ethos to comfortably view the 4 stars at 169x. I then pointed the scope to Albireo, the absolutely beautiful contrasting two very colorful stars also at 169x. The seeing was not fully supporting my 6mm Ethos at 365x. 

 

Now that I had things working well, it was time to go to M4 and M80 in Scorpious and later to return to Sagittarius and the surrounding area of the Milky Way to see some old favorites including some pinpoint open clusters and double stars with my 21mm and 13mm Ethos ep's. I had earlier taken a peek at Saturn as it was rising and the views were sharp at 169x with lots of detail. While staying dark adapted, I cruised around without an OIII filter to known nebulae and could barely make out some of the targets with the Swan (M17) being most prominent without a filter that I need to buy. 

 

As always, part of the magic of the night was viewing Saturn and then Jupiter as they rose higher in the sky at about almost 11 p.m. last night. The rings of Saturn are slowing closing up since being fully open in 2017 and are about half way to edge-on in 2025. Jupiter and the Jovian Moons were looking good at 169x and the GRS was rotating into view. I had some lucky views with my 6mm Ethos at 365x but the seeing would rarely support the magnification so I stuck to the 13mm Ethos. Sadly, I only had about 1 hour on the planets before the seeing went from about 8/10 to about 6/10 and I ended my session at a few minutes before midnight. By that time, the Milky Way above the house was pretty much faded out and the air mass had become more humid.

 

Some thoughts on the UC and especially the Terry Ostahowski primary mirror. In terms of transport, the VMB=Virtual Mirror Box that Kriege has designed makes the scope soooo much easier to transport to darker skies. At age 72, I can almost comfortably lift the VMB into my car by myself. The rocker platform only weighs 7 pounds. With the use of the wheelbarrow handles, the scope fully assembled seems to only weigh about 10 pounds and I can literally lift the handles with one finger of each hand. The 6-truss pole system is fully attached and so assembly of the scope is relatively straight forward once you learn the little tricks on how to manipulate the components for ease of assembly. There is relatively little shift of the laser from 30-80 degrees of movement of the scope and the laser remains somewhere in the center spot donut throughout the arc. I already addressed the damping times and with Ethos ep's, you don't need to be perturbing the telescope as often to keep it on target so the views are generally very stable as the target moves through the eyelens.

 

In summation for first light, all I can say is that I am VERY happy that I bought this scope. I did not use the 32k encoders and the Argo Navis last night but they will help me get to all of the DSO's I want to revisit from almost 20 years in the hobby. As I am aging out, it represents a very functional and pleasant large aperture scope that does not have all of the attendant limitations of a conventional Newtonian since it is so skeletonized. The relatively fast Ostahowski mirror with the Paracorr 2 and the Ethos ep's are a beautiful match with very bright, high contrasty sharp images produced. Finally, I have been in the process of reading all of Anthony Hillerman's Navajo Tribal Police mystery novels on my Kindle Paperwhite and a very strange thing occurred last night that caused me some pause. At about 10:30, I heard a very faint noise and rustling about 20 feet from me at the edge of my driveway and sensed I was being watched. I made a sort of barking sound and witnessed the shape of a coyote scamper away with the sound of his claws grabbing the concrete pavement. If I were a Native American, and specifically a Navajo, I would have wondered what the presence of the coyote meant? Thanks for putting up with such a long first light report. Bob Schilling


Edited by Bob S., 31 July 2021 - 11:32 AM.

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#2 cuzimthedad

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Posted 31 July 2021 - 10:59 AM

Great report and welcome back Bob! Congratulations on the new scope!


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#3 rajilina

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Posted 31 July 2021 - 11:05 AM

Thanks for this report! I’ve been trying to find a recent-but-used 18” UC and have been waffling back and forth on whether it will be too much scope for me. This gives me a fair amount of incentive to forge ahead with my quest! 


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#4 havasman

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Posted 31 July 2021 - 11:39 AM

Thanks for the fine report. It's good to see you back.


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#5 Bill Jensen

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Posted 31 July 2021 - 12:28 PM

Welcome back Bob! Glad you are back enjoying the night sky. 


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#6 Doug Culbertson

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Posted 31 July 2021 - 01:07 PM

Well, well, Howdy stranger! Congrats on the new scope; does it all fit in your 'vette? smile.gif

 

One thing that I've always been curious about is how the UC does in Florida's humidity, specifically whether the exposed primary dews over rapidly? I don't know if the humidity is as bad in Lecanto, but you know how bad it is up here. 


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#7 Bob S.

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Posted 31 July 2021 - 01:36 PM

Doug,

 

I share some of the same concerns that you do about the primary and Florida dew. In my post, I described leaving the microfiber towels underneath the plastic mirror cover until the primary equilibrated with the ambient air temps. I figured that leaving the towels on the face of the mirror slowed the equilibration process and prevented the primary that had come out of my air conditioned house from instantly dewing up. The temperature delta between my home and the outside air temp was about 10 degrees last night and a fair amount of humidity out of doors.

 

Kriege includes several things that help mitigate the dew issues. The scope came equipped with a shroud that has a semi-rigid skirt that keeps the shroud out of the light path. The shroud does not come all the way down to below the mirror and in fact ends about 10 inches above the mirror. Included with the scope is a 8" tall kydex lower shield that attaches around the entire primary mirror to help prevent things from dropping on the mirror or dirt getting direct access to the primary. I also think that the lower Kydex shroud helps prevent dewing of the primary. There is also a fan installed on the back of the mirror cell that can be run to also prevent dewing if things get pretty juicy. Kriege also recommends running the rear fan on the back of the primary when you bring the scope in from an observing session to mitigate formation of dew on the primary. The secondary came equipped with a 9-volt dew heater that compares the secondary mirror's temp with the ambient temp (likely Astrosystems dew heater). 

 

As I mentioned in the original post, I spent a great deal of time looking at all of the design elements of the scope and trying to understand from an engineering standpoint, how all of the various elements interact with each other. The tolerances are quite tight for most of the features and in some respects, I would consider the telescope to be a bit on the "fussy" side. It does not seem to be as immune from abuse as say the Classic designs of the Obsessions or other name brand conventional wood Newts seem to possess. OTOH, because of the more skeletonized design, the scopes is extremely compact and will easily fit with the wheelbarrow handles on and the scope fully assembled through a conventional doorway. The width of the scope with the wheelbarrow handles attached is only about 28.75 inches wide fully assembled.

 

I need to change my Avatar. After 15 months of ownership, I sold the Vette and bought a brand new car that consistently wins the SCCA National Solo Championships (autocross) in the G Street class. It is a front wheel drive Honda Civic Si and with race wheels and 200 tw race tires and a rear sway bar that  makes it competitive at the National level if only I had the skills to drive it that precisely. I have gotten significantly faster over the past 6 years but have the issue of decreasing reflexes and information processing to contend with as I keep getting older for some reason??? In other words, I am tickled to find myself in the middle of the pack and not almost dead last like when I started this game. The entire 18" UC fits very comfortably in my 2020 Honda Civic Si sedan with the rear seats down.


Edited by Bob S., 31 July 2021 - 01:38 PM.

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#8 Doug Culbertson

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Posted 31 July 2021 - 01:48 PM

Doug,

 

I share some of the same concerns that you do about the primary and Florida dew. In my post, I described leaving the microfiber towels underneath the plastic mirror cover until the primary equilibrated with the ambient air temps. I figured that leaving the towels on the face of the mirror slowed the equilibration process and prevented the primary that had come out of my air conditioned house from instantly dewing up. The temperature delta between my home and the outside air temp was about 10 degrees last night and a fair amount of humidity out of doors.

 

Kriege includes several things that help mitigate the dew issues. The scope came equipped with a shroud that has a semi-rigid skirt that keeps the shroud out of the light path. The shroud does not come all the way down to below the mirror and in fact ends about 10 inches above the mirror. Included with the scope is a 8" tall kydex lower shield that attaches around the entire primary mirror to help prevent things from dropping on the mirror or dirt getting direct access to the primary. I also think that the lower Kydex shroud helps prevent dewing of the primary. There is also a fan installed on the back of the mirror cell that can be run to also prevent dewing if things get pretty juicy. Kriege also recommends running the rear fan on the back of the primary when you bring the scope in from an observing session to mitigate formation of dew on the primary. The secondary came equipped with a 9-volt dew heater that compares the secondary mirror's temp with the ambient temp (likely Astrosystems dew heater). 

 

As I mentioned in the original post, I spent a great deal of time looking at all of the design elements of the scope and trying to understand from an engineering standpoint, how all of the various elements interact with each other. The tolerances are quite tight for most of the features and in some respects, I would consider the telescope to be a bit on the "fussy" side. It does not seem to be as immune from abuse as say the Classic designs of the Obsessions or other name brand conventional wood Newts seem to possess. OTOH, because of the more skeletonized design, the scopes is extremely compact and will easily fit with the wheelbarrow handles on and the scope fully assembled through a conventional doorway. The width of the scope with the wheelbarrow handles attached is only about 28.75 inches wide fully assembled.

 

I need to change my Avatar. After 15 months of ownership, I sold the Vette and bought a brand new car that consistently wins the SCCA National Solo Championships (autocross) in the G Street class. It is a front wheel drive Honda Civic Si and with race wheels and 200 tw race tires and a rear sway bar that  makes it competitive at the National level if only I had the skills to drive it that precisely. I have gotten significantly faster over the past 6 years but have the issue of decreasing reflexes and information processing to contend with as I keep getting older for some reason??? In other words, I am tickled to find myself in the middle of the pack and not almost dead last like when I started this game. The entire 18" UC fits very comfortably in my 2020 Honda Civic Si sedan with the rear seats down.

 

Excellent post, thanks for that! I honestly don't see myself going larger than 14.5", but one often dreams in spite of limited time to observe. Sounds like a heck of a telescope, and a nice fit for you. 


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#9 Bob S.

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Posted 31 July 2021 - 02:00 PM

Copy of Si (640x427).jpg Doug,

 

When I first started racing the Si, I center punched a cone with my new car before I put on a beefed up rear swaybar and had significant understeer. That is why in the next race, I put on painter's tape on the front end until I got the rear sway bar that neutralized the understeer. Now, it does not understeer and rotates quite nicely with reduced body roll.

 

And now to getting back on topiclol.gif

 

Doug, Vic Menard opined on several occasions to me that 18" of aperture is likely the ideal large aperture scope in Florida for beating the seeing conditions most frequently. Funny thing is that because he had previously owned a 22" Starmaster, his dear wife strongly suggested that when he replaced his scope with a StarStructure that he get another 22" scope even though he thought that the 18" would perform more consistently in our skies. As was the case, he got another 22" f/4 and kept saying the mantra, "Happy Wife, Happy Life". 


Edited by Bob S., 31 July 2021 - 08:27 PM.

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#10 Bill Jensen

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Posted 31 July 2021 - 06:01 PM

I guess you really have a FAST dob , Bob! smile.gif


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#11 CHASLX200

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Posted 31 July 2021 - 06:06 PM

Well, well, Howdy stranger! Congrats on the new scope; does it all fit in your 'vette? smile.gif

 

One thing that I've always been curious about is how the UC does in Florida's humidity, specifically whether the exposed primary dews over rapidly? I don't know if the humidity is as bad in Lecanto, but you know how bad it is up here. 

SCT's don't last 10 mins in my area on the gulf.   Lecanto is only around 60 miles north of me.
 



#12 a__l

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Posted 31 July 2021 - 06:49 PM

Bob S, welcome back to hobby :)


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#13 turtle86

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Posted 31 July 2021 - 07:28 PM

Bob,

 

Welcome back and thanks for the report!  I remember recently seeing that scope on AM and being very tempted by it since the seller is also in Florida.  I still have (and love) my 18" SM after all these years, but have to say as I get older, something lighter and more compact like the 18" UC definitely sounds appealing. I'm also intrigued by those Reginato scopes from Italy.

 

From your report, it sure sounds like there have been a lot of nice improvements made to the UC. You're going to have a blast with it.  I'm not a Native American either, but I would sure take the appearance of that coyote as a very good sign! smile.gif


Edited by turtle86, 31 July 2021 - 07:29 PM.

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#14 peleuba

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Posted 31 July 2021 - 07:39 PM

Sadly, I only had about 1 hour on the planets before the seeing went from about 8/10 to about 6/10 and I ended my session at a few minutes before midnight. 

 

I would be ecstatic if I had an honest 6/10 seeing most nights.

 

As I have told you in texts and on the phone, I am glad you are back Kemosabe.  


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#15 Bob S.

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Posted 31 July 2021 - 08:16 PM

I would be ecstatic if I had an honest 6/10 seeing most nights.

 

Paul, I remember picking up a 20" f/4.3 Zambuto/Starmaster in San Francisco about 15 years ago and taking it directly up into the California mountains to the Golden State Star Party. I was frankly shocked at how relatively poor the seeing was. The transparency was terrific but the seeing wasn't. However, folks along the coastal areas of Southern California reportedly get to enjoy some pretty good laminar flows from the Pacific Ocean that produce superb seeing.

 

Here in West Central Florida, I am about 9 miles from the Gulf of Mexico and we generally have daily onshore or offshore winds from the Gulf or the Atlantic ocean. Where I live in the State, the width from shore to shore is only about 115 miles across. The beautiful laminar air flowing from the water makes the Florida Keys (sandwiched between the Atlantic and Gulf by a thin strip of land) where the WSP has been held, especially favorable for incredible planetary views. 

 

When I first was getting into the hobby some 20 years ago, Florida was experiencing many years of semi drought conditions and the humidity was lower for a bunch of years. Many of us with larger aperture Newtonians were routinely getting 1000x plus nights on certain objects and I remember one morning at Chiefland Astronomy Village looking between the stars in the core of M13 at about 2250x in a 30" telescope with a newbie in the hobby that morning at about 4 a.m. I advised him that I had never seen that view before and that we might never see that again in a regular eyepiece which has remained true to this day. 

 

I am suspecting that there will be some incredible nights with this Ostahowski primary based on the interferometer certs I shared with you and Terry's terrific in-house coatings but do not want to publicly report due to the age old problem of people comparing certs as if they are the end all/be all of performance which we know to not be quite accurate because of numerous other variables. What I particularly like about the UC is that the 18-point mirror cell seems to work pretty well and is balanced such that turning the collimation screws are very easy to turn. The fact that the mirror is two inches thick does not cause me any pause because I have some concerns about gravity induced astigmatism in some thinner mirrors that might not be adequately supported. As we know, mirror supports are critical to primary mirror performances. A thickness ratio of 1 to 9 is fine by me and since the primary mirror is made from fused silica, it is an inherently stable substrate to begin with. I feel fortunate to have retired in a place where we can still get some incredible nights from time to time. Last night was a good start waytogo.gif


Edited by Bob S., 31 July 2021 - 08:54 PM.

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#16 dustyc

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Posted 31 July 2021 - 10:48 PM

Thanks for the report! 

What I like best about my UC is it just gets out of the way and allows me to enjoy the views. I have just the Argo and no drive. At higher powers I get about the same settling time of about 2 seconds. 


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#17 CHASLX200

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Posted 01 August 2021 - 05:53 AM

Does the UC have handles so it can rolled outside?



#18 Bob S.

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Posted 01 August 2021 - 07:23 AM

Does the UC have handles so it can rolled outside?

Yes, They are metal handles with captive bolts in each handle that screw into the altitude bearings. The scope also has captive chains and turn buckles on the front and back on the ground board that keep the Virtual Mirror Box attached to the rocker box when using the wheelbarrow type aluminum handles. Install and removal of the handles takes less than 1 minute. The only slow down is that you have to remove the altitude encoder arm because it provides interference with the handles. 



#19 CHASLX200

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Posted 01 August 2021 - 07:30 AM

Yes, They are metal handles with captive bolts in each handle that screw into the altitude bearings. The scope also has captive chains and turn buckles on the front and back on the ground board that keep the Virtual Mirror Box attached to the rocker box when using the wheelbarrow type aluminum handles. Install and removal of the handles takes less than 1 minute. The only slow down is that you have to remove the altitude encoder arm because it provides interference with the handles. 

My 18" Obsession just does fit out my door. Tried Jupiter with it back in May and it looked great at 450x. This a 2002 made Dob with a Galaxy mirror. I see you moved just north of me now. I can't keep track, i think you were on the east coast not long ago.


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#20 ghilios

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Posted 01 August 2021 - 05:47 PM

Bob, congratulations on the new scope! I got a 22" UC with ArgoNavis and ServoCat just the other month, and had my first stellar night of seeing last night. Jupiter, Saturn, and globs are completely insane and mesmerizing at a clear 500x. Despite being technically savvy, I've had quite the learning curve with the automation. Good luck, and feel free to reach out if you get stuck!


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#21 Bob S.

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Posted 02 August 2021 - 06:53 AM

Bob, congratulations on the new scope! I got a 22" UC with ArgoNavis and ServoCat just the other month, and had my first stellar night of seeing last night. Jupiter, Saturn, and globs are completely insane and mesmerizing at a clear 500x. Despite being technically savvy, I've had quite the learning curve with the automation. Good luck, and feel free to reach out if you get stuck!

I see that you are software engineer so you definitely have a leg up on the learning curve for automation. Fortunately, I have owned a bunch of scopes with ServoCATS and Argo Navis DTC's so am quite familiar with their operation. I used to teach advanced statistics many years ago and found learning how to create a pointing model in TPAS on the AN to be quite challenging with a fairly steep learning curve at the time. I would have to go back and relearn TPAS if I wanted to used it but fortunately will not be adding the complications of drives to my scope so it is likely overkill for that level of precision.

 

I would love to hear how the ServoCAT has been working on your 22" UC. I had heard some rumors about earlier UC's presenting some problems with the altitude bearings "bumping" at the hinge point and throwing the system off but have not heard anything definitive in a long time. I really appreciate the altitude bearing stiffener bars that Kriege included in his latest iterations of the UC's. What you and I know is that driven scopes really stabilize images and generally prevent the perturbations due to truss pole flexture. I used to very much appreciate driven scopes when looking at objects in the higher magnifications ranges especially like planetary objects and also being able to study targets without having to expend energy on hand guiding of the scope. 


Edited by Bob S., 02 August 2021 - 10:13 AM.


#22 a__l

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Posted 02 August 2021 - 07:37 AM

TPAS this is not the best solution for a collapsible design.
There are four things you need to do.
1. Minimal side slip, by any available means.
2. Check the operation of the Az encoder. This requires an eyepiece with a cross. Rotate the telescope clockwise and counterclockwise several times 360 degrees. Polaris star or terrestrial object. Your encoder digital value should be +/- 1. If more, fix the problem. For example, it took me up to 3-5 days to solve this problem with the replacement of the entire Az mechanism of the bolt.
3. You need to set the center of the Alt encoder with maximum precision. Better is more accurate than 1 mm. After taking measurements with a ruler to three points. 2 arc ends and perpendicular.
4. If you are using one battery 12V for servo motors and Argo, you need to install two ferrite rings at the Argo input for encoders. Until I realized this problem, it took more than a month to solve it.

The Nexus DSC is good for this, the lithium battery will allow you to forget about this problem. 

 

And one more nuance. If your Alt bearing are inaccurate, your optical Alt encoder may freeze. Do not overtighten the screws on the rocker for the encoder foot. This, of course, will not improve accuracy, but will allow the encoder to work without freezing.


Edited by a__l, 02 August 2021 - 07:51 AM.

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#23 a__l

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Posted 02 August 2021 - 03:25 PM

And one more nuance for optical US Digital encoders.
Follow the correct sequence when attaching the foot.
Washer (blue arrow) - encoder foot - washer (red arrow) - nut. Tighten firmly. Otherwise, incorrect operation (pinching without the first washer) or free play (without the second) is possible.

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  • Washers.jpg


#24 stubeeef

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Posted 03 August 2021 - 08:15 PM

Thanks for all the stormy wx Bob....


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#25 Tyson M

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Posted 03 August 2021 - 11:30 PM

A fine report Bob, thanks for sharing.
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