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Drive Correctors

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#51 Nick W.

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Posted 29 September 2019 - 11:49 AM

Anyone still using one of these? I stil use mine with C8 forks, Unitron 152, and the old Dynamax 8. Use to use one with my old Cave and Parks Superior Mounts.  I'm holding on to this one cause they're getting harder to find. 

 

Post a picture of yours!

rolo - any chance you have the manual for yours I could crib from? We have one of the DigiTraks installed in our observatory that was built in 1970. Old Boller and Chivens 16" Cassegrain pier mounted is what it is hooked up to. Seems to still be working fine (despite being shoved under a desk for a very long time and maybe getting a little water on it). I don't have much info on how to calibrate it and such, anything would be helpful to at least have on file.

 

Thanks!

~Nick



#52 ltha

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Posted 29 September 2019 - 02:27 PM

Heck, I just bought an original Schaefer drive corrector for the Schaefer mount I am using to carry the Cave 12.75” Newtonian. Now I have to figure out how to change the existing plugs to match one another.....

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#53 G-Tower

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Posted 30 September 2019 - 06:23 AM

Wow, I haven't seen one of those in decades! Does everything work?



#54 John Rogers

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Posted 30 September 2019 - 08:07 AM

I picked this up on a whim.  I don't know if it works as I am reluctant to plug it in, although both fuses are intact.

 

It appears to me that Bill Schaefer built custom boxes for folks.  It must have used a lot of power.  The heat sink on the bottom is huge!

 

Schaffer_1.jpeg Schaffer_3.jpeg Schaffer_2.jpeg

 

In the early 1970s, there was a schematic of a variable frequency controller published in Sky & Telescope.  I built one from that schematic, including designing and etching my own circuit board.  It worked well, but was not as complicated as this one!


Edited by John Rogers, 30 September 2019 - 08:16 AM.


#55 DAVIDG

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Posted 30 September 2019 - 09:51 AM

 Your Schaefer drive corrector is using a circuit board that  Willmann Bell sold  to make a West Bradford drive corrector . The design was published in Auguast 1975 Sky and Telescope. Here is a link https://archive.org/...8-pdf/page/n55 

 

              - Dave 


Edited by DAVIDG, 30 September 2019 - 11:32 AM.


#56 John Rogers

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Posted 30 September 2019 - 11:19 AM

That is amazing Dave!  I did not realize that Willmann Bell sold anything but books.

 

There does not appear to be any markings on the printed circuit board to indicate a manufacturer.  However, a cursory glance at some of the ICs show the same numbers that appear on the schematic.

 

The device I built from scratch appeared in the October 1970 issue of Sky and Telescope on page 237.



#57 DAVIDG

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Posted 30 September 2019 - 11:32 AM

 Here is a  link to  the Willmann Bell ad that lists the circuit boards. I built both the Saxon version from the Jan 1975 Sky and Tel and the West Bradford unit from August 75 using the Willmann Bell circuit boards. Still have both and they still work great. 

https://archive.org/...09-cbr/page/n39

 

                  - Dave 


Edited by DAVIDG, 30 September 2019 - 11:33 AM.

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#58 photoracer18

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Posted 30 September 2019 - 01:38 PM

I still have one of the those mdl 300 Digitrak II's also. Plus a pair of single axis ones. I got Bob to give me a set of his schematics after he retired so I could fix them. That was while I was working for Gary Hand. I tried to get Orion to give me copies of the Accutracks also but they declined even though they were no longer repairing them also. I am holding onto mine in case I ever get ambitious enough to tackle that early Cave observatory mount that came with the 12.5" convertible Cass/Newt. Been trying to find an original C8 fork + the DC DEC drive as a test bed but nothing in the right price range has popped up. I do have a spare hand control for one of the dual drive controllers like the D II but have not tested it.

I did get an early C8 fork assembly and also found an Astro-Physics DEC drive kit for the the C8 out of the classifieds. So one of my 2 Vogel Digitrak II models is fully functional and one has a blown DEC side. The working one has a number of mods on the circuit board so I need to meter those out and add them to the schematics before I attempt to repair he second one. I also have 2 working single axis Vogel VE200 models plus one oddball that is a 200 in a 300 case including the hand-paddle port. In the Accutrack side I have one working dual axis model although the DC DEC port has an odd connector on it.

Vogel Digitrak VE200 single axis drives only have DC power input and are designed to power scopes like the RV-6 in the field although they could do an old AC powered C8 also. They have fast and slow buttons on the box for drive control.

Vogel Digitrak II VE300D dual axis drives AC RA and DC DEC with the DEC connector the stereo plug used by Celestron and Meade among others. They have dual AC or DC power input and 4 button hand-paddles and variable power out for an illuminated reticle eyepiece. A good candidate to modify the handpaddle port for an ST-4 autoguider port as it uses the Celestron RJ11 jack. I plan on attempting that maybe next year after I setup the DEC drive in my AT-9 as DC.

All Vogels have Sidereal, Lunar, and Solar rate buttons plus a variable rate control. 

Accutracks also come in single and dual axis controllers. All of them I think have dual power input. Single axis controllers have a hard wired 2 button controller and dual axis ones have a hard wired joystick controller. The top of the line 4000 Quartz model has digital settable frequency control in addition to the requisite Sidereal, Lunar, and Solar rotary switch that all Accutracks have.

 

I don't have any examples of S&S Optical or dual AC Vista controllers as of yet. Lumicon rebadged other brands of controllers (1 of my Vogel VE200 is one).

 

Since my post last year I am pretty sure I am going to chuck that weird drive setup on the back of the Cave early observatory mount for the spare 7.1" Byers Starmaster I have stored away. Then I can work on the simpler DEC drive setup.


Edited by photoracer18, 30 September 2019 - 01:43 PM.

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#59 asphy

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Posted 20 November 2019 - 11:44 PM

Hello everyone,

I am a new member in this forum and this is my first post, so I am sorry if I do not do the things as by book.

Recently got two vintage Celestrons “orange” C5 and C8. I think I am lucky as optics and motors are in perfect condition, so I decided to make them operational as much as I can.

 

My question is basically about building an inverter and oscillator based drive corrector for AC motors SYNCHRON , 3W ,120V, 60 Hz both Celestrons are US version. 

As I am in New Zealand, ~240V/50 even with step down transformer the scopes will move too slow to be used. 

So, after searching the WEB, I found 2 schematics and  I am wondering whether some of you guys have had already build those ones.

The first was published in Astrophotography for the Amateur, 2nd edition by Michael Covington.(1999) (p285-286)
Here is his schematics ( some of you may recognise?)

 

Attached File  U1.pdf   101.09KB   24 downloads

Attached File  U2.pdf   164.26KB   19 downloads

The second is shown in the Andrew’s blog:  http://darkerview.co...dpress/?p=21405  and seems to be much more modern:

DriveCorr.png

In contrast compared with 1980’s one.( cannot read all details but the schematic is attached for comparison)

 

DriveCorrector-1.jpg.png

 

So, anyone has build successfully any of those I found or any other?

I would appreciate any help and advice.

 

Plamen



#60 DAVIDG

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Posted 21 November 2019 - 09:51 AM

 I have built and repaired many drive correctors including the second schematic in your post. It is the Saxon circuit from Jan 1975 Sky and Telescope. https://archive.org/...01-pdf/page/n49

 Still works great after almost 40 years. What I suggest thou is that you purchase a 12volt 60 Hz DC/AC converter and if you don't want to run off a 12 volt battery buy or built a simple 12 DC power supply. Most of the commerical DC/AC converter you can modify so you can add slow and fast buttons and also change the rate. They use a circuit very similar to the Saxon unit with 555 timer and resistor and capacitor and timing circuit. 

  If you decide to build the Dark View unit you'll need the code and programmer to program the PIC micro controller. The Saxon circuit uses simpler parts and requires no programming. I would use a LM7805 voltage regulator to the replace the 5 volt zener and 2n3122 transistor 

 

 

             - Dave 


Edited by DAVIDG, 21 November 2019 - 09:52 AM.

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#61 semiosteve

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Posted 21 November 2019 - 12:40 PM

Astro Physics Model 8002 DA drive corrector with Model 7002 Autoguider.   Original owner.

 

attachicon.gif AP 001.jpg

 

 

A couple of Accutracks, I bought the one on the left around 75, 76.

 

attachicon.gif Accutrak 001.jpg

 

 

This Sidereal Electronics unit came with my Cave 10" Custom Super Deluxe.  

 

attachicon.gif Sidereal Electronics 001.jpg attachicon.gif Sidereal Electronics 002.jpg

 

 

All of these still get used.

I've got that same Sidereal Electronics unit but mine is labelled "Celestron"...worked fine with my old Cave 8" RFT clock drive.

 

But get this, I just acquired my first SCT - an original Celestron Super C8 Plus. It is in great shape but was missing a power cord. Turns out the Sidereal Unit uses the same style oval 3 prong power cord, so I was able to immediately validate the Byers drive worked just fine .

 

So that  Sidereal Electronics unit I picked up on a whim for $30 now  supports.two classic scopes.


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#62 Don W

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Posted 21 November 2019 - 12:59 PM

A quick aside, Willman Bell used to also sell mirror grinding supplies, glass, abrasives, kits etc.


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#63 photoracer18

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Posted 21 November 2019 - 04:40 PM

I have managed to collect a number of old school drive correctors in the last several months including Digitrak 400, Digitrak II 200/300, Accutrack 3117 and 3118, plus some parts. All but one of them so far is working. So far all these models are AC RA and DC DEC if they are dual axis. Some are single axis RA only. Also acquired some spare Hurst CA motors.


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#64 svenk123

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Posted 22 November 2019 - 03:23 AM

Hello Plamen,

 

because i am doing astrophotography, i had the same problem in the past. 110V/60Hz fork mount and 230V/50Hz grid supply here in Europe. Since i have not found any commercial drive corrector on the market i have build one on my own. The electronic circuit to generate a stable 110V/60Hz AC to track the scope at exactly siderial speed is not very complicated and can be realized with a microcontroller.

Send me a PM, when interested in the gerber files, part list and firmware.

 

I have used my latest version over 2 years on several fork mounts. It provides the following functions:

 

- Input Voltate 11-14 V to operate on batteries oder external AC power supply

- Siderial tracking (60.1643 Hz), Lunar tracking (58.696 Hz), Solar tracking (60.0 Hz), Kings rate tracking

- ST4-Guding input

- Fast/Normal slewing in DEC and RA

- DEC motor output for JMI Motodec or JMI Motofocus

- USB interface for configuration and diagnosis, it simulates a USB-CGST4-Device that you can used it in PHD2 oder other astronomy software tools nativly

 

CS

 Sven

 

 

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#65 DAVIDG

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Posted 22 November 2019 - 10:21 AM

Hello everyone,

I am a new member in this forum and this is my first post, so I am sorry if I do not do the things as by book.

Recently got two vintage Celestrons “orange” C5 and C8. I think I am lucky as optics and motors are in perfect condition, so I decided to make them operational as much as I can.

 

My question is basically about building an inverter and oscillator based drive corrector for AC motors SYNCHRON , 3W ,120V, 60 Hz both Celestrons are US version. 

As I am in New Zealand, ~240V/50 even with step down transformer the scopes will move too slow to be used. 

So, after searching the WEB, I found 2 schematics and  I am wondering whether some of you guys have had already build those ones.

The first was published in Astrophotography for the Amateur, 2nd edition by Michael Covington.(1999) (p285-286)
Here is his schematics ( some of you may recognise?)

 

attachicon.gif U1.pdf

attachicon.gif U2.pdf

The second is shown in the Andrew’s blog:  http://darkerview.co...dpress/?p=21405  and seems to be much more modern:

attachicon.gif DriveCorr.png

In contrast compared with 1980’s one.( cannot read all details but the schematic is attached for comparison)

 

attachicon.gif DriveCorrector-1.jpg.png

 

So, anyone has build successfully any of those I found or any other?

I would appreciate any help and advice.

 

Plamen

Since your down in New Zealand you have a bigger problem then the 240/50 hz voltage in your country vs  the  120/60  voltage for the  motors made to be used in the US. You need to reverse the direction of the drive and that requires reserving the direction of the two motors in the base. You can only do that by replacing the motors.

 

                     - Dave 


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#66 bjkaras

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Posted 25 November 2019 - 07:02 PM

Here's the scope it was from. A 10" Cave Cass.

Wow, this is a real beauty!



#67 photoracer18

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Posted 27 November 2019 - 05:17 PM

Since your down in New Zealand you have a bigger problem then the 240/50 hz voltage in your country vs  the  120/60  voltage for the  motors made to be used in the US. You need to reverse the direction of the drive and that requires reserving the direction of the two motors in the base. You can only do that by replacing the motors.

 

                     - Dave 

Dave he should be able to reverse the motors by switching one starting cap lead to the other lead. Unless they are not AC Synchronous motors. 



#68 DAVIDG

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Posted 27 November 2019 - 06:47 PM

Dave he should be able to reverse the motors by switching one starting cap lead to the other lead. Unless they are not AC Synchronous motors. 

 There are no  starting caps in the motors used in these vintage  Celestrons. They are two wire  synchronous type like a common Synchron units. The reversible type have two separate coils and are either 3 or 4 wire units. This  allow the use of  a capacitor along with the indicatance of the coils to cause a 90 degree phase shift in the AC waveform between the two coils and allow the direction to changed. 

   When you purchased one of these vintage Celestrons you could have the mount built with 220 volt 50 hz motor for use in the Northern hemisphere  ie countries in Europe or 220 volt 50 hz motor that rotate in the opposite direction for use in countries in the Southern Hemisphere.  The motors will need to be replaced with ones that  at least rotate in the opposite direction and at the correct speed. Then a drive corrector could be built to provide the correct voltage and frequency. Here is a  link to one of Celestron's catalogs that offers different motors for the Southern Hemispheres https://wiki.telesco..._Literature.pdf

 

               - Dave 


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#69 photoracer18

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Posted 29 November 2019 - 05:12 PM

You are right I stand corrected. Spending too much time lately on Caves and Schaefers.



#70 Geo.

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Posted 30 November 2019 - 11:31 AM

For DIY folks should look at Mike Covinton's  Alcor system http://www.covington...lcor/index.html

 

It works with 50 or 60Hz. It can be a simple RA only controller or dual axle by adding a LM293 to drive a DC Dec motor of relays for an AC motor.

 

Alcor_C5.jpg

 

http://www.covington...s-Published.pdf


Edited by Geo., 30 November 2019 - 11:33 AM.

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#71 bjkaras

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Posted 11 December 2019 - 11:58 PM

Someone mentioned about the Vista drive corrector. That’s what I use now on my Parks 10” f5. I got it in 1987 and it still works. I did have to adapt it to my drive though. That involved removing the capacitor from the original Dec control box and placing it in the drive corrector box. I also had to replace the Parks connector with the one supplied by Vista so that the dec drive would work. I’ll post a picture of it later if anyone is interested.



#72 DAVIDG

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Posted 27 December 2019 - 08:53 PM

  A couple of months ago a good friend sent me a Celestron drive corrector that was designed to be used for C14. A C14 has some unique electronics and the corrector is design to run both the RA drive that runs on AC and the DEC drive and RA slewing drive that runs on either 12 volt DC for slow slewing or 24 volts  DC for fast slewing.

   I thought it would  be a pretty simple fix because about 90% of the time it is one of output transistors  goes bad. On this one both output transistor were cooked and the output transformer as well. After replacing them, the unit worked but the transistors were running red hot so something was still wrong. Sometime in the past the unit has been "repaired" so you never know what has been done.

   So today I got back on the project and started  at one end of the circuit and worked toward the other, drawing out the circuit and checking everything. After about an hour I discovered the problem, one of  the resistors that bias the base of one of  the  transistor was the wrong value. It needed to be 1K and it was 10K so it wasn't allowing enough current to fully turn on one of the output transistors. That caused it to run hot and eventually fail. I replaced  it with the correct value  and now the both transistors are running cool and the output voltage is right where it is supposed to be with  a nice shape to the waveform. 

   Now I need to stuff " 10lbs of Chocolate into a 5lbs box ! "  and get all the parts back into the case.  Once all the parts are back in the case I'll calibrate the output frequencies to drive the scope at Solar, Lunar and Sidereal rate. Here is a  picture showing the AC voltage coming out of  the unit with  all it "guts" all over the table. 

 

                Happy 2020 !

 

                  - Dave 

 

C14DRIVECORRECTOR.jpg


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#73 asphy

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Posted 01 January 2020 - 04:23 AM

Thanks to Dave, Sven, Geo and everybody who got involved in my query. Thank you so much guys!

 

My project of making C5 &C8 operational is moving but very slowly.  So far I found  only 2 x 620 SYNCHRON motors (0.75 RPH, 3W, 220V AC 50Hz)  for South Hemisphere but only for C5 to replace the US ones. So while keep looking for SYNCHRON motors for C8 ( they read 1 RPH) I could do some steps ahead in drive correctors.

I would like to stick with something simple like the one schematics shown by Geo, and while I am building it I would like to look for some of vintage drive correctors as shown in the Viking 1 post.

Does anyone can suggest any surplus astronomy equipment place in the US who may agree to sell and ship to NZ ?? ( Getting such things in NZ is almost impossible)

 

Any help and  additional info will be appreciated.

 

HAPPY NEW 2020 YEAR !!

 

Plamen



#74 DAVIDG

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Posted 01 January 2020 - 02:54 PM

  A couple of months ago a good friend sent me a Celestron drive corrector that was designed to be used for C14. A C14 has some unique electronics and the corrector is design to run both the RA drive that runs on AC and the DEC drive and RA slewing drive that runs on either 12 volt DC for slow slewing or 24 volts  DC for fast slewing.

   I thought it would  be a pretty simple fix because about 90% of the time it is one of output transistors  goes bad. On this one both output transistor were cooked and the output transformer as well. After replacing them, the unit worked but the transistors were running red hot so something was still wrong. Sometime in the past the unit has been "repaired" so you never know what has been done.

   So today I got back on the project and started  at one end of the circuit and worked toward the other, drawing out the circuit and checking everything. After about an hour I discovered the problem, one of  the resistors that bias the base of one of  the  transistor was the wrong value. It needed to be 1K and it was 10K so it wasn't allowing enough current to fully turn on one of the output transistors. That caused it to run hot and eventually fail. I replaced  it with the correct value  and now the both transistors are running cool and the output voltage is right where it is supposed to be with  a nice shape to the waveform. 

   Now I need to stuff " 10lbs of Chocolate into a 5lbs box ! "  and get all the parts back into the case.  Once all the parts are back in the case I'll calibrate the output frequencies to drive the scope at Solar, Lunar and Sidereal rate. Here is a  picture showing the AC voltage coming out of  the unit with  all it "guts" all over the table. 

 

                Happy 2020 !

 

                  - Dave 

 

attachicon.gifC14DRIVECORRECTOR.jpg

 Happy 2020 !  Need a little help from my Cloudy Night Family.  I fixed this vintage C-14 drive corrector and the circuits are working but it has me puzzled. There are two parts to this unit. One is  a classic variable frequency circuit that uses a 555 timer and transformer to make 120 volts AC that one can vary frequency  to control the speed that the scope tracks at. Makes perfect sense

   The other part is what has me puzzled. It is bistable oscillator circuit that use the two transformer. It takes 12 volt DC and make either 12 or 24 volts AC. The AC feeds 120 volt style plug on the back of the unit that is labeled  12 -24 AUX AC. I have a classic C-14 and there is no place were it needs either 12 or 24 volts AC. The DEC motor runs on 12 of 24 volt DC not AC and the DC is made inside the telescope.  There is no place on the mount were one could connect 12 or 24 volts AC. 

   Like I said this circuit is also working perfectly but I have no idea why one would need these voltage with  a classic C-14.  Anybody have manual or know what  these voltages were used to power ?

 

                    - Dave 



#75 Terra Nova

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Posted 05 January 2020 - 01:16 PM

Here is a very interesting piece that I thought would be a salient entry to this topic. I wonder if anyone here can ad some information about it. It’s a 12V DC drive corrector with a built-in AC Inverter. It was built and marketed in limited numbers for the C8 back in the 1970s. The C8’s AC power cord plugs into the unit, and the unit plugs into a standard 12Vport such as a car’s cigarette lighter or a battery jump-starter. It was given to me by a good friend and fellow CN’er. Here’s what he had to say about it. 

 

When I bought my C8 back in '77, I got it from a guy in San Jose CA who was just starting business as a telescope vendor, and had put an advertisement in Sky & Telescope. At that point, he hadn't yet opened up a storefront, and was still amassing inventory and storing it in his three-car garage.”

“So it turned out that he was also an electronics guy... and while talking with him on the phone about shipping and such for the C8 (in the end, my girlfriend and I drove up from Santa Barbara to San Jose, to pick it up), he reminded me that its drive motors were AC-only, and also that they only had a fixed sidereal rate. He then offered to make a little rheostat-controlled inverter/slow-motion control for it (Right Ascension only, of course) that could be plugged into a car's cigarette lighter... and of course I took him up on it. Here's what it looks like:”

“The black knob is the rheostat, which is used to adjust the tracking rate. The black and red buttons very slightly speed-up (red) and slow-down (black) the Right Ascension drive rate... so they can be used like RA slow-motion controls to help with centering an object, instead of using the manual RA Slo-Mo control, which as you know, is pretty course.”

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