174 replies to this topic

[Henryscope]

Hubble / Dave

 

Can you elaborate on how to modify a 12VDC to 120VAC inverter to be a tracking controller for an old Celestron C8 with the 120 VAC drive?

I have an inverter I bought at Menards. It is a Masterforce model number 260-9519. Can you point me to a schematic? Do I do something with the circuit to vary the frequency, or do something with the 120VAC output to vary the frequency?

Thnk you for any help!!

Henry

Henryscope

[Goofyboy1]

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

Im interesting in your design!

[GalaxyPiper]

Hubble / Dave

 

Can you elaborate on how to modify a 12VDC to 120VAC inverter to be a tracking controller for an old Celestron C8 with the 120 VAC drive?

I have an inverter I bought at Menards. It is a Masterforce model number 260-9519. Can you point me to a schematic? Do I do something with the circuit to vary the frequency, or do something with the 120VAC output to vary the frequency?

Thnk you for any help!!

Henry

Henryscope

These are two different animals. An inverters job is to turn D/C into A/C and that's it.

A corrector deals with A/C frequency, changing the frequency of the A/C high or lower than the wall frequency of 50 or 60 Hz. There is no voltage change, only frequency. The A/C clock motors use frequency to keep timing accurate. By changing it, you can control the speed of the motor slightly fast or slower.

 

To answer your question as to how to turn an inverter into a drive corrector you can follow these steps: 

 

http://bobmay.astron...sc/drivcorr.htm

 

Always use caution when dealing with high volages, working on equiptment that is unplugged and high voltage capacitors that are discharged.

 

Best of luck to you.

 

Bryan

Edited by GalaxyPiper, 14 February 2025 - 02:44 PM.

[cavedweller]

I own a few old school drive correctors and they all are inverters that convert 12 VDC into 120 VAC with variable frequency; most also have a 12VDC power supply that can operate the inverter circuit from a 120 VAC input source.

[DAVIDG]

Hubble / Dave

 

Can you elaborate on how to modify a 12VDC to 120VAC inverter to be a tracking controller for an old Celestron C8 with the 120 VAC drive?

I have an inverter I bought at Menards. It is a Masterforce model number 260-9519. Can you point me to a schematic? Do I do something with the circuit to vary the frequency, or do something with the 120VAC output to vary the frequency?

Thnk you for any help!!

Henry

Henryscope

 Got back to message #59 and the schematic at the bottom of the page.  How this circuit works it that it is using a resistor(s) and capacitor to make a RC  time base. Change the value of resistor(s) or the capacitor and that changes the frequency that the unit is making. The lower left section of the schematic is  the hand controller that allows the user to adjust the output frequency with a variable resistor and two push button to override the normal operating frequency and speed it up or slow it down by pushing the appropriate button. One button is normally closed (NC) and is wired across a resistor. When that button is pushed the resistor is now added to the circuit, increasing the resistance and the frequency is reduced. The other button is normal open (NO), when that button is pushed, the current now flows through  the switch, taking the resistor it is wired across out of  the circuit and the current flow through the switch which is low resistance and that make the frequency increase.

   So to modify an exiting DC/AC inverter you have to determine how the time base is working. On many it uses a resistance/capacitance circuit. Then you cut into the circuit and make a circuit similar to hand paddle circuit that adds or removes resistance to change the speed. Since all these DC/AC inverters circuits are not the same, you have to understand how it works to modify it to make the frequency variable.

 

                  - Dave   

[svenk123]

Im interesting in your design!

Here is the complete design: https://github.com/svenk123/alcor

 

CS

  Sven

[GalaxyPiper]

Here is the complete design: https://github.com/svenk123/alcor

 

CS

  Sven

This is very nice, but the very first component on the list, "Teensy 2.0 development board", has stopped production in 2022. So now is in the "unobtainable" category.

 

This would need to be reevaluated and brought back up to date with different components.

[Kristian Bang Jensen]

I have just completed (with the patient help of Sven and a colleague of mine) an alcor corrector following Sven's design. More than happy with the tracking ability of this corrector.  I had no major issues finding older parts, including the teensy 2.0.

 

CS Kristian 

[Kasmos]

Thanks Ken.  The one on mine is Mount Wilson.  I am trying to put a timeline together to better understand the history of Sidereal Electronics.  It appears that they made a lot of different boxes, but there does not seem to be a whole lot of information about their history on the web.  If I can determine when they were located at Mount Wilson, it will help me date the manufacture date of a used Meade telescope that I recently picked up.

 

For what its worth, the Baseline Road address comes up as a private residence on Google.

I guess I never responded, but mine has the Mount Wilson address and it was purchased in 1978.

Tim also mentioned his NOS Mount Wilson example came with a 1976 Sand Cast C8.

[cavedweller]

I recall The Mt Wilson address is a PO Box, no? I was thinking that they were never physically at Mt Wilson, Maybe they thought it would give them some clout in the market to use that address.

[photoracer18]

I have the Accutrack model 3117.  Notes from my first test are simply "Accutrack - All works".  I don't have an Accutrack 4000 to test. Not sure of the differences. 

Here is the wave form from the first test. I have pictures of the wave generated using both 120VAC and 12VDC inputs. The output waves are basically the same with either input source.  This seems to be a decent square wave. There is a very faint but longer spike at the moment of voltage reversal. While the spike is very faint and extremely short duration, it is long to represent a possible high volt jab that might be stressing the electronics insulation/separation. I don't know if that spike is a concern or not. It might be common and so weak that it doesn't matter.  I'm just recording. I will get a decent scale value on the second test to calculate the spike voltage.  

 

Had room to add a picture of the back hooked up for the first 120VAC input test. 

4000 model was the programmable one. Had the 4 digit counter on the front that you could put a set of numbers in to make small adjustments in the output for things like atmospheric dispersion. Earliest ones I have seen were made by Vista. The manual for my Kencore modified C8 fork has a chart with numbers that give the dispersion correction numbers for various altitudes above the horizon to correct the drive speed. It has a main gear that barely fits in the lower mount case and a worm gear that sits outside the case because its too big to fit inside, like an oversized Byers drive model. I also have a 2117 and used to have a 2118 Accutrack drive corrector. This was during the time I acquired a Schaefer AT-9 mount and I was looking for a dual AC model Vista corrector. Also during the time after Bob Vogel (Digitrak) retired and gave me some of his schematics.

[photoracer18]

Thanks Dave,

 

I have all the math and graph characteristics down. I used to teach all this stuff, albeit over 30 years ago. I was on faculty at a local Comm. College and taught everything they had into post calc. I was also Professor of their math lab which allowed me to get into all the side lines for the trade programs such as math for nursing and math for CNC, etc.  I adore application math, teaching and using, and it is still my hobby. 

It's not like a bicycle, it's more like a foreign language. If you don't use it, you lose it.  I'm pretty rough from diff. eq. on up now, but don't need it....much, and I still have all my text books (some back to 6th grade) to brush up if I want. Fun stuff.

 

I had both leads hooked up but didn't want to overlay the wall current in order to keep the images cleaner. I set the wall current scale to match basic lines on the grid to simplify estimations and the strictly visual (qualitative) comparisons. I specifically framed two cycles, one each side of center, or one in center with a half on each side. I think that helps to embody the big picture. Now that I have all the plugs, adapters, test leads, paper clips, etc., I will probably run through each unit again briefly when I post them. I'll have my own additional questions by then too.  It would be easier to use my DMM (nice one) for frequencies if I decide to record specifics. I believe my DMM will do a good job of extracting the rms voltage from the distorted waves. I'm starting to get into this so not sure how far I'll go.

 

Quick digression. One of my fond memories was using determinates to calculate machinery setting to make parts for a tesseract. Determinates made the computations incredibly fast and easy. Though relatively simple, I could not do that off the top of my head now for the life of me, literally. The parts fell together like a glove. I made two tesseracts and gave one to Dr. Daniel Sukle at FRCC community college. He was by far the most extraordinary instructor I ever had the privilege to study under, and so acclaimed by many others. I still have the second one I made. 

With the exception of the first amateur built working stellar photometer I completed in 1964 as a Junior in HS with my advisor. I learned everything I know about electronics from Frederick Terman of Stanford U while in the US Navy during Nam. The father of Silicon Valley.

Edited by photoracer18, 25 February 2025 - 08:15 PM.

[Kasmos]

I recall The Mt Wilson address is a PO Box, no? I was thinking that they were never physically at Mt Wilson, Maybe they thought it would give them some clout in the market to use that address.

Yes it was, but that's a long walk up the mountain just to get the mail.  

[Oliveira]

Hi,
I bought an Astro-Physics 8002 DA drive corrector and the starguider  7002 from a guy in Germany, but the 7002 came incomplete. Despites It's mint,  with eyepiece and cable, it didn't work at all. When I decided tho open it to service I noticed that its internal parts were absent. As far as I know, it employed a beam splitter prism and light controlled transistors. So I am asking for help in way to rebuild that historical piece of hardware.

Does anyone here have diagram or image of the autoguider system?

Any information will be wellcome.

I thanks in advance.

[GalaxyPiper]

All companies were required to submit their circuit diagrams to the F.C.C.

A company went into business selling the old diagrams to technicians.

 

I believe they were called, "Sams PhotoFax"....and all you had to do was give them the model, year, and device name and for a small fee send you the circuit diagram of old radios and electronics.

 

You can start here:  https://www.samswebsite.com

  

Bryan

Edited by GalaxyPiper, 05 March 2025 - 05:02 PM.

[Oliveira]

All companies were required to submit their circuit diagrams to the F.T.C.

A company went into business selling the old diagrams to technicians.

 

I believe they were called, "Sams PhotoFax"....and all you had to do was give them the model, year, and device name and for a small fee send you the circuit diagram of old radios and electronics.

 

You can start here: https://www.samswebsite.com 

  

Bryan

Thanks for the information! I will seek for it!

[GalaxyPiper]

Thanks for the information! I will seek for it!

That should have said F.C.C...I'm correcting my post.

 

And this must be the article or device you are talking about.

 

https://www.astro-ph...ures/770601.pdf

Edited by GalaxyPiper, 05 March 2025 - 05:00 PM.

[GalaxyPiper]

Well, I just tried Sam's Photofax myself with no luck. I did a test using RCA and it brought up 18,353 entries using "Brand " and "equal to" in the search fields. So it does work, but I guess only for radios and T.V.s.

Edited by GalaxyPiper, 06 March 2025 - 01:19 PM.

[GalaxyPiper]

This information was provided in a Cloudy night forum titled "Vintage C14 Documentation":

 

https://www.dropbox....yf7bf&e=1&dl=0 

 

This does not provide the circuitry you are looking for, but goes in-depth on how to use it and may give you more insight.

 

Post #16 on this thread describes this device liking red stars more than blue ones, and is more accurate with red stars.

 

This device probably uses light sensitive diodes in conjuction with a stair step generator. I built one very simular in my college days. It used a comparator of the two light sensitive diodes to provide a differential in voltages that then drive two DC motors forwards or backwards depending on the amount of light hitting them.

 

I imagine this device follows along in the same manor.

Edited by GalaxyPiper, 06 March 2025 - 04:43 PM.

[Oliveira]

Hi,
That is right, it is the AP 7002 and I thanks for the documentation you provided.
I spent some time searching for it in the FCC archive but nothing about Astro-physics Inc or specifically the device returned. I also ask for the seller in Germany about the parts but according to him, he bought the device from a scientific equipament shop in in confidence that it was functional as stated in the invoice that he sent to me. The driver is functional, only que autoguider is not. I have somewhere here an old article from NASA describing an autoguider with four photocells, that I suppose used a close system to th AP 7002.
As far as I know, the 7002 was the first autoguider available commercially to amateur astronomers, then my interest into rebuilding it.

[GalaxyPiper]

Hi,
That is right, it is the AP 7002 and I thanks for the documentation you provided.
I spent some time searching for it in the FCC archive but nothing about Astro-physics Inc or specifically the device returned. I also ask for the seller in Germany about the parts but according to him, he bought the device from a scientific equipment shop in in confidence that it was functional as stated in the invoice that he sent to me. The driver is functional, only que autoguider is not. I have somewhere here an old article from NASA describing an autoguider with four photocells, that I suppose used a close system to the AP 7002.
As far as I know, the 7002 was the first autoguider available commercially to amateur astronomers, then my interest into rebuilding it.

Yes, for the amateur this was the first commercially available auto guider that goes back to the 70s. I would email Astro-Physics themselves and ask for more detail and explain your reason for preserving this device.

If they are the type of company I would hope they are, they would be accommodating to you.

 

https://www.astro-ph...om/contact-us/ 

[Oliveira]

Yes, for the amateur this was the first commercially available auto guider that goes back to the 70s. I would email Astro-Physics themselves and ask for more detail and explain your reason for preserving this device.

If they are the type of company I would hope they are, they would be accommodating to you.

 

https://www.astro-ph...om/contact-us/ 

Great idea! I will do it.

I have bought some equipment from AP back in the 90s and early 2000s. In those times, Mrs. Marjorie used to answer the fax messages! I still have my EDF155 with field corretor, that I waited almost two years to deliver. It worth every day of waiting and cent spent for. Great old days!!!
 

Edited by Oliveira, 07 March 2025 - 01:28 PM.

[photoracer18]

I don't think that is actually an A-P product, I think they just rebranded it from Geiseller Electronics which became part of Orion later on. I think their own brand name was Accutrack.  This was technology that predated the SBIG ST-4 autoguider which was better technology than the 7002 Star Tracker.

[DAVIDG]

 Your autoguider is most likely based on the March and April Gleanings for ATM's articles in Sky and Telescope " An automatic guider for astrophotography"  The design uses a beam splitter to feed star light to two  photo multiplier tubes. The beam splitter  has knife edge at 90 degrees so it can tell if a star is drifting in RA or DEC and as the star drifts into the knife edges the brightness decrease and the circuit turns on the corresponding motors to move correct it's drift.

   In the Astrophysic device,  the PMT's  were most likely replaced with at the time "modern" low voltage photodiodes and most likely feed to differential OP amps. 

 

           - Dave  

[GalaxyPiper]

I don't think that is actually an A-P product, I think they just rebranded it from Geiseller Electronics which became part of Orion later on. I think their own brand name was Accutrack.  This was technology that predated the SBIG ST-4 autoguider which was better technology than the 7002 Star Tracker.

You may be correct on this. Accu-track called theirs a model "2200" I believe.

 

I think it was used in conjuction of the Accutrack 2119B model drive corrector.

 

Funny thing is, Rodger Tillhill relabelled it as a "Star Trap", but in reality, it was an Accutrack 2119B.

 

An old C.N. thread can be found here: 

 

https://www.cloudyni...ron-forkmouny/ 

Edited by GalaxyPiper, 08 March 2025 - 05:34 PM.