Alt Az mount

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Larry Mayfield

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Sep 11, 2022, 7:55:38 PM9/11/22
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Every time I turn around I find something else that needs to be done to make a functional Alt Az mount, for RA only, no photography.

Is there and outstanding cookbook somewhere that I can own or consult to figure stuff out for this mount and drive systems? 

 

I have been, probably dumbly, assuming that the earth turns at a steady rate and that I can figure out he rate of speed per degree of transit for both the elevation and rotation of the system. And that since tracking starts at the same time and has to finish at the same time that this is a simple thing to do.  I am not a photographer and so do not need field corrections the keep planetary objects in the same frame of reference for long time exposures.  

 

I need some hand holding to get me going correctly in a step by step mode without any assumptions that I know what I am doing, lol.  Seeking the simplest alt az system that can be put together by an ordinary old (80) man with tools, welder etc.  My system will use two old dish 500 parabolas with off set feeds. Why, just ‘cause I want to, lol.

 

Is there anyone out there who will take my age spotted hand and guide me to success int eh shortest possible time or provide me with a really complete cook book on how to get it done?

 

Sure would be a help to an old geezer. Maybe others also.

 

Many thanks, and all replies welcomed

 

Larry

Pahrump, NV

 

 

Jack Lobingier

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Sep 11, 2022, 11:16:06 PM9/11/22
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Larry, this maybe overkill for what you want, but it might give you some ideas.

Jack



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Larry Mayfield

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Sep 12, 2022, 1:12:21 AM9/12/22
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Jack, what may be overkill? I see noting with ideas or directions. Were you to attach a link or document or?

larry

Jack Lobingier

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Sep 12, 2022, 6:16:07 AM9/12/22
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Yep, sorry about that.  I tried to attach my presentation from the last SARA Conference, but it was too big to send.  If you have the handouts from the Conference, mine is the one on a tracking and positioning system for alt/ax mounts.

Alex P

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Sep 12, 2022, 6:29:17 AM9/12/22
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" make a functional Alt Az mount, for RA only, no photography....

I have been...  assuming that the earth turns at a steady rate and that I can figure out the rate of speed per degree of transit for both the elevation and rotation of the system. And that since tracking starts at the same time and has to finish at the same time that this is a simple thing to do "

==================================================================================================

Hi Larry,
The only practical way to make an Alt Az mount "track in RA" is to elevate the Alt Axis to correspond to your local Latitude and point it at the NCP.
That converts an " Alt Az " into an Equatorial Mount and  the Az can be clocked at a constant rate of 15 deg/hr.
( the " Meade Wedge effect " )
Otherwise, both Alt and Az rates would require constant changing with respect to the location of an object in the Sky.

( see attached graphic )

Alex KK4VB

Az_El_vs_EarthRotationPath.jpg

Marko Cebokli

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Sep 12, 2022, 8:41:35 AM9/12/22
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Hello Larry!

Polar mount (as called by satellite people, aka "equatorial" by
astronomers) has also the following pluses:
- does not rotate polarization (not important with unpolarized sources
or circular pol)
- can be a "clock drive" (no angle feedback, just a single constant
speed motor).

When I began with EME, I used improvised polar mounts, see a wooden
version:
http://lea.hamradio.si/~s57uuu/eme/dish1m1.jpg
slightly improved version, works in snow, too:
http://lea.hamradio.si/~s57uuu/eme/sl5.jpg

But a serious polar mount is usually mechanically more challenging to
build than an alt/az, so in the end, I ended with an alt/az.



With an alt/az, without a computer, it is quite hard to do sideral
tracking.
A small computer like Raspberry, is powerful enough, and Python is
simple (I heard), with many useful libraries available, maybe even
ready-made tracking solutions.

I am working on an "universal" solution, but as my projects go, might
take a longer time to be finished.
Slides in Slovene language are here:
http://lea.hamradio.si/~s57uuu/s5/RIS/RIS2019/RIS2019.pdf
a polar mount made with satellite "hands", and the original Andrew dish
mount, is on page 6. It must be on a south facing hillside, and has a
rather limited angle coverage.

Marko Cebokli


On 12.09.2022 12:29, 'Alex P' via Society of Amateur Radio Astronomers
wrote:
> _" MAKE A FUNCTIONAL ALT AZ MOUNT, for RA only, no photography...._
>
> I have been... assuming that the earth turns at a steady rate and that
> I can FIGURE OUT THE RATE OF SPEED PER DEGREE OF TRANSIT FOR BOTH THE
> ELEVATION AND ROTATION OF THE SYSTEM. And that since tracking starts
> at the same time and has to finish at the same time that this is a
> simple thing to do "
>
> ==================================================================================================
>
> Hi Larry,
>
> The only practical way to make an Alt Az mount "track in RA" is to
> elevate the Alt Axis to correspond to your local Latitude and point it
> at the NCP.
>
> THAT CONVERTS AN " ALT AZ " INTO AN EQUATORIAL MOUNT AND  THE AZ CAN
> BE CLOCKED AT A CONSTANT RATE OF 15 DEG/HR.
> ( the " Meade Wedge effect " )
>
> Otherwise, BOTH ALT AND AZ RATES WOULD REQUIRE CONSTANT CHANGING with
> respect to the location of an object in the Sky.
>
> ( see attached graphic )
>
> Alex KK4VB
>
>>
>
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Michiel Klaassen

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Sep 12, 2022, 9:33:22 AM9/12/22
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Hi Larry,
I understand that you have a lot of experience with cars. So, I will give some of my ideas using their parts.

1. A polar mount
You take a rear axle from a truck and mount that axel with 'A' frames to be parallel to the earth axis.
On the differential drive shaft you mount an electric motor with reduction.  On one wheel you mount the antenna. On the other wheel you mount a lever which can activate the brake. If engaged the antenna will move slowly counter clockwise compensating the earth rotation.
If the brake is free, then you can move the antenna to the desired declination of the source. No software needed.

2. An Az/alt mount.
Buy a 10 ft sea container. On one long side you mount two car wheels without the tires. The wheels run on a concrete ring covered with a round iron strip.
In the centre of the other long side you construct a pressure bearing onto a concrete pillar. The antenna(s) are mounted on the upper ring and moved in elevation with a worm wheel.
problem is; wife's consent is needed.
another problem is that a lot of software is needed.
As always, my solutions are not as good as your own.
Regards
Michiel

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Larry Mayfield

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Sep 12, 2022, 9:43:29 AM9/12/22
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Jack, sorry, I do not have the handouts… where can I obtain them as a down load if you know?

 

Larry

Jack Lobingier

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Sep 12, 2022, 10:09:52 AM9/12/22
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It’s on YouTube.  

Larry Mayfield

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Sep 12, 2022, 11:11:32 AM9/12/22
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Michiel,

Yes, a bit of experience with cars. And quite a bot with building and operating my equatorial mount 2 meter dish. Which is down for some repairs right now.

 

What I am seeking is basically a tutorial on actually building an ALT-AZ system. I do have a broad understanding of the manner in which it works. I have a tracking mechanical system I am designing  for the Alt and one for  the AZ as well. But, dog gone it, every time I think I have it in hand, I find that I am missing something, like for instance the tracking equations and the parametric inputs for them to work. Code would be good for me to examine to see what is considered for tracking.   Occasionally I read something that brings into question of “I don’t know what I don’t know” aspect because I do not have the recipe or cookbook describing the basic elements. And it seems like that cookbook does not exist. Heck just a list of things that have to be considered would be a great help I think.  I am a technical degreed old engineer with a good math education and certainly an aeronautical and astronautical engineering degree as well. So I am not unfamiliar with how to make things work when I know what the tings are without having to reinvent the wheel every time I try and do something.  I am trying to develop a very short baseline (really short) interferometer  using two recycled dish offset antenna with a common clock signal and tuned electronics  in support of an experiment I want to try for adding (multiplying) the two signals to gain a better receiver input signal.  

 

I code pretty well in Arduino IDE the RPI Python and even Excel basic and Fortran of all things and have a son who is a Computer software guru when help is needed.  I use NI Multisim to analyze and design circuitry for the systems I fab up. When I have the mechanicals figured out, I also model my systems using Cadre Pro 6 for vibration and structural defects and deflections under loads as well.

 

Just that my tired old brain is missing some basic input on the what is needed not necessarily the how although that would be wonderful as well. .

 

Anyway, that’s for the attempt to switch me over to equatorial mounts and or using automotive stuff for the fab of systems. I already do that kind of stuff.

 

A recipe would be good…..

 

Larry

Pahrump, nv

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Michiel Klaassen
Sent: Monday, September 12, 2022 6:33 AM
To: sara...@googlegroups.com
Subject: Re: [SARA] Alt Az mount

 

Hi Larry,

Larry Mayfield

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Sep 12, 2022, 1:16:03 PM9/12/22
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Thanks, Jack, I appreciate it and you knowledge!

Marko Cebokli

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Sep 12, 2022, 3:52:08 PM9/12/22
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Larry,

There are two types of az/alt mounts: the "azimuth over elevation" type,
mostly used in antenna test range positioners, and "elevation over
azimuth", most popular for astronomy, weather radars, etc. Here, the
whole elevation mechanism is "on top" of the azimuth mechanism, and
turns with it.

Assuming you want to make the second type, you need a vertical axis for
azimuth, with suitable motors and gears, and some kind of angle readout
(encoders, resolvers, potentiometers, selsyns, etc.)
On top of the rotating part, you need a perpendicular (horizontal) axis
for elevation, again with motors and readouts, and in most cases, with a
counter weightfor the dish. For elevation readout, you can also use
accelerometers from electronic levels, or a potentiometer with a weight
hanging of it's axis.
As suggested before, the car differential case is a nice T shape thing
to unite the azimuth and elevation axes.
Then you need some servo electronics (usually done with microcontrollers
these days), to read the angles and drive the motors to the desired
position. I think you can find encoder interface and motor PWM boards
ready made for the Arduino.
For sideral tracking, you then just need to convert from declination and
right ascension to azimuth and elevation, for your location. This is a
simple coordinate system rotation, just a few sines and cosines. Python
has a ready made "astropy" or something library, that can do that for
you.
It is in fact the advent of computers, that made az/el mount popular
with astronomers, who once used equatorial mounts almost exclusively.
If you made equatorial mounts in the past, an az/el should be a piece of
cake - just make the polar axis vertical!

Marko Cebokli
> Just that my tired old brain is missing some basic input on the _WHAT_
> is needed not necessarily the _how _although that would be wonderful
> as well. .
>
> Anyway, that’s for the attempt to switch me over to equatorial
> mounts and or using automotive stuff for the fab of systems. I already
> do that kind of stuff.
>
> A recipe would be good…..
>
> Larry
>
> Pahrump, nv
>
> FROM: sara...@googlegroups.com <sara...@googlegroups.com> ON
> BEHALF OF Michiel Klaassen
> SENT: Monday, September 12, 2022 6:33 AM
> TO: sara...@googlegroups.com
> SUBJECT: Re: [SARA] Alt Az mount
>
> Hi Larry,
>
> I understand that you have a lot of experience with cars. So, I will
> give some of my ideas using their parts.
>
> 1. A polar mount
>
> You take a rear axle from a truck and mount that axel with 'A' frames
> to be parallel to the earth axis.
>
> On the differential drive shaft you mount an electric motor with
> reduction. On one wheel you mount the antenna. On the other wheel you
> mount a lever which can activate the brake. If engaged the antenna
> will move slowly counter clockwise compensating the earth rotation.
>
> If the brake is free, then you can move the antenna to the desired
> declination of the source. No software needed.
>
> 2. An Az/alt mount.
>
> Buy a 10 ft sea container. On one long side you mount two car wheels
> without the tires. The wheels run on a concrete ring covered with a
> round iron strip.
>
> In the centre of the other long side you construct a pressure bearing
> onto a concrete pillar. The antenna(s) are mounted on the upper ring
> and moved in elevation with a worm wheel.
>
> problem is; wife's consent is needed.
>
> another problem is that a lot of software is needed.
>
> As always, my solutions are not as good as your own.
>
> Regards
>
> Michiel
>
> parac.eu [8]
>
> On Mon, Sep 12, 2022 at 12:41 PM Marko Cebokli <s57...@hamradio.si>
> wrote:
>
>> Hello Larry!
>>
>> Polar mount (as called by satellite people, aka "equatorial" by
>> astronomers) has also the following pluses:
>> - does not rotate polarization (not important with unpolarized
>> sources
>> or circular pol)
>> - can be a "clock drive" (no angle feedback, just a single constant
>> speed motor).
>>
>> When I began with EME, I used improvised polar mounts, see a wooden
>> version:
>> http://lea.hamradio.si/~s57uuu/eme/dish1m1.jpg [1]
>> slightly improved version, works in snow, too:
>> http://lea.hamradio.si/~s57uuu/eme/sl5.jpg [2]
>>
>> But a serious polar mount is usually mechanically more challenging
>> to
>> build than an alt/az, so in the end, I ended with an alt/az.
>>
>> With an alt/az, without a computer, it is quite hard to do sideral
>> tracking.
>> A small computer like Raspberry, is powerful enough, and Python is
>> simple (I heard), with many useful libraries available, maybe even
>> ready-made tracking solutions.
>>
>> I am working on an "universal" solution, but as my projects go,
>> might
>> take a longer time to be finished.
>> Slides in Slovene language are here:
>> http://lea.hamradio.si/~s57uuu/s5/RIS/RIS2019/RIS2019.pdf [3]
>>> http://groups.google.com/group/sara-list?hl=en [4] [1]
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>>>
>>
> https://groups.google.com/d/msgid/sara-list/dbd5663d-fc76-4bb1-bba7-b8f2306ab3cbn%40googlegroups.com
>> [5]
>>> [2].
>>>
>>>
>>> Links:
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>>> [1] http://groups.google.com/group/sara-list?hl=en [4]
>>> [2]
>>>
>>
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>
>
> Links:
> ------
> [1] http://lea.hamradio.si/~s57uuu/eme/dish1m1.jpg
> [2] http://lea.hamradio.si/~s57uuu/eme/sl5.jpg
> [3] http://lea.hamradio.si/~s57uuu/s5/RIS/RIS2019/RIS2019.pdf
> [4] http://groups.google.com/group/sara-list?hl=en
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> [7]
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> [8] http://parac.eu
> [9]
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Joe McCauley

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Sep 12, 2022, 5:57:16 PM9/12/22
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Larry, I don't get time to read the SARA list stuff often sadly, but his caught my eye....


Lets assume you are using an arduino to control the mount.
Use a satellite dish actuator like this one on the dish elevation axis (though you may need one with a longer range) https://www.ebay.com/itm/383964600504
That has a reed switch in it that operates once per revolution, so you can count the pulses from it and interpret where the dish is elevated to. Set things up so that at 0 degrees (or whatever you want the minimum elevation to be, that the actuator is fully reteracted. There is a switch in there that stops the motor being driven further in if that makes sense. What I've done before is, to start by retracting the actuator and monitor the pulses from the switch. If I don't get any more pulses while the actuator is supposed to be retracting, then I infer that I'm at minimum elevation. Now I reverse the direction and count pulses until I reach the position I want. You could set this mechanically so that x switch pulses translated directly to y degrees of elevation and 2x pulses to 2y degrees etc.. I simply calibrated the thing using an accelerometer and stored a lookup table in the system so that I know how many counts corrospond to a given elevation (i.e. was not linear, but did not matter as the lookup table translated the total pulses to an angle and I interpolated the gaps). A better option is simply fit an accelerometer to the dish and readout the angle directly - easy to do with an arduino as well & the sensors are cheap (https://www.adafruit.com/product/163 its an analog output device, so you'll need to use arduino ADC to read it, don't use an I2C type accelerometer as you won't be able to read it over a long cable), do lots of averaging on the value you get and it will work nicely and you can get a direct elevation angle from this. The thing about this project is that your dish movements don't have to be fast. 

For the azimuth axis, you'll need to fit a rotary shaft encoder to the az axis to get the angular position of the az axis. There are 2 types of rotary encoder you can get. One is a counting type which can give you direction of motion and a pulse as it rotates. For this one you will have to have a home position for the dish where a switch is activated when you reach that position. This means to reach the home position, you have to drive in a particular direction. The resolution of the encoder is how many pulses you get per revolution of the shaft. Have a search for 'OMRON Incremental Rotary Encoder' on ebay, there are loads available, for a 1:1 gearing ratio between the sensor and the shaft, I'd get one that gives at least 1000 pulses per rev. There can be errors with gearing and backlash, but tracking in az, you will be driving only in one direction anyhow. So if your homing direction is the opposite to your tracking direction, there should be no problem unless your axis is sloppy and can move back and forth in the wind enough to give a pulse from the sensor. One way to minimise this being a problem would be to not count pulses unles the motor was being actively driven. Before selecting a new target, home both az and el.

The other type of shaft encoder is an absolute position encoder which gives a direct readout of the angle. These are more expensive, but much better. Relying on pulse counting is cheap, but if you lose power, you have to home the system again to know where you are. You could possibly also do azimuth angle sensing by gearing a potentiometer to the az axis, but this is not very robust and your travel would have to be limited (not really recommended).

Your control computer has to continuously calculate for your location the Alt-Az of your target and then feed that to the arduino controlling the mount. That only has to be done every few minutes. I don't know what size your dishes are, but the beamwidth is going to be relatively large I guess, so no need to overdo it on the update frequency.

As others have mentioned, Astropy does your calculations for you and can spit out an alt-az angle for any target. If you are using pulse counts to keep track of az and el, have the mount controller (arduino) relate the angles to pulse counts, all will be OK. You just need to keep track of the number of pulses. You will always be tracking in one direction in az, but in elevation you can be tracking up or down or both for a given observation so you'll need to bear that in mind if you are using the pulses generated by the elevation actuator. Finally it would be a good idea to have some indication if power to the arduino has cycled or the device has reset. This is important so your control computer knows this has happened.

I hope the above makes some sense. There is quite a bit to this, but its very doable. I've done a transit only (no az movement and no tracking necessary) interferometer using an arduino and satellite jacks for elevation. It worked well but was easier than what you are trying in the sense that I only had to elevate it once per day.

Joe

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Marcus D. Leech

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Sep 12, 2022, 6:39:05 PM9/12/22
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On 2022-09-12 17:57, Joe McCauley wrote:
Larry, I don't get time to read the SARA list stuff often sadly, but his caught my eye....

I was just thinking about Nate today.   He's since moved on to using somewhat-beefy slew bearings for azimuth, which I think
  he got surplus from eBay.

I'll point out that for some observing modes, you don't even need a driven azimuth--a "transit" mount only requires
  a driven elevation.


Jim Abshier

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Sep 13, 2022, 1:34:26 PM9/13/22
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Larry,

Another advantage of the polar mount is that it can track smoothly
through zenith. With an elevation-over-azimuth mount, the azimuth
changes rapidly when tracking near zenith. Tracking through zenith would
be a real challenge. At my location, Cygnus A transits very near zenith
and the few tracking mounts that I have ever used were all polar mounts.

Jim Abshier

b alex pettit jr

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Sep 13, 2022, 1:58:09 PM9/13/22
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As the antennas Larry plans to use are so small, an off-the-shelf  Polar/Equatorial mount would be an easy solution  vs building

The Dish 500 Antennas  are 22" Diameter... A small equatorial astronomical mount could handle, if they not too widely spaced,  a pair of these '500's nicely.

Inline image


Inline image


Alex Pettit KK4VB
=======================================================

Charles S Osborne K4CSO

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Sep 13, 2022, 3:37:45 PM9/13/22
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This isn't mine. Contact the person directly. Just saw it on QRZ.com. They posted it Tuesday 9/13 at 2:10pm.
 
 
Charles Osborne
 

Joe McCauley

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Sep 13, 2022, 5:32:50 PM9/13/22
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Those are small dishes all right! I paid little attention to the dish type as Dish 500 meant nothing to me. So where I come from the nearest equivalent type of dish easily available would be 60cm offset dishes and they are used for Ku band satellite TV reception. That being the case you could use a DiSEqC motor like this one https://www.ebay.com/itm/175390037265?hash=item28d60f9511:g:lEEAAOSw1h9jAXTj&amdata=enc%3AAQAHAAAAoEyWvKjJeQTPlskzwt1XjxfagriIuHqonbESg6Ijg7XLfMDRgjZgxrpjiPB3Bk3ly1HZ%2FJGKPmoSOB2qql5yFuMXLUE%2B5%2Fg6%2FySw%2FzvvzECpTGLIx2VTPqjzvACnrR%2F6XcnP4tBvkCEY%2F4idibLNu96Ic0fiHw6uGohlv8%2F8J%2BcQGOdNjEzaN8ow6VttjDMZzahiW9paZAaH27wrnK3oY3A%3D%7Ctkp%3ABk9SR7627onnYA
DiSEqC satellite RX stuff is common in Europe, no idea if you can easily get it in the USA, but guess you can get it online shipped to you.
Coupled with a dish actuator like the one I linked to yesterday for elevation control, you could get almost 180 degrees of azimuth control with one of these. That might be enough for your purposes. 

Now I bought 2 of these motors for my interferometer project, but did not really have time to incorporate these and it turned out that leaving it setup as a transit only setup was sufficient with variable elevation. Its a thing I'll get back to some day. These can drive 1.2m solid aluminum dishes which present a significant wind load, so these are actually quite capable drivers. They are controlled by modulating the power supply thereby encoding the control signals on the power supply (psu is nominally 13-18V DC usually, but check that). At the time I was playing with these I was working with PIC microcontrollers and had made a circuit to do the control. I work mostly with arduino stuff now (lots of cheap readily available boards). I'll bet there is a DiSEqC control library for arduino out there on the net. As I recall, the circuit was not overly complex but it was over 7 years ago & I may not have the details any more. Have a look on the net for a DiSEqC H-H motor control interface circuit, likely you can also buy a ready made control box. The DiSEqC commands are described in this zip https://de.eutelsat.com/files/PDF/DiSEqC-documentation.zip.

Out of interest what are you going to observe with these and at what frequency? The beam width will be large in any case due to the small dish size, that helps in that the accuracy requirments of your positioning wont be stringent, but you'd probably want the source to be filling the beam and would have to be a strong source.

Joe

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Joe McCauley

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Sep 13, 2022, 5:45:49 PM9/13/22
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And it turns out that Christain Monstein in Switzerland has built a DiSEqE motor controller since I worked on this last and here is a link. https://www.e-callisto.org/hardware/Diseqc/Doku%20Diseq.pdf. No point reinventing the wheel!

Joe

Larry Mayfield

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Sep 13, 2022, 7:17:36 PM9/13/22
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Joe, others,

I must have not explained my system being designed with my specific requirements. Yes, I can throw money at this project and  be done with it very quickly, but part of me is an engineer (actually Registered Professional Engineer, license 19119, Washington State). But part of me is in a learning phase as I know doodly squat regards RA.  So, this is part of my learning. The quickness I need is because I am pushing the envelope regards the mortality tables for my age group.   I have already decided on the use of off-set slider crank mechanisms for both the Alt and the Az  axle operations. I have already designed the crank arm and how it mounts to the dish mounting beam and it rotation system. I have taken that far enough with an excel spread sheet to define the linear stroke needed for a single degree for me to determine the rate of travel time for that 1 degree of change. I have two rotary encoders, both instantaneous versions to measure the number of counts traversed during movements.  I will build two encoder drive gears fro GT2 cogged timing belts with 300 teeth per revolution of the gear. With my 20 tooth encoder drive pulley , the 600 pulses pe recorder revolution the quadrature multipliers due to two phased encoder operation, plus the resolution gain with encoder drive ration  I will have 36000 counts per revolution of the alt axle.   That will give the capability for count numbers equating to 36 arc seconds of degree resolution. I am not chasing polar orbiting sats, nor equatorial geosats either . My sole operation is geared to listening to the newly found planets around some of the star systems.  The Az drive is virtually the same mechanism just the mechanical scale is a bit different.  I amusing an automotive front replaceable spindle hub as my lazy Susan bearing supporting the mast and remainder of the bits and pieces. I have two linear actuators that I will use, one for the Alt system and a larger one for the Az drive.  The Alt unit will be mounted rigidly to the vertical Mast and connect to a connecting rod pushing and pulling on the crank attached the dish mounting beam for those changes. The Az drive will similar but will be capable of doing a full revolution of 360 degrees with one simple change. The crank for the ax will connect to the hub internal spline for that rotation operation. And the rate of change for the systems will be matched to the ALT axis.  Corrections for the ALT axis drive rates will no doubt be required for different viewing elevation angles. I expect help from AstroPy for these ideas and coding.  I have the complete code for Stellarium as the basic code for running this particular system.

 

What I sometimes get excited and frustrated with is things like changing the field of view of a planet in ut system because as it rotates around our solar system its view on earth rotates causes OPTICAL telescopes to  need axis rotation to maintain photo quality. While I do not believe this is a requirement for radio signals that maybe just my dumbness.

 

Oh, before I forget, I do think that if I used a equatorial basic design with the offset slider mechanism that I could have a working system quite easily. But where is the fun I that? No t much learning needed but more expense with respect to the equatorial or ra drive system. I guess I could use the slider crank and linear actuator  with a hand set declination angle.

 

Anyway,  nuff blabber from me today. And probably tomorrow as well…

Larry

Pahrump, NV

 

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Joe McCauley
Sent: Tuesday, September 13, 2022 2:33 PM
To: sara...@googlegroups.com
Subject: Re: [SARA] Alt Az mount

 

Those are small dishes all right! I paid little attention to the dish type as Dish 500 meant nothing to me. So where I come from the nearest equivalent type of dish easily available would be 60cm offset dishes and they are used for Ku band satellite TV reception. That being the case you could use a DiSEqC motor like this one https://www.ebay.com/itm/175390037265?hash=item28d60f9511:g:lEEAAOSw1h9jAXTj&amdata=enc%3AAQAHAAAAoEyWvKjJeQTPlskzwt1XjxfagriIuHqonbESg6Ijg7XLfMDRgjZgxrpjiPB3Bk3ly1HZ%2FJGKPmoSOB2qql5yFuMXLUE%2B5%2Fg6%2FySw%2FzvvzECpTGLIx2VTPqjzvACnrR%2F6XcnP4tBvkCEY%2F4idibLNu96Ic0fiHw6uGohlv8%2F8J%2BcQGOdNjEzaN8ow6VttjDMZzahiW9paZAaH27wrnK3oY3A%3D%7Ctkp%3ABk9SR7627onnYA

image001.png
image002.png

Wayne Hilliard

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Sep 14, 2022, 5:12:08 AM9/14/22
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Larry,
Check out

This is a telescope control software system based on 3D printer boards and Arduino type microcontrollers. It supports both az-el as well as equatorial type mounts. It is open source and works very well. I'm considering a mount for a 10 foot dish and will use this in some manner  to control it. I've already converted a Celestron C8 fork mount optical telescope with it to a computer controlled telescope. It's extremely well documented for an open source type project and has a very active user group you can get help from. Really the problem is the same both with optical and radio telescope. All that should change is the size of the driver motors.

Cheers,
Wayne Hilliard

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Larry Mayfield

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Sep 14, 2022, 11:44:53 AM9/14/22
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Thanks! I will take a look and hopefully it does what I think I want to do, lol…

larry

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Wayne Hilliard
Sent: Wednesday, September 14, 2022 2:12 AM
To: sara...@googlegroups.com
Subject: Re: [SARA] Alt Az mount

 

Larry,

Joe McCauley

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Sep 15, 2022, 7:14:00 AM9/15/22
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Are you sure stepper motors are right for a radio astronomy dish? Stepper motors have relatively low torque capability compared to other motor types. They are great for positioning, but will loose steps if you try to drive them too fast or if to try to drive a heavy load. That makes them less useful for moving large loads I feel. You would have to have them very heavily geared to move the mass involved in any reasonably sized dish positioner (particularly accounting for wind). That would make the axis really slow.....

The type of motor used in 3D printers (certainly hobby/light pro ones) are NEMA 17 motors. These are pretty light weight indeed. I've used NEMA 23 motors (a bit more powerful than the 17s) with 3D printer hardware for a home built laser cutter, but I'm certainly not using the motors at their rated current as the drivers I have are not up to it. You will do better drive capability wise by using TMC2209 or better motor driver modules which are pin compatible with many 3D printer boards using plug in motor driver modules, but even then and using even more powerful stepper motors, you may well run into trouble with lost steps which means you lose position info. In principle you feed a stepper motor a given number of steps and that should be that, but its not always the case sadly.

I've not studied that telescope drive in the link you sent to see if he has position feedback on the mount RA and DEC axis (I certainly intend to as there is other stuff on that site that interests me). For an optical telescope, you'll get visual confirmation if you're on target or not (i.e. if you have lost steps). For a radio telescope where you might have to integrate for a while, its not so simple. So my personal opinion is that you still really should have axis position feedback meaning that the disadavntages of steppers for moving a radio astronomy dish are probably going to outweigh percieved advantages of cheap hardware etc.

Thats just my opinion & maybe someone will prove me wrong....

Joe



Larry Mayfield

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Sep 15, 2022, 8:58:23 AM9/15/22
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No stepper motors. Linear actuators. The garage guy used steppers, not me…

 

Larry

pahrump

Chad Gray

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Sep 15, 2022, 9:18:46 AM9/15/22
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Hey Joe, there are many successful uses of stepper motors on astronomy mounts.  If you are going to design a mount then make sure it is balanced so it can be moved with little effort. 

There are external drivers that can deliver the current if you need it.  Like you said the small stepstick drivers like the TMC2209 can only deliver so much.  There are also adapters if you want to take the stepstick footprint and output to an external driver. 

This is a well documented large scale conversion.  There were a few too many chefs in the kitchen on this conversion, but eventually it was all figured out.

Here is also a list of conversions of mostly commercially made mounts that developed dead electronics and people brought they back to life.

Chad


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Marcus D. Leech

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Sep 15, 2022, 9:34:28 AM9/15/22
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On 2022-09-15 09:05, Chad Gray wrote:
> Hey Joe, there are many successful uses of stepper motors on
> astronomy mounts.  If you are going to design a mount then make sure
> it is balanced so it can be moved with little effort.
I was involved in a 21cm interferometer project in the mid 1980s that
used steppers to drive a custom German Equatorial
  mount.  The two axes were based on rotary tables for milling
machines--basically poor man's slew drives.  We had to replace
  the ring gears inside them, substituting bronze for the cast-iron
that they came with.

The original code (not written by me) drove the RA stepper continuously
at a very low rate during tracking.  That caused
  the motors to overheat.  I changed the code to "sleep a bit, move a
bit" motion doctrine and they worked fine after that.
  Our stepper controller used a stepper chip driving a small bank of
MOSFETs as I recall.

Our secondary position feedback was via multi-turn precision
potentiometers, but I cannot recall what our primary
  feedback was.


Joe McCauley

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Sep 15, 2022, 10:45:39 AM9/15/22
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Chad, these are all optical telescope mounts though. I was referring to the advisability of using steppers as antenna positioners. There you surely have to take wind loading (particularly on a dish) into consideration as no ammount of balancing will work when the wind changes :).

I will say that Hopewell Ealing mount is an impressively large one though. The motors used look like double stack NEMA 23s (I think) and a scan through the Jan 2022 post indicated the drive is slow so as I said must be heavily geared. Its good enough for sky tracking though if you don't mind waiting while slewing to a target. It seems they got it going by throwing progressively larger stepper moters and drivers at the problem. Thats a long way from using a 3D printer board to control a telescope as was suggested before. 

At some stage I'll read through it all and see if they actually have position feedback from the telescope axes. I'm delighted to have found out about https://onstep.groups.io/ as I have a good quality Russian Netwonian scope here with a basic single speed eq mount. Might be an interesting project if I ever get time.

Joe

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Chad Gray

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Sep 15, 2022, 10:46:27 AM9/15/22
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Great re-use of rotary tables... I never thought of that one!  I would imagine they are based on worm/wheel gears just like most equatorial mounts.

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Chad Gray

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Sep 15, 2022, 10:59:07 AM9/15/22
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He Joe, do understand that the Ealing mount was not originally designed for stepper motors.  If you are starting from scratch all of these concerns can be dealt with.

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Joe McCauley

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Sep 15, 2022, 11:19:21 AM9/15/22
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Marcus, what size were the dish(es) involved? Did you have problems with loosing steps? Even if you did, you still had feedback on the axis I guess so at least you knew about it. You also ran into the other problem with steppers I never mentioned, they get hot when the windings are continuously energised. That also affects their torque performance if I recall correctly. Then you power them down to alleviate that problem and you're at the mercy of an external force moving things. Not the biggest issue if the system is geared though. Also you can short the windings to ensure the motor won't move with no power applied. Its also common to use a reduced drive current to hold the motor at a given position, but continuous motion as you say can be a problem.

'Our secondary position feedback was via multi-turn precision potentiometers, but I cannot recall what our primary feedback was.' What do you mean by primary/secondary position feedback?

Joe

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Marcus D. Leech

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Sep 15, 2022, 11:23:23 AM9/15/22
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On 2022-09-15 11:19, Joe McCauley wrote:
Marcus, what size were the dish(es) involved? Did you have problems with loosing steps? Even if you did, you still had feedback on the axis I guess so at least you knew about it. You also ran into the other problem with steppers I never mentioned, they get hot when the windings are continuously energised. That also affects their torque performance if I recall correctly. Then you power them down to alleviate that problem and you're at the mercy of an external force moving things. Not the biggest issue if the system is geared though. Also you can short the windings to ensure the motor won't move with no power applied. Its also common to use a reduced drive current to hold the motor at a given position, but continuous motion as you say can be a problem.
These were 3.8m dishes.



'Our secondary position feedback was via multi-turn precision potentiometers, but I cannot recall what our primary feedback was.' What do you mean by primary/secondary position feedback?
We had two ways of telling where the dish was--a potentiometer and some kind of absolute encoder as I recall.   Both of them
  on shafts that went through the middle of the rotary tables.

Rotary tables are based on a worm-gear drive, so you don't need the motors to hold position.


Joe McCauley

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Sep 15, 2022, 1:53:17 PM9/15/22
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Ah yes, I get that Chad.

Marcus mentioned the issue of stepper motors over heating while driving continuously. I wonder if they are having problems with that. Marcus dit stop start driving which is OK for an antenna given the relatively large beamwidths.... 

Marcus D. Leech

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Sep 15, 2022, 1:58:58 PM9/15/22
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On 2022-09-15 13:53, Joe McCauley wrote:
Ah yes, I get that Chad.

Marcus mentioned the issue of stepper motors over heating while driving continuously. I wonder if they are having problems with that. Marcus dit stop start driving which is OK for an antenna given the relatively large beamwidths....
Stepper motors are a kind of two-phase drive, where it "steps" by dropping power to one of the phases (that's my understanding).
  What this means is that at low speeds, one of those coils is drawing power all the time, and the thing is stationary, meaning
  no back-EMF to provide a reactive resistance to current flow.

Pretty much like a regular DC motor at stall....

The 12.8m dish we're dealing with used to use 7.5HP "torque/traction" motors, in which the two motors are running in
  opposition to each other, and you reduce drive on one of them to get net motion in the desired direction.  You can imagine
  that consumed a *LOT* of power and produced a lot of excess heat.


mike....@gmail.com

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Sep 15, 2022, 2:45:51 PM9/15/22
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The   old step motor "drivers" did not have all the features of the modern step motor drivers which include current limit , micro stepping  and current reduction when not moving.  

Those transmissions with step motors are on ebay.

Mike

Joe McCauley

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Sep 15, 2022, 3:18:06 PM9/15/22
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Mike, 

For sure modern drives have more bells and whistles though those won't deal with many of the issues discussed in the context of antenna mounts. I'm curious about that mount anyhow. Any details? I can't see them on that website you linked. There is a video showing his dish moving. I could be wrong for sure, but those ones at least don't look like steppers. Have you an ebay link?

On steppers & torque, there are 3 phase steppers available which pack more of a punch. If anyone in Europe has any interest, I have a bunch on NEAMA 23 3 phase steppers and also 3 phase driver circuits to suit for sale......

Thanks,

Joe

djl

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Sep 15, 2022, 3:29:38 PM9/15/22
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Re: dual motor drives:   The ALMA dishes are apparently driven with two opposing motors. I saw them on the dish elevation drive at the Atacama observatory; the motor housings could be seen (https://www.eso.org/public/products/virtualtours/chajnantor/).This is apparently how the extremely fine angular drive precision together with rapid response is obtained.  The heat can only help at the altitude of the observatory.

I was also lucky enough to see the Subaru telescope several years ago while it was under construction. There, the polar drive at least was a steel motor shaft directly bearing on a steel band.  Perhaps this was an adaptation of the Hewlett Packard drive for which a steel wheel with random blobs pinched the paper between it and a "rubber" wheel, leaving a track of "random" impressions. This proved better than the previous system of cogged paper and was significantly cheaper; it was bidirectional as well once the impressions had been made.  A similar scheme could possibly replace chain style drive?

Also, as a comment, I too have a problem with a drive system with no position feedback. A DC motor with an encoder and a counter system provides position feedback as well as drive.

Don

Thanks! I will take a look and hopefully it does what I think I want to do, lol...

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VOX: 406-626-4304

Marcus D. Leech

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Sep 15, 2022, 3:36:28 PM9/15/22
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On 2022-09-15 15:29, djl wrote:

Re: dual motor drives:   The ALMA dishes are apparently driven with two opposing motors. I saw them on the dish elevation drive at the Atacama observatory; the motor housings could be seen (https://www.eso.org/public/products/virtualtours/chajnantor/).This is apparently how the extremely fine angular drive precision together with rapid response is obtained.  The heat can only help at the altitude of the observatory.

That's the reason this NATO dish had a dual-drive system (actually, it was a redundant drive system--4 motors per axis and
  two gearboxes).  They were operating at 7.5GHz so needed very-fine position accuracy.    Shaft feedback was via one
  sel-syn per gearbox, and the absolute axis position was via 3-stage resolvers on each axis.

I was also lucky enough to see the Subaru telescope several years ago while it was under construction. There, the polar drive at least was a steel motor shaft directly bearing on a steel band.  Perhaps this was an adaptation of the Hewlett Packard drive for which a steel wheel with random blobs pinched the paper between it and a "rubber" wheel, leaving a track of "random" impressions. This proved better than the previous system of cogged paper and was significantly cheaper; it was bidirectional as well once the impressions had been made.  A similar scheme could possibly replace chain style drive?

Also, as a comment, I too have a problem with a drive system with no position feedback. A DC motor with an encoder and a counter system provides position feedback as well as drive.

Shaft encoders and the like only get you so far when you have a gear-train that will inevitably have some backlash, which is
  why absolute position encoders on the two axes are often essential for high-precision motion.


mike....@gmail.com

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Sep 15, 2022, 3:46:59 PM9/15/22
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Go to   https://jgeheniau.wixsite.com/radio-astronomy/copy-of-home-1
Click on GEAR
Third picture down  , two guys looking at the drives

Those are china gear boxes like

Search for NMRV 030, 040 , 050       NMRV050 has a 25mm output shaft that you can put a dual output shaft in (they supply for more money)

Marcus D. Leech

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Sep 15, 2022, 3:52:39 PM9/15/22
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On 2022-09-15 15:46, mike....@gmail.com wrote:
> Go to  https://jgeheniau.wixsite.com/radio-astronomy/copy-of-home-1
> Click on GEAR
> Third picture down  , two guys looking at the drives
>
> Those are china gear boxes like
> https://www.ebay.com/itm/265358939359?hash=item3dc8a014df:g:xZgAAOSwKQ9Z-YqH&amdata=enc%3AAQAHAAAAsPHIKBelLIu8OY1JIEUtomVkhAl5JZ5FRYdwCP4pZEsP8V0lbaqU0VsqW%2FZ3g3FuOFQZ5MXmh3ile7cqyEeGd%2BDUEFcIyFH2%2BJIRg0tgTsLsvwBf9UBUrPnug1bD7nhYeJZIASxDfV893rqi445PEBt8KaoMwA92H9gTCZq3foGBKKYqVqoTa94CnM8hlSpDFgrriK%2FttwcL2zO4WTl4nXcq5vk52AXxNUJxFBw%2F%2FiMY%7Ctkp%3ABk9SR6y626noYA
>
> Search for NMRV 030, 040 , 050       NMRV050 has a 25mm output shaft
> that you can put a dual output shaft in (they supply for more money)
I have something similar on the way from Amazon--without the motor.

In one of the photos it looks like they're driving the worm-gear reducer
box with a larger windshield-wiper motor.  Which is
  itself a worm-gear drive typically....



Joe McCauley

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Sep 15, 2022, 5:15:36 PM9/15/22
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I saw that image, but couldn't make out much. The video is a little clearer, but the motor looked like a DC or AC type to me. Might be a cover on a NEMA stepper motor of course, would make sense as its outside. I thought the dish was moving awfully fast for a stepper, but maybe the vid is running fast.

Thanks for the gear info. They look like worm gears, I could have a use for them myself! I sent Job Geheniau a message, hope he responds

Joe

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/10758d3e-2907-46f9-b1ff-e2a5c9e7b864n%40googlegroups.com.

Jack Lobingier

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Sep 19, 2022, 3:09:48 PM9/19/22
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Larry, here is an example program that uses Astropy to do the coordinate conversions between alt/az (Horizon) coordinates and Ra/Dec (EQ) and Galactic coordinates.  Please feel free to use any or all of it.

Jack

On Mon, Sep 12, 2022 at 9:09 AM Jack Lobingier <49j...@gmail.com> wrote:
It’s on YouTube.  

On Mon, Sep 12, 2022 at 8:43 AM Larry Mayfield <drm...@mayfco.com> wrote:

Jack, sorry, I do not have the handouts… where can I obtain them as a down load if you know?

 

Larry

 

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Jack Lobingier
Sent: Monday, September 12, 2022 3:16 AM
To: sara...@googlegroups.com
Subject: Re: [SARA] Alt Az mount

 

Yep, sorry about that.  I tried to attach my presentation from the last SARA Conference, but it was too big to send.  If you have the handouts from the Conference, mine is the one on a tracking and positioning system for alt/ax mounts.

 

On Mon, Sep 12, 2022 at 12:12 AM Larry Mayfield <drm...@mayfco.com> wrote:

Jack, what may be overkill? I see noting with ideas or directions. Were you to attach a link or document or?

larry

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Jack Lobingier
Sent: Sunday, September 11, 2022 8:16 PM
To: sara...@googlegroups.com
Subject: Re: [SARA] Alt Az mount

 

Larry, this maybe overkill for what you want, but it might give you some ideas.

 

Jack

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Horizon_to_EQ_and_Galactic.py

Larry Mayfield

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Sep 19, 2022, 8:08:49 PM9/19/22
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Jack,

I just finished using the video, that you indicated below, and my snip tool to make a copy of the slides you presented.  I saved it both as a word file (mucho bytes) and as a pdf (less than 3 MB with compression). But it has a problem so unable to send you a copy now but can break up the word file into smaller pieces and send it as chunks. Happy to do so.

 

Very nice presentation of the functions and general solution manner for the system. No “how to” and I can see that things like cabling, modules and wiring, etc. would be a very large task!

 

Also where is the example program you mention below for Astropy, see highlighted yellow.  I would be interested in that for sure. You mentioned in one post and maybe it was a chart comment that the code work for this was 1000 lines long. Can I entice you to send me that code? Copy it with word than make smaller page numbered packages and send it in bits and pieces? 1000 lines at 40 lines per page is just 25 pages total. I would buy you an RC Cola and moon pie if you would (it is an old Texas ( I am a native Texan) and South East thing, lol).

 

Right now, I am wading through some code for operating a system with Stellarium doing the heavy work. But, that code has flaws in it. Written in Python but there are missing loop brackets in places. I will call it to the attention of the writer, for sure.

 

And thank you forALL of the effort and work you put  into your system!! Massive.

 

Larry

Pahrump, NV

Jack Lobingier

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Sep 19, 2022, 8:27:01 PM9/19/22
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Larry, Astropy is a Python package that needs to be installed into a Linux environment.  I am using Ubuntu.  Once you have a computer with Linux installed and have added the Astropy package, just run the program that I attached to my last email.

Jack

Marcus D. Leech

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Sep 19, 2022, 8:31:16 PM9/19/22
to sara...@googlegroups.com
On 2022-09-19 20:08, Larry Mayfield wrote:

Jack,

I just finished using the video, that you indicated below, and my snip tool to make a copy of the slides you presented.  I saved it both as a word file (mucho bytes) and as a pdf (less than 3 MB with compression). But it has a problem so unable to send you a copy now but can break up the word file into smaller pieces and send it as chunks. Happy to do so.

 

Very nice presentation of the functions and general solution manner for the system. No “how to” and I can see that things like cabling, modules and wiring, etc. would be a very large task!

 

Also where is the example program you mention below for Astropy, see highlighted yellow.  I would be interested in that for sure. You mentioned in one post and maybe it was a chart comment that the code work for this was 1000 lines long. Can I entice you to send me that code? Copy it with word than make smaller page numbered packages and send it in bits and pieces? 1000 lines at 40 lines per page is just 25 pages total. I would buy you an RC Cola and moon pie if you would (it is an old Texas ( I am a native Texan) and South East thing, lol).

 

Right now, I am wading through some code for operating a system with Stellarium doing the heavy work. But, that code has flaws in it. Written in Python but there are missing loop brackets in places. I will call it to the attention of the writer, for sure.

Python doesn't use brackets.  It can take folks some time to get used to "whitespace is syntactically significant". 

I don't use AstroPy, but rather pyephem--it's older, but for simple things like "what's my local LMST" it's fine.


Larry Mayfield

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Sep 20, 2022, 12:11:17 AM9/20/22
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Jack, I didn’t get a program. Nothing attached.  

I have python 3.10 on my computer in windows. And Anaconda, has Astropy on it on my comuter. So I can make things work I think.  But no software code from you.

 

In any case tomorrow will be another day and another doctor, lol.

 

Off to sleepy time,

 

Larry

Pahrump

fasleitung3

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Sep 20, 2022, 2:46:45 AM9/20/22
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I would certainly second the view to use pyephem when it comes to coordinate transformation only.
pyephem does all you would need and it is much more compact than the very extensive astropy package. There is no functional difference, since the coordinate transformation in astropy is just pyephem integrated into astropy.
However, if you want/need more of the functionality of astropy and have it installed for that purpose, then of course this may be the way to go.
There is another caveat which I have with respect to using astropy in a live control environment: Every now and then (not very frequently) it downloads some updated data such as ephemeris which stalls the operation for a moment. This is not what you want when using it for a tracking mount.
At our site we are using pyephem for all our smaller dishes. For the 25-m dish we use pyephem and an even older package PyTPM for purely historical reasons. I do not recommend PyTPM for any new development.
Best regards,
Wolfgang

Jack Lobingier

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Sep 20, 2022, 8:28:47 AM9/20/22
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Larry, look at the bottom of the message string for the program.  I don’t know why it put it there.  If you don’t find it let me know and I will resend it directly to you.  Both Marcus and Wolfgang feel that pyephem is a better solution, so use that if you like.

Jack

Jim Abshier

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Sep 20, 2022, 11:53:17 AM9/20/22
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One of the reasons why I never considered learning python.

Jim Abshier

Marcus D. Leech

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Sep 20, 2022, 11:58:32 AM9/20/22
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On 2022-09-20 11:53, Jim Abshier wrote:
> One of the reasons why I never considered learning python.
It was a profound irritant when I first (reluctantly) learned Python in
2004.  But
  once you get over that, and use a "smart" editor that understands the
rules,
  then you can focus on how useful and expressive Python is.

This coming from a "I will be a C programmer until I'm 100" kind of guy.

A goodly portion of scientific data processing is done with Python these
days--both
  because of how expressive it is, and because it has well-integrated
scientific libraries
  like scipy and numpy and matplotlib, etc.

Larry Mayfield

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Sep 21, 2022, 11:28:55 AM9/21/22
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Marcus,and everybody else,  yes, I did get mixed up a smidge with brackets. Was working with Arduino IDE code and it is basically “C” and it does use the curly brackets. And I was tangled up in Python as well, micro python now works with the arduino microcontrollers I am told. I have the Stellarium code and it is in Arduino code application and the version from Instructables has code flaws with the brackets in a few places.  I even have one in python code I snagged yesterday, and it is very short on comments as to what the code is doing as well. So I am trying to make it better and readable. And error free. If Possible.  Why? Well, if I am having issues with trying to make ALT AZ work because of a lack of information then perhaps many other noobs are having the same issues?

 

I will say that the brain trust of the knowledgeable list members is awesome and generally all are very helpful, however, most are  short and incomplete at times.  I keep asking for information and getting some answers, but it seems to me that the SARA org could take a hand in setting up a committee to design and build both equatorial and alt az telescope mounts with drive and control systems that are as simple as they can be and with full tracking controls would be a reasonable thing to do. Might get a lot of new members who are less frustrated? At least one, lol, me.  The systems could have everything needed for a new wannabe to build and operate their system. And FREE of commercial interests. Schematics, part numbers, drive part numbers … in short everything. Conception to fulfilment with a working system.  Just in the last few days I have found several different papers and operating systems for the above. But not a SARA org unit that is recommended. Kinda Sad.  I would join in a minute, but quite frankly, at my age, and with mortality statistics not on my side, ie., far fewer days in front of me than behind me, that I will cease to be in a year or two.  I am currently struggling with the idea and knowledge that I probably will not be able to finish anything I have started because the lack of simple how to’s, in complete detail, is just not locatable by me.  But I will keep on for at least a while.

 

I apologize to all the other members for my lengthy diatribes but I am frustrated by my inability to get what I want done becasu e of a lack of detailed information.  

 

So all yall excuse me please, I will try my best not to be a pin in the batookus.  Signing off for now.

 

Larry

Pahrump

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Marcus D. Leech
Sent: Monday, September 19, 2022 5:31 PM
To: sara...@googlegroups.com
Subject: Re: [SARA] Alt Az mount

 

Big snip….

 

Python doesn't use brackets.  It can take folks some time to get used to "whitespace is syntactically significant". 

I don't use AstroPy, but rather pyephem--it's older, but for simple things like "what's my local LMST" it's fine.



 

And thank you forALL of the effort and work you put  into your system!! Massive.

 

Larry

Pahrump, NV

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Jack Lobingier
Sent: Monday, September 19, 2022 12:10 PM
To: sara...@googlegroups.com
Subject: Re: [SARA] Alt Az mount

 

Larry, here is an example program that uses Astropy to do the coordinate conversions between alt/az (Horizon) coordinates and Ra/Dec (EQ) and Galactic coordinates.  Please feel free to use any or all of it.

 

Jack

 

On Mon, Sep 12, 2022 at 9:09 AM Jack Lobingier <49j...@gmail.com> wrote:

It’s on YouTube.  

On Mon, Sep 12, 2022 at 8:43 AM Larry Mayfield <drm...@mayfco.com> wrote:

Jack, sorry, I do not have the handouts… where can I obtain them as a down load if you know?

 

Larry

 

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Jack Lobingier
Sent: Monday, September 12, 2022 3:16 AM
To: sara...@googlegroups.com
Subject: Re: [SARA] Alt Az mount

 

Yep, sorry about that.  I tried to attach my presentation from the last SARA Conference, but it was too big to send.  If you have the handouts from the Conference, mine is the one on a tracking and positioning system for alt/ax mounts.

On Mon, Sep 12, 2022 at 12:12 AM Larry Mayfield <drm...@mayfco.com> wrote:

Jack, what may be overkill? I see nothing with ideas or directions. Were you to attach a link or document or?

Lamar Owen

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Oct 12, 2022, 2:27:50 PM10/12/22
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On 9/20/22 02:46, 'fasleitung3' via Society of Amateur Radio Astronomers
wrote:
> I would certainly second the view to use pyephem when it comes to
> coordinate transformation only.
> pyephem does all you would need and it is much more compact than the
> very extensive astropy package.
Pyephem has been deprecated in favor of Skyfield.  Same author, Brandon
Rhodes.  https://rhodesmill.org/skyfield/ (also a quote from the
https://rhodesmill.org/pyephem home page: "The Skyfield astronomy
library <https://rhodesmill.org/skyfield/> should be preferred over
PyEphem for new projects. Its modern design encourages better Python
code, and uses NumPy to accelerate its calculations.")

For our X-Y antennas here, it gets more complicated.  Even though the
mounts are X-Y, the DFM Engineering software does RA/DEC to and from X-Y
conversions.  However, I actually ended up driving the antenna in
HA/DEC, and used AltAz/HADEC conversion routines in Python ported from
the NASA IDL library.  For a treatment of coordinate conversions between
X-Y, HA/DEC, AltAz, and ECEF cartesian, NASA's "Mathematical
Relationships of the MFOD Antenna Axes" is a dense but thorough
treatment of the subject ( https://ntrs.nasa.gov/citations/19670030005
). (The 85-foot antenna there, the Apollo USB made by Blaw-Knox, is
rotated 90 degrees with respect to the axes of our two 85-foot antennas,
which follow the equations and graphs of the 30-foot X-Y antennas).

If you're not familiar with the X-Y mount (or Alt-Alt mount) here's a
link to a timelapse video of a day's run with one of our two antennas:
https://nebula.pari.edu/index.php/s/kWxb7B90fYpfCbn

As to Python syntax, you know, I always indented my C code anyway;
braces (curly brackets, or {}; brackets are []) are, in my opinion at
least, redundant anyway.  I know people can get possessive about their
indentation style.... but Python brings so much to the table that the
tradeoff is, in my opinion at least, very much worth it.
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