I hope this is not "inappropriate" for posting to the group, but here it goes:

Raphael, have you considered perhaps a different type of setup for tracking the ISS? For example, there are Astro-Physics mounts out there that when paired up with software like APCC [Astro-Physics Command Center] it helps a lot when tracking satellites, ISS, Hubble Space Telescope "HST", etc. Not sure, but I think also the Software Bisque Paramounts can be programmed to do the same thing <The Sky X software, T-Point, etc>. I figure the extreme CNC precision machining that goes into these mounts would make the task/goal easier (however, with a smaller aperture scope).

I mention this because many astronomers have multiple setups (mounts: alt-az & German Equatorials, push to or electronic drive systems, solar or nighttime telescopes, etc)

I know not everyone is into German Equatorial Mounts "GEM's". They are a different animal, or beast, versus a big dob light bucket. I mentioned it here as "just a thought" or "friendly suggestion".

Perfectly understandable if your preference is to stay committed to your project.?

I hope this doesn't get me banned/ kicked out of the group. I don't think it hurts or is harmful to look at alternative means of doing things.?

Fernando

Gary,

"My suspicion is you might be asking too much from such a large scope"

Yes, for sure !!

In fact trying to get the maximum from my scope is really a target in itself.

With my small field of view, it is necessary to have pointing and ratio as accurates as possible to follow as perfectly as possible ISS.

You know it's like Gabriel Wiklund that is optimising again and again the autoguiding with wonderfull results at the end. Great to obtain the very best from a scope !

I want to go as deep as possible for optimising the scope. Maybe I will be blocked by mechanical problem, but at least I want to go to this point.

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I will continue using drifting test, either by tweaking the ratio 5 by 5 as you suggest, either using the "track improvment" method but with the correction I was mentionning in my initial message for the alt correction. Even if I'm wrong with the correction I mentioned in my initial message, it will just take more iterations to achieve the best ratio I could achieve before mechanicalo limitation.

I will post the results after the iterations

Thanks for your help

Rapha?l

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Dear Gary,

I did it already one and corrected ratio. But there is still a remaining of correction of ratio needed.?

I mean yesterday night, the scope was pointing accurately because I had just calculated the IE of TPAS (with other persistant terms already computed from previous test)so I had a computed TPAS leading to RMS of 6'. OK

Then I centered a star and after 35 min it was 20' offcenter (0.33°). Frankly this is OK for visual follow up but still not accurate enough to follow ISS that move 200 times quicker than sideral.

?

But I?can't I achieve anymore the "Simple Track Improvements Test" because :

In the "Simple Track Improvements Test" it is said :? ?

"Push the GOTO – it will start to move – now watch carefully the GUIDE value for this axis (left for AZ, right for
ALT). The scope will move a distance and then come to a stop. It will will then quickly pick up and start moving
again. You need to get the GUIDE value when it first stops"

The problem is since I'm already close to perfect ratio I can't notice any stop even if I put 170° instead of 100° in the procedure.

Maybe this is because my scope is massive, so I need to put? a 5 seconds deceleration => could this make it more difficult to notice the "stop" if it occurs during the deceleration ? I don't know... but I can't notice any stop.

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So this is why I wanted then to use? the "track improvment" method described in the Sercocat quick V3 file since this one is unsensitive to deceleration.

But then I have the calculation issue I indicated in my first message

I hope this clarify my original question

Regards

Rapha?l

Dear all,

I have used servocat+AN to follow ISS.

As ISS is moving at high speed you have to have have very good ratio adjustment (and also good pointing to have the maths done at good location => I implemented a TPAS)

To improve accuracy of tracking I started to improve ratio using the "track improvment" method described in the Sercocat quick V3 file.

To adjust Az ratio, it describes to use a star located at south.

I understand because at south it's a pure Az movement, no alt movement.

?

Then for Alt ratio, it describes to use a star located at east.

For ex you strack an object for 1/2 hour, the sky moved 7.5° (=360/24/2)and you divide your offset by this 7.5° value to calculate a correction factor of your Alt ratio.

What I don't understand is that for a star located at east, it's not a pure Alt movement so I don't understand why you divide your offset by 7.5°?

For example I live at 45° latitude.

In this case the star move only sin(45)*7.5= 5.3 in Alt (and 5.3 in Az).

After 1/2h let say I see in AN an offset for the star of 0.1° in Az and 0.2° in alt => I would have divided the alt offset 0.2 by 5.3 to get the correction ratio, not 0.2/7.5?

I'm certainly wrong, but could someone explain my mistake ?

Regards

Rapha?l

Mickey,?

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I'm not saying it makes no difference - I am saying it isn't going to account for a 5° error!?

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g.

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Actually with the Nexus it can make a difference. This may not be the problem but it can make a difference.

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Mickey

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On Apr 22, 2025, at 12:56?PM, K9RX - Gary via groups.io <amateurK9RX@...> wrote:

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The 2 stars used should not cause an issue in pointing of that degree nor cause it to be off on one of those stars (when returned to it). The quality of the alignment - whether the stars were the right stars (i.e. you were on the ones you claimed) could make a difference.?

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Generally with that much difference I'd suggest you are seeing slippage in one of the encoders. Generally the ALT is the culprit. Make sure the ALT encoder arm is not pushing up or down on the encoder shaft or twisting it.?

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g.

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------ Original Message ------

From "Mickey Huffman via groups.io" <finman42@...>

To [email protected]

Date 4/22/2025 12:29:47 PM

Subject Re: [ServoCAT] servocat and nexus dsc pro

?

Hello Frank, what 2 stars are you using for your 2 star alignment?

?

Mickey

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On Apr 22, 2025, at 12:16?PM, fwillburn <frank@...> wrote:

?

I have the jumpers switched and the nexus dsc pro is now communicating. I did a two star alignment and it pointed good to the first five targets and then on the sixth target it was off by about 5 degrees this is the order of the targets M51-m81-m82-albireo-m81 and then when i whent back to albireo it was off about 5 degrees. I have double checked all the settings. Let me know what you think.

Thanks

Frank? ??

Actually with the Nexus it can make a difference. This may not be the problem but it can make a difference.

Mickey

On Apr 22, 2025, at 12:56?PM, K9RX - Gary via groups.io <amateurK9RX@...> wrote:

?

The 2 stars used should not cause an issue in pointing of that degree nor cause it to be off on one of those stars (when returned to it). The quality of the alignment - whether the stars were the right stars (i.e. you were on the ones you claimed) could make a difference.?

Generally with that much difference I'd suggest you are seeing slippage in one of the encoders. Generally the ALT is the culprit. Make sure the ALT encoder arm is not pushing up or down on the encoder shaft or twisting it.?

g.

------ Original Message ------

From "Mickey Huffman via groups.io" <finman42@...>

To [email protected]

Date 4/22/2025 12:29:47 PM

Subject Re: [ServoCAT] servocat and nexus dsc pro

Hello Frank, what 2 stars are you using for your 2 star alignment?

Mickey

On Apr 22, 2025, at 12:16?PM, fwillburn <frank@...> wrote:

?

I have the jumpers switched and the nexus dsc pro is now communicating. I did a two star alignment and it pointed good to the first five targets and then on the sixth target it was off by about 5 degrees this is the order of the targets M51-m81-m82-albireo-m81 and then when i whent back to albireo it was off about 5 degrees. I have double checked all the settings. Let me know what you think.

Thanks

Frank? ??

Hello Frank, what 2 stars are you using for your 2 star alignment?

Mickey

On Apr 22, 2025, at 12:16?PM, fwillburn <frank@...> wrote:

?

I have the jumpers switched and the nexus dsc pro is now communicating. I did a two star alignment and it pointed good to the first five targets and then on the sixth target it was off by about 5 degrees this is the order of the targets M51-m81-m82-albireo-m81 and then when i whent back to albireo it was off about 5 degrees. I have double checked all the settings. Let me know what you think.

Thanks

Frank? ??