Guiding a Meade LX50 through the ST4 port

[Piergiorgio Licciardello]

Hi everybody,

Is there anyone who can suggest me the right setup for a Meade LX50.

Considering that it’s a pre-autostar model, there aren’t configuration options on telescopi side so all the work should be done on SW side.

I’ve tried to connect it to a ZWO ASI 224mc and the mount get connected but the calibration process fails because after some steps on East-West calibraton, the mount slews, probably responding in a bad way to the com and, and the star is lost.

I tried many times and the step number may change but the final result is always the same.

Any suggestion or procedure i can follow to better analyze where the problem may be?

Thank you very much in advance 

Regards

Piergiorgio 

[Aris Pope]

Hope this helps, i know it's for an LXD75 but should be similar.

https://www.cloudynights.com/topic/592147-autoguiding-the-lxd75-would-the-meade-apm-07509-work/

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[wave...@talktalk.net]

Hello Piergiorgio, I think you'll find that guiding an LX50 for long exposure AP will be exceedingly difficult. The ST4 system has serious limitations, not least being the need to re-calibrate for each target area of the sky. Some Meade owners will tell you not to even try, but for those that do, this thread has some good advice specifically on LX50 guiding. https://www.cloudynights.com/topic/715488-meade-lx-50-autoguiding/

Good luck,

0 Jack

[wave...@talktalk.net]

Piergiorgio, as an addendum to my post above, I'd also suggest using the latest Meade scopes driver being developed by Colin Dawson. Also ensure you have the latest ASCOM platform installed.

You'll find Colin Dawson's  Meade Generic (ASCOM) driver here: https://bitbucket.org/cjdskunkworks/meadeautostar497/wiki/Home

- Jack

[Piergiorgio Licciardello]

Thank you very much for the informations.

About the ASCOM drivers I only have a doubt.

The mount is connected to the PC via the ST4 port of the guiding camera so in PHD2 set up is identified as an “on camera” mount.

Does the ASCOM driver is used in a configuration like this?

Best Regards

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[wave...@talktalk.net]

Piergiorgio, you asked:

The mount is connected to the PC via the ST4 port of the guiding camera so in PHD2 set up is identified as an “on camera” mount.

Does the ASCOM driver is used in a configuration like this?

Ah, so the connections are: [pc/usb to camera/usb] and [camera ST4 to mount/CCD port].

The LX50 doesn't have a separate serial port, so no I don't think you can use the Meade Generic ASCOM driver.

As I understand it from the User Guide, the Aux Mount selection should be set to 'Ask for Coordinates'.

Before you attempt guiding, ensure all the communications work by using the Star Cross Test. Then run a Calibration at Dec0 and your meridian. Follow any warnings to get a good calibration. Then run the Guiding Assistant for 15-20 minutes to obtain a Baseline Guiding assessment. Submit the resulting GuideLog here and ask the experts to advise on how it looks and what you need to do to obtain best guiding.

- Jack

[Piergiorgio Licciardello]

Ok, thanks

I’ll try this way and see what happens

Regards

Piergiorgio

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[Piergiorgio Licciardello]

Well…I tried the test you suggested…and the result was definitely bad.

The star cross test returned a shape that has nothing to do with a cross and the telescope didn’t return in the starting position. 

At the end of the process the star was out of the field of the main camera.

The worse result seems to me in DEC axis where the star was totally shifted.

I tried the calibration at DEC 0 and I haven’t been able to complete.

The RA calibration returned a warning about limited movement toward east.

Indeed there has been a strange behavior of the mount.

The step on west proceeded in a good way but then, when the mount invert the direction there were a lot of shifts the opposite direction. Indeed in response to a pulse aiming to east, the mount moved to east and then slewed back to west. This means that, at the end of the calibration steps, PHD2 returned a warning on limited star movement (clearly due to the “return movements” of the mount.

The calibration on DEC failed immediately. It starts with a “backlash” operation and the telescope slewed away loosing completely the star. I’ve tried more than once with the same result. The response to the command was too high.

I attach the logs but I’m afraid they cannot help that much.

Probably the mount is not good for guiding…

Piergiorgio

[wave...@talktalk.net]

Hello Piergiorgio, From what I've read, the LX50  isn't the best mount out there for sure.

From what little I see in the logs, PHD2 doesn't know what the mount's guide speed is, so that's a no-go anyway.

So, I think it's worth installing the Meade Generic (ASCOM) driver as I noted earlier. That contains the guide speed data. Then, in the Aux Mount setting, try selecting Meade Generic (ASCOM) driver, that may be what's missing in the communication.

I hope one of the PHD2 experts will comment on your problem. I think they will quickly see what's wrong.

- Jack

[mj.w...@gmail.com]

Hi Jack

You're contradicting yourself.

Piergiorgio can't use the ASCOM Generic Driver because, as you said, the mount doesn't have an  RS232 port.

 Hi Piergiorgio

The Calibration settings in the GuideLog look wrong, did you use the Wizard in the PHD2 Equipment Profile ?

Calibration Step = 6944 ms, 

Looking at how far the mount moved in the Cal I'd guess that's 6 or 7 times too large.

 Calibration Distance = 108 px,

That should default to 25 px, did you alter it ?

Michael

Wiltshire UK

[Piergiorgio Licciardello]

Hi, 

The calibration step was first set automatically to 6944ms, I guess as a result of a calculation based on camera and focal length of the guide telescope.

I first tried with that amount and immediately, when changing from west to east, the mount slewed away a lot, completely loosing the star

Then I tried to reduce the step (600, 1000, 2000, 3000) to see if something changed and, indeed the lower is the value, the less the mount slews away when changing direction. Keeping a lower value, although with some warnings, allowed to complete the RA calibration

I didn’t change the distance, 108 was the result of the wizard .

So it seems that both values are too big?

1000ms and 25px may work well?

Best Regards

Piergiorgio

PS: I confirm that I don’t have a RS-232 or AUX port on the LX50. The only connection available is the ST-4 port, that is connected to the guide camera. I can specify an “external mount” during the configuration but, then, when requested to connect the devices, that mount cannot be connected as there’s no serial port to specify for the connection.

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[Brian Valente]

Hi Piergiorgio

What is your telescope focal length?

my guess is you entered the diameter and not focal length into the setting

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Brian Valente

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[Piergiorgio Licciardello]

The focal length of the telescope is 2000 (or 1280, depending on the use of reducer or not) but I’ve entered the focal length of the guide telescope (50 mm F=180).

The tooltip on the field (at least in the Italian translated version) indicate that value to be inserted and not the focal length of the main telescope.

The right value there should have been 2000 and the translation is wrong?

Best Regards

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[wave...@talktalk.net]

Hello Michael, you said:

You're contradicting yourself.

Piergiorgio can't use the ASCOM Generic Driver because, as you said, the mount doesn't have an  RS232 port.

Yea, I was hoping the mount guide speed and coordinates could be picked up via the ASCOM driver under the Aux Mount selector. Reading page 10 of the PHD2 manual put that into my head.

I think the bottom line is the LX50 just wasn't built for guiding.

- Jack

[Piergiorgio Licciardello]

Hi 

"I think the bottom line is the LX50 just wasn't built for guiding.”

Unfortunately it seems so.

The annoying thing is that the mount has a specific port “Autoguide” that is an ST4 port.

I wonder why this should not work and, if so, why Meade added a port not supposed to work. Only to have customers complaining? 

Anyway really thanks a lot to everyone for you attempts to find the error and a possible solution 

Best Regards

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[Brian Valente]

You enter the value of your guidescope focal length

What did you enter for your information in the calculations dialog box?

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[Piergiorgio Licciardello]

This is what appeared after the profile creation with the wizard 

The only parameter I’ve entered was the focal length. 180.

All the other where defaults, automatic calculations or camera specifications, like the pixel dimension

Il giorno 9 feb 2022, alle ore 16:35, Brian Valente <bval...@gmail.com> ha scritto:

You enter the value of your guidescope focal length

What did you enter for your information in the calculations dialog box?

<image.png>

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[Brian Valente]

your calibration distance is far too high. it should be more like 25 pixels

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[mj.w...@gmail.com]

Hi Piergiorgio

A quick look at LX50 images in Google, I only found one that had a guidescope:

http://www.spacegazer.com/index.asp?pageid=97146

He mentions a "Dec Fix Kit"  to make Dec a better match to the RA drive.

Hi Brian

Many years since I've done the Wizard, so for my edification:

Does the "Calibration distance, px" in fact default to 25 px ?

And does it alter based on the inputs to the Wizard ?

I've never seen a different figure in logs.

Michael

Wiltshire UK

[Piergiorgio Licciardello]

In a way or another I’ve been able to complete the calibration with warnings on east pulse and with some struggle and the system is guiding. The graph is horrible but and the polar alignment has an very high error but the system is guiding and trying to keep the star in the cross.

Surely for Dec what I had to do was to reduce dramatically the maximum impulse from the 2500 to 100 (and probably it’s still to high) and i’ve applied the suggestions of guide assistant.

Perhaps some additional tune up can be possible (together with a better polar alignment).

Thank you all for the support that allowed to arrive to this point

Inviato da iPhone

Il giorno 9 feb 2022, alle ore 16:35, Brian Valente <bval...@gmail.com> ha scritto:



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