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Slew rate does not make sense

Stefan Berg Nighttime Imaging 'N' Astronomy (N.I.N.A. / NINA) Sky-Watcher EQ-AL55i PRO Go-To Sky-Watcher SynScan Pro Help Needed
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Christoph B avatar
Christoph B avatar

Hi,

I have a problem where NINA (or possibly SynScan Pro or the mount) is slewing way faster in the RA axis than it thinks it is. This leads to the mount overshooting substantially and I have no idea how to fix this. The following is what I can see:

  • Point at any point in the sky

  • Do a plate solve in NINA and sync to the mount

  • Slew the mount along the RA axis for enough time to expect a substantial difference (say an hour)

  • Note the RA value reported by NINA

  • Plate Solve again, not the discrepancy

For example if I slew for an hour or two, NINA will only think there were a few minutes difference. As a result, when I slew to any real target, NINA will move to a completely wrong location

I have the following setup:

  • NINA on a Windows PC

  • Skywatcher EQ-AL55i controlled via USB cable by the SynScan Pro App on the same PC

  • ASCOM driver for the SynScan App installed.

  • Everything done after being polar aligned using TPPA.

I have no idea how to fix this. I once got the system to work but not this happens every time.

Interestingly, tracking works perfectly fine. If I just expose on a random location in the sky, I do not get star trails. It is only during slewing that I run into problems.

Any help is appreciated.

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Tony Gondola avatar
Tony Gondola avatar

I don’t use SynScan but I do have a SkyWatcher mount. I use Green Swamp Server via USB for my mount control interface, commanded by NINA and I’ve never had a problem with that configuration.

Short of changing out software, how are you manually slewing the mount, with the hand box?

If you power the mount up in park, connect in NINA, command unpark in NINA, Have NINA slew to and solve your selected object, the select another object and do another slew and solve, does all that work?

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Christoph B avatar
Christoph B avatar

Thank you for the response. I have not tried Green Swamp Server, so maybe that is what I should do.

As for your other questions: I always mean slewing via NINA using either the direction controls available in NINA or the sky atlas slew function.

I currently cannot slew to any specific object due to my issues. But if I plate solve, slew somewhere else, and plate solve again, the second solution is completely off in comparison to where the scope believes it is looking.

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Tony Gondola avatar
Tony Gondola avatar

Giving GSS a try might be your best bet.

Christoph B avatar
Christoph B avatar

Thank you again. I had a surprise night of good weather and could try this out. I guess SynScan cannot take all alignment information from NINA or something like that. Using GSS worked like a charm.

Tony Gondola avatar
Tony Gondola avatar

excellent news!

Gamaholjad avatar
Gamaholjad avatar
Greenswamp  GSS for the win. Nina works well with it never had a problem.