SharpCap Plate Solve problem

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Posts: 23
Joined: Fri Jan 12, 2018 6:21 am

SharpCap Plate Solve problem

Post by stubblejumper » Tue Dec 04, 2018 8:41 am

I don't know if this is an SCap issue or my setup. I have used SCap's Plate Solve function for two nights in a row. SCap connected to ASPS and came up with coordinates of where my lens was pointing both nights. But it doesn't appear to update my mount as per the settings I selected because the handset values didn't change. Once the plate solve was successful, I tried, as per SCap instructions to get my planetarium program to slew to Schedar once again. In the first run I used Cartes du Ciel. After the meridian flip I used Starry Nights v6. In both cases, the mount did not move.

Am I doing something wrong or is there a connectivity problem between SCap Plate Solve and my mount?

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Re: SharpCap Plate Solve problem

Post by stubblejumper » Tue Dec 04, 2018 5:47 pm

Further information. I just learned that iOptron uses JNOW, not J2000 for epoch (forgive me if that is not the correct term!). I can select JNOW in Cartes du Ciel and perhaps Starry Nights, which are the two planetarium programs I've tried. But it doesn't seem possible that it would resolve why SCap's plate solve is not adjusting my CEM25P's position. However, in one run SCap did move my mount (had that option selected). However the move didn't get the target star, Schedar, anywhere near the center of the FOV. I was capturing IC11/NGC281 (Pacman) and it's right beside Schedar. I will hopefully be able to do more captures tonight. At 49N, sunset is around 4:15PM and a nice long period of darkness is great.

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Re: SharpCap Plate Solve problem

Post by BlackWikkett » Wed Dec 05, 2018 4:53 pm


I see you have two threads going about plate solving.

It sounds like you have plate solving working since it's able to capture the frame, solve and slew the mount. Your problem is that the corrected slew is off by " x " measure. I've seen this before and found this difference due to one the the items in the change of plate solving not using the same epoch as the mount. iOptron uses JNOW so your first step is to make sure your plate solver is using JNOW.

This isn't really a SharpCap issue since SC is capturing the image sending it to the solver and the solver is solving and sending the solved coordinates to the SC which then instructs the mount to move. All this seems to be working in your case. I think you'll find you get the plate solver, planetarium and mount on JNOW you'll be good to go.

Good Luck! -Wikkett

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Re: SharpCap Plate Solve problem

Post by admin » Thu Dec 06, 2018 4:45 pm


Wikket is likely correct that the issue is a coordinate system mismatch. The plate solvers that SharpCap uses all report coordinates in J 2000. Ascom mounts vary as to which coordinate system they use and they should report their coordinate system so that SharpCap can tell.

Code: Select all

  public enum EquatorialCoordinateType
    equOther = 0,
    [Obsolete("Please use equTopocentric instead. (See Astronomical Coordinates page in Developer's Help for further information)")] equLocalTopocentric = 1,
    equTopocentric = 1,
    equJ2000 = 2,
    equJ2050 = 3,
    equB1950 = 4,
if the mount reports one of the topocentric coordinate systems then SharpCap assumes it is running in J now and will perform a conversion from J 2000 to J now before sending the sync coordinates to the mount.

If however you're mounts does not correctly report its coordinate system then SharpCap wouldn't know to perform the conversion, which may be the problem that you are having.

Hope this helps, Robin

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