Re: GOTO accuracy for stars vs DSOs

Joe Zeglinski

    Have you checked the attachment of the dovetail to your mount’s head? Maybe one of  the screws isn’t tightened  squarely, or tightly enough, so the entire scope, whichever one you have mounted at the time,  and the AP saddle rock just a bit, to the other extreme after a meridian flip. That would result in a major shift and loss of your target from the original centered FOV.
    If the dovetail is in fact tight,  solidly and squarely bolted on, then maybe you may have a minor defect in this particular production run of the mount – Again, as evidenced by a slight rocking of the RA axis.
You can check this at PARK-3 by rocking the end of the end of the counterweight bar up & down, to see if there is any play, or even a minor  separation crack between the DEC and the RA,  as you rock the axle.
    Tony,  (his AP-GTO Group handle is:  “Harley Davidson”). had that problem which he demonstrated in his video, last Labour Day.
See his group post:
“[ap-gto] 1600GTO mount play in RA axis”  dated: (06/09/2018)
Tony’s problem demo video
    Even though his is a different model from your Mach-1, perhaps yours has the same unique production/assembly problem. Tony had to return the mount for an internal mount part replacement, not something an owner can do himself. It works fine now.
Good luck. Hope this helps,

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