PI doesn't read the correct focal length from the FITS header

No. By deleting nonsense from the headers you are just making them look the way that the ASIAir app should have written them in the first place.
But I agree "fv" is a tedious pain to use. I assume "fv" stands for "FITS viewer" - it has absolutely nothing to do with me ("fv" = fred vanner)! Anyone who writes an app or script to batch correct a set of ASIAir-damaged images will be doing all ASIAir users a favour.
 
An enthusiastic ASIAir user could provide useful information on this. Does the astrometric solution only get written to the header after an "auto-centre" "goto" (if this is not the case, I don't know where the solution comes from)? If so, what actions "clear" the solution (i.e. stop it being written to the header) - for example is it cleared by a small manual "nudge"? (it surely should be)
I use ASIAir Pro extensively, though I am not much of an IT guy. I get the focal length error in PI EVERY TIME. That's mostly when I just type in the catalog number of the target and allow ASIAir to go to that target and center it, which it appears to do pretty well. But when I do the manual centering, only once in awhile to frame the target how I want it, I still get the error.
ZWO appears to be completely baffled by reports of this problem with the binned astrometric data that they themselves put in. They must believe that doing so somehow "helps"? On their bug forum, they have asked for clarification.
I could only put down what I can understand from what has been said here, that is, that it is a problem induced by adding binned plate solving data (astrometric data) into the FITS headers. Ha, to cover my weaker understanding, I linked this discussion to them.
 
But when I do the manual centering, only once in awhile to frame the target how I want it, I still get the error.
That is a real puzzle! The (4x4 binned) solution in the header must come from running a plate solver on a 4x4 binned image, and the only time the ASIAir is likely to do that is for the "auto-centre" function. The key, important point to communicate to ZWO is that this (4x4 binned) solution is wrong for any subsequent (typically 1x1 binned) image - so please don't (EVER) write it to the header - it will ALWAYS be wrong. (the RA/DEC of the image centre may be more or less right, but the rest of the solution is complete nonsense).
 
That is a real puzzle! The (4x4 binned) solution in the header must come from running a plate solver on a 4x4 binned image, and the only time the ASIAir is likely to do that is for the "auto-centre" function. The key, important point to communicate to ZWO is that this (4x4 binned) solution is wrong for any subsequent (typically 1x1 binned) image - so please don't (EVER) write it to the header - it will ALWAYS be wrong. (the RA/DEC of the image centre may be more or less right, but the rest of the solution is complete nonsense).
I wish I could sic you on ZWO. I am up to here with this error and for me it always happens. Every time. Last time, I tried to use the "Image Solver" script (is that the right one?). My understanding of it is that you run it and it corrects the FITS headers (some guy told me that). That didn't work for me. It ran and said success, but when I tried PCC again, it still failed.
 
If ZWO are so determined to keep writing this unhelpful rubbish to the header, can't they at least implement an option to switch it off?
 
Just received information from ZWO. They have corrected the error in the latest issue of the ASIair App,
Not yet had a chance to test it yet as they have only released a Beta version.
 
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