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Old 14-02-2017, 10:42 AM
tim.anderson (Tim Anderson)
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EQ8 PECPrep Results - are these OK?

The attached PECPrep analysis is from an imaging run of about 50 minutes. I'm not really sure what to expect from the EQ8 mount, but the error values look pretty good to me. Is there any point in applying the PEC curve to the mount, given the results?

Any assistance welcomed.

Tim
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Old 14-02-2017, 10:46 AM
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jenchris (Jennifer)
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My opinion is of little value.
But your pe is quite low and if you are using phd2 anyway probably has little benefit.
However having taken it, why not use it?
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Old 14-02-2017, 11:18 AM
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Troy
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I was under the impression this was suppose to be done without autoguiding.
If nothing else it shows a smooth pe curve - not a low one.

I would only alter the pec curve using unguided data.
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Old 14-02-2017, 12:14 PM
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Slawomir (Suavi)
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I agree with Troy - this needs to be done without autoguiding.

If this was your mount's tracking graph (not guiding), it would have been up there with the high end ones that have high resolution encoders
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Old 14-02-2017, 12:25 PM
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Shiraz (Ray)
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Hi Tim.
FWIW, my EQ8 has never done anything remotely like as good. However, if this is a guide graph with an incorrect pixel scale and timebase, it might indicate that your EQ8 is guiding normally.

suggest that you look at the following maybe:
- the worm period in your data is that of an EQ6, you need to set up an EQ8 in the startup panel, so that you get the right worm period - your FFT shows a PE residual at about the 198 sec worm period of the EQ8, so that bit is working right
- the pixel scale is possibly way out, did you set the guide scope focal length and guide cam pixel size in the startup panel and is dec correction on?
- as others have said, PE measurement requires that the guiding be turned off in phd2 while you do the measurement - this looks like you had guiding on.

In general EQ8's seem to come in at around 7 arcsec p-p PE and guide to better than 1 arcsec RMS. The worm period is short though, so you need fairly short guide exposures to ensure that PE does not leak into guiding - I find that 0.5-2 seconds works OK with mine and I don't need any PE correction (which is just as well, since it doesn't work in EQMOD). your data might indicate the level of guiding accuracy if you can correct the pixel scale.

Last edited by Shiraz; 14-02-2017 at 05:33 PM.
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Old 14-02-2017, 12:51 PM
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Atmos (Colin)
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I was under the impression (something I read a while ago) that the EQ8 has a permanently running PE correction. Or was that just with the hand controller?
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Old 14-02-2017, 04:10 PM
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Shiraz (Ray)
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Quote:
Originally Posted by Atmos View Post
I was under the impression (something I read a while ago) that the EQ8 has a permanently running PE correction. Or was that just with the hand controller?
I guess that permanentPEC might work with the hand controller, but at last try, VSPEC under EQMOD would not run on the EQ8, which I assume is the environment that Tim is using (if the problem has been fixed recently, would be happy to be corrected). Thankfully the mounts have such low inherent PE that it is not a major issue, just annoying that Skywatcher shows almost zero interest in supporting/optimising/improving their premium mount.

Last edited by Shiraz; 17-02-2017 at 03:20 PM.
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