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Another EQ8


Zakalwe

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I've never used PECPrep before, so I am not sure if I can interpret this data correctly. I've loaded the PHD guiding log if anyone wants to download it and interpret it? I'd really appreciate it if someone could do this. PHD_log_30Dec13.txt

The guide star was lost at the end of this run (the clouds rolled in, as per usual) which I think explains the peak in the DEC data at the end?

PECPrep analysis of the RA axis:

post-9007-0-65743700-1388680570_thumb.jp

Periodic Error Correction for the RA axis:

post-9007-0-34124100-1388680579_thumb.jp

PECPrep analysis of DEC axis:

post-9007-0-51221800-1388680584_thumb.jp

PEC for DEC axis:

post-9007-0-66108700-1388680589_thumb.jp

Less than 2 arc seconds periodic error? Is that right? If so, then I think that I have every reason to be pleased with this mount... (though I am probably mis-reading what PECPrep is telling me!!!)

I was using a QHY5 on a Skywatcher OAG. The main scope is a Equinox 80 Pro (500mm f6.25) which was reduced with a Televue TRF-2008 (resulting in 400mm focal length at f5). The main imaging camera was an Atik 428EX (4.54 µM pixels)

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Hi - I have not used PECPREP either - but have just started using EQ8 with EQMOD - the backlash in dec is there but small and seems symmetrical around the dec axis - can you post any PHD graphs?-mine are very good on RA less perfect on Dec but my polar alignment is still out due to clouds!! -when I get good weather will try again- so far like you  encouraged though - best wishes Tony

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Hi - I have not used PECPREP either - but have just started using EQ8 with EQMOD - the backlash in dec is there but small and seems symmetrical around the dec axis - can you post any PHD graphs?-mine are very good on RA less perfect on Dec but my polar alignment is still out due to clouds!! -when I get good weather will try again- so far like you  encouraged though - best wishes Tony

Hi Tony,

Sorry, I didn't screenshot the PHD graph. I did download PHDLab (http://countingoldphotons.com/phdlab-intro/ ) but is is crashing when I import the log file.

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Well, the backlash in Dec on my mount seems to have disappeared over Christmas! :-)

I got back home this evening and the skies cleared, so I've been out playing.

It seems that I've not got good enough equatorial alignment at the moment as even a couple of minutes capture using the 60Da on the 80mm 'scope shows star trails, but at least they are straight lines which suggests that the PE is small.

I hope that you've been able to get out with your 'scope tonight.

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Thanks Stephen.

I've jus been out and spent some time sorting a focus issue in my OAG. My aim was to get some more data on IC1805. Predictably, as soon as I had sorted everything, aligned on the target and started the PHD guiding calibration the clouds rolled in. :mad:

Someone please remind me again why I have spent blooming £thousands on this dratted hobby... :mad: :mad: :mad:

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I spoke too soon about the Dec backlash, it came back again when pointing west. Worse, when I parked the scope in my custom position (RA vertical, Dec pointing West and horizontal) as it was close to horizontal the worm gear started squeaking with each revolution!!!! It sounds as if it's started bottoming out on the gear.

Of course, this means that both the worm gear and the Dec gear itself must be slightly eccentric, the worm gear giving the sqeak-squeak as it revolves and the Dec gear having a different radius between East and West.

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I've given it up as a bad job for tonight. The clouds started to clear so I unparked and calibrated PHD. Started the first sub and the clouds rolled in.. I waited for a bit and then rolled the roof closed. Just as I started to tighten the turnbuckles down, it started to lash with rain.

Gawd, I hate this country at times.....

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I've never used PECPrep before, so I am not sure if I can interpret this data correctly. I've loaded the PHD guiding log if anyone wants to download it and interpret it? I'd really appreciate it if someone could do this. attachicon.gif

Less than 2 arc seconds periodic error? Is that right? If so, then I think that I have every reason to be pleased with this mount... (though I am probably mis-reading what PECPrep is telling me!!!)

I was using a QHY5 on a Skywatcher OAG. The main scope is a Equinox 80 Pro (500mm f6.25) which was reduced with a Televue TRF-2008 (resulting in 400mm focal length at f5). The main imaging camera was an Atik 428EX (4.54 µM pixels)

Those nice flat graphs look very promising.

Did you capture the data with the guide corrections turned off / ST4 lead unplugged ?  The guider should be running but not issuing guide corrections to the mount to measure the true PE curve.

Dave.

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Those nice flat graphs look very promising.

Did you capture the data with the guide corrections turned off / ST4 lead unplugged ?  The guider should be running but not issuing guide corrections to the mount to measure the true PE curve.

Dave.

Hi Dave,

No. I just dumped a PHD log file into PECPrep. The PHD log was created during an active imaging run. Guiding was being carried out over ST4

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I spoke too soon about the Dec backlash, it came back again when pointing west. Worse, when I parked the scope in my custom position (RA vertical, Dec pointing West and horizontal) as it was close to horizontal the worm gear started squeaking with each revolution!!!! It sounds as if it's started bottoming out on the gear.

Of course, this means that both the worm gear and the Dec gear itself must be slightly eccentric, the worm gear giving the sqeak-squeak as it revolves and the Dec gear having a different radius between East and West.

Sorry to hear this, obviously. While I'm not going to do any more testing I was concerned that, at the tightest point, there was no backlash whatever, even with a long doevtail inserted to feel for it. To me this said, 'too tight.'

Olly

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Hi Dave,

No. I just dumped a PHD log file into PECPrep. The PHD log was created during an active imaging run. Guiding was being carried out over ST4

In that case what you are analysing is your guiding performance rather than Periodic Error itself.   Usually a guided log would appear quite flat in the time domain (as you would expect) and with no significant peaks in the frequency domain. If the data does show distinct and significant peaks in the frequency spectrum, then this indicates your guiding setup has failed to compensate for all of the periodic error present (perhaps due to minimum movement or hysteresis settings).

You can actually record PE whilst guiding if you use the AutoPEC feature of the later test releases of EQASCOM. This will output its own log (so no need to generate phd log) that can then be loaded into PECPrep for detailed analysis.

Chris.

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In that case what you are analysing is your guiding performance rather than Periodic Error itself.   Usually a guided log would appear quite flat in the time domain (as you would expect) and with no significant peaks in the frequency domain. If the data does show distinct and significant peaks in the frequency spectrum, then this indicates your guiding setup has failed to compensate for all of the periodic error present (perhaps due to minimum movement or hysteresis settings).

You can actually record PE whilst guiding if you use the AutoPEC feature of the later test releases of EQASCOM. This will output its own log (so no need to generate phd log) that can then be loaded into PECPrep for detailed analysis.

Chris.

Thanks for the clarification Chris.

Next question: How does one setup AutoPEC?

<edit> Ignore that...I've found it in one of your(extremely helpful) YT videos

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I'll have another bash at PE recording at some point (if it ever clears up here!)

The data you have recorded does show your mount is guiding extremely well, which is great to see and a good indication you'll see a nice PE curve from your next test runs.

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Thanks for the clarification Chris.

Next question: How does one setup AutoPEC?

<edit> Ignore that...I've found it in one of your(extremely helpful) YT videos

If you look in the files/documentation section of the yahoo group you will find a draft VS-PEC document that covers the AutoPEC interface - the only autopec video shows my initial attempt  - the user interface has changed a bit since then.

Chris.

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 What no comments!! unusual for an EQ8 at the moment   :laugh: has anyone else done a PE run and seen similar results?

Managed to reduce my dec backlash today, not as difficult as first thought, if one removed the plastic cover over the worm block, the coupling can be turned with fingers to better assess the resistance to rotation and fine tune any tight spots of the worm  

Ray

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 What no comments!! unusual for an EQ8 at the moment   :laugh: has anyone else done a PE run and seen similar results?

Managed to reduce my dec backlash today, not as difficult as first thought, if one removed the plastic cover over the worm block, the coupling can be turned with fingers to better assess the resistance to rotation and fine tune any tight spots of the worm  

Ray

Hi Ray,

I'll have a look at it later...it'll give me a chance to practice on PECPrep.

Thanks for sharing these.

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Maybe I'm off the norm with mine but I've had a lovely flat PHD graph, Maxim reports my stars as being 0.01 out of round (best I have ever seen) ... I honestly don't feel the need to analyse the PE and worry myself :)

</2p>

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Maybe I'm off the norm with mine but I've had a lovely flat PHD graph, Maxim reports my stars as being 0.01 out of round (best I have ever seen) ... I honestly don't feel the need to analyse the PE and worry myself :)

</2p>

Hi Stephen, i have to agree with the sentiment, it's the shape and outcome of the image  that matters, however for some..it's also the knowledge and practical benefit of knowing  that a mount meets the expectations put on it otherwise there would be no use in having the software to measure such things.

Ray

Ray 

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