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CG5-AGST and PEC

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#1 A. Viegas

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Posted 30 November 2012 - 10:14 PM

Does anyone know if the new HC+ version 5.21.2200 ( in beta ) will allow PEC in the CG5 to be retained? As far as I understand the CG5 is limited in that PEC recording is lost when the mount is turned off. first, there are some posts in the CG5 forum on yahoo saying that newer firmware retains the PEC data, additionally if you hibernate the mount would the PEC info be stored in any case?

Al

#2 orlyandico

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Posted 01 December 2012 - 12:26 AM

The issue with the CG5 is that there is no PEC indexer on the RA worm. The indexer is used to determine the starting position of the RA worm between power cycles.

Actually a lot of (stepper) mounts can remember the PEC index even without an indexer, which is why I don't know why the CGEM needs the indexer.. (which the CG-5 doesn't have)

#3 rmollise

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Posted 01 December 2012 - 08:09 AM

Because, like the CG5, the CGEM uses servos, not steppers. ;)

#4 A. Viegas

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Posted 01 December 2012 - 09:02 AM

So that means that even if you hibernate the mount, when it wakes up the PEC data stored or not stored will nonetheless be unreliable due to the lack of a reference indexer?? Still, if you end your observing session in the "Home" position, hibernate and you have the PEC data saved to your computer, can't you just re-upload it at the start of a new imaging session?? why will that not work?

Al

#5 orlyandico

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Posted 01 December 2012 - 10:57 AM

Rod, that's the thing, both steppers and servos are absolute positioning systems. For both systems, you can actually store the worm angle in NVRAM and thus avoid the need for an indexer.

This is exactly the same situation when you park the mount - the Nexstar remembers the ALT and AZ angles. It is no more different to also save the worm angle.

Al - the indexer is basically a wheel with a slot that is attached to the RA motor output shaft. So it provides a "known starting" worm position angle. Again, even without such an indexer, stepper or servo, it should be possible to save the worm angle. I just don't know why not.

#6 mclewis1

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Posted 01 December 2012 - 11:01 AM

So that means that even if you hibernate the mount, when it wakes up the PEC data stored or not stored will nonetheless be unreliable due to the lack of a reference indexer??

Al, That's correct.

Still, if you end your observing session in the "Home" position, hibernate and you have the PEC data saved to your computer, can't you just re-upload it at the start of a new imaging session?? why will that not work?

The physical mount position is no problem to reproduce but the position of the worm gear isn't as easy (but as Orlando has mentioned it might be possible in other ways). I've read that some folks have run a comparison between a stored PEC and a partial PEC training run and tried to line them up but it doesn't appear that there are any commercial products that are/will doing this. You would still have to run the worm for a while to figure out where it's positioned and that would be the same as doing another PEC training run so why not just do that?

Good questions ... many of which most of us CG-5 owners have or will think about. It's interesting to delve into how the mount actually operates, which helps everyone understand what's really going on behind the scenes.

#7 orlyandico

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Posted 01 December 2012 - 11:13 AM

IMHO if your PE is not too large, autoguiding will be enough, no need for PEC.

you only need PEC badly if you don't want to autoguide.

#8 mclewis1

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Posted 01 December 2012 - 11:22 AM

Exactly.

The desire though is to have a nice simple PEC to help smooth out some of the larger PE on this lower end mount. For many folks who want to do short fl imaging or video observing this would be enough and very beneficial (and no need to add a more complex and "weighty" autoguider).

Alas this nice simple feature is available only on heavier and more expensive mounts.

#9 Jmel

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Posted 01 December 2012 - 04:24 PM

It's funny, maybe I'm just dense, but I read this whole thread and didn't see a direct answer to the OP's question... Did I miss something?

#10 orlyandico

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Posted 02 December 2012 - 12:49 AM

Answer: the CG-5 has no Permanent PEC.

The rest of the posts are speculation as to why this is so.

#11 Jmel

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Posted 04 December 2012 - 11:25 AM

Answer: the CG-5 has no Permanent PEC.

The rest of the posts are speculation as to why this is so.


That's counter to what the guy from the yahoo group was saying. He was saying that newer mounts with the latest firmware seem to be able to do it.

http://tech.groups.y...G5/message/2054

Does anyone dispute that?

#12 wolfman_4_ever

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Posted 04 December 2012 - 01:57 PM

Why not test it and find out yourself?

Just because someone else says it works or does not work, does that make it definite? 17 days tell the 21st!

#13 orlyandico

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Posted 04 December 2012 - 03:22 PM

hmmm not aware of that

just did a guiding exercise with my CGEM.. the PEC didn't make much difference (guiding vs guiding + PEC). maybe the PEC routine is the CGEM isn't as good as that in the CGE Pro. very likely!

i guess PEC would only be useful if you wanted to go unguided. but due to the 8/3 in the CGEM motor (also present in the CG5 I guess since it's the same motor) PEC can't lower your PE below about +/- 8" or so.

#14 fuzzystuff4ever

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Posted 04 December 2012 - 04:25 PM

Has Celestron had permanent PEC on any of their scopes or mounts? I thought their rationale (in the past at least) was that it was "better" to train the PEC every time you set up the scope rather than have one recorded permanently.

Brian

#15 rmollise

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Posted 04 December 2012 - 06:33 PM

Depends on the mount. Most recent mounts other than the CG5 and the basic NexStars most assuredly have and have had PPEC for a long time. Remember, Meade's lower level scopes like the LX90 don't have PPEC either. I have never heard of such a rationale.

#16 mclewis1

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Posted 04 December 2012 - 07:01 PM

just did a guiding exercise with my CGEM.. the PEC didn't make much difference (guiding vs guiding + PEC). maybe the PEC routine is the CGEM isn't as good as that in the CGE Pro. very likely!

Orlando, No, it's the same firmware for all of Celestron's gem mounts. All that changes are the enabling of mount specific features (RA/DEC switches, Meridian function, worm gear indexing, etc.) within the common code base.

Autoguiding will mask many benefits of PEC. A good test would be shooting subs with and without PEC but not using any autoguiding.

#17 orlyandico

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Posted 04 December 2012 - 08:25 PM

celestron's own CGE Pro web page clearly shows that PPEC + AG does better than either of them alone...

#18 Jmel

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Posted 05 December 2012 - 06:00 PM

Why not test it and find out yourself?

Just because someone else says it works or does not work, does that make it definite? 17 days tell the 21st!


Great idea. I just got the CG5 last week though, so I'll have to figure out how to even try it. I'm coming from an alt/az se mount.






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