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Astro-Physics GTO question

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#1 Jesus Munoz

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Posted 23 January 2013 - 12:16 AM

Hello,

I'm planning to buy a high payload capacity mount, an Astro-Physics 900 or 1200. Reading about the options I noted there are some options in the used market, the GTO CP2 and the CP3, the newer. What's the difference between GTO CP2 and CP3?

Thanks

#2 orlyandico

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Posted 23 January 2013 - 12:41 AM

the CP3 can take an "S" chip which means you can use APCC and (reputedly, with a good pointing model) do 20-30 minute unguided subs.

the CP2 can't take this chip. It also I believe is not compatible with the newer handsets, so you don't have Quick Drift Align and some other features.

having used the CP3 for a month, I would say if the difference is large (say 2000+) and you don't intend to use APCC (which requires a PC for the pointing model, just like Paramounts and the ASA mounts, and costs $500+ in of itself) then you can save money with the CP2...

#3 Ray Gralak

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Posted 23 January 2013 - 12:58 AM

The CP3 also has extended autoguider commands which pass the time to move the mount built into the command instead of relying on the (sometimes not so accurate) timing of windows to issue start/stop commands. So, IMO if you are planning to autoguide via the AP V2 ASCOM driver then that feature alone makes it worth it. The "S" chip, which is now available, also adds commands to read back the mount's current state as well as autoparking the mount on a temporary power failure.

-Ray

#4 orlyandico

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Posted 23 January 2013 - 01:05 AM

one possible alternative...

AP sells the handset alone for $1000-ish. I am not sure if an older handset for a CP2 can be upgraded to 4.17 which is the latest version. If it can be...

then maybe you can buy the CP3 controller alone from AP. It would almost certainly cost less than the handset.

Ray - autoparking with the S chip means I can cut the power without doing an explicit park command, and on startup I can just resume from park? sounds like a killer feature that would help remote imagers a lot... if it's foolproof, as the older AP mounts don't have homing sensors...

also - the extended autoguider commands would only be utilized if pulse guiding through the ASCOM interface right? so "traditionalists" / luddites like me who guide through the ST4 interface won't be able to use this?

#5 Ray Gralak

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Posted 23 January 2013 - 09:30 AM

I think you can just buy the CP3 without buying the new handset.

Ray - autoparking with the S chip means I can cut the power without doing an explicit park command, and on startup I can just resume from park? sounds like a killer feature that would help remote imagers a lot... if it's foolproof, as the older AP mounts don't have homing sensors...


Yes, the new autoparking command was implemented specifically for remote imaging so when power is lost then regained the mount would not automatically start tracking. Having the mount start tracking automatically before being initialized is great for visual users but for imagers it can cause the mount to appear to be "lost" if not initialized soon after power is restored.

the extended autoguider commands would only be utilized if pulse guiding through the ASCOM interface right


Yes, that's true.

However, the CP3 also has commands to program PEC directly through an upload instead of using PEMPro's playback capability. Effectively programming a PEC curve would help autoguiding even when using the ST-4 interface.

-Ray

#6 orlyandico

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Posted 23 January 2013 - 01:17 PM

whoah.. the CP3 is $995 by itself. handset is $1060.

to the OP.. there is for example an AP1200 CP3 on the a-mart classifieds for 7500 including RPA but pickup in Utah. Not too far from Mexico to drive, right? :)

There also is a AP1200 CP2 for 6500. If you got a CP3, would end up costing the same..

#7 Jesus Munoz

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Posted 23 January 2013 - 11:17 PM

Not too far from Mexico to drive, right? :)


:roflmao: Far, far away. If the mount was in Texas...

I think CP2 is enough for my interests and upgrade in the future.

I really appreciate all of your answers. My decision is clear now.

Thanks

#8 Calypte

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Posted 24 January 2013 - 01:59 AM

Yes, the new autoparking command was implemented specifically for remote imaging so when power is lost then regained the mount would not automatically start tracking. Having the mount start tracking automatically before being initialized is great for visual users but for imagers it can cause the mount to appear to be "lost" if not initialized soon after power is restored.

Which may explain some strange behavior I've experienced, such as the mount going to a spot several degrees west of the correct place when reactivated. But the automatic resumption of tracking has other consequences, too. I got up one morning to find my scope pushing against the mount after a brief overnight power outage, when it was supposed to be in a parked position.






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