Re: Upgrade from CP on an AP900


Hi Murray,
Sorry I was a bit hurried and on my way to work on my earlier response.
This is certainly a 'home project'. I am in Australia and everything including a complete lobotomy falls into the home project category.

You only require a set of Imperial / English / Us Hex Allen Keys for the job. Removing the old CP1 box and it's saddle is the only part that requires a bit of time.
The entire circuitry has to be removed before you can unscrew the CP1 box and it's saddle.
After you remove the top cover you unscrew the remaining two bottom screws on the front panel.
This only leaves the RA and Dec drive sockets to be unscrewed from memory before you lift out the circuitry in one piece. The drive sockets are held by 2 screws each.
The CP3 box is only 1/4 the thickness of the CP1 box and just sits on a half dovetail locked by 2 grub screws.

This may sound complex but I did it during my lunch break one day. If you can replace a card in a PC you can do it easily.

My reasons for changing were twofold.
1: I couldn't get reliable PEC with PemPro. I ended up not using it at all as in general it made things much worse.
2: I was also getting an erratic movement during the guide star exposure which smeared the guidestar into a streak. This seemed to be associated with Pulse Guide.
If I shut down PulseGuide and restarted it after tracking was running it seemed to be OK.

I have only done several lots of Ha with the new box but it has been fine in every regard and giving the sort of results I expect fron an AP mount.

Hope this is clear.

----- Original Message -----
From: Murray Hammick
To: ap-gto@...
Sent: Sunday, September 30, 2007 5:04 AM
Subject: Re: [ap-gto] Upgrade from CP on an AP900


Thanks for the feedback.

Was this a home project or did you send it off to be done by AP ? What sort of cost are talking about and also what were your main reasons for the mod ?

I have read - possibly on the AP site - that some mods are not worth it on older AP900s as the rest of the mount cannot be upgraded to take advantage of the better performance of the upgraded item. Was this a consideration with the CP1 - CP3 change.

Look forward to hearing back from you.


Brian Coote <dbcoote@...> wrote: Hi Murray,
I have just upgraded my GTOCP1 controller to the CP3.
I too was a bit unsure of how worthwhile it was.
I was having problems with running PEC on the old CP1.

I have only done 3 x 30min subs in Ha with the new CP3. This was with a 6 sec guide exposure and the 30 min subs gave me FWHM figures of 1.55 arc sec.
Very worthwhile.
The test image is at

----- Original Message -----
From: mphammick
To: ap-gto@...
Sent: Thursday, September 27, 2007 6:52 AM
Subject: [ap-gto] Upgrade from CP on an AP900

Anyone contemplated an upgrade of the CP on an AP900. I have the CP1
series and wondered whether one can do anything to modernise it - or
indeed whether it is worth it.


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