CPC 800 on a wedge, bearing replacement required?

[NenoVento]

Hi all,

As some of you may know, I am the (proud) owner of a second (maybe third) hand Celestron CPC 800 which, on the past, has required some adjustments. Lately I've moved it into a little observatory I've made at my home and, to make things more interesting (ha ha) I placed it on a wedge (hoping to try my hand with AP, although I'll be perfectly happy if I get to make it work as an EEVA setup as well). The thing is that, since the scope was placed this way, I've noticed that, sometimes, it gets sort of stuck in the RA movement every now and then. This is clearly noticeable when moving it with the clutch off (disengaged?) however, if I force to move it back and forth a few times (also with the clutch off), it goes back to normal. I've looked around the Internet and, after finding Gary Bennett's excellent article "How To Replace Factory Original Nylon Azimuth Bearing Balls" , I believe that I need to take a look at how it is the situation with my CPC's bearings and, since for doing so I have to go through the task of dismantling it, I've already ordered new  bearings, just in case. However, before doing anything, I would like to ask you about your opinions on its guiding performance, which you can see below:

If I am not mistaken, I remember reading somewhere that normal accuracy for this kind of setup is about RMS 1.25", but I haven't been able to find the source again... Anyway, if this is true, this is more or less what I get in Dec.

Best regards,

NV

 

PS: I believe that I have the scope pretty well balanced (meaning that it doesn't move on its own when the clutches are off) by using a proper rail counterweight and two workout ankle weights, wrapped at the holder placed in lighter arm, as you can see below:

 

 

PSPS: Also, please notice that PHD2 Log Viewer says that in the session I had a Polar Alignment Error of 11.6' (despite my having performed one ASPA).

[Cosmic Geoff]

I have a CPC800 and had trouble with the azimuth bearing, which caused problems with tracking and a notable resistance when spinning the mount with the clutch released.

I followed the procedure you mention but fortunately found that all I needed to do was slacken off a large adjustment nut.

I have not read much positive about these mounts mounted on a wedge, and my own experience is that a C8 is not the best tool for deep space astrophotography.  All the deep space images I took with a C8 looked awful, giving me no incentive to persist, while those I took with a 102mm f5 refractor were often pleasing.

[newbie alert]

21 hours ago, NenoVento said:

 

PSPS: Also, please notice that PHD2 Log Viewer says that in the session I had a Polar Alignment Error of 11.6' (despite my having performed one ASPA).

I found ASPA ok for visual or planetary imaging.. but useless for deepsky.. sharpcap or polemaster is far more accurate, but not as accurate as the drift tool in phd2( just takes far longer)

Edited December 23, 2020 by newbie alert
Adjusted

[NenoVento]

Thanks for sharing your experience @Cosmic Geoff. I will be in the lookout for the situation on the "large adjustment nut".

About using the CPC on a wedge for DSAP (Deep Space Astrophotography), yes, so far I am not having much luck, even after using the f/6.3 reducer-corrector.  I still need to try with a camera that have a bigger sensor than the one I'm using (an imx290 that I bought for planetary imaging). Thankfully I also have a Cannon 600D, so I will be able to test this assumption 🤞.

Yesterday I also noticed that the DC socket is a bit loose (which was the cause for some connecting issues that were driving me crazy!). Now I also have a new task to add to my to-do list (thankfully there is an excellent how-to in IFIXIT by Michael Wofford), together with cleaning the inner part of the corrector plate 🥺.

Best regards,

NV

[Cosmic Geoff]

13 minutes ago, NenoVento said:

Yesterday I also noticed that the DC socket is a bit loose (which was the cause for some connecting issues that were driving me crazy!).

That is a problem with many mounts that use the same connector style. (e.g. SE series).  I have cable ties stuck on next to the sockets to restrain the cable. In the case of the CPC800, it helps if you pass the cable through the loop of the adjacent carry handle. You can also splay the centre pin with a sharp craft knife.

[NenoVento]

40 minutes ago, newbie alert said:

I found ASPA ok for visual or planetary imaging.. but useless for deepsky.. sharpcap or polemaster is far more accurate, but not as accurate as the drift tool in phd2( just takes far longer)

Thanks @newbie alert, I will try the PHD2 drift tool (unfortunately I don't have views of Polari from my little observatory).

Also thanks @Cosmic Geoff, I will try what you suggest, while I wait for the bearings to arrive. I already have received the new DC connecting set:

Which I purchased locally (since the shipment costs to my place from DigiKey were astounding).

Best regards,

NV

 

[newbie alert]

7 minutes ago, NenoVento said:

@newbie alert, I will try the PHD2 drift tool (unfortunately I don't have views of Polari from my little observatory).

You don't need to see Polaris for drift alignment.. just south for Az adjustment  and east or west for altitude..  you need to be on the equator and Dec 0 intersection  when pointing south

Edited December 23, 2020 by newbie alert
Added info