Testing RC8 carbon telescope on Avalon M-Zero mount setup - Forums

Topic starter

Jan 18, 2026

Hey everyone!

I recently picked up a second-hand Avalon M-Zero and I'm exploring what this mount can handle. I've read quite a few mixed experiences about using larger scopes like my RC8 on the M-Zero - plenty of reports saying it's not practical or doesn't work well, but also some success stories. So I decided to test it myself!

The Setup:

RC8 Carbon + imaging train (reducer, focuser, EAF, OAG, ASI533MC Pro) = 7.8kg total
Image scale: 0.72"/pixel
For this initial test, I mounted the scope as low as possible on the M-Zero
This leaves very little clearance between camera and mount (see photo) and limits movement range somewhat during slewing, but I can achieve balance with just a 50mm guide scope + 100g counterweight
I have both a 50mm guide scope (ASI120MM Mini) and OAG (ASI174MM Mini) available, so I wanted to compare guiding performance between the two

Important notes:

My scope isn't properly collimated yet
I wasn't sure if the OAG would pick up stars reliably

Night 1 - Initial Test: Only 25 minutes before clouds rolled in, so I could only test the guide scope. Results: 0.6"-0.8" RMS. After analyzing the EKOS guide data, I noticed my RA settings were too aggressive, so I adjusted them for night 2.

Night 2 - M45 & M38: Started with M45 (altitude ~55°-45°):

Guide scope: consistent 0.5"-0.6" RMS
OAG: 0.4"-0.5" RMS

The stars looked decent in my subs (despite the collimation issue), so I moved on to M38 (altitude 50°-75°). Normally I'd shoot open clusters with 30s subs, but since I'm testing the mount, I went with 66s exposures. I maintained consistent 0.58" RMS for several hours, though I couldn't get it any better than that.

At the end of the night, I briefly tried IC434 Horsehead (altitude 33°-30°) but got 1"-1.3" RMS with the guide scope. The OAG wouldn't work at all for some reason. Though there was also quite a bit of moisture in the air at that point.

My Questions for the Community:

Are these results acceptable and comparable to what others are seeing? As a new Avalon user, I don't really know what to expect.
Is the RMS increase around 35° altitude in the south to be expected, or was that likely weather-related?
I'm considering running a similar session with the scope mounted much higher on the M-Zero, but this would require ~2.6kg of counterweights instead of the ~1kg I'm using now. Would that have a significant effect on performance, or should I expect similar numbers?
To really gain freedom of movement, I'd need to mount the scope further forward by extending my Vixen plate. Since the DEC balance is currently very good, I'd need to add weight to the back. This would be beneficial for future upgrades (rotator, larger filter wheel), but increases total weight and torque requirements. Do you think this becomes problematic?

I'll keep this thread updated with any developments, but I'm really curious to hear from other Avalon (M-Zero) users about their experiences!

Clear skies!

📷 M38 - Avalon M-Zero First Test with RC8

https://app.astrobin.com/i/dxhiti/

📷 M38_abberation.jpgMainly collimation problems not really guiding problems.

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Karl Zöchmann

New contributor

1 hour ago

I use a GSO RC8 and from most comments from other forums was to use OAG especially for RC scopes, I always had issues finding stars and guiding numbers weren’t all that good ( I can’t remember the guiding numbers) plus not being able to use multi star in PHD2.

In the end I went a piggyback system with a 400×80 SW refractor as I had read that the guide scope should be about a ¼ of the main scope, it does add weight but I use an EQ6r, and I’ve never looked back.

In the beginning of the night it was stable at 0.63 rms, midnight was around 0.78 and towards the end was 0.46 total rms.

I’ve never gone back to OAG even through it would cut weight by quite a lot. I think my set up is about 11kg, that’s with Moonlite focuser, EAF, ASI2600mc, CCDT67 (down to 1325mm FL) and the refractor with rings direct mounted to the vixen bar at the top.

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Tony Gondola

Frequent contributor

Exemplary contributor

1 hour ago

I wouldn’t obsess about guiding RMS as that way waits madness. As long as your stars are round I would press on to other concerns. I think most people with average hardware get in the range of 0.6” and 0.4” rms. Of course it’s very much affected by the seeing. That’s why you really shouldn’t chase the numbers based on the result of one night. Once you’ve run your rig for awhile you’ll know what a good night looks like. You’ll also know what happens when the air is rough and wind gusts are buffeting the rig.

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Alex Nicholas

1 hour ago

I think you will be very surprised at what the M-Zero is capable of. I had MANY nights where my guiding was 0.25~0.3” RMS with mine, and the only reason I eventually sold the beautiful little thing was when my lust for a large APO took over, and there was no sensible way of mounting a 120mm f/7 refractor on it.

As Tony said, your biggest issues will come with seeing and wind.. while the mount is a rock solid performer, wind when using an open tube 8” catadioptric scope like an RC at such fine pixel scales will inevitably cause issues.

I moved from running my 65mm APO on a Losmandy G11, which was BULLETPROOF even in relatively high wind conditions, to using the 65 APO on the M-Zero. Even with that, a solid wind gust would cause the odd lost frame at 2.2”/px, so at 0.8”/px, you’re likely to lose a few in wind, and seeing will probably blur your images faster than any normal guiding performance will.

Given good stable seeing and no wind to gentle breeze, I see no reason that you won’t find success with this combination.

Out of curiosity, are you following avalon’s detailed guidelines regarding guiding parameters for the mount? These mounts guide VERY differently to a harmonic mount or a german equatorial as a result of the extreme reduction drive and fully belt driven, 0 gears nature of the mount yielding no backlash. I think you’d do very well to look at their setting recommendations, and 0.5~0.7” certainly isn’t BAD, but the mount is more than capable of less than half that error.

I don’t think I ever had more than 7kg on my M-Zero, but I was able to run that with 250g of counterweight, and was 100% free to image from horizon to horizon without doing a meridian flip at all… It was certainly a bit of a dream mount in that regard!

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