Biggest Newt You've Run on a Mach 2? - Forums

Topic starter

10 days ago · Edited: 10 days ago

I'm toying with the idea of getting an imaging newt in 2026 or later and wondering how big some of you have gone for a Mach 2. I've been chatting with Catalin from CFF and he makes a 250mm and a 300mm f3 Newt.

The 250 I think would be no problem, it is 15kg and 870mm long. The 300 would be a killer f3 scope, but it's 19kg and 1020mm long, with a larger diameter pushing the weight even further out. According to "Karen" the 250 should be no problem, it's handily in the Green, however the 300 is right on the edge of yellow. Mounting the focuser and image train on the underside would definitely help.

I could always sell the Mach 2 and get an 1100/1150. But for the sake of this conversation would the Mach 2 be up to the task?

Hoping for some feedback from some folks who have mounted a big newt on a Mach 2 and can give some guidance. Thanks!

Engaging

Rick Krejci

10 days ago

I had a 250 f4 newt on the Mach 2 and it did handle it fine…when the wind was calm. Since I don't have a protective observatory, the 250 was an absolute wind sail and images from breezy nights were impacted. The weight of a Newt is at each end and highest wind profile is at the camera end. f3 would be shorter, but I'd imagine the mirror would be a bit heavier so the balance point wouldn't be mid-way on the tube. Could be wrong about that.

If it's in an observatory, it should be much less of an issue. Or a truss would be less prone to it

I went to a side-by-side 140 f7 APO and a 91 f4.9 Petzval and the Mach 2 handled it without issue and was less prone to wind. Still in the green on the chart.

I'd be concerned with the combination of height + length + weight of a 12" even at f3 unless it's in a controlled area.

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Arun H

Frequent contributor

9 days ago · Edited: 9 days ago

Rick Krejci:
I had a 250 f4 newt on the Mach 2 and it did handle it fine...when the wind was calm. Since I don't have a protective observatory, the 250 was an absolute wind sail and images from breezy nights were impacted. The weight of a Newt is at each end and highest wind profile is at the camera end. f3 would be shorter, but I'd imagine the mirror would be a bit heavier so the balance point wouldn't be mid-way on the tube. Could be wrong about that.

If it's in an observatory, it should be much less of an issue. Or a truss would be less prone to it

I went to a side-by-side 140 f7 APO and a 91 f4.9 Petzval and the Mach 2 handled it without issue and was less prone to wind. Still in the green on the chart.

I'd be concerned with the combination of height + length + weight of a 12" even at f3 unless it's in a controlled area.

wind is a different beast than moment from weight. Wind load would depend cross sectional area and length from the point of rotation. The big issue with wind is that it will cause an unpredictable torque that can only be compensated for after the encoders detect the movement it causes and there will be a lag due to the inertia of the scope and counterweights before it can be compensated. By which time, the wind moment can change. Whereas the moment from the scope changes relatively slowly. Any scope that experiences a wind moment that is large in comparison to the moment caused by its weight would create a problem for any mount regardless of weight capacity. I don’t believe the Mach2 or any AP graph makes a claim that anything in the green would be wind resistant.

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Chris White- Overcast Observatory

Topic starter

9 days ago

I'm at HCRO inside a large Observatory. There are rarely any issues with wind, it just dies right down at sunset. I think in the lastvyear there was one night that the roof was closed all night from wind (10+mph).

Chris White- Overcast Observatory

Topic starter

9 days ago

Thanks Rick. I appreciate hearing about your experience with a 250. Im probably leaning that way just because the 300 is so much bigger

Rick Krejci

9 days ago

Arun H:
Rick Krejci:
I had a 250 f4 newt on the Mach 2 and it did handle it fine...when the wind was calm. Since I don't have a protective observatory, the 250 was an absolute wind sail and images from breezy nights were impacted. The weight of a Newt is at each end and highest wind profile is at the camera end. f3 would be shorter, but I'd imagine the mirror would be a bit heavier so the balance point wouldn't be mid-way on the tube. Could be wrong about that.

If it's in an observatory, it should be much less of an issue. Or a truss would be less prone to it

I went to a side-by-side 140 f7 APO and a 91 f4.9 Petzval and the Mach 2 handled it without issue and was less prone to wind. Still in the green on the chart.

I'd be concerned with the combination of height + length + weight of a 12" even at f3 unless it's in a controlled area.

wind is a different beast than moment from weight. Wind load would depend cross sectional area and length from the point of rotation. The big issue with wind is that it will cause an unpredictable torque that can only be compensated for after the encoders detect the movement it causes and there will be a lag due to the inertia of the scope and counterweights before it can be compensated. By which time, the wind moment can change. Whereas the moment from the scope changes relatively slowly. Any scope that experiences a wind moment that is large in comparison to the moment caused by its weight would create a problem for any mount regardless of weight capacity. I don’t believe the Mach2 or any AP graph makes a claim that anything in the green would be wind resistant.

I understand. I'm just relaying my experience with a 10" newt on a Mach 2.

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John Stone

9 days ago

I’ve got a 58” long, 50 lb, TOA-130 on my Mach2 that tracks sub 0.3” RMS (and sometimes sub 0.2” RMS).

It’s not wind sail but it’s longer and just as heavy as that Newt would be. In fact it’s 5 lbs above the line in the Dec chart but still works great.

That newt would be way below the line in the Dec chart and just half-way through the ‘extended performance’ yellow area in RA.

I’d take a chance on it. I’d be very surprised if there were any problems in an observatory.

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ScottF

Frequent contributor

9 days ago

I have an 11” Rasa which weights 43 lbs, plus computer, celestron dew heater and camera, photon cage, etc. , so the actual weight is a few pounds more and it’s about 838mm long not including the camera/lens shield on my Mach2 and it seems to function well. It is housed in a ROR backyard observatory so wind is not usually an issue.

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