Telescope Reviews: Mach1 GTO vs. A-P 900 mounts

Hi there !

Well, it's actually something you "feel".

If you look at the specs on paper -- shafts and wheels -- the two mounts look indeed comparable. In both cases the AP900 has a slightly bigger shaft and wheel in RA (2.2" and 7.2" vs 2" and 6.75"), and slightly smaller in Dec (1.75" and 6" vs again 2" and 6.75"). This is nothing really significant.

OTOH, the masses are significantly different: 54 lbs vs 75 (and this difference is especially significant in Dec, i.e 17 lbs vs 37.5). Again, the AP900 is really a no-brainer portable mount, while both with the Titan and the AP1200 you have to be careful with your back.

In any event, assuming that both mounts have an hypothetical similar recommended payload (AP and Losmandy give different figures, 70 vs 100 lbs, but we all know how conservative Roland is...), I feel it more appropriate putting a 150lbs 2mt-long refractor (including cws and accs.) on a mount whose mass is 45% bigger than the other. Consider that in the Titan case the mass is just half -- and in the 900 only *one-third* -- the *moving long-arm* weight being supported.

Further, during one single evening, going to different objects, shifting observer, going straight through or using a diagonal, I find myself flipping scope easily five, six, seven, many times. This is usually done not using slewing but literally pushing the instrument to the other side of the meridian and flipping it. It's a very swift exercise and usually in 5 secs people can exchange their place at the eyepiece. This kind of flipping is dynamically demanding on the mount with a long instrument and really gives you the wrist of it. You do feel that, even if the pier is the same, the heavier mount reacts much better. In the same way dampens better any vibration...

Trivially, get two guys, one heavier than the other. Both of them lift the same when on the gym board. You would still call the heavier "more robust", btw. Now if they both have to lift something steady, no pbl. But if they have to hold it, spin it around and then stop, even though their strength on the gym board is similar, the heavier guy -- the more robust -- will stand the momentum drag much better than the other. And imagine that here the weight being considered is twice or three times their own weight...!

In any event, roughly, on similar pier, I find the AP900 dampens a 180 f/9 as efficiently as the Titan dampens a 200 f/9. If you do the maths you'll see that the ratio between the two OTAs is about 1:1.45. And that happens to be exactly the ratio between the two masses of the mounts.

Hope it makes sense

-- Max