Midrange GEM ?

[Wavytone]

Considering a midrange GEM to carry 7" Mak + 5" refractor... could later be expected to carry 13" f/12 cassegrain. Mainly interested in excellent tracking at high power. Push-to with digital circles would be nice, but not a must-have. GOTO - no thanks, not interested in coffee grinders.

- EQ6 - too small IMHO, worms hopelessly tiny
- Losmandy G-11 - possible.
- Vixen Atlux - possible.

Or ?
Why ?

Suggestions please.

[gbeal]

I have an M703, or my 10" f5 newt, on a CGE, but it doesn't qualify as it is in the coffee grind category. Stunning mount though.
Gary

[Bassnut]

For imaging on a 13" cassegrain, and "excellent tracking at high power", you are looking at a minumum of a Losmandy Titan IMO. The G11 or less wont cut it (unless you get a light carbon tube OTA). Dont understand the adversion to Goto at that level, its going to be very difficult without it, and anyway, the drive system will need to be so good that Goto is a relatively inexpensive addition. You will need some control electronics anyway for guiding, the goto contoller has that built in (and PEC).

You seem to have high expectations for imaging (oops, is that what you want to do, or visual?), but the mount ideas you have dont match. The mount is simply the most important item bar none, a rethink, yes?.

[Wavytone]

What bothers me is to see people claiming they use 8", 10" Newtonians or C11's or C14's on an EQ6. In my younger days the standard rule of thumb was worm wheels no less than 50% of the diameter of the scope. Aluminium gears are still the same as they were 20 years ago - if not worse - and those in an EQ6 are quite simply too puny even for my 7".

My use is mainly visual - through the 7" Mak or 13" which are for lunar & planetary. Imaging is not a high priority - if I do it will only be through a small ED refractor (f/7).

I would like it to track, encoders for Argo Navis or similar are desired, but I frankly don't need GOTO as I've learnt the sky well enough over the past 35 years.

Once upon a time I was using a 4" refractor on a mount that had a 6" phosphor bronze worm with 1440 teeth with a worm driven at close to 1 rpm. On my 8" f/7 newtonian I had a 10" worm wheel, with 1.5" axes. THAT was what I considered a decent mount, but no-one makes that kind of gear anymore and frankly most of the mounts I see now appear to be lightweight rubbish when you take into account the mass of the optics sitting on top + the counterweights.

[Bassnut]

Well, OK, for visual, you can load to spec and more, and yes I suppose goto then is a luxury you dont need.

No one wants to pay for proper engineering these days, its very competitive, and gear manufacture (so they would have us believe) is sophisticated enough to allow smaller diameters, and compensation for (periodic) irregularity with PEC.

[Wavytone]

"gear manufacture (so they would have us believe) is sophisticated enough to allow smaller diameters, and compensation for (periodic) irregularity with PEC"

The accuracy of the machining is certainly much improved on the smaller mounts, and periodic errors reduced, but flexure is still fundamentally a function of the materials used, the mass of the load carried (and the torque applied) and the dimensions.

I think I'm destined for the G11. Then next up from that is an AP Mach1 and that is overkill.

[Alchemy]

the mak and the 5 inch would be fine on the G11.

i have a 12 inch newt and 80mm ed guidescope plus accessories on mine , it is overloaded but functions just ok for imaging. i will admit id be better off with a lighter scope arrangement. note im shooting at f5 which is only 1500mm .

13 inch cassegrain.. might be a similar weight. but finding stuff without goto would be slow ... still that might be half the fun and challange.