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EM 10 Page
Once I had decided I needed a good mount I reliased that portability was going to be a prime issue. I need to set my gear up every night and store it inside. My choice was between the Losmandy GM8, Vixen GPDX and the Tak EM10. I saw an offer on the EM10 with the Temma Pc Jnr and went for it.
The mount is a beautifully made item and when combined with the wooden tripod it really looks the part. Its light enough to move around in one piece and sturdy enough to hold an 8" SCT or 6" Newtonian. I limit the payload to 20 lbs and it does OK.
I've had lots of challenges getting the system to work but it works just fine now and I'm delighted with the performance. Art and Fred at TNR were a source of much help and Art even talked me through some minor surgeries on the phone. Nick at Tru-Tek was also a great help.
Here are some of the issues I found.
High Latitude
I live at 53 Deg N and the mount is only good for 50 or 51 so I was a bit stumped when I first took it out of the box. The solution was simple enough. Extend the front tripod leg to compensate. Problem solved with no adverse impact to alignment.
Polar Alignment
The polar scope works fine I've never had any field rotation in 10 minute exposures at up to 1500 mm focal length. Just make sure that if the mount is leveled with the bubble then the clock starts at the bottom. I've heard of some scopes where the reticule has slipped. If you aren't well aligned the guiding errors will gradually increase and you may also see field rotation. I spent about 2 months several degrees from the pole until I worked out what was going on. Short focal lengths can hide field rotation in 5/10 minute exposures.
Dec Backlash
It seems to be a fact of life Tak mounts can have large backlashes up to 6 or so seconds. That's where mine is and I can't find a fix I've changed the motors meshed the gears, the works. Truth is it doesn't matter as DEC guiding should only go in one direction. The key is to ensure you never overshoot in DEC. For longer focal length work I made up a cable which ensures DEC only drives in one direction (I cut both DEC wires and only join up the one I want). The only time I've found backlash to be a real problem is when guiding at longer focal lengths with Astro Art version 2.0 which only guides one axis at a time. I believe Maxim solves this problem. My ST4 has no problem guiding.
DEC Jumps
I had a period of a few months when the mount suddenly started to jump in Dec while guiding. I ended up taking the whole thing apart and trying to turn the DEC gear with my finger. It was very stiff and I found that the Temma encoder was binding on the worm, a quick adjustment and all was fine. The backlash also dropped a bit.
No Movement In DEC
I've had a couple of occasions when there was no motion in the DEC axis. There were two reasons for this: the first is simple and more common the clutch was not closed; the second was that the worm had slipped out of place. The latter was remedied by loosening the top plate (don't take it off) and pushing it forwards to make sure the gear/worms mesh.
Poor Guiding
The most common cause of this is that the mount is unbalance, I always weight mine against the direction of travel ie. on the east. The other reason is that the gears are not well enough meshed. You can open up the silver viewing ports on the head and watch the gears to see how well meshed they are.
Power Supply
I always use a 12V battery or two in series at 24V, one can use a power supply but I think the mount is sensitive to surges so I never take the risk.
Computer Control
I've used Richard Lawler's plug in for the sky and it works just fine. Telescope tracker works well but it lacks the functions of the sky. I never use the zenith initialisation I simply sink on a star near where I want to be. Also I never allow the mount to flip I just do it manually.
Scope Hitting the Tripod
If you have anything longer than a small refractor or SCT you will find the scope hits the tripod legs near the zenith. There are two solutions to this: use a pier or buy the TAK tripod extension (you can see mine in the equipment page). If you already have the tripod go for the extension its cheaper.