William Optics GT81 Triplet Arrives
Posted 03 October 2011 - 05:40 PM
Posted 03 October 2011 - 05:43 PM
I had planned to use one of my extra dovetail bars to start using it but I'm not sure that's in the cards after all. I guess I may really be forced to use rings but I really wish I didn't have to do that.
Posted 03 October 2011 - 06:02 PM
Strange also that the camera tripod hole is below the recess for the dew cap. So it's impossible to attach a long dovetail to the OTA. Why did they do this and why didn't they at least include an L-bracket? Does anybody sell L-brackets until I get scope rings? Thanks for any info.
Posted 03 October 2011 - 06:30 PM
I'm not sure where you can find a an L-bracket at, but if you're sorta handy with tools I think you could make a L-bracket out of some wood and a couple of bolts. Just an idea.
Posted 03 October 2011 - 07:11 PM
I agree, the thought that went into it wasn't from a users point of view, more it was designed I reckon in a 3D computer program, but someone that hadn't actually used the scope.
Glaringly obvious is the fact that the tripod head attaching to the 1/4x20 hole is not going to work. So you buy tube rings (I did, bought the W/O tube rings), and it sort of works.
But again, that 3D program didn't think about the dovetail, or the point of balance, so when you factor all that in and then think you'll rotate that focuser, you can't. See what I mean?
Sound likes I dislike it? No way, it is a great scope, but you have to be prepared to live with the R&D short-comings, and there are a few of them.
My only other beef is the DDG, in my case it either slips, or is that tight it hardly moves. When I image I use a Feather Touch, so get around this, but it will be the end of the scope sooner or later. At least I don't suffer image shift with the F/T like I do with the DDG.
Posted 03 October 2011 - 07:16 PM
Posted 03 October 2011 - 10:48 PM
The handle is a great idea.
Posted 03 October 2011 - 10:56 PM
The dovetail is also slightly curved so it hugs the curvature of the tube quite nicely. Quite solid.
Posted 04 October 2011 - 01:28 AM
Posted 04 October 2011 - 04:15 AM
The balance point is located close to the middle of the saddle plate but this will depend on the weight of the camera/filterwheel gear attached to the focuser.
Posted 04 October 2011 - 04:17 AM
Posted 04 October 2011 - 07:55 AM
Posted 04 October 2011 - 08:43 AM
Posted 04 October 2011 - 11:48 AM
Congrat's on the new scope Pierre - hope it works out.
If you have play in the focuser rotating mechanism, you can adjust it out with the 3 black recessed allen screws that are closest to the tube. I had to tweak mine, but once I got it right there's been no further adjustment needed.
Posted 04 October 2011 - 01:53 PM
Posted 04 October 2011 - 03:42 PM
As an imaging scope the GT-81 fitted with the Astro-Tech AT2FF field flattener or using the Tele Vue TRF-2008 0.8x Photo Reducer Flattener produces excellent star images across the APS size CCD chip.
Posted 04 October 2011 - 03:53 PM
Posted 04 October 2011 - 08:54 PM
Last night imaging the moon with my Canon 5D for the first time all went well with the focuser until the end of my session. When I went to rack the focuser back in with camera/extention tube still attached the focuser would not rack in. Something has loosened up causing the focuser to slip. I have been viewing with a TV 31 Nagler w/o problems which with the diagonal is heavier than the camera.
So what adjustments do I need to make. WO has published a detailed instruction manual for the 3" DDG on their website. It looks like item "B" hex screw (M5) is the first place to start with to adjust.
Has anyone else had their focuser not be able to rack in with a load when the scope is not horizontal? If so, what adjustments did you make?
Posted 04 October 2011 - 09:48 PM
Posted 04 October 2011 - 10:07 PM
Posted 04 October 2011 - 10:12 PM
Posted 04 October 2011 - 11:54 PM
Thanks for the tip. Focus lock screw is in non tension state. I tightened the tension hex set screw without going too tight, and that has solved the problem. Upon close inspection I see that the single focus knob wobbles slightly as the focuser is rotated. The dual speed knob does not do this. So I need to see if another type of adjustment is required to the bearing block or something.
Posted 07 October 2011 - 11:07 AM