Astromart Reviews - William Optics FLT110mm f7 TMB designed ...

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Astromart Reviews - William Optics FLT110mm f7 TMB designed triplet and matching field flattener • Terms of Service • Privacy Policy • Help & FAQ • Astronomy Links • User Profiles • Top Users List • Sponsors • Supporters • RSS Feeds Who wins? Florida Ohio State View Comments (4)... Previous Polls... The finish of the optical tube is white pebble, giving the impression of long lasting durability and stability. Mechanics of the focuser are impressive and one gets the impression it is possible to tune it to the very last bit. The focuser has two rotating mechanisms, one for the complete focuser, and one at the end of the drawtube for an extra camera rotation. Perhaps a bit of overkill, but still, if you want to rotate the camera independent from the focuser knobs, it will be possible. A little warning should be made here. Loosening the focuser rotation mechanism setscrew too much will cause the entire assembly to tilt suddenly in the rotation holder. I haven• tried to unlock the setscrew completely and see whether there is a risk of dropping the entire focuser, but ok, if you know that care is needed, I don• see a major issue here. Unlock the setscrew just enough so you can rotate the focuser. If you use heavy accessories you may want to screw in the plastic setscrews a bit with a flat screwdriver as WO suggested to me. By default it ships quite loose. This does help in fixing the issue, but it not the same quality feeling as the Takahashi TOA rotator or the 3.5?Feathertouch focuser rotation mechanism though. So, rotate first, fine focus then is the message here. Anyway this is a policy I am using with all rotation mechanisms on focusers. The focusing mechanism itself is buttery smooth and stable for visual and DSLR use. I could not detect imaging shift while focusing. The dual speed mechanism is a blessing for every telescope and in this case very well done. It certainly feels more like the well known Feathertouch quality than the one of the Takahashi TOA dual speed knob (which I think could be made better). The focuser locking screw does what it has to do: lock the focuser in place when needed. But again a little warning?by default the tension on the focuser is NOT sufficient for an SBIG STL camera. You need to lock the hex screw underneath the focuser to avoid a potential heart attack when you see your SBIG slipping ?fast! Fortunately there is an internal mechanism of the focuser which prevents the drawtube from falling out, but you don• want to take any risk with your expensive camera. It is a bit difficult to find the right balance point between adding friction for a heavy STL camera and still keeping smoothness with the 10-1 reduction. Too much friction and the focusing knob will start slipping; too little friction and your camera will slip. When the hex screw is tightened for the STL, the standard locking thumbscrew became quite useless, it does not lock anything anymore and I was relying on the hex screw friction alone. William Optics suggested replacing the thumbscrew with a longer one so that it locks better under heavy weight. They also mentioned using not only the large hex screw to put additional friction, but also the two other (smaller) ones, again with the drawtube fully racked out when performing this operation! Basically when doing all this, one should find a good combination. At least it works for my STL. On the image below you can see the camera sitting cozy held by friction on a vertically placed tube. Focusing is still possible. I can• show this so you will need to believe me on that one. http://www.astromart.com/articles/article.asp?article_id=523 (2 of 19)1/6/2007 10:54:28 AM
Astromart Reviews - William Optics FLT110mm f7 TMB designed triplet and matching field flattener http://www.astromart.com/articles/article.asp?article_id=523 (3 of 19)1/6/2007 10:54:28 AM The drawtube itself is engraved with a scale. Handy to more or less raw focus cameras after you have determined the needed distance once. It will not be good enough for repetitive CCD or DSLR work, but you have a starting point for fine focus very fast. I remember that with my AP focusers, I marked the drawtube with a thin hairline using a razorblade. No need to get the razor out with this focuser. The 2?adapter only has one setscrew. I don• like that kind of system, especially since the 2?WO adapter is a bit on the wide side and definitely not the best part of the focuser. My Herschel wedge for solar observations did not sit very comfortable in the focuser, was difficult to lock in place and hard to keep it square. I do have a Baader multifunction 2?adapter which happened to fit the 4 inch William Optics focuser, so I replaced the original 2? adapter with the Baader one (which is more robust and has two setscrews to lock accessories) to get a much better fit. You can see the Baader adapter on the STL setup picture. OK, I am being picky on these things. A scope may be optically excellent, but if you cannot mount accessories square, you reduce the potential. It doesn• cost an arm and a leg to make a good adapter like the clamp ring style of the 3.5 inch Feathertouch or the 3 setscrews of an Astro-Physics focuser. There is one thing I regret with the WO 4 inch focuser. It has the same end threads as the Takahashi focusers, but female, whereas the Takahashi has male threads. Too bad, as it would have opened the door for use of all Takahashi accessories like their fabulous reducer-correctors! Anyway, I had an adapter made locally by Eric Moerman to convert to Takahashi threads, so I can use their 2.7?reducer-corrector for photographic testing of the FLT110. It should be easy for William Optics to add such an adapter to their product line. As a matter of fact, standardizing connections in telescope land would be a great thing in general for consumers?br /> Perhaps this all sounds a bit negative on the focuser. For many purposes it will be excellent, but one should know it does have its little shortcomings which you may need to look after with heavy accessories. A few of these shortcomings could have been factory solved easily. The tube itself is well baffled and dark inside for high contrast. Looking from the back through the telescope, I do not have the impression any of the baffles would vignette the light cone, although the first baffle on the front end is pretty close.
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