{"id":25,"date":"2021-08-23T15:41:31","date_gmt":"2021-08-23T14:41:31","guid":{"rendered":"http:\/\/knowhere.myqnapcloud.com\/WordPress\/?p=25"},"modified":"2023-11-16T00:25:37","modified_gmt":"2023-11-16T00:25:37","slug":"adjusting-william-optics-flt-91-focuser","status":"publish","type":"post","link":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/2021\/08\/23\/adjusting-william-optics-flt-91-focuser\/","title":{"rendered":"Adjusting William Optics FLT 91 Focuser"},"content":{"rendered":"

Note: As can be seen from the comments below, this information seems to also applies to WO FLT132 IV.<\/em><\/p>\n

A while back I purchased a William Optics Fluorostar FLT 91 Telescope as on paper the specs seemed to be exactly what I was looking for. This particular scope was also supposed to be checked and tuned. Initially everything did feel okay but it didn\u2019t take long for me to start noticing some issues with the focuser. Right out of the box it had some \u201crough spots\u201d on the length of the travel. A little bit of grease on the rack and pinion system took care of that.<\/p>\n

With visual observations everything seemed to be okay with a 2\u201d diagonal and some 1.25\u201d eyepieces. It wasn\u2019t until I swapped to my imaging setup when the more annoying issues started to show up. The setup was a HoTech SCA Field Flattener + 5×2\u201d slot EFW + Atik 383L+ spacers. This was a lot more weight hanging off the focuser than I had with the visual setup.<\/p>\n

First I noticed a slight horizontal play when I gave it a little wiggle as soon as the focuser was racked out even a little bit. Vertically it felt okay. Or so I thought. Quick email to WO and I was told to adjust the focuser tension using these two screws:<\/p>\n

\"\"<\/p>\n

For several nights I kept adjusting the focuser tension and every time I thought I got it good the focuser was too stiff to operate. Not good. Also the screw in the second photo above didn\u2019t seem to do much even if I tightened it a tad more than I was comfortable with. It seemed to be more about the bigger screw and the tension of the pinion assembly at the opposite side. While doing all this I noticed another issue with the focuser. It seemed to tilt up and down depending which way you turn the focus knobs. I thought this can\u2019t be right on a \u00a32k scope\u2026<\/p>\n

Eventually I decided to take the focuser apart and really see how it\u2019s been built and why I can\u2019t adjust it properly. To do this, first remove the whole focuser rotator assembly which just unscrews anti-clockwise.<\/p>\n

\"\"\"\"<\/p>\n

Next step is to remove the focuser knob assembly which is held in place with the two socket head bolts in the middle. You might want to loosen up the four small grub screws first that are stabilising the assembly against the focuser body as they\u2019ll need to be adjusted upon re-assembly again.<\/p>\n

\"\"\"\"<\/p>\n

Finally to remove the focuser body you\u2019ll need to remove the three brass screws and the thumb screw around it (On the table next to the red screwdriver below).<\/p>\n

\"\"<\/p>\n

And whaddaya know\u2026 This reveals another tension adjustment screw at the front of the focuser body. Why they have decided to hide this inside the scope with no access from the outside is beyond me. Seems like a bit of a design flaw… I am tempted to drill a small hole on the top of the body just big enough so I can adjust the screw with an allen key without dismantling everything again. This screw was rather loose on my scope and caused all the troubles I mentioned above.<\/p>\n

It is now possible to push the focuser tube through the body so that the teflon sliders inside can be inspected. Looking at it from the inside I really don\u2019t think the second screw in the first photo in this document can be used to adjust the tension as advised by WO. I think it\u2019s there just to stop the plastic tension bar sliding out the assembly. The tension is adjusted using the two bigger similar looking screws at the front and back of the body. Using these I was able to have a tight fit without any play even with the pinion assembly removed while still being able to move the tube in and out without too much effort.<\/p>\n

With all this done it was time to put it back together again which is basically just the reverse of disassembly. Care must be taken not to overtighten anything. Special care must be taken with the three brass screws and the thumb screw holding the focuser body to the telescope as they have plastic tips on them pressing against the groove on the metal. They need to be snug but don\u2019t go too crazy with them.<\/p>\n

When re-installing the pinion assembly start by tightening the two socket head bolts just tight enough so the focuser knobs feel nice and smooth. Then snug up the four small grub screws to prevent it from moving about. Hope this helps!<\/p>\n","protected":false},"excerpt":{"rendered":"

Note: As can be seen from the comments below, this information seems to also applies to WO FLT132 IV. A<\/p>\n

Continue readingAdjusting William Optics FLT 91 Focuser<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":33,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_lmt_disableupdate":"no","_lmt_disable":"no","ngg_post_thumbnail":0,"footnotes":""},"categories":[2],"tags":[5,4,6,3],"class_list":["post-25","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-telescopes","tag-flt-91","tag-fluorostar","tag-focuser","tag-william-optics"],"modified_by":"nightowl","_links":{"self":[{"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/posts\/25","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/comments?post=25"}],"version-history":[{"count":8,"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/posts\/25\/revisions"}],"predecessor-version":[{"id":549,"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/posts\/25\/revisions\/549"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/media\/33"}],"wp:attachment":[{"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/media?parent=25"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/categories?post=25"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ironmountain.halley-arctic.ts.net\/WordPress\/wp-json\/wp\/v2\/tags?post=25"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}