I recently moved my
AP rig over to my Explore Scientific fracs, an ED12CF and an ED80. The hardest part is generally the
EAF focuser but fortunately, the bracket fit perfectly, so all I had to do was get four 25 mm long M4/0.70 screws from the hardware store, and it fit almost out of the box. I made the last couple of mm fit by pushing a quarter underneath the bracket as I did not have 4 washers to make it fit perfectly. This worked for both the ED12CF and the ED80 because they have the same stock focuser.
First off, here is the problem; look at the elongated stars at the lower right. This was for the ED80, the ED127CF had round stars. Clearly there is some misalignment that is caused either by the focuser or by the lens (that I will not touch except possibly for the pull-push alignment screws). It can also be caused by the
ES field flattener, I have the 45 mm backfocus version (the current one is 55 mm).
There have been a lot of negative comments about the
ES stock focuser but IMHO that is not justified. The key is to identify all 6 adjustment screws, 4 of which are hidden. The two visible ones are the regular tightening screws on the outside, no need to discuss those. The first pair of hidden screws are underneath the focuser housing (the part that contains the turn screw). When taking the 4 screws out (they may have Loctite on them, so the first time is the hardest), there are 2 adjustment screws on both side that you can tighten. If you can get the rotation collar off, there are two more screws there that push down on the Teflon sliders inside. I was able to get it off for my ED127CF IIRC but today, not for my ED80. However, if you take the handle off there is a big enough hole that, when turning the rotation collar, they show up, and you can adjust them through that hole. Note that these screws are so far up that they only have effect if the focuser tube is underneath them. You may have to get an extra ring to make it so, depending on your focus position. Anyway, using these 4 hidden screws and the 2 visible ones, everything can be made as tight enough to carry a hefty camera rock solid. Try this first before spending a fortune on a Moonlite.
To fix the alignment I cut a paper disc that fit right the outside rim of the lens and marked the center as accurately as possible. Then I inserted the Howie Glatter laser in the focuser with the 3 extension rings that I needed. The more rings the better for this, I presume. I loosened up all 4 screws of the focuser collar. There is one meant to be used to rotate the collar that can be operated with your fingers. The other three are thumb screws. I don't know if these thumb screws are meant to be tightened, or if they are adjustment screws. As the whole focuser was flopping all over the place when the screws were loose, I tightened them all while looking at the laser dot on the paper disc. It took a while but eventually I got the laser focused exactly on the dot to the millimeter. Just 1 mm makes a significant difference, considering that an APS/C sensor is 25x16 so that''s a substantial part (the camera is about equally far away from the collar as the lens).
The last part that can cause tilt is the
ES FF that, in my case, could not be pushed up against the outer ring to align it. I had to pull it out 15 mm and tighten it with the screws, which can cause tilt, I think. I made a little cardboard collar 14 mm wide and slid it tightly around the
FF. Then I pushed it up against the ring. That should hopefully be aligned well now.
I haven't tried it yet but will ASAP. The last thing that I may need to do is to try other ring configurations on the camera because I am not sure if the 45 mm backfocus is cast in stone. It worked for my ED127CF at
F/7.5 but my
F/6 ED80 may need a different distance.
... Henk.
Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80,
Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall,
Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS,
DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles,
Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50,
Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK,
Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17",
Website:Henk's astro images