MEF-2 focuser

[Sunshine]

I’m not sure what to think about the MEF2 focuser, I have temporarily removed it to adjust the tension and re grease it as it was rough. Unfortunately when I re install it, it seems to misbehave again, it spins smoothly and seems fine when I have it in hand but it seems to become very stiff again when I install it. Not sure why, are there any tricks and tips for using this thing? any member mods around? Thanks.

[F15Rules]

Hi Sunshine,

I'm not aware of an Mef-2 microfocuser, but if you are referring to your Tak FS128, its an MEF-3 unit, offering a 7:1 gearing reduction.

Have a look at the thread linked to below from several years ago on here..just click on the title text "Tak MEF3 microfocuser fe.."

I found the information shown in this thread to be very helpful when fitting my own FS128 with this unit. It works really well. After about 3 years of use I have only had to re-adjust it once.

Bear in mind that you need to make sure the original 2.7" focuser may also need to be adjusted as well.

 

 

I hope that helps😉..

Dave

[F15Rules]

Just to add, in case it helps with adjustments to your original 2.7" focuser unit, the following instructions were added to a CN thread by poster "TomCody"..

As an addendum to my post above, here is a more complete description of adjusting the Tak 2.7" focuser:

"To adjust it properly, you must first remove the cover from the rack and pinion. by unscrewing the small flat chrome screw on the bottom of the focuser (use a bent paper clip in the shape of a U or a pair of sharp tipped tweezers as a spanner wrench to loosen that chrome screw. Then remove the cover over the rack gears and LOOSEN the two screws that tighten the tension clearance on the gears ( you will need a small #3 Phillips head screw driver, get the clearance loose and sloppy, but still able to turn the focuser knobs and move the focuser in and out.

(WHY? The three screws along the top of the focuser adjust the play in the focuser tube by pressing the tube against the bottom of the focuser housing, if you do not loosen the pinion gear shaft, you are just pressing the focuser tube against the pinion gear, not the bottom of the focuser housing).

NOW adjust the three small allen hex screws along the top of the focuser (use a tiny drop of acetone to loosen the glue holding them) they take a 1.5mm allen wrench. Adjust the three screws while turning the focuser knob in and out until all slop in the focuser tube is removed and the tube still slides in and out without binding. (Start with the middle screw, then the front screw, then back screw).
Now go back and tighten the two phillips screws on the rack until you do not feel any slop when reversing direction of the focuser knob AND the rack moves smoothly without binding, (DO not over tighten this adjustment as it will cause rough movement and binding of the gears, also slop will only be felt as looseness or back lash in the gears and not hurt the scope movement, so a little loose is beter than too tight).
Replace the cover and screw and you are done.

EDIT: A few more points, the glue used to secure the three screws along the top of the focuser will re-dry in about an hour (if you don't use too much acetone to loosen them, if the stay loose? just use a drop of clear nail polish to re-secure them."

HTH,

Dave

[Sunshine]

13 minutes ago, F15Rules said:

Hi Sunshine,

I'm not aware of an Mef-2 microfocuser, but if you are referring to your Tak FS128, its an MEF-3 unit, offering a 7:1 gearing reduction.

Have a look at the thread linked to below from several years ago on here..just click on the title text "Tak MEF3 microfocuser fe.."

I found the information shown in this thread to be very helpful when fitting my own FS128 with this unit. It works really well. After about 3 years of use I have only had to re-adjust it once.

Bear in mind that you need to make sure the original 2.7" focuser may also need to be adjusted as well.

 

 

I hope that helps😉..

Dave

That’s what I meant to say, MEF-3, thanks.

[Sunshine]

1 minute ago, F15Rules said:

Just to add, in case it helps with adjustments to your original 2.7" focuser unit, the following instructions were added to a CN thread by poster "TomCody"..

As an addendum to my post above, here is a more complete description of adjusting the Tak 2.7" focuser:

"To adjust it properly, you must first remove the cover from the rack and pinion. by unscrewing the small flat chrome screw on the bottom of the focuser (use a bent paper clip in the shape of a U or a pair of sharp tipped tweezers as a spanner wrench to loosen that chrome screw. Then remove the cover over the rack gears and LOOSEN the two screws that tighten the tension clearance on the gears ( you will need a small #3 Phillips head screw driver, get the clearance loose and sloppy, but still able to turn the focuser knobs and move the focuser in and out.

(WHY? The three screws along the top of the focuser adjust the play in the focuser tube by pressing the tube against the bottom of the focuser housing, if you do not loosen the pinion gear shaft, you are just pressing the focuser tube against the pinion gear, not the bottom of the focuser housing).

NOW adjust the three small allen hex screws along the top of the focuser (use a tiny drop of acetone to loosen the glue holding them) they take a 1.5mm allen wrench. Adjust the three screws while turning the focuser knob in and out until all slop in the focuser tube is removed and the tube still slides in and out without binding. (Start with the middle screw, then the front screw, then back screw).
Now go back and tighten the two phillips screws on the rack until you do not feel any slop when reversing direction of the focuser knob AND the rack moves smoothly without binding, (DO not over tighten this adjustment as it will cause rough movement and binding of the gears, also slop will only be felt as looseness or back lash in the gears and not hurt the scope movement, so a little loose is beter than too tight).
Replace the cover and screw and you are done.

EDIT: A few more points, the glue used to secure the three screws along the top of the focuser will re-dry in about an hour (if you don't use too much acetone to loosen them, if the stay loose? just use a drop of clear nail polish to re-secure them."

HTH,

Dave

Thanks, I have seem this thread and used it to adjust the focuser on my 102, some alcohol and clear nail polish are what i used to loosen and then resecure the three small screws on top of the focuser, I will be doing the same with the 128. It’s a delicate procedure getting the right amout of friction on the focuser tube.

[Sunshine]

11 hours ago, F15Rules said:

Just to add, in case it helps with adjustments to your original 2.7" focuser unit, the following instructions were added to a CN thread by poster "TomCody"..

As an addendum to my post above, here is a more complete description of adjusting the Tak 2.7" focuser:

"To adjust it properly, you must first remove the cover from the rack and pinion. by unscrewing the small flat chrome screw on the bottom of the focuser (use a bent paper clip in the shape of a U or a pair of sharp tipped tweezers as a spanner wrench to loosen that chrome screw. Then remove the cover over the rack gears and LOOSEN the two screws that tighten the tension clearance on the gears ( you will need a small #3 Phillips head screw driver, get the clearance loose and sloppy, but still able to turn the focuser knobs and move the focuser in and out.

(WHY? The three screws along the top of the focuser adjust the play in the focuser tube by pressing the tube against the bottom of the focuser housing, if you do not loosen the pinion gear shaft, you are just pressing the focuser tube against the pinion gear, not the bottom of the focuser housing).

NOW adjust the three small allen hex screws along the top of the focuser (use a tiny drop of acetone to loosen the glue holding them) they take a 1.5mm allen wrench. Adjust the three screws while turning the focuser knob in and out until all slop in the focuser tube is removed and the tube still slides in and out without binding. (Start with the middle screw, then the front screw, then back screw).
Now go back and tighten the two phillips screws on the rack until you do not feel any slop when reversing direction of the focuser knob AND the rack moves smoothly without binding, (DO not over tighten this adjustment as it will cause rough movement and binding of the gears, also slop will only be felt as looseness or back lash in the gears and not hurt the scope movement, so a little loose is beter than too tight).
Replace the cover and screw and you are done.

EDIT: A few more points, the glue used to secure the three screws along the top of the focuser will re-dry in about an hour (if you don't use too much acetone to loosen them, if the stay loose? just use a drop of clear nail polish to re-secure them."

HTH,

Dave

Thanks, I have seem this thread and used it to adjust the focuser on my 102, some alcohol and clear nail polish are what i used to loosen and then resecure the three small screws on top of the focuser, I will be doing the same with the 128. It’s a delicate procedure getting the right amout of friction on the focuser tube.

[Sunshine]

Spent the better part of the evening mucking around with the Tak focuser making small adjustments while incorporating the MEF-3. Though I am not thrilled about the MEF3 I got everthing working more or less as smooth as can be, the MEF has a friction clitch ring which is held to the selected friction for the microfocuser knob by a tiny set screw. One would loosen said set screw and using the hex key while still inserted to turn the ring clockwise or counterclockwise for more or less friction then tighten the screw, check friction on the microfocuser knob and either repeat the process or leave it be if youre happy with the friction. 
 

One lesson I learned was to check the friction with your heaviest eyepiece with the scope pointed up near zenith, this ensures your selected friction will be enough to rack the focuser in with the microfocus knob without slipping. When I first set the friction while the scope was more or less horizontal it worked great, then I pointed the scope near zenith only to realize the microfocus wheel slipped while trying to rack the focuser in with my 5mm XW in the diagonal.  
 

Thankfully, the friction ring can be adjusted easily with the focuser installed and I was able to get the friction so it would haul my XW uphill without issue. One thing I don’t like about this dual speed focuser is that when focusing in while scope is pointing up the micro focus knob feels oike a crayford (not a fan of crayfords) It’s the rubbery backlash when letting gonof the wheel when scope is looking up and the focuser is at maximum stress. Letting go of the microfocus wheel in this circumstance causes a rubbery sort of backlash which feels as though the focuser moves back out again by a hairs worth, not a huge concern but I wish it weren’t that way. Under the stars will be real test of this focuser, I do hope O get on with it as dual soeeds are handy for doubles, but then again, I haven’t used one before for doubles, just a new toy to try out.

Edited December 18, 2023 by Sunshine

[JeremyS]

14 hours ago, Sunshine said:

Thanks, I have seem this thread and used it to adjust the focuser on my 102, some alcohol 

I find alcohol makes most things better 👍🏻