Micro Focuser for Takahashi 100 DZ

[johnturley]

Having recently acquired a Takahashi 100 DZ, I must confess to being a bit disappointed with the focusing mechanism, I found it to be very stiff even after slackening off the Drawtube clamp, and difficult to achieve correct focus, having only coarse focusing. I'm surprised that at this price point it doesn't come with a dual speed focuser, especially as most non-premium 100mm Refractors costing less than half the price, come with a dual speed focuser, and in order for me to carry out a meaningful comparison of the performance with my other refractors, I consider that a fine focus mechanism is essential. 

As I understand there are two Precision Focuser kits available for the Takahashi FC 100 Refractors, the genuine Takahashi MEF3 Micro Edge Focuser available from FLO at £247, or the More Blue Precision Focuser Retrofit Kit, currently in stock at FLO at £195.

I would be interested to receive any recommendations from observers that have fitted either of these fine focusing kits, including ease of fitting.

John 

[Mr Spock]

I have a MEF3 and fitting is easy taking just a couple of minutes.

I had similar focuser issues. It was way too stiff making focusing impossible. When I fitted the MEF that was initially useless as it was too 'bouncy'. I did manage to loosen the focuser a little by adjusting the three grub screws but eventually it went back to FLO for adjustment. It's still a bit stiff and the fine focuser a little bouncy but is useable.

I've gone to the (great) expense of ordering a Feathertouch (3-4 months waiting list). Shame such a fine scope is blighted with a poor quality focuser though.

[John]

The focuser on my FC100-DL was rather stuff when it was new. I found that I could adjust the focuser to make it good to use. The process is documented somewhere online - I'll see if I can find a link. I then found the DL focuser fine to use for a few years but I came across a Feathertouch micro pinion upgrade at a reasonable cost so added that and now the focuser feels just the same as the full FT on my TMB/LZOS 130mm. I've not tried either the Tak or the Moreblue upgrades.

 

 

[LandyJon]

7 minutes ago, Mr Spock said:

I've gone to the (great) expense of ordering a Feathertouch

They are well known as the best money can buy, precision engineering and beautifully crafted.

Dena will do her best to get one to you as quick as possible, drop her an email.

https://www.starlightinstruments.com/product/mpa-tak2-5-micro-pinion-assembly-takahashi-retrofit-2-5-diameter-focusers-fits-takahashi-sky-90-fcl-90-and-fc-100-telescopes/

[MartianHill]

I found adjusting the two screws evenly and slightly on the focuser pressure plate on the underside of the focuser allowed very good adjustment control for the focus tension.

[johnturley]

1 hour ago, MartianHill said:

I found adjusting the two screws evenly and slightly on the focuser pressure plate on the underside of the focuser allowed very good adjustment control for the focus tension.

There is a small round metal plate under the focuser, presumably this needs to be removed to expose the screws.

John

[Franklin]

One thing that I've noticed with regard to these "add-on" fine focusers that attach to the original pinion shaft, is that they are fitted to the scope via a plate which in turn is fixed using the screws that adjust tension on the original R&P mechanism. This can cause problems and make the action "lumpy" and "gritty", for example if the pinion shaft is not perfectly true, which can happen if it's taken a knock, then this slight bend would be unnoticeable with the original focuser knobs which would just turn but with the "add-on" the fine focuser side is now fixed to the plate and any bend in the shaft will cause undue pressure and drag, again causing issues. Not the best design imo really.

[John]

This guidance was posted by @mikeDnight on the CN forum. It refers to the FC100-DC that he had at that time:

The stiff focuser problem is easily resolvable! I noticed in a side by side comparison with a FL102 that my DC focuser was really quite stiff, so after giving it some consideration, I eventually plucked up the courage to try and rectify the problem. Now the focuser is buttery smooth and easy to move.

First remove the pinion by unscrewing the top cover and then the two screws on the brass plate underneath. It's a simple process and you can do no harm.

Next, remove the locking nut on top of the focuser. Now there are three small grub screws also on top of the focuser. The holes for these grub screws may be filled with glue to prevent tampering. The glue however is quite soft and a fine Allen key can be pushed through it. Unwind each of the three grub screws equally until the drawtube slides freely by hand. Then gently retighten each grubscrew evenly and a fraction at a time, until the drawtube feels firm but still easily moveable. Uneven tightening will result in image shift! Trial and error may be necessary to get it just how you want it.

Next, reattach the pinion by screwing the two screws holding the brass plate back on focuser. Don't overtighten these screws! Then reattach the pinion cover.

 

Mike

[Franklin]

38 minutes ago, John said:

This guidance was posted by @mikeDnight on the CN forum. It refers to the FC100-DC that he had at that time:

This is pretty much the same advice that I've seen on adjusting the Vixen R&P which is a similar design to the Takahashi. The idea is to allow the drawtube to run freely on the two lower rails, just being held there by the upper grubscrews and Teflon strip, rather than the pinion gear pressing up against the rack.

[John]

9 minutes ago, Franklin said:

This is pretty much the same advice that I've seen on adjusting the Vixen R&P which is a similar design to the Takahashi. The idea is to allow the drawtube to run freely on the two lower rails, just being held there by the upper grubscrews and Teflon strip, rather than the pinion gear pressing up against the rack.

Yes it is very similar. I use this guide for my Vixen focuser:

Vixen Focuser Adjustments (miltonhill.us)

[MartianHill]

2 hours ago, johnturley said:

There is a small round metal plate under the focuser, presumably this needs to be removed to expose the screws.

John

Yes

[John]

1 hour ago, Franklin said:

One thing that I've noticed with regard to these "add-on" fine focusers that attach to the original pinion shaft, is that they are fitted to the scope via a plate which in turn is fixed using the screws that adjust tension on the original R&P mechanism. This can cause problems and make the action "lumpy" and "gritty", for example if the pinion shaft is not perfectly true, which can happen if it's taken a knock, then this slight bend would be unnoticeable with the original focuser knobs which would just turn but with the "add-on" the fine focuser side is now fixed to the plate and any bend in the shaft will cause undue pressure and drag, again causing issues. Not the best design imo really.

This is true. The instructions for the Feathertouch micro pinion unit mention this and describe testing the pinion shaft to check it is straight. There are some useful photos in on the first page of this which show how the Tak FC pinion is held in place. Might be useful even if not fitting an FT:

Microsoft Word - MPA-TAK Instructions.doc (starlightinstruments.com)

[johnturley]

8 minutes ago, MartianHill said:

Yes

Wasn't sure how to remove the metal plate, do you need a special tool, I assume that its screwed in.

John 

[MartianHill]

@johnturley

Yes it’s screwed in , I used two small Allen keys clamped between 2 pieces of wood, taking care not to slip

Edited November 26, 2023 by MartianHill

[Franklin]

18 minutes ago, johnturley said:

do you need a special tool

Lens spanner.

[Franklin]

41 minutes ago, John said:

I use this guide for my Vixen focuser:

Vixen Focuser Adjustments (miltonhill.us)

Have you figured out why it says NOT to touch the middle grubscrew?

[johnturley]

1 hour ago, Franklin said:

This is pretty much the same advice that I've seen on adjusting the Vixen R&P which is a similar design to the Takahashi. The idea is to allow the drawtube to run freely on the two lower rails, just being held there by the upper grubscrews and Teflon strip, rather than the pinion gear pressing up against the rack.

The adjustment screw holes on the side of the Vixen focuser actually look more similar to those on the Esprit 150 focuser, and not at all like on the Tak 100 DZ, where there aren't actually any adjustment screw holes on the side of the focuser.

Incidentally there were no instructions for adjusting the focuser in the manuals that came with either the 100 DZ or the Esprit 150.

John

[The60mmKid]

Has anyone used a Baader Steeltrack focuser with a Tak? They're such darn good focusers (I had the Newtonian version), and they're priced competitively with the Tak fine focusers.

[John]

33 minutes ago, Franklin said:

Have you figured out why it says NOT to touch the middle grubscrew?

Nope. You know what happens when there is a screw, bolt or knob labelled "do NOT touch" though 😈

[Franklin]

Well I don't know for sure because I haven't succumbed to that but I would guess that the outer grubscrews are flat-headed for applying pressure to the Teflon strip and the central grubscrew is pointed and actually screws into the Teflon strip to prevent it from slipping out of place.

[John]

1 minute ago, Franklin said:

Well I don't know for sure because I haven't succumbed to that but I would guess that the outer grubscrews are flat-headed for applying pressure to the Teflon strip and the central grubscrew is pointed and actually screws into the Teflon strip to prevent it from slipping out of place.

That sounds quite logical 👍

[Franklin]

34 minutes ago, johnturley said:

The adjustment screw holes on the side of the Vixen focuser actually look more similar to those on the Esprit 150 focuser, and not at all like on the Tak 100 DZ, where there aren't actually any adjustment screw holes on the side of the focuser.

The adjustment grubscrews are on the top of the focuser on both Vixen and Takahashi scopes. Older Vixen scopes in the hammered green livery had side adjusted focusers back in the early 90's. The DZ has two adjustment grubscrews either side of the lock-knob.

 

Edited November 26, 2023 by Franklin

[mikeDnight]

My DZ, which I've had since April 2020, has a relatively smooth and easy to use focuser. I can't remember if its become easier over time or if its always remained the same. What I do remember is that with my DC I needed the MEF, but with the DZ I've never felt the need for it. 

The trouble with having a go at adjusting the focuser, is that if you don't get the pressure on the grub screws just right you'll end up with image shift. I found that out with my DC and it took me some time, trial and error to get it back to an acceptable condition. Sometimes I think the best way to look at any Tak purchase, is that you're paying for the optics. Tak throw the tube and focuser in as a bonus.

Edited November 26, 2023 by mikeDnight

[johnturley]

25 minutes ago, Franklin said:

The adjustment grubscrews are on the top of the focuser on both Vixen and Takahashi scopes. Older Vixen scopes in the hammered green livery had side adjusted focusers back in the early 90's. The DZ has two adjustment grubscrews either side of the lock-knob.

 

I've just had a look at my scope, and yes there are, I hadn't noticed them before, the lower one in particular was largely hidden by the lock-knob. So you need to slacken them off to make the focuser freer moving, any idea about the size of the Allen key required. 

John 

Edited November 26, 2023 by johnturley

[johnturley]

1 hour ago, The60mmKid said:

Has anyone used a Baader Steeltrack focuser with a Tak? They're such darn good focusers (I had the Newtonian version), and they're priced competitively with the Tak fine focusers.

I fitted one to my 14in  Newtonian, replacing the one supplied with the scope by Astro Systems (Luton). 

I agree, its much smoother than the focusers on my Esprit 150, ES 127, and Tak 100 DZ, although it does have a short distance of travel of only 40mm, but then you are limited on a Newtonian, unlike a Refractor. In addition with a Newtonian the weight of a heavy eyepiece is more pushing downwards on the focuser mechanism, rather than pulling outwards with a Refractor.  

John 

Edited November 26, 2023 by johnturley