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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Problem with SW FOCUSER (1 Viewer)

L

Lotusman

Member
Hi,
Iam having problems with the focuser on my ED80. When I attach the D90 the 2" Crayford Focuser is unable to move freely up and down.I have tried to adjust the 2 allen screws underneath but this seemed to make it worse.
I have even taken the focuser off the the SW but cannot see anything broken, even with no camera attach it does not move freely.
Does anyone have any ideas what is wrong, have I broken it ?.

Alan
 
Does that happen with both focuser wheels? or only one?

That most likely is a matter of tightening the bolts underneath the focuser, you said you adjust them but by how much? Probably it isn't enough. Doesn't it feel a bit too loose?

While I'm not seeing the focuser, there's not much to break or malfunction in a crayford focuser (BTW it is a crayford focuser, not rack and pinion) , if everything is tightened correctly it should work fine. That said don't tighten it too much or the dual speed wont work, that's why I ask if it happens with both wheels.
 
Fernando.
Yes this happens with both wheels, that allen screws are as tight as i dare but the unit is not losse.
What does seem to have a huge amount of play is the actual tube that moves in and out.

Alan
 
Of course, that's why it doesn't move. The focuser drawtube it's too loose and doesn't make full contact with the focuser drive.

If the screws are tighten, then something must be preventing the drive to make correct contact with the tube. Or maybe something is missing, usually there's a teflon part for the drive to slide against, that part easily falls if the focuser comes too loose from factory, then you can tighten all you want but it will never work.
 
I'd take the small plate off and check if there is a half round plastic type shim at the back of the chrome bar that has the thumb wheels on either end. Hope that makes sense.

Paul.
 
Paul Corfield said:
I'd take the small plate off and check if there is a half round plastic type shim at the back of the chrome bar that has the thumb wheels on either end. Hope that makes sense.

Paul.
Click to expand...

Yup, that's the teflon part I'm mentioning, and the chrome bar is what I'm calling the drive (I think that's the right name anyway).
 
I don't anything about the SW focuser. With my Celestron 80ED, the allenkey screws adjust the proper fitting of the focuser tube in the focuser body. A chrome screw on top of focuser stops the focuser from creeping. The 4 screws on the gear cover of the pinion adjust the gear backlash. If the 4 screws are too tight, the gear will not turn. Only very light tensioning needed to keep rack and pinion with correct tension.
 
Hi Guys,

I have taken the wheel assembly apart and everthing appears to be OK,however have since reassembled the unit and tightened everything up and it is now working perfectly.
Infact it seems to be a little tight maybe I will slightly slacken the 2 allen screws a little.
Thanks for your guidence.
Alan
 
Lotusman said:
Hi Guys,

I have taken the wheel assembly apart and everthing appears to be OK,however have since reassembled the unit and tightened everything up and it is now working perfectly.
Infact it seems to be a little tight maybe I will slightly slacken the 2 allen screws a little.
Thanks for your guidence.
Alan
Click to expand...

Excellent. Now that you are back on track, go shoot something to show us LOL.
 
I was quite surprised at just how much nicer the feel and resistance is on the focuser of the SW 120 ST compared to the SW 80ED.

There is no flat channel , but proper geared teeth, so i guess thats rack and pinion ? Its excellent, very smooth and zero notchiness, so i wont be changing that for an upgraded focuser like i did before
 
Musoman said:
I was quite surprised at just how much nicer the feel and resistance is on the focuser of the SW 120 ST compared to the SW 80ED.

There is no flat channel , but proper geared teeth, so i guess thats rack and pinion ? Its excellent, very smooth and zero notchiness, so i wont be changing that for an upgraded focuser like i did before
Click to expand...

When will we see some photos taken with the new scope?

Paul.
 
I've only shot some test photos Paul, of nothing really. Just targets outside my window. My tripod head is woefully inadequate and i need to address that first before I can go birding.

I can take another test shot to post but it wont be a classy pic due to wobble ;)
 
Last edited:
OK, here we have some test shots. Bit wobbly as i said, resting on a chair back, so couldnt keep the ST 600 still. Shot at 600mm, no teleconverters. Bright day, sun out, but subject was in shade

Distance on Google Earth = 46 metres ( 151 feet )

Chubb Alarm box size is about 9 inches each side.

Photo No1 is uncropped, but resized.

Photo No2 is 100% Crop but resized

Then we have the posters on the inside of the window of the building, to show much smaller text than the writing on the Chubb Alarm box.

Shots taken with exact same parameters as above with first 2 photos

Photo No1 is uncropped, but resized.

Photo No2 is 100% Crop but resized
 

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Musoman said:
OK, here we have some test shots. Bit wobbly as i said, resting on a chair back, so couldnt keep the ST 600 still. Shot at 600mm, no teleconverters. Bright day, sun out, but subject was in shade

Distance on Google Earth = 46 metres ( 151 feet )

Chubb Alarm box size is about 9 inches each side.

Photo No1 is uncropped, but resized.

Photo No2 is 100% Crop but resized

Then we have the posters on the inside of the window of the building, to show much smaller text than the writing on the Chubb Alarm box.

Shots taken with exact same parameters as above with first 2 photos

Photo No1 is uncropped, but resized.

Photo No2 is 100% Crop but resized
Click to expand...


Nice shots. You mean your SW120 non ED? Wow, that's be a hell lot trickier handling that canon.
 
alphan said:
Nice shots. You mean your SW120 non ED? Wow, that's be a hell lot trickier handling that canon.
Click to expand...

Its not any trickier to handle than the 80ED i had before, as it only weighs 8.5 Lbs which is just 1Lb heavier. But i sold my Gimbal head, and bought a lightweight head, which is now useless for this scope

The length of the 120 ST scope ( without Dew Shield ) to the very end of the focuser tube, with focuser racked in to its shortest position is 500mm. With focuser racked out as far as possible, its 565mm long. So, 65mm of focuser travel

How does that compare to the 80ED ? ( I cant remember the figures off hand )

PS if any of you Scope guys have a skywatcher type mount plate you're not using, sell it to me - cheers !
 
Last edited:
Minus the dew shield the SW 80ED is 480mm racked in and 550mm racked out.

Do a search on google for Skywatcher dovetail bar. The one I use on my 80ED is the medium 21cm long dovetail plate and it's around £15.

Paul.
 
Hey, thats not too bad then is it. For a 40mm increase in aperture, its only 20mm longer racked in, and only 15mm longer racked out. And i get all that extra light ;)

I'll check those plates out, thanks. Though at £15 a shot, i'll probably just hunt down some offcut 8mm alloy plate from an engineering shop
 
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