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AT 102 EDL focuser issue

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#1 Lite2

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Posted 14 May 2021 - 10:14 PM

I love my new scope but although I am purely imaging I have noticed that the fine focus knob slips, like bad.

My purpose was solely to add the ZWO EAF but as far as I can tell the left "coarse" knob does not come off, I see no grub screws on it so I can't use the EAF. After taking the scope out the 1st night I got it I just winged it to test the scope out and it's great, at least for me. But very surprised of how weak the fine focus knob is, the coarse is working as it should. I am waiting on a reply from Mike/Astonomics about what may be wrong.

I have now ordered a Moonlite focuser so I can have my trusted stepper motor focus again,  but am curious as to any settings/adjustment that is off for the fine to slip that bad. I would have considered putting the EAF on the fine shaft but can't trust the slippage for my focus to be right. Nice looking focuser on the 102EDL but not up to the task of precise repeatable focus for imaging for me.



#2 bacon

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Posted 14 May 2021 - 11:04 PM

Something is definitely wrong here, mine has no perceptible slip or backlash.  The fine focus knob is excellent for visual use. 

I use a similar style electronic focuser and it works very well.  The coarse knob set screws are revealed by removing one of the focuser housing screws.  I hope you are able to get it fixed in a timely manner, it's disconcerting your focuser made it passed QC.

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  • AT102EDL_3.jpg


#3 Redbetter

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Posted 15 May 2021 - 01:39 AM

Have you tried adjusting the tension balance for the fine focus knob?  I haven't seen images of the underside of the AT102EDL, but if the build of the rack and pinion is the same as the AT60ED and AT72EDII, then you might need to fine tune this.  I had problems out-of-the-box with the fine focus of the AT60ED.  I found an explanation of the screws and adjusted as described in post #299 in the following thread:  fine focus adjustment link.  AT72EDII didn't need adjustment from what I recall.  

 

Fine focus knobs have been a frequent source of fiddling over the decades, whether refractors or Dobs.  The fine focus can be more trouble than it is worth...until you finally get it dialed in.  Once dialed in I don't seem to have to mess with them again unless the focuser suffers some physical trauma.  A major problem is general lack of documentation about focuser adjustment.



#4 GSBass

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Posted 15 May 2021 - 07:13 AM

No issues with mine either, very nice and smooth, but I did take a picture showing underside, guess those 3 tiny screws are going to be the answer although I don’t guess it matters if the op has a moonlite on the way, I bet just one of those screws worked out just enough during shipment not to have solid contact on the gear teeth, actually probably the only thing it could be, a tiny turn should fix it

_____

update… just to keep anyone from having to research further, look at the picture of the 3 perpendicular screws… the middle one will adjust the tension for the fine focus, tighten, check, back off til you have a smooth travel

 

Have you tried adjusting the tension balance for the fine focus knob?  I haven't seen images of the underside of the AT102EDL, but if the build of the rack and pinion is the same as the AT60ED and AT72EDII, then you might need to fine tune this.  I had problems out-of-the-box with the fine focus of the AT60ED.  I found an explanation of the screws and adjusted as described in post #299 in the following thread:  fine focus adjustment link.  AT72EDII didn't need adjustment from what I recall.  

 

Fine focus knobs have been a frequent source of fiddling over the decades, whether refractors or Dobs.  The fine focus can be more trouble than it is worth...until you finally get it dialed in.  Once dialed in I don't seem to have to mess with them again unless the focuser suffers some physical trauma.  A major problem is general lack of documentation about focuser adjustment.

Attached Thumbnails

  • 38D59E72-05D7-47C1-A5D3-08984496A704.jpeg

Edited by GSBass, 15 May 2021 - 10:19 AM.

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#5 Jon Isaacs

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Posted 15 May 2021 - 10:48 AM

There are a number of possible reasons the fine focuser is slipping. It could be as simple as a loose set screw on the knob or on the adapter between the two speed unit and the focuser body.  It could be an internal adjustment.

 

The Astro-tech focuser is a rack and pinion, the Moonlite is a Crayford, rack and pinion Focusers are generally preferred for astrophotography. 

 

Jon


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#6 GSBass

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Posted 15 May 2021 - 10:53 AM

Sorry the op had an issue but have to say this is the nicest focuser I have ever had…. I mean super nice, can’t imagine a upgrade

There are a number of possible reasons the fine focuser is slipping. It could be as simple as a loose set screw on the knob or on the adapter between the two speed unit and the focuser body.  It could be an internal adjustment.

 

The Astro-tech focuser is a rack and pinion, the Moonlite is a Crayford, rack and pinion Focusers are generally preferred for astrophotography. 

 

Jon


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#7 Redbetter

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Posted 15 May 2021 - 05:36 PM

Thanks for the pic of the bottom of the focuser.  It is the same arrangement as the other AT's I have.  The fine focus tension adjustment is the middle of the three screws.  It is a 2mm hex.  


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#8 Lite2

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Posted 16 May 2021 - 12:02 AM

No issues with mine either, very nice and smooth, but I did take a picture showing underside, guess those 3 tiny screws are going to be the answer although I don’t guess it matters if the op has a moonlite on the way, I bet just one of those screws worked out just enough during shipment not to have solid contact on the gear teeth, actually probably the only thing it could be, a tiny turn should fix it

_____

update… just to keep anyone from having to research further, look at the picture of the 3 perpendicular screws… the middle one will adjust the tension for the fine focus, tighten, check, back off til you have a smooth travel

I did try the center of the 3 inline screws and it didn't help the fine focus.

Thanks for the tip Bacon on the access to the coarse knob, that worked and I have the EAF installed now so I will wait for the next clear night to test the auto focus in SGP to see if it works. I still think the resistance on the focuser is too tight, it just feels harder to move than any scope i've had.

Will put a hold on the Moonlite for now, but may just have to get it.



#9 Lite2

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Posted 19 May 2021 - 08:46 PM

Mike replied and just said to adjust/tighten the middle of the 3 screws but the fine focus is still loose so the Moonlite is on the way.

I had such high hopes for the focuser on this scope and although I did finally get the EAF installed I will stick with  the (to me) trusted Moonlite and sell the EAF.

It may work fine with the stock  + EAF but at this point I just don't trust the stock focuser.

I loved the focuser on my WOZ73 using the Moonlite Stepper motor but would likely trash the stock focuser from my 102. Glad everyone else is happy with theirs.



#10 Moondust

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Posted 19 May 2021 - 09:06 PM

I don't have an issue with the focuser on my 102EDL and it's presently working very smoothly. I did however notice that the fine focus knob was wobbling when I turned the course knob suggesting it was not on flush. I took it off and put it on several times with no improvement. I then noticed the hole where the fine knob slides onto the shaft is cut way too big so has a lot of play which is causing it to wobble. I wrapped some white plummers tape around the shaft a few times then reapplied the fine focus knob and no more wobble.   



#11 Lite2

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Posted 26 May 2021 - 09:40 PM

My 102 focuser is on the way to Mike/Astronomics to check out. My new Moonlite is great! Still waiting on a good night to test... :(


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#12 Lite2

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Posted 31 May 2021 - 06:51 PM

My focuser from my 102edl is on the way to Mike to check out. I now have a Moonlite installed and finally got a few moments last night between the clouds.

My question now is for guidance as to how to adjust the tilt. In this shot from last night the right side don't look too bad but the left half of the frame is certainly "pointing" to the right side of the frame.

What is the methodology of discerning which way to move the imaging train? I have never been so picky as now to care, but now I do.

Do I move the focuser/camera into the "point" or away to correct? As in my example with the stars pointing to the right for the most part, what way should the imaging train move to compensate for that?

In other words, how to "steer" the eggs:).

Once I figure that out I would assume that then it's just a matter of spacing between the flattener and the camera to even the whole field.

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  • broom_short-Oxygen_III (Large).jpg


#13 daquad

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Posted 03 June 2021 - 08:41 AM

My focuser from my 102edl is on the way to Mike to check out. I now have a Moonlite installed and finally got a few moments last night between the clouds.

My question now is for guidance as to how to adjust the tilt. In this shot from last night the right side don't look too bad but the left half of the frame is certainly "pointing" to the right side of the frame.

What is the methodology of discerning which way to move the imaging train? I have never been so picky as now to care, but now I do.

Do I move the focuser/camera into the "point" or away to correct? As in my example with the stars pointing to the right for the most part, what way should the imaging train move to compensate for that?

In other words, how to "steer" the eggs:).

Once I figure that out I would assume that then it's just a matter of spacing between the flattener and the camera to even the whole field.

In that pic, looks to me like all stars are pointing downward and slightly to the left.  Guiding?

 

Dom Q.



#14 Lite2

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Posted 05 June 2021 - 08:23 PM

No issues with mine either, very nice and smooth, but I did take a picture showing underside, guess those 3 tiny screws are going to be the answer although I don’t guess it matters if the op has a moonlite on the way, I bet just one of those screws worked out just enough during shipment not to have solid contact on the gear teeth, actually probably the only thing it could be, a tiny turn should fix it

_____

update… just to keep anyone from having to research further, look at the picture of the 3 perpendicular screws… the middle one will adjust the tension for the fine focus, tighten, check, back off til you have a smooth travel

My trouble wasn't smoothness but slippage. The fine knob can't lift my imaging setup (1600, 5 filter wheel, OAG, FR). I sent the focuser back to Mike and he said he fixed it and said he was caught off guard about the new focuser design and was glad to know but to me it is still slipping a lot. I did get the Moonlite but am rethinking the need and the stock 102EDL focuser is ok on the course shaft so the fine knob is useless to me anyway. I want to use the ZWO EAF that I have so I am now looking for a threaded adapter for the stock focuser tube. It seems that I need a 62 to 48mm adapter but I am not positive that the tube is 62mm (that's my caliper measurement) but I don't seem to find a 62mm to 48mm threaded adapter anywhere. The stock compression ring has way too much wiggle for me so I want the camera all threaded. Is it a 63mm thread on the focuser tube? I see those listed.


Edited by Lite2, 05 June 2021 - 09:25 PM.


#15 Lite2

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Posted 09 June 2021 - 08:10 PM

I sent the Moonlite back (was hard to do), but for the extra weight the EAF on the stock focuser was the best choice not to mention about $300 less.

Had a short nite to test the EAF and although a crappy nite as far as clarity it seemed to work fine.




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