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Recommendations for drop-in focuser for ES N208CF Newt

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#1 Tom62e

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Posted 06 December 2021 - 06:39 AM

Hi all,

Looking to replace the stock focuser on my 8" Explore Scientific N208CF Newtonian astrograph. I do not wish to drill holes in the OTA if it can be avoided.

Single or double speed is fine. I will be connecting a ZWO EAF auto-focuser to it.

Thanks to all who reply.

Clear skies,
Tommy

#2 jmillsbss

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Posted 06 December 2021 - 09:38 AM

IIMA, what's the problem with the OEM piece?  Isn't it a 2-speed already?  It wouldn't seem to me to really matter what is already on it if you have an EF on it?  Are there issues with the original like tilt or sloppy/poor specs?

 

I ask all these questions because I've about determined this will be my next scope after the upgrade to a much beefier mount...



#3 Tom62e

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Posted 06 December 2021 - 11:54 AM

IIMA, what's the problem with the OEM piece?  Isn't it a 2-speed already?  It wouldn't seem to me to really matter what is already on it if you have an EF on it?  Are there issues with the original like tilt or sloppy/poor specs?

 

I ask all these questions because I've about determined this will be my next scope after the upgrade to a much beefier mount...

Actually, I can't figure out a way to install the EAF onto the stock focuser.  And since I use a ASI2600 (a fairly heavy camera) and an HRCC coma corrector (large and heavy as far as CC's go), I figured I'd take this time to upgrade.  



#4 George N

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Posted 06 December 2021 - 04:20 PM

Even bigger issue - there are no high-end focusers to be found right now. FT is certainly months out - and who knows about the others.

 

My thinking (as an owner of the same telescope - which is 'discontinued' on the ES website, and gone on High Point ) -- I have full size chip CCD cameras and a Canon Ra -- so I expect I'll need a 3-inch focuser and 3-inch Paracoor at some point to avoid vignetting. Until then I'll just use the ES focuser.



#5 Tom62e

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Posted 06 December 2021 - 04:55 PM

Even bigger issue - there are no high-end focusers to be found right now. FT is certainly months out - and who knows about the others.

 

My thinking (as an owner of the same telescope - which is 'discontinued' on the ES website, and gone on High Point ) -- I have full size chip CCD cameras and a Canon Ra -- so I expect I'll need a 3-inch focuser and 3-inch Paracoor at some point to avoid vignetting. Until then I'll just use the ES focuser.

To mount a 3" focuser, this means you'd need to cut the opening larger, yes?  Would you do that yourself, or send it somewhere?


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#6 George N

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Posted 06 December 2021 - 06:02 PM

To mount a 3" focuser, this means you'd need to cut the opening larger, yes?  Would you do that yourself, or send it somewhere?

Yes, the hole would need to be cut, and new holes drilled. I would probably get some friends to help. I've drilled fiberglass tubes, but never carbon fiber. You need to work slow, or it will melt.

 

If things were still "normal" -- I'd do the same as I did with my 6-inch F/5 ATM scope ( self-made oak tube ) -- I'd just take it to NEAF and walk up to Moonlite (or FT) and say -- "I'll buy your stuff, if you install it!" -- and that's exactly what the Moonlite guys did - sold me a 2-inch 2-speed focuser and the "appropriate" attachment hardware ( all at a 20% NEAF discount!!! ) - they drilled the holes and installed the focuser. I picked the tube up about 2 hours after I had dropped it off and took it out to my car. Moonlite has also installed at least 2 of their focusers on refractors belonging to the local astronomy club or members ( one, an Astro Physics 6-inch F/12 ) - all requiring connectors. They did the work for free ( but of course full price for the focuser & hardware - plus the time to drive down to his shop twice - drop off, pick up a week or so later ).



#7 Tom62e

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Posted 06 December 2021 - 07:14 PM

Yes, the hole would need to be cut, and new holes drilled. I would probably get some friends to help. I've drilled fiberglass tubes, but never carbon fiber. You need to work slow, or it will melt.

 

If things were still "normal" -- I'd do the same as I did with my 6-inch F/5 ATM scope ( self-made oak tube ) -- I'd just take it to NEAF and walk up to Moonlite (or FT) and say -- "I'll buy your stuff, if you install it!" -- and that's exactly what the Moonlite guys did - sold me a 2-inch 2-speed focuser and the "appropriate" attachment hardware ( all at a 20% NEAF discount!!! ) - they drilled the holes and installed the focuser. I picked the tube up about 2 hours after I had dropped it off and took it out to my car. Moonlite has also installed at least 2 of their focusers on refractors belonging to the local astronomy club or members ( one, an Astro Physics 6-inch F/12 ) - all requiring connectors. They did the work for free ( but of course full price for the focuser & hardware - plus the time to drive down to his shop twice - drop off, pick up a week or so later ).

Wow, that was brilliant.  I lived in NY my entire life shy of three years ago.  I regret never going to NEAF.  SMH.



#8 Dan_I

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Posted 07 December 2021 - 06:12 AM

To mount a 3" focuser, this means you'd need to cut the opening larger, yes?  Would you do that yourself, or send it somewhere?

Not necessarily, depending on the location of the focal plane with the coma corrector inserted.

 

post-144218-0-05388700-1625477680.jpg

 

On my 200/800 carbon newt I use a  3" R&P focuser from Teleskop service, very solid and allowing to use large format correctors.

 

I had a custom adapter machined in a local shop, that is  fitted to the OTA using the same screw holes as the original V-Power 2" focuser.

 

I had to saw about 0.8" of the focuser drawtube to avoid hitting the OTA, however I still have more than 1" of focus travel, largely enough for imaging. Notice that my coma corrector is 2.5" in diameter and  protrudes inside the OTA at focus (the focuser hole is large enough for the corrector). I could have used the 3" Wynne corrector from TS as well, thanks to its outwards focus shift.


Edited by Dan_I, 07 December 2021 - 07:50 AM.


#9 Tom62e

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Posted 07 December 2021 - 10:46 AM

Not necessarily, depending on the location of the focal plane with the coma corrector inserted.

 

attachicon.gifpost-144218-0-05388700-1625477680.jpg

 

On my 200/800 carbon newt I use a  3" R&P focuser from Teleskop service, very solid and allowing to use large format correctors.

 

I had a custom adapter machined in a local shop, that is  fitted to the OTA using the same screw holes as the original V-Power 2" focuser.

 

I had to saw about 0.8" of the focuser drawtube to avoid hitting the OTA, however I still have more than 1" of focus travel, largely enough for imaging. Notice that my coma corrector is 2.5" in diameter and  protrudes inside the OTA at focus (the focuser hole is large enough for the corrector). I could have used the 3" Wynne corrector from TS as well, thanks to its outwards focus shift.

That looks awesome.  Did it add a lot of extra weight? I bought the ES Carbon Fiber to help keep the weight down. An 8” Newt is about at the max weight I would want to be on my EQ6R-Pro.

 

 I thought about replacing the focuser with an Orion low profile hybrid - but that things is super heavy. Plus I would need to drill new holes, which I would rather avoid if I could. 



#10 jmillsbss

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Posted 07 December 2021 - 11:23 AM

Actually, I can't figure out a way to install the EAF onto the stock focuser.  And since I use a ASI2600 (a fairly heavy camera) and an HRCC coma corrector (large and heavy as far as CC's go), I figured I'd take this time to upgrade.  

I use the ES HRCC too. It's lighter than the TVCC but not necessarily the lightest CC by a longshot.  There are simpler coma correctors out there but maybe not as adjustable as the ES or Paracorr.

 

Most aftermarket electronic focusers are sorta one size fits all.  Just a matter of removing one of the focus knobs and sliding the EF on the focuser shaft, tighten the set screw and there you go.  Is the EAF really so different?  I've just never seen one.



#11 Tom62e

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Posted 07 December 2021 - 11:51 AM

I use the ES HRCC too. It's lighter than the TVCC but not necessarily the lightest CC by a longshot.  There are simpler coma correctors out there but maybe not as adjustable as the ES or Paracorr.

 

Most aftermarket electronic focusers are sorta one size fits all.  Just a matter of removing one of the focus knobs and sliding the EF on the focuser shaft, tighten the set screw and there you go.  Is the EAF really so different?  I've just never seen one.

Installing the EAF onto the focus knob is easy-peasy.  The issue is securely mounting the body of the EAF to the focuser — so the EAF doesn't move when in operation. 

 

Normally you replace a few of the screws on the bottom of the focuser (between the focuser knobs) with longer screws (this is typically where you find the tensioner screw among others).  You would then use those replacement screws to install the mounting plate.  Those typical screws are not on the ES stock focuser.  The design leaves no way of mounting the body of the EAF.

 

I tried using zip-ties to mount the EAF, but it wasn't secure enough.  



#12 Dan_I

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Posted 07 December 2021 - 03:25 PM

That looks awesome.  Did it add a lot of extra weight?

It adds about 700g, not a big issue for my AZEQ6.

 

 



#13 Tom62e

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Posted 07 December 2021 - 09:36 PM

Not necessarily, depending on the location of the focal plane with the coma corrector inserted.

 

attachicon.gifpost-144218-0-05388700-1625477680.jpg

 

On my 200/800 carbon newt I use a  3" R&P focuser from Teleskop service, very solid and allowing to use large format correctors.

 

I had a custom adapter machined in a local shop, that is  fitted to the OTA using the same screw holes as the original V-Power 2" focuser.

 

I had to saw about 0.8" of the focuser drawtube to avoid hitting the OTA, however I still have more than 1" of focus travel, largely enough for imaging. Notice that my coma corrector is 2.5" in diameter and  protrudes inside the OTA at focus (the focuser hole is large enough for the corrector). I could have used the 3" Wynne corrector from TS as well, thanks to its outwards focus shift.

Dan - what CF scope do you have in that picture?



#14 mayhem13

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Posted 07 December 2021 - 09:51 PM

Installing the EAF onto the focus knob is easy-peasy.  The issue is securely mounting the body of the EAF to the focuser — so the EAF doesn't move when in operation. 

 

Normally you replace a few of the screws on the bottom of the focuser (between the focuser knobs) with longer screws (this is typically where you find the tensioner screw among others).  You would then use those replacement screws to install the mounting plate.  Those typical screws are not on the ES stock focuser.  The design leaves no way of mounting the body of the EAF.

 

I tried using zip-ties to mount the EAF, but it wasn't secure enough.  

Mount he EAF to the tube……..a little shade tree DIY and done….



#15 Tom62e

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Posted 07 December 2021 - 10:17 PM

Mount he EAF to the tube……..a little shade tree DIY and done….

Interesting idea.  I never would have thought of that.  And now that you say it, I could probably 3-D print a mounting bracket/spacer to install on the tube.  And then mount the EAF to that.

 

I like the way you think outside the box!


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#16 mayhem13

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Posted 08 December 2021 - 12:53 AM

post-356785-0-45193700-1627188777.jpeg

Interesting idea.  I never would have thought of that.  And now that you say it, I could probably 3-D print a mounting bracket/spacer to install on the tube.  And then mount the EAF to that.

 

I like the way you think outside the box!

I didn’t have access to a 3D printer so I did it by hand with sandpaper and a 5 gal bucket for the arc. Took about 20 minutes to fabricate from HDPE black plastic I had on hand.



#17 Dan_I

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Posted 08 December 2021 - 03:04 PM

Dan - what CF scope do you have in that picture?

Self-assembly from various sources, some parts custom made, some parts off the shelf.



#18 Tom62e

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Posted 08 December 2021 - 06:30 PM

attachicon.gifpost-356785-0-45193700-1627188777.jpeg

I didn’t have access to a 3D printer so I did it by hand with sandpaper and a 5 gal bucket for the arc. Took about 20 minutes to fabricate from HDPE black plastic I had on hand.

Building on your idea, I may install a 3rd OTA ring above the focuser and mount the bracket to that.  I was looking to install a 3rd ring anyway for supporting the OTA around the focuser.  I've seen guys do this to prevent focuser sag and what-not.  Especially in cheap metal OTAs.

 

I can't wait to try this!




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