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electric focuser

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#1 garyc11

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Posted 17 January 2005 - 07:32 PM

does anyone use an electric focuser like the jmi motofocus on their sct. how well do they work? is it better than manual focus? i have a c11-sgt. thank you for your input.

#2 Jim Shaffer

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Posted 17 January 2005 - 09:37 PM

I have a Celestar 8 Basic (a Celestron fork-mounted 8" with a cheap wedge and tripod) and I bought a motofocus because the scope shook so bad at high power that fine focusing was difficult without it. The down side is that some of my eyepieces aren't even close to parfocal, and sometimes I use a focal reducer and sometimes not, and it takes a long time even at the highest speed to go from one extreme of the focuser to the other.

How is the stability of your C11-SGT? I'm thinking about getting one, but I'm wondering if it's too much scope for the mount. The only person I know locally with that mount has the 9.25" scope on it and only observes at low power, so I have no way of comparing it to my current scope.

#3 celestial_search

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Posted 17 January 2005 - 10:11 PM

Jim:

I have the same scope as Gary (C-11 SGT on CG-5 mount). Many threads suggest that the C-11 is slightly overmounted on the CG-5 mount. Consensus seems to be that the CG-5 mount will handle between 32# and 36#. The C-11 OTA with EP, finder, and Telrad is about 30# or slightly above. If you mount is less sturdy than the CG-5 then you may want to consider getting the CG-5 or CG-5 GOTO version with your C-11.

#4 Rusty

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Posted 17 January 2005 - 11:57 PM

I had the motofocus on my N11 - never liked it. It's been replaced with the WO Crayford (visual) and the NGF-S electric for imaging. Both of the latter are great!

#5 garyc11

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Posted 18 January 2005 - 09:39 AM

i find the cg-5 mount with the 11 ota fine for visual work. i havent tried photography with it so i cant comment on that. for the money its a good scope.

#6 celestial_search

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Posted 18 January 2005 - 10:56 AM

I second that motion. Nice thing about the SCTs is the wide range of accessories that you can get/use. I may at some point get the W.O. Crayford focuser for mine.
Gary, did you see the post about the non-illuminated reticle EP? The guy bought one of the $25 ones, but said it is hard to see the crosshairs at night. He suggested the one that functions as an EP, but has an illumintor that can be added.

#7 garyc11

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Posted 18 January 2005 - 12:12 PM

didnt see that post.it seems it would be ok for the three star alaignment as your looking at bright objects but i could be wrong. if you find a good price on an illuminated one let me know. the cheapest one ive seen is around 80-100 bucks. ive been looking at the wo focuser diagonal combo on astronomics looks like a good deal.

#8 garyc11

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Posted 18 January 2005 - 12:15 PM

frank, does the sct base for the orion raci bolt rite up to where the celestron bracket goes.

#9 Johnr0836

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Posted 18 January 2005 - 03:15 PM

I have the Motofocus on my C5+ and like it a lot. As others have said, at high magnification it keeps the image steady.

#10 celestial_search

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Posted 18 January 2005 - 07:03 PM

Gary:

The Orion RACI finder bolts into the very same spot that the stock finder does. The Orion SCT version (see link) fits right over the existing holes.

Orion SCT Finer Mount

#11 celestial_search

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Posted 18 January 2005 - 07:04 PM

Thanks,

I'll have to look at that one.

#12 garyc11

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Posted 18 January 2005 - 08:13 PM

frank, on your mount is the eq head lined up over one of the legs of the tripod or is it inbetween two legs. mine came with the alignment peg inbetween two of the legs of the tripod, i was thinking that it would be more stable over one of the legs.

#13 celestial_search

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Posted 18 January 2005 - 10:03 PM

Gary:

I read the Cloudy Nights Review of the CG-5 Goto mount by Senor J. Crilly before putting mine together. I moved that screw as he suggested so that the counterweights are over a tripod leg for better stability. His review had a couple of points that I followed. It is easy to move the screw (just remove the mount and unscrew it and rescrew it into the hole facing the leg).

#14 garyc11

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Posted 18 January 2005 - 10:43 PM

i read it also it wasnt clear about the counterweights hitting the leg. i guess it doesnt if yours is set up that way. thanks for the info

#15 Starman1

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Posted 19 January 2005 - 01:28 AM

does anyone use an electric focuser like the jmi motofocus on their sct. how well do they work? is it better than manual focus? i have a c11-sgt. thank you for your input.

If, as I do, you own eyepieces that are not close to parfocal, and require large amounts of refocusing when changing eyepieces, you will find the electric focusers annoying and too inaccurate.
I would hold the focus button for over 30 seconds to change from a 22 nagler to an 8.8mm Meade UWA--too slow.
Also, every electric focuser I've used in an SCT took longer to find the ideal focus (due to back-and-forth inertia and lack of sensitivity) than the manual focuser.
Instead, I changed to a 2-1/2" focuser knob on my SCT and gained the focus sensitivity I needed to avoid jittery images during high power focusing.

#16 garyc11

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Posted 19 January 2005 - 01:32 PM

where did you get that focus knob? i cant seem to find one. if you could post a link,thank you

#17 Starman1

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Posted 19 January 2005 - 03:29 PM

Gary,
My scope was a Meade, and my review of the focus knob was here:
http://www.cloudynig...2/ezfocuser.htm
But I was not recommending this knob to you, anyway, because you have a Celestron.
A simple "fix" is to install a 2 to 2.5" diameter "donut" to the focus knob, leaving the smaller tip sticking out so you can easily coarse focus.
You can use Precise Parts:
http://www.precisepa...main/index.html
to make one for you. It is essentially a metal ring with a set screw that surrounds the standard focus knob and tightens against it with a set screw.
I've seen people who used a circular piece of hard foam to accomplish the same thing on a rubber-covered focus knob.
And lastly, you can replace the whole focus knob with a super-sensitive 2-speed knob from Feather Touch:
http://starizona.com...fm?Category=108
Having gone the route of an electric focuser and being disappointed, I'm steering you in the direction of a better focuser instead.

#18 Guest_**DONOTDELETE**_*

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Posted 21 January 2005 - 10:01 PM

The electric focuser I have drove me nutz. It was probably the biggest waste of money that I have ever spent. I can never seem to achieve the "fine " focus I like. A crayford is on the horizon. BTW its for sale real cheap. :lol:

Clear Skies,

Roger

#19 imjeffp

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Posted 22 January 2005 - 09:02 AM

I use a rubber PCV valve grommet from my local auto parts store. Fits snugly with a nice tactile feel.

#20 Starman1

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Posted 22 January 2005 - 01:15 PM

The electric focuser I have drove me nutz. It was probably the biggest waste of money that I have ever spent. I can never seem to achieve the "fine " focus I like. A crayford is on the horizon. BTW its for sale real cheap. :lol:

Clear Skies,

Roger

since the rear-mounted Crayford focuser doesn't eliminate the normal focuser, and there is danger of the extra length causing vignetting at worst or mount contact and balance problems at best, I would advise the FeatherTouch 2 speed focuser as a better solution. The fine focus knob is every bit as sensitive as the rear-mounted Crayford.
IMHO, of course.

#21 werewolf6977

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Posted 22 January 2005 - 01:53 PM

I don't use the pcv valve grommet, myself, but I do have a 2" rubber fender washer that does the trick!!

#22 Canadian

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Posted 05 February 2005 - 10:10 AM

Roger, the fine focuser you pointed us to from Starlight looks promising. (I'd heard about this, but until now, hadn't found any info) This would give much better control. (I have a newly aquired CG11)

But it does not fix the image shift problem that the rear mounted focusers say they do. And while I have been researching the rear focusers, WO,JMI and Feathertouch, none of them mentioned vignetting. Does the vignetting problem affect visual or imaging or both?

Would using both be an optimal upgrade?

Garry
ED80/EQ5
CG11

#23 Canadian

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Posted 11 October 2005 - 02:42 AM

Well to answer my own question, using the Starlight FeatherTouch Micro focuser with a JMI NGF-CM worked out preety good. I think I would have liked more than a 1/2 of travel on the JMI, but acheiving a good focus using the manual FeatherTouch first and the JMI afterwards, has worked fine. Plus, using the JMI eliminated the mirror shift as well.

#24 Eddy

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Posted 11 October 2005 - 04:39 AM

Hi,
I might be a bit late jumping in here. I bought a NGF-C last year for my C8 and recently upgraded it with the motofocus system because of the vibrations when touching the scope/focuser at high power and also because I am starting with astrophotography. I do like the upgrade very much although the focusing process takes a bit more time than before. I roughly focus with the scope's focuser and fine-tune afterwards with the JMI one. No vibrations at all and is very helpful with imaging. You can have a look at the laptop while focusing with the motofocus system. In fact, it has a triple speed function: very slow, slow and fast. The first two depend of the switch position, the latter starts when depressing one of the focus knobs for longer than 2 seconds.
Cheers,

#25 Flying_Fox

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Posted 11 October 2005 - 09:08 PM

Hi All,

I am researching the electric focusers possibilities too. I have Celestron Nexstar 8i. First I was thinking of the JMI Motorfocus like here but then decided against it, as it does not eliminate the image shift. Now I am thinking about JMI NGF-CM. Does anybody have any experience with NGF-CM installed on Nexstar 8i? :question: Apparently I will need the Ray's Bracket for it. Any other pro or contra?


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