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Equipment Discussions >> Refractors

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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 102mm F7 Kunming refractor comparisons new [Re: CollinofAlabama]
      #5926185 - 06/17/13 07:24 PM

Quote:


How does one get it off? I see the small black metal screws down the indention at 120* angles. Do I unscrew them? I don't see anything to attach the single speed Crawford on the tube, proper. Will I need some kind of adapter? Who might sell one? Any information is appreciated.




Collin:

I wouldn't bother with trying to replace the current two speed focuser with another single speed, it's much easier just to disable the two speed micro-focuser and use the current focuser as a single speed.

The roughness is caused by the micro-focuser so if it disabled, you are home free. Assuming the Orion is like the AT-102ED, the easiest way to disable to the two speed is this:

Underneath the focuser knobs, these is a stainless steel bushing/collar with three small set screws at 120 degrees apart. If you loosen these so the collar is free to move, the two speed is disabled and the focuser work smoothly as a single speed. If you want a photo, I can take one.

Jon


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CollinofAlabama
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Reged: 11/24/03

Loc: Lubbock, Texas, USA
Re: 102mm F7 Kunming refractor comparisons new [Re: Jon Isaacs]
      #5926723 - 06/18/13 01:02 AM

Gosh, Jon, I'd appreciate it. No big rush, but if you get a chance to snap off a shot, that'd be great. Still like the idea of the lightweight ED80 single speed Crayford on it. Honestly, at F/7, a single speed's all I need for fine focus, provided its good, and the Orion old school 80 and 100ED focusers were (and in my case, are). But any advice offered that covers either course, provided I get smooth focusing, is the right path for me. Again, no rush but if you can snap off a shot, can't hurt.

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beanerds
sage


Reged: 07/15/08

Loc: Darwin Australia
Re: 102mm F7 Kunming refractor comparisons new [Re: CollinofAlabama]
      #5926970 - 06/18/13 08:12 AM

Jon , I did exactly the same thing , works a treat .
Then I dissasembled the whole thing , and found the 3 balls that drive the 10-1 reduction were made out of this kind of black rock material ?? , not round , or uniform in size , also the 3.2mm stainless steel shaft that drives the lot was only 3mm in diameter ,, damn .
After a bit of a dig around , I found that "NTN" bearings made a ball race # 6304LLU/2AS have real hardened and spherical balls that fitted my focuser's brass race ,.
I hand made a piece of 3.2mm , 316 S/S TIG wire to use as a shaft and its still working today , nice , not FT quality but a lot better than what left the factory and ended up on my ED80 ...
Brian.

Edited by beanerds (06/18/13 08:14 AM)


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 102mm F7 Kunming refractor comparisons new [Re: beanerds]
      #5927015 - 06/18/13 08:38 AM

Quote:

Jon , I did exactly the same thing , works a treat .
Then I dissasembled the whole thing , and found the 3 balls that drive the 10-1 reduction were made out of this kind of black rock material ?? , not round , or uniform in size , also the 3.2mm stainless steel shaft that drives the lot was only 3mm in diameter ,, damn .
After a bit of a dig around , I found that "NTN" bearings made a ball race # 6304LLU/2AS have real hardened and spherical balls that fitted my focuser's brass race ,.
I hand made a piece of 3.2mm , 316 S/S TIG wire to use as a shaft and its still working today , nice , not FT quality but a lot better than what left the factory and ended up on my ED80 ...
Brian.




Brian:

I have messed around with the darn things, replaced the balls, the shafts, polished the races... I had some luck improving them but they were never smooth enough for me.

As far as the black balls... I have a focuser that came off a Astronomy Technologies 102mm F/7, not an Astro-Tech, it's the small company that according to Jim Barnett is in the same strip mall as StellarVue.

It's very similar to the Astro-Tech Focuser but lighter duty. The 4 upper bearings that the drawtube rides in had a 0.5mm thick plastic layer. It was probably an experiment to see if it would prevent marking the anodizing.

Whatever, it developed flats in the plastic. I was very confusing.. I would disassemble the focuser, put it back together and it would work for a short while. But then it would quit, the focuser just spun. I finally noticed the flats... I worked at first because they were not aligned, but they would soon be aligned and the darn thing would just spin..

jon

Edited by Jon Isaacs (06/18/13 08:52 AM)


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 102mm F7 Kunming refractor comparisons new [Re: CollinofAlabama]
      #5927033 - 06/18/13 08:45 AM

Quote:

Gosh, Jon, I'd appreciate it. No big rush, but if you get a chance to snap off a shot, that'd be great. Still like the idea of the lightweight ED80 single speed Crayford on it. Honestly, at F/7, a single speed's all I need for fine focus, provided its good, and the Orion old school 80 and 100ED focusers were (and in my case, are). But any advice offered that covers either course, provided I get smooth focusing, is the right path for me. Again, no rush but if you can snap off a shot, can't hurt.




Collin:

I think if you disable the 2 speed you will probably like the focuser as a single speed, it's more robust than the ED-80 focuser... And it's a whole lot easier to make happen.

I recently purchased a Skywatcher Pro focuser on Astromart for $65, it's the same thing as the ED-80 with different paint and a two speed. It's on my Orion SkyView 100mm F/6 achromat, it's surprisingly good, I had to shorten the drawtube and it needed some adjustment but it'll handle a 20mm type 2 Nagler without a problem.

Also, if you post of photo of the underside of your focuser, I can edit it and show you where the set screws are.

Jon


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stevew
Now I've done it


Reged: 03/03/06

Loc: British Columbia Canada
Re: 102mm F7 Kunming refractor comparisons new [Re: Jon Isaacs]
      #5928404 - 06/18/13 11:06 PM Attachment (29 downloads)

Jon, Is this the focuser you guys are talking about?

Steve


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stevew
Now I've done it


Reged: 03/03/06

Loc: British Columbia Canada
Re: 102mm F7 Kunming refractor comparisons new [Re: stevew]
      #5928407 - 06/18/13 11:10 PM Attachment (30 downloads)

A couple of months ago I bought the 110mm version of this scope and have been thoroughly enjoying it.
I haven't had a problem with the focuser.
It seems very smooth, and handles quite a lot of weight.
Frankly its better than any GSO focuser I have.
Is there something I should watch out for?

Steve


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 102mm F7 Kunming refractor comparisons new [Re: stevew]
      #5928675 - 06/19/13 04:17 AM Attachment (25 downloads)

Quote:

Jon, Is this the focuser you guys are talking about?

Steve




It looks like it, thanks. I have edited the photo to show the location of one of the set screws, there are three around the circumference of that bushing. If they are loosened so the part is free to rotate, the two speed is disabled and the focuser should be smooth and free as a single speed.

Jon


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dennilfloss
sage


Reged: 01/06/13

Loc: Ottawa, Canada
Re: 102mm F7 Kunming refractor comparisons new [Re: Jon Isaacs]
      #5928714 - 06/19/13 06:22 AM

Might be a stupid question but which of the two speeds remains enabled then, the coarse focus or the fine focus?

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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 102mm F7 Kunming refractor comparisons new [Re: dennilfloss]
      #5928719 - 06/19/13 06:45 AM

Quote:

Might be a stupid question but which of the two speeds remains enabled then, the coarse focus or the fine focus?




The coarse focus. The two speed microfocuser is a planetary gear set that uses ball bearing under load as the gears. If the surfaces are not perfectly smooth or become damaged, it creates a rough spot. Since the ratio between the coarse and fine focuser is about 11:1, moving the coarse focuser causes the fine focuser to rotate 11 times faster, 1 rough spot becomes 11 rough spots... it also magnifies the roughness. Generally, the microfocuser knob is heavy, brass or steel weighted, this helps smooth out the roughness.

The collar with the set screws is part of the planetary gearing and by allowing it to rotate freely, it disables the microfocuser and so the rough spots disappear.

Jon


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Agatha
Pooh-Bah


Reged: 06/04/12

Loc: Coulee Region, Wisconsin
Re: 102mm F7 Kunming refractor comparisons new [Re: Jon Isaacs]
      #5929006 - 06/19/13 11:08 AM

Quote:

I have a focuser that came off a Astronomy Technologies 102mm F/7, not an Astro-Tech, it's the small company that according to Jim Barnett is in the same strip mall as StellarVue.




Hi Jon, The above statement is a bit confusing. Astronomy Technologies and Astro-Tech are one and the same. Astro Telescopes are the telescopes from Hands On Optics. I have several Astro-Tech scopes and not all the same focusers. I'm sure they have come from different sources and some perhaps the same as those from HandsOn.

I seem to remember that when Astro Telescopes came on the scene, Astro-Tech wasn't exactly thrilled with the name.
Anyway, my only point is to clarify company names. . I hope his makes sense.

Best,


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 102mm F7 Kunming refractor comparisons new [Re: Agatha]
      #5929058 - 06/19/13 11:33 AM

Quote:

Quote:

I have a focuser that came off a Astronomy Technologies 102mm F/7, not an Astro-Tech, it's the small company that according to Jim Barnett is in the same strip mall as StellarVue.




Hi Jon, The above statement is a bit confusing. Astronomy Technologies and Astro-Tech are one and the same. Astro Telescopes are the telescopes from Hands On Optics. I have several Astro-Tech scopes and not all the same focusers. I'm sure they have come from different sources and some perhaps the same as those from HandsOn.

I seem to remember that when Astro Telescopes came on the scene, Astro-Tech wasn't exactly thrilled with the name.
Anyway, my only point is to clarify company names. . I hope his makes sense.

Best,




Agatha:

Thanks for catching my mistake. Hopefully Jim Barnett will pop into to clarify exactly the name of the company I was thinking of. It was something very much like Astro Tech..

Jon


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DaveJ
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Reged: 01/07/05

Loc: NE Ohio
Re: 102mm F7 Kunming refractor comparisons new [Re: Jon Isaacs]
      #5929082 - 06/19/13 11:50 AM

Quote:

Thanks for catching my mistake. Hopefully Jim Barnett will pop into to clarify exactly the name of the company I was thinking of. It was something very much like Astro Tech.




Agatha was correct: it was, and is, "Astro Telescopes." A similar "similar name" adventure as "Stellarvue" and the brand name (at the time of naming) with instant credibility, "Tele Vue." "Astro-Tech"/"Astro Telescopes" and "Tele Vue"/"Stellarvue" Hmmmm. To me, it seems to demonstrate a desire to confuse a potential buyer to purchase one's products by naming them such as to cause said confusion.


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CollinofAlabama
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Reged: 11/24/03

Loc: Lubbock, Texas, USA
Re: 102mm F7 Kunming refractor comparisons new [Re: Jon Isaacs]
      #5938771 - 06/24/13 09:50 PM

Jon,

Yes, my focuser looks identical to this one. I have loosened the 3 120*-apart hex screws, and lo and behold, apparent smooth movement! Nothing like what it was! To me, it looks like the fine focusing part is still working, but we shall see. Again, I'm cool with it being a nice single speed, for F/7. All of this is academic, as I've not used it under the stars -- yet. Just enough time to give this a whirl between loads of dishes and putting one of our two girlies down. Gotta go do night-night duty now. I'll let you know how this works under the skies.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: 102mm F7 Kunming refractor comparisons new [Re: CollinofAlabama]
      #5939064 - 06/25/13 01:59 AM

Quote:

Jon,

Yes, my focuser looks identical to this one. I have loosened the 3 120*-apart hex screws, and lo and behold, apparent smooth movement! Nothing like what it was! To me, it looks like the fine focusing part is still working, but we shall see. Again, I'm cool with it being a nice single speed, for F/7. All of this is academic, as I've not used it under the stars -- yet. Just enough time to give this a whirl between loads of dishes and putting one of our two girlies down. Gotta go do night-night duty now. I'll let you know how this works under the skies.




Collin:

The two speed still turns but the drawtube doesn't move. instead, that stainless collar turns. A lot smoother.. One of my dreams is to design an improved two speed micro focuser that uses sealed bearings.

Jon


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CollinofAlabama
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Reged: 11/24/03

Loc: Lubbock, Texas, USA
Re: 102mm F7 Kunming refractor comparisons [Re: Jon Isaacs]
      #5971605 - 07/15/13 02:33 AM

Jon, followed your advice on the 120* micro screws as previously noted. A couple of nights under the stars and here are the results. Yes, generally I can get it to focus precisely as a single speed with the main focus knob. Ironically, the fine focus still works, somewhat. It can be used to come to exacting focus once your really close with the big knob, as you'd expect, but it can just as often just plain mess up the focusing, requiring a restart with the big knob.

Overall, it's better. Still, it would be nicer to have the 80ED focuser I bought for it, or a really nice dual speed like the SkyWatchers (and our 80ED scopes) have. Has anyone removed that focuser and tried to install another? Is it just not worth it? Does it require a pair of experienced optical hands? I can live with it, but it isn't optimal.


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Geo.
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Re: 102mm F7 Kunming refractor comparisons new [Re: stevew]
      #5973991 - 07/16/13 11:55 AM

Quote:

A couple of months ago I bought the 110mm version of this scope and have been thoroughly enjoying it.
I haven't had a problem with the focuser.
It seems very smooth, and handles quite a lot of weight.
Frankly its better than any GSO focuser I have.
Is there something I should watch out for?

Steve



I have the same scope and picked it up knowing that the focuser had issues. I works OK but has a "lumpy" fine focus. Spent a lot of time on it and couldn't eliminate it. I traced it to the 3mm pin axle. Looking at it closely the crescent relief ground in the pin isn't even, so with each rotation the high spot creates the "lump." Picked up a used Moonlight, but I'll have to try the tig wire trick. Then I can sell the focuser with a good conscience.

Is this scope Kunming, too?
Thanks


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