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102mm F7 Kunming refractor comparisons

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#26 stevew

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Posted 18 June 2013 - 10:06 PM

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

Steve

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#27 stevew

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Posted 18 June 2013 - 10:10 PM

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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#28 Jon Isaacs

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Posted 19 June 2013 - 03:17 AM

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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#29 dennilfloss

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Posted 19 June 2013 - 05:22 AM

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

#30 Jon Isaacs

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Posted 19 June 2013 - 05:45 AM

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

#31 Agatha

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Posted 19 June 2013 - 10:08 AM

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. :crazy:
Anyway, my only point is to clarify company names. :). I hope his makes sense.

Best,

#32 Jon Isaacs

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Posted 19 June 2013 - 10:33 AM

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. :crazy:
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

#33 DaveJ

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Posted 19 June 2013 - 10:50 AM

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. :grin:

#34 CollinofAlabama

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Posted 24 June 2013 - 08:50 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.

#35 Jon Isaacs

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Posted 25 June 2013 - 12:59 AM

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

#36 CollinofAlabama

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Posted 15 July 2013 - 01:33 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.

#37 Geo.

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Posted 16 July 2013 - 10:55 AM

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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