Why not helical focusers?
- pakarinen
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Why not helical focusers?
I'm curious why almost all scopes come with R&P or Crayford-style focusers as opposed to helical. Helical are much lighter, less complex and therefore more robust, and probably much cheaper to manufacture.
Just a random thought rolling around my brain like a pea in an empty coffee can...
Just a random thought rolling around my brain like a pea in an empty coffee can...
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I drink tea, I read books, I look at stars when I'm not cursing clouds. It's what I do.
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AT50, AT72EDII, ST80, ST102; Scopetech Zero, AZ-GTi, AZ Pronto; Innorel RT90C, Oberwerk 5000; Orion Giantview 15x70s, Vortex 8x42s, Navy surplus 7x50s, Nikon 10x50s
I drink tea, I read books, I look at stars when I'm not cursing clouds. It's what I do.
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AT50, AT72EDII, ST80, ST102; Scopetech Zero, AZ-GTi, AZ Pronto; Innorel RT90C, Oberwerk 5000; Orion Giantview 15x70s, Vortex 8x42s, Navy surplus 7x50s, Nikon 10x50s
- OzEclipse
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Re: Why not helical focusers?
True helical only focusers have limited travel. The micro-focusers only have 10mm travel. If they did have long travel, they'd take forever to do a long travel unless combined with a draw tube slide.
My old telescope has a home made twist and slide friction focuser. Having used it for 44 years, I really like it and I am used to it.
Friends of mine using it for the first time have commented that once I explained how to use it, they really like it.
The brass tubes are a smooth twist friction slide. You twist as you pull or push, the resulting inward outward movement is very very smooth and fine, as precise as the Feather Touch on my 18"dob .
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Joe
My old telescope has a home made twist and slide friction focuser. Having used it for 44 years, I really like it and I am used to it.
Friends of mine using it for the first time have commented that once I explained how to use it, they really like it.
The brass tubes are a smooth twist friction slide. You twist as you pull or push, the resulting inward outward movement is very very smooth and fine, as precise as the Feather Touch on my 18"
Joe
Amateur astronomer since 1978...................Web site : http://joe-cali.com/
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Re: Why not helical focusers?
The Telescopics focuser installed on my 8" Newt (circa 1972) is an R & P but the Rack portion is setup up to also function as a helical focuser for fine focus. Don't know why these aren't produced anymore, they work like a dream!
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO
∞ G&G Scopes: #1: Meade 102mm f/7.8 #2: Bresser 102mm f/4.5
∞ Guide Scopes: 70 & 80mm fracs -- The El Cheapo Bros.
∞ Mounts: iOptron CEM70AG, SW EQ6, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
∞ Cameras: #1: ZWO ASI294MC Pro #2: 662MC #3: 120MC, Canon T3i, Orion SSAG, WYZE Cam3
∞ Binos: 10X50,11X70,15X70, 25X100
∞ EPs: ES 2": 21mm 100° & 30mm 82° Pentax XW: 7, 10, 14, & 20mm 70°
Searching the skies since 1966. "I never met a scope I didn't want to keep."
∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO
∞ G&G Scopes: #1: Meade 102mm f/7.8 #2: Bresser 102mm f/4.5
∞ Guide Scopes: 70 & 80mm fracs -- The El Cheapo Bros.
∞ Mounts: iOptron CEM70AG, SW EQ6, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
∞ Cameras: #1: ZWO ASI294MC Pro #2: 662MC #3: 120MC, Canon T3i, Orion SSAG, WYZE Cam3
∞ Binos: 10X50,11X70,15X70, 25X100
∞ EPs: ES 2": 21mm 100° & 30mm 82° Pentax XW: 7, 10, 14, & 20mm 70°
Searching the skies since 1966. "I never met a scope I didn't want to keep."
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