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Clean and Collimate

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#1 E Sully

E Sully

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Posted 18 April 2017 - 10:36 AM

   Well, the scope is 16 1/2 years old.  Years back I dealt with the capacitors, and gears had been been greased and adjusted.  
    It spent a few years stored away due to physical issues.  A little knee work, bicep tendon reattached, and a hip replacement.  ETX90 came out, but LX was a little too much weight.
    After enough recovery time, I decided this would be a good year to get it back into action.  First run everything went pretty well.  Tracking was good, but optics needed a tweak.  It was time to collimate.  One thing that also bothered me was the film on the inside of the corrector lens.  Years of out-gassing and such had left nice a haze.
    Since it is mostly cloudy with changing weather this time of year, I decided to pull it and give it it's first interior cleaning.  Precautions were taken.  I set it up on a sturdy table, towels placed in case of a slip.  I gathered the supplies.  Distilled water, 90% alcohol, cotton balls, Kleenex, exam gloves, camel hair blower brush, and a marker.
    Scope was set up on a sturdy table, angled so lens will not fall off, with a towel for the corrector lens set up front.  Allen screws taken out, retaining ring removed.  Found the factory marks, and added 2 more reference marks of my own.  I removed the corrector and set in with the camel hair brush blower, damp cotton balls, followed by tissues for drying.   No pressure.  Keep water away from mirror holder.
    Many cotton balls and tissues later, corrector looked great.  A little work with the camel hair blower and time to re-install.  The original cork spacers around the edges of the tube were shrunken and no longer keeping the corrector centered.  I made some new ones out of rubber, and secured it all together.
    While most of the nights are to cloudy to do much, one evening I was able to get a decent view of a star for collimation.  I went through the procedure of de-focusing the star with a 28mm lens and slightly turning the screws till I had a nicely centered disc.  Changed to a 9mm lens and did a little more fiddling.  Now the stars are nice and sharp.
    I had purchased a set of Bob's Knob's for the scope, but decided against using them.  There is no clearance if they are installed to put the dust cap on.   The knobs would hit the cover.  The directions state you can bend the cover out in the center to clear the knobs, but I don't like that idea.  The collimation does not need to be done too often, and using an allen key is not really difficult with the 8" scope.

    Next step is to see if I can get some imaging with the Nikon D70 my brother donated to me.  All I need is a clear sky.

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#2 MistrBadgr


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Posted 18 April 2017 - 04:15 PM

Thanks for the great post! ::)


Bill Steen

Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#3 RickScofield


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Posted 18 April 2017 - 05:36 PM

Good luck and welcome back..


#4 SBacon


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Posted 19 April 2017 - 06:23 AM

Great post! Looking forward to some celestial pics!



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