11 replies to this topic

[Hillbill]

Just a quick follow-up to my earlier post...  Here is a picture of the Questar receipt for my fast focus Questar, and a couple more pictures showing the factory installed fast focus hardware.  I find it hard to believe that Questar charged $548 to add this little qizmo.  Any thoughts?

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[Richard O'Neill]

It's custom work with a guarantee. That costs. You should see what they charge the government!

[Billydee]

Bill,

 

You have the Fast Focus II (Rack & Pinion Model) that was made between 1983 and 1989  It replaced the large box on the side of the Q (cam type, 1970-1983).  Your model was replaced in 1989 with a Threaded Rod version (10-24 TPI).  I believe your model was replaced because it is the most complex and the parts were very expensive.  The threaded rod model is much less expensive, 10-24 rod is very cheap.  The Fast Focus option is a very low production item and yours appears to be rather complex.  They had to modify the side of the control box for the two control knobs and design the second control knob to have a memory for it's preset position.  They had to modify the back of the control box to accommodate the tubular extension to allow the rack to slide to the desired length (I'm betting that extension costs about $150).  I am pretty sure they had to modify the mirror cradle to allow the rack to attach so mirror movement could happen.  The rack path support was probably a real bear to undertake and that pinon gear looks very custom made.  All this for probably less that 25 Qs over a 6 year period.  You got a bargain and a nicely engineered option.

 

Bill

Edited by Billydee, 16 November 2017 - 09:38 PM.

[Billydee]

Bill,

 

I just did a little cost study on off the shelf racks (good quality 9" long, 1/2 " wide and 1/2" high 24 TPI) cost $135.  The pinion gear in a good quality straight cut gear 1.5" in diameter costs $58.  Yours are angle cut (much more expensive) for better mesh.   All parts appear to be hand machined and were probably produced only when the item was ordered.  This is a very costly way to produce but is necessary on low volume options.

 

Bill

[Hillbill]

Thank you both for your input.  Bill, you really know your stuff!  When I got the scope, it was missing the 24mm Brandon and the full apature solar filter.  I feared that part or the fast focus was missing, as well.  I am relieved.

I am looking to replace the occular and filter.  Got any spares?

Many thanks,

Bill

[JamesMStephens]

What yea was this Questar made?

[Billydee]

Bill,

 

You don't have to worry, 100% of the Fast Focus is there and of the three FFs your 's is the cadillac.  Please give us the SN of your Duplex so James can know the year of production (with FF-II it had to be between 1983 and 1989).  Don't have e spare Full Aperture Solar Filter or a 24mm Brandon,  both sell real quick and usually show up on AMart every month.  

 

Note:  be sure you purchase a Questar threaded Brandon, Vernonscope (maker of Brandon) also makes a Brandon proprietary threaded EP and a non-threaded Brandon.

 

In addition to the three types of FFs Questar also makes a Rapid Focus Gearing option that uses the same rear knob (but slightly larger) that costs about $125 (in 2008) if installed at time of production.

 

Bill

[Hillbill]

Here it is.

Thanks again

Bill

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[Billydee]

James,

 

1987

 

Bill

[Hillbill]

BTW, what is the purpose of a fast focuser?

How is it used?

Edited by Hillbill, 20 November 2017 - 08:44 AM.

[Optics Patent]

Cheeky answer:  To focus fast.

 

Real answer:  Because it takes a lot of turns (10-20?) of the normal focus knob to go from 10 feet to infinity.  That's great for fine focusing on distant objects, but for birdwatchers, cinematographers and such, it's too time-consuming.  Instead of many turns, the whole focus range in is about one turn.  With a larger knob that mitigates the loss of fine precision, but the smooth mechanisms are still readily focused with precision.  Also with one smooth motion there may be less jarring of the image - important to cinema work.

[Hillbill]

Thank you, Ben!