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A Beautiful Small Telescope...but not for sale

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#1 bill1970

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Posted 03 August 2014 - 10:52 PM

In a recent Sky and Telescope there was an article about a homemade ultra fast Dobsonian Rich Field Telescope. It is a small gem at F 2.8 with a 6 inch mirror and very portable. There is only one problem, you have to build it yourself.

There are 8 inch 11 inch and 14 inch  SCT on many pages of the magazine. You would think that there would be a market for this gem of a scope. So why doesn't a leading manufacturer like a Meade or a Celestron build a scope like this for the general public?  It would be niche marketing since there is nothing like this for sale that I know of.



#2 Jon Isaacs

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Posted 03 August 2014 - 11:15 PM

Do you really want to deal with an F/2.8 Newtonian?  Definitely Paracorr 2 + 21mm Ethos territory.  Looking at the secondary size,  a 7 inch diameter tube  a 1 inch focuser height barely illuminates the center of the field with a 3.1 inch secondary..  It's pretty much a one trick pony. 

 

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#3 gnowellsct

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Posted 04 August 2014 - 03:34 PM

Do you really want to deal with an F/2.8 Newtonian?  Definitely Paracorr 2 + 21mm Ethos territory.  Looking at the secondary size,  a 7 inch diameter tube  a 1 inch focuser height barely illuminates the center of the field with a 3.1 inch secondary..  It's pretty much a one trick pony. 

 

Jon

 

Yes--and parabolizing an f/2.8 for mass manufacture would be difficult I think.  GN



#4 Shneor

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Posted 05 August 2014 - 04:34 PM

Where there's a price, there's a way. If there's a perceived demand for something like this neat scope, someone will manufacture that, but the price will be quite a bit higher than a standard 6" f/5. I'm sure it could be marketed as a travel scope, which by itself would justify a higher price. Adding a Paracorr or equivalent still take s lot less space and weight than the difference between this acopw and a 6" f/5.

#5 gnowellsct

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Posted 06 August 2014 - 12:00 AM

I just read that article and the guy who made that scope is a real ATM expert guru type.  It would be really fun to try that scope out.  How commercial versions would turn out is problematic.  

 

You can get a very nice rich field scope by dropping a 24 Pan Optic into a 4.5" Star Blast.  It won't keep up with the one in that article though.  But it really is a viable alternative to binoculars (nice steady mount) and the wide field views at low power are competitive with the views offered by short fl refractors.    Likely won't be able to juice it to 300x and like the reults, though.  GN



#6 Pinbout

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Posted 06 August 2014 - 06:43 AM

 

Do you really want to deal with an F/2.8 Newtonian?  Definitely Paracorr 2 + 21mm Ethos territory.  Looking at the secondary size,  a 7 inch diameter tube  a 1 inch focuser height barely illuminates the center of the field with a 3.1 inch secondary..  It's pretty much a one trick pony. 

 

Jon

 

Yes--and parabolizing an f/2.8 for mass manufacture would be difficult I think.  GN

 

 

 

not when they call this parabolized. they'll say, oh its wide field they don't need high mag, so they will give us this...

 

 

20140614_140137.jpg



#7 DAVIDG

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Posted 06 August 2014 - 12:45 PM

 Here is a spot diagram for 6" f2.8 parabola that covers 1/2 degree field of view.  The small black circle is the size of the Airy disk  so the amount  of coma is huge, even a small distance from the center of field. Having made fast parabolic mirrors, something this fast is very difficult. A far better opticial design would be Schmdit Newtonian which would have about 1/3 of the coma and much easier to commerically produce.  The old Celestron/Vixen "comet catcher" is a good example of this.

 

             - Dave Attached File  6f28newt.JPG   24.84KB   0 downloads



#8 bill1970

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Posted 06 August 2014 - 08:16 PM

Speaking of niche marketing, I was thinking of marketing it like the Questar 3.5 inch Maksutov-Cassegrain. This small telescope has been around about 50 years and was heavily advertised in Sky and Telescope and Scientific American in the early 1970s. It was very portable , had great optics and was quite expensive.( I think it cost $1,000 back then.) It found a market and no one tried to copy this unique design.



#9 gnowellsct

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Posted 06 August 2014 - 10:52 PM

Aurora I think it would be more meaningful (and interesting to me!) to see the spot diagrams with the paracorr included.  The reason being that its use is pretty much an expected condition of the design, just as a corrector plate is on an SCT.   I think there is a strong version of the paracorr for ultra-fast designs....maybe someone can clarify that point.  GN



#10 Astrojensen

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Posted 07 August 2014 - 04:37 AM

 

 

ultra fast Dobsonian Rich Field Telescope. It is a small gem at F 2.8 with a 6 inch mirror and very portable.

 

This one has almost all the characteristics you want and it's available now:

 

http://www.buytelesc...olic-astrograph

 

It's not a dob, but that's easy to fix and you don't have to build the scope yourself. 

 

 

Clear skies!
Thomas, Denmark








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