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 Starmasterô Portable Telescopes
 Rick Singmaster
Super FX Series Telescopes

The Super FX telescopes from Starmaster represent a new frontier in commercially produced telescopes - they are the first large commercial telescopes offered at a focal ratio F/3.3.
  • 20" F/3.3, quartz primary 1.25" thick (and 4.5" m.a. quartz flat)
  • 22" F/3.3, Pyrex primary 1.5" thick
  • 24" F/3.3, Pyrex primary 1.6" thick

Eyepieces, coma correctors, cooling, and performance

At F/3.3, visual observing is uncompromised and made even more amazing by the Paracorr and awesome Ethos eyepieces from TeleVue.  The new Advanced Paracorr, due out early in 2010, promises even better performance with wide field eyepieces like the 20mm Ethos.  Objects are as sharp as with slower instruments, except the observer's feet are much closer to the ground, or on the ground!

Starmaster build quality means that these fine instruments stay in collimation as they move to objects all over the sky, high up and near the horizon.  Carefully designed mirror cells support the optics properly at all altitudes, and are built solidly to minimize flexure that could affect collimation.  Simply put, once properly collimated the telescope stays aligned.

A 22" F/3.3 at Okie-Tex 2009

Additionally, the fast focal ratio means that those doing imaging and observing using high-sensitivity cameras (a.k.a. video astronomy, see John VeDepo's article here) can use shorter exposure times than slower instruments while their captures a wider field of view.

This line features another Starmaster first - a telescope with all quartz optics.  Inspired by Mike Lockwood's 1.25"-thick 20" F/3 mirror, the 20" F/3.3 features a 1.25"-thick quartz mirror, the same thickness as the 14.5" and 16.5" FX telescopes' Pyrex primary mirrors.  These three models currently are the fastest cooling and lightest weight primary mirrors (of comparible size) in the commercial Dob market.

Conclusion - the Super FX line provides the same performance as other telescopes, but in a much shorter package.

As Mike Lockwood says, "Given good optics and seeing, the main factors limiting performance in a telescope are thermal equilibration and proper collimation.

Starmaster has addressed these factors and minimized their effect to ensure maximum performance and maximum quality observing time.

You can read about Mike's 20" F/3 MX, the telescope that proved that F/3.3 visual telescopes were doable, in three articles linked from the Online Articles page.

Just what ladder or chair (if any) do I need?

Rick with a 30" F/3.3The 20" F/3.3 allows seated observing all over the sky.  Rick and Mike both enjoy seated observing because it is more comfortable, less fatiguing, and it allows the observer to see more detail in both deep-sky and planetary views.

The only disadvantage to seated observing is trying to get your friends out of your observing seat so you can observe!

If you're about 6' tall, the 22" F/3.3 requires one step to view at the zenith, and seated observing is possible over most of the rest of the sky.  (See image at the top of this page.)  The 24" F/3.3 needs one more step.

Weights, dimensions, eyepiece heights, etc. are provided on the Telescope Specs page.  For other questions, give Rick a call.

Customer and user reports

Here's a link to an article about the Fall 2009 Chiefland Star Party.  A brief report by Rick is followed by comments from two Starmaster owners who report on a 30" F/3.3 and other Starmaster telescopes.  Also see Rick and Mike's report about the 2009 Okie-Tex Star Party and the 22" F/3.3 Super FX that Rick brought.

Comparing the 20" and 22" F/3.3 Super FX telescopes

A number of people have asked, besides price, what's the difference between the 20" and 22" F/3.3 Super FX?  This is a great question, because there are some noteworthy differences depending on what is most important to the future owner.

The advantages of the 20"x1.25" quartz blank over the 22"x1.5"
Pyrex blank are 1) lighter weight, 2) faster cooling time, and 3) reduced effect
on the mirror figure while cooling.

The 20" will have a 1.25"-thick mirror, so it will cool faster than the
1.5"-thick 22" F/3.3. (Currently a 20" diameter piece of quartz is the largest
piece I can get for prices that are reasonable and appropriate for Rick's

The quartz blank is thinner, weighing ~27 lbs. for the 20"x1.25" blank, while
the 22"x1.5" weighs 41 lbs. This is a 14 lb weight savings, important for those
with back problems.

Quartz has a coefficient of thermal expansion (CTE) that is about 1/6 that of
Pyrex. This means that the mirror, with one curved surface and one flat
surface, will distort less during cooling due to the internal thermal gradient.
This gradient usually causes mirrors to appear overcorrected while cooling.  (Mike notes this effect on his thin Pyrex 20" F/3 was definitely moving this direction until it
cools off a short time later.)

Thinner mirrors seem to change correction more, but they cool faster, so the
effect goes away sooner. Quartz allows one to utilize a thinner mirror and
greatly reduce the effect of this cooling-induced correction change.

So, under serious cooling, the 20" quartz mirror will likely show less
correction error than the 22", and it will definitely cool off faster. This
provides more quality observing time. Once the 20" and 22" are roughly
equilibrated, the 22" will have the advantage due to larger aperture.

Just for perspective, keep in mind that we're comparing two thin mirrors, and
both will cool off much more quickly than 2"-thick optics.

Finally, in terms of physical size, the 20" scope will be shorter and more
compact in size than the 22", and that may be important for those with smaller
vehicles or narrower doorways to pass through between scope storage and scope

All major components of Starmaster Telescopes are made with pride in the United States of America by small, community based companies.

-Cancelled orders will be subject to a restocking fee which will be equal to 15% of the BASE price of the telescope, NO EXCEPTIONS.
-Orders are not transferable without permission of Starmaster Telescopes and will be subject to additional fees.
-We are now accepting international orders for telescopes 22" in aperture and under.

For comments or questions about this site, email Starmaster Portable Telescopes.

Rick has a second passion besides astronomy - Click here to see what it is!