In the interest of
full disclosure, I have no financial stake in any of the companies
mentioned in the following article.
When it comes to
finding components for amateur telescope making, some areas of the
market are burdened with an embarrassment of riches while others are
anemic when it comes to options available to the consumer. When it
comes to small mirror cells or tubes, most ATMs are limited to a
small number of suppliers. When it comes to focusers, however, there
are dozens upon dozens of choices available to the amateur
astronomer. Recently it was necessary to replace the (broken) stock
plastic 1.25” focuser on my late model Orion “Deep Space
Explorer” Dobsonian. Since budget was a serious issue to
consider, I looked to the low end of focusers on the market. I
settled on the cheapest available focuser that still had the
appropriate racked-in to fully-extended height range without having
to reposition the secondary mirror. I also wanted to change from a
1.25” focuser to a 2” unit, so I went for the Orion 2”
cast-aluminum rack and pinion focuser manufactured by Synta.
When the focuser was
received, it was oozing excessive quantities of “alien snot,”
also known as “Synta Glue,” “Gluebricant” and
“Jeez, what the heck IS this stuff?” I don’t think
I will ever understand why so many Chinese companies lubricate their
components with this sticky grease. It actually detracts from the
functioning of the instrument, and it has terrible thermal properties
(stiffening when the temperature drops). The first order of business
was to degrease and relubricate the focuser. The unit had to be
completely disassembled and each component cleaned in a two step
process. First, liberal quantities of WD-40 were used to break down
the glue. Second, 409 degreasing cleanser was used to clear away the
WD-40/Glue mixture. This may have to be repeated to fully eliminate
all traces of the glue, and a toothbrush makes a great tool for
scrubbing in the notches between gear teeth in the R&P mechanism.
Afterward, apply moderate amounts of white lithium grease to the R&P
mechanism components and reassemble the focuser.
After reassembling the
focuser and installing it on my telescope, it moved reasonably
smoothly and the lock knob provided good tension control. The lock
knob is good and large, so I’m even able to adjust it with
gloves on. Focusing accurately at high magnification is difficult,
however, unless the tension knob is completely loosened. There are
also occasionally minor “jumps” and “jerks”
in the travel. Compared to the plastic unit my scope was originally
supplied with, however, it functions beautifully. High-end Crayford
units will still put it to shame.
The focuser has a
relatively low profile for a rack and pinion unit. This does,
unfortunately leads to the focus knobs sitting barely above the
focuser’s base, and fingers can be pinched between the two. As
for the plastic knobs themselves (made of a particularly brittle
variety of plastic), the knurled grip around the edges is
uncomfortable to grip. I’ve heard them being referred to as
“plastic teeth out for blood.” In the aforementioned
situation of fingers getting pinched between the focuser base and the
knob, these plastic teeth can inflict some painful damage. I took to
wrapping strips of electrical tape around the knobs to lessen their
painful nip. Luckily, multiple companies sell replacement focus knobs
for Synta units. I eventually intend to replace the knobs with
rubber-grip knobs, and hopefully ones of a slightly smaller diameter.
Apart from the
brittleness of the focus knobs themselves, the overall build quality
is reasonably high. The all-metal construction is a welcome relief to
the all-plastic focuser I was using previously. The included 2”
to 1.25” adapter is made of solid, anodized aluminum and fits
tightly into the focuser. 1.25” eyepieces correspondingly fit
tightly into the adapter. I don’t foresee any centering issues
with eyepieces or collimation tools.
This focuser is
certainly not perfect. It has several issues that cause it to come up
lacking compared to better focusers, even ones within Orion’s
product line. Ultimately, you get what you pay for. However, for only
7 dollars more than the cheaper plastic focuser it was replacing, it
does provide a decent, reasonable option for ATMs on a budget, or
owners of cheap plastic focusers looking for a modest upgrade.
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