On Sat, 28 Feb 2004 17:48:36 -0600, Pete Rasmussen
wrote:

Lawrence,

A dealer for these just told me the 14mm WA requires approx. 3/8"
additional in-travel compared to an "average" eyepiece. That of
course a ballpark measure but seems less than the older SW's.

Pete, what I have found is that although all of the WA's require
appreciable in-travel, the 18mm Speers-Waler WA in particular requires at
least a full cm more in travel the next most in-travel requiring WA. I
hand held the eyepieces within the 2" focuser tube to achieve focus while
my wife measured the in-travel beyond where the shoulder of the focuser
resides with a ruler placed alongside the focuser and eyepiece. The
incredible difficulty in holding the eyepiece steady and optically
straight at focus by free hand made it impossible to gauge optical
quality, and also hard for my wife to make reliable measurements (as she
was freezing and totally disinterested in assisting in my project at the
time...). As I recall, it was the 7.5mm WA eyepiece which required the
least in-travel (all of them being different in this regard) and came to
focus with its base just about dead even with the shoulder of my 2"
focuser proper (which was fully racked in at the time of course). If a
1.25" to 2" adapter exists which maintains the original height of the 2"
focuser shoulder when a 1.25" eyepiece is seated, the 7.5mm WA would have
just reached focus with the focuser racked in fully to the bumper, and
with such an adapter in place. My current Orion 1.25" to 2" adapter
yields about a 1.2 cm rise above the shoulder of the 2" focuser proper, so
this is why none of the WA's reach focus in my scope as currently
configured.

My previous eyepiece champion for requiring the most in-travel (before I
acquired the WA's) was my 30mm Celestron Ultima. I would say that the
14mm Speers-Waler WA requires perhaps 3/8" more in-travel than the 30mm
Ultima, but by contrast it requires about 1.7" more in-travel than my
8.8mm UWA (my eyepiece which requires the most focuser out-travel in my
arsenel, and which I must presently seat out from the focuser shoulder a
wee bit to achieve focus, as a result of moving my miror forward upon
acquiring the 30mm Ultima no less). The 18mm Speers-Waler WA is easily
about a full 2" inward of the 8.8mm UWA to reach focus, on first
approximation. To say that this series (taken as a whole) requires only
3/8" more in-travel than the "typical" eyepiece is a stretch. I would put
it at more like 1" inward of the "typical" eyepiece (unless the UWA's in
general are considered to focus atypically far out).


Since the SW main housing is just under 2" dia., why not wrap the
lower section with tape and plug it in your 2" drawtube to study the
sky view? That way you could determine exact in-travel required and
how you liked it before altering your scope. We also happily get to
know your impressions soon on performance at f/5.2 in a Newtonian.

As it stands now, I have my eye set on a Moonlight Crayford focuser with
the optional 2.75" travel draw tube. $175 total with this option. My
1.25" overall travel focuser is not going to cut it for my planned head to
head test of Speers-Waler WA's vs. Meade UWA's. Convincing my wife of my
need for a new focuser is the next major hurdle I must face, followed by
tube cutting and focuser changing (if/when I win...). The standard
Moonlight ($165) with its 2" draw would only perhaps just provide the
required total span I need, with absolutely no room to spare (and I would
likely have to set the 8.8mm UWA out a bit from the fully extended focuser
shoulder in this case, as I do now anyway), so the 2.75" draw option looks
like a clear winner. With 2.75" of travel I may even be able to reach
focus with the 18mm speers-Waler WA and a Paracorr (with the Paracorr
requiring about 1/2" of additional in-travel), while still being able to
fully seat the 8.8mm UWA in the focuser. The Paracorr is not too critical
for my 13.1" f/5.23, but I'm working an ~ f/4.1 mirror (30") at
present.....

Lawrence Sayre
--
------------------------------------------------------------------------
My philosophy, in essence, is the concept of man as
a moral being, with his own happiness as the moral
purpose of his life, with productive achievement as
his noblest activity, and reason as his only absolute.

Ayn Rand (in the appendix to 'Atlas Shrugged')
------------------------------------------------------------------------