The worst TASCO ever? - 911TR model
a...@waikato.ac.nz
I noticed a new? reflector in the TASCO catalogue called a 911TR.
The interesting thing about this telescope is that it has an aperture of 114.5
mm or 4.5 inches, but only has a focal length of 500mm, now my trusty
calculator tells me this means an f ratio of 4.4.
As Tasco can hardly produce a good mirror around f9/10 how can they produce
an f4.4 mirror that is any good?
I believe this f4.4 mirror is NOT parabolic.
The images produced by this telescope MUST be diabolical.
Has anyone ever bothered trying out this scope?
Have Tasco improved their optics?
Is this model the only TASCO worth owning?
I await all sensible posts (do not email me direct please)
--
Andrew Chambers
IJK Macintosh Support
University of Waikato
New Zealand
LAB...@gitvm1.bitnet
exactly what he deserves......nothing for something.
Tasco binoculars, microscopes, and rifle scopes are another matter, as they
are made by a different organization.
Leonard Abbey, F.R.A.S.
Georgia Tech Research Institute
Atlanta, Georgia, USA
lab...@gitvm1.gatech.edu
David R. Smith
>Please no flames, I just have to ask this question!
>I noticed a new? reflector in the TASCO catalogue called a 911TR.
>an f4.4 mirror that is any good?
No flames, eh?
>I believe this f4.4 mirror is NOT parabolic.
On what evidence?
>The images produced by this telescope MUST be diabolical.
>Has anyone ever bothered trying out this scope?
No flames, eh?
>Have Tasco improved their optics?
>Is this model the only TASCO worth owning?
No flames, eh?
Several months I cleaned and collimated a friend's 4.5" Tasco reflector of
900mm f.l. After that, its stellar diffraction pattern looked like it
should, and it performed well on the moon and planets. Sure, that scope
was worth owning. Whether it was worth buying is another matter: for the
money, I would probably go for a bigger-diameter Dobsonian. If I owned it
and didn't plan to trade up, I would buy some better eyepieces and a real
finder.
--
David R. Smith, HP Labs | "I like to get my hands dirty,
dsm...@hpl.hp.com | because it stimulates my mind."
(415) 857-7898 | -- Irwin Sobel
David Nash
>In article <1993Feb26.1...@waikato.ac.nz> a...@waikato.ac.nz writes:
>>Please no flames, I just have to ask this question!
>>I noticed a new? reflector in the TASCO catalogue called a 911TR.
>>As Tasco can hardly produce a good mirror around f9/10 how can they produce
>>an f4.4 mirror that is any good?
>
>
>On what evidence?
I don't know about this particular scope, but I do know that in one of Sears's
catalogs about a year ago, they listed a Tasco short-focus scope (looked
about f/5) that was described explicitly as having a "spherical" mirror.
>Several months I cleaned and collimated a friend's 4.5" Tasco reflector of
>900mm f.l. After that, its stellar diffraction pattern looked like it
>should, and it performed well on the moon and planets. Sure, that scope
>was worth owning. Whether it was worth buying is another matter: for the
>money, I would probably go for a bigger-diameter Dobsonian. If I owned it
>and didn't plan to trade up, I would buy some better eyepieces and a real
>finder.
Yeah -- those are probably the real weak spots in the Tasco 4.5" scopes.
From what little I've seen and heard, there is a substantial difference
between the 4.5" reflectors Tasco makes and the flock of refractors they
make. The former are often usable, whereas the latter tend to be bad
by almost any standards. One of my standards is the following: if the scope
comes with an eyepiece-end solar filter, stay away from it at all costs. The
manufacturer obviously doesn't care about your eyesight. These things are
way too common on small, inexpensive refractors. . .
>David R. Smith, HP Labs | "I like to get my hands dirty,
>dsm...@hpl.hp.com | because it stimulates my mind."
>(415) 857-7898 | -- Irwin Sobel
--
David Nash | Gradual Student, Chemistry
| University of Illinois (Urbana)
(dn...@uxa.cso.uiuc.edu) | This .sig is made of 100% recycled electrons.
(na...@aries.scs.uiuc.edu) | No binary trees were killed to make it.
David R. Smith
>From what little I've seen and heard, there is a substantial difference
>between the 4.5" reflectors Tasco makes and the flock of refractors they
>make. The former are often usable, whereas the latter tend to be bad
>by almost any standards.
Well, I guess that matches my experience. Another friend had a 60mm Tasco
refractor. Its objective was OK, but the other end was a joke. Point the
scope skyward, and the draw tube would slide out. The silvering on the
diagonal was corroded and pitted. The eyepiece retainer screw had stripped
its threads in the diagonal. The finder might just as well have been a
taped-on straw.
I should mention that the mountings on both scopes aren't any great shakes.
Hmmm, maybe I should have said that they ARE great shakes. Whatever. You
get the idea.
--
LAB...@gitvm1.bitnet
internal baffles stop the objective down to about 1/2 aperture. The
resulatant instrument is about f/30 to f/40, which tends to mask all
sorts of optical errors.
The objective lens looks impressive, but most of it is not used.
Once again, I would like to emphasize that I have not examined the model
911TR, so I don't know that this is the case with this particular
instrument.
VaxCat
>In article <93064.000...@GITVM1.BITNET> <LAB...@GITVM1.BITNET> writes:
>>The biggest sin of the Tascos, at least the ones I have seen, is that the
>>internal baffles stop the objective down to about 1/2 aperture. The
>
>hoopla, _Consumer Reports_ (yeah, I know, bear with me) tested a number of
>relatively inexpensive scopes: 50mm refractors to a Celestron 8" SCT. There
>
>>The objective lens looks impressive, but most of it is not used.
As an owner of one of these fine (not) optical instruments, let me share
my experience. They suck. =-) It was a 60mm refractor. Yes, the
aperature was baffled down (which baffles me =) to about half the
diameter of the objective. The mounting was shaky. And getting the
finder aligned with the objective was amusing at best.
Oh oh...this is what I loved best. The mounting was very sticky, hard
to turn and had a problem where it would shift (for no good reason)
while I was viewing. Being the handy-guy I am, I decided to take the
mounting apart, regrease stuff (it was filled with grease) and put it
back together right. Uh huh...bad idea. I discovered, after
reconstruction, that the viscosity of the original grease was the only
thing holding the poorly machined parts in anything close to being
properly aligned.
Basically, I'm not going to buy a scope again until I can afford
something decent. I found a local guy who sells inexpensive,
hand-figured (by him) optics and mountings etc. So I'm going to build a
scope myself from parts acquired from him. The tripod and mount from
that old piece of crap now serves as a unique plant holder! =-) And
the only thing I can think of to use the scope for is looking at certain
neibhors ;) and perhaps using it as the finder (with certain
corrections) for that REALLY BIG scope I'll get someday. =-)
>Yeah, as I've seen here before (and once heard through E-mail) their long-focus
>4.5" reflectors are often useable, once you replace the poor eyepieces and
>finder that they come with.
The worst thing about cheapy Japanese scopes is that they have that
goofy eyepiece size. Why...oh god...why can't they spend the extra 27
cents or whatever and put in 1 1/4 inch focusers?
Anthony Clifton
David Benn
About 8 years ago I paid $400 for a Tasco 11T, a 4.5" Newtonian Reflector.
Up until a few years ago I knew very little about eyepieces. I have since
replaced the crummy, low contrast Huygens eyepieces with Orthoscopics (and
one Kellner). It is no understatement to say that an eyepiece is one half
of the scope. Decent eyepieces make a HUGE difference. Constrast is better,
exit pupil is larger, general quality is better. This assumes of course
that you have reasonable optics (primary and diagonal mirror). My 11T's
primary optics are quite good.
The next thing to change is the finder. As has already been lamented in
this thread, the Tasco finderscope is terrible. The contrast is poor and
the mount is shoddy.
I replaced this with a more sturdily mounted finder which makes a lot of
difference. I couldn't even see Omega Centauri in the old finder!! Then
again, I guess you'll NEVER see it if you're in the North :-).
The next change was to ditch the wooden tripod with a solid pier with
simple cross-shaped feet and height adjustment screws. I had this made
quite cheaply ($50) by a local small engineering company from a simple
drawing I gave them. The mount was made from scrap metal and bushes connect
the mount with the equatorial portion of the mount.
The latter has made the scope more stable in addition to preventing the
tube from snagging as much by protruding tripod legs. After the scope is
knocked, the whole thing settles down more quickly.
The final addition was a clock drive (not a Tasco one, but I guess that'd
be okay). This makes life much nicer.
I also plan to get a 1.25" eyepiece adapter, maybe add another finder
(medium size) and get solid shaft RA and DEC controls.
All up, my old 11T is now worth over $1000. It's not perfect. The mechanism
of the equatorial mount frequently performs poorly, but the sights I get
through the eyepiece are darn good. In poor seeing my 4.5" performs better
than a 8" or 10" Newtonian, and it's cheaper!
Sure, I want a Meade LX3 or similar, but until I can afford it, my 11T
gives me a great deal of pleasure and I can use it for timings etc without
problems.
Regards...
--
db...@leven.appcomp.utas.edu.au - David Benn. Uni. of Tasmania at Launceston.
Once you are open to questioning rituals and time-honoured practices,
you find that one question leads to another. (Carl Sagan)