Help collimating a "classic" Tasco 11T-R 4.5" reflecting telescope

(i pulled this out of another thread as buried my real question in an
inappropriate thread)

Now, im posting a link of the back of the telescope.

http://home.maine.rr.com/benno/Image-08.jpg

you can see the 3 thumbscrews and 3 phillips head screws. since im
without a manual for this thing, how is it that i adjust the mirror
with these? do i loosen the thumbscrews and do fine adjustments with a
screwdriver to the phillips screw, or vice versa?


I'd like to take the whole darn thing off as a unit to clean it. Now,
heres another point in my confusion. how to get the back off. Not
shown in the pic are three small screws that screw through the red
tube into the back. to me, these look like they hold the back on, but
when i take them off, and tug on the back,nothing gives. granted i
could tug harder, but am reluctant to do so without all the facts.

I would guess that you would loosen the philips-head screws, collimate using
the thumbscrews, then tighten the philips-head screws just enough to hold, NOT
enough to change the collimation. If I had the scope, I would try this first,
and if that did not work, try the other way.
I believe that the three screws on the side are the ones you remove to take out
the cell. However, be sure to MARK one of these screws and the tube where it
goes in to be sure you get the cell back in the way it was, or you can lose
your collimation. Also, be sure you have something soft for the cell to fall
on when you pull it out in case it is difficult and you drop it. This advice
is from experience.
Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

"Fu Manchu" wrote in message
...
(i pulled this out of another thread as buried my real question in an
inappropriate thread)

I have since posted what you need in the earlier thread. If it is still not
clear, let us know.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try http://groups.yahoo.com/group/lunar-observing/
And the Lunar Picture of the Day http://www.lpod.org/
************************************



Now, im posting a link of the back of the telescope.

http://home.maine.rr.com/benno/Image-08.jpg

you can see the 3 thumbscrews and 3 phillips head screws. since im
without a manual for this thing, how is it that i adjust the mirror
with these? do i loosen the thumbscrews and do fine adjustments with a
screwdriver to the phillips screw, or vice versa?


I'd like to take the whole darn thing off as a unit to clean it. Now,
heres another point in my confusion. how to get the back off. Not
shown in the pic are three small screws that screw through the red
tube into the back. to me, these look like they hold the back on, but
when i take them off, and tug on the back,nothing gives. granted i
could tug harder, but am reluctant to do so without all the facts.

I believe that the three screws on the side are the ones you remove to
take out
the cell. However, be sure to MARK one of these screws and the tube where
it
goes in to be sure you get the cell back in the way it was, or you can
lose
your collimation.

???? You are going to lose collimation when you remove it. And it probably
isn't very well collimated currently. He will quickly learn the easy art of
collimating a newt.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try http://groups.yahoo.com/group/lunar-observing/
And the Lunar Picture of the Day http://www.lpod.org/
************************************


Also, be sure you have something soft for the cell to fall
on when you pull it out in case it is difficult and you drop it. This
advice
is from experience.
Clear, Dark, Steady Skies!
(And considerate neighbors!!!)

Just a note here. . .from the photograph, it appears that you need to set
the declination on the scope's mount to match your latitude. Do a Google on
"using setting circles."

--
Martin

On Wed, 11 Aug 2004 18:48:46 GMT, Fu Manchu wrote:

(i pulled this out of another thread as buried my real question in an
inappropriate thread)

Now, im posting a link of the back of the telescope.

http://home.maine.rr.com/benno/Image-08.jpg

you can see the 3 thumbscrews and 3 phillips head screws. since im
without a manual for this thing, how is it that i adjust the mirror
with these? do i loosen the thumbscrews and do fine adjustments with a
screwdriver to the phillips screw, or vice versa?


I'd like to take the whole darn thing off as a unit to clean it. Now,
heres another point in my confusion. how to get the back off. Not
shown in the pic are three small screws that screw through the red
tube into the back. to me, these look like they hold the back on, but
when i take them off, and tug on the back,nothing gives. granted i
could tug harder, but am reluctant to do so without all the facts.


You are wise to approach this task with caution. Rest assured that no
aspect of cleaning or collimating your Tasco newtonian involves rocket
science or similar arcana. To start with, lets define some terms, to
avoid confusion:

Mirror Cell Assembly: The mechanism which holds the (primary) mirror,
secures it to the tube, and allows for alignment and collimation.
In addition to the mirror, the mirror cell assembly usually consists of:

The Mirror Cell / Holder / Mounting Plate - The part which actually holds
the mirror.

The Back Plate - Connects the Mirror Cell to the tube wall. Sits behind
the
mirror cell.

The Collimation Screws - a set of three or six. Three thumbscrews are used
to pull the mirror cell toward the Back Plate; springs provide push in the
opposite direction. Or a set of six screws (three thumbscrews for pull,
and
three thrust screws for push) act to point and lock the mirror in
alignment.

(Tube) End Ring - usually a plastic reinforcing ring mounted at the ends of
the tube. Its function is that of a bumper - it keeps the tube-ends from
getting dented, and protects your walls and shins from getting scraped or
cut
by the tube's sharp (metal) edges.


(These aren't official nomenclature, just a convenience for communication.)

====


In your photo, the large black ring, with six collimations screws showing,
is
the back plate. On the other side of the back plate is the mirror cell.

The "three small screws that screw through the red tube into the back" pose
something of a problem.
- If they are long enough to go into the back-plate, then they are what
holds
the mirror cell assembly in place.
- If the screws are just long enough to go into the tube, but not the back
plate,
then there may be another set of screws under the end-ring.
- It is possible that the End Ring and the Back Plate are all part of the
same piece of plastic.


In any event, you should NOT have to touch the Collimation Screws to get
the mirror
cell assembly out.

However, before you start, make alignment marks where the end-ring meets
the tube,
and where the back plate meets the end-ring. These will help when it comes
time to
re-assemble the optical tube assebly, by merely lining up the respective
alignment
marks.


SUGGESTED PROCEDURE
1. Remove the three small screws from the end ring.
2. Attempt to rotate the back plate within the end ring.
This will tell if other screws are holding it in place, or if the
back plate and the end ring are one integral piece.
3. If the back plate rotates, try to remove the mirror cell assembly
by twisting and pulling (very carefully).
4. If the back plate does not rotate free of the end ring, try to lightly
push the end ring off the tube.
5. If additional hardware holds the back plate to the tube, remove it,
after first making new alignment marks where the tube and back plate
meet.
6. The mirror cell should now be easily removed. (Do so with care.)


Clean the mirror, according to previous instructions.

Re-assemble by reversing the disassembly process.

Collimate the telescope. There are any number of good websites which tell
you
how to do this. Some advise using specific collimation tools. If you do
not
have such tools, I have a site which allows adequate collimation without
them:
http://www.vvm.com/~piscescs/collimat/NoTools2.html


Cheers, and good luck,
Larry G.

Update. Primary and Secondary mirror out sucessfully, but with a
hitch. The damn backplate on this thing just wouldnt budge!! So i
carefully loosened up the thumbscrews and regular screws on the
backplate until the mirror came loose, the carefully reached down the
tube and pulled the whole assembly out the front, which barely fit
out. Once the mirror was out, i exerted some more daring in trying to
remove the backplate, but to no avail. I think possibly that the
metal in the screws holes on the backplate is somehow snagged on the
metal in the tube and that happend when they drilled and tapped during
original construction.

To my suprise, there were springs loading the mirror assembly against
the thumbscrews, which actually it turns out are thumbbolts. The
screws holding the mirror assembly in place are permanently affixed to
the mirror assembly, and it is to these that the thumbolts are
attached, so to put it back together and collimate i believe i would
have to tighten the thumbolts up snug, and then use the regular screws
to kind of push the mirror assembly against the spring loaded screws
for alignment.

http://home.maine.rr.com/benno/Image-08.jpg
http://home.maine.rr.com/benno/Image-09.jpg
http://home.maine.rr.com/benno/Image-10.jpg


Attached are some pics of the primary mirror assembly (which is of
suprising quality considering the cheap nature of this particular
telescope), the secondary mirror assembly (notice the fender washers
which im going to use to help shim the secondary mirror to more
closely align with the focuser hole instead of driving the alignment
screws waayy in to help hold it)

Next task is to clean the primary and secondary mirrors and center
mark the primary, and order a collimation set up. Here is a question,
are there any type of magic marker that will damaged the mirror
coating? Was thinking of marking the center of the primary with some
washable marker, putting a paper reinforcment ring around the center
for a nice laser target.

As far as a collimation setup, thinking of getting the deluxe laser
collimator from Orion, a .965" to 1.25" adapter assembly for the
collimator, and a 10mm and 25mm .965" zhummel plossl lenses.

Kind of ironic actually that this upgrade costs more than the original
scope probably did back in the 1980s when my parents brought it home.
But, i figured this is good practice in learing about the guts of a
telescope without much to lose as far as the scope is concerned, and
ill pass it along for my kids to play with some day. It will also
hold me over as i save up enough cash to buy a motorized base and a
newer scope down the road.

I think ill paint "chick magnet" on the side and send a picture and my
rebuild story to http://www.andysshotglass.com/DontDo.html when im
done, hehe.






On Thu, 12 Aug 2004 01:39:04 -0500, LarryG
wrote:

On Wed, 11 Aug 2004 18:48:46 GMT, Fu Manchu wrote:

(i pulled this out of another thread as buried my real question in an
inappropriate thread)

Now, im posting a link of the back of the telescope.

http://home.maine.rr.com/benno/Image-08.jpg

you can see the 3 thumbscrews and 3 phillips head screws. since im
without a manual for this thing, how is it that i adjust the mirror
with these? do i loosen the thumbscrews and do fine adjustments with a
screwdriver to the phillips screw, or vice versa?


I'd like to take the whole darn thing off as a unit to clean it. Now,
heres another point in my confusion. how to get the back off. Not
shown in the pic are three small screws that screw through the red
tube into the back. to me, these look like they hold the back on, but
when i take them off, and tug on the back,nothing gives. granted i
could tug harder, but am reluctant to do so without all the facts.


You are wise to approach this task with caution. Rest assured that no
aspect of cleaning or collimating your Tasco newtonian involves rocket
science or similar arcana. To start with, lets define some terms, to
avoid confusion:

Mirror Cell Assembly: The mechanism which holds the (primary) mirror,
secures it to the tube, and allows for alignment and collimation.
In addition to the mirror, the mirror cell assembly usually consists of:

The Mirror Cell / Holder / Mounting Plate - The part which actually holds
the mirror.

The Back Plate - Connects the Mirror Cell to the tube wall. Sits behind
the
mirror cell.

The Collimation Screws - a set of three or six. Three thumbscrews are used
to pull the mirror cell toward the Back Plate; springs provide push in the
opposite direction. Or a set of six screws (three thumbscrews for pull,
and
three thrust screws for push) act to point and lock the mirror in
alignment.

(Tube) End Ring - usually a plastic reinforcing ring mounted at the ends of
the tube. Its function is that of a bumper - it keeps the tube-ends from
getting dented, and protects your walls and shins from getting scraped or
cut
by the tube's sharp (metal) edges.


(These aren't official nomenclature, just a convenience for communication.)

====


In your photo, the large black ring, with six collimations screws showing,
is
the back plate. On the other side of the back plate is the mirror cell.

The "three small screws that screw through the red tube into the back" pose
something of a problem.
- If they are long enough to go into the back-plate, then they are what
holds
the mirror cell assembly in place.
- If the screws are just long enough to go into the tube, but not the back
plate,
then there may be another set of screws under the end-ring.
- It is possible that the End Ring and the Back Plate are all part of the
same piece of plastic.


In any event, you should NOT have to touch the Collimation Screws to get
the mirror
cell assembly out.

However, before you start, make alignment marks where the end-ring meets
the tube,
and where the back plate meets the end-ring. These will help when it comes
time to
re-assemble the optical tube assebly, by merely lining up the respective
alignment
marks.


SUGGESTED PROCEDURE
1. Remove the three small screws from the end ring.
2. Attempt to rotate the back plate within the end ring.
This will tell if other screws are holding it in place, or if the
back plate and the end ring are one integral piece.
3. If the back plate rotates, try to remove the mirror cell assembly
by twisting and pulling (very carefully).
4. If the back plate does not rotate free of the end ring, try to lightly
push the end ring off the tube.
5. If additional hardware holds the back plate to the tube, remove it,
after first making new alignment marks where the tube and back plate
meet.
6. The mirror cell should now be easily removed. (Do so with care.)


Clean the mirror, according to previous instructions.

Re-assemble by reversing the disassembly process.

Collimate the telescope. There are any number of good websites which tell
you
how to do this. Some advise using specific collimation tools. If you do
not
have such tools, I have a site which allows adequate collimation without
them:
http://www.vvm.com/~piscescs/collimat/NoTools2.html


Cheers, and good luck,
Larry G.