Orion Skywatcher 120 Questions 
Author Message
 Orion Skywatcher 120 Questions

Dear SAA knowledge base:

I recently picked up a Skywatcher 120 (F8.3) at a good price.  Overall the
scope works nicely but seems to have a good case of the shakes, trying to focus
can be quite an experience, much like my old C8, adjust and wait for the
vibration to die.  Reminds me of why I like DOBs....  <g>  But I would like to
resolve this issue if possible.

This scope has the EQ-3 mount which is apparently a CG-4???

I do have the option of mounting the EQ head on an extremely sturdy tripod if
that would help matters but my suspicion is that the head itself contributes
significantly.

Anyway, I would appreciate suggestions on improving this situation and any
pointers to websites that may address issues on improving these mounts.

Thanks for your time and thoughts.....

Jon Isaacs



Thu, 28 Oct 2004 23:42:42 GMT
 Orion Skywatcher 120 Questions
Jon,

I have an original Vixen GP that I use for most things, and it is fine.
But the maximum weight allowance is 16 lb. Unfortunately, they never
stated the maximum angular moment allowed. This is likely the source of
your problem as that telescope (5" f/8") is fairly large. Even on a GP
mount, a 4" f/12 is basically at the limit of the mount.

The EQ-3 is essentially a clone of the old Vixen Super Polaris mount.
The EQ-4, sometimes known as the EQ-5 is a clone of the Vixen Great
Polaris mount.

I currently have an EQ-6 with the 6" f/8 refractor on it. The mount is
balanced with 20 pounds of counterweight. Focussing is terrible at
300x... lots of jiggle. I might suggest that the 6" f/8 is at the limit
of the EQ-6 in terms of angular moment.

The most prominent problem is the slop in the equatorial head. A quick
rebuild solves much of this. I have seen a few pages about rebuilding
the EQ-4, and GP mounts. There may be one out there for the EQ-6.

The next problem is the tripod... aluminum tripods are just not the
thing to use. Switch to a heavy wood tripod or a permanent pier. The
tripods that ship with the clone EQ-3 and EQ-4 are typically an aluminum
extrusion (unless swapped out by thge distributor) which is lighter and
cheaper than wood.

Good luck.

Eric.

Quote:

> Dear SAA knowledge base:

> I recently picked up a Skywatcher 120 (F8.3) at a good price.  Overall the
> scope works nicely but seems to have a good case of the shakes, trying to focus
> can be quite an experience, much like my old C8, adjust and wait for the
> vibration to die.  Reminds me of why I like DOBs....  <g>  But I would like to
> resolve this issue if possible.

> This scope has the EQ-3 mount which is apparently a CG-4???

> I do have the option of mounting the EQ head on an extremely sturdy tripod if
> that would help matters but my suspicion is that the head itself contributes
> significantly.

> Anyway, I would appreciate suggestions on improving this situation and any
> pointers to websites that may address issues on improving these mounts.

> Thanks for your time and thoughts.....

> Jon Isaacs



Fri, 29 Oct 2004 08:22:22 GMT
 Orion Skywatcher 120 Questions
John

Universal Astronomics should be able to solve your tripod problem.
They provide a heavy duty wooden surveyors tripod and adapter.

Anderson Instruments also sells surveyors tripods but you will need to
go to Universal Astronomics for the adapter..  Im using the wooden
surveyors tripod to hold my cg-5 mount and 6" refractor. The wooden
tripod made a huge improvment.

Rich


Quote:
>Dear SAA knowledge base:

>I recently picked up a Skywatcher 120 (F8.3) at a good price.  Overall the
>scope works nicely but seems to have a good case of the shakes, trying to focus
>can be quite an experience, much like my old C8, adjust and wait for the
>vibration to die.  Reminds me of why I like DOBs....  <g>  But I would like to
>resolve this issue if possible.

>This scope has the EQ-3 mount which is apparently a CG-4???

>I do have the option of mounting the EQ head on an extremely sturdy tripod if
>that would help matters but my suspicion is that the head itself contributes
>significantly.

>Anyway, I would appreciate suggestions on improving this situation and any
>pointers to websites that may address issues on improving these mounts.

>Thanks for your time and thoughts.....

>Jon Isaacs



Sat, 30 Oct 2004 12:48:43 GMT
 Orion Skywatcher 120 Questions

Quote:

>Dear SAA knowledge base:

>I recently picked up a Skywatcher 120 (F8.3) at a good price.  Overall the
>scope works nicely but seems to have a good case of the shakes, trying to focus
>can be quite an experience, much like my old C8, adjust and wait for the
>vibration to die.  Reminds me of why I like DOBs....  <g>  

Yes *we* all know how much you prefer the rumored stability of Dobs :^)

Quote:
>But I would like to
>resolve this issue if possible.

Fix the problem. Replace the grease in the focuser with lithium grease and
adjust the tension and fit until it is smooth and easy to turn. Most
Synta scopes suffer from this same problem. They can also benefit from
appropriate shims (teflon) as well.

Quote:
>This scope has the EQ-3 mount which is apparently a CG-4???

Probably not a good mount though I am sure there will be those that
disagree. Adjust all axis until there is minimal backlash and no slop.

Quote:
>I do have the option of mounting the EQ head on an extremely sturdy tripod if
>that would help matters but my suspicion is that the head itself contributes
>significantly.

<sacrasm>

Be creative Jon. Dob mounts are soooo {*filter*}y superior why don't you use
one of those ?

</sarcasm>

Seriously though .... piggyback it on the infamous Stable Dob we all
hear so much about and if the {*filter*}y thing still shakes then it has to
be the focuser

Quote:
>Anyway, I would appreciate suggestions on improving this situation and any
>pointers to websites that may address issues on improving these mounts.

http://www.***.com/
http://www.***.com/

come join us on the "dark side" Jon .... you'll be glad you did :^)

See the appropriate page for upgrading the CG-5. Almost everthing there
will work for that as well.

Bill



Sun, 31 Oct 2004 01:39:22 GMT
 Orion Skywatcher 120 Questions

Quote:

>>But I would like to
>>resolve this issue if possible.
>Fix the problem. Replace the grease in the focuser with lithium grease and
>adjust the tension and fit until it is smooth and easy to turn. Most
>Synta scopes suffer from this same problem. They can also benefit from
>appropriate shims (teflon) as well.

This is the sort of information I was looking for.  The focuser is quite tight
and this does seem to be part of the problem.

Quote:
>>This scope has the EQ-3 mount which is apparently a CG-4???

>Probably not a good mount though I am sure there will be those that
>disagree. Adjust all axis until there is minimal backlash and no slop.

Sounds like a plan, I will give that a try.

Quote:
>>I do have the option of mounting the EQ head on an extremely sturdy tripod
>if
>>that would help matters but my suspicion is that the head itself contributes
>>significantly.

><sacrasm>

Actually this is not sarcastic at all.  Rather a friend gave me a tripod which
apparently was originally meant to be used with a 35 mm Panavision type moving
picture camera.  It is very nicely made, very sturdy, it handles my 235 lbs
jumping on it very nicely.

Mounting the EQ-3 head on this tripod is an option if it would help.

Quote:
>Seriously though .... piggyback it on the infamous Stable Dob we all
>hear so much about and if the {*filter*}y thing still shakes then it has to
>be the focuser

Actually I am interested in trying to improve this mount so that the scope can
perform as it should.  There is no doubt that a DOB mount is more stable but
that is not the issue here, rather I would like to make the necessary
improvements to this scope and mount so that I can enjoy advantages that it
offers.

Quote:
>come join us on the "dark side" Jon .... you'll be glad you did :^)

>See the appropriate page for upgrading the CG-5. Almost everthing there
>will work for that as well.

>Bill

Well, I am not selling anything but I do hope to get a feel for what a medium
aperture, medium focal length achromat can do.  

Thanks for your pointers and I will work on the focuser and mount ASAP.

jon isaacs

jon isaacs



Sun, 31 Oct 2004 05:36:13 GMT
 Orion Skywatcher 120 Questions
Dear Jon
I had the same experience with my 120. My question is would you want a GEM
mount anyway? Ok, if you want to do atrophotos, but for a visual astronomer,
a GEM is literally a pain in the back.
If you look at the mechanics of the EQ3, you will see that the two axes of
rotation are stabilised by about 4mm of metal contact on the worm to gear
surfaces and the gears themselves (on mine anyway) must have been lathed by
a novice - I measured 5 mil play between the gear and the shafts. No way
that is ever going to be stable. Adding a Heargraves strut (see S&T of
Sept.2001) and filling the tripod legs does help a lot. HOWEVER for the
ultimate solution I threw away the EQ3 (actually I converted the tripod into
a coffe cup and snack holder) and commisioned a machine shop to build a copy
of the LightSpeed telescope Wagon mount, on a solid oak/carbon fibre  pier
mount. (I would have bought one, but since I am from South Africa and having
toilet paper for currency it would have cost me 2 months salary after
converion to US$1600). If you are from US, check out that mount at
http://home.att.net/~Riddel.LightSpeed/wagon.htm. My buddies drool over the
mount and it is the most stable thing I have ever seen (as in zero vibration
= zero dampening time). A more affordable option, without the drives will be
Nisur systems Taurus mount and their P3 pier mount for total $400). see
http://nisursystems.com/index.html.
Happy gazing
Carlos


Mon, 01 Nov 2004 06:59:37 GMT
 Orion Skywatcher 120 Questions

Quote:
>I had the same experience with my 120. My question is would you want a GEM
>mount anyway? Ok, if you want to do atrophotos, but for a visual astronomer,
>a GEM is literally a pain in the back.

One of the reasons I bought this scope was that it had a GEM.  Every other
scope I own is on some sort of an Alt-AZ mount and I figured it was time to see
what I was missing.  I had already done the fork thing so I thought it was time
to do the GEM thing.  

Well, so far my impression is that it is better than the Fork thing.  

But I am sticking with this EQ, I already got the solid Alt-AZ thing under
control.

<g>

jon isaacs



Mon, 01 Nov 2004 10:14:54 GMT
 Orion Skywatcher 120 Questions


Fri, 19 Jun 1992 00:00:00 GMT
 Orion Skywatcher 120 Questions


Quote:
> One of the reasons I bought this scope was that it had a GEM.  Every other
> scope I own is on some sort of an Alt-AZ mount and I figured it was time
to see
> what I was missing.  I had already done the fork thing so I thought it was
time
> to do the GEM thing.

> Well, so far my impression is that it is better than the Fork thing.

Point taken Jon, you like a GEM and nothing wrong with it. However I would
like to make a case for a better GEM mount. Unless you are handy with a
lathe and willing to rebuild your EQ3, you will always have a second class
mount. Astronomy boys site has a nice discussion on how to improve the CG5
mount, and will translate directly to the EQ3
(http://www.astronomyboy.com/cg5/index.html). Coincidentally I took a long
lunch today and visited my local Cats (local optics shops that stock Synta
and Orion) and saw their new EQ-6 mount. Now that is a well-built piece of
equipment, with a sturdy tripod reminiscent of a Meade. I am not sure
whether Orion stocks that one yet.
I do believe in wooden tripod legs, not just because of their dampening
properties, but also their beauty. I would recommend a good Nisur pier mount
(wooden legs, acrylic central pier).
Perhaps the EQ-6 head on a Nisur pier mount? Now that will be a groovy
combination.
Regards
Carlos


Tue, 02 Nov 2004 06:01:23 GMT
 
 [ 9 post ] 

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