Dobsonian Tilt ?

[duncan]

G,day all,

I'm curious to know whether a Dob base could be tilted to match latitude of where someone lives? This then is the next question. If so would something like ArgoNavis then be able to track whatever the scope is aimed at? Of course alignment to the pole would have to be spot on? I new it would only be a matter of time before i asked something that would sound crazy.
I layed in bed 2 nights ago and couldn't sleep. Three hours later i'd designed an observatory from the ground up. My poor missus didn't like the tossing and turning. So i told her i'd finally gone over the edge,and promptly left the room,lol.

Cheers from an insane,
Duncan

[bojan]

Duncan,
If you tilt dobsonian then it would not be dobsonian any more :-), it would become equatorial mounted telescope.
For driving dobsonian though, have a look at Mel Bartels website
http://www.bbastrodesigns.com/BBAstr...ted_Telescopes

[duncan]

Hi Bojan,
Thanks for the reply. Had a look at the site you mentioned. I think i'll stick to the Skywatcher 10" newt on Eq6 mount. Then maybe at a later date get a much bigger Dob (aperture fever)lol.

Cheers,
Duncan

[gary]

Hi Duncan,

Thanks for the post.

Originally Posted by duncan

I'm curious to know whether a Dob base could be tilted to match latitude of where someone lives?

This is in fact commonly done using what is known as an "equatorial
platform" or "equatorial table". There are a few popular commercial models
around, such as these.
Many amateur telescope makers (ATM's) also fabricate their own.
Typically the platform has a drive motor that allows it to track at the
sidereal rate. This then turns an Alt/Az telescope, such as a Dob mount, into
a true equatorial telescope.

In fact, an equatorial mount is really just an Alt/Az mount that has been
tilted so as the mount's azimuth axis is now aligned to the polar axis.

Originally Posted by duncan

If so would something like ArgoNavis then be able to
track whatever the scope is aimed at? Of course alignment to the pole would have to be spot on?

The really beautiful part about Argo Navis is that the mount need not
be polar-aligned at all. It works equally well on equatorial and alt/az mounts
such as Dobsonians with or without equatorial platforms.

When using Argo Navis on a Dob, you simply need to perform an alignment
on two stars. After that, it "knows" where it is pointing. There is no requirement
to enter the date, time or location nor to level the mount. You don't need a GPS
unit.

To use Argo navis on a telescope, one simply needs to install a pair
of devices known as optical encoders to each axis of the mount.
These devices emit electrical pulses when they rotate and are interfaced
to Argo Navis via a cable. We can supply high resolution optical encoders
and the necessary hardware to mount them to a large variety of telescopes.
See here for a list of commercial mounts for which we can supply installation kits.
We are introducing a new kit for the Skywatcher Dobs on Monday 19th Feb 2007.
We can also assist ATM's with advice and components should they wish to
fabricate their own hardware.

Owing to this utility of not having to polar align the mount, for this reason
Argo Navis is the pointing solution of choice for an enormous number of
enthusiasts, many of whom are Dob owners. For example, Obsession
Telescopes and SDM Telescopes provide Argo Navis as an option with their telescopes
as the pointing solution of choice.

Getting back to the issue of equatorial platforms, as mentioned, these
are usually fitted with a drive motor that allows the mount to track
at the sidereal rate. However, as an alternative to equatorial platforms,
many users now use motorized slew and track systems whilst the mount
is still in an Alt/Az configuration. An excellent example of a commerical
slew and track system is the ServoCAT by StellarCAT in Arizona.
This unit allows for connection to two servo motors which can drive the scope.
It is also designed to then interface with Argo Navis. One simply dials
up the target object on Argo Navis, hits the GOTO button on the ServoCAT
handpad and the scope will slew and then track the target. Argo Navis performs
all the object offset and tracking rate calculations on behalf of the ServoCAT.
Since the mount is not equatorially aligned, both axis move simultaneously
at continually varying tracking rates.

For sound engineering reasons, it is not surprising that most of the world's
large professional mounts, such as found on the tops of mountains in Hawaii
and Chile, are also Alt/Az mounts driven in the same way.

Hope this answers you questions and your ideas aren't crazy at all.
You've simply re-invented the wheel without knowing it, for which you should
be congratulated.

By the way, Argo Navis is in use all around the world but happens to be designed
and manufactured right here in Sydney, Australia. Don't hesitate to contact me
if you are curious to know more as we have considerable expertise in this area
that we are more than happy to share.

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
Phone +61-2-9457-9049
Fax +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au

[Gargoyle_Steve (Steve)]

Duncan another member posted this pic a while ago, I think you'll find it interesting. I've been thinking about making one something like this myself.

[bojan]

And, just in case you missed the information on Bartel's website..
His software (which is distributed free of any charge) can handle both altazimuth and polar mount, with GOTO capability as well, if you want it.
B

[duncan]

Hi all,

Many thanks for all your replies. I'm sticking with the 10"newt on EQ6 to start with. Then i'll get the big Dob.That should keep the wife happy (not)lol.

Thanks again,
Duncan

[Starkler (Geoff)]

The problem with tilting a dob base is that the typical base is not designed to handle loads in anything but the vertical direction. Once inclined there are forces causing flexure in the rocker box sides, azimuth pivot issues and altitude bearings that need mods to prevent them from jumping off the base.
Another problem is the issue of the focuser ending up at strange and inconvenient angles.

[gary]

Originally Posted by Starkler

The problem with tilting a dob base is that the typical base is not designed to handle loads in anything but the vertical direction. Once inclined there are forces causing flexure in the rocker box sides, azimuth pivot issues and altitude bearings that need mods to prevent them from jumping off the base.

Hi Geoff,

Dave Kriege, co-author of "The Dobsonian Telescope" and founder and
owner of Obsession Telescopes, has told me much the same. Well designed
Dobs are simply not a matter of aesthetics and are instead based on sound
engineering principles backed by solid physics. On some designs, the
engineering assumption was made that the mount would be relatively level
with respect local gravity, otherwise its performance and handling could
be compromised. In these instances, motorised slew and track systems are
a preferred option over platforms, as the mount then does not need to be
tilted.

[ving (David)]

why would you want a dob when you can have an eq?

hehe

dave p. does something like this i believe