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  #81  
Old 03-12-2008, 04:22 PM
gary
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Quote:
Originally Posted by erick View Post
If I found the targets were coming up a bit far from centre of 35mm Panoptic, I just did a quick "Mode Align" on the object and carried on. Hope that is a reasonable approach to take.
Indeed it is and it one approach that we recommend. In the face of finite
geometric fabrication errors within the mount, the error residuals will
be smallest in the vicinity of the alignment stars. So re-aligning in the
region you are currently observing in can take advantage of this.

Quote:
Randomly toured constellations or "20 deg around that spot" for non-stellars. Saw many new objects. It made finding small planetaries a breeze!
Brilliant! That is what we like to hear.

Fingers are crossed that this summer brings plenty of good observing opportunities!

Best Regards

Gary Kopff
Wildcard Innovations Pty Ltd
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  #82  
Old 03-12-2008, 04:48 PM
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koputai (Jason)
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Quote:
Originally Posted by erick View Post
How is everyone else going?
I was intending to buy new, but a 2nd hand AN with encoders came up at a price too good to refuse. I'm half way through installing it (some mods due to having a GSO scope but Lightbridge encoder kit) and it's looking good so far.

Cheers,
Jason.
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  #83  
Old 04-12-2008, 06:54 AM
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Gary I got offered a unit at a very good price by another maker and was wondering can I fit an argo to the supplied mounting hardware?

IT has 4000 step encoders ?... Another looming problem with my az
mounting situation is my az bolt is glued ( thanks dad) into the ground
board.. are the newer encoders bigger height wise ?.
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  #84  
Old 04-12-2008, 02:46 PM
gary
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Quote:
Originally Posted by nightstalker View Post
Gary I got offered a unit at a very good price by another maker and was wondering can I fit an argo to the supplied mounting hardware?

IT has 4000 step encoders ?...
Hi Graham,

Thanks for the post.

Indeed you can. Argo Navis is fully compatible with the encoders found on
legacy DSC systems. The encoder cable will also simply plug and play.
Argo Navis has setup parameters menus were you can define the AZ STEPS
and ALT STEPS settings appropriately.

Quote:
Another looming problem with my az
mounting situation is my az bolt is glued ( thanks dad) into the ground
board.. are the newer encoders bigger height wise ?.
The new 10,000 step encoders are the same height as their predecessors.
You can find a mechanical drawing on our web site here -
http://www.wildcard-innovations.com....ncoder_dim.gif
If you study it, the thread above the shaft is 0.26" and the body 0.50", a total
of 0.76" (19.3mm).

I gather your existing Az pivot bolt is not "encoder ready"? If you can
remove it we can always create a custom encoder ready replacement for you.
One alternative is that you get a hole saw of the minimum diameter that allows
the existing bolt to the cut out.

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
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  #85  
Old 04-12-2008, 03:32 PM
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koputai (Jason)
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Gary,
What are the maximum and minimum steps/rev that the AN can handle (or realistically use).

Cheers,
Jason.
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  #86  
Old 04-12-2008, 05:53 PM
gary
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Quote:
Originally Posted by koputai View Post
Gary,
What are the maximum and minimum steps/rev that the AN can handle (or realistically use).
Thanks for the post.

The menus allow step counts up to 9,999,999 steps. However,
when using the encoder interface, one also needs to take
into account the encoder sampling rate. Estimating your
maximum slew speed in degrees/second combined with a
knowledge of the encoder sampling rate can then allow you to
design the appropriate amount of gearing.

The following may also be helpful.

As you are aware, Argo Navis can be powered from a set of AA
batteries. The encoders are the most power hungry devices in
the system. In order to conserve power, Argo Navis powers
them on, samples them, then powers them off, thousands of
times per second. Since the encoders are sampled, there is a
maximum 'tick rate' at which the encoders can be turned and
still read reliably. In communications theory, the Nyquist
Criteria
says that one needs to sample a signal at least
twice the rate at which the signal is changing, in order to
sample it reliably.

Even when Argo Navis is powered from an external DC source
with the encoders permanently powered on, (achieved by SETUP
ENC TIMING, TON=xx, TOFF=0), the unit still samples the
encoders. In this case, the maximum sampling rate is around
16,000 samples per second. Hence the maximum slew rate
should not exceed 8000 times a second for the Nyquist
Criteria not to be violated. Working backwards, one can then
determine by how much you can gear the encoders based on
what your expected maximum slew rate is likely to be.

For a 10,000 step encoder geared 1:1, you can slew at
approx. ((16000/2)/10000) * 360 = 288 degrees per second.
The 16000/2 is owing to the Nyquist rate. Therefore you can
also work backwards and if you know in advance what your
maximum slew rate will be you can then determine the max.
number of encoder steps for one 360 degree revolution and
hence your gearing.

Anecdotally, on a colleague's 20" Dob we use quite a lot, we
have been running 56K steps on the Alt axis and 10K on the
Az axis for many years and never seen an encoder sampling
error message and this scope is purely PUSHTO.

The User Manual, in the section on SETUP ENC TIMING,
provides the sampling rates for various settings of the
SETUP ENC TIMING parameter. Using these numbers, one
can trade-off sampling rate/slew speed for battery life.

On some other GOTO scopes, rather than via the encoder port,
encoder data is supplied to Argo Navis via the serial port.
On these scopes, step counts in the millions are not
uncommon. However, for your PUSHTO configuration on a small
scope, I would recommend you aim for something around 10K to
30K steps per 360 degree resolution of the mount.

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
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  #87  
Old 04-12-2008, 07:56 PM
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GrahamL
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Thanks gary

having a good look at my az bolt tonight and scrapeing off a little epoxy I realised the old man didn't machine the bottom bolt/bush out of one piece of brass as I had always thought.. I now have two seated brass bushes
18mm od which are currently drilled to 5 /16 which can presumably drilled out a little more to take an encoder ready bolt ?
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  #88  
Old 04-12-2008, 08:28 PM
gary
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Quote:
Originally Posted by nightstalker View Post
Thanks gary

having a good look at my az bolt tonight and scrapeing off a little epoxy I realised the old man didn't machine the bottom bolt/bush out of one piece of brass as I had always thought.. I now have two seated brass bushes
18mm od which are currently drilled to 5 /16 which can presumably drilled out a little more to take an encoder ready bolt ?
Hi Graham,

If enlarging the hole, possibly think about accommodating some bushes
with 1/2" (12.7mm) I.D. We could supply an encoder-ready Az pivot
bolt that would slip right into them. In this instance, the encoder would be
mounted above the pivot bolt. Therefore you need to ensure that there
is sufficient clearance as the edge of the OTA passes over where the top
of where the encoder will be. Watch out for any fans or collimation nuts/bolts
to make sure they won't come into contention either.

An alternative is to keep the bushes there and fit a 5/16" Az pivot bolt
which then goes to a timing pulley/belt arrangement. We have exactly something
like this for the LightBridges and mounts such as the GSO truss 16".
Check out the images in the Az installation instructions for a GSO truss 16
on our web site here to see what I mean -
http://www.wildcard-innovations.com....s/gso16_az.pdf
This arrangement has a slightly lower height profile compared to mounting the
encoder directly into the bolt, if clearance is an issue.

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
Phone +61-2-9457-9049
Phone +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au
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  #89  
Old 04-12-2008, 10:38 PM
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koputai (Jason)
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Gary,
Thanks for the comprehensive post re encoder counts. Great info.

Regards,
Jason.
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  #90  
Old 31-12-2008, 02:17 PM
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Kevnool (Kev)
Fast Scope & Fast Engine

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Hi Gary was reading a post today in genearal discussion ,and with the leap second ,how does the Argo-Navis correct this......I,m betting the answer is really simple......Happy new year Gary and Cheers ....Kev.
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  #91  
Old 31-12-2008, 03:23 PM
gary
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Quote:
Originally Posted by Kevnool View Post
Hi Gary was reading a post today in genearal discussion ,and with the leap second ,how does the Argo-Navis correct this......I,m betting the answer is really simple......Happy new year Gary and Cheers ....Kev.
Hi Kev,

We keep track of it in the firmware. The 34 seconds tends to play a significant part
in some solar system object calculations.

There is a plethora of time standards that are arithmetically inter-related.

People have been messing with time keeping for thousands of years. Back in Sept
1752, there is a whole two weeks missing from the calendar when the English
moved from the Julian to the Gregorian calendar. People actually came out in
the street and protested "Give us back our two weeks".

Happy New Year!

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
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  #92  
Old 31-12-2008, 03:36 PM
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Kevnool (Kev)
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Poor ole September got a rough deal......Cheers Kev.
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  #93  
Old 04-01-2009, 12:37 PM
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Well I got some encoders and cable for x-mass .. so let the fun begin

I was kindly given an encoder ready bolt .. which I had some doubts about being able to fit to my existing ground board as the bush needed to be removed (glued in there)and drilled out for the larger bolt.Thankfully I smacked it out without much damage and was able to flip it to get a nice snug fit again..the torn ply underneath will be hidden by the locking plate..which I had to make another of as the overall thickness of the rocker box /ground board stopped the bolt locking down by about 5 mm.

The pole for the ago navis is 32 mm I'm planning to run the cable down the inside of the tube atm.

a few pics and a birds eye view of proceedings so far
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  #94  
Old 04-01-2009, 12:42 PM
gary
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Thumbs up Good luck with the install

Quote:
Originally Posted by nightstalker View Post
I was kindly given an encoder ready bolt .. which I had some doubts about being able to fit to my existing ground board as the bush needed to be removed (glued in there)and drilled out for the larger bolt.Thankfully I smacked it out without much damage and was able to flip it to get a nice snug fit again..
Hi Graham,

Happy New Year!

That is excellent news. We look forward to hearing how you progress.

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
Phone +61-2-9457-9049
Phone +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au
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  #95  
Old 04-01-2009, 12:56 PM
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Same to you gary .. No tricks to putting the encoders into those nylon bushes in the bolt?.. seems a tight fit .. though the old volume pot
I tried first fits very snug in there.. thats a better much idea than messing about tapping the bolt I'll look at that when I do the alt mount.. is the bush glued in there?

cheers graham
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  #96  
Old 04-01-2009, 01:31 PM
gary
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Quote:
Originally Posted by nightstalker View Post
Same to you gary .. No tricks to putting the encoders into those nylon bushes in the bolt?.. seems a tight fit .. though the old volume pot
I tried first fits very snug in there.. thats a better much idea than messing about tapping the bolt I'll look at that when I do the alt mount.. is the bush glued in there?

cheers graham
Hi Graham,

Once the bolt is in place, since it is the type that has a nylon sleeve in the
well where the encoder goes, just push the encoder shaft tight into there
by pressing carefully down. No tricks involved and indeed it will be a tight fit.

To remove, carefully pull the encoder vertically upward. Because of the
forces involved, avoid performing this operation unnecessarily. This
will then minimize the risk of ever damaging the encoder. Once the bolt is
in place and secured, then it is time to push the encoder in. Also check that the
OTA will clear the encoder as it swings over it.

Normally the bushes aren't glued in there.

If the fit is not tight enough, wrap a segment of Scotch tape around the encoder
shaft to enlarge its O.D. and then push it into the nylon sleeve.

Best Regards

Gary
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  #97  
Old 07-01-2009, 12:03 AM
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koputai (Jason)
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Woohoo!!
I completed mounting my encoders this arvo, and gave the AN its first run tonight. What a marvellous little device! Even though the moon is out, it's humid, and the light polution is terrible, I braved the mozzies for about two hours just having fun with the AN. Will have to do some more reading of the manual to get a bit more efficient at using it, but so far, so good.

Cheers,
Jason.
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  #98  
Old 07-01-2009, 02:16 PM
gary
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Quote:
Originally Posted by koputai View Post
Woohoo!!
I completed mounting my encoders this arvo, and gave the AN its first run tonight. What a marvellous little device! Even though the moon is out, it's humid, and the light polution is terrible, I braved the mozzies for about two hours just having fun with the AN. Will have to do some more reading of the manual to get a bit more efficient at using it, but so far, so good.

Cheers,
Jason.
Hi Jason,

Great to hear you wouldn't let warm temperatures, light pollution and mosquitoes
get in the way of a good night out!

Best Regards

Gary Kopff
Wildcard Innovations Pty Ltd
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  #99  
Old 12-01-2009, 03:23 PM
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been giving spme thought as to how mount the alt encoder
any thoughts most welcome .. I might make up a bush and slightly oversize the hole in the mounting mounting bracket to allow a little bit of adjustment.. though I'm pretty sure the centre of rotation is at the intersection of those two lines.

The tangent arm is 2mm brass I had a piece of lying around .. A little heavier than I would of hoped for
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  #100  
Old 12-01-2009, 04:36 PM
gary
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Arrow

Quote:
Originally Posted by nightstalker View Post
been giving spme thought as to how mount the alt encoder
any thoughts most welcome .. I might make up a bush and slightly oversize the hole in the mounting mounting bracket to allow a little bit of adjustment.. though I'm pretty sure the centre of rotation is at the intersection of those two lines.

The tangent arm is 2mm brass I had a piece of lying around .. A little heavier than I would of hoped for
Hi Graham,

Looks good. Rather than increase the overall circumference of the mounting hole,
you might want to consider milling it into a slot whose major axis is parallel to the
cross bar on the Alt trunnion. That will allow you to move the encoder side to side.
For the vertical axis, you might want to consider some mechanism to raise or
lower the entire bracket itself. Rather than fasten it directly with wood screws
onto the cross bar of the trunnion, possibly insert a couple of self-threading
brass inserts into the crossbar first. Then fasten the bracket into the self-threading
inserts using machine screws. One can then adjust the bracket in the vertical
direction and then fix it in place with appropriate washers and hex nuts.

Scott Tannehill posted a procedure in PowerPoint format entitled
"Version 4.0 Locating ALT axis on Dobsonian.ppt" which you can find in the
Files section of the Argo Navis User's Group.
http://tech.groups.yahoo.com/group/a...vis_dtc/files/
this can be useful to help center the encoder.

The 2mm brass for the tangent arm is a bit heavy-ish but should be fine.
Refrain from fastening the far end solidly to the side of the rocker.
Use a shoulder screw on the side of the rocker and carefully mill then file a
slot with a transition tolerance in the end of the tangent arm that just slides over
the shoulder screw.

Best Regards

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