Quote:
Originally Posted by JohnG
Paul, there has been, and still is, a lot of discussion on the Gemini Group about the use of encoders or DSC's, the great majority say don't fit them, can cause some interference with the Gemini although I believe they are disabled by default in Version 4.
I have a new V 4.02 chip but am yet to fit it and see.
Cheers
JohnG
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Hi John,
Thanks for the post but please allow me to clarify.
When GM-8/G-11 users suggest not to fit encoders, they mean do not bother
connecting the encoders to the Gemini. In theory, the Gemini provides for
an encoder interface that would allow the user to slew the scope using
muscle power (PUSHTO) but still maintain its position (down to the resolution of the
encoders). However, apparently this feature has been problematic on the Gemini.
For this reason, the general advice is not to bother using encoders interfaced
to the Gemini.
However, that is not to say that you still can't install encoders and use them
in conjunction with a DSC/DTC interfaced to them. You can even keep the
Gemini in place and use both systems in parallel. Many users in fact do this.
We stock genuine Losmandy parts DSCH which are the encoders and hardware
for the GM-8/G-11 and DGC which are the Delrin Gear Covers that help
protect your cables and fingers from getting caught. See
here for details.
Our Argo Navis DTC is a popular choice for GM-8/G-11 owners.
Common feedback from these users is that they often prefer PUSHTO over
GOTO because of its fast, reliable and quiet operation and that they enjoy the
power of the Argo Navis user interface.
As I mentioned, some users use both Argo Navis and Gemini systems in
parallel and there are no problems whatsoever in doing this. The two
systems are entirely independent and will not interfere with each other.
Therefore in summary where you say, "a lot of discussion on the Gemini Group
about the use of encoders or DSC's, the great majority say don't fit them,
can cause some interference with the Gemini", that is not entirely correct.
The advice is you can fit DSC/DTC systems, you can fit encoders and you can
operate them in parallel with the Gemini without any problem, just don't
connect the encoders to the encoder port of the Gemini itself.
Finally, it also gives me an opportunity to mention another reason why
Argo Navis is a popular choice on these mounts. Argo Navis has an
in-built Telescope Pointing Analysis System (TPAS) that can analyse and
compensate for several systematic geometric, gravitational and eccentric
errors that are quite common in these mount/OTA combinations. It will
even assist with polar misalignment and unlike a simple drift test will
take the other errors into account simultaneously.
For Part 1 of a case study of using TPAS on a G-11, see this link here -
http://www.wildcard-innovations.com.au/group_post_5573/
In order to view the graphics, grab a free copy of the Adobe SVG plugin from
here -
http://www.adobe.com/svg/viewer/install/main.html
One of the important things about TPAS is that it provides you with
stastical feedback about your mount's raw and corrected pointing performance
along with hard statistics about the various systematic errors within the
mount/OTA. TPAS can make a world of difference for anyone considering
blind-pointing a CCD.
Thanks again for the post and hope the above clarifies this for yourself
and other GM-8/G-11 owners.
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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gary 
