Argo Navis & TPAS

[Starkler]

Have any of you argo navis users out there tried setting up the TPAS function?
Does it work well for you?

I had a play with it this evening started off with a 6 star model.
I calculated for IE only and got a result of +6.8+-2

After fitting that model I did a run of 12 stars and got the following results:

RMS =5.3 (was 8.8)
PSD =7.1 (was 10.4)

CA =107.5+-36.5
IE =8.1+-1.7
NPAE =-81.6+-31.6

I tried adding terms ECES and ECEC but they seemed to degrade the PSD, so I fitted the above model. A test run touring globulars seemed to work fairly well so I went back to compute and selected "USE NOW AND SAVE".

After powering off and back on again, I went back into "SET ERROR VALUES" and upon looking for the values calculated from the prior session they were all zeros :doh:

[dugnsuz]

Man, I've got to get an Argo Navis to figure out what the heck you're talking about!:rofl: :rofl: :rofl:
Cheers
Doug:thumbsup:

ps: sorry Starkler!!!!

[Dave47tuc]

Good to see your playing with the TPS feature Geoff.:thumbsup:

I have been following peoples results on Yahoo. Reason for that is I have the AN on the way for my mount:whistle:
There has been a hold up getting it but hopefully soon.:D

Last nights viewing was so cold i could not get past 2 hours. But in that time it was some of the best seeing I have had. No shimmer on the Moon at 180x and only a little at 225x. GRS on Jupiter was awsome:eyepop:

I have used lots of eyepiecs in my time but that 10 mm XW Penatax is the best I have used:eyepop: :eyepop: :eyepop:

Anyway keep it up on using the TPS ;) Good luck.:thumbsup:

[gary]

Good to see you performed a TPAS run.

It is also nice to know the RAW RMS of the data. You can always find the
RAW RMS value by spinning the DIAL clockwise in the REVIEW DATA submenu
until you reach the entry that says END OF DATA on the top line of the
display. The bottom line of the display will show either the RAW RMS or
FIT RMS. You can alternate between the two values by pressing ENTER,
spinning the DIAL until it shows the type of RMS you are interested in
examining and then pressing ENTER again.

The 'WAS' values you see when you perform a COMPUTE are not always the
same as the RAW RMS. The 'WAS' values are what you would get if the
current 'IN USE' model is applied to the data. The RMS and PSD values
you see are those that you would get if you were to apply the model
as defined in DEFINE MODEL. Therefore the 'WAS" values are a convenient
way of seeing at a glance whether the RMS and PSD drops when you
expermient with alternative models in DEFINE MODEL.

If you currently have a 'null' model IN USE, then the 'WAS' values will
be equivalent to the RAW values.



Just be sure that when you "USE NOW AND SAVE", that you keep pressing ENTER
until you see the COMPUTE submenu appear again. The reason for this is that
the values are only actually put in USE and SAVED when you press ENTER on
the final term. If you press EXIT at any time, the USE NOW and SAVE will be
cancelled. If you power off the unit prior to dealing with the last term, likewise
no terms will be saved.

I can't envisage any other scenario that would result in the values
not being saved except the above. but let me know if you experience any
further difficulty.

Also be sure to check out the Argo Navis User's Group on Yahoo
for further tips from time to time.

http://groups.yahoo.com/group/argo_navis_dtc

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

[Starkler]

I was hoping you would make an appearance in this thread Gary, your help is very much appreciated :) I have also been following the yahoo group, however not often as late.

The next chance I get I'll do another run or two and see if I get consistant results. Last night was my first time in trying it, with me running in and out between the scope and the pc to read instructions, so I was bound to mess something up.:ashamed:


Dave Im surprised you had good seeing, it was absolutely horrible at my place, worst night in ages :shrug:

[Dave47tuc]

Funny that. Mark also said he had great seeing also. :shrug: Must have something to do with us being on the Peninsula.

[gary]

It is normal for it to take two or three sessions to become familiar with,
however, from your initial posting, it sounds as if you are on the right track.
Drop me a line if you ever need assistance. I am looking forward to hearing
about your results from your next run.

Don't forget to try and get a good even distribution of sampled
stars in Alt and Az covering as much as the sky that is available to you.

Avoid double stars or stars whose identify of which you are uncertain.
I recommend computing and putting 'IN USE' a model after sampling every
few stars. This has the advantage that you start to benefit from better pointing
during the sampling run, thus minimizing the chance of misidentification.
Nothing will throw out your results more than a misidentified star.
This is where regular inspection of the residuals in the REVIEW DATA submenu
can assist in spotting any samples that have been obviously misidentified.

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

[Starkler]

Hi Gary, a few more questions if I may.

The CA term seems to be a rather large number at 107.5. My scope is a 10" f5 dobsonian and I collimate my secondary with a laser, and my primary with a barlowed laser, so i would think all should be pretty much spot on.
Does this large CA number suggest a problem in this area?

Does the quality of the initial 2 star alignment affect the quality of results of a subsequent TPAS run (assuming correct object identification)?

Thirdly, would a calculated models usefulness be more consistant and useful if my dob scopes base board was always oriented to the same direction each observing session? I'm thinking of the possibility of an off centre or non square azimuth pivot type error here.

footnote: When you buy an Argo Navis, you not only get the most powerful DSC on the market, you also get superlative after-sales service :)

[gary]

Hi Geoff,

You are more than welcome.



A couple of points.

Firstly, keep in mind that CA and NPAE have similar 'signatures'
and unless you sample a reasonable number of stars they can be
difficult to differentiate. Recommend you sample a larger number of stars
chosen with a wide spread of Altitudes. In particular make sure you also
include a sample of stars nearer the pole of the scope (i.e. the zenith) where
CA and NPAE can be better differentiated.

If you look carefully, your CA and NPAE terms are acting in opposite
directions with respect to each other. It may turn out that based
on the small sample size, the two terms are "borrowing" from each other
when in fact you may actually have predominantly one or the other.

Secondly, don't confuse optical collimation with pointing "Collimation
Error". Consider the following primary axes on your scope -
the Az axis, the Alt axis, the Optical axis and the nominal Pointing axis.
You can have all of the optical components within your OTA "collimated"
(i.e. all the optical components are in-line and parallel to each other).
However, you can still have the Optical axis out of collimation with respect
to the Pointing axis. In other words, where the telescope "looks" might
be different to where it "points". Optically, the image will be fine.
As far as pointing performance, however, such a scope will be deemed
to have a pointing "Collimation Error". This error can arise from a variety
of sources, including optics that are out of collimation, optics that are
not parallel to the Pointing axis or a Pointing axis that is not perpendcular
to the mount's Alt axis.

Your mount may have pointing Collimation Error, it may have
"Non Perpendicular Axis Error" whereby the Az axis and the Alt axis
are not perpendicular, or it may turn out it has a bit of both.

On a subsequent run, it will be interesting know your RAW and
FITTed RMS as well as the values for the terms. If any error turns out
particularly large, you may even consider correcting it mechanically
at some point in the future.

You can appreciate that given a mount can have all these geometric errors
as well as eccentric bearings, flexure etc., then any computerized pointing
system that can compensate for them is clearly no longer just a plain
"Digital Setting Circle", as nothing is particularly circular any more. :)
For this reason, Digital Telescope Computer is a more apt description.



No, it doesn't. The two are independent. When you peform a two star
alignment the system uses only those two stars plus computes the Altitude
Encoder Reference point from them if you have AUTO ADJUST ON. As soon
as you apply a TPAS model, it uses all the sampled stars plus peforms
effectively a "super Auto ADJUST" courtesy of the IE term. If you remove the
TPAS model by setting all the terms to zero, the system automatically reverts
to your original two-star alignment.

I like to sample a few stars, define, compute and put "in use" a model,
then sample a few more stars and repeat the process. Doing this will
not affect the overall result, i.e. one can simply sample a large number of
stars and then do a COMPUTE at the end. However, by refining a model
as you sample, you can take advantage of the better pointing performance,
thus minimizing the chance of mis-identifying a star from the pointing
performance you get from just the plain two-star alignment.



Once you have determined errors such as NPAE, you should save them
for use on a subsequent session by selecting the USE NOW & SAVE option.
On a subsequent session, you should define a model that keeps NPAE
at a fixed value (as well as any ECEC or ECES term if significant) and then
set IE and possibly CH to COMPUTE. You would then sample, say, 6 to
10 stars and then COMPUTE a model to determine those terms that need
to be freshly computed. When you do this, the system is also able to
internally compute an index error in Azimuth term that is analogous to IH for
polar aligned scopes. This then circumvents you having to align the mount in
a particular way on each session.

Since one cannot determine the zero point of the Az encoder from session
to session, there are some class of errors that are dependent on an absolute
Az position that cannot be determined. However, often these errors can be
'mopped-up' by existing terms and an Az pivot bolt that is mounted so
that the Az axis is not at right angles to the Alt angles is handled by NPAE.



Thank you. I appreciate that. You are welcome.

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

[Starkler]

Thanks so much Gary for your very comprehensive answers and help :)

Now if only the weather will cooperate I'll have this all down pat before next new moon :)