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APPM - The Astro-Physics Point Mapper
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Requirements
To use APPM with your mount you will need to have the following:
1) A full version of MaxIm DL, CCDSoft, or AstroArt. Meade DSI cameras are also supported but they
usually are not big enough to capture enough stars for reliable plate solves. Support for ASCOM cameras
will be coming soon.
2) The full version of DC3 Dreams PinPoint application. Version 6 of Pinpoint is preferred. In the future
other plate solving methods will be made available but we believe this is the best solution available at this
time.
3) Optional - we recommend that you purchase a THUM temperature/Humidity sensor. This will allow
APCC to compensate for changes in temperature and humidity for the purposes of calculating refraction
accurately.
Using the Astro-Physics Point Mapper (APPM)
The APPM is a very powerful and versatile mapping tool. It's primary purpose is to create, and then run a
point mapping that will provide the error-data needed for APCC to create a model which can then be used
to determine corrections to both the pointing and the tracking of your mount. The point mapping can be
custom tailored to your system, and even has a mapping strategy to facilitate domed observatories that
may have rather narrow slits.
Before beginning an actual mapping run, make sure that your system is as mechanically sound as is
possible. Models are predictive tools. They answer the question: "Based on previous results, how
should I (the model) adjust the GoTo coordinates to increase pointing accuracy, and how should I adjust
the tracking rate to achieve more accurate tracking?" No model can adequately predict random events.
If it isn't repeatable, it can't be modeled! Flopping, shifting, cable jerks and even strong wind gusts that
are not identically repeatable will spoil an otherwise good model. So make sure that everything is tight.
Make sure your cables are free to follow the system throughout its entire range of motion, and make sure
that they don't impose a heavy weight-burden on the end of the scope. Be sure that you have minimized
mechanical backlash. (but DO NOT set any backlash compensation in the software or in the keypad!)
In general, you will want to begin by running a point mapping in APPM to create a model in APCC.
For your first try, we suggest that you run a smaller mapping on the order of 50 or so points. Then run
a small verify run of around 30 points to see how much the pointing has improved.
Begin the process by setting up each of the tabs in APPM. They are described in detail in the
sections that follow. It is important to get the settings right, so invest some time in doing a good job
on this.
Make sure that you have set up your Meridian Limits and Horizon Limits in APCC if you wish them to
be included in the point mapping.
Spend some time changing the parameters in the Measurement Points Tab to see how they affect the
point mapping.
Run your point mapping. As the mapping progresses, make a mental note of the magnitude of the
errors that are being displayed. A screen shot might also be a convenient way to document the errors.
These are the raw pointing errors that the model will try to correct. Note that they will vary
considerably in different parts of the sky.
© 2015 Astro-Physics, Inc.