Re: APPM requirements


Ray Gralak
 

Hi Jeff,

I’ve just wondered about the practicality for a non-permanent setup, and the conditions where APPM is needed for
unguided imaging… eg the focal length where APPM becomes effective over just the encoders on a polar aligned
mount.. Or is the benefit simply repeatable pointing accuracy?
A pointing model will improve both tracking and pointing accuracy, including accounting for drift from polar alignment error.

However, if you move the mount you will need to recreate the model from scratch, but that should not take much time. Usually, APPM will do between 2-3 points per minute, so you should easily be able to do a 50-point model (25 points per side) in about 15-25 minutes. You can do this even before the skies are completely dark, thus not losing any imaging time.

The accuracy of a model is roughly related to the square root of the number of points on each side. For example, going from 25 to 100 points per side will roughly double the tracking and pointing accuracy (because 100 is four times 25 and the square root of four is two!).

-Ray

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Jeffc
Sent: Tuesday, March 23, 2021 1:54 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] APPM requirements

Speaking of “requirements”…

What’s the thought on using APPM with a non-permanent setup?

Fwiw, I’m using the mach2 now with an st8300m + fs128 at about 1040mm focal length and am “visually” seeing
decent round stars with 5 minute unguided exposures.

I’ve only had the mount for a couple weeks, but I also used the 130GT at 614mm with (iirc) 20 minute exposures
unguided.

Yes, objects do not land in the center of the chip on a goto , but it is usually close enough such that I can plate solve
, sync , then goto again (for proper framing).

I’m guessing APPM might help with longer exposures , and also with objects low on horizon affected by
atmospheric distortion… the latter would be nice to correct for. At this point I image objects when they are fairly
high on the sky.

What would be the guidelines for a “portable” setup ?
Eg
a) create model at the site but it could be reused for the same location?
b) or.. it is necessary to re-create model if the mount is moved.. ie polar alignment is re-done?

I’ve just wondered about the practicality for a non-permanent setup, and the conditions where APPM is needed for
unguided imaging… eg the focal length where APPM becomes effective over just the encoders on a polar aligned
mount.. Or is the benefit simply repeatable pointing accuracy?

Thx




On Mar 23, 2021, at 12:39 PM, Dean Jacobsen <deanjacobsen@...> wrote:



Ray's APCC/APPM on-line manual is a great place to start.

https://www.siriusimaging.com/Help/APCC/index.html

There is a specific section for APPM that I used to get everything set up.
--
Dean Jacobsen
http://astrophoto.net/wp/
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