APCC pro refraction modeling for nomad setup #APCC #Mach2GTO


Andrea Lucchetti
 

Hi,
I have a Mach2.
From what I have understood, APCC can take into account refraction when using a model.
I wonder if it is possible to create a "transparent model", whose only effect would be to calculate refraction based on latitude, temp, humidity and celestial coordinates.

I have a nomad set up and prefer not to invest time in running a model, at least during summer when the night is very short .
Thank you
Andrea


Chris White
 

Interesting question.  I've been thinking about how useful the refraction based on temp and humidity actually is and whether it is worth in vesting in a THUM device or just running a model just based on the pointing matrix. 

FWIW- I know another user who sets up each night and if I remember correctly he runs an 80 to 120 point model all before it's dark enough to image.  So you could do the same as long as you arrive at your site with enough time to setup and get the model done before you would start imaging anyway. 


Ray Gralak
 

Hi Andrea,

 

> From what I have understood, APCC can take into account refraction when using a model.

> I wonder if it is possible to create a "transparent model", whose only effect would be to

> calculate refraction based on latitude, temp, humidity and celestial coordinates.

 

Yes, you can do that, but it would not take long to create a small model. If you have a model from a previous night that may no longer be valid, you can uncheck all of the pointing terms except the refraction checkbox, like in this screenshot, which shows a tracking rate correction for refraction only:

 

 

That said, you would get more accurate tracking with a model. The model will compensate for polar alignment error, flexure, and orthogonality errors. Typically APPM can run through 2-3 points per minute which would allow you to create a 60 point model in less than 30 minutes.

 

-Ray

 

> -----Original Message-----

> From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Andrea Lucchetti

> Sent: Tuesday, May 11, 2021 3:25 PM

> To: main@ap-gto.groups.io

> Subject: [ap-gto] APCC pro refraction modeling for nomad setup #APCC #Mach2GTO

>

> Hi,

> I have a Mach2.

> From what I have understood, APCC can take into account refraction when using a model.

> I wonder if it is possible to create a "transparent model", whose only effect would be to calculate refraction based

> on latitude, temp, humidity and celestial coordinates.

>

> I have a nomad set up and prefer not to invest time in running a model, at least during summer when the night is

> very short .

> Thank you

> Andrea


Dale Ghent
 

On May 12, 2021, at 09:30, Ray Gralak <iogroups@siriusimaging.com> wrote:

That said, you would get more accurate tracking with a model. The model will compensate for polar alignment error, flexure, and orthogonality errors. Typically APPM can run through 2-3 points per minute which would allow you to create a 60 point model in less than 30 minutes.
To add to Ray's comment, you can do the modeling run during twilight, usually during nautical dusk. Plate solving doesn't require anything in the way of fidelity; only that a sufficient number of stars can be detected. Doing it then will avoid stepping on your actual imaging time which, I presume, would start during astronomical dusk at the earliest.

/dale


Andrea Lucchetti
 

thank you everyone.
I need to be quicker in setting up the rig: my last night out was in November and this doesn't allow me to build a routine...
in the future I'd like to run a small model before imaging, but for now I like the trick suggested by Ray.
I am curious to see how long unguided I can go, with a mach 2 polar aligned on the refracted pole and refraction keyed in.
andrea