Topics

Tip for creating horizon limits


Dale Ghent
 


I'm experimenting with defining horizon limits in APCC in conjunction with another project, and I was trying to figure a good way to get an accurate representation of my site's horizon lines into APCC without using the drawing tool. I suck at drawing, especially with a mouse, and the flattened, linear projection of the horizon tool in APCC adds additional challenge in terms of transcribing what you see.

You can also use the alt+az tools in the horizon tracking limits editor to "trace" the horizon using your telescope and camera/eyepiece, manually dropping points to form your horizon, but this seemed a little time consuming to me and I didn't quite want to set up my gear in the daytime to do this when there was also no nights in the forecast that had weather that was conducive to imaging (I've reached the stage of things where if I set up, I'm setting up to image. Damnit. :D )

So this led me to look into how APCC stores its horizon limit table and alternate ways of creating horizon lines with accuracy.  This led me to 2 findings:

1. APCC stores horizon limits in a flat text file with a simple format: 
<azimuth> <altitude>

A pair of space-separated numbers, one pair per line. Azimuth is a whole number from 0 to 359. Altitude is a floating point number, 0 to 90, and represents the lowest altitude that has clear sky at the corresponding azimuth. Obviously, there are 360 lines of this data in the file. The file is saved with the .hrz file extension, but it is otherwise a plain text file that can be edited in any text editor. 

2. Smart phones and tablets are brimming with inclinometers, and there are a few apps for both iOS and Android which can read these and, ultimately, log their values. Since I have an iPhone, I used an app called Theodolite which, if you're familiar with the instrument, puts a crosshair on the middle of your phone's video feed along with angle and rotation information. A similar app on Android is Dioptra.

In these apps, one turns on logging and traces the horizon with the phone as the app logs altitude and azimuth it is pointing at, usually in 1 degree increments. Once you trace a full 360 degrees, you can turn off logging and save the data. In the case of Theodolite on my iPhone, it saved it to my iCloud drive as a CSV file. I then opened it up on my Mac, extracted the Azimuth and Altitude columns, edited them to remove any duplicate azimuth entries or gaps (sometimes if you turn too fast, there is a gap in azimuth numbers). In the end I had 360 lines of accurate horizon altitude limits. I saved the file as a space-separated file with a .hrz extension and loaded it into APCC's horizon limits editor. The result is in the attached screenshot.

This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.


Ray Gralak
 

Hi Dale,

Since I have an iPhone, I used an app called Theodolite which,
if you're familiar with the instrument, puts a crosshair on the middle
of your phone's video feed along with angle and
rotation information. A similar app on Android is Dioptra.
This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.
That's a great tip. I will have to try it.

Thanks for posting this!

-Ray Gralak
Author of PEMPro
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver


-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Dale Ghent
Sent: Monday, December 14, 2020 8:09 AM
To: main@ap-gto.groups.io
Subject: [ap-gto] Tip for creating horizon limits


I'm experimenting with defining horizon limits in APCC in conjunction with another project, and I was trying to figure a
good way to get an accurate representation of my site's horizon lines into APCC without using the drawing tool. I suck
at drawing, especially with a mouse, and the flattened, linear projection of the horizon tool in APCC adds additional
challenge in terms of transcribing what you see.

You can also use the alt+az tools in the horizon tracking limits editor to "trace" the horizon using your telescope and
camera/eyepiece, manually dropping points to form your horizon, but this seemed a little time consuming to me and I
didn't quite want to set up my gear in the daytime to do this when there was also no nights in the forecast that had
weather that was conducive to imaging (I've reached the stage of things where if I set up, I'm setting up to image.
Damnit. :D )

So this led me to look into how APCC stores its horizon limit table and alternate ways of creating horizon lines with
accuracy. This led me to 2 findings:

1. APCC stores horizon limits in a flat text file with a simple format:
<azimuth> <altitude>

A pair of space-separated numbers, one pair per line. Azimuth is a whole number from 0 to 359. Altitude is a floating
point number, 0 to 90, and represents the lowest altitude that has clear sky at the corresponding azimuth. Obviously,
there are 360 lines of this data in the file. The file is saved with the .hrz file extension, but it is otherwise a plain text
file
that can be edited in any text editor.

2. Smart phones and tablets are brimming with inclinometers, and there are a few apps for both iOS and Android
which can read these and, ultimately, log their values. Since I have an iPhone, I used an app called Theodolite which,
if you're familiar with the instrument, puts a crosshair on the middle of your phone's video feed along with angle and
rotation information. A similar app on Android is Dioptra.

In these apps, one turns on logging and traces the horizon with the phone as the app logs altitude and azimuth it is
pointing at, usually in 1 degree increments. Once you trace a full 360 degrees, you can turn off logging and save the
data. In the case of Theodolite on my iPhone, it saved it to my iCloud drive as a CSV file. I then opened it up on my
Mac, extracted the Azimuth and Altitude columns, edited them to remove any duplicate azimuth entries or gaps
(sometimes if you turn too fast, there is a gap in azimuth numbers). In the end I had 360 lines of accurate horizon
altitude limits. I saved the file as a space-separated file with a .hrz extension and loaded it into APCC's horizon limits
editor. The result is in the attached screenshot.

This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.



 

that is super clever, well done! i will have to try this too



On Mon, Dec 14, 2020 at 8:09 AM Dale Ghent <daleg@...> wrote:

I'm experimenting with defining horizon limits in APCC in conjunction with another project, and I was trying to figure a good way to get an accurate representation of my site's horizon lines into APCC without using the drawing tool. I suck at drawing, especially with a mouse, and the flattened, linear projection of the horizon tool in APCC adds additional challenge in terms of transcribing what you see.

You can also use the alt+az tools in the horizon tracking limits editor to "trace" the horizon using your telescope and camera/eyepiece, manually dropping points to form your horizon, but this seemed a little time consuming to me and I didn't quite want to set up my gear in the daytime to do this when there was also no nights in the forecast that had weather that was conducive to imaging (I've reached the stage of things where if I set up, I'm setting up to image. Damnit. :D )

So this led me to look into how APCC stores its horizon limit table and alternate ways of creating horizon lines with accuracy.  This led me to 2 findings:

1. APCC stores horizon limits in a flat text file with a simple format: 
<azimuth> <altitude>

A pair of space-separated numbers, one pair per line. Azimuth is a whole number from 0 to 359. Altitude is a floating point number, 0 to 90, and represents the lowest altitude that has clear sky at the corresponding azimuth. Obviously, there are 360 lines of this data in the file. The file is saved with the .hrz file extension, but it is otherwise a plain text file that can be edited in any text editor. 

2. Smart phones and tablets are brimming with inclinometers, and there are a few apps for both iOS and Android which can read these and, ultimately, log their values. Since I have an iPhone, I used an app called Theodolite which, if you're familiar with the instrument, puts a crosshair on the middle of your phone's video feed along with angle and rotation information. A similar app on Android is Dioptra.

In these apps, one turns on logging and traces the horizon with the phone as the app logs altitude and azimuth it is pointing at, usually in 1 degree increments. Once you trace a full 360 degrees, you can turn off logging and save the data. In the case of Theodolite on my iPhone, it saved it to my iCloud drive as a CSV file. I then opened it up on my Mac, extracted the Azimuth and Altitude columns, edited them to remove any duplicate azimuth entries or gaps (sometimes if you turn too fast, there is a gap in azimuth numbers). In the end I had 360 lines of accurate horizon altitude limits. I saved the file as a space-separated file with a .hrz extension and loaded it into APCC's horizon limits editor. The result is in the attached screenshot.

This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.



--
Brian 



Brian Valente


Manusfisch
 

Brilliant Brian, thanks for sharing

TJF Mobile

On Dec 14, 2020, at 11:34, Brian Valente <bvalente@...> wrote:


that is super clever, well done! i will have to try this too



On Mon, Dec 14, 2020 at 8:09 AM Dale Ghent <daleg@...> wrote:

I'm experimenting with defining horizon limits in APCC in conjunction with another project, and I was trying to figure a good way to get an accurate representation of my site's horizon lines into APCC without using the drawing tool. I suck at drawing, especially with a mouse, and the flattened, linear projection of the horizon tool in APCC adds additional challenge in terms of transcribing what you see.

You can also use the alt+az tools in the horizon tracking limits editor to "trace" the horizon using your telescope and camera/eyepiece, manually dropping points to form your horizon, but this seemed a little time consuming to me and I didn't quite want to set up my gear in the daytime to do this when there was also no nights in the forecast that had weather that was conducive to imaging (I've reached the stage of things where if I set up, I'm setting up to image. Damnit. :D )

So this led me to look into how APCC stores its horizon limit table and alternate ways of creating horizon lines with accuracy.  This led me to 2 findings:

1. APCC stores horizon limits in a flat text file with a simple format: 
<azimuth> <altitude>

A pair of space-separated numbers, one pair per line. Azimuth is a whole number from 0 to 359. Altitude is a floating point number, 0 to 90, and represents the lowest altitude that has clear sky at the corresponding azimuth. Obviously, there are 360 lines of this data in the file. The file is saved with the .hrz file extension, but it is otherwise a plain text file that can be edited in any text editor. 

2. Smart phones and tablets are brimming with inclinometers, and there are a few apps for both iOS and Android which can read these and, ultimately, log their values. Since I have an iPhone, I used an app called Theodolite which, if you're familiar with the instrument, puts a crosshair on the middle of your phone's video feed along with angle and rotation information. A similar app on Android is Dioptra.

In these apps, one turns on logging and traces the horizon with the phone as the app logs altitude and azimuth it is pointing at, usually in 1 degree increments. Once you trace a full 360 degrees, you can turn off logging and save the data. In the case of Theodolite on my iPhone, it saved it to my iCloud drive as a CSV file. I then opened it up on my Mac, extracted the Azimuth and Altitude columns, edited them to remove any duplicate azimuth entries or gaps (sometimes if you turn too fast, there is a gap in azimuth numbers). In the end I had 360 lines of accurate horizon altitude limits. I saved the file as a space-separated file with a .hrz extension and loaded it into APCC's horizon limits editor. The result is in the attached screenshot.

This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.



--
Brian 



Brian Valente


 

It's great, but Dale is the guy who came up with this :)



On Mon, Dec 14, 2020 at 9:23 AM Manusfisch via groups.io <tjfischer653=mac.com@groups.io> wrote:
Brilliant Brian, thanks for sharing

TJF Mobile

On Dec 14, 2020, at 11:34, Brian Valente <bvalente@...> wrote:


that is super clever, well done! i will have to try this too



On Mon, Dec 14, 2020 at 8:09 AM Dale Ghent <daleg@...> wrote:

I'm experimenting with defining horizon limits in APCC in conjunction with another project, and I was trying to figure a good way to get an accurate representation of my site's horizon lines into APCC without using the drawing tool. I suck at drawing, especially with a mouse, and the flattened, linear projection of the horizon tool in APCC adds additional challenge in terms of transcribing what you see.

You can also use the alt+az tools in the horizon tracking limits editor to "trace" the horizon using your telescope and camera/eyepiece, manually dropping points to form your horizon, but this seemed a little time consuming to me and I didn't quite want to set up my gear in the daytime to do this when there was also no nights in the forecast that had weather that was conducive to imaging (I've reached the stage of things where if I set up, I'm setting up to image. Damnit. :D )

So this led me to look into how APCC stores its horizon limit table and alternate ways of creating horizon lines with accuracy.  This led me to 2 findings:

1. APCC stores horizon limits in a flat text file with a simple format: 
<azimuth> <altitude>

A pair of space-separated numbers, one pair per line. Azimuth is a whole number from 0 to 359. Altitude is a floating point number, 0 to 90, and represents the lowest altitude that has clear sky at the corresponding azimuth. Obviously, there are 360 lines of this data in the file. The file is saved with the .hrz file extension, but it is otherwise a plain text file that can be edited in any text editor. 

2. Smart phones and tablets are brimming with inclinometers, and there are a few apps for both iOS and Android which can read these and, ultimately, log their values. Since I have an iPhone, I used an app called Theodolite which, if you're familiar with the instrument, puts a crosshair on the middle of your phone's video feed along with angle and rotation information. A similar app on Android is Dioptra.

In these apps, one turns on logging and traces the horizon with the phone as the app logs altitude and azimuth it is pointing at, usually in 1 degree increments. Once you trace a full 360 degrees, you can turn off logging and save the data. In the case of Theodolite on my iPhone, it saved it to my iCloud drive as a CSV file. I then opened it up on my Mac, extracted the Azimuth and Altitude columns, edited them to remove any duplicate azimuth entries or gaps (sometimes if you turn too fast, there is a gap in azimuth numbers). In the end I had 360 lines of accurate horizon altitude limits. I saved the file as a space-separated file with a .hrz extension and loaded it into APCC's horizon limits editor. The result is in the attached screenshot.

This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.



--
Brian 



Brian Valente



--
Brian 



Brian Valente


DFisch
 

Thanks for the attestation, thanks Dale for making my backyard simpler to map, thanks Brian for making me aware. Bad thread skilz are my specialty! Tom

On Mon, Dec 14, 2020 at 13:23 Brian Valente <bvalente@...> wrote:
It's great, but Dale is the guy who came up with this :)



On Mon, Dec 14, 2020 at 9:23 AM Manusfisch via groups.io <tjfischer653=mac.com@groups.io> wrote:
Brilliant Brian, thanks for sharing

TJF Mobile

On Dec 14, 2020, at 11:34, Brian Valente <bvalente@...> wrote:


that is super clever, well done! i will have to try this too



On Mon, Dec 14, 2020 at 8:09 AM Dale Ghent <daleg@...> wrote:

I'm experimenting with defining horizon limits in APCC in conjunction with another project, and I was trying to figure a good way to get an accurate representation of my site's horizon lines into APCC without using the drawing tool. I suck at drawing, especially with a mouse, and the flattened, linear projection of the horizon tool in APCC adds additional challenge in terms of transcribing what you see.

You can also use the alt+az tools in the horizon tracking limits editor to "trace" the horizon using your telescope and camera/eyepiece, manually dropping points to form your horizon, but this seemed a little time consuming to me and I didn't quite want to set up my gear in the daytime to do this when there was also no nights in the forecast that had weather that was conducive to imaging (I've reached the stage of things where if I set up, I'm setting up to image. Damnit. :D )

So this led me to look into how APCC stores its horizon limit table and alternate ways of creating horizon lines with accuracy.  This led me to 2 findings:

1. APCC stores horizon limits in a flat text file with a simple format: 
<azimuth> <altitude>

A pair of space-separated numbers, one pair per line. Azimuth is a whole number from 0 to 359. Altitude is a floating point number, 0 to 90, and represents the lowest altitude that has clear sky at the corresponding azimuth. Obviously, there are 360 lines of this data in the file. The file is saved with the .hrz file extension, but it is otherwise a plain text file that can be edited in any text editor. 

2. Smart phones and tablets are brimming with inclinometers, and there are a few apps for both iOS and Android which can read these and, ultimately, log their values. Since I have an iPhone, I used an app called Theodolite which, if you're familiar with the instrument, puts a crosshair on the middle of your phone's video feed along with angle and rotation information. A similar app on Android is Dioptra.

In these apps, one turns on logging and traces the horizon with the phone as the app logs altitude and azimuth it is pointing at, usually in 1 degree increments. Once you trace a full 360 degrees, you can turn off logging and save the data. In the case of Theodolite on my iPhone, it saved it to my iCloud drive as a CSV file. I then opened it up on my Mac, extracted the Azimuth and Altitude columns, edited them to remove any duplicate azimuth entries or gaps (sometimes if you turn too fast, there is a gap in azimuth numbers). In the end I had 360 lines of accurate horizon altitude limits. I saved the file as a space-separated file with a .hrz extension and loaded it into APCC's horizon limits editor. The result is in the attached screenshot.

This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.



--
Brian 



Brian Valente



--
Brian 



Brian Valente

--
TJF MOBILE


Dale Ghent
 

A side benefit I just realized is that the same az-alt text file that is used for APCC horizon limits can also be used, without modification, to create the basis for a polygonal horizon model in Stellarium, and I believe Cartes du Ciel as well.

Example, using my limits file:
https://i.imgur.com/wemy50M.png

On Dec 14, 2020, at 11:09, Dale Ghent <daleg@elemental.org> wrote:


I'm experimenting with defining horizon limits in APCC in conjunction with another project, and I was trying to figure a good way to get an accurate representation of my site's horizon lines into APCC without using the drawing tool. I suck at drawing, especially with a mouse, and the flattened, linear projection of the horizon tool in APCC adds additional challenge in terms of transcribing what you see.

You can also use the alt+az tools in the horizon tracking limits editor to "trace" the horizon using your telescope and camera/eyepiece, manually dropping points to form your horizon, but this seemed a little time consuming to me and I didn't quite want to set up my gear in the daytime to do this when there was also no nights in the forecast that had weather that was conducive to imaging (I've reached the stage of things where if I set up, I'm setting up to image. Damnit. :D )

So this led me to look into how APCC stores its horizon limit table and alternate ways of creating horizon lines with accuracy. This led me to 2 findings:

1. APCC stores horizon limits in a flat text file with a simple format:
<azimuth> <altitude>

A pair of space-separated numbers, one pair per line. Azimuth is a whole number from 0 to 359. Altitude is a floating point number, 0 to 90, and represents the lowest altitude that has clear sky at the corresponding azimuth. Obviously, there are 360 lines of this data in the file. The file is saved with the .hrz file extension, but it is otherwise a plain text file that can be edited in any text editor.

2. Smart phones and tablets are brimming with inclinometers, and there are a few apps for both iOS and Android which can read these and, ultimately, log their values. Since I have an iPhone, I used an app called Theodolite which, if you're familiar with the instrument, puts a crosshair on the middle of your phone's video feed along with angle and rotation information. A similar app on Android is Dioptra.

In these apps, one turns on logging and traces the horizon with the phone as the app logs altitude and azimuth it is pointing at, usually in 1 degree increments. Once you trace a full 360 degrees, you can turn off logging and save the data. In the case of Theodolite on my iPhone, it saved it to my iCloud drive as a CSV file. I then opened it up on my Mac, extracted the Azimuth and Altitude columns, edited them to remove any duplicate azimuth entries or gaps (sometimes if you turn too fast, there is a gap in azimuth numbers). In the end I had 360 lines of accurate horizon altitude limits. I saved the file as a space-separated file with a .hrz extension and loaded it into APCC's horizon limits editor. The result is in the attached screenshot.

This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.

<MIPUfM1-1.png>


Ron Kramer
 

YEP  Now if only NINA knew it... so it would know when the target is below the custom horizon rather than say 30degrees.
Something I requested... but didn't think it would pan out. However, Stephan did seem somewhat intrigued. 
PRISM does and will sort targets in the sequence by location.  NINA still rules above PRISM AND SGP by leaps and bounds. 

mysky2.JPG
myview.JPG
APCC.JPG


On Mon, Dec 14, 2020 at 2:29 PM Dale Ghent <daleg@...> wrote:

A side benefit I just realized is that the same az-alt text file that is used for APCC horizon limits can also be used, without modification, to create the basis for a polygonal horizon model in Stellarium, and I believe Cartes du Ciel as well.

Example, using my limits file:
https://i.imgur.com/wemy50M.png



> On Dec 14, 2020, at 11:09, Dale Ghent <daleg@...> wrote:
>
>
> I'm experimenting with defining horizon limits in APCC in conjunction with another project, and I was trying to figure a good way to get an accurate representation of my site's horizon lines into APCC without using the drawing tool. I suck at drawing, especially with a mouse, and the flattened, linear projection of the horizon tool in APCC adds additional challenge in terms of transcribing what you see.
>
> You can also use the alt+az tools in the horizon tracking limits editor to "trace" the horizon using your telescope and camera/eyepiece, manually dropping points to form your horizon, but this seemed a little time consuming to me and I didn't quite want to set up my gear in the daytime to do this when there was also no nights in the forecast that had weather that was conducive to imaging (I've reached the stage of things where if I set up, I'm setting up to image. Damnit. :D )
>
> So this led me to look into how APCC stores its horizon limit table and alternate ways of creating horizon lines with accuracy.  This led me to 2 findings:
>
> 1. APCC stores horizon limits in a flat text file with a simple format:
> <azimuth> <altitude>
>
> A pair of space-separated numbers, one pair per line. Azimuth is a whole number from 0 to 359. Altitude is a floating point number, 0 to 90, and represents the lowest altitude that has clear sky at the corresponding azimuth. Obviously, there are 360 lines of this data in the file. The file is saved with the .hrz file extension, but it is otherwise a plain text file that can be edited in any text editor.
>
> 2. Smart phones and tablets are brimming with inclinometers, and there are a few apps for both iOS and Android which can read these and, ultimately, log their values. Since I have an iPhone, I used an app called Theodolite which, if you're familiar with the instrument, puts a crosshair on the middle of your phone's video feed along with angle and rotation information. A similar app on Android is Dioptra.
>
> In these apps, one turns on logging and traces the horizon with the phone as the app logs altitude and azimuth it is pointing at, usually in 1 degree increments. Once you trace a full 360 degrees, you can turn off logging and save the data. In the case of Theodolite on my iPhone, it saved it to my iCloud drive as a CSV file. I then opened it up on my Mac, extracted the Azimuth and Altitude columns, edited them to remove any duplicate azimuth entries or gaps (sometimes if you turn too fast, there is a gap in azimuth numbers). In the end I had 360 lines of accurate horizon altitude limits. I saved the file as a space-separated file with a .hrz extension and loaded it into APCC's horizon limits editor. The result is in the attached screenshot.
>
> This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.
>
> <MIPUfM1-1.png>
>









Ron Kramer
 

A great app called Observer Pro (IOS only I think) has a build in camera/draw creation as you pan.
APP is well worth getting to tell you when targets are in YOUR VIEW not just above horizon!
NINA needs this. 

IMG_1711.PNG


On Mon, Dec 14, 2020 at 4:57 PM Ron Kramer <ronkramer1957@...> wrote:
YEP  Now if only NINA knew it... so it would know when the target is below the custom horizon rather than say 30degrees.
Something I requested... but didn't think it would pan out. However, Stephan did seem somewhat intrigued. 
PRISM does and will sort targets in the sequence by location.  NINA still rules above PRISM AND SGP by leaps and bounds. 

mysky2.JPG
myview.JPG
APCC.JPG


On Mon, Dec 14, 2020 at 2:29 PM Dale Ghent <daleg@...> wrote:

A side benefit I just realized is that the same az-alt text file that is used for APCC horizon limits can also be used, without modification, to create the basis for a polygonal horizon model in Stellarium, and I believe Cartes du Ciel as well.

Example, using my limits file:
https://i.imgur.com/wemy50M.png



> On Dec 14, 2020, at 11:09, Dale Ghent <daleg@...> wrote:
>
>
> I'm experimenting with defining horizon limits in APCC in conjunction with another project, and I was trying to figure a good way to get an accurate representation of my site's horizon lines into APCC without using the drawing tool. I suck at drawing, especially with a mouse, and the flattened, linear projection of the horizon tool in APCC adds additional challenge in terms of transcribing what you see.
>
> You can also use the alt+az tools in the horizon tracking limits editor to "trace" the horizon using your telescope and camera/eyepiece, manually dropping points to form your horizon, but this seemed a little time consuming to me and I didn't quite want to set up my gear in the daytime to do this when there was also no nights in the forecast that had weather that was conducive to imaging (I've reached the stage of things where if I set up, I'm setting up to image. Damnit. :D )
>
> So this led me to look into how APCC stores its horizon limit table and alternate ways of creating horizon lines with accuracy.  This led me to 2 findings:
>
> 1. APCC stores horizon limits in a flat text file with a simple format:
> <azimuth> <altitude>
>
> A pair of space-separated numbers, one pair per line. Azimuth is a whole number from 0 to 359. Altitude is a floating point number, 0 to 90, and represents the lowest altitude that has clear sky at the corresponding azimuth. Obviously, there are 360 lines of this data in the file. The file is saved with the .hrz file extension, but it is otherwise a plain text file that can be edited in any text editor.
>
> 2. Smart phones and tablets are brimming with inclinometers, and there are a few apps for both iOS and Android which can read these and, ultimately, log their values. Since I have an iPhone, I used an app called Theodolite which, if you're familiar with the instrument, puts a crosshair on the middle of your phone's video feed along with angle and rotation information. A similar app on Android is Dioptra.
>
> In these apps, one turns on logging and traces the horizon with the phone as the app logs altitude and azimuth it is pointing at, usually in 1 degree increments. Once you trace a full 360 degrees, you can turn off logging and save the data. In the case of Theodolite on my iPhone, it saved it to my iCloud drive as a CSV file. I then opened it up on my Mac, extracted the Azimuth and Altitude columns, edited them to remove any duplicate azimuth entries or gaps (sometimes if you turn too fast, there is a gap in azimuth numbers). In the end I had 360 lines of accurate horizon altitude limits. I saved the file as a space-separated file with a .hrz extension and loaded it into APCC's horizon limits editor. The result is in the attached screenshot.
>
> This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.
>
> <MIPUfM1-1.png>
>








--



 

Dale just a guess but are you imaging in a cave? :)


On Mon, Dec 14, 2020 at 11:29 AM Dale Ghent <daleg@...> wrote:

A side benefit I just realized is that the same az-alt text file that is used for APCC horizon limits can also be used, without modification, to create the basis for a polygonal horizon model in Stellarium, and I believe Cartes du Ciel as well.

Example, using my limits file:
https://i.imgur.com/wemy50M.png



> On Dec 14, 2020, at 11:09, Dale Ghent <daleg@...> wrote:
>
>
> I'm experimenting with defining horizon limits in APCC in conjunction with another project, and I was trying to figure a good way to get an accurate representation of my site's horizon lines into APCC without using the drawing tool. I suck at drawing, especially with a mouse, and the flattened, linear projection of the horizon tool in APCC adds additional challenge in terms of transcribing what you see.
>
> You can also use the alt+az tools in the horizon tracking limits editor to "trace" the horizon using your telescope and camera/eyepiece, manually dropping points to form your horizon, but this seemed a little time consuming to me and I didn't quite want to set up my gear in the daytime to do this when there was also no nights in the forecast that had weather that was conducive to imaging (I've reached the stage of things where if I set up, I'm setting up to image. Damnit. :D )
>
> So this led me to look into how APCC stores its horizon limit table and alternate ways of creating horizon lines with accuracy.  This led me to 2 findings:
>
> 1. APCC stores horizon limits in a flat text file with a simple format:
> <azimuth> <altitude>
>
> A pair of space-separated numbers, one pair per line. Azimuth is a whole number from 0 to 359. Altitude is a floating point number, 0 to 90, and represents the lowest altitude that has clear sky at the corresponding azimuth. Obviously, there are 360 lines of this data in the file. The file is saved with the .hrz file extension, but it is otherwise a plain text file that can be edited in any text editor.
>
> 2. Smart phones and tablets are brimming with inclinometers, and there are a few apps for both iOS and Android which can read these and, ultimately, log their values. Since I have an iPhone, I used an app called Theodolite which, if you're familiar with the instrument, puts a crosshair on the middle of your phone's video feed along with angle and rotation information. A similar app on Android is Dioptra.
>
> In these apps, one turns on logging and traces the horizon with the phone as the app logs altitude and azimuth it is pointing at, usually in 1 degree increments. Once you trace a full 360 degrees, you can turn off logging and save the data. In the case of Theodolite on my iPhone, it saved it to my iCloud drive as a CSV file. I then opened it up on my Mac, extracted the Azimuth and Altitude columns, edited them to remove any duplicate azimuth entries or gaps (sometimes if you turn too fast, there is a gap in azimuth numbers). In the end I had 360 lines of accurate horizon altitude limits. I saved the file as a space-separated file with a .hrz extension and loaded it into APCC's horizon limits editor. The result is in the attached screenshot.
>
> This took me about 10 minutes to do and required no setup of equipment or drawing with a mouse.
>
> <MIPUfM1-1.png>
>








--
Brian 



Brian Valente


Dale Ghent
 

On Dec 14, 2020, at 17:06, Brian Valente <bvalente@gmail.com> wrote:

Dale just a guess but are you imaging in a cave? :)
SIGH.

It figures to be just my luck that I choose the only house in Maryland that has a redwood tree (a freakin redwood tree! in *Maryland*!) growing along the south side of my lot, and the north side has a giant maple. Despite the ginormous amount of sky redwood takes out, I take solace in the fact that it prevents me from seeing the even more depressing bortle 6000 sky of Washington DC immediately to my south with its thousands of "Washington Globe" acorn-style street lights.

One of these days I'll figure out a remote solution.

/dale


Worsel
 

Thanks, Dale for both the inclinometer technique and the CdC approach!

Bryan


Eric Claeys
 

The SkyX can use the same file.  I did it.

Eric