APPM Models


Worsel
 

Lee

A tip on using MGBox V2 with APPC.

Do not use the astro-mi.ch Windows app.  Just download the ASCOM Local Server.  Use the same COM port in that app and in APPC and APPC will get the data when you connect  in GPS Tab via ASCOM Observing Conditions.

Bryan


 

Hi Lee

afaik pressure doesn't really make much of a difference for model accuracy. Temperature is the real variable there


Brian

On Tue, Dec 1, 2020 at 10:03 AM Lee Dodge <ldodge12@...> wrote:
Worsel,

Thanks for the reply.  I think what was particularly bothering me was the large temperature dependence in the correction equation that I was using to get from barometric pressure to absolute pressure.  I finally gave up and ordered an MGBox V2 to measure the pressure directly.  I hope that this will improve the accuracy of my APPM models.  Previously I was using a THUM device for temperature and humidity, and a fixed value of 737 mbar for pressure, that should correspond to a high pressure, clear day at my altitude.  

When I tried to put together an APPM model, it got about half way through and then froze up for some unknown reason.  I will try again with the MGBox V2 that hopefully will make it more accurate and worth the effort.  Since I am working in a dome, it takes some extra effort to keep swinging the dome around to get a view of the sky.  I did use the search pattern laid out for a dome that helped a bit.    



--
Brian 



Brian Valente


Lee Dodge
 

Worsel,

Thanks for the reply.  I think what was particularly bothering me was the large temperature dependence in the correction equation that I was using to get from barometric pressure to absolute pressure.  I finally gave up and ordered an MGBox V2 to measure the pressure directly.  I hope that this will improve the accuracy of my APPM models.  Previously I was using a THUM device for temperature and humidity, and a fixed value of 737 mbar for pressure, that should correspond to a high pressure, clear day at my altitude.  

When I tried to put together an APPM model, it got about half way through and then froze up for some unknown reason.  I will try again with the MGBox V2 that hopefully will make it more accurate and worth the effort.  Since I am working in a dome, it takes some extra effort to keep swinging the dome around to get a view of the sky.  I did use the search pattern laid out for a dome that helped a bit.    


Worsel
 

Lee

Here is an excerpt from the APPC Pro manual on pressure.  The highlight below is mine.  MGPV2 Box will send local pressure to APPC via the astromi.ch ASCOM driver.

Pressure: Here you can enter the approximate atmospheric pressure. This is used for refraction
calculations. The atmospheric pressure varies based on two principal factors: the weather, and your
altitude above sea level. Note that this differs from typical weather forecast "barometric pressure" which
is the atmospheric pressure normalized to sea level. Do not use barometric pressure values. Light is
being refracted by the actual air mass above your telescope, not the equivalent normalized sea-level air
mass. As an example: mean sea-level atmospheric pressure = average barometric pressure = 1013
mB. The Astro-Physics observatory is at an altitude of about 228 meters above sea level - none too
high. The sea-level value of 1013 mB is equivalent to about 987 mB of actual atmospheric pressure here
at AP. At a remote observatory in Chile at an altitude of 2295 meters, that same sea-level value is
equivalent to about 770 mB.

For any given altitude, the atmospheric pressure will have a certain range of variability that can be
expected. Within the range at your observing spot's altitude, you will find that higher pressure
corresponds with nights where it is clear enough to actually use the telescope, and lower pressure
corresponds with cloudy or even stormy weather. When manually entering a value here, enter one that
corresponds with the high pressure value for your altitude that you would be likely to find on a good clear
night. In a future release, APCC will add support for weather station software so that this value can be
kept updated in real time.


Lee Dodge
 

Thanks for the reply Dale.  Using data from https://www.mide.com/air-pressure-at-altitude-calculator, I come up with a correlation at my altitude of P(mbar) = BARO (inHg) x 3.5599 x (T(C) +273.15)^0.3409.  I am just trying to verify that weather stations that report barometric pressure and temperature are being corrected for altitude and temperature for use in APPM model inputs, and that my approach is reasonable.  


Dale Ghent
 

On Nov 29, 2020, at 12:26, Lee Dodge <ldodge12@gmail.com> wrote:

I am at a loss to understand the details of the pressure required for the APPM model, and how some folks are getting that from the local weather report. The APPM model asks for "pressure" in mbar. My local weather station reports barometric pressure in inches of mercury (Hg). So, for today, the barometric pressure 30.52 in. Hg., and using a conversion factor of 33.8639 mbar/in. Hg, I would get an absolute pressure of 1033.5 mbar, which sounds reasonable for a nice clear day. However, my observatory is at 8565 ft. above sea level, or 2611 m. Using this barometric pressure at my altitude would be nonsense, as I compute the absolute pressure at my altitude and a temperature of -11 C (today's temp.) to be 725.3 mbar. The difference between the barometric pressure and the actual absolute pressure at my location is that the barometric pressure is always converted to some sea level equivalent, and regardless of how high you go, the barometric pressure is always around 1013 mbar. If the model is looking for barometric pressure, then it must be labeled barometric pressure rather than pressure, and if it is really looking for pressure, then how are folks getting that from the local weather report. Which pressure is it looking for?
I think it's pretty obvious and well-understood that the local air pressure is what goes there. How one gets that number is up to their discretion and judgement. For some, the reports given by a weather service are sufficient as those are collected from both official and private weather stations and from local airport weather equipment can be quite accurate enough. Others use local devices. I have a small Arduino-based project the size of a stick of gum that includes a BMP80 air pressure chip and an ASCOM driver that can read it. Yet others have their own weather stations and enter the data either manually or via ASCOM driver, if their weather station has an ASCOM driver that can talk to it. If you find that you need to take a local reading and modify it for your altitude, and it works for you, then it works for you.

mbar is equivalent to the SI unit for air pressure, hectopascals (hPa). The ASCOM ObservingConditions driver specification says that all its various units are SI units, and the astronomy world in general deals in SI units for all measurements. I'm not sure why there needs to be any consternation here.


Lee Dodge
 

I am at a loss to understand the details of the pressure required for the APPM model, and how some folks are getting that from the local weather report.  The APPM model asks for "pressure" in mbar.  My local weather station reports barometric pressure in inches of mercury (Hg).  So, for today, the barometric pressure 30.52 in. Hg., and using a conversion factor of 33.8639 mbar/in. Hg, I would get an absolute pressure of 1033.5 mbar, which sounds reasonable for a nice clear day.  However, my observatory is at 8565 ft. above sea level, or 2611 m.  Using this barometric pressure at my altitude would be nonsense, as I compute the absolute pressure at my altitude and a temperature of -11 C (today's temp.) to be 725.3 mbar.  The difference between the barometric pressure and the actual absolute pressure at my location is that the barometric pressure is always converted to some sea level equivalent, and regardless of how high you go, the barometric pressure is always around 1013 mbar.  If the model is looking for barometric pressure, then it must be labeled barometric pressure rather than pressure, and if it is really looking for pressure, then how are folks getting that from the local weather report.  Which pressure is it looking for?  

Lee


KHursh
 

That is an interesting piece of kit. I would need to think a bit about where I would put it. 

On the other hand, I was successful in getting my run going with SGP as I have a license for that. I had trouble at first with my plate solves because I (stupidly) hadn't done an initial recal in SGP prior to running the model. I stared blankly at the screen of "failed" for two days before it dawned on me.


Ray Gralak
 

Hi Dale,

I had an old license for TSX so I installed it to get APPM access
to a plate solver. After some problems with ActiveX errors being burped up by APPM when trying to solve an image
taken through my ASCOM-connected QHY600, it turned out I needed to run TSX as admin first so that its AcitveX
components could get registered, then APPM was able to talk to it. I expected it to just use TXS's API server but I
guess that isn't the case here.
The reason for using ActiveX is that it allows the same interface code in APPM to be used for CCDSoft V5 and TSX Camera Add-On. :-)

As for why TSX does not register its ActiveX components when SkyX is installed, you will have to ask Software Bisque about that.

-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: Saturday, November 28, 2020 7:46 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] APPM Models


On Nov 28, 2020, at 20:30, KHursh via groups.io <khursh=yahoo.com@groups.io> wrote:

Thanks Marcelo,

I had the API key from years ago, but I set it wrong in APCC. I had to choose ASCOM.OCH.ObservingConditions
as the driver so I could select my PowerBox for temp and humidity, but use OpenWeather for the Pressure.
OpenWeather had bad data for the temperature. It is about 14C here. OWM said it was 26!! Now it is all set!
Teamwork!

For what it's worth, Evan@Pegasus just announced a more comprehensive sensor that plugs into the existing
PowerBox ecosystem:

https://pegasusastro.com/uranus-meteo-sensor/

Available Q1/2021. Pretty much everything you need for local info.

I upgrade to APPC Pro this week and ran my first model tonight using OCH+OWM for air pressure and temperature
and humidity from my UPBv2. It went swimmingly. I had an old license for TSX so I installed it to get APPM access
to a plate solver. After some problems with ActiveX errors being burped up by APPM when trying to solve an image
taken through my ASCOM-connected QHY600, it turned out I needed to run TSX as admin first so that its AcitveX
components could get registered, then APPM was able to talk to it. I expected it to just use TXS's API server but I
guess that isn't the case here.

/dale


Dale Ghent
 

On Nov 28, 2020, at 20:30, KHursh via groups.io <khursh=yahoo.com@groups.io> wrote:

Thanks Marcelo,

I had the API key from years ago, but I set it wrong in APCC. I had to choose ASCOM.OCH.ObservingConditions as the driver so I could select my PowerBox for temp and humidity, but use OpenWeather for the Pressure. OpenWeather had bad data for the temperature. It is about 14C here. OWM said it was 26!! Now it is all set! Teamwork!
For what it's worth, Evan@Pegasus just announced a more comprehensive sensor that plugs into the existing PowerBox ecosystem:

https://pegasusastro.com/uranus-meteo-sensor/

Available Q1/2021. Pretty much everything you need for local info.

I upgrade to APPC Pro this week and ran my first model tonight using OCH+OWM for air pressure and temperature and humidity from my UPBv2. It went swimmingly. I had an old license for TSX so I installed it to get APPM access to a plate solver. After some problems with ActiveX errors being burped up by APPM when trying to solve an image taken through my ASCOM-connected QHY600, it turned out I needed to run TSX as admin first so that its AcitveX components could get registered, then APPM was able to talk to it. I expected it to just use TXS's API server but I guess that isn't the case here.

/dale


KHursh
 

Thanks Marcelo,

I had the API key from years ago, but I set it wrong in APCC. I had to choose ASCOM.OCH.ObservingConditions as the driver so I could select my PowerBox for temp and humidity, but use OpenWeather for the Pressure. OpenWeather had bad data for the temperature. It is about 14C here. OWM said it was 26!! Now it is all set! Teamwork!

Kevin


Marcelo Figueroa
 

Even though I have the Pegasus Powerbox Advance, I haven't installed it yet (waiting for the appropriate cables to arrive) so the details are missing, but look at the image 1 of the link, the pressure is selected in the Obeserving Condition HUB Configuration. Also note that it may take several hours for your OpenWeatherMap account to be activated.
 
At the moment this is what I do:
 
To get all the data via OpenWeatherMap (no device required, but internet connection):
 
1) In APCC Settings > Environmental Settings
2) Source > ASCOMObservingConditions
3) Select Driver > OpenWeatherMap.ObservingConditions
4) Properties :
 
- API Key: Enter the API Key number that was sent to you
- API URL: https://api.openweathermap.org/data/2.5/weather

5) Select Site: Enter your city name and select it from the list (be sure to select the correct city)
- Ok
 
 
 


KHursh
 
Edited

Thanks Marcelo,

I have OpenWeatherMap API key stored in my ASCOM settings, but the pressure still appears editable in APCC pro, so I do. Not sure if I am missing something somewhere.


Marcelo Figueroa
 


You don't need to enter the pressure manually, follow these steps and you can get it (along with temperature and humidity as well) from the internet:

https://ap-gto.groups.io/g/main/message/73588?p=,,,20,0,0,0::Created,,openweathermap,20,2,0,77256891


KHursh
 

PS. I am using a Pegasus Astro Powerbox which has real-time temp and humidity monitoring. I enter the atmospheric pressure manually.


KHursh
 

Thanks for the response Ray!

I am using a fairly well sorted and tied down set-up. I have a 120 mm refractor, so no mirror issues as of now. As for the rest of the randomness, who knows. I am not looking for unguided imaging, I just want REALLY good guiding. The Mach2 and my little 30 point model already improved my guiding to around .6 arc-sec rms. This is higher than many people get on lesser mounts, but a vast improvement to what I was getting. I have pretty bad seeing up here in Northern California.

I don't want to fall into sycophancy, but I really am impressed by APCC/APPM, Ray. It is a large part of why I went with the Mach2 over the 1100GTO. The encoders plus APCC pro were the final decision point for me. Nice work!

Kevin


Ray Gralak
 

Hi Kevin,

I ran my first successful model tonight of 30 points.
Obviously I am going to want to try a much larger model, but I
am wondering how long can I use it. I was thinking about a hundred or so.
If I go for 150 or 200 or so, can I use
that model for multiple days? A week?
If you don't change anything, the model will likely work pretty well indefinitely, but some things will hinder the model's accuracy.

First, to properly account for refraction, you should supply APCC with real-time Temperature, Pressure, and Humidity measurements. The MGBoxV2 is one of the devices capable of supplying this information. You can add this device, or any other ASCOM device with an ASCOM Observing Conditions driver, in APCC's Environmental Settings.

Some potential issues include:

1) Non-repeatable pointing. Some telescopes with non-fixed mirrors can introduce random pointing errors.
2) Any settling of the pier into the ground can change polar alignment.
3) Loose or flimsy mounting plates can introduce randomness.
4) An inadequate focuser can introduce extra flexure and/or introduce randomness.
5) Drastic changes to OTA flexure in temperature changes can subtly affect the pointing model.
6) Hanging cables can introduce randomness, especially if one gets caught on something.
7) Any changes to the setup after a model has been created will usually reduce the model's effectiveness.
8) Any inaccuracy in the plate solves will obviously affect accuracy.

Provided that there is not significant pointing randomness nor unmodeled setup characteristics, each hemisphere model's pointing and tracking rate accuracy will improve as the square root of the number of points. Pointing and tracking rate accuracy should not change significantly over time as long as the setup is stable, which means minimally that the following do not change: polar alignment, flexure, telescope setup, and the total weight of all equipment, counterweights, and balance.

That said, it's pretty easy to create a new model. APPM should be able to capture 2-3 points per minute, or 120-180 points per hour.

-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 KHursh via groups.io
Sent: Friday, November 27, 2020 6:35 PM
To: main@ap-gto.groups.io
Subject: [ap-gto] APPM Models

I ran my first successful model tonight of 30 points. Obviously I am going to want to try a much larger model, but I
am wondering how long can I use it. I was thinking about a hundred or so. If I go for 150 or 200 or so, can I use
that model for multiple days? A week?

Kevin


KHursh
 

Good tip Brian. I will do a 100 or so point model in the mean-time, before I can do the 'whole hog'


 

It sounds like a good idea... but you will get a handful of fails
around the bright moon

if you are going to go through the effort of building a large model to
keep for a while, my experience suggests you want to use a relatively
moonless night

hth

Brian

On Fri, Nov 27, 2020 at 8:08 PM KHursh via groups.io
<khursh=yahoo.com@groups.io> wrote:

I think I will make good use of the full-ish moon to make a much bigger model.


--
Brian



Brian Valente
portfolio brianvalentephotography.com


KHursh
 

I think I will make good use of the full-ish moon to make a much bigger model.