Airmass calculation

Image processing, astrometry, photometry, etc.
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VAastro
Posts: 19
Joined: 07 Jan 2019, 18:32

Airmass calculation

Post by VAastro » 15 Jul 2020, 20:01

Is there an Airmass calculation in AA7 or AA6 that can be taken from the ASCOM mounts altitude/azimuth info and be placed in the FITS header?

Thanks
Erik

fabdev
Posts: 202
Joined: 03 Dec 2018, 21:43

Re: Airmass calculation

Post by fabdev » 16 Jul 2020, 15:07

Hello, if you are using scripts, here is an example:

Code: Select all

lon = Observatory.Longitude
lat = Observatory.Latitude
ra,de = Image.EstimateRADec
azi,alt = EquatToAltaz(ra,de,lon,lat,Image.JD)
print "Azi,Alt =" ; azi ; alt
print "Airmass" ; Airmass(alt)
Image.SetKey("AIRMASS", Airmass(alt))

function Airmass(objalt)
  if objalt < 0 then objalt = 0
  thDeg = objalt + 244 / (165 + 47 * objalt^1.1)
  return 1 / Sin(thDeg / 180 * PI)
end function
About the formula, see Wikipedia:
https://en.wikipedia.org/wiki/Air_mass_ ... e_formulas

Actually you don't need to read altitude/azimuth from the telescope, given the ra/dec and the coordinates of the observatory, they can be calculated. An option to add the AIRMASS keyword for every new image will be added in Service Pack 5 this september. If you need the prerelease just let me know.
Greetings, Fabio.

VAastro
Posts: 19
Joined: 07 Jan 2019, 18:32

Re: Airmass calculation

Post by VAastro » 16 Jul 2020, 15:29

Thanks for info Fabio.

Is it possible to get a pre-release SP5?

Erik

merlin66
Posts: 16
Joined: 08 Jan 2019, 05:38

Re: Airmass calculation

Post by merlin66 » 18 Jul 2020, 11:13

Erik,
If you use EQMod the Air Mass is already calculated for you, just click on the LST display and it turns to AirMass

VAastro
Posts: 19
Joined: 07 Jan 2019, 18:32

Re: Airmass calculation

Post by VAastro » 19 Jul 2020, 15:23

Thanks Merlin99

I have an AP Mach1 GOTO mount but I am interested in putting the Airmass into the FITS header so it can be read by my photometry software.

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