For eyepieces, Field of view in deg = field stop diameter in mm of eyepiece x 57.3 / telescope focal length in mm.
For cameras, replace field stop diameter with sensor dimensions.
E.g. Field of view in deg = sensor dimension in mm x 57.3 / telescope focal length in mm.
To work in arc min multiply 57.3 x 60 = 3438. You were close with 3460. If you want even more accuracy instead of 57.3 use 180/Pi = 57.2958 but you will find you 1000mm focal length of the telescope will have more variation so 57.3 is sufficient accuracy.
Astronomy tool seems to be a bit inaccurate in FOV
Maybe because they don’t have my telescope in the presets
I’m happy to use my formula and maths
Thanks all
Hi Martin, check that spreadsheet. It's got a bit of everything in it but that's what I've used for a while now to figure out image scale, fov, etc... Check the formulas so you can make your own.
Thanks All
The formula I found on Sky & Telescope 2018 are close to the mark , exactly what I wanted to double check !!
Appreciate the feedback and attached data
Many thanks
Clear skies
As I mentioned on this thread I’ve tried Astronomy Tools FOV calc and I don’t agree with outcome on the image displayed, maybe because they don’t have my telescope listed in the presets ??
M8 Lagoon Nebula is approximately 90 arc minutes x 40 arc minutes in size
My set up according to astro maths is 77 arc minutes x 51 arc minutes in FOV confirmed by a few IIS members on this thread but according to the AT image produced, my set up easily fits around M8 with heaps of room to spare
Somethings not quite right ?
So Im sticking to Astro maths, as I do for everything else in Astronomy both visual and AP
Proof in the pudding will be when I get a chance to image M8 end of May / early June
I will post the image and a brief note on the above posted topic
It is certainly not free but is very good. I have version 3 Pro but I use for visual only. In version 4 the developer split visual and imaging. Imaging has been released but visual is pending. There are different upgrade price options if you buy 3 now than if you bought but a couple of years ago. See Skyhound website for details.
Martin,
Using M8 to gauge your FOV is not accurate.
The most accurate method is to plate solve one of your images....
This will give exactly the field coverage and the plate scale.
I must say, CCDCalc has always given me very good results.
The most accurate method is to plate solve one of your images....
This will give exactly the field coverage and the plate scale.
Precisely what I've always done. My gear rarely changes so I get one image and feed to astrometry to plate solve. Regardless the web specs on your gear the variayions in manufacturing tolerances etc mean in practice they are not that precise in the end. Your image is exactly the fov you get so why not measure just that?