Help with Firecapture f-ratio?

[yelsac]

Hi 

Just a quick question regarding Firecapture settings.

Every time you record a video you get a text document with the settings used like gain, shutter etc. It also gives the camera used & the focal length. What I want to know is does anyone know if that is correct?

I'm just wondering as I understand firecapture knows the camera, sensor etc but it doesn't know what scope it's being used.

The reason I'm asking is because (& I could have this completely wrong) I'm using an f4.7 scope with a 2.5 Barlow so I assume it would almost be F12, but firecapture tells me it was F9? I also tried a x5 Barlow which again I would have thought would be F24 but firecapture says it was F18!

I'm confused 🥴

Are my maths wrong?

 

[symmetal]

My capture txt files didn't have any details on the scope though I downloaded the latest version and the text files now report 'Unknown Scope'.

Under 'Settings/Misc/Observer' you can set the scope name and aperture but not its focal length. The capture text files still don't mention any focal length or focal ratio though, just the scope name. Are these the same txt files you're referring to?

Alan

 

Edited January 7, 2023 by symmetal

[yelsac]

Hi Alan

Thanks for your reply

Below is one of my text files that firecapture creates when I record a video.

2022-12-27-0027_6-U-IR-Mars.txt

As you said it says unknown scope but a few rows down it says under focal lenght =1900mm (F8) which by my maths should be F12 🤷‍♂️

[symmetal]

Yes, your file has extra entries compared to ones I checked. Maybe you had the option to keep the planet centred while capturing checked. I assume this requires FC to measure how many pixels width the planet occupies and from this the image scale. If it knew the current angular size of the planet, it could work out the focal length. Maybe it takes an average angular size over a complete orbit to use which would throw the calculations off somewhat.

Alan