Re: 114mm Newt, webcam and 2x barlow = magnification ?


"Reddog" <_no_spam_d-hilton@xxxxxxxxxxxxxxxx> wrote in message
news:jl3602llcot44a662570kpbv83ts7ntvap@xxxxxxxxxx
Hi all,

I have just managed to get my first ever webcam avi shots using my
mead DS115 (no comments...), a toucam pro and a 2x barlow, no
eyepiece.

As usual the goto failed and I could not get the tracking to work so I
ended up capturing saturn and mars as they 'floated past'. Oh and did
I mention the wind, so it was really a 'wobble past' The results were
rubbish and my son thought mars was a flying pimple! Duh...

Anyway to the the question : As I did not use a lens (ie webcam on a
threaded adapter and slotted into 2x barlow), how do I calculate the
magnification?


I use a utility in K3CCDtools to calculate this sort of thing for me. Your
scope has a focal length of 910mm, which with a 2x Barlow should end up as
1820mm FL. The Toucam has 640x480 pixels 5.6 microns square. This works out
as 0.63 arcsec/pixel and a field of view of 6.77 x 5.08 arcmin. Tonight
Mars is 7.1 arcsec diameter and should therefore be about 11 pixels across

Robin


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