I came across an article of Dr. Erhard Hänssgen homemade 107 cm (42") newtonian.
If you scroll down the page a bit you will see him doing full
https://www.cruxis.com/scope/scope1070.htm
That will never happen Bob!bobharmony wrote: ↑Tue Oct 03, 2023 1:10 pm Say it isn't so, Gabby, that you're not coming over to the dark side after all these years as a mirror-basher!
I believe it is for protecting the secondary in transport and assembly.
Let's see if I can follow this, his telescope has diameter D=42*25.4=1067 mm, it's F ratio isOzEclipse wrote: ↑Fri Oct 06, 2023 10:35 am When he was asked to comment about magnification, he replied about using 1600 power. But to use a telescope of that aperture and at his age(he looks 50-60 years old) minimum magnification is around 200X. Any magnification lower than that and he is observing with a smaller aperture.
He also talks about using it for solar observing. With the contraction of his pupil, he'd need to use at least 1000 x magnification to use full aperture. At 200x, his 42 inch scope is only transmitting light from10 inches of aperture. Using it for solar observing seems ridiculous. BTW: The sun is blinding bright in a 10 inch with Baader V5 too, so the extra variable filter will still be needed.
Safer yes, but still going to need bottled oxygen at that altitude.
HI Henk,SkyHiker wrote: ↑Fri Oct 06, 2023 11:36 amLet's see if I can follow this, his telescope has diameter D=42*25.4=1067 mm, it's F ratio isOzEclipse wrote: ↑Fri Oct 06, 2023 10:35 am When he was asked to comment about magnification, he replied about using 1600 power. But to use a telescope of that aperture and at his age(he looks 50-60 years old) minimum magnification is around 200X. Any magnification lower than that and he is observing with a smaller aperture.
He also talks about using it for solar observing. With the contraction of his pupil, he'd need to use at least 1000 x magnification to use full aperture. At 200x, his 42 inch scope is only transmitting light from10 inches of aperture. Using it for solar observing seems ridiculous. BTW: The sun is blinding bright in a 10 inch with Baader V5 too, so the extra variable filter will still be needed.fr =4.5, so the primary's focal length is D*fr =4801 mm. If f is the eyepiece focal length, m is the magnification m=F/ f and x is the exit pupil then x=D/m=D*f/ F=f/fr so for an exit pupil of 5 mm (typical for a 50-year old at night) the matching focal length is f=x*fr =5*4.5=22.5 mm and the minimum magnification to not lose light is m=F/ f=213x. During the daytime the pupil is more like x=3.5 mm so the matching focal length f=x*fr =15.8 mm and the minimum magnification is m=F/ f=305x. That's not crazy, is it, assuming that he uses an extra filter to keep his pupil at a normal size?
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