Grampa Don
Yep, that's me
- Location
- Orange county, Calif.
Professional astronomers collect and study data. The big observatories are pretty much automated. Amateurs look at the sky for pure enjoyment.
Don
Don
Any amateur astronomers?
- Thread starter Grampa Don
- Start date
HiDesertHal
Senior Member
Hey Grampa Don,
Sure, I'll qualify my previous statements!
The human eye, when fully dark-adapted, has an average diameter of 5 mm. Even a small 8" telescope has a mirror diameter of 203.2mm, so the diameter ratio between eye and mirror is 203.2mm / 5mm =40.64.
BUT...this is the ratio of the diameters. The ratio of the areas is 1651.6, (disregarding the blockage of the Secondary mirror), and this is how much brighter the image in an 8" scope will be compared to the naked eye.
The apertures of my large scopes ranged from 12.5" to 20", so this would produce an extreme retina-damaging glare unless a moon filter were used under full-moon conditions.
A 10" mirror would reflect 1.56 times as much light as an 8" mirror, or 2576.5 times the naked eye.
A 12" mirror would reflect 2-1/4 times as much light as an 8" mirror, or 3716.1 times the naked eye.
A 16" mirror would reflect 4 times as much light as an 8" mirror, or 6606.4 times the naked eye.
A 20" mirror would reflect 6-1/4 times as much light as an 8" mirror, or 10,322.5 times the naked eye.
This is why I cautioned against observing the full moon through a telescope, but I should have said a large telescope...my error!
Shown: 6" Computerized Locating and Tracking Refractor.
HiDesertHal
Sure, I'll qualify my previous statements!
The human eye, when fully dark-adapted, has an average diameter of 5 mm. Even a small 8" telescope has a mirror diameter of 203.2mm, so the diameter ratio between eye and mirror is 203.2mm / 5mm =40.64.
BUT...this is the ratio of the diameters. The ratio of the areas is 1651.6, (disregarding the blockage of the Secondary mirror), and this is how much brighter the image in an 8" scope will be compared to the naked eye.
The apertures of my large scopes ranged from 12.5" to 20", so this would produce an extreme retina-damaging glare unless a moon filter were used under full-moon conditions.
A 10" mirror would reflect 1.56 times as much light as an 8" mirror, or 2576.5 times the naked eye.
A 12" mirror would reflect 2-1/4 times as much light as an 8" mirror, or 3716.1 times the naked eye.
A 16" mirror would reflect 4 times as much light as an 8" mirror, or 6606.4 times the naked eye.
A 20" mirror would reflect 6-1/4 times as much light as an 8" mirror, or 10,322.5 times the naked eye.
This is why I cautioned against observing the full moon through a telescope, but I should have said a large telescope...my error!
Shown: 6" Computerized Locating and Tracking Refractor.
HiDesertHal
