RFI telescope

[brian fleming <>]

 wrote:

> Any ideas about the utility of a Nationbal Geogrphic 50mm telescope, 
> 18-180x ?
> Thanks,
> Judith. 
A 10:1 zoom ratio seems excessive - I suspect some compromises somewhere 
in the mechanism and optics. 50mm objective at 180x is going to be very 
dark We made sure to get ~80mm for our 20-60x scope. Unlike a good 
camera zoom lens, you have to refocus after each zoom - not a question 
of maker, as this applies to Zeiss and other top brands.
Brian Fleming
Melbourne
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