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Re: [ATM] 4-1/4" Mirror Suggestions and Thoughts Wanted

Dave,
   
  That much magnification on a very light 4.5 inch scope is sure to be too stressful to enjoy. Even if you are lucky enough to get a planet into the field, it'll be near impossible to keep it there. It'll move so fast you won't be able to focus your attention on it before you have to  go find it again. I suggest a 6 inch f-6 or f-8 as her first scope. It's easier to make, heavier (which adds stability), and a good compromise on power/light grasp.
   
  A 4.5 inch scope is only useful to give a person aperature feaver.
   
  Ken Hunter

Dave Tabor <david@tabor.com> wrote:
  Hi, fellow, ATM'ers...

I'm a beginning ATM'er, who made his first 8" mirror (f/6.25) last winter. 
I used it to build a travelscope, which works very well, but as I'm told is 
common with ATM'ers, it's my work-in-progress. I recently modified the 
trusses, going from 4 straight to 8 diagonal. Now I need to re-fix the 
balance a little, and I'm planning to switch to ebony star and teflon to 
make it smoother.

I'm going to be assisting my 10 yr old daughter with her first mirror, and 
she's decided that smaller is nicer, so we've purchased a 4-1/4" mirror kit. 
She'd like the scope to be shorter, so it fits her size better. I'd like to 
keep usable for as many different types of things as possible, to help keep 
her interest in astronomy peaked.

If I guide her toward an f/6, it would be shorter (25.5" focal length), but 
would need a 3mm eyepiece to get up to the 212x theoretical maximum 
magnification for a 4.25" mirror.
If she went with an f/12, it would be easier to get the 212x for viewing 
planets, etc., but might limit it's uses.

Being an beginning amateur, and not having the experience to fall back on, 
I'm wondering what suggestions, thoughts or recommendations the group has 
regarding good usable scope configurations using a 4-1/4" mirror?

Thanks,
Dave 

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