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Re: [ATM] 4-1/4" Mirror Suggestions and Thoughts Wanted
And again,
I think the point made earlier that a 10 year old (or a 42 year old ;-) )
will have a much easier time finding and keeping a target in view with the
wide FOV.
Jack
StarryHost.com
-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Jerry
Sent: Tuesday, October 10, 2006 6:15 PM
To: 'Dave Tabor'; atm@atmlist.net
Subject: Re: [ATM] 4-1/4" Mirror Suggestions and Thoughts Wanted
I go more for the low power with this size scope. It is the wide field 15X
to 30X views that I find best on such a scope.
Sure, you see faint fuzzies better with a bigger scope but you see the
planets better too!
But with those big scopes you can't fit some open clusters and extended
objects in the field of view.
With an unobstructed scope such as a refractor you can go to as low a power
as you can find a long focal length eyepiece to do it. But with a diagonal
obstruction at some low power you will see the diagonal shadow in the field
of view.
I find the Pleiades to look best at about 15X.
I think planets will be more disappointing in this size scope than clusters
and Milky Way scanning. I would lean to the low power end.
f:4.5 will give 15X with a 32mm.
f:6 would give 20X
f:8 would give 26X
I would decide by what eyepieces I would have available. I would go as short
as I could and still get to 125X or 150X on the high end with a short
eyepiece or a medium eyepiece and a Barlow I would be happy.
But then longer is easier to make. Taking that into account I will recommend
f:6.
Jerry
-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Dave Tabor
Sent: Tuesday, October 10, 2006 10:53 AM
To: atm@atmlist.net
Subject: [ATM] 4-1/4" Mirror Suggestions and Thoughts Wanted
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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