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Re: [ATM] New with starters questions
I'll see if I can answer your questions.
--- "frog3@freeler.nl" <frog3@freeler.nl> wrote:
> Hello all,
> i'm Joel, from the Netherlands, i'm new to the
> group.
>
> i would like to ask a few things to help me on the
> way to building a
> first 20, 25 or 30 cm truss dobson telescope. (8",
> 10" or 12")
>
> probably a 10" as this seems to be the best
> compromise for me at this
> time, regarding cost and final size, i would like to
> make it about F/5,
> so around 1250mm in the case of the 25cm.
Costwise is one thing to consider when building a
'scope. The other thing is size. If you live in a
small place, you're not going to want to build a large
telescope, because these nice instruments take up as
much space as a refrigerator in some cases.
>
> first general question:
> is it alright if i talk in centimeters and
> milimeters here? as it is
> easyer for me to think about than to think in the
> feet and inch conversions.
I like cm, but I think in inches.
>
> first atm question:
> if i want a 25 cm dobson tlescope, should i make the
> mirrorbox about 30
> cm? or is this too small or too big? (roughly 2"
> more than the size of
> the mirror)
>
The mirror box size shouldn't be too big. You wnat to
get the light out of it somehow. 30cm for a 25cm
mirror sounds ok, but you might consider smaller, say,
27cm so you don't have as much diagonal mirror
obstruction.
> 2:
> What is better costwise: making a mirror out of a
> blank and having it
> aluminized and coated or buying the most inexpensive
> ready-made usable
> 10" f/5 mirror?
> and what will both of these options more or less
> exactly cost?
> and where should i buy it? here in the netherlands?
> or in europe? or
> doesn't it matter? what would be the best for the
> price including all
> shipment(s) and where should i 'shop'? and do any of
> the people of this
> list also sell atm supllies?
>
Make your mirror. Costwise it may be similar to a
purchased set of optics, but you have complete control
over how good the final product really is.
> 3:
> I would like to make the , what i believe are called
> sidebearings, in
> sort of a half circle, instead of a circle, is this
> a lot more difficult
> to do than just a making a plain circle, or does it
> make no difference?
>
The circular side (altitude) bearings should be
circular because the half of the circle you're not
using supports the part you use. Pipe fittings also
don't come in hemicircular parts.
> 4:
> does anyone have any drawings or plans (or how
> should i be calling this
> in particular? please help the novice) with exact
> sizes for everything?
> just to function as an example for me to 'draw on',
> because it's quite
> difficult to be doing this from scratch, or even a
> boook, that is what i
> find at least, i have the Kriege book of "The
> Dobsonian telescope".
I don't have drawings or plans, but I do have photos
of my equatorial mount in progress.
>
> 5: (very important, so i'm not sure why it ended on
> place 5 ;)
> what to make first? and when does the balancing of
> the telescope have to
> be done? which part is it that neds to be
> re-adjusted for the balancing,
> and therefore
Make the mirror first, but you can make it all at once
if you can keep your mind that focused.
>
> 6:
> What am i forgetting?!..... :) ....very important to
> ask. :)
Um... I have to remind myself not to forget. I'll
get back to you when I remember this part.
>
> Thank you all,
> Joel
Kevin of Eastern Iowa
Seeker of the Darkness
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