RE: [ATM] New with starters questions

["Alan Scott" <alanne1956@hotmail.com>]

Joel,
  One solution among many is the web site that I put together.  It is at 
www.xmission.com/~alanne/DS3Main.html.  This will answer many of your 
questions - as far as I answered them.

  I would recommend buying your first mirror, and I would buy a 12" (0.30 m) 
because the cost isn't much more, 12" scopes can still be made pretty small, 
and they are pretty portable.  As far as costs, I don't know about Europe, 
but check out Gary Hand in the states from "hands on optics".  Maybe he 
could give you a place to buy, or shipping costs.

  By the way, this is an international group.  Centimeters and millimeters 
are fine.

  My side bearings are half circles.  Makes the scope smaller and lighter 
when it is torn down.

  No detailed plans, but I did put into my web site the "hows" and "sizes" 
of everything.  Go to the bottom, and click on links.

  Order IS important.  I made the mirror cell, mirror cage, and secondary.  
Then, you add trusses (as determinded by the focal length of the primary and 
how far the focuser is out from the center of the scope).  Next, figure out 
the center of gravity.  NOW, you can voodoo out the size of the bearings and 
the rocker box.

  Take a look at Mel Bartel's web site.  It is located at: 
http://www.bbastrodesigns.com/.  Mel's old web site at www.efn.org is old.  
Don't use that one.

  Also, go into the atmlist archive and do some back-reading - there are a 
lot of good ideas on this group.  http://www.atmlist.net/

  Two more pieces of advice -
    1) Telescopes are a compromise between being as big as possible, a 
reasonable cost, and as portable and easy to set up as possible.  A good 
size for a first scope is an 8" to 12".  Don't go too big too fast.

    2) Never having made a mirror - here goes some advice.  If you do decide 
to grind a mirror yourself, find someone else local to you that has made one 
to help you learn the ropes the first time.


Alan Scott
www.xmission.com/~alanne/DS3Main.html


>From: "frog3@freeler.nl" <frog3@freeler.nl>
>To: ATM@atmlist.net
>Subject: [ATM] New with starters questions
>Date: Thu, 14 Apr 2005 23:33:31 +0200
>
>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.
>
>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.
>
>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)
>
>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?
>
>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?
>
>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".
>
>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
>
>6:
>What am i forgetting?!..... :) ....very important to ask. :)
>
>Thank you all,
>Joel
>
>
>
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