ATM (amateur telescope making)

[bronx]

Hi all,

I would like to share my biggest project ever with you all.

some 4 years ago I completed building my own telescope. Including handgrinding and handpolishing my own primary mirror.

I must say to you - after so many hours of work it it a wonderfull feeling seeing through the scope the first time and then it is there... The first sharp look  ;D Haven't beaten that feeling since.

Anyway - have a look at the pictures in my gallery, many of them speak for themselves.
http://festoolownersgroup.com/CoppermineMain//thumbnails.php?album=82

And by the way - I used my ES 150 and my OF 1010EBQ to the wood part of the project. Since then I became a "festoolholic"

Questions? Feel free to ask! 

Best regards Thomas, Denmark

 

[jatt]

Dare I ask how many hours you had to spend handpolishing the mirror.

What sort of magnification is your telescope capable of?

Worked with a "boy genius" in my previous job who was building something similar.  Saw a book he had on the maths on optical theory and calculating curvature of lenses etc..etc..  Bit over my head, but interesting just the same.

Looks good.  Sure u will have fun playing around with it.

 

[CharlesWilson]

I just started grinding the mirror for my second telescope. The first one was done years before I even heard of Festool. I think I finished it back in 2000. The purpose of this second one is to create a more easily transportable telescope, mostly for planetary viewing. The mirror for this one is 6", similar in size to the one you show in the picture. The previous one was 8". When finished, I plan to post the woodworking portion of the project here.

Charles

 

[Dave Ronyak]

I know next-to-nothing about telescopes and optics in general, so please forgive my [probably stupid] questions.  Wood is responsive to changes in humidity.  Coatings slow down the rate of moisture absorption and desorption, but cannot stop it.  Doesn't use of wood in the structure of the telescope render the alignment of the lenses and mirrors unstable?  How do you deal with that issue?  Or is the rate of any change in alignment so slow as to not affect any night of use once adjusted?

Dave R.

 

[CharlesWilson]

I know next-to-nothing about telescopes and optics in general, so please forgive my [probably stupid] questions.   Wood is responsive to changes in humidity.  Coatings slow down the rate of moisture absorption and desorption, but cannot stop it.  Doesn't use of wood in the structure of the telescope render the alignment of the lenses and mirrors unstable?  How do you deal with that issue?  Or is the rate of any change in alignment so slow as to not affect any night of use once adjusted?

Dave R.

Dave,

Wood is very responsive to changes in humidity. So are the fiber tubes often used to make homemade telescopes. Water resistant coatings are normally applied to these materials. Metal and glass are responsive to changes in temperature. All of this needs to be factored into the adjustment (collimation, etc) of telescopes.

It is a good idea to operate a telescope after it has reached equilibrium with its environment. Until the mirror is at a constant temperature throughout its thickness, its reflective surface will be 'moving' and affecting image quality! When at equilibrium, you can make the necessary adjustments, and, for a period of time, the telescope will be working in an optimal fashion. When there is both radiation cooling and relatively high humidity, condensation can become a significant problem. Small resistive heaters are often used to eliminate this problem on glass and metal surfaces. Condensation on the cooled surfaces of the structure can result in a significant amount of moisture appearing on the telescope.

The best designs for simple reflector telescopes (often called Dobsonian) will incorporate mechanisms for making the necessary adjustments while looking through the eyepiece. Because some telescopes have the big mirror 5 or more feet distant from the eyepiece, this can provide some unique design challenges, but it is very much worth the effort if you want to see spectacular views of the moon and planets.

 

[bronx]

Dare I ask how many hours you had to spend handpolishing the mirror.

What sort of magnification is your telescope capable of?

The polishing took me around 50 hours - but who counts when you have fun ;D

The magnification depends on how many millimeter focal lenght the first lens you look through has. Magnification will range from around 25 times up to around 250 times magnification.

Charles and Dave - I guess all is answered regarding humidity etc. Thanks!

 

[Matthew Schenker]

Good Afternoon,
This is really interesting.  For many years, I've been a backyard astronomer.  I've owned numerous telescopes, include Dobsonians (my favorites).  I've often been curious about the people who build their own Dobsonian bases using wood and a variety of other materials.  I have this dream of building a base that allows for the perfect adjustments and easy transport.

Here are a few sites from some people I've been watching who are into DIY Dobsonians (a number of them are amazingly ambitious):
http://www.scribd.com/doc/3475460/how-to-build-a-dobsonian-telescope
http://www.astropix.com/HTML/L_STORY/DOB.HTM
http://www.scopemaking.net/dobson/dobson.htm
http://www.webjones.net/telescope_v1.htm
http://ladyandtramp.com/tj/
http://www.gm4jjj.co.uk/astronomy/dobson.html

I'd be really curious to hear from other FOG members who are interested in amateur (or professional) astronomy, and whether they have seen ways to combine woodworking and stargazing.

Stay in touch,
Matthew