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My homemade 488mm (19") F4.85 Dobsonian

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#1 Allar

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Posted 10 November 2012 - 08:15 AM

Hi guys,

I'm an amateur telescope maker from Finland (currently studying in Germany). Recently I have finished my latest half a metre Dobsonian and I was thinking of shearing the story with you. Actually I finished the telescope already a year ago but I finally had some time to translate my home page from Finnish to English.

488mm F4.85 Dobsonian Telescope

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#2 Mike I. Jones

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Posted 10 November 2012 - 08:30 AM

Allar, by any level of standard or comparison here, you have a first-rate, top-shelf, beautifully executed telescope. Congratulations on finishing it and enjoying it, and thanks for sharing it here! Can't wait to see your next project.
Mike

#3 starman345

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Posted 10 November 2012 - 08:42 AM

Allar, absolutely beautiful telescope. Making that mirror had to be a big challenge. Congrats on the stunning results. Thanks for sharing.

#4 Mirzam

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Posted 10 November 2012 - 10:01 AM

Beautiful scope and very nicely illustrated and explained in your blog.

JimC

#5 glennnnnnn

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Posted 10 November 2012 - 11:45 AM

Wow! Obviously you know what you're doing, especially using small grinding tools like that. Great telescope!

#6 Víctor Martínez

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Posted 10 November 2012 - 02:20 PM

Great work!

#7 coinboy1

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Posted 10 November 2012 - 10:16 PM

Allar. Congratulations on the scope build it looks great! You look fairly young so I am glad im not the only mirror grinder in their 20s.

#8 sopticals

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Posted 11 November 2012 - 02:57 AM

Thanks Allar, nice one, appreciate your account of the journey from beginning to end.

Stephen,(44deg.S).

#9 Allar

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Posted 11 November 2012 - 04:11 AM

Thank you all for your nice comments!

You look fairly young so I am glad im not the only mirror grinder in their 20s.


Yes, indeed! I was only 20 when I started the project freshly after completing my high school.

I would like to point out here that many people are afraid to make big mirrors. I believe that people grinding 25-30cm size mirrors are very well capable to make half a metre mirros if they just have enough motivation and patience for it.

This mirror was only fourth I have finished after completing 150mm, 300mm and 75mm mirrors. The step from 300mm to 488mm was big but in the end I think this half a metre mirror was not significantly more difficult to grind as my 30cm mirror. It just took some more time.

So for grinders thinking whether they should or should not start grinding a large mirror I would just say GO FOR IT! ;)

#10 azure1961p

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Posted 13 November 2012 - 09:44 PM

it took nearly 400 hours to complete this mirror?

pete

#11 Allar

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Posted 14 November 2012 - 01:37 AM

it took nearly 400 hours to complete this mirror?

Yes, around 370 hours including time for tool making etc. For comparison it took me 300 hours to make the 300mm (12") mirror. The difference is not that big because I got lot of experience while doing the 300mm mirror.

#12 Dan Watt

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Posted 14 November 2012 - 02:38 AM

Thank you for this post! What a great read. I'm impressed with how well you document everything.

How well do you like the CF spider vanes?

#13 Allar

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Posted 14 November 2012 - 03:36 AM

The carbon fibre vanes have worked very well and I was able to reduce some weight. The spider without the secondary mirror weights around 500g. Carbon is also matte black and no painting was needed. The only negative thing I can found is that the vanes I used are relatively thick (1 mm). A bit thinner vanes would work fine I suppose.

#14 azure1961p

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Posted 14 November 2012 - 07:02 AM

thanks Allar

Pete

#15 Project Galileo

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Posted 14 November 2012 - 11:11 AM

Well done!

#16 scopemankit

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Posted 18 November 2012 - 01:51 PM

Thanks Allar, great work!

#17 herrointment

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Posted 18 November 2012 - 06:03 PM

Congratulations!

Your time was well spent!

#18 mark cowan

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Posted 18 November 2012 - 06:56 PM

Interesting read. :waytogo:

Best,
Mark

#19 Rutilus

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Posted 19 November 2012 - 03:15 PM

Excellent work.

#20 Achernar

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Posted 19 November 2012 - 06:24 PM

Nice work Allar, very professional job too. :bow: I am sure the workmanship is matched by the views through your telescope. I built my own 15-inch (380mm) Obsession patterned Dob, but I paid to have the optics made as I do not have the means to grind, polish and figure them. I did however weld the primary mirror's tailgate, spider and other componnents out of mild steel. The rest of the metal components I cut out of 6061 T6 aluminum alloy and 316 stainless steel. I even sewed my own shroud for it, but I am no dressmaker, LOL. I am very impressed with your workmanship, you are a very good craftsman, far better than me.

Taras






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