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

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Pages: 1

Allar
journeyman

Reged: 11/22/08

Loc: Jena, Germany

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

#5512817 - 11/10/12 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

Post Extras:

Mike I. Jones
Carpal Tunnel

Reged: 07/02/06

Loc: Fort Worth TX

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

[Re: Allar]
#5512832 - 11/10/12 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

Post Extras:

starman345
Wait, I'm Thinking

Reged: 07/06/10

Loc: New Brunswick, Canada

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

[Re: Mike I. Jones]
#5512839 - 11/10/12 08:42 AM

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

Post Extras:

Mirzam
Post Laureate

Reged: 04/01/08

Loc: Lovettsville, VA

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

[Re: starman345]
#5512892 - 11/10/12 10:01 AM

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

JimC

Post Extras:

glennnnnnn
sage

Reged: 10/20/09

Loc: West Coast High Desert

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

[Re: Mirzam]
#5513071 - 11/10/12 11:45 AM

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

Post Extras:

Víctor Martínez
sage

Reged: 02/05/07

Loc: Cádiz - Spain

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

[Re: glennnnnnn]
#5513255 - 11/10/12 02:20 PM

Great work!

Post Extras:

coinboy1
super member

Reged: 05/03/11

Loc: Oklahoma City, OK

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

[Re: Víctor Martínez]
#5513753 - 11/10/12 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.

Post Extras:

sopticals
sage

Reged: 03/28/10

Loc: New Zealand

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

[Re: coinboy1]
#5513950 - 11/11/12 02:57 AM

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

Stephen,(44deg.S).

Post Extras:

Allar
journeyman

Reged: 11/22/08

Loc: Jena, Germany

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

[Re: coinboy1]
#5513978 - 11/11/12 04:11 AM

Thank you all for your nice comments!

Quote:

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!

Post Extras:

azure1961p
Postmaster

Reged: 01/17/09

Loc: USA

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

[Re: Allar]
#5518753 - 11/13/12 09:44 PM

it took nearly 400 hours to complete this mirror?

pete

Post Extras:

Allar
journeyman

Reged: 11/22/08

Loc: Jena, Germany

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

[Re: azure1961p]
#5518988 - 11/14/12 01:37 AM

Quote:

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.

Post Extras:

Dan Watt
professor emeritus

Reged: 10/13/09

Loc: Oceanside, Calfornia.

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

[Re: Allar]
#5519020 - 11/14/12 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?

Post Extras:

Allar
journeyman

Reged: 11/22/08

Loc: Jena, Germany

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

[Re: Dan Watt]
#5519042 - 11/14/12 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.

Post Extras:

azure1961p
Postmaster

Reged: 01/17/09

Loc: USA

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

[Re: Allar]
#5519115 - 11/14/12 07:02 AM

thanks Allar

Pete

Post Extras:

Project Galileo
professor emeritus

Reged: 11/14/07

Loc: Jefferson County, Colorado

Re: My homemade 488mm (19") F4.85 Dobsonian [Re: azure1961p]
#5519371 - 11/14/12 11:11 AM

Well done!

Post Extras:

scopemankit
sage

Reged: 01/27/09

Loc: south africa

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

[Re: Project Galileo]
#5526189 - 11/18/12 01:51 PM

Thanks Allar, great work!

Post Extras:

herrointment
Carpal Tunnel

Reged: 03/12/11

Loc: North of Hwy. 64

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

[Re: scopemankit]
#5526538 - 11/18/12 06:03 PM

Congratulations!

Your time was well spent!

Post Extras:

mark cowan
Vendor (Veritas Optics)

Reged: 06/03/05

Loc: salem, OR

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

[Re: herrointment]
#5526624 - 11/18/12 06:56 PM

Interesting read.

Best,
Mark

Post Extras:

Rutilus
Pooh-Bah

Reged: 12/17/10

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

[Re: mark cowan]
#5528165 - 11/19/12 03:15 PM

Excellent work.

Post Extras:

Achernar
Postmaster

Reged: 02/25/06

Loc: Mobile, Alabama, USA

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

[Re: Allar]
#5528526 - 11/19/12 06:24 PM

Nice work Allar, very professional job too.

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

Post Extras:

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