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Old 10-04-2007, 07:50 PM
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Smile 24" Nasmyth

Well it's been a very busy couple of weeks for me. I started my 24" project after spending so much time on the design side of things I was egar to start doing some hands on work.

Because I needed the secondary holder to star test the optics on another telescope that George had. (by the way for those who don't know, Big George he is known to some of us on the forum and although he can be quite strange at times he has a passion for working with class especially telescope mirrors he is doing the optics) I started work on the secondary holder and as you will see by the pics this whole project will be very time consuming but I love every moment of it!

With the holder finished I moved on to the spider and then the top ring which is stained with a mix of Walnut and Golden Oak and then thinned. I yet have to spray several coats of polyurethane.

Anyway a picture says a thousand words so here they are.
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Last edited by Orion; 10-04-2007 at 08:07 PM.
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Old 10-04-2007, 07:58 PM
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Old 10-04-2007, 08:06 PM
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Old 10-04-2007, 08:14 PM
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Astroman (Andrew Wall)
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Ed you are a master scope builder That looks really nice, no wonder your happy with it 24" hey WOW.. how much does a mirror like that set you back these days?
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Old 10-04-2007, 08:21 PM
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h0ughy (David)
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wow that potato masher is really developing since I saw it at the last NAS meeting. Excellent work Ed!
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Old 10-04-2007, 08:26 PM
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seeker372011 (Narayan)
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work of art -a thing of beauty surely is being created here
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Old 10-04-2007, 08:27 PM
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Quote:
Originally Posted by Astroman View Post
Ed you are a master scope builder That looks really nice, no wonder your happy with it 24" hey WOW.. how much does a mirror like that set you back these days?
Thanks Andrew, well the cost of the mirror....it depends on how much work it takes him to figure it. He says that some times they get stubborn towards the end.
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Old 10-04-2007, 08:30 PM
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So is this a Cassegrain or similar type of scope? Just looking at the secondary holder its not on a 45 degree angle?
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Old 10-04-2007, 08:39 PM
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Quote:
Originally Posted by Astroman View Post
So is this a Cassegrain or similar type of scope? Just looking at the secondary holder its not on a 45 degree angle?
It's a Cassegrain secondary with a tertiary at 45 deg.
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Old 10-04-2007, 08:42 PM
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hence the reason for the oversized secondary. I like this design, reasonably impractical for smaller scopes but perfect for large ones. cant wait to see how it turns out for you.
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Old 10-04-2007, 09:54 PM
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Hi Ed,

Awsome A couple of Q's:

What is the secondary size, it looks about 10".
Is it a Cassegrain secondary (convex) or is it a flat?
I assume the round bit of plate is a baffle, is it tapered to allow for the light cone from the primary or have you just made the top end a little oversize?
BTW what is the F ratio of the primary?

Cheers,
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Old 11-04-2007, 03:31 AM
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Quote:
Originally Posted by stringscope View Post
Hi Ed,

Awsome A couple of Q's:

What is the secondary size, it looks about 10".
Is it a Cassegrain secondary (convex) or is it a flat?
I assume the round bit of plate is a baffle, is it tapered to allow for the light cone from the primary or have you just made the top end a little oversize?
BTW what is the F ratio of the primary?

Cheers,
Hi Ian,
The secondary is a n 7.5" convex mirror. The "can" around the mirror is the baffle and the primary is a f5.
The pic might explain it better.
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Old 12-04-2007, 04:38 PM
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Hi Ed,

What a fantastic looking project you have there. Just wondering what the final focal ratio might be? I saw that the primary is f5 but was curious about the amplification factor of the secondary.

Do you intend to mount it as a Dobsonian or Equatorially?

If the final instrument is up to the standard of what you have done so far it will be one classey looking instrument!

Regards
Andrew
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Old 18-04-2007, 07:19 PM
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Hi Andrew, sorry for the late reply.

The focal ratio with the secondary will be close to f7 and it will be a Alt Az mount.
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Old 20-04-2007, 06:34 PM
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I did a bit more work on the secondary holder. The top ring, spider and holder is all assembled. See what you think.
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Old 20-04-2007, 06:44 PM
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beautiful work Ed. It reflects the time and effort you have put into it
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Old 21-04-2007, 09:37 AM
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beautiful work Ed. It reflects the time and effort you have put into it
Thanks mate...
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Old 21-04-2007, 10:19 AM
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Looks fantastic Ed.
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Old 21-04-2007, 11:59 AM
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Brilliant work!

This is such an exciting project - it'e double the focal lenghth of Zane's http://www.sdmtelescopes.com.au/SDM007.html and with a 4000+ mm focal length is going to be the ultimate high power scope!

It would be great to get them side by side when they are finished and do a compare and contrast - they are at opposite poles of the monster dob scale! Chuck in a standard 25" F5 as the control by which they are measured.

BTW, If the eyepiece height is low enough to avoid a ladder you may be able to angle the focuser like smaller dobs to make it more comfortable at lower declinations.
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Old 21-04-2007, 04:12 PM
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rmcpb (Rob)
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Looked thorugh George's scope at the SPSS which is the same design and also throught the 25" Obsession. Liked the idea of not climbing ladders in the night
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