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where to buy a finished 12 inch mirror kit to begin building my own Dob?

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#1 firmdog

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Posted 14 October 2019 - 02:02 PM

Hi,

 

All of my searches result in vendors selling blanks only. Does anyone have a list of vendors where one can buy a fully finished and polished, etc... 12 inch mirror kit to begin building my own Dobsonian? I really don't have the time to do the polishing of a mirror blank so I would rather buy a mirror kit, but having trouble finding places to purchase from. 

 

I would appreciate if anyone can tell me where I can buy a ready to go 12 inch mirror kit for an attempt at a DIY Dob?

 

Thanks!



#2 sg6

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Posted 14 October 2019 - 02:31 PM

I assume you want a finished mirror, not a "kit".

Hubble Optics, Orion Optics UK, many retailers will sell mirrors usually GSO ones.

 

Where are you in this case a location is somewhat relevant.

 

Also budget - are you looking at GSO or Zambuto ?


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#3 kksmith

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Posted 14 October 2019 - 02:49 PM

https://agenaastro.c...set-12-f-5.html



#4 firmdog

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Posted 14 October 2019 - 07:42 PM

I assume you want a finished mirror, not a "kit".

Hubble Optics, Orion Optics UK, many retailers will sell mirrors usually GSO ones.

 

Where are you in this case a location is somewhat relevant.

 

Also budget - are you looking at GSO or Zambuto ?

 

Yes, you are correct. I am looking for finished mirrors so I can focus on building the scope.

 

I am near Annapolis, Maryland.  (Bortle 7/8 area I believe)

 

GSO or Zambuto is above my level of knowledge. A quick web search says Zambuto has better contrast and is more expensive?

 

I have an Orion XT8 right now and am looking to build a 12 inch. I am a novice, but I finally found the Andromeda galaxy a few weeks ago, that was really exciting, so now I am really hooked and want to go a bit bigger, and then get into astrophotography. From all my research, a 12 inch Dob will be the largest I will need for a long, long time. Looking to build it myself and it seems hard to find vendors for finished mirrors. Any recommendations welcome!

 

I see kksmith gave me a good link, so will look at that for now and see if any other recommendations come back in this forum thread.

 

Thanks!



#5 Stephen Kennedy

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Posted 14 October 2019 - 08:36 PM

You will not be able to do astrophotography with a Dobsonian.  Alt-az mounts, even with motor drive will suffer from field rotation limiting exposure time to a few seconds.  Astrophotography requires a German Equatorial Mount (GEM) that is motor driven and such a mount is not really something that an amateur can build.  A GEM capable of accomodating a 12" reflector will be very large, heavy and expensive..


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#6 kfiscus

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Posted 14 October 2019 - 09:40 PM

12" is the perfect size for a dob- I have 2 that size.  You CAN do astrophotography without field rotation if you use a quality 2-axis equatorial platform but it is not ideal.  Google Tom O's website to see amazing deep-sky photos taken with large dobs on his platforms.

Attached Thumbnails

  • Stock 12 & 16 Photos 005.JPG

Edited by kfiscus, 14 October 2019 - 11:18 PM.

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#7 drneilmb

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Posted 14 October 2019 - 09:45 PM

GSO or Zambuto is above my level of knowledge. A quick web search says Zambuto has better contrast and is more expensive?

 

I have an Orion XT8 right now and am looking to build a 12 inch. I am a novice, but I finally found the Andromeda galaxy a few weeks ago, that was really exciting, so now I am really hooked and want to go a bit bigger, and then get into astrophotography. From all my research, a 12 inch Dob will be the largest I will need for a long, long time. Looking to build it myself and it seems hard to find vendors for finished mirrors. Any recommendations welcome!

Completed telescope mirrors are available in a very wide range of price and quality. The Chinese optical manufacturing company GSO (Guan Sheng Optical) makes mirrors for many of the commercially available dobsonians. This one https://agenaastro.c...-f-5-ad017.html is probably the same thing that goes into an Orion XT12. Other online sellers might exist for the same mirror. These mirrors are passable, generally "diffraction limited" but they are mass-produced items and they do occasionally make a lemon. Testing to find out if the one you bought is a lemon is not completely trivial.

 

In the next price point, there are mirrors hand made by skilled opticians. Zambuto is one example, but the price increase is substantial https://zambutomirro...om/mirrors.html. There is not as much middle ground between these two price ranges as you might imagine (because hand-making mirrors is extremely time-consuming and requires substantial expertise).

 

Perhaps the best way to get a 12" mirror is to post a "Wanted" ad here on the Cloudy Nights classifieds, or monitor the classifieds closely to see when one comes up for sale. I bought my 12" f/5 Orion mirror for around $250 here on Cloudy Nights.

 

-Neil


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#8 Jon Isaacs

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Posted 14 October 2019 - 10:37 PM

12" is the perfect size for a dob- I have 2 that size.  You CAN do astrophotography without field rotation if you use a quality 2-axis equatorial platform but it is not ideal.  Google Tom O's website to see amaing deep-sky photos taken with large dobs on his platforms.

Here you go.. 12.5 inch F/4.06 on a dual axis Tom O. Eq platform:

 

JStar on EQ Platform 1.jpg

 

Jon


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#9 stargazer193857

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Posted 17 October 2019 - 10:04 PM

A mount need not be able to rotate a tube 360 degrees to take a good picture. If it could go 5 degrees before needing a reset, that would be good enough. I wonder if powered roller rings would be worth designing.
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#10 stargazer193857

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Posted 18 October 2019 - 11:28 AM

Dobson allowed visual observers to use bigger scopes by coming off the eq to use the alt AZ dob mount. But astrophotographers still use EQ mounts. What if powered tube rings, even if reset every 5 degrees, allowed astrophotographers to come down off their eq mounts?

Would 20" astrographs be good?
The alt axis just needs a sign wave generator, like a piston rod or steam tie rod. Mirror makes use them to make back and forth motion for polishing. The ax axis can be fixed speed. And the tube axis can be fixed speed too.
No computer is needed to track.

#11 stargazer193857

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Posted 18 October 2019 - 11:30 AM

I've seen 18" truss dobs with a strange almost 3 axis set up. I think it is for navigating Dobson's hole, but I bet it could be geared to rotate with a long exposure for 5 degrees.

...

This whole time I thought I was replying to the 14" thread, for the guy who wanted astrophotography. Time to copy and paste.

Edited by stargazer193857, 18 October 2019 - 11:32 AM.



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