Planetary Newtonian anyone

[neil phillips]

Couldnt believe my eyes when i saw this. Wonder what kind of mount could take this ?   12" F10  Newtonian nearly 10 feet long.

One would hope the figure is good. And what about Flexure. Would this even work ? And has anyone ever purchased one. One wonders.

Nuts

Parabolic Primary Mirror, D300F3000 High precision Scientific Research Astronomical Reflecting Telescope Collimator|Lenses| - AliExpress

Edited December 8, 2021 by neil phillips

[Alien 13]

I would drill a hole in it to make the scope 5 ft long for a start 🙂

Alan

[rl]

I believe there is a precedent; Clyde Tombaugh is supposed to have used a 12" f/10. It may well be similar to the scope in the wikipedia article photo which looks like it might be f/10: all the photos I can find of the scopes he made show incredibly long tubes.

https://en.wikipedia.org/wiki/Clyde_Tombaugh

 

Edited December 8, 2021 by rl

[neil phillips]

39 minutes ago, rl said:

I believe there is a precedent; Clyde Tombaugh is supposed to have used a 12" f/10. It may well be similar to the scope in the wikipedia article photo which looks like it might be f/10: all the photos I can find of the scopes he made show incredibly long tubes.

https://en.wikipedia.org/wiki/Clyde_Tombaugh

 

wow interesting thanks for that information and link

[neil phillips]

1 hour ago, Alien 13 said:

I would drill a hole in it to make the scope 5 ft long for a start 🙂

Alan

Thats the sprit of adventure 👌 Some might find it interesting. Maybe the short scopes need stretching lol 😄

Edited December 8, 2021 by neil phillips

[johninderby]

Does it come with a free step ladder? 😁

[neil phillips]

12 minutes ago, johninderby said:

Does it come with a free step ladder? 😁

  Thats also on Ali. Probably there mate down the road 😆 What Amazes me. is the coatings are about as standard as you can get. Yet everything else is about as unstandard as is possible 

Edited December 9, 2021 by neil phillips

[johninderby]

I was looking at their other mirrors and they seem to be of SW or GSO standard so not bad but not premium either. 😋🤔

 

[neil phillips]

1 minute ago, johninderby said:

I was looking at their other mirrors and they seem to be of SW or GSO standard so not bad but not premium either. 😋🤔

 

Your paying all that money for the long focal length yet its easier to make. Dont quite get that ? wonder what Orion would charge ? 

[johninderby]

Sure they could do it to special order and as their 300mm f5.3 primary and secondary 1/10 PV set are cheaper so perhaps a similar price but premium optics. 

[neil phillips]

5 minutes ago, johninderby said:

Sure they could do it to special order and as their 300mm f5.3 primary and secondary 1/10 PV set are cheaper so perhaps a similar price but premium optics. 

Yeah probably John. I Am fairly certain mirror makers have a easier time. Compared to Short focal length. So dont understand the extra cost. Was just looking at a 8" long focus achro doublet its really something. F14.3 3000mm long 

Astronomical Telescope Refraction Objective Lens Double Separation Achromatic Large Size D210mm F3000/2400/1800/1200mm|Lenses| - AliExpress

[johninderby]

Think Rowan would need to come up with an AZ500 for that one.. 😁

Edited December 9, 2021 by johninderby

[neil phillips]

3 minutes ago, johninderby said:

Think Rowan would need to come up with an AZ500 for that one.. 😁

Good aint it. EQ8 Maybe ? 

[johninderby]

Maybe if perfectly balanced.

How about this offering from Tecnosky? 🤔

https://astrograph.net/epages/www_astrograph_net.sf/en_GB/?ObjectPath=/Shops/www_astrograph_net/Products/AGTEC234

Edited December 9, 2021 by johninderby

[neil phillips]

1 hour ago, johninderby said:

Maybe if perfectly balanced.

How about this offering from Tecnosky? 🤔

https://astrograph.net/epages/www_astrograph_net.sf/en_GB/?ObjectPath=/Shops/www_astrograph_net/Products/AGTEC234

That is a beast. And bigger than that lens i showed you. But five times  the price. The chinese 210mm At F14 would  be colour free. wonder what the cell and tube would cost to get it built ? reckon half the price. At F14 like a  backstreet scopetech on steroids. You would worry about the figure though for a £2000 scope unmounted wouldnt you. I aint building it intriguing though sure you agree. Would need a obs around it. Sod trying to lift it on your own. Not possible probably 

Edited December 9, 2021 by neil phillips

[neil phillips]

Heres another 9 inch f12

High Quality Astronomical Telescope Objective Lens D222F2700 Double Separation Single Film Multilayer Film|Lenses| - AliExpres

10" F7.1 Crazy

Refraction Astronomical Telescope Objective Lens D254f1375/F1800|Lenses| - AliExpress

Edited December 9, 2021 by neil phillips

[johninderby]

And I’ll raise you this. 😁😁😁

https://www.widescreen-centre.co.uk/LZOS-304-3600-T.html

[neil phillips]

3 hours ago, johninderby said:

And I’ll raise you this. 😁😁😁

https://www.widescreen-centre.co.uk/LZOS-304-3600-T.html

Would be nice to do some lunar imaging with it for a few days. Somewhere high like Hawaii.  But i must complain a bit. The scope will probably be quite a bit better than the far east offerings. But for a better figure better glass and two inches more  its only about £136.000 dearer. Even though i wouldnt build these chinese achros. They are actually doable for about 6 grand mounted i reckon. Wonder if anyone has tried. Have they actually sold 1 ? 

Edited December 9, 2021 by neil phillips

[johninderby]

If I win the lottery will let you know how well it performs from my villa in Tennerife. 😁😁😁

Dream on. 😕😢😢😢

[neil phillips]

5 minutes ago, johninderby said:

If I win the lottery will let you know how well it performs from my villa in Tennerife. 😁😁😁

Dream on. 😕😢😢😢

Oi i want a invitation for the weekend 🤣 whoever wins it first is the host

[Peter Drew]

I have an 8" F8 planetary Newtonian built round a 1/20th wave OOUK optics set and a 12" F8.5 Newtonian with optics by unknown maker but tested and described by Wildey as being so perfect that nothing could be done to improve them.  I did at one time have a 12" F15 achromat objective with which I was going to make a folded refractor but sold it and bought a 16" SCT with the funds.     🙂

[Peter Drew]

I think there is a slight misconception regarding spherical optics of long focus Newtonian mirrors.  Both short focus paraboloids and long focus spheres are difficult to make.  If you want 1/10 wave performance you still need a 1/10th wave sphere.    🙂

[neil phillips]

34 minutes ago, Peter Drew said:

I think there is a slight misconception regarding spherical optics of long focus Newtonian mirrors.  Both short focus paraboloids and long focus spheres are difficult to make.  If you want 1/10 wave performance you still need a 1/10th wave sphere.    🙂

Fair enough Peter. Just something i thought i had read about figuring mirrors.  

[neil phillips]

43 minutes ago, Peter Drew said:

I have an 8" F8 planetary Newtonian built round a 1/20th wave OOUK optics set and a 12" F8.5 Newtonian with optics by unknown maker but tested and described by Wildey as being so perfect that nothing could be done to improve them.  I did at one time have a 12" F15 achromat objective with which I was going to make a folded refractor but sold it and bought a 16" SCT with the funds.     🙂

Once had 1/12th OOUK F7 300MM Newtonian sounds like you have had the kind of scopes i could really get my teeth into. Very interesting Peter

[Stu]

This was my longest scope; OO 300mm f6 which was a bit of a beast. For context, the scope beside it is an 8” f20 Mak (OMC200). It wasn’t very stable on the AYODigi II, much better on a dob mount. Anything longer much be completely insane!