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Long slow Newtonians

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#126 CollinofAlabama

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Posted 24 January 2019 - 01:31 AM

My TAL has a spherical mirror like SW F8 6" Newts.


The SkyWatcher Traditional Dobsonian series all have parabolic mirrors.

#127 NHRob

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Posted 24 January 2019 - 07:24 AM

I have a 8" f/7.75. (62" FL) mirror on order.  It is to become my retirement project .. a high performance visual dob.

Probably do a solid tube but, am researching different design options for best thermal and optical performance.


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#128 Galicapernistein

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Posted 24 January 2019 - 09:28 AM

I have a 8" f/7.75. (62" FL) mirror on order.  It is to become my retirement project .. a high performance visual dob.

Probably do a solid tube but, am researching different design options for best thermal and optical performance.

I have an 8” F9 OPT Planet Pro, no longer made, unfortunately. It’s a truss dob with the tube parts made of sonotube. I’m looking into converting the upper tube assembly to aluminum to improve the balance. Parallax Instruments has a good selection of aluminum tubes. Another option is to make a split-tube aluminum dob using Discovery hardware.


Edited by Galicapernistein, 24 January 2019 - 09:28 AM.

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#129 TOMDEY

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Posted 24 January 2019 - 10:25 PM

I had a (professionally-made and certified) 12-inch F/100... that I was going to use for a solar imager. Just never got around to it. I waited for the sun to get just above our 100-ft building, with the tech on the ground with the mirror on mount and aimed where I was, with a screen, on a tripod, up on the roof. The 10.5-inch image was bright and razor sharp, right there on the screen! They even made the 16-inch folding flat to feed the thing, eventually... but I just never got around to it.    Tom



#130 Auburn80

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Posted 25 January 2019 - 12:36 AM

I had a (professionally-made and certified) 12-inch F/100... that I was going to use for a solar imager. Just never got around to it. I waited for the sun to get just above our 100-ft building, with the tech on the ground with the mirror on mount and aimed where I was, with a screen, on a tripod, up on the roof. The 10.5-inch image was bright and razor sharp, right there on the screen! They even made the 16-inch folding flat to feed the thing, eventually... but I just never got around to it. Tom


😲 wow. Would love to have seen that!

#131 Shneor

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Posted 25 January 2019 - 02:12 AM

A fellow observer - President of the local astronomy club at the time, about 25 years ago - had a 14" f/7. I just remember having one view through it, all I remember is that it was very sharp. But he developed an interest in motorcycling and apparently left the hobby.



#132 CHASLX200

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Posted 25 January 2019 - 06:32 AM

A fellow observer - President of the local astronomy club at the time, about 25 years ago - had a 14" f/7. I just remember having one view through it, all I remember is that it was very sharp. But he developed an interest in motorcycling and apparently left the hobby.

That would be a dream scope for my taste.  But the size of the tube would be a killer and too heavy to mount up.  I think the perfect scope for me would be a Dob in the 18 to 20" size and a speed of F/6 for my planet viewing.  Since i would only a few objects a nite moving a ladder would not be a problem and i grew up with a 10" F/9.6, so ladder scopes are my thing.



#133 25585

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Posted 25 January 2019 - 01:58 PM

Just a FYI, here is a 18.25 inch 1973 vintage Newtonian in SW England, UK. http://www.starsover...ry - Part 1.htm

 

Since the site was last updated, its mirror has been serviced for what is likely to be the last time of usefulness, perhaps it has had to be re-figured too many times. The mirror was probably hand ground originally.

 

That big scope has been used to look for exo-planets among other tasks. Nice location. https://gostargazing...ctivity-centre/

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Edited by 25585, 25 January 2019 - 02:05 PM.

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#134 TOMDEY

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Posted 25 January 2019 - 07:53 PM

I remember, long ago, the Syracuse Club had a Cave Astrola Professional Model in a big roll-off, at their nice rural site. That was really huge, for that era. All I remember was that it looked LONG, awesome, and pretty cumbersome. Now, I've got a 36-inch in a dome [I may have shyly mentioned that once, twice or a hundred times]. My 36 is F/3.75 on a Dob GoTo etc... compact for so much aperture [he feverishly said]. The Lick 36-inch is 57 feet long! "Ha ha Ha HA Ha ha heh... snort"

 

Who am I kiddin' Now that my scope is finally fat enough... I wish it were longer...    Tom

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#135 CHASLX200

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Posted 25 January 2019 - 07:59 PM

Just a FYI, here is a 18.25 inch 1973 vintage Newtonian in SW England, UK. http://www.starsover...ry - Part 1.htm

 

Since the site was last updated, its mirror has been serviced for what is likely to be the last time of usefulness, perhaps it has had to be re-figured too many times. The mirror was probably hand ground originally.

 

That big scope has been used to look for exo-planets among other tasks. Nice location. https://gostargazing...ctivity-centre/

That would be a back breaker for sure to mount up.


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#136 Shneor

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Posted 26 January 2019 - 02:40 AM

That would be a dream scope for my taste.  But the size of the tube would be a killer and too heavy to mount up.  I think the perfect scope for me would be a Dob in the 18 to 20" size and a speed of F/6 for my planet viewing.  Since i would only a few objects a nite moving a ladder would not be a problem and i grew up with a 10" F/9.6, so ladder scopes are my thing.

As I recall, it was a truss, not a tube.



#137 CHASLX200

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Posted 26 January 2019 - 07:30 AM

As I recall, it was a truss, not a tube.

I had a 14.5" F/6 in a Parks Tube and i had to rig up a way to roll it out and line up the ring mount bolts with the saddle holes as there was no way i could lift it up to mount up. A 16" OD tube it just too big to grab and lift up.



#138 Deep13

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Posted 02 February 2019 - 01:57 AM

The name of this thread sounds like a Little Richard song.
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#139 rguasto

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Posted 03 February 2019 - 10:30 AM

Here's my 8" f8 on a dob mount.  I've gotten some not so nice comments on the classics forum for putting it on a dob mount. It's so much better than the inadequate gem it came with.  This is my largest aperture telescope. It doesn't fit in any vehicle I own but not because of the OTA, because of the mount. I have to transport it in my dirt bike cargo trailer. 

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#140 Galicapernistein

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Posted 03 February 2019 - 11:15 AM

Here's my 8" f8 on a dob mount.  I've gotten some not so nice comments on the classics forum for putting it on a dob mount. It's so much better than the inadequate gem it came with.  This is my largest aperture telescope. It doesn't fit in any vehicle I own but not because of the OTA, because of the mount. I have to transport it in my dirt bike cargo trailer. 

I have an 8” F9 truss on a dob mount, and I have no problem tracking. I had a 10” F5.6 Discovery dob that put up great images, but in comparison to the 8”,  it just couldn’t compete at high powers, so I sold it. For me, a GEM isn’t something that would be worth the trouble.



#141 Jeff Morgan

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Posted 03 February 2019 - 11:29 AM

Here's my 8" f8 on a dob mount.  I've gotten some not so nice comments on the classics forum for putting it on a dob mount. It's so much better than the inadequate gem it came with.  This is my largest aperture telescope. It doesn't fit in any vehicle I own but not because of the OTA, because of the mount. I have to transport it in my dirt bike cargo trailer. 

Very interesting build!

 

I take it the entire OAT can be moved along the altitude cradle for balance? Are the silver objects trimming weights, or knobs for securing the OTA?



#142 rguasto

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Posted 03 February 2019 - 12:31 PM

Very interesting build!

I take it the entire OAT can be moved along the altitude cradle for balance? Are the silver objects trimming weights, or knobs for securing the OTA?


Those are the original criterion knobs and yes it can slide in the cradle about 3".

-Rob

#143 SandyHouTex

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Posted 03 February 2019 - 01:00 PM

I just jumped on the longer focal length reflector band wagon.  I have a ton of f/4 to f/5 newtonians, and I’m tired of having to screw with a Paracorr all the time.  So before their gone, I just ordered a 4 1/4 inch f/8 Celestron Power Seeker and the 6 inch f/8 Skywatcher dob.  We’ll see what they can do.


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#144 25585

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Posted 03 February 2019 - 08:35 PM

Here's my 8" f8 on a dob mount.  I've gotten some not so nice comments on the classics forum for putting it on a dob mount. It's so much better than the inadequate gem it came with.  This is my largest aperture telescope. It doesn't fit in any vehicle I own but not because of the OTA, because of the mount. I have to transport it in my dirt bike cargo trailer. 

Looks great! Never mind retroists, your mount is fine and practical.  


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#145 Galicapernistein

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Posted 04 February 2019 - 12:34 PM

I just jumped on the longer focal length reflector band wagon.  I have a ton of f/4 to f/5 newtonians, and I’m tired of having to screw with a Paracorr all the time.  So before their gone, I just ordered a 4 1/4 inch f/8 Celestron Power Seeker and the 6 inch f/8 Skywatcher dob.  We’ll see what they can do.

Unfortunately, there aren’t any options for non-mass produced slow dobs above 6” anymore, that I know of. But I think you’ll find that a 6” F8 can easily outperform an F4 or F5 of the same size.



#146 TxStars

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Posted 04 February 2019 - 04:41 PM

Im sure that at least one of the current mirror and scope makers would be happy to do a long scope if someone were to ask for one.

Also the long scopes come up for sale a good bit as many are jumping on the f/4 and under ship...


Edited by TxStars, 04 February 2019 - 04:41 PM.


#147 TOMDEY

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Posted 04 February 2019 - 04:58 PM

After six pages of this... notable that we may be (understandably) reacting to the Ultra-Fast Ultra-Light binge of the past few years. Scopes that are like two-foot window glass mirrors, Short as an oil drum, tentatively held together with broom sticks and twine, and blow around in the wind like tumbleweeds... Like all things... taken beyond reasonable extreme... just for the sake of it.

 

Maybe long slow Newts and long slow achromatic doublets will return to prominence!

 

NOTE: Notice how radio silence has descended on the recently touted "flat" telescope hype?! Gone the way of Cold Fusion and Tac Glasses.    Tom


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#148 starcanoe

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Posted 04 February 2019 - 05:00 PM

Long slow newtonians are where people with less money than they would like to have to spend (but still want top notch images) on astrogear fear to tread....

 

Well, actually the people with LESS money fear the treading virtually none...its the people WITH the money that can't "do without" or understand the people that can/are forced to do so...


Edited by starcanoe, 04 February 2019 - 05:05 PM.


#149 Pezdragon

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Posted 04 February 2019 - 06:00 PM

I’ve been using my “Orchid”, a 10” f-8 since I built it back in 1969. This is its last days as a f-8 though. In a few weeks ZOC will be finishing a new 10” f6.4 (gasp) primary for it. I have always loved long slow dobs in fact I was tutored by the man himself who thought anything below f-6 was well...a pig. Don’t get me wrong though, the fast scopes have theirs own attractions and strong points. I just like to keep the flame going for the slow ones....if f 6.4 can still be considered slow....

 

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#150 SandyHouTex

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Posted 05 February 2019 - 10:15 AM

One of my mottos is "newer isn't always better".


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