Quite a lens!

[Chris]

On 27/02/2019 at 10:09, KP82 said:

Weighs in at 600kg lens only ... imagine how heavy the end scope is going to be. You'd need a crane to set this whole thing up.

Is this a typo though, I can't imagine a lens weighing over half a Ton. Maybe it is 60kg? which is still damn heavy. 

[RobertI]

On 27 February 2019 at 09:30, John said:

This is a 250mm F/16 refractor - imagine what a 500mm would be like

 

Crikey, you'd take your life in your hands trying to observe anything with that. At least he has a more useable 'grab and go' nearby! ?

[michael8554]

On 03/03/2019 at 06:48, beka said:

But really, why does this product actually exist and why would anyone buy it?

Pecival Lowell III wants to see the canals on Mars...........

Michael 

.

[Cosmic Geoff]

I suspect that the makers listed it mainly to incite threads like this, and sell their smaller models.  A 12" SCT would be so much more practical.?

[dannybgoode]

2 hours ago, Lockie said:

Is this a typo though, I can't imagine a lens weighing over half a Ton. Maybe it is 60kg? which is still damn heavy. 

600kg will be about right for a triplet of that size. Not light at all. 

The complete scope comes in about 1t from memory. 

[Chris]

47 minutes ago, dannybgoode said:

600kg will be about right for a triplet of that size. Not light at all. 

The complete scope comes in about 1t from memory. 

That's mind blowing! I'm not sure I've done this right, but using pi R squared to scale the thing down to a 6", it would weigh 55kg. This is only rough as it solves for area rather than volume. You could probably quarter that figure if the cell and glass were 1/4th as thick, but 14kg still seems reasonably heavy for a 6".  

I'll stick with doublets above 100mm! ?  

[Ags]

The weight will go up roughly by the cube (not square) of the radius. It's the classic problem of aperture fever: light gathering increases at the square of aperture but the mass increases at the cube of aperture! 

[Louis D]

On 05/03/2019 at 05:28, Ags said:

The weight will go up roughly by the cube (not square) of the radius. It's the classic problem of aperture fever: light gathering increases at the square of aperture but the mass increases at the cube of aperture! 

Unless you can remove mass as in a mirror by honeycombing it.  Of course, this doesn't work with traditional refractor lenses, but a similar principle could be applied using a modern variation on fresnal lenses.  I've read there's been work to use the same principle, but at the microscopic (nanoscopic?) level to flatten the bulge in large lenses without compromising optical performance.

[Sunshine]

On 27/02/2019 at 06:48, LukeSkywatcher said:

That just redonkilous.

Has anyone asked how this insane scope is carted in and out of this guys house? i mean, he's clearly at his house with this thing!.

[John]

3 minutes ago, Sunshine said:

Has anyone asked how this insane scope is carted in and out of this guys house? i mean, he's clearly at his house with this thing!.

I think he keeps them in his garage. His name is John Pons and he makes these scopes which incorporate lenses by the likes of Zeiss.

 

[Sunshine]

There is no way on earth that triplet alone weighs almost 1200lbs, maybe on Jupiter, (referring to the OP).

 

[Sunshine]

3 minutes ago, John said:

I think he keeps them in his garage. His name is John Pons and he makes these scopes which incorporate lenses by the likes of Zeiss.

 

Yess well, how does he mount the OTA? you'd need a small crane or something lol, i'm baffled.

[Chris]

25 minutes ago, Sunshine said:

There is no way on earth that triplet alone weighs almost 1200lbs, maybe on Jupiter, (referring to the OP).

 

I find it hard to believe also, a 600kg / 1320 lb 20" triplet? I'm tempted to message them to check. 

[Louis D]

2 hours ago, Lockie said:

I find it hard to believe also, a 600kg / 1320 lb 20" triplet? I'm tempted to message them to check. 

For reference, a Lockwood 1.4" thick, 20" wide mirror weighs 31 pounds.  That triplet weighs 43 times as much.  Is that triplet's lens cell made of depleted uranium?

[LukeSkywatcher]

I've only noticed the smaller scope....which in itself is huge.

[beka]

On 07/03/2019 at 02:13, Lockie said:

I find it hard to believe also, a 600kg / 1320 lb 20" triplet? I'm tempted to message them to check. 

I checked on  the internet and it seems glass can have a density of up to 8000kg per meter cubed. Calculating using this density and the diameter of 510mm it looks like it will have to be about 37cm thick - seems a bit high (are the lenses cemented or air/oil spaced ?  ). Lower density glass will make it even thicker. Also I think truss APOs should be illegal!

Best

[Chris]

6 minutes ago, beka said:

I checked on  the internet and it seems glass can have a density of up to 8000kg per meter cubed. Calculating using this density and the diameter of 510mm it looks like it will have to be about 37cm thick - seems a bit high (are the lenses cemented or air/oil spaced ?  ). Lower density glass will make it even thicker. Also I think truss APOs should be illegal!

Best

It doesn't look at least 15" thick on the pictures, that would make it about as thick as it is wide! Not sure if it's air or oil spaced either, but oil might be better for cooling because heat might conduct out the lens more quickly. 

I wouldn't want a truss Apo. The idea of an Apo is the highest contrast and the sharpest views possible surely. Also imagine having such a lens exposed to the 'elements'. 

[John]

Istar did a skeleton tube 6 inch refractor for a while:

 

[Ags]

That looks so wrong. And heavy too!

[John]

Just now, Ags said:

That looks so wrong. And heavy too!

The actual optical tube weight was low for a 150mm F/12 - about the same as for an F/8.

The heavy duty mount is still needed for the tube length however.