54 replies to this topic

[Shubham]

Exactly what mount is it where the eyepiece doesn't change height and angle? Even with a short focal length refractor, the seat height changes significantly..

 

Cost and transportability are important factors.. many/most of amateur astronomers travel to observe under dark skies...

 

Jon

Jon, my post was just in response to Don’s reply that an RC would have too big of a secondary to be useful for visual. I do agree that for most people wanting to have that big of an aperture at the lowest cost possible and some “portability”, a dob would be the preferred option. It’s just that I’d personally never want to own a scope larger than say a 16” f4 for visual where I can’t reach the eyepiece without a ladder if needed. This is also great if you want to observe with friends or family.

 

As for the ASA AZ800, that’s just one of the examples that if I REALLY wanted to go that big and had the money, I’d rather have that than bother with a dob. As for the eyepiece height, it is a Nasmyth design, so the eyepiece would remain at a height of 1.1m from the base allowing for comfortable seated viewing at all times. It can be configured to 4 Nasmyth ports allowing attachment of instrumentation like cameras, spectroscopes, etc., useful for photography and most importantly research applications (which interest me a lot). This scope is basically a dream scope for me. 

 

[Tony Flanders]

Exactly what mount is it where the eyepiece doesn't change height and angle?

The Naismyth and Coudé designs have an invariant eyepiece height and angle. Almost all truly big professional scopes have a Coudé option to allow attachment of massive spectroscopes and the like.

I've never seen either one in an amateur scope. As Jon says, the eyepiece height varies quite a bit in Cassegrains and their various catadioptric variants once you get to large apertures.

[NinePlanets]

The Springfield mount's eyepiece doesn't move at all.

[ClsscLib]

More insane is the ladder he uses:

https://www.wildcard...barbarella1.gif

Naw, dawg.

[Jon Isaacs]

The Naismyth and Coudé designs have an invariant eyepiece height and angle. Almost all truly big professional scopes have a Coudé option to allow attachment of massive spectroscopes and the like.

I've never seen either one in an amateur scope. As Jon says, the eyepiece height varies quite a bit in Cassegrains and their various catadioptric variants once you get to large apertures.

 

I am aware the various mounts which do not change eyepiece heights but I was asking about specific examples as they applied to the amateur astronomer.

 

 

I do agree that for most people wanting to have that big of an aperture at the lowest cost possible and some “portability”, a dob would be the preferred option. It’s just that I’d personally never want to own a scope larger than say a 16” f4 for visual where I can’t reach the eyepiece without a ladder if needed. This is also great if you want to observe with friends or family.

 

I'm not sure lowest cost is the right term.  Reasonable might be a better term. If one wants to avoid ladders, a 22 inch F/3 is as good as a 16 inch F/4.

 

Some ladders I find unacceptable. Too often it's a $10,000 telescope with a $100 ladder. I started out that way with my 25 inch F/5 but my wife put her foot down so I ended up with an industrial, Cotterman rolling, folding ladder. It's a way different experience..  with the railings and wide steps with a shallow climbing angle, no one ever balked at taking a look.

 

 

Quite transportable if you're young and strong.

 

 

The ladder for my current 22 inch F/4.4. it's really a rolling staircase as the angle is only 42°.  It's not pretty but it's effective. I doubled the steps so it's always comfortable. The railings provided security so one had two hands free.. the eyepiece rack is very nice, there's a large accessory tray and even a drink holder..

 

 

There are ladders and then there are ladders.

 

Jon

[Shubham]

There are ladders and then there are ladders. 

And then there are no ladders! 

[Starman1]

And then there are no ladders! 

Yup.  With my 16" f/3.75, I'm seated when the scope points at the zenith (61" eyepiece height).

For shorter people, my Starmaster chair doubles as a stool with hand railings when turned around the other direction.

[Kefka1138]

https://www.optiques.../photo-gallery/

Middle pic.

That's bananas cool. 

[Whiteduckwagglinginspace]

I have to disagree with this. A proper ladder for the scope can be quite comfortable to observe with. Matched properly there are no bad viewing positions.

Of course: it is a personal thing. I even prefer to have a smaller telescope than standing on a ladder - even a comfortable one. This invention (third mirror) is a blessing for people who don't like to observe on a ladder. Apparently there is a market for it. Too bad you have to make a request to find out the price. This fact tells me enough about the price.

[Jon Isaacs]

Of course: it is a personal thing. I even prefer to have a smaller telescope than standing on a ladder - even a comfortable one. This invention (third mirror) is a blessing for people who don't like to observe on a ladder. Apparently there is a market for it. Too bad you have to make a request to find out the price. This fact tells me enough about the price.

 

Have ever spent a night or two with a ladder custom built for a larger scope?

 

Very few have... 

 

Jon

[Whiteduckwagglinginspace]

Have ever spent a night or two with a ladder custom built for a larger scope?

 

Very few have... 

 

Jon

No, I didn't - but enough experience with several kind of ladders and never liked it. Last three years (because of sickdom), my sense of balance is completely out of control. Sitting on a good chair is my most stable position. If this was not the case, I would really like to try your ladder to proof me wrong.

Edited by Whiteduckwagglinginspace, 19 June 2025 - 02:02 PM.

[Jon Isaacs]

No, I didn't - but enough experience with several kind of ladders and never liked it. Last three years (because of sickdom), my sense of balance is completely out of control. Sitting on a good chair is my most stable position. If this was not the case, I would really like to try your ladder to proof me wrong.

 

Sitting is my preference. But it's important that's it's not just any chair, a chair designed specifically for astronomy is important.

 

Its the same with ladders but even more so. If some has balance issues, even the best ladder may be risky at night. But otherwise, my ladder is allows me to view in comfort. 

 

If you ever make it to Southern California, I'd be happy for you to visit.

 

Jon

[Whiteduckwagglinginspace]

Sitting is my preference. But it's important that's it's not just any chair, a chair designed specifically for astronomy is important.

 

Its the same with ladders but even more so. If some has balance issues, even the best ladder may be risky at night. But otherwise, my ladder is allows me to view in comfort. 

 

If you ever make it to Southern California, I'd be happy for you to visit.

 

Jon

At this moment, I'm using a desk chair / office chair for my 8 incher. But when the 12 incher comes this summer, it will be a bit too low I guess.

If this day comes (traveling to America), I will certainly(!) do that. Let me know when you're in Norway for some reason. We have a big house and even bigger hospitality - cheers!

Edited by Whiteduckwagglinginspace, 19 June 2025 - 03:47 PM.

[Dave Mitsky]

Here's a photo of Jon Vogt, his 32" f/4 ATM Dob, and ladder that I took at Stellafane last year.

 

https://stellafane.o.../vogt/vogt.html

Attached Thumbnails

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[Jon Isaacs]

Here's a photo of Jon Vogt, his 32" f/4 ATM Dob, and ladder that I took at Stellafane last year.

 

https://stellafane.o.../vogt/vogt.html

 

Nice scope but not a ladder I'd consider climbing. 

 

Jon

[MeridianStarGazer]

Fullum makes scopes up to 65".
...

So does Lockwood. I can't afford either one though.

[dustyc]

Mike makes mirrors,not completed scopes.

[MeridianStarGazer]

I read that reflectors can be made bigger if a cluster of mirrors is used. Why?
Can amateurs go bigger if a cluster is used?

[Shubham]

I read that reflectors can be made bigger if a cluster of mirrors is used. Why?
Can amateurs go bigger if a cluster is used?

Does not make any sense for apertures smaller than at least a few meters. Pretty much all professional observatories with telescopes in diameter up to about 8 meters use a monolithic mirror.

Making and operating a segmented mirror telescope is very complicated. The segments cannot be flat, nor can they be a regular parabolic or hyperbolic shape with the center of optical axis coinciding with the center of the segment. Each segment has to be made with a unique figure to represent the exact part of the parabola or hyperbola (of the combined mirror) that it would be placed in. And then each segment has to have precise actuators placed underneath to achieve collimation across all the individual segments.

Edited by Shubham, 22 June 2025 - 09:20 PM.

[MeridianStarGazer]

Mike makes mirrors,not completed scopes.

For sale, true. But he did make his own 20" f3 scope.

Edited by MeridianStarGazer, 23 June 2025 - 09:31 AM.

[MeridianStarGazer]

Maintaining 1/4 wave accuracy across such a large mirror is absolutely impressive.

[dustyc]

There are two threads in the reflector forum concerning the large Fullum scopes. A 50" and a 1 meter. With pics! The secondary on that 50' is larger than the primary mirrors of most telescopes here. 

[Dave Mitsky]

Nice scope but not a ladder I'd consider climbing. 

 

Jon

It's not as bad as it looks in that photo, Jon.  I've been up that ladder a number of times over the years.

[Keith Rivich]

It's not as bad as it looks in that photo, Jon.  I've been up that ladder a number of times over the years.

At the minimum it needs half steps, makes all the difference...

[oldphotonm]

As my age (and the physical decrepitude that comes with it) advances, my single biggest comfort factor now is having a 3-step platform ladder with W.I.D.E. steps. Those dreadful painters ladders with their narrow step width are simply murder on my poor feet. Too many frayed tendons and too many bouts of plantar fasciitis. Thankfully, at 6'-3" tall, a 3-step platform ladder is all I need with my 20" f/5. And my 14.5" f/5? A joy to use with feet on the ground 95% of the time.