Ed,

I think your designs that use commercial lenses (even though they may not be
perfectly optimized) and off the shelf mirrors will be key to getting this
design into the hands of a lot more ATMers. As you mention a small percentage of
ATMs actually make their own mirrors, and I'd be willing to bet an equally small
percentage of those who do will take the next step to make their own lenses....
I think I see an opportunity for you to earn some extra beer money there!

I didn't realize that Cheifs can go as fast as f/5 or f/6 with all the longer FR
designs I've been looking at and for a general purpose scope the longer FRs
probably more useful anyway. Good point about the secondary shadow too, hadn't
thought about that.

All in all I agree with you. More complex construction and alignment (lens
adjustment) aside, your design does appear to be the better all 'round scope.
The point I was making was that for some ones first scope build or specialized
applications like AP and RFTs I feel the Newt will still get used.... and not
fade away like has been alluded to.

Yup, I think it's going to be popular. Thanks Ed! <thumbs up>

Ryan

--- In spiderless@yahoogroups.com, "Ed" <opticsed@...> wrote:
>
> Ryan,
>   I agree, the Newtonian will be around for a while because it is easy to make
with only 2 mirrors and is fast which is important for astrophotography. The
Chief is definitely more complicated than the Newt but shouldn't deter most
ATMs. I think the fact that the optics in some cases can be bought will
eventually make the Chief the most common unobstructed scope because
unfortunately fewer ATMs get into mirror making. The Chief can be no faster than
about f/5 to F/6 but if it isn't too slow you can still reach minimum power or
close to it with some eyepieces (except maybe the Naglers).  I suppose you could
always use a telecompressor to use the Naglers at minimum power and the long BLF
should allow it but that's a little crazy. The Chief has some low power
advantages over the Newt though, it has better baffeling making a darker field
and there is no diagonal shadowing that you can sometimes see in Newts. The big
advantage for the Chief is high power and so you could argue that it's a better
all around scope. Eyepiece height is important and the Chief is at least
competative with Newtonians except for the ultra short ones.
>
> Ed

Ryan,
   I agree, the Newtonian will be around for a while because it is easy to make
with only 2 mirrors and is fast which is important for astrophotography. The
Chief is definitely more complicated than the Newt but shouldn't deter most
ATMs. I think the fact that the optics in some cases can be bought will
eventually make the Chief the most common unobstructed scope because
unfortunately fewer ATMs get into mirror making. The Chief can be no faster than
about f/5 to F/6 but if it isn't too slow you can still reach minimum power or
close to it with some eyepieces (except maybe the Naglers).  I suppose you could
always use a telecompressor to use the Naglers at minimum power and the long BLF
should allow it but that's a little crazy. The Chief has some low power
advantages over the Newt though, it has better baffeling making a darker field
and there is no diagonal shadowing that you can sometimes see in Newts. The big
advantage for the Chief is high power and so you could argue that it's a better
all around scope. Eyepiece height is important and the Chief is at least
competative with Newtonians except for the ultra short ones.

Ed


--- In spiderless@yahoogroups.com, "rcmcivor@..." <rcmcivor@...> wrote:
>
> I doub't the Cheif will replace newts like you've mentioned before for
reason's you've mentioned below. They are easy and work very well. But I feel
this way for advanced builders as well. There's one thing that Cheifs can't do
and that's short FR's. It's not always about getting the EP height down but
being able to get low power views with a good amount of aperture... I LOVE low
power viewing myself.
>
> I'm certainly not poo pooing on Ed's design as the advantages of his design
become apparent at higher mags, you get a long FR with lots of aperture and a
reasonable EP height to boot plus no diffraction. I'll absolutely be building a
Cheif for myself if I can ever decide on a size. Finding time to fab the optics
and build a scope would be a plus too.
>
> Ryan
>
>
>
> --- In spiderless@yahoogroups.com, "kevin" <airfrederick@> wrote:
> >
> > A Newtonian is hard to beat. Easy to understand .Two mirrors works great.
every time. any size .So why muddy the water making some thing that only a fiew
people understand and they need the help of computers to make it work .Why spend
time and money on something that may not work ? For me it was about working with
some one who i could learn alot from . I didnot need another telescope .I only
got CHief sprinkler itis after seeing the moon in the 20 INCH CHief .
> >
>

I agree with you. What it has replaced however, is the Schiefspiegler.
In fact the Chief has virtually overwhelmed the Schief which was never
popular in spite of 50 (?) years or more of opportunity; ample time to
get a toehold. There has to be a reason for it's failure to win over
astronomers.

A quick check of two other Schief associated groups here at Yahoo
reveals a dramatic fall off in activity.

Delmarva had no activity at all in November.

The Schiefspiegler group has not seen any activity since 2008!

Ed's site, by comparison is like Grand Central Station!

What does all that tell you?

Thanks Ed!

Art






<rcmcivor wrote:
>
> I doubt the Chief will replace newts like you've mentioned before for
reason's you've mentioned below.

I doub't the Cheif will replace newts like you've mentioned before for reason's
you've mentioned below. They are easy and work very well. But I feel this way
for advanced builders as well. There's one thing that Cheifs can't do and that's
short FR's. It's not always about getting the EP height down but being able to
get low power views with a good amount of aperture... I LOVE low power viewing
myself.

I'm certainly not poo pooing on Ed's design as the advantages of his design
become apparent at higher mags, you get a long FR with lots of aperture and a
reasonable EP height to boot plus no diffraction. I'll absolutely be building a
Cheif for myself if I can ever decide on a size. Finding time to fab the optics
and build a scope would be a plus too.

Ryan



--- In spiderless@yahoogroups.com, "kevin" <airfrederick@...> wrote:
>
> A Newtonian is hard to beat. Easy to understand .Two mirrors works great.
every time. any size .So why muddy the water making some thing that only a fiew
people understand and they need the help of computers to make it work .Why spend
time and money on something that may not work ? For me it was about working with
some one who i could learn alot from . I didnot need another telescope .I only
got CHief sprinkler itis after seeing the moon in the 20 INCH CHief .
>

A Newtonian is hard to beat. Easy to understand .Two mirrors works great. every
time. any size .So why muddy the water making some thing that only a fiew people
understand and they need the help of computers to make it work .Why spend time
and money on something that may not work ? For me it was about working with some
one who i could learn alot from . I didnot need another telescope .I only got
CHief sprinkler itis after seeing the moon in the 20 INCH CHief .

John welcome to spiderless and also to all the new folks who have joined lately.
   It's interesting to hear about your experiments trying different aperture
stops. The Airy disk is supposed to not be round if the stop is nor circular at
least according to Zemax but I've never tried it.

Ed

--- In spiderless@yahoogroups.com, "mnemnon_53" <John.E.Bishop@...> wrote:
>
> Hi!  I saw the S&T reference to "spiderless" and have now read all the
postings and looked at some of the photos and files.
>
> I have three of the DGM Optics telescopes.  They are off-axis, eccentric-pupil
Newtonians: the primary is an off-axis section of a parabolic mirror and not
tilted.  The flat secondary is over the center of the "parent" mirror and thus
not in the incoming light path.  They are around f/10 (varies by model).
>
> I've been posting about my telescopes in the Yahoo "offaxis" group which
focuses on unobstructed mirror-based telescopes.  I have the 3.6-inch, the
6.5-inch and recently got the 9.0-inch.
>
> The main difference between these and the CHiefs is that the DGM Optics design
has to be f/10 or slower and doesn't lend itself as well to bending the light
path back in the direction to the primary mirror.  Thus large apertures mean
very long telescopes.  With the 9.0-inch, the tube is 80 inches long; viewing
requires a ladder for most of the sky (though I only need to go up two steps for
the area right around zenith).
>
> To answer some questions in old postings:
>
> 1.  How many commercial off-axis telescopes are out there?
>
> I believe that DGM Optics sold a number in the one to few hundreds, mostly of
the smaller models, based on what I've heard.  I have no firm data.
>
> 2.  What about making elliptical off-axis child mirrors of a parabolic mirror
(message 752)?
>
> I experimented with off-axis masks on a 16-inch standard Newtonian.  I tried a
round opening and a rounded oval that was the biggest shape I could cut which
would not overlap an edge or a secondary mirror support and which was convex on
all sides (i.e., not a "kidney bean" shape with a part that goes in).
>
> With these non-round masks, the outer part of the defocused image of a star
showed the shape of the opening, but the rings quickly become round in the
interior of the image.  When focused, I didn't see any bad consequence of the
shape.
>
> In a 4-inch I once tried a triangular opening, but can't remember whether
there were 'spikes' around a focused star.
>
>    -John
>

Good Morning Dennis!

Thanks! The probability is high that most people will elect a motorized Poncet style altitude table like Ed's and leave the sector drive to those with a knowledge of microprocessors and steppers.

As indicated in the photo section comments, one disadvantage of a center mounted sector drive is that it interferes with the logical location for the axle needed by the Azimuth table. Without that shaft to spin on one must add bearings, a circular track and a rigid precision structure to hold it all.

That adds weight and while the CG isn't a factor in the design and construction of the base of a conventional Dob, it is one more thing we have to lift into the trunk of the car.

"Clear Skies and Apple Pies!"

Art
--- In spiderless@yahoogroups.com, "Dennis Sheridan" <balsawood@...> wrote:
>
> Art,
>
> I like your center driven concept with the side sectors running thru channels in the base board. Not only does it torsional problems being driven from the center but it also lowers the CG. Also with the side sectors in the channels an increase in the pulse rate is less likely to occur.
>
> Take care,
> Dennis
>
>
> ----- Original Message -----
> From: "Mr. Wizard!"
> To: spiderless@yahoogroups.com
> Sent: Tuesday, December 01, 2009 3:27 AM
> Subject: [spiderless] Re: Things are too quiet!
>
>
>
>
> No, I am not asleep. In fact I wish I could get a solid 8 hours!
>
> I've just returned from an 8 day trip to property in Mexico and spent much of my time on the flights down and back on my lap top, studying the geometry of the Alt-Az mount designed for the Giant Magellan Telescope (GMT). What a fantastic machine! And HUGE!
>
> The result is a structural change to the design of the typical Dobsonian that promises to:
>
> 1. eliminate the altitude box completely,
>
> 2. lower the entire scope in the process and
>
> 3. lower the CG of the entire system.
>
> It may also lower the total weight as well, something younger astronomers will eventually come to appreciate.
>
> If I sound a little less than certain it's because in my rush to do a preliminary study, I did not assign material properties to the materials or components used. Since I do not know the weight of each of those, the system can't calculate total weight much less the center of gravity.
>
> However, based on the use of composite materials and past experience, all those things should be possible. I may incorporate a Poncet type drive as an integral part of the design, rather than as a separate component.
>
> CG issues appear to be the biggest obstacle to the amount of time one can view with a Dobsonian scope on a motorized base. Lowering the design will not only make it possible to lower the eyepiece but the reduced elevation of the CG will increase the time available before the CG shifts so far outside the stability envelope to cause an increase in our pulse rates.
>
> I'll post some renderings of the design in a dedicated album in the Photo section including some designs for sector drives one might consider in lieu of a Poncet Drive. There will just be images for now. When I catch my breath I'll return and add some text.
>
> And now I AM going back to sleep!
>
> Art
>
> --- In spiderless@yahoogroups.com, "Ed" opticsed@ wrote:
> > >
> > > Is everyone asleep in telescope land?
> > >
> >
>

Hi Jack!

There is sufficient detail in the concept model for you to tease a
design of your own into existence. However, the weight of the structure
and the Center of Gravity have to be the center of focus from the very
first part you make.

Once you've built something, it's too late to make any meaningful
reductions in weight. You have to be downright fanatical in sizing parts
and how they are made. On all my weight sensitive projects, I vacuum bag
composites to extract unecessary extra epoxy from the weave and weigh
everything on a postage or UPS scale.

Because of their uncertainty about structures, ATM's tend to over design
and overbuild everything. Engineers are no different: they just have
more money to play with.

End grain balsa wood is a great structural core material for use in
fiberglass sandwiches. I use 3 lb/cu-ft low density foam instead. It's
cheaper and it doesn't soak up epoxy like balsa does. I just picked up a
4' by 8' sheet of half inch insulating foam at Loew's I'll experiment
with. I'd have preferred quarter inch thick but that's only available in
aircraft grade and many times more expensive.

Mass grows incrementally, an ounce at a time, and the CG changes with
it. Rather than add weight to the mirror box to balance the OTA, one
needs to remove weight from the secondary cage and truss. That's hard to
do, especially if you are a fan of Ed Nagler's better EP's!

Ideally, the CG should be just in front of the primary reflective
surface and almost touching it! The optical ladder design that Ed uses,
if made from cored composites, is featherlight yet mechanically rigid
and helps a great deal in this battle..

Ed is writing a book on the Chief design to be published some day by
Willman-Bell. W-B's commitment to publish is contingent on his not
giving away too many details otherwise, what would be the point?

In the past, he has responded to this question by telling others that
there is enough information in his sketches to get the job done. I
agree. The basic scope is very simple to build. Any uncertainty I have
about the design is in the size and placement of the lens holders and
the angles of the geometry at the top of the ladder. The good news there
is that you can adjust things as you go to get it right.

Art

PS: I edited the comments with the images I uploaded and added some
info.


--- In spiderless@yahoogroups.com, Jack Brooks <jbrooks@...> wrote:
>
> Art,
>
> Such a mount design as you are describing that eliminates the
> altitude box sounds VERY interesting. I am eager to see it. I have
> been constructing a truss tube for my ribbed lightweight 14.5 inch
> mirror, and getting the cg low enough has been a battle, constantly
> re-calculating the cg as I add, or subtract something.
>
> I am new to this group, and wonder if there is someplace on the site
> that describes the design of the "chief" spiegler? I know what most
> of the off axis designs are, but not that one.
>
> Jack Brooks
>
>
> On Dec 1, 2009, at 3:27 AM, Mr. Wizard! wrote:
>
> >
> > No, I am not asleep. In fact I wish I could get a solid 8 hours!
> >
> > I've just returned from an 8 day trip to property in Mexico and
> > spent much of my time on the flights down and back on my lap top,
> > studying the geometry of the Alt-Az mount designed for the Giant
> > Magellan Telescope (GMT). What a fantastic machine! And HUGE!
> >
> > The result is a structural change to the design of the typical
> > Dobsonian that promises to:
> >
> > 1. eliminate the altitude box completely,
> >
> > 2. lower the entire scope in the process and
> >
> > 3. lower the CG of the entire system.
> >
> > It may also lower the total weight as well, something younger
> > astronomers will eventually come to appreciate.
> >
> > If I sound a little less than certain it's because in my rush to do
> > a preliminary study, I did not assign material properties to the
> > materials or components used. Since I do not know the weight of
> > each of those, the system can't calculate total weight much less
> > the center of gravity.
> >
> > However, based on the use of composite materials and past
> > experience, all those things should be possible. I may incorporate
> > a Poncet type drive as an integral part of the design, rather than
> > as a separate component.
> >
> > CG issues appear to be the biggest obstacle to the amount of time
> > one can view with a Dobsonian scope on a motorized base. Lowering
> > the design will not only make it possible to lower the eyepiece but
> > the reduced elevation of the CG will increase the time available
> > before the CG shifts so far outside the stability envelope to cause
> > an increase in our pulse rates.
> >
> > I'll post some renderings of the design in a dedicated album in the
> > Photo section including some designs for sector drives one might
> > consider in lieu of a Poncet Drive. There will just be images for
> > now. When I catch my breath I'll return and add some text.
> >
> > And now I AM going back to sleep!
> >
> > Art
> >
> > --- In spiderless@yahoogroups.com, "Ed" opticsed@ wrote:
> > > >
> > > > Is everyone asleep in telescope land?
> > > >
> > >
> >
> >
> >
>

----- Original Message -----

From: "Mr. Wizard!"

To: spiderless@yahoogroups.com

Sent: Tuesday, December 01, 2009 3:27 AM

Subject: [spiderless] Re: Things are too quiet!

 

No,  I am not asleep. In fact I wish I could get a solid 8 hours!

I've just returned from an 8 day trip to property in Mexico and spent much of my time on the flights down and back on my lap top, studying the geometry of the Alt-Az mount designed for the Giant Magellan Telescope (GMT). What a fantastic machine! And HUGE!

The result is a structural change to the design of the typical Dobsonian that promises to:

1. eliminate the altitude box completely,

2. lower the entire scope in the process and

3. lower the CG of the entire system.

It may also lower the total weight as well, something younger astronomers will eventually come to appreciate.

If I sound a little less than certain it's because in my rush to do a preliminary study, I did not assign material properties to the materials or components used. Since I do not know the weight of each of those, the system can't calculate total weight much less the center of gravity.

However, based on the use of composite materials and past experience, all those things should be possible. I may incorporate a Poncet type drive as an integral part of the design, rather than as a separate component.

CG issues appear to be the biggest obstacle to the amount of time one can view with a Dobsonian scope on a motorized base. Lowering the design will not only make it possible to lower the eyepiece but the reduced elevation of the CG will increase the time available before the CG shifts so far outside the stability envelope to cause an increase in our pulse rates.

I'll post some renderings of the design in a dedicated album in the Photo section including some designs for sector drives one might consider in lieu of a Poncet Drive. There will just be images for now. When I catch my breath I'll return and add some text.

And now I AM going back to sleep!

Art

--- In spiderless@yahoogroups.com, "Ed" opticsed@ wrote:
> >
> > Is everyone asleep in telescope land?
> >
>

Hi!  I saw the S&T reference to "spiderless" and have now read all the postings
and looked at some of the photos and files.

I have three of the DGM Optics telescopes.  They are off-axis, eccentric-pupil
Newtonians: the primary is an off-axis section of a parabolic mirror and not
tilted.  The flat secondary is over the center of the "parent" mirror and thus
not in the incoming light path.  They are around f/10 (varies by model).

I've been posting about my telescopes in the Yahoo "offaxis" group which focuses
on unobstructed mirror-based telescopes.  I have the 3.6-inch, the 6.5-inch and
recently got the 9.0-inch.

The main difference between these and the CHiefs is that the DGM Optics design
has to be f/10 or slower and doesn't lend itself as well to bending the light
path back in the direction to the primary mirror.  Thus large apertures mean
very long telescopes.  With the 9.0-inch, the tube is 80 inches long; viewing
requires a ladder for most of the sky (though I only need to go up two steps for
the area right around zenith).

To answer some questions in old postings:

1.  How many commercial off-axis telescopes are out there?

I believe that DGM Optics sold a number in the one to few hundreds, mostly of
the smaller models, based on what I've heard.  I have no firm data.

2.  What about making elliptical off-axis child mirrors of a parabolic mirror
(message 752)?

I experimented with off-axis masks on a 16-inch standard Newtonian.  I tried a
round opening and a rounded oval that was the biggest shape I could cut which
would not overlap an edge or a secondary mirror support and which was convex on
all sides (i.e., not a "kidney bean" shape with a part that goes in).

With these non-round masks, the outer part of the defocused image of a star
showed the shape of the opening, but the rings quickly become round in the
interior of the image.  When focused, I didn't see any bad consequence of the
shape.

In a 4-inch I once tried a triangular opening, but can't remember whether there
were 'spikes' around a focused star.

    -John

Now that's really cool, Ed! Stack that on a long focus Schief, and you'd have
practically all the bases covered- low to high powers, in a very portable
package.
Very interesting!

(wasn't asleep, just postulating the swelling wasteline!)
Mark

No,  I am not asleep. In fact I wish I could get a solid 8 hours!

I've just returned from an 8 day trip to property in Mexico and spent much of my time on the flights down and back on my lap top, studying the geometry of the Alt-Az mount designed for the Giant Magellan Telescope (GMT). What a fantastic machine! And HUGE!

The result is a structural change to the design of the typical Dobsonian that promises to:

1. eliminate the altitude box completely,

2. lower the entire scope in the process and

3. lower the CG of the entire system.

It may also lower the total weight as well, something younger astronomers will eventually come to appreciate.

If I sound a little less than certain it's because in my rush to do a preliminary study, I did not assign material properties to the materials or components used. Since I do not know the weight of each of those, the system can't calculate total weight much less the center of gravity.

However, based on the use of composite materials and past experience, all those things should be possible. I may incorporate a Poncet type drive as an integral part of the design, rather than as a separate component.

CG issues appear to be the biggest obstacle to the amount of time one can view with a Dobsonian scope on a motorized base. Lowering the design will not only make it possible to lower the eyepiece but the reduced elevation of the CG will increase the time available before the CG shifts so far outside the stability envelope to cause an increase in our pulse rates.

I'll post some renderings of the design in a dedicated album in the Photo section including some designs for sector drives one might consider in lieu of a Poncet Drive. There will just be images for now. When I catch my breath I'll return and add some text.

And now I AM going back to sleep!

Art

--- In spiderless@yahoogroups.com, "Ed" opticsed@ wrote:
> >
> > Is everyone asleep in telescope land?
> >
>

Nope. Still plan to make a chief but the honey-do list keeps piling up.



--- In spiderless@yahoogroups.com, "Ed" <opticsed@...> wrote:
>
> Is everyone asleep in telescope land?
>

Is everyone asleep in telescope land?

Congratulations Kevin, nice picture and article in Sky & Tel. Now that you're
famous can I get your autograph?

Ed

ED and I are making a 16 f 10 offaxis CHief the telescope will be 8.5 ft and the
EYEPIECE IS UNDER 4 FT  from the primary .The primary 1 5/8 inch thick pyrex
[26lbs] is fully polished but not done yet.EDS telescopes are so cool .kevin
frederick

I have a 16 inch pyrex 1 5/8 thick mirror all polished out . the RC is 330 f
10.3 still have correcting to do. Should make a killer chief !!

Yes it is should be 12, I always seem to make a mistake when I enter these by
hand.

Ed

--- In spiderless@yahoogroups.com, "marcething" <marcething@...> wrote:
>
> Hi Ed ,
>
> Thanks for all the efforts , I really apreciate that !
> After making already quit a few telescopes , mainly Newtons and a 6 inch
Schiefspiegler , and now working on a 10" F/16 Dall-Kirkham , I would like to
have for my personal litle observatory THE ULTIMATE telescope .
> A fast enough system (F/7 to max F/12) and as close to "no aberations" as
possible .
> I was going for a Schuppmann 10 Inch F/10 , but now I'm more won for your idea
.
> Bigger diameter is still possible ( to fit in my litle observatory ) and I
thinck it's easier to make ( I do the optics myself , as we always did in our
group of ATM enthousiats , here at Urania observatory ) . Thats' Chriske's group
, for the insiders :-) .
>
>  1 litle question :
> Shouln't the diameter of surface 1 in 12inchf8 aplanat2.JPG be 12 inch in
stead of 6 ?
>
> Thanks  a lot in advance
>
> Marc
>

Hi Ed ,

Thanks for all the efforts , I really apreciate that !
After making already quit a few telescopes , mainly Newtons and a 6 inch
Schiefspiegler , and now working on a 10" F/16 Dall-Kirkham , I would like to
have for my personal litle observatory THE ULTIMATE telescope .
A fast enough system (F/7 to max F/12) and as close to "no aberations" as
possible .
I was going for a Schuppmann 10 Inch F/10 , but now I'm more won for your idea .
Bigger diameter is still possible ( to fit in my litle observatory ) and I
thinck it's easier to make ( I do the optics myself , as we always did in our
group of ATM enthousiats , here at Urania observatory ) . Thats' Chriske's group
, for the insiders :-) .

  1 litle question :
Shouln't the diameter of surface 1 in 12inchf8 aplanat2.JPG be 12 inch in stead
of 6 ?

Thanks  a lot in advance

Marc

Ed wrote:
> I uploaded a Zemax file for Marc called "12inchCHieff8bcomafree2.ZMX" a 12
inch f/8 aplanatic Chief design.
The thickness on surface 6 (the secondary): Is the system
still physically realizable?