Best tube material for a planetary Newtonian?

On Monday, 2 February 2015 16:23:45 UTC+1, Lord Androcles wrote:

I'd still be very interested to hear from anybody who has direct experience
of buying a long, CF tubed Harley-Davidson.

I was misquoted.

Imitation being the sincerest form of flattery...?

"Chris.B" wrote in message
...

On Monday, 2 February 2015 16:23:45 UTC+1, Lord Androcles wrote:

I'd still be very interested to hear from anybody who has direct
experience
of buying a long, CF tubed Harley-Davidson.

I was misquoted.

Imitation being the sincerest form of flattery...?

================================================== ===
Definition of chain-jerking is "flattery"? I thought it was "teasing", in
this case by parody.
The part that really amused me was "I am determined to use my vintage
driven equatorial" which says in effect you are not ready for change.
Analogously, adding an engine to an old bicycle gives you this,
http://www.cars-show.org/wp-content/...orcycle-05.jpg
and not this:
http://www.motorcycledaily.com/wp-co...2middle1-3.jpg
You'll need a wrench for the first and a fibreglass moulding shop for the
second.
CF tubes are not bolted or welded together, instead they are wrapped. If you
mix the old with the new you'll end up with a disaster.
What you need for planetary viewing is a motor driven balanced Dob with the
azimuth and altitude controlled by a computer, then the weight issue is less
important, unless you want to transport it to a dark park somewhere on the
bed of a truck. And if you are going to mount a camera then the height of
the eyepiece doesn't matter either. I use my phone as the camera for my
computer, so my image can be as large as my monitor or appear as a window
within it. Squinting through an eyepiece out in the cold seems masochistic
to me, the telescope itself is technology used to aid viewing, so is
electronics.

-- The Reverend Lord Androcles.
Je suis Charlie.

"Chris.B" wrote:
On Monday, 2 February 2015 01:23:29 UTC+1, Sketcher wrote:
For some, cost and ease of construction can be important factors. In
which case a Dobsonian with a wood tube might be a reasonable choice.
With practice (especially if one has no alternative) one's arms and
hands eventually learn to make the necessary adjustments (even at planetary
magnifications) with hardly any conscious effort. I have a 10-inch
Newtonian with a long, hexagonal, cedar tube - a Dobsonian, that's been
used (among other uses) as a planetary telescope. One of the odd things
about this scope is that it has four instead of the usual three
collimation screws. There was insufficient space within the OTA for
three screws 120 degrees apart. I have to be careful when collimating
to not induce astigmatism! On the other hand, once the scope is
collimated the four screws effectively 'lock' the collimation in place.

The long, solid tube extending 18 inches beyond the focuser makes the
optics impervious to dew and frost and helps shield the tube's interior
from the observer's body heat.

Sketcher,
To sketch is to see.

Thank you all for your responses. 'Solid' aluminium tubes may have some
advantages but quickly become heavy and unwieldy in longer [suitably
stiff wall thickness] lengths.

So far I have tried cardboard form tubes but found them much too heavy
for comfort. I ended up with an ultra-lightweight, aluminium, twin beam
effort. But still have some local stiffness problems to overcome.
Hopefully without increasing the moment too much for comfortable mounting.

CF seemed to offer the lightness I desperately need for my 10" F:8 optics
but is still very costly. Not something I want to experiment with unless
it stood [literally] head and shoulders over traditional alternatives.

I am determined to use my vintage, driven equatorial, if possible, before
giving up and building a Dobsonian. I have built Dobs up to 12" and they
do handle very nicely. But, they just don't offer the freedom to take
extra-focal 'snaps' with a digital compact camera. Nor webcam video frame
stacking which I want to try.

I've also built tracking platforms before but with the eyepiece already
7' off the ground I have serious reservations about increased height.

I'd still be very interested to hear from anybody who has direct
experience of using a long, CF tubed Newt.

Thanks

Are you going to use a low profile focuser and smaller secondary?

On Tuesday, February 3, 2015 at 12:51:42 PM UTC-5, Chris.B wrote:

snip

Your telescope will/will not provide for rotating the focuser to comfortable/safe viewing position?

There are good reasons why we don't generally see 10" f/8 Newts anymore.

Not trying to be "antagonistic" here, you understand.

On Tuesday, February 3, 2015 at 12:51:42 PM UTC-5, Chris.B wrote:

snip

Quasi-equatorial, single motion for tracking, should work for planets, especially at high latitudes:

http://home.freeuk.com/m.gavin/solatrax.htm

There is no rule that a telescope can't have more than one mount.

On Friday, 6 February 2015 12:26:43 UTC+1, wrote:

There are good reasons why we don't generally see 10" f/8 Newts anymore.

The lack does not hint at anything except a demand for portability, extreme compactness and ease of use. Few can afford, or have the space, for a fixed observatory. So the telescope must usually be brought out from a heated room and used just outside the home. The SCT may be the popular choice but it offers the lowest planetary performance for visual use. The reasons are numerous. Thermal and cooling issues in a sealed tube, inferior optics and mechanics, large secondary obstruction and relatively poor mountings and drives.

On Saturday, February 7, 2015 at 12:01:23 PM UTC-5, Chris.B wrote:
On Friday, 6 February 2015 12:26:43 UTC+1, wsne... wrote:

There are good reasons why we don't generally see 10" f/8 Newts anymore.

The lack does not hint at anything except a demand for portability,

A good reason.

extreme compactness

A good reason.

and ease of use.

A VERY good reason

The SCT may be the popular choice but it offers the lowest planetary
performance for visual use.

That depends on the SCT. Most are good. A few are bad. Most are very useful to their owners.

Your experience with the ongoing construction of a 10" f/8 compares very poorly with my experience building a scope with a more practical focal ratio.

My scope took about two months from the decision to build to first light, and worked perfectly "out-of-the-box," needing no rebuilds, mods or upgrades after completion.

Whereas yours has been a "work in progress" for YEARS.

I would hate to think that newbies will view your trials and tribulations as the norm.

On Monday, 9 February 2015 15:38:43 UTC+1, wrote:

Your experience with the ongoing construction of a 10" f/8 compares very poorly with my experience building a scope with a more practical focal ratio.

My scope took about two months from the decision to build to first light, and worked perfectly "out-of-the-box," needing no rebuilds, mods or upgrades after completion.

Whereas yours has been a "work in progress" for YEARS.

I would hate to think that newbies will view your trials and tribulations as the norm.

Each to their own. The journey's the thing. Not [so much] reaching the destination. For that would mean finding something new and interesting to do next. Better an ATM project which suits my tastes perfectly than an irritating commercial thing handicapped down to a price.

Telescope making was always my hobby in preference to astronomy. This may well have had a lot to do with the very poor illustrations in library books on astronomy when I was young. Whereas ATM1, 2 and Advanced were absolutely packed full of fascinating stuff. There were other books in the library in those days of course. Knowledge meant a bike ride to the reference or lending library.

I spent many happy hours watching my various mirror making machines do their stuff. It would have been far easier and probably better to have worked entirely by hand but that wasn't the point. Designing and finding the parts to build machines and telescopes from everyday objects and materials was a complete hobby in itself and has lasted me a lifetime.

I've spent most of my life searching for an incredible range of unlikely parts, materials and tools to do a job perfectly and usually with minimum expenditure. In the process I taught myself metalwork, woodwork, optics, photography, spectroscopy, precision measurement, materials choice and handling, GRP, machining, mechanics, glass cutting, electrical work, soldering, brazing, welding, tool use and safety, calculation, geometry, trigonometry, computer programming, optical text book conversion to Basic... even human relations...

The list really is endless and mostly down to ATM. With the knowledge accumulated I obtained employment, built homes, cars, furniture, bicycles, models, clocks and audio equipment etc, etc.. These days I blog and I write to try and amuse and gently educate others. As just one of literally hundreds of different hobbies and interests over the decades ATM has filled countless hours. Doing so as I wish and full of the pleasure of quiet, personal accomplishment. Not bending to some other person's timetable or delivering to their expectations.

The worst thing which could have happened to me was being born rich. Instead of which I enriched my own life by doing or studying the unlikely in my own modest way. Happiness is finding a huge range of things interesting and even amusing. When TV and the media fail to amuse it is a lifesaver to be able to amuse yourself constructively. The spoilt offspring of the rich fill the headlines with their drug abuse, alcoholism and infantile tantrums. I filled my modest life with knowledge and made all sorts of things. Can you say the same? ;ø))

On Monday, February 9, 2015 at 11:55:48 AM UTC-5, Chris.B wrote:
On Monday, 9 February 2015 15:38:43 UTC+1, wsne... wrote:

Your experience with the ongoing construction of a 10" f/8 compares very poorly with my experience building a scope with a more practical focal ratio.

My scope took about two months from the decision to build to first light, and worked perfectly "out-of-the-box," needing no rebuilds, mods or upgrades after completion.

Whereas yours has been a "work in progress" for YEARS.

I would hate to think that newbies will view your trials and tribulations as the norm.

Better an ATM project which suits my tastes perfectly than an irritating
commercial thing handicapped down to a price.

Now there's a strawman argument! Of course it is also possible to buy an "irritating commercial thing" and then improve upon it.

Telescope making was always my hobby in preference to astronomy.

I prefer to keep a balance between the two.

The worst thing which could have happened to me was being born rich.

I hate to break this to you, but compared to the average world citizen you probably WERE born rich.

The spoilt offspring of the rich fill the headlines with their drug abuse,
alcoholism and infantile tantrums.

For example, the Third Earl?

I filled my modest life with knowledge and made all sorts of things. Can you
say the same?

I built a equatorial pipe mount for my Department Store Telescope. Worked great.

On Monday, 9 February 2015 20:20:26 UTC+1, wrote:

I hate to break this to you, but compared to the average world citizen you probably WERE born rich.

A meaningless generalization. My only real wealth was being born with burning curiosity and an ability to seek more information. Applying that information in my countless interests and projects enjoyed a snowball effect. Further enhancing every other area of interest and activity.

I see the modestly constructive use of my allotted time on this earth as a priceless gift. Countless others hide from the real truth of our ephemeral existence with bowed heads. Grovelling on their knees in fear of a vengeful ogre. Others, so desperate to improve their meaningless existence, commit crimes and enslave others for cheap, personal gain. There is no victim-less crime. Others literally scramble over tottering, pyramidal humanity in their rush for fame and fortune at any cost. Countless others now seek to lose themselves in the virtual world. Or exchange simple reality for abuse and self abuse.

We are the sum of everybody who has ever lived. Many confuse those who are best remembered as ideals for their own pitiful existence. Or seek to be remembered themselves for the worst possible reasons. The despotic philanthropist in his sprawling, gilded palace, who gives away his evaded taxation and the sweated toils of his slaves, is really no better than a petty crook and public wife beater. He just prefers to mask his crimes against humanity from himself with lavish decoration of his nest and unearned nest egg.

Do no harm, treat others as you would yourself and tread lightly on this, our only earth. These are all an excellent guide to gently pass on our personal existence to the next generation. All empires eventually fall as if they never really existed. They should really be seen as failed follies to pointless, personal ambition. Their only glory lies in their hard lessons for mankind's organisation and developing real sanctions for evildoing. The blind exploitation of resources and humanity are always limited and always result in exactly the same mistakes.

While others try to force themselves on an unwilling world I build myself telescopes. Slowly and Badly? Perhaps. But who in the grand scheme of things is the judge? Who is measuring their own time against my own? As if winning will get them to the end of their lives a second earlier? ;ø))