New telescope technology

When do you think we'll see active optics filter down to amateurs? It
seems to be the most exciting thing happening in astronomy at the
moment.

On the subject a completely different technology, have there been any
initiatives to set up amateur telescope arrays? The proliferation of
broadband, telescope computer interfaces and incredibly powerful CPU's
for image processing could lead to some exciting results, I would
imagine. Do you think this would be feasible?

TopBanana wrote:

When do you think we'll see active optics filter down to amateurs? It
seems to be the most exciting thing happening in astronomy at the
moment.

Starlight Xpress already do one that is perfectly adequate for amateur
aperture scopes based on a tip-tilt corrector. You can also do offline
stack and add tricks for planetary images with a humble webcam.

On the subject a completely different technology, have there been any
initiatives to set up amateur telescope arrays? The proliferation of
broadband, telescope computer interfaces and incredibly powerful CPU's
for image processing could lead to some exciting results, I would
imagine. Do you think this would be feasible?

Sorry but optical telescope arrays are never going to be realistically
within the capabilities of amateur groups. The tolerances are far too
tight at optical wavelengths to do anything interesting without massive
engineering resources and temperature stabilised optical bunkers.

It might be possible for an amateur to repicate the Michelson & Pease
experiment to measure stellar diamters of the brightest stars. But even
that is doubtful - later and without Michelson (one the greatest
experimentalists of the last century), Pease couldn't make the kit work.

Regards,
Martin Brown

Martin Brown wrote:
TopBanana wrote:

When do you think we'll see active optics filter down to amateurs? It
seems to be the most exciting thing happening in astronomy at the
moment.

/comment
The words "active optics" are actually used for devices that do modify
the optics to correct for low order, high amplitude, low frequency
optical errors (defocus, piston, astigmatism and spherical to name the
most frequent ones). You might have meant "adaptive optics" though, by
which term they mean the devices that do correct low amplitude, high
frequency optical errors due to atmospherics at some point of the
optical path
/end comment


Starlight Xpress already do one that is perfectly adequate for amateur
aperture scopes based on a tip-tilt corrector. You can also do offline
stack and add tricks for planetary images with a humble webcam.

That's woefully inadequate if the proper menaing of the term "adaptive
optics" is accepted. It is not even fast enough for correcting tip/tilt
errors induced by the atmosphere let alone all other terms...

BTW, SBIG started making the same device 10 years ago. Once upon a time
there was a true tip/tilt correction device available to the amateurs
(the AO-2) but alas this is no more.

Andrea T.

Andrea T.

"TopBanana" wrote in message
...
When do you think we'll see active optics filter down to amateurs? It
seems to be the most exciting thing happening in astronomy at the
moment.

On the subject a completely different technology, have there been any
initiatives to set up amateur telescope arrays? The proliferation of
broadband, telescope computer interfaces and incredibly powerful CPU's
for image processing could lead to some exciting results, I would
imagine. Do you think this would be feasible?
The problem is the amount of light involved. There are lots of different
'levels' of AO. The lowest, is what is known as 'tip/tilt' correction, and
this has been offered by a number of companies (SBIG, with their AO7,
Starlight Express with their AO unit at present, and a couple of other
units in the past). Now these run a 'borderline', on whether they are
really AO, because the actual light for correction, comes sufficiently far
away from the target star, that it is arguable that they function more in
correcting faults in the mount, than in actually correcting for
atmospheric effects. However used on reasonably small image scales, with
high update rates (10Hz), the results do show very significant
improvement, and people are obtaining fwhm figures far better than with
simply guided scopes, especially when the seeing is good.

Going further than this though, runs into the problem of light. To acheive
correction for some of the focus defects, requires update rates increase
further, and that the correction light is coming from a spot very close to
the imaging target. Unfortunately few targets have a bright star this
close, and this is why observatories use an artificial sodium guide star
(there is a layer in the upper atmosphere, which a sodium laser will
stimulate to produce a bright 'dot' - since this is very high in the
atmosphere, the light distortions seen on an image of this, correspond
closely with the distortions being seen from the astronomical object, and
can be used for the basis of correction). Now even with this laser, the
aperture needed to get enough light for good corrections, is large. It is
typically calculated that a minimum of 1m aperture is needed for the
wavefront sensors to get enough light to work.
The problems of getting licensing to project a sodium laser bright enough
for this, the costs of the actuated corrector, and a scope large enough
for all this to work, take it beyond anything that is likely to happen in
many places. I wouldn't say there will never be such an amateur system,
but it is not going to be something available to the normal backyard
amateur.

However many amateurs do use the tip/tilt correctors for deep sky imaging
with success, and on planetary imaging, there has been the development of
'pseudo AO'. With this, perhaps 300 images are taken in rapid succession,
and then processing software is used to perform first alignment, and then
statistical wavefront analyses, on these images. This produces an effect
very similar to AO, but done 'after the event'. Many of the recently
published amateur planetary images, happily 'beat' the best professional
images from only a few years ago, using this technique, and this has the
big advantage of being cheap (only needing a high speed imager, and a lot
of processing power).

On 'multiple scopes', many published images, are the result of combining
images taken in different parts of the world, _but_ these do not bring the
advantages you are thinking of in resolution. The resolution advantage
from multiple seperate scopes, only appears, when you resolve wavefront
level information in the images (no simple CCD sensor does this), and the
images are combined to accuracies at this level, or the light from two
sources is brought together down a light path allowing the same level of
control. This is why the professional successes at doing this on longer
baselines, have all been at much lower frequencies, where such timing is
possible. On shorter baselines, visible systems, require scopes where the
lightpath can be maintained to this level of accuracy. No amateur system
could do this. Even the professional systems are only just moving into the
visible light area doing this.

Some amateur radio astronomers _have_ done work at their lower
frequencies.

Best Wishes

"Martin Brown" wrote in message
...
| TopBanana wrote:
| On the subject a completely different technology, have there been
any
| initiatives to set up amateur telescope arrays? The proliferation
of
| broadband, telescope computer interfaces and incredibly powerful
CPU's
| for image processing could lead to some exciting results, I would
| imagine. Do you think this would be feasible?
|
| Sorry but optical telescope arrays are never going to be realistically
| within the capabilities of amateur groups. ...

Hmmm. 'Never say "never"'. Optical arrays became possible due to the
vast increases in (not too expensive) processing power. My first PC had
30 Mb disk and about 0.3 megahertz cpu cycle time. Today, 17 years
later, for about the same price as that was, I can buy one with 300
gigabyte & 1 gigahertz - 10,000 fold & 3000 fold respectively.

OK, amateur telescope arrays will not happen this week, but who knows
what will be achievable in 1000 years time.
--
Laury

Originally Posted by

BTW, SBIG started making the same device 10 years ago. Once upon a time
there was a true tip/tilt correction device available to the amateurs
(the AO-2) but alas this is no more.

Andrea T.

....and if I recall using a tip/tilt mirror. I understand from SX at Astrofest that SBIG are considering a tip/tilt 'window' too.

Nytecam

Laury wrote:

"Martin Brown" wrote in message
...
| TopBanana wrote:
| On the subject a completely different technology, have there been
any
| initiatives to set up amateur telescope arrays? The proliferation
of
| broadband, telescope computer interfaces and incredibly powerful
CPU's
| for image processing could lead to some exciting results, I would
| imagine. Do you think this would be feasible?
|
| Sorry but optical telescope arrays are never going to be realistically
| within the capabilities of amateur groups. ...

Hmmm. 'Never say "never"'. Optical arrays became possible due to the
vast increases in (not too expensive) processing power.

That is only part of the tale. Optical arrays with phase compensation
are only just marginally possible at a hard engineering level. Steel
behaves like jelly at the tolerances needed.

Even today replicating the original Michelson & Pease experiment of the
1920's is well beyond the capabilities amateurs.

In the radio bands interferoemtry is well within amateur capabilities.

My first PC had
30 Mb disk and about 0.3 megahertz cpu cycle time.

By the time PCs had 30MB hard disks the clock speed was 4.77MHz or
above, but with only tiny amounts of expensive memory fitted.

Today, 17 years
later, for about the same price as that was, I can buy one with 300
gigabyte & 1 gigahertz - 10,000 fold & 3000 fold respectively.

OK, amateur telescope arrays will not happen this week, but who knows
what will be achievable in 1000 years time.

Even the most advanced designs and composite materials are still subject
to the laws of physics. To make interferometry work in a phased array
you have to hold all relative path lengths of the optical components
constant to fraction of a wavelength.

It will never be easy or cheap to do this on Earth.

Regards,
Martin Brown

"Martin Brown" wrote in message
...
Laury wrote:

"Martin Brown" wrote in message
...
| TopBanana wrote:
| On the subject a completely different technology, have there been
any
| initiatives to set up amateur telescope arrays? The proliferation
of
| broadband, telescope computer interfaces and incredibly powerful
CPU's
| for image processing could lead to some exciting results, I would
| imagine. Do you think this would be feasible?
|
| Sorry but optical telescope arrays are never going to be
realistically
| within the capabilities of amateur groups. ...

Hmmm. 'Never say "never"'. Optical arrays became possible due to the
vast increases in (not too expensive) processing power.

That is only part of the tale. Optical arrays with phase compensation
are only just marginally possible at a hard engineering level. Steel
behaves like jelly at the tolerances needed.

Even today replicating the original Michelson & Pease experiment of the
1920's is well beyond the capabilities amateurs.

In the radio bands interferoemtry is well within amateur capabilities.

My first PC had
30 Mb disk and about 0.3 megahertz cpu cycle time.

By the time PCs had 30MB hard disks the clock speed was 4.77MHz or
above, but with only tiny amounts of expensive memory fitted.

Today, 17 years
later, for about the same price as that was, I can buy one with 300
gigabyte & 1 gigahertz - 10,000 fold & 3000 fold respectively.

OK, amateur telescope arrays will not happen this week, but who knows
what will be achievable in 1000 years time.

Even the most advanced designs and composite materials are still subject
to the laws of physics. To make interferometry work in a phased array
you have to hold all relative path lengths of the optical components
constant to fraction of a wavelength.

It will never be easy or cheap to do this on Earth.
The one 'possibility', would be if a new sensor design was created, that
stored the phase/wavelength for every photon at every pixel. Nothing even
'on the horizon' that can do this simultaneously, but 'never say
never'!...

Best Wishes

"Martin Brown" wrote in message
...
| Laury wrote:
|
| Hmmm. 'Never say "never"'. Optical arrays became possible due to
the
| vast increases in (not too expensive) processing power.
|
| That is only part of the tale. Optical arrays with phase compensation
| are only just marginally possible at a hard engineering level. Steel
| behaves like jelly at the tolerances needed.

That's true. My understanding was that the engineering was ready some
while back and the pioneers at Cambridge were waiting for the processing
capability.
|
| Even today replicating the original Michelson & Pease experiment of
the
| 1920's is well beyond the capabilities amateurs.

A bit too expensive! Otherwise I'd have done it for myself by now, just
to satisfy my scepticism about speed of light being constant. That
device was also the first to be used for astromomical optical
interferometry to determine the motion of Capella.
|
| My first PC had
| 30 Mb disk and about 0.3 megahertz cpu cycle time.
|
| By the time PCs had 30MB hard disks the clock speed was 4.77MHz or
| above, but with only tiny amounts of expensive memory fitted.

My mistake. In those days, I used 'multiply' time as a way of comparing
and had that in mind. The old girl still works, and I never did fill
that disk! It had an 8080 chip, and it 640Kb memory. To me then, that
wasn't tiny.

A far cry from my first micro, the 8008 with 2kb ROM, 2kb RAM & 2*256K
hard formatted 8" floppies which were truluy floppy.
|
| Today, 17 years
| later, for about the same price as that was, I can buy one with 300
| gigabyte & 1 gigahertz - 10,000 fold & 3000 fold respectively.
|
| OK, amateur telescope arrays will not happen this week, but who
knows
| what will be achievable in 1000 years time.
|
| Even the most advanced designs and composite materials are still
subject
| to the laws of physics. To make interferometry work in a phased array

| you have to hold all relative path lengths of the optical components
| constant to fraction of a wavelength.
|
| It will never be easy or cheap to do this on Earth.

Perhaps I'm wrong, but I thought rather than trying to keep the
distances constant, the trick is to measure the distances and
incorporate that into the calculation. I haven't been able to find a
reference for that.

Anyway, given that the current number of usable professional instruments
is something like 20, it'll be a long time in the future before amateurs
will be able to use optical interferometry.
--
Laury

On Sun, 26 Feb 2006 13:34:27 +0000 (UTC), "Laury"
wrote:

"Martin Brown" wrote in message
...
| Laury wrote:
| Today, 17 years
| later, for about the same price as that was, I can buy one with 300
| gigabyte & 1 gigahertz - 10,000 fold & 3000 fold respectively.

.... and they still only go about twice as fast :-)

Jim