CCD imaging resolution of "large" atm scopes?

Hi all...

Was pondering my future retirement dreams and visions of a large telescope and
observatory in some reasonably dark location in the southeast...

By large I mean something in the 24 to 40 inch class....

Now it is apparent from some of the CCD pics amatuers have taken of the planets
with more modest size scopes that they are able to reach darn close to the
theoretical limits of resolution and contrast...ie in the .5 to .25 arc second
range....

Butttt....these result from several things.....first modest size scopes ( 8 to
16 inches).....secondly...they can image for hours, days, even weeks to get a
good planetary shot.....and thirdly....they take many FAST images where they
"freeze" the seeing, pick the best looking of some fraction of them, and then
combine that fraction for a final image....

Back to the large dream scope....lets say Im not really interested doing the
planet imaging thing....Im more interested in CCD photometry, asteroid
searches/astrometry, nova patrol, faint comets etc etc......now this kind of
work (if your looking to be at all efficient about it) requires long exposures
per frame...and the ability to use the majority of the frames taken....so now
in addition to having a scope 2 to 5 times as large as what the planetary
imagers use we also have the exact opposite in terms of exposure duration and
required fraction of usable frames....

Sorry, getting to my point here....now I find it hard to imagine if I built a
40 inch scope and it was located somewhere near sea level in the southeast USA,
that I would get anything remotely close to .1 arc second star images on CCD
frames ranging anywhere from 30 seconds to many minute exposures (and lets
assume seeing is our only problem....other problems such as tracking, scope
vibrations, tube currents, overly warm observatory etc etc have been
eliminated)....

Now, my WAG is that such large scopes probably dont exceed .5 arc seconds
imaging give or take the majority of the time...if that good...

Anybody here with relatable experience or other WAGS?

take care

Blll

On 19 Mar 2004 14:52:53 GMT, (BllFs6) wrote:

Sorry, getting to my point here....now I find it hard to imagine if I built a
40 inch scope and it was located somewhere near sea level in the southeast USA,
that I would get anything remotely close to .1 arc second star images on CCD
frames ranging anywhere from 30 seconds to many minute exposures (and lets
assume seeing is our only problem....other problems such as tracking, scope
vibrations, tube currents, overly warm observatory etc etc have been
eliminated)....

Now, my WAG is that such large scopes probably dont exceed .5 arc seconds
imaging give or take the majority of the time...if that good...

I don't believe I've ever seen a deep astroimage with 0.5" resolution. At very
good sites, with good equipment (see, for example, what Adam Block is getting at
Kitt Peak with a 20" RCOS on a Paramount- basically as good a setup as you can
get) 2" is common, rarely pushing down towards 1". That's the best any scope, of
any size, can do through the atmosphere (without using adaptive optics, which
doesn't exist for amateurs except the for the trick of selecting from many
frames).

Also, if you want to do deep sky imaging, you'd be better off retiring to the
southwest than the southeast g.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

"BllFs6" wrote in message
...
Hi all...

Was pondering my future retirement dreams and visions of a large telescope
and
observatory in some reasonably dark location in the southeast...

By large I mean something in the 24 to 40 inch class....

Now it is apparent from some of the CCD pics amatuers have taken of the
planets
with more modest size scopes that they are able to reach darn close to the
theoretical limits of resolution and contrast...ie in the .5 to .25 arc
second
range....


Yep, the guys a dreamer. Dream on!


"BllFs6" wrote in message
...
Funny how no one ever asks them directly inspite of all the smoke and
mirrors. People want answers from the hip,
not the sky!


Well....Id say tombos answers come from a stinky body part that is
generally
covered by 2 layers of clothing and is often massaged with toilet
paper....(and
hint...it aint the hip!)

Blll

I said people! Not the likes of you, whatever you are. Obviously your name
is foreign around here which
makes you a lurker, a troll, a nobody, and various other words that take
some form of the 7 words you can't say on
the radio or TV!

Chris L Peterson wrote in message . ..
On 19 Mar 2004 14:52:53 GMT, (BllFs6) wrote:

Sorry, getting to my point here....now I find it hard to imagine if I built a
40 inch scope and it was located somewhere near sea level in the southeast USA,
that I would get anything remotely close to .1 arc second star images on CCD
frames ranging anywhere from 30 seconds to many minute exposures (and lets
assume seeing is our only problem....other problems such as tracking, scope
vibrations, tube currents, overly warm observatory etc etc have been
eliminated)....

Now, my WAG is that such large scopes probably dont exceed .5 arc seconds
imaging give or take the majority of the time...if that good...

I don't believe I've ever seen a deep astroimage with 0.5" resolution. At very
good sites, with good equipment (see, for example, what Adam Block is getting at
Kitt Peak with a 20" RCOS on a Paramount- basically as good a setup as you can
get) 2" is common, rarely pushing down towards 1". That's the best any scope, of
any size, can do through the atmosphere (without using adaptive optics, which
doesn't exist for amateurs except the for the trick of selecting from many
frames).

Also, if you want to do deep sky imaging, you'd be better off retiring to the
southwest than the southeast g.

Heh!

What many (apparently) don't realize is the seeing conditions and arcsecond
resolution at many of the professional observatories aren't as "good" as one
might imagine.

An interesting document that describes site selection and tests (with examples)
can be found he

snap.lbl.gov/pubdocs/Seeing_at_Observatories_v3.0.doc

"LBL" = "Lawrence Berkeley Labs"

A number of other fascinating articles can be found he

http://www.llnl.gov/str/Indexlist.html

such as:

http://www.llnl.gov/str/Olivier.html

concerning laser guide stars for adaptive optics.

"LLNL" = "Lawrence Livermore National Laboratories" (the nuke lab :-)

LLNL was instrumental setting up many observatories with adaptive optics using
technology originally developed for SDI ("Star Wars").

Chris L Peterson wrote in message . ..


I don't believe I've ever seen a deep astroimage with 0.5" resolution.
At very good sites, with good equipment (see, for example, what Adam
Block is getting at Kitt Peak with a 20" RCOS on a Paramount-
basically as good a setup as you can get) 2" is common, rarely
pushing down towards 1".


Soon Adam will have the possibility to use 32" RC from RCOS with
ARIES'
ION-BEAM figured optics with quality of RMS 0.015 wave. This should
improve
his photos significantly. Star images will be tighter.


Valery Deryuzhin.
ARIES.

I don't believe I've ever seen a deep astroimage with 0.5" resolution.
At very good sites, with good equipment (see, for example, what Adam
Block is getting at Kitt Peak with a 20" RCOS on a Paramount-
basically as good a setup as you can get) 2" is common, rarely
pushing down towards 1".


In order to get down to 1 arc second, you will need more than a good mount. I
found that in places of best seeing, where the full resoution of my 10" scope
could be used (Florida Keys), the star image would be almost perfect at the
highest power (900 to 1000X), but it would wander in a random manner as much a
3 arc seconds in a 5 second time period due to low frequency atmospheric
disturbances. No mount can counter this type of motion. In order to achieve
maximum resolution you will need to use an active device such as the SBIG AO7
unit. I believe Adam Block uses such a device in his images.

In my case, I was able to achieve 1.2 arc seconds FWHM with the 10" Mak in the
Keys by limiting my exposure time to 3 seconds and stacking a large number of
exposures.

Roland Christen

On 19 Mar 2004 13:57:30 -0800, (ValeryD) wrote:

Soon Adam will have the possibility to use 32" RC from RCOS with
ARIES'
ION-BEAM figured optics with quality of RMS 0.015 wave. This should
improve
his photos significantly. Star images will be tighter.

We'll see. I think his star images are essentially limited by his seeing, not
his optics. I really doubt that the new telescope will produce significantly (or
even noticeably) better star images.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

(Thad Floryan) wrote in message . com...
Chris L Peterson wrote in message . ..
On 19 Mar 2004 14:52:53 GMT, (BllFs6) wrote:

Sorry, getting to my point here....now I find it hard to imagine if I built a
40 inch scope and it was located somewhere near sea level in the southeast USA,
that I would get anything remotely close to .1 arc second star images on CCD
frames ranging anywhere from 30 seconds to many minute exposures (and lets
assume seeing is our only problem....other problems such as tracking, scope
vibrations, tube currents, overly warm observatory etc etc have been
eliminated)....

Now, my WAG is that such large scopes probably dont exceed .5 arc seconds
imaging give or take the majority of the time...if that good...

I don't believe I've ever seen a deep astroimage with 0.5" resolution. At very
good sites, with good equipment (see, for example, what Adam Block is getting at
Kitt Peak with a 20" RCOS on a Paramount- basically as good a setup as you can
get) 2" is common, rarely pushing down towards 1". That's the best any scope, of
any size, can do through the atmosphere (without using adaptive optics, which
doesn't exist for amateurs except the for the trick of selecting from many
frames).

Also, if you want to do deep sky imaging, you'd be better off retiring to the
southwest than the southeast g.

Heh!

What many (apparently) don't realize is the seeing conditions and arcsecond
resolution at many of the professional observatories aren't as "good" as one
might imagine.

An interesting document that describes site selection and tests (with examples)
can be found he

snap.lbl.gov/pubdocs/Seeing_at_Observatories_v3.0.doc

"LBL" = "Lawrence Berkeley Labs"

A number of other fascinating articles can be found he

http://www.llnl.gov/str/Indexlist.html

such as:

http://www.llnl.gov/str/Olivier.html

concerning laser guide stars for adaptive optics.

"LLNL" = "Lawrence Livermore National Laboratories" (the nuke lab :-)

LLNL was instrumental setting up many observatories with adaptive optics using
technology originally developed for SDI ("Star Wars").

Thanks for the links, Thad. I wasn't aware of the LBL public
documents site before, but it looks like there is a lot of interesting
stuff there.

Clear skies.

Erik
socalsw

On 19 Mar 2004 12:47:01 -0800, (Thad Floryan) wrote:

What many (apparently) don't realize is the seeing conditions and arcsecond
resolution at many of the professional observatories aren't as "good" as one
might imagine.

And they are remarkably variable. A few sites in the Tucson area have some of
the best seeing in the continental U.S. A few others, just a few miles from
those, are much worse. Local conditions are very important.

Of course, the southeast is generally regarded as having quite good seeing. But
it also generally has poor transparency, making it less than ideal for deep sky
imaging, where the improved S/N from clear, dark skies is valuable.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote in message . ..
On 19 Mar 2004 13:57:30 -0800, (ValeryD) wrote:

Soon Adam will have the possibility to use 32" RC from RCOS with
ARIES'
ION-BEAM figured optics with quality of RMS 0.015 wave. This should
improve
his photos significantly. Star images will be tighter.

We'll see. I think his star images are essentially limited by his seeing, not
his optics. I really doubt that the new telescope will produce significantly (or
even noticeably) better star images.


It will. If you compare images, taken with large scopes and smaller ones,
you will see, that star images are tighter on photos with larger telescopes.
This is due to lesser influence of diffraction on apertures in large instruments.


Valery Deryuzhin.