Asteroid 2003 UV11 Again: Forget the Clouds. Open the Shutter!

Another damned fine sequence of 10 two-minute exposures of ref
asteroid, this time taken through clouds and satellite tracks and brown
marmorated stinkbugs with five feet in the grave.

http://www.primordial-light.com/asteroid2003uv11.html

Davoud

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm

On Oct 30, 7:02*am, Davoud wrote:
Another damned fine sequence of 10 two-minute exposures of ref
asteroid, this time taken through clouds and satellite tracks and brown
marmorated stinkbugs with five feet in the grave.

http://www.primordial-light.com/asteroid2003uv11.html

Davoud

Curious. Why is the asteroid track In the second image a wiggly line?
(for want of a suitable, technical term) I used Ctrl+ to enlarge the
image to confirm a repetitive sinusoidal behaviour. The stars don't
show any hint of short term drive inaccuracies and your AP mounting is
unlikely to exhibit such foibles anyway. Have you captured the
object's slow tumbling?

Chris.B:
Curious. Why is the asteroid track In the second image a wiggly line?
(for want of a suitable, technical term) I used Ctrl+ to enlarge the
image to confirm a repetitive sinusoidal behaviour. The stars don't
show any hint of short term drive inaccuracies and your AP mounting is
unlikely to exhibit such foibles anyway. Have you captured the
object's slow tumbling?

Chris L Peterson:
All mounts oscillate, which is why it is so common for asteroid tracks
to show some wiggle (or satellites, or airplanes). You don't see it with
stars because all it does is make them very slightly larger. However, in
this case, not having the original image to look at, I think the
apparent wiggle is just an aliasing effect. A diagonal line on a CCD
usually produces that, especially when the angle is shallow.

It's an aliasing effect exaggerated by two actions: 1) enlargement of a
small portion of the full frame. The telescope has a .73 reducer on it
that I was not inclined to remove. The full frame is 5° 19' x 3° 33',
while the enlarged portion is 2° across; 2) post-processing that was
necessary to reveal the track in a low-contrast image in which all 10
sub-frames were made through clouds of greater or lesser thickness.
Such processing was not needed for the first image because the sky was
clear for all 10 exposures in that image.

I have posted a flat-and-dark-reduced version of frame four, without
non-linear post processing, at
http://www.primordial-light.com/asteroid2003uv11.html#framefour.
Here, I believe, you will see less wiggle.

I took the liberty of performing significant post-processing on the 30
October UTC image because it was a non-repeating, now-or-never event
and my images are presented as informational, and are not intended to
be used for research purposes. When the 10 frames were aligned and
combined, before non-linear post-processing, the track was quite
difficult for the untrained eye to detect. The primary audience of
primordial-light.com consists of persons like myself with untrained
eyes. I wouldn't imagine that either Chris is a follower except
possibly when I post a link in SAA, but according to my e-mails I have
a few public-school science teachers and students, both near and far,
who visit my site.

Variations in the brightness of the tracks in the first image /may/
signal the asteroid's rotation, a planetary scientist told me. A few
members of my audience do have trained eyes.

How dare Chris L Peterson suggest that my mount oscillates! More likely
the astro-images that you see on line are aquiver due to the use of an
OS that was designed to display ASCII art rather than high-resolution
the high-resolution digital imaging

Davoud

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm

On Oct 30, 7:31*pm, Davoud wrote:
Chris.B:

Curious. Why is the asteroid track In the second image a wiggly line?
(for want of a suitable, technical term) I used Ctrl+ to enlarge the
image to confirm a repetitive sinusoidal behaviour. The stars don't
show any hint of short term drive inaccuracies and your AP mounting is
unlikely to exhibit such foibles anyway. Have you captured the
object's slow tumbling?

Chris L Peterson:

All mounts oscillate, which is why it is so common for asteroid tracks
to show some wiggle (or satellites, or airplanes). You don't see it with
stars because all it does is make them very slightly larger. However, in
this case, not having the original image to look at, I think the
apparent wiggle is just an aliasing effect. A diagonal line on a CCD
usually produces that, especially when the angle is shallow.

It's an aliasing effect exaggerated by two actions: 1) enlargement of a
small portion of the full frame. The telescope has a .73 reducer on it
that I was not inclined to remove. The full frame is 5 19' x 3 33',
while the enlarged portion is 2 across; 2) post-processing that was
necessary to reveal the track in a low-contrast image in which all 10
sub-frames were made through clouds of greater or lesser thickness.
Such processing was not needed for the first image because the sky was
clear for all 10 exposures in that image.

I have posted a flat-and-dark-reduced version of frame four, without
non-linear post processing, at
http://www.primordial-light.com/asteroid2003uv11.html#framefour.
Here, I believe, you will see less wiggle.

I took the liberty of performing significant post-processing on the 30
October UTC image because it was a non-repeating, now-or-never event
and my images are presented as informational, and are not intended to
be used for research purposes. When the 10 frames were aligned and
combined, before non-linear post-processing, the track was quite
difficult for the untrained eye to detect. The primary audience of
primordial-light.com consists of persons like myself with untrained
eyes. I wouldn't imagine that either Chris is a follower except
possibly when I post a link in SAA, but according to my e-mails I have
a few public-school science teachers and students, both near and far,
who visit my site.

Variations in the brightness of the tracks in the first image /may/
signal the asteroid's rotation, a planetary scientist told me. A few
members of my audience do have trained eyes.

How dare Chris L Peterson suggest that my mount oscillates! More likely
the astro-images that you see on line are aquiver due to the use of an
OS that was designed to display ASCII art rather than high-resolution
the high-resolution digital imaging

Davoud

I'd hate to argue with an expert but I find it hard to believe that
the "zigzags" from the youth of computing would appear in your images
in quite the same way. These deviations appears quite uncharacteristic
of poorly drawn diagonal lines from my own experience of having seen
probably hundreds of thousands of such artefacts over the early years
of home PCs.

All structures have a resonant frequency but having seen the images of
Davoud's equipment I would guess at far too high an F to be visible as
such perfectly repetitive "wiggles". One could not possibly excite the
mounting continuously to repeat exactly the same amplitude over such a
long period unless a drive motor was horrendously "noisy". Which I
seriously doubt at this level of sophistication. The AP just does not
lend itself to such excitement as it would rapidly damp out any such
vibration. Most top-heavy mountings on piers, set in or on concrete
foundations, would probably behave like compound pendulums with quite
long periods. Which again would not provide reproducible wiggles in
the same plane over any period of time without distorting the star
images as well.

Perhaps the effect really is an artefact of the sensor's limited
resolution and subsequent enlargement through cropping. Nevertheless,
keep up the good work. At least somebody here is doing something
worthwhile under the stars instead of fantasising about them in the
historical abstract.

BTW: You probably know that you can get free counters to go on
websites and blogs which give you very sophisticated data about your
visitors. A useful and reliable example is Statcounter. One cannot
rely on people emailing you privately to guess about visitor numbers
or their geography. ;-)

Chris.B:

BTW: You probably know that you can get free counters to go on
websites and blogs which give you very sophisticated data about your
visitors. A useful and reliable example is Statcounter. One cannot
rely on people emailing you privately to guess about visitor numbers
or their geography. ;-)

Primordial-light.com does not attract a huge following (and it wasn't
intended to). The total number of unique visitors may be seen at the
bottom of the main page: 5441 as this is written. The counter does not
count visits from my own computers.

In fact I have a fairly sophisticated counter that collects OS, IP
address, screen resolution, browser ID, unique vs repeat visitors, all
the stuff that can be gotten from a legal cookie. I pay nearly $100 per
year for this service, but it serves a number of web sites that I own
or control.

Recent visits have come from Denmark, the UK, Germany, Spain, Romania,
Canada, Sweden (friends, judging from the hometown), India, Japan,
Greece, Russia, Norway, Hong Kong, Mexico, Iran, India, Vietnam, New
Zealand, Australia, several U.S. university addresses (.edu), etc. As
you know, I cannot normally identify individuals with these stats, but
when a friend from a small town in Sweden visits it's pretty obvious
who it is. Ditto a few friends I have in other countries from which I
would not expect many hits.

OS: Mac OS X leads at 55%, All Windows varieties are next at 43%, then
Unix variants, older Mac OS, and unknowns comprise 2%.

Sundays and Tuesdays are the busiest days, Friday the slowest.

These stats don't count the Mac astronomy page, which has its own
counter.

Davoud

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm

Chris L Peterson wrote:

Turn off the tracking and make a star trail image. I've never done this,
with any mount, and not seen wiggle in the trails.

Of course you are right. But I have never done that, period. I'm not
inclined to swap cameras between 'scopes just now, but at my first
opportunity I will put a DSLR on the longer FL 'scope (150/1100mm refr.
vs. 106/530mm refr.), up the image scale a bit to exaggerate the
effect, and make an exposure or two with the drive turned off. I'll
post a link here. We'll see if I benefit comes from a 1600 lb pier
base, a relatively short 7" steel pier, and a semi-rural environment.
OK, we won't really see that, because I'm not going to move it all
someplace else for a comparison....

Davoud

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm

On Oct 30, 5:04*pm, Davoud wrote:
Chris L Peterson wrote:
Turn off the tracking and make a star trail image. I've never done this,
with any mount, and not seen wiggle in the trails.

Of course you are right. But I have never done that, period. I'm not
inclined to swap cameras between 'scopes just now, but at my first
opportunity I will put a DSLR on the longer FL 'scope (150/1100mm refr.
vs. 106/530mm refr.), up the image scale a bit to exaggerate the
effect, and make an exposure or two with the drive turned off. I'll
post a link here. We'll see if I benefit comes from a 1600 lb pier
base, a relatively short 7" steel pier, and a semi-rural environment.
OK, we won't really see that, because I'm not going to move it all
someplace else for a comparison....

Davoud

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm

Very neat pics, whatever about the wiggle...!
Marty

Marty wrote:
Very neat pics, whatever about the wiggle...!
Marty

Very kind of you to take time to say that. Thanks.

Davoud

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm

Chris L Peterson:

I do check your site semi-regularly. You are one of the few imagers
around still doing a lot of B&W imaging, which I generally prefer to
color.

Yes. Thank you. I like narrowband because it is quite immune to light
pollution and especially the light pollution gradients that are a pox
on my meager efforts. And I like monochrome because *I* think that I
see more subtle detail. Probably some limitation in my ability to
process color composites. Anyway, I also do color because monochrome
doesn't "sell" as well.

Davoud

--
I agree with almost everything that you have said and almost everything that
you will say in your entire life.

usenet *at* davidillig dawt cawm