Date   

Re: First Light with my new Mach1

Wiggins, Rick
 

Hi Hunter,
That is an impressive image. Great details and good color. I am
really impressed that this was done with a DSLR.
Thanks, Rick

--- In ap-gto@..., "hewholooks" <hewholooks@...> wrote:

Set up the new mount yesterday afternoon and it wasn't supposed to
be
clear - but it was. After a slight learning curve, I got these
shots
of the Leo Trio - first 5 images in this gallery (really just one
image
in 5 ways).

Thanks for looking.

http://hwilson.zenfolio.com/p781396937

Hunter


Re: Autoguider correction frequency

Wiggins, Rick
 

Hi Hunter,
I have a few questions if you don't mind.
Maybe I am having a senior moment, but what is PHD?
Antoher question or confirmation is "Is aggressiveness set to 60 "
equivalent to 60% correction or what would be "6" in CCDSoft or
Maxim?
Finally a comment or my misunderstanding. I would think that for a
guider (with the setttings as described) not to make any corrections
for 5 minutes implies two things; first that the worm drive has
virtually no periodic error (meaning less then 0.05 arc sec), and
second, that the sky has virtually no turbulance.
If my guider did not make any corrections for 5 minutes, I would
expect that something was wrong.

Here are some of my settings with an AP155 on a AP1200 mount, guided
with a Tak FS60C and ST :
Periodic error = less than 0.8 arc secs PtP
Guider settings: Min error=0.04 pixels Max error=0.10 pixels, rate =
1x, aggressiveness 5 (=50%), exposure 2 secs
With these settings I am getting RMS guider errors of approximately
0.08 pixels and instantaneous errors not usually exceeding 0.2 pixels
This is on average seeing evenings. Even with these readings, I am
getting real corrections on mnay of the cycles.

Maybe this information is of some use to you and others.
Thanks, Rick



--- In ap-gto@..., "hewholooks" <hewholooks@...> wrote:

Gedas,

Right now, as I write, I am guiding with my new Mach1 (Thank you
Roland - you are my hero) using PHD. I have guide rate on the
mount
set to 0.5 and PHD RA agress set to 60. I have never seen
anything
like this. PHD is on vacation - maybe, MAYBE one correction every
5
or 10 minutes and that's only 0.3 pixels (1.3 arcsec).

I am in awe. I can't wait to image at 1500mm (tonight it's at 780
with the 130 refractor).

The Mach1 is everything they say it is.

Hunter

--- In ap-gto@..., "Gedas" <w8bya@> wrote:

Correct, it's the orion AG'er.

Gedas
http://gedas.cc
http://www.w8bya.com



----- Original Message -----
From: "hewholooks" <hewholooks@>
To: <ap-gto@...>
Sent: Friday, March 28, 2008 11:53 AM
Subject: [ap-gto] Re: Autoguider correction frequency


So you are using your "on camera" guider and not something
like a
DSI
or independant webcam to guide with.

Thanks,

Hunter

--- In ap-gto@..., "Gedas" <w8bya@> wrote:

That's a good question Hunter. As far as I know I have not
loaded
ASCOM
onto this newly populated pc yet so I did not even access the
panel
you
mention. I just selected on-camera for mount type in PHD. I
should have
double checked the guide rate on the AP hand controller
however.
The last
time I tried AG it was set to 1x and assumed it did not
change,
that's a
poor assumption on my part, I should have looked.

Gedas
http://gedas.cc
http://www.w8bya.com



----- Original Message -----
From: "hewholooks" <hewholooks@>
To: <ap-gto@...>
Sent: Friday, March 28, 2008 11:04 AM
Subject: [ap-gto] Re: Autoguider correction frequency


Gedas,

What guiding rate did you set the AP ASCOM driver to (on
the
ASCOM
panel - NOT the PHD settings) when you used PHD - I believe
it
has
1x, 0.5x, and 0.25x as choices. I was wondering which to
use
when I
give it a try. Also, while I'm asking, what RA
aggressiveness
did
you select.

Hunter

--- In ap-gto@..., "Gedas" <w8bya@> wrote:

Murray, I use a 900GTO and the Orion guider along with
PHD.
Last
week I
tried the guider for the first time and found that for my
rough
polar
alignment and available stars, 2 second exposures provided
me
with
perfect
round stars for my 15 minute test frame. I'm sure I could
have
gone longer
between exposures but since it worked I didn't mess with
the
settings after
that. One note, I did have to reduce the ms step size
from (I
think the
default was 1000ms) to like 100ms. By default, the cal
star
would
quickly
leave the cal box if left alone. Once I changed it to
100ms,
this
reduced
how far the mount would move and I had solid guiding.

Gedas
http://gedas.cc
http://www.w8bya.com



----- Original Message -----
From: "mphammick" <mphammick@>
To: <ap-gto@...>
Sent: Thursday, March 27, 2008 4:18 PM
Subject: [ap-gto] Autoguider correction frequency


I have just bought the Orion Starshoot autoguider camera
and
have
got
some very sharp images with a TAK scope on an AP900
mount.

Has anyone else tried this system and if yes, what
frequency
setting
do they have for the corrections. I have a friend with a
Paramount ME
who says his guider corrects 10 times a second; this
seems
rather
high
to me. Does anyone have strong views as to how often the
guider
should
correct a reasonable AP900 ?

Murray


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Re: Autoguider correction frequency

Roland Christen
 

In a message dated 4/3/2008 12:55:50 PM Central Daylight Time,
rickwiggins@... writes:


Here are some of my settings with an AP155 on a AP1200 mount, guided
with a Tak FS60C and ST :
Periodic error = less than 0.8 arc secs PtP
Guider settings: Min error=0.04 pixels Max error=0.10 pixels, rate =
1x, aggressiveness 5 (=50%), exposure 2 secs
With these settings I am getting RMS guider errors of approximately
0.08 pixels and instantaneous errors not usually exceeding 0.2 pixels
This is on average seeing evenings. Even with these readings, I am
getting real corrections on mnay of the cycles.
You will always have some drift in both axes, even with perfect polar
alignment. Unless you are pointing straight up, the stars do not move at exactly the
sidereal rate, therefore RA will drift. They will move faster, and you will
get Dec drift also, simply because the real sky is slightly distorted by the
atmosphere.

Rolando


**************
Planning your summer road trip? Check out AOL Travel
Guides.

(http://travel.aol.com/travel-guide/united-states?ncid=aoltrv00030000000016)


The New Mount

hewholooks
 

'Afternoon,

Just got out in the sun today and got some documentary shots of the new
mount. I thought I would share it here, so you nice folks could see it.

http://hwilson.zenfolio.com/p612406172/

Thanks for lookin'

Hunter

PS - Hope you don't mind me lifting some verbage from your web site,
Roland.


Re: Autoguider correction frequency

Woodwind
 

Bob,

The results with the little Orion SSAG and the AP900 are so good that of course all it has done is to show up faults elsewhere in my system. Ten minute exposures have produced tack-sharp stars - but also revealed dust donuts on the images that were never there on the 60 second efforts.

Still - that is what this sport is all about - ratcheting up your system inch by dollar. Good stuff.

Murray



Bob Piatek <bobtek@...> wrote: Murray,

On your first question, I think the telescope mount manufacturers are
doing what they do best. I've owned several AP mounts and can't think
of a lot of ways they could improve. Maybe going to a USB interface
instead of the older Serial ports would be my top suggestion.
However, I think there are plenty of opportunities for advancing the
state of the art in auto-guide camera software.

Averaging several short guide star exposures is one of them.

Another technique that I heard of people trying was using multiple
guide stars to calculate position. The idea is that seeing related
changes would be seen differently by the various guide stars in the
field. I haven't seen much data on the results achieved by doing
this, however. My feeling is that small format sensors like that used
in guide cameras would have all stars in the image seeing the same
effect.

I did some work myself on something I call predictive guiding. The
idea is that you would collect historical guide star error data over a
period and then look for trends. For star drift due to polar miss-
alignment, for instance, you would typically see a fixed error in a
particular direction. Rather than waiting for one entire guide period
and then issue a single large correction, the software would portion
the same total correction via many smaller corrections. The idea is
to make smaller corrections but more frequent. The results I found
were significant.

What we need is to see more of the software developers out there
devoting more time to the guide problem. It seems to me that most of
their efforts are devoted to the image processing problem.

For your second question... you can certainly use the SSAG as a
primary imaging camera but there will be problems. First is the fact
that the SSAG is limited to only 8 bit data. This will not be enough
for many deep sky objects that need a camera with better dynamic range
to capture the fainter regions of the object. Secondly, the CMOS
image sensor in the SSAG suffers from line noise artifacts that will
limit its performance as an imaging camera. The Starfish design uses
the entire 10 bit pixel data captured by the sensor and has dedicated
image processing hardware to remove the dynamic line noise. So, you
can use it as a primary imaging camera for some of the brighter
objects but you really have to coax the image out of your raw data
during post processing to get good results. You'll make your life as
an astro-imager a lot easier by using a true 16bit camera for your
imaging.

Regards,

Bob PIatek

On Mar 31, 2008, at 11:38 AM, Murray Hammick wrote:
> Bob,
>
> Two questions - and thanks for your comments. I am the guilty one
> for setting this hare running.
>
> Would not the the best of both worlds be a system that allows you to
> select both the exposure time and the frequency of exposure. That
> will give you the chance to minimise loss of definition of brighter
> stars, but also avoid over-correcting the mount. Alternatively, the
> mount makers could allow you to choose settings to filter
> corrections and eliminate very small inputs attributable to poor
> seeing and other "noisy" variables.
>
> The other question is whether the Orion SSAG and similar cameras can
> be used as a "CCD" imager. The .05sec exposure setting indicates
> that it might be a very useful CCD subsitute - even if it is
> actually a CMOS device as someone pointed out on this thread.
>
> Murray
>


Re: Autoguider correction frequency

dan kowall
 

Yes.
It is mostly unreadable with text and images piled one on top of another.

dan
___
"William R. Mattil" <wrmattil@...> wrote: dan kowall wrote:
> I have the same problem.
> I'm using Firefox.
>
>
>
Dan,

The following page ?

http://www.fishcamp.com/starfish_shootout.html

Regards

Bill






---------------------------------
You rock. That's why Blockbuster's offering you one month of Blockbuster Total Access, No Cost.


Re: Autoguider correction frequency

dan kowall
 

I'm at 1680 x 1050 (Apple Cinema).
The overwriting occurs at all font sizes.
I'm a novice at html (actually below novice if that's possible), but the source code at Starfish shows a lot of absolute position layers. Wouldn't this cause the overwriting if not viewed at specific resolutions?

dan

______
Steve Reilly <sreilly@...> wrote: I've seen these problems before and it had to do with screen resolution. Try
maybe 1024x768. On my monitors at the suggested max 1680x1050, all is well.
Are you using normal font size or larger?

Steve


_____

From: ap-gto@... [mailto:ap-gto@...] On Behalf Of
dan kowall
Sent: Monday, March 31, 2008 5:00 PM
To: ap-gto@...
Subject: Re: [ap-gto] Re: Autoguider correction frequency

I have the same problem.
I'm using Firefox.

dan kowall

Alan Voetsch <alan_voetsch@ <mailto:alan_voetsch%40yahoo.com> yahoo.com>
wrote: Internet Explorer.

Alan

--- Bob Piatek <bobtek@... <mailto:bobtek%40mac.com> > wrote:

> Alan,
>
> I made the web site but did not check with every browser. There
> probably is a problem.
>
> What web browser are you using. I'll check it out on my end.
>
> Bob Piatek
>
>
>
>
> On Mar 31, 2008, at 11:15 AM, Alan Voetsch wrote:
> > Hey Bob,
> >
> > I wonder if it just my computer, but there are several areas in this
> > link where
> > text is covered by other text making it nearly impoossible to read.
> >
> > Alan
> >
> > --- Bob Piatek <bobtek@... <mailto:bobtek%40mac.com> > wrote:
> > > http://www.fishcamp <http://www.fishcamp.com/starfish_shootout.html>
.com/starfish_shootout.html
> >
> > Astrophotography: http://www.pbase. <http://www.pbase.com/avoetsch12952>
com/avoetsch12952
> >
>

Astrophotography: http://www.pbase. <http://www.pbase.com/avoetsch12952>
com/avoetsch12952

__________________________________________________________
OMG, Sweet deal for Yahoo! users/friends:Get A Month of Blockbuster Total
Access, No Cost. W00t
http://tc.deals. <http://tc.deals.yahoo.com/tc/blockbuster/text2.com>
yahoo.com/tc/blockbuster/text2.com

---------------------------------
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Access, No Cost. W00t










---------------------------------
You rock. That's why Blockbuster's offering you one month of Blockbuster Total Access, No Cost.


Re: Autoguider correction frequency

Paul Gustafson
 

Bob Piatek <bobtek@...> wrote:

http://www.fishcamp.com/starfish_shootout.html
Displays fine here, IE7 and Vista, 1900x1200.

http://www.astrophotoinsight.com/node/162
"Full text available to premium subscribers only"

Paul Gustafson


Re: Autoguider correction frequency

Joe Zeglinski
 

Alan,

No problem here - I'm using IE7 @ 1280 x 800 and 96 dpi. The links display correctly.
You may have to change screen settings, if there is overlap. Some websites have this kind of problem - e.g. OPTEC etc..

Joe

----- Original Message -----
From: "Alan Voetsch" <alan_voetsch@...>
To: <ap-gto@...>
Sent: Monday, March 31, 2008 1:15 PM
Subject: Re: [ap-gto] Re: Autoguider correction frequency


Hey Bob,

I wonder if it just my computer, but there are several areas in this link where
text is covered by other text making it nearly impoossible to read.

Alan

--- Bob Piatek <bobtek@...> wrote:
http://www.fishcamp.com/starfish_shootout.html


Astrophotography: http://www.pbase.com/avoetsch12952


____________________________________________________________________________________
You rock. That's why Blockbuster's offering you one month of Blockbuster Total Access, No Cost.
http://tc.deals.yahoo.com/tc/blockbuster/text5.com


------------------------------------

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Re: Autoguider correction frequency

Woodwind
 

The site was fine by me running a vista and firefox set-up.

Murray

Bob Piatek <bobtek@...> wrote: Well, the WEB page being messed up is puzzling. I've tested with IE,
Firefox, and Safari and it looks good on my system. I presume this
means it is not a browser related issue.

Maybe differences in graphics cards or video drivers? Maybe next time
I should pay a professional to do the web site :)

I'll try it on a couple of other computers I have around here and see
if I get different results.

Bob Piatek

fishcamp engineering
105 W. Clark Ave.
Orcutt, CA 93455

http://www.fishcamp.com
TEL: 805-937-6365
FAX: 805-937-6252

On Mar 31, 2008, at 3:15 PM, Hank Sielski wrote:
> Dan, Alan, Bob,
>
> FYI, I don't have any problems with the Fishcamp website, either with
> Firefox (2.0.0.13) nor with IE 6.0.2900.xxxx on an IBM Thinkpad T43
> Laptop
> running XP 1024x768...all pretty much plain vanilla, no special
> fonts or
> layout prefs...
>
> Good Luck,
>
> Hank
>


Re: Autoguider correction frequency

Bob
 

Well, the WEB page being messed up is puzzling. I've tested with IE, Firefox, and Safari and it looks good on my system. I presume this means it is not a browser related issue.

Maybe differences in graphics cards or video drivers? Maybe next time I should pay a professional to do the web site :)

I'll try it on a couple of other computers I have around here and see if I get different results.


Bob Piatek

fishcamp engineering
105 W. Clark Ave.
Orcutt, CA 93455

http://www.fishcamp.com
TEL: 805-937-6365
FAX: 805-937-6252

On Mar 31, 2008, at 3:15 PM, Hank Sielski wrote:
Dan, Alan, Bob,

FYI, I don't have any problems with the Fishcamp website, either with
Firefox (2.0.0.13) nor with IE 6.0.2900.xxxx on an IBM Thinkpad T43 Laptop
running XP 1024x768...all pretty much plain vanilla, no special fonts or
layout prefs...

Good Luck,

Hank


Re: Autoguider correction frequency

Kent Kirkley
 

In a message dated 03/31/08 13:38:40 Central Daylight Time, mphammick@... writes:
Would not the the best of both worlds be a system that allows you to select both the exposure time and the frequency of exposure. That will give you the chance to minimise loss of definition of brighter stars, but also avoid over-correcting the mount.

Bob:
The old SBIG ST-4, the SBIG STV (last firmware) and Maxim DL do/did this.

You choose the guiders exposure times and also choose the time between corrections.

I routinely use 2-6 second guider exposures with a STL-11000 and remote guide head and make a correction anywhere from 1 to 10 seconds. This is with an AP1200GTO mount that is very well polar aligned and needs very little correcting.

Kent Kirkley


Re: Autoguider correction frequency

William R. Mattil <wrmattil@...>
 

dan kowall wrote:
I have the same problem.
I'm using Firefox.


Dan,

The following page ?

http://www.fishcamp.com/starfish_shootout.html

Regards

Bill


Re: Autoguider correction frequency

Hank Sielski
 

Dan, Alan, Bob,

FYI, I don't have any problems with the Fishcamp website, either with
Firefox (2.0.0.13) nor with IE 6.0.2900.xxxx on an IBM Thinkpad T43 Laptop
running XP 1024x768...all pretty much plain vanilla, no special fonts or
layout prefs...

Good Luck,

Hank

On Mon, Mar 31, 2008 at 1:59 PM, dan kowall <dan_kowall@...> wrote:

I have the same problem.
I'm using Firefox.

dan kowall

Alan Voetsch <alan_voetsch@... <alan_voetsch%40yahoo.com>> wrote:
Internet Explorer.


Alan

--- Bob Piatek <bobtek@... <bobtek%40mac.com>> wrote:

Alan,

I made the web site but did not check with every browser. There
probably is a problem.

What web browser are you using. I'll check it out on my end.

Bob Piatek




On Mar 31, 2008, at 11:15 AM, Alan Voetsch wrote:
Hey Bob,

I wonder if it just my computer, but there are several areas in this
link where
text is covered by other text making it nearly impoossible to read.

Alan

--- Bob Piatek <bobtek@... <bobtek%40mac.com>> wrote:
http://www.fishcamp.com/starfish_shootout.html
Astrophotography: http://www.pbase.com/avoetsch12952
Astrophotography: http://www.pbase.com/avoetsch12952

__________________________________________________________
OMG, Sweet deal for Yahoo! users/friends:Get A Month of Blockbuster Total
Access, No Cost. W00t
http://tc.deals.yahoo.com/tc/blockbuster/text2.com





---------------------------------
OMG, Sweet deal for Yahoo! users/friends: Get A Month of Blockbuster Total
Access, No Cost. W00t





Re: Autoguider correction frequency

Steve Reilly <sreilly@...>
 

I've seen these problems before and it had to do with screen resolution. Try
maybe 1024x768. On my monitors at the suggested max 1680x1050, all is well.
Are you using normal font size or larger?

Steve


_____

From: ap-gto@... [mailto:ap-gto@...] On Behalf Of
dan kowall
Sent: Monday, March 31, 2008 5:00 PM
To: ap-gto@...
Subject: Re: [ap-gto] Re: Autoguider correction frequency



I have the same problem.
I'm using Firefox.

dan kowall

Alan Voetsch <alan_voetsch@ <mailto:alan_voetsch%40yahoo.com> yahoo.com>
wrote: Internet Explorer.

Alan

--- Bob Piatek <bobtek@... <mailto:bobtek%40mac.com> > wrote:

Alan,

I made the web site but did not check with every browser. There
probably is a problem.

What web browser are you using. I'll check it out on my end.

Bob Piatek




On Mar 31, 2008, at 11:15 AM, Alan Voetsch wrote:
Hey Bob,

I wonder if it just my computer, but there are several areas in this
link where
text is covered by other text making it nearly impoossible to read.

Alan

--- Bob Piatek <bobtek@... <mailto:bobtek%40mac.com> > wrote:
http://www.fishcamp <http://www.fishcamp.com/starfish_shootout.html>
.com/starfish_shootout.html

Astrophotography: http://www.pbase. <http://www.pbase.com/avoetsch12952>
com/avoetsch12952
Astrophotography: http://www.pbase. <http://www.pbase.com/avoetsch12952>
com/avoetsch12952

__________________________________________________________
OMG, Sweet deal for Yahoo! users/friends:Get A Month of Blockbuster Total
Access, No Cost. W00t
http://tc.deals. <http://tc.deals.yahoo.com/tc/blockbuster/text2.com>
yahoo.com/tc/blockbuster/text2.com





---------------------------------
OMG, Sweet deal for Yahoo! users/friends: Get A Month of Blockbuster Total
Access, No Cost. W00t


Re: Autoguider correction frequency

dan kowall
 

I have the same problem.
I'm using Firefox.

dan kowall

Alan Voetsch <alan_voetsch@...> wrote: Internet Explorer.

Alan

--- Bob Piatek <bobtek@...> wrote:

> Alan,
>
> I made the web site but did not check with every browser. There
> probably is a problem.
>
> What web browser are you using. I'll check it out on my end.
>
> Bob Piatek
>
>
>
>
> On Mar 31, 2008, at 11:15 AM, Alan Voetsch wrote:
> > Hey Bob,
> >
> > I wonder if it just my computer, but there are several areas in this
> > link where
> > text is covered by other text making it nearly impoossible to read.
> >
> > Alan
> >
> > --- Bob Piatek <bobtek@...> wrote:
> > > http://www.fishcamp.com/starfish_shootout.html
> >
> > Astrophotography: http://www.pbase.com/avoetsch12952
> >
>

Astrophotography: http://www.pbase.com/avoetsch12952

__________________________________________________________
OMG, Sweet deal for Yahoo! users/friends:Get A Month of Blockbuster Total Access, No Cost. W00t
http://tc.deals.yahoo.com/tc/blockbuster/text2.com






---------------------------------
OMG, Sweet deal for Yahoo! users/friends: Get A Month of Blockbuster Total Access, No Cost. W00t


Re: Autoguider correction frequency

Bob
 

Murray,

On your first question, I think the telescope mount manufacturers are doing what they do best. I've owned several AP mounts and can't think of a lot of ways they could improve. Maybe going to a USB interface instead of the older Serial ports would be my top suggestion. However, I think there are plenty of opportunities for advancing the state of the art in auto-guide camera software.

Averaging several short guide star exposures is one of them.

Another technique that I heard of people trying was using multiple guide stars to calculate position. The idea is that seeing related changes would be seen differently by the various guide stars in the field. I haven't seen much data on the results achieved by doing this, however. My feeling is that small format sensors like that used in guide cameras would have all stars in the image seeing the same effect.

I did some work myself on something I call predictive guiding. The idea is that you would collect historical guide star error data over a period and then look for trends. For star drift due to polar miss- alignment, for instance, you would typically see a fixed error in a particular direction. Rather than waiting for one entire guide period and then issue a single large correction, the software would portion the same total correction via many smaller corrections. The idea is to make smaller corrections but more frequent. The results I found were significant.

What we need is to see more of the software developers out there devoting more time to the guide problem. It seems to me that most of their efforts are devoted to the image processing problem.

For your second question... you can certainly use the SSAG as a primary imaging camera but there will be problems. First is the fact that the SSAG is limited to only 8 bit data. This will not be enough for many deep sky objects that need a camera with better dynamic range to capture the fainter regions of the object. Secondly, the CMOS image sensor in the SSAG suffers from line noise artifacts that will limit its performance as an imaging camera. The Starfish design uses the entire 10 bit pixel data captured by the sensor and has dedicated image processing hardware to remove the dynamic line noise. So, you can use it as a primary imaging camera for some of the brighter objects but you really have to coax the image out of your raw data during post processing to get good results. You'll make your life as an astro-imager a lot easier by using a true 16bit camera for your imaging.

Regards,

Bob PIatek

On Mar 31, 2008, at 11:38 AM, Murray Hammick wrote:
Bob,

Two questions - and thanks for your comments. I am the guilty one for setting this hare running.

Would not the the best of both worlds be a system that allows you to select both the exposure time and the frequency of exposure. That will give you the chance to minimise loss of definition of brighter stars, but also avoid over-correcting the mount. Alternatively, the mount makers could allow you to choose settings to filter corrections and eliminate very small inputs attributable to poor seeing and other "noisy" variables.

The other question is whether the Orion SSAG and similar cameras can be used as a "CCD" imager. The .05sec exposure setting indicates that it might be a very useful CCD subsitute - even if it is actually a CMOS device as someone pointed out on this thread.

Murray


Re: Autoguider correction frequency

Alan Voetsch <alan_voetsch@...>
 

Internet Explorer.

Alan

--- Bob Piatek <bobtek@...> wrote:

Alan,

I made the web site but did not check with every browser. There
probably is a problem.

What web browser are you using. I'll check it out on my end.

Bob Piatek




On Mar 31, 2008, at 11:15 AM, Alan Voetsch wrote:
Hey Bob,

I wonder if it just my computer, but there are several areas in this
link where
text is covered by other text making it nearly impoossible to read.

Alan

--- Bob Piatek <bobtek@...> wrote:
http://www.fishcamp.com/starfish_shootout.html
Astrophotography: http://www.pbase.com/avoetsch12952

Astrophotography: http://www.pbase.com/avoetsch12952


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Re: Autoguider correction frequency

Woodwind
 

Bob,

Two questions - and thanks for your comments. I am the guilty one for setting this hare running.

Would not the the best of both worlds be a system that allows you to select both the exposure time and the frequency of exposure. That will give you the chance to minimise loss of definition of brighter stars, but also avoid over-correcting the mount. Alternatively, the mount makers could allow you to choose settings to filter corrections and eliminate very small inputs attributable to poor seeing and other "noisy" variables.

The other question is whether the Orion SSAG and similar cameras can be used as a "CCD" imager. The .05sec exposure setting indicates that it might be a very useful CCD subsitute - even if it is actually a CMOS device as someone pointed out on this thread.

Murray

Bob Piatek <bobtek@...> wrote:
This is an interesting thread. Though I've gotten in late on the
discussion, a few points come to mind:

1) Although a guide camera may be able to take exposures as short as
20mS, this will result in the system trying to 'chase the seeing' as
others have pointed out. Long exposures of 1 second or more will
average out the perceived position of the guide star due to seeing
conditions. The problem with longer exposures is that you will tend
to saturate the image sensor when using bright guide stars. A
saturated guide star image will cause problems with the guider
software routines that compute the star centroid when measuring star
position. One way around this is to use a shorter exposure but to
average several pictures together before computing the guide star
position. That way you don't saturate on the bright guide stars and
also average out the seeing induced variations. Not many guider
software programs provide for this type of operation, however.

2) Auto-guiding is a closed loop system in that a measurement of the
guide star's position is made and then a correction is sent to the
mount to correct for any error. The process repeats indefinitely or
at least until the sun rises. The key premise here is that you cannot
make a guide correction faster than you can see the result. Otherwise
you have an unstable system. So, if you send a guide correction to
your mount, you better wait for the telescope movement to complete
before taking another picture. If you try to take a picture of your
guide star before the previous guide correction has finished, you will
erroneously conclude that the last correction didn't correct for the
error and you will probably do the wrong thing. Most telescopes have
a lot of mass and can't respond very quickly. That is what AO systems
promise. They can respond faster since they are moving an optical
element which has far less mass than your telescope mount.

3) Auto-guiding attempts to correct pointing problems regardless of
their cause. These can be any or all of problems with polar
alignment, periodic error, flexure, etc. So, if for instance you
have poor polar alignment, this will be detected by the auto-guider
and a large correction will be sent you your mount. Better polar
alignment will result in less drift between guide star pictures and
smaller corrections being made. Your stars will get progressively
rounder with smaller and smaller guide corrections. Likewise, auto-
guiding will correct for periodic error in the mount's drive train but
it would be better to have the mount's drive electronics perform the
periodic error correction. It is, after all, a very predictable error
and is best handled by the drive electronics. The auto-guider would
just try to make a correction after the error has occurred whereas the
drive electronics would be pro-active and not let the error occur in
the first place. The moral of the story is that there is no
substitute for addressing the sources of error where they lay. Your
auto-guider will have an easier job and your pictures will show better
results. I always say... ' the best auto-guider correction is one
that doesn't have to be made'.

4) I'm the designer of the Starfish Guide camera and, yes, it uses the
same image sensor as the Orion Starshoot Autoguider. Apart from using
the same image sensor the two cameras are distinctly different as the
following references point out:

http://www.fishcamp.com/starfish_shootout.html

http://www.astrophotoinsight.com/node/162

Regards,

Bob Piatek

fishcamp engineering
105 W. Clark Ave.
Orcutt, CA 93455

http://www.fishcamp.com
TEL: 805-937-6365
FAX: 805-937-6252


Re: Autoguider correction frequency

Bob
 

Alan,

I made the web site but did not check with every browser. There probably is a problem.

What web browser are you using. I'll check it out on my end.

Bob Piatek

On Mar 31, 2008, at 11:15 AM, Alan Voetsch wrote:
Hey Bob,

I wonder if it just my computer, but there are several areas in this link where
text is covered by other text making it nearly impoossible to read.

Alan

--- Bob Piatek <bobtek@...> wrote:
http://www.fishcamp.com/starfish_shootout.html
Astrophotography: http://www.pbase.com/avoetsch12952