Date   

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


____________________________________________________________________________________
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


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


Re: Autoguider correction frequency

Alan Voetsch <alan_voetsch@...>
 

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


Re: Autoguider correction frequency

Bob
 

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

Kurt Mihalco <mihalco@...>
 

Actually, the SSAG is based on a relatively inexpensive CMOS imager,
not a CCD. I don't know if Orion used it in a previous product. I
believe the Starfish guider by Fishcamp Engineering uses the same
chipset (Micron MT9M001C12STM).
Kurt

--- In ap-gto@..., Murray Hammick <mphammick@...> wrote:

The Orion SSAG is actually a repackaged version of an older CCD
camera. I have seen some stunning views of the moon taken with it - so
I can only assume that it can be an effective CCD.


Re: Autoguider correction frequency

Kurt Mihalco <mihalco@...>
 

Hi Murray,
To answer your question, the main reason for allowing short exposures
is for non-astro imaging. The cmos imaging and associated driver
chips are general purpose and marketed for all sorts of applications,
many of which are video surveillance. For these uses, the short
exposures are necessary to avoid saturation in daylight
applications. Orion happens to use this imager and chipset in the
Starshoot autoguider primarily because it is cheap relative to the
CCD imagers and support chips. It is also less sensitive, but who
cares - you simply take a 1 sec exposure instead of 1/2 second. For
this application, it really doesn't matter. Again, the autoguider can
only digitize and deliver a full frame to the computer every 1/15
second - even if the exposure is 1/1000 a second (or less).
Regarding the mount response, others have already commented. Trying
to move the mass of the tube 15 times/second is pretty much like like
tapping on the side of the tube - it takes a while for the impulse to
settle out. If it is constantly being done, it never reaches
equilibrium. That's why those that want the fast corrections (that
take into account atmospheric seeing) use the SBIG AO hardware.
These can be driven at high rates (up to 60 corrections/sec) due to
their low mass. Hope this helps.
Regards,
Kurt


--- In ap-gto@..., Murray Hammick <mphammick@...> wrote:

Kurt,

I do not have a problem with the maths - that is a straightforward
calculation.

What I do have a question about is why the software in the
autoguider has the ability to sample as often as up to 20 times per
second if there is no real requirement to do so. According to others
on this site (including Roland) you should be looking at corrections
every second or slower. So what sort of mount is able to make good
use of those 1/20th or a second exposures which imply a correction
rate of up to 20Hertz. I say "up to" because of course if you have a
good mount then you might only be correcting very 20, 30 or 100
exposures or whatever.

Perhaps this is a redundant thread for an AP site as the view is
that a setting of 1 sec or slower is what is needed for mounts like
the Mach 1, 900, 1200 etc. and this will avoid over-correcting and
bouncing the mount around as it tries to "chase its tail".

Murray


Re: Autoguider correction frequency

Woodwind
 

The Orion SSAG is actually a repackaged version of an older CCD camera. I have seen some stunning views of the moon taken with it - so I can only assume that it can be an effective CCD.

More than that I cannot say - perhpas someone else has a view (sorry about pun).

Larry Phillips <llp41astro@...> wrote: Can this camera work like a webcam and capture many frames per second
to do planet imaging? Just a thought.

Larry

--- In ap-gto@..., Murray Hammick <mphammick@...> wrote:
>
> Kurt,
>
> I do not have a problem with the maths - that is a straightforward
calculation.
>
> What I do have a question about is why the software in the
autoguider has the ability to sample as often as up to 20 times per
second if there is no real requirement to do so. According to others
on this site (including Roland) you should be looking at corrections
every second or slower. So what sort of mount is able to make good
use of those 1/20th or a second exposures which imply a correction
rate of up to 20Hertz. I say "up to" because of course if you have a
good mount then you might only be correcting very 20, 30 or 100
exposures or whatever.
>
> Perhaps this is a redundant thread for an AP site as the view is
that a setting of 1 sec or slower is what is needed for mounts like
the Mach 1, 900, 1200 etc. and this will avoid over-correcting and
bouncing the mount around as it tries to "chase its tail".
>
> Murray
>
>
>
>
> Kurt Mihalco <mihalco@...> wrote: Hi
Murray,
> First, I don't have an Orion Starshoot autoguide camera, so my
> comments could be inaccurate. Their specs show a maximum full res
> frame rate of 15 fps. This is based on the time it takes the
> hardware to scan out and digitize the imager at full resolution
and
> transfer it to the PC over the USB. So, irrespective of the
> exposure, 15 frames per second is the maximum the camera is
capable
> of delivering a full frame image to the PC (I don't know if the
> camera supports binning or ROI, which could allow for faster frame
> rates). The PC sofware (PHDGuide?) then
> has to process the frame, compare it to the previous one, and
issue
> any guiding commands, back through the USB to the camera, which
then
> closes the solid state switches which command the mount to move a
> particular direction (by the SBIG compatible interface). If your
> exposure is greater than 1/15 second (66.7 mscec), then the frame
> rate the camera delivers images to the PC must slow down
> accordingly. For example, if you set a 1/2 second exposure, then
the
> camera can only deliver 2 frames per second to the PC. The key
point
> here is that the guide software is what issues the corrections to
the
> mount (through some hardware in the camera head). The camera
itself
> only delivers the images to the PC based software which analyzes
them
> and determines the appropriate corrections. The PC Software
cannot
> issue guiding corrections any faster than the camera is delivering
> images to it. If the camera is taking 2 second exposures, then the
> maximum rate the software can issue a correction to the mount is
> every 2 seconds. Hope this makes sense.
> Regards,
> Kurt Mihalco
>
> --- In ap-gto@..., Murray Hammick <mphammick@> wrote:
> >
> > I hear what you say and do not doubt the veracity of your
comments -
>
> and especially Roland's authority in this matter.
> >
> > That said - why does the Orion guide camera offer you a choice
of
> exposure down to .02 sec ? Is it in fact not sending corrections
> after
> each exposure (assuming less than perfect tracking of course) ?
> >
> > Murray
>
>
>
>
>
>
>
>


Re: Autoguider correction frequency

Larry Phillips
 

Can this camera work like a webcam and capture many frames per second
to do planet imaging? Just a thought.

Larry

--- In ap-gto@..., Murray Hammick <mphammick@...> wrote:

Kurt,

I do not have a problem with the maths - that is a straightforward
calculation.

What I do have a question about is why the software in the
autoguider has the ability to sample as often as up to 20 times per
second if there is no real requirement to do so. According to others
on this site (including Roland) you should be looking at corrections
every second or slower. So what sort of mount is able to make good
use of those 1/20th or a second exposures which imply a correction
rate of up to 20Hertz. I say "up to" because of course if you have a
good mount then you might only be correcting very 20, 30 or 100
exposures or whatever.

Perhaps this is a redundant thread for an AP site as the view is
that a setting of 1 sec or slower is what is needed for mounts like
the Mach 1, 900, 1200 etc. and this will avoid over-correcting and
bouncing the mount around as it tries to "chase its tail".

Murray




Kurt Mihalco <mihalco@...> wrote: Hi
Murray,
First, I don't have an Orion Starshoot autoguide camera, so my
comments could be inaccurate. Their specs show a maximum full res
frame rate of 15 fps. This is based on the time it takes the
hardware to scan out and digitize the imager at full resolution
and
transfer it to the PC over the USB. So, irrespective of the
exposure, 15 frames per second is the maximum the camera is
capable
of delivering a full frame image to the PC (I don't know if the
camera supports binning or ROI, which could allow for faster frame
rates). The PC sofware (PHDGuide?) then
has to process the frame, compare it to the previous one, and
issue
any guiding commands, back through the USB to the camera, which
then
closes the solid state switches which command the mount to move a
particular direction (by the SBIG compatible interface). If your
exposure is greater than 1/15 second (66.7 mscec), then the frame
rate the camera delivers images to the PC must slow down
accordingly. For example, if you set a 1/2 second exposure, then
the
camera can only deliver 2 frames per second to the PC. The key
point
here is that the guide software is what issues the corrections to
the
mount (through some hardware in the camera head). The camera
itself
only delivers the images to the PC based software which analyzes
them
and determines the appropriate corrections. The PC Software
cannot
issue guiding corrections any faster than the camera is delivering
images to it. If the camera is taking 2 second exposures, then the
maximum rate the software can issue a correction to the mount is
every 2 seconds. Hope this makes sense.
Regards,
Kurt Mihalco

--- In ap-gto@..., Murray Hammick <mphammick@> wrote:
>
> I hear what you say and do not doubt the veracity of your
comments -

and especially Roland's authority in this matter.
>
> That said - why does the Orion guide camera offer you a choice
of
exposure down to .02 sec ? Is it in fact not sending corrections
after
each exposure (assuming less than perfect tracking of course) ?
>
> Murray






[Non-text portions of this message have been removed]


(No subject)

Pierre Henrotay
 

Hi Gerald,

I received with the printed manual a small sheet of paper with
title "Special Notice to Mach1GTO Owners".
This says that :
- The keypad is set to 1200GTO.
- The parameters for Mach1GTO, 900GTO and 1200GTO are all identical
and that either the 900 or 1200 setting will work fine.
- And finally: "do not, however, set the keypad to either 400 or 600E"


Pierre

--- In ap-gto@..., Gerald Sargent <sargentg@...> wrote:

My hand controller on my Mach! under mount selection lists
as options 400, 600, 900, 1200, but not Mach 1.
Which one should I select ?
Does it make a difference ?