Date
1 - 15 of 15
Nudge Guiding last night
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Roland Christen
Hi Astronuts,
I posted my guiding results from a 5 hour imaging session last night on Astrobin:
https://www.astrobin.com/ge4lnv/
I wanted to show how an Absolute Encoder Mount can enhance the guide accuracy and thereby improve the image resolution when using medium to long focal length telescopes.
There are always discussions on the various newsgroups that question whether an encoder mount is really necessary if you're going to guide anyway. The idea doesn't make sense until you realize that the encoders provide the mount axes with a very precise position according to the input commands of the servo controller. It means that if you can detect sub-arc sec errors in the position of the guide star, you can correct for them at a very precise level. You can also take 90% of the guide burden away for really long exposures by modeling, and thus driving both axes at a custom rate according to the model.
The encoder loop is not only accurate but very linear down to the sub-arc sec level. For example, a non-encoder mount can have non-linear response and discontinuity in Dec during direction reversals, even if the gears are belt driven. That can cause delays and even oscillations around the zero point. All that goes away with encoder control.
Last night was not especially great seeing, Clear Sky Clock rated it as a 3 out of 5, but it was good enough for the nudge guiding plus model tracking to track down to the 0.2 arc sec Pk level. Without the model and just normal full guiding (2 - 3 sec guide exposure) the system would be guiding at around 0.5 arc sec Pk (which isn't shabby).
Rolando
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Tony Benjamin <tonybenjamin@...>
You are using Maxim…how would you set this up in PHD2? Just very low aggression and greater than 5 sec exposure time?
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of uncarollo2 <chris1011@...> via groups.io
Hi Astronuts,
I posted my guiding results from a 5 hour imaging session last night on Astrobin:
I wanted to show how an Absolute Encoder Mount can enhance the guide accuracy and thereby improve the image resolution when using medium to long focal length telescopes.
There are always discussions on the various newsgroups that question whether an encoder mount is really necessary if you're going to guide anyway. The idea doesn't make sense until you realize that the encoders provide the mount axes with a very precise position according to the input commands of the servo controller. It means that if you can detect sub-arc sec errors in the position of the guide star, you can correct for them at a very precise level. You can also take 90% of the guide burden away for really long exposures by modeling, and thus driving both axes at a custom rate according to the model.
The encoder loop is not only accurate but very linear down to the sub-arc sec level. For example, a non-encoder mount can have non-linear response and discontinuity in Dec during direction reversals, even if the gears are belt driven. That can cause delays and even oscillations around the zero point. All that goes away with encoder control.
Last night was not especially great seeing, Clear Sky Clock rated it as a 3 out of 5, but it was good enough for the nudge guiding plus model tracking to track down to the 0.2 arc sec Pk level. Without the model and just normal full guiding (2 - 3 sec guide exposure) the system would be guiding at around 0.5 arc sec Pk (which isn't shabby).
Rolando
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Marcelo Figueroa
That's fantastic. The other night I was also testing this form of guidance using PHD2 and SGP, although not with such long exposures.
When I did it I noticed that in APCC Pro the tracking rate had changed from custom (comet icon) normally used when not using guiding, to sidereal. Is that normal?
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Roland Christen
PHD2 can be set up the same way. Very low Min Move. Very low aggression. I like to use 10 sec guide exposure in Maxim in order to minimize random sky motions. Set the delay between guide exposures to 5000 msec (5 sec) or even more if the seeing is very steady. MaximDL has good algorithm for finding the centroid even if the guide star is saturated, as it was in my case. I'm not sure if PHD2 can do that, so it would have to pick a fainter star.
One thing to be careful about is good cable management. You cannot have cables dragging or you will get sudden jumps that take longer to settle because of the slow guide cadence. I would do this type of guiding only for longish exposures, such as 20 min and longer for narrowband deep sky. If you dither, it will take longer to settle also. Make sure that the main camera exposure length doesn't saturate the object that you are recording. In my case the 1hr exposure did not saturate the tiny squiggles inside the Bubble nebula. It would very much saturate the core of a typical galaxy with a wideband LRGB filter set.
Rolando
-----Original Message-----
From: Tony Benjamin <tonybenjamin@...> To: main@ap-gto.groups.io Sent: Tue, Sep 22, 2020 1:55 pm Subject: Re: [ap-gto] Nudge Guiding last night You are using Maxim…how would you set this up in PHD2? Just very low aggression and greater than 5 sec exposure time?
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of uncarollo2 <chris1011@...> via groups.io
Sent: September 22, 2020 10:34 AM To: main@ap-gto.groups.io; main@ap-ug.groups.io Subject: [ap-gto] Nudge Guiding last night Hi Astronuts,
I posted my guiding results from a 5 hour imaging session last night on Astrobin:
I wanted to show how an Absolute Encoder Mount can enhance the guide accuracy and thereby improve the image resolution when using medium to long focal length telescopes.
There are always discussions on the various newsgroups that question whether an encoder mount is really necessary if you're going to guide anyway. The idea doesn't make sense until you realize that the encoders provide the mount axes with a very precise position according to the input commands of the servo controller. It means that if you can detect sub-arc sec errors in the position of the guide star, you can correct for them at a very precise level. You can also take 90% of the guide burden away for really long exposures by modeling, and thus driving both axes at a custom rate according to the model.
The encoder loop is not only accurate but very linear down to the sub-arc sec level. For example, a non-encoder mount can have non-linear response and discontinuity in Dec during direction reversals, even if the gears are belt driven. That can cause delays and even oscillations around the zero point. All that goes away with encoder control.
Last night was not especially great seeing, Clear Sky Clock rated it as a 3 out of 5, but it was good enough for the nudge guiding plus model tracking to track down to the 0.2 arc sec Pk level. Without the model and just normal full guiding (2 - 3 sec guide exposure) the system would be guiding at around 0.5 arc sec Pk (which isn't shabby).
Rolando
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Roland Christen
My MaximDL guide signals does not go thru APCC. MaximDL goes direct to the mount.
Rolando
-----Original Message-----
From: Marcelo Figueroa via groups.io <marfig1970@...> To: main@ap-gto.groups.io Sent: Tue, Sep 22, 2020 2:19 pm Subject: Re: [ap-gto] Nudge Guiding last night That's fantastic. The other night I was also testing this form of guidance using PHD2 and SGP, although not with such long exposures.
When I did it I noticed that in APCC Pro the tracking rate had changed from custom (comet icon) normally used when not using guiding, to sidereal. Is that normal?
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Michael Hambrick <mike.hambrick@...>
Hi Roland
You refer to the seeing as rated by Clear Sky Clock. Is that a free web site or a subscription service ? Do you have any techniques that you use yourself to estimate what the seeing is ? I would love to get a better explanation of the how the seeing ratings are defined. Best Regards Michael Hambrick ARLANXEO TSR Global Manufacturing Support PO Box 2000 Orange, TX 77631-2000 Phone: +1 (409) 882-2799 email: mike.hambrick@...
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Sébastien Doré
+1 on this one...
Sébastien
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Roland Christen
You can judge seeing by doing a few minutes of tracking and just examine the guide star tracking in the guide graph with guide pulses turned OFF. That's it in a nutshell.
Rolando
-----Original Message-----
From: Michael Hambrick via groups.io <mike.hambrick@...> To: main@ap-gto.groups.io Sent: Tue, Sep 22, 2020 2:45 pm Subject: Re: [ap-gto] Nudge Guiding last night Hi Roland
You refer to the seeing as rated by Clear Sky Clock. Is that a free web site or a subscription service ? Do you have any techniques that you use yourself to estimate what the seeing is ? I would love to get a better explanation of the how the seeing ratings are defined. Best Regards Michael Hambrick ARLANXEO TSR Global Manufacturing Support PO Box 2000 Orange, TX 77631-2000 Phone: +1 (409) 882-2799 email: mike.hambrick@...
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Hi Roland,
toggle quoted messageShow quoted text
how do you do that? I have MaximDL connected to the AP driver. The driver do as I sought is connected to APCCC and APCC to the control Box. Konstantin
Konstantin v. Poschinger
Hammerichstr. 5 22605 Hamburg 040/8805747 0171 1983476
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Roland Christen
The guide signals are not modified by APCC. Yes, of course MaximDL has to be connected to the driver, so the guide signals go to the mount with proper protocol. Using guiding and custom tracking in APCC works fine. It also works fine when using the simple model created by the keypad.
Rolando
-----Original Message-----
From: Konstantin von Poschinger <KPoschinger@...> To: main@ap-gto.groups.io Sent: Tue, Sep 22, 2020 3:24 pm Subject: Re: [ap-gto] Nudge Guiding last night Hi Roland,
how do you do that? I have MaximDL connected to the AP driver. The driver do as I sought is connected to APCCC and APCC to the control Box.
Konstantin
Konstantin v. Poschinger
Hammerichstr. 5 22605 Hamburg 040/8805747 0171 1983476
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Roland,
toggle quoted messageShow quoted text
is the new Keypad Software available in the meantime? Konstantin
Konstantin v. Poschinger
Hammerichstr. 5 22605 Hamburg 040/8805747 0171 1983476
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Roland Christen
For the Mach2 yes. It's in your keypad if you purchased one.
Rolando
-----Original Message-----
From: Konstantin von Poschinger <KPoschinger@...> To: main@ap-gto.groups.io Sent: Tue, Sep 22, 2020 3:31 pm Subject: Re: [ap-gto] Nudge Guiding last night Roland,
is the new Keypad Software available in the meantime?
Konstantin
Konstantin v. Poschinger
Hammerichstr. 5 22605 Hamburg 040/8805747 0171 1983476
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Will there be no update for existing Keypads? Are this keypads only work for the Mach2? I have written that the new software also works on the GTOCP4 for other mounts.
toggle quoted messageShow quoted text
Konstantin
Konstantin v. Poschinger
Hammerichstr. 5 22605 Hamburg 040/8805747 0171 1983476
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CurtisC <calypte@...>
I still have my keypad from 2010. It doesn't even have Parks 4 and 5.
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Roland Christen
Will there be no update for existing Keypads? Are this keypads only work for the Mach2? I have written that the new software also works on the GTOCP4 for other mounts. Yes there will be updates for existing keypads.
The keypads will work seamlessly for both CP4 and CP5
Rolando
-----Original Message-----
From: Konstantin von Poschinger <KPoschinger@...> To: main@ap-gto.groups.io Sent: Tue, Sep 22, 2020 4:23 pm Subject: Re: [ap-gto] Nudge Guiding last night Will there be no update for existing Keypads? Are this keypads only work for the Mach2? I have written that the new software also works on the GTOCP4 for other mounts.
Konstantin
Konstantin v. Poschinger
Hammerichstr. 5 22605 Hamburg 040/8805747 0171 1983476
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