APT - dithering settings for PHD

[Russe]

Guys,

Every day smth new - never realised that you can connect PHD & APT. Saw for the first time that I could dither with through APT.

Anyone tried that? Any idea on the settings?

Dithering distance 1-5

Dithering stability

Dithering settle time

D-ing timeout

Auto cancel exposure on/off

Auto cancel distance

Help much appreciated!!

[Russe]

This is from APT's help file:

XIX. Guiding programs integration - APT can cooperate with two guiding programs:

-Stark Labs PHD Guiding

(www.stark-labs.com)

-MetaGuide by Frank Freestar8n (www.astrogeeks.com/Bliss/MetaGuide/).

Also supported is the Lacerat MGen auto-guiding solution.

 

When there is no guiding APT can make dithering itself when there is connection to the mount.

The supported functions are fast switching to the guiding program window, auto-dithering between exposures and auto real-time monitoring of the distance to the

guiding star when PHD or MGen are used (in the main window, ‘Info’ section, PHD/MGen Status)

Auto-dithering is a small change of the position of the telescope between the exposures. It reduces the banding noise in your images and minimizes the data loss from hot and cold pixels.

Auto-cancel allows stopping the exposure before a guiding problem becomes visible on your image allowing to use the gathered so far data.

 

The fast switching can be made with a simple click on the ‘Guide’ button. It will minimize APT’s window and will bring to focus the window of the guiding program.

NOTE: to use PHD integration functions it has to be configured in Server mode. Select from PHD’s menus 'Tools'->'Enable Server'. To enable/disable and tune the other guiding functions, please use “Shift+Click” on the ‘Guide’ button. This will open the Guiding settings dialog box. In the settings dialog you can tune the following parameters:

o Guiding program – select the guiding program you are using.

o Auto-Dithering - enables/disables auto dithering.

o Auto-Dithering Distance – defines what to be the dithering distance (implemented for PHD, APT and MGen only)

o MGen mode – defines the dithering mode for the MGen device

o Dithering Stability Distance - defines the acceptable distance to consider that dithering is completing. The distance is in pixels from 0.00 to 2.55. See the explanation below. (implemented for PHD only)

o Dithering Settle Time – defines how many seconds to wait after Dithering Stability distance is reached. It gives time guiding to settle down. See the explanation below. (implemented for PHD, APT and MGen only)

o Dithering Timeout - defines the maximum time for d

ithering. After that time

APT will continue with the next exposure no matter

what is the distance to the

guiding start. 0s means that there is no time limit

to complete the dithering.

When MetaGuide is used this defines when to resume

with next exposure.

o

Auto-Cancel - enables/disables Auto Canceling. Aut

o Canceling allows

canceling exposure when the distance to the guiding

star becomes greater

than a defined value. (implemented for PHD

and MGen

only)

o

Auto Cancel Distance - defines the maximum accepta

ble distance to the

guiding star. After this point the exposure has to

be canceled. The values are

in pixels form 0.00 to 2.55. (implemented for PHD

and MGen

only)

o

PHD IP address – Defines the IP address of the com

puter that is used for

guiding. This feature is useful if you use separate

computer for guiding. The

default values is 127.0.0.1 which means that same c

omputer is used for

imaging and for guiding.

The auto-dithering and auto-canceling are applied o

nly to the exposures plans of

LIGHT type. When it is enabled it works by the foll

owing algorithm:

PHD version – After the exposure is finished, APT s

ends command to PHD to

make a dithering, and starts to monitor when the di

stance to the guiding start will

become smaller than the defined Stability distance.

Once this happens it will wait

a number of seconds defined for Settle time, which

gives possibility of PHD to

settle down. After that time APT will resume with t

he next exposure. The timeout

value defines how many seconds you want to give to

PHD to reach the settle

distance, and after this moment APT will resume wit

h the next exposure, no

matter what is the distance to the guiding start. I

f the settle distance is reached

the timeout value will be ignored.

MetaGuide version – After the exposure is finished,

APT sends command to

MetaGuide to make a dithering and waits the number

of seconds defined by

timeout value and after that will resume with the n

ext exposure.

APT Dithering – After the exposure APT will move th

e mount in small steps with

random length and direction. In order to work there

is need to enter the focal

length of the telescope and when CCD is used to ent

er the sensor dimensions

and pixel size.

MGen version – After the exposure is finished, APT

sends command to MGen to

make a dithering, and waits for the command complet

ion. Once this happens it

will wait a number of seconds defined for Settle ti

me, which gives possibility of

MGen to settle down. After that time APT will resum

e with the next exposure. The

timeout value defines how many seconds you want to

give to MGen to complete

the command, and after this moment APT will resume

with the next exposure. If

the dithering command is completed in time the time

out value will be ignored.

[Christopher Davenport]

I am very much a noob to APT and PHD, so my experience is limited.

I have tried this, once and it worked quiet well. 

Although it never returned me to the exact same place, so my images were slightly off each time.

I think this is the point of dithering, so I can use cappa sigma stacking and avoid using darks.

Worked okay for me, but it does waste time for taking lights.

Sorry I can't help more.

[lensman57]

Guys,

Every day smth new - never realised that you can connect PHD & APT. Saw for the first time that I could dither with through APT.

Anyone tried that? Any idea on the settings?

Dithering distance 1-5

Dithering stability

Dithering settle time

D-ing timeout

Auto cancel exposure on/off

Auto cancel distance

Help much appreciated!!

Hi,

Launch PHD first and enable server under the Tools Menu, launch APT, Gear, double click guiding and adjust the parameters as per Russe instructions, for a DSLR you want a high ditter and a longish settle time, with a cooled ccd more conservative settings will be fine but allow long eough settle time for the guiding to resumue.

Regards,

A.G

[Leveye]

Make sure you check "enable server" in tools in PHD. PHD2 just received an update that shortens dithering recovery time. I have heard that a setting of 3-4 for the dithering distance is working pretty good. Clear skies soon for me to test it out.

[Yoddha]

Hi Russe,

I would suggest to start with the default values Then:

-If the movement is not enough then increase the distance.

-If there are trails lower the stability distance

-If you see timeouts increase the Dithering Timeout

Hope this helps

[RikM]

The default values always work well for me.

[Russe]

I've found this. But it's not so detailed to figure out one's problems...

[Yoddha]

I'm open for ideas, suggestions and questions  Please let me know what is unclear and I'll give my best. 

English is not my mother tongue and as you see documentation is not my strongest side

[AstroAdam]

I'm open for ideas, suggestions and questions  Please let me know what is unclear and I'll give my best. 

English is not my mother tongue and as you see documentation is not my strongest side

I wish my <insert any language except English here>  was as good as your English....

[Russe]

I'm open for ideas, suggestions and questions Please let me know what is unclear and I'll give my best.

English is not my mother tongue and as you see documentation is not my strongest side

Dithering Settle Time – defines how many seconds to wait after Dithering Stability distance is reached. It gives time guiding to settle down. See the explanation below. (implemented for PHD, APT and MGen only)

Dithering Timeout - defines the maximum time for dithering. After that time APT will continue with the next exposure no matter what is the distance to the guiding start. 0s means that there is no time limit to complete the dithering.

When MetaGuide is used this defines when to resume with next exposure.

Auto-Cancel - enables/disables Auto Canceling. Auto Canceling allows canceling exposure when the distance to the guiding star becomes greater than a defined value. (implemented for PHD and MGen only)

Auto Cancel Distance - defines the maximum acceptable distance to the guiding star. After this point the exposure has to be canceled. The values are in pixels form 0.00 to 2.55. (implemented for PHD and MGen only)

If I continue to hit a wall at 300s before getting eggy stars, it's probably more of a PHD settings problem rather than settling times etc. what are commonly used settings for the above mentioned 4 settings in dithering?

May I just say as well - great program - this APT. I love it!! I'm just frustrated at my inability at going longer than 300s...

[Christopher Davenport]

Russ,

+1 on APT, it eats BYEOS for breakfast and for 10 quid you get advanced equipment control. I love it!

IMHO, I don't think your 300s woes are a PHD problem.

It's either polar align or periodic error.

To test theory, why not do a guide session using PhD, then switch to metaguide and see if you get past your mark, if not then at least you have illiminated it as the problem.

Next take try to do a 300s drift align and see if it helps.

If still happens next problem illiminated.

Lastly I suggest you look at quartermasters blog on the New autopec in New version of eqmod.

But it would be good to hear what others think?

[Yoddha]

I wish my <insert any language except English here>  was as good as your English....

Thank you!

[Yoddha]

Dithering Settle Time – defines how many seconds to wait after Dithering Stability distance is reached. It gives time guiding to settle down. See the explanation below. (implemented for PHD, APT and MGen only)

Dithering Timeout - defines the maximum time for dithering. After that time APT will continue with the next exposure no matter what is the distance to the guiding start. 0s means that there is no time limit to complete the dithering.

When MetaGuide is used this defines when to resume with next exposure.

Auto-Cancel - enables/disables Auto Canceling. Auto Canceling allows canceling exposure when the distance to the guiding star becomes greater than a defined value. (implemented for PHD and MGen only)

Auto Cancel Distance - defines the maximum acceptable distance to the guiding star. After this point the exposure has to be canceled. The values are in pixels form 0.00 to 2.55. (implemented for PHD and MGen only)

If I continue to hit a wall at 300s before getting eggy stars, it's probably more of a PHD settings problem rather than settling times etc. what are commonly used settings for the above mentioned 4 settings in dithering?

May I just say as well - great program - this APT. I love it!! I'm just frustrated at my inability at going longer than 300s...

If you have doubts that dithering is the reason, I'll suggest to lower the value "Dithering Stability". My opinion is that if dithering is bugging then the "eggs" will be will different directions. As you know PHD makes random moves. If the "eggs" are in same direction then I join to Christopher that problem is in the polar alignment or PE. 

Thanks!

[Yoddha]

Russ,

+1 on APT, it eats BYEOS for breakfast and for 10 quid you get advanced equipment control. I love it!

IMHO, I don't think your 300s woes are a PHD problem.

It's either polar align or periodic error.

To test theory, why not do a guide session using PhD, then switch to metaguide and see if you get past your mark, if not then at least you have illiminated it as the problem.

Next take try to do a 300s drift align and see if it helps.

If still happens next problem illiminated.

Lastly I suggest you look at quartermasters blog on the New autopec in New version of eqmod.

But it would be good to hear what others think?

Thank you Christopher!

[Russe]

If you have doubts that dithering is the reason, I'll suggest to lower the value "Dithering Stability". My opinion is that if dithering is bugging then the "eggs" will be will different directions. As you know PHD makes random moves. If the "eggs" are in same direction then I join to Christopher that problem is in the polar alignment or PE.

Thanks!

Eggs are in different directions when I dither.

I shall lower the stability. Any idea what to?

[Yoddha]

Ok, try to set the Stability to half of the current value and also increase the Settle time... If still have eggs then continue to lower the Stability

[Yoddha]

I see that you use finder guider. Maybe you can try with 0.10 first...

[alcol620]

Since this exchange of views last year. What is the consensus on the values to use for the various parameters?

[Yoddha]

The best way is to experiment Start with the default parameters...

The move is controlled by "Dithering distance" if it is small increase it. If it is still small then use "Dithering Scaling" in the PHD's brain dialog box.

Then stability and stability should be easy to tune (if there is need at all)

[alcol620]

Thanks Ivo

After posting I have had a play around as you suggest and it now works.

APT is a great piece of software and with PHD in tandem is magic.  Many thanks for all your efforts

Alec

[glowingturnip]

APT is a great piece of software and with PHD in tandem is magic.  Many thanks for all your efforts

I second that !

[Yoddha]

Thank you very much Alec and Stuart!

[ianpwilliams]

Hi,

Launch PHD first and enable server under the Tools Menu, launch APT, Gear, double click guiding and adjust the parameters as per Russe instructions, for a DSLR you want a high ditter and a longish settle time, with a cooled ccd more conservative settings will be fine but allow long eough settle time for the guiding to resumue.

Regards,

A.G

Hi, I've just upgraded to guided imaging and I'm very keen to try dithering so that I can give flats and darks a miss. I'm using APT and PHD2.

Would anyone happen to have any links which explain how to do it?

I can no doubt do what AG says above, and someone said to start with the default settings, but is there anything else I should know when I try to get it going?

And if the default settings don't work, how can I be prepared so that I know what to do, rather than randomly changing parameters and hoping for the best?

And would setting up the dithering be the final step before imaging, and after polar alignment, framing, centering, focusing, and guiding?

[alcol620]

Try this link for starters    http://www.rosecityastronomers.org/resources/pdf/GuideToGuiding.pdf

APT is super software and capable of doing most things, if it doesn't then Ivo is on the case to make sure it does!

Magic when it all works. You will still need flats even if you dither.

Good luck

Alec