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Dithering Questions


cuivenion

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Hi, I had my first attempt at ditthering last night, and it didn't go so well. I was using this to manually dither with phd2:

http://openphdguiding.org/phd2-dither-app/

Unfortunately it was taking along time to settle and I was getting an error message along the lines of 'max dec/ra duration to low, cannot find star'. I'd have to turn off the guiding and then start it again and the mount wouldn't settle for quite a few minutes, I gthink it was about 10 or more.

I'm wondering, should I turn off guiding before sending a dither command or does PHD2 take this into account? Here's the guidelog from the attempt:

Guidelog.thumb.jpg.f93de30d14ed373124f44f92f7327156.jpg

 

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2 minutes ago, spillage said:

Sorry I have only dithered through phd2 through apt and not had any issues this way. What software do you use with your altair?

Hi, Sharpcap, But the dithering is done manually via the app in the link.

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I see the equipment in the Guidelog is 640x480 PS3 guider, is that right, or are you using the GPCAM to guide?

How many pixels are you dithering?

I use the manual dither in the PHD2 Manual Move menu to Dither my 500D , typical values in my Guidelog display are no larger than 2.0, yours is 15 !!

So in your display, Dec has shot off a million miles, and takes a lot of Max Moves to return, but then overshoots - that's not right, it should Max Move back to zero and pick up guiding again.

You could make your Search Region bigger, might help.

I thought the PHD2 Dither App had to be used with Maxim, didn't know it was standalone?

Michael

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Hi Michael. I'm using the PS3 Eye to guide, typically 4-10s exposures. I was dithering with 15 pixels as I'd read somewhere this was a good idea for noisy camera's. The GPCAM is very noisy on long exposures. I'm not sure what you mean by Search Region, but I'm pretty new to guiding.

From what I've read in the instructions for the app it can be used by software,or you can double click the .vbs file to send a dither command manually. Thanks for your help.

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1 hour ago, michael8554 said:

I see the equipment in the Guidelog is 640x480 PS3 guider, is that right, or are you using the GPCAM to guide?

How many pixels are you dithering?

I use the manual dither in the PHD2 Manual Move menu to Dither my 500D , typical values in my Guidelog display are no larger than 2.0, yours is 15 !!

So in your display, Dec has shot off a million miles, and takes a lot of Max Moves to return, but then overshoots - that's not right, it should Max Move back to zero and pick up guiding again.

You could make your Search Region bigger, might help.

I thought the PHD2 Dither App had to be used with Maxim, didn't know it was standalone?

Michael

Just looked up Search Region. I may have to increase that if I'm using such agressive dithering.

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Also I seem to remember that with PHD2,  the dither is applied to the guidecam.

So 15 pixels on your guidecam will actually be:

 "Guider image scale" divided by "Imager pixel scale" times 15 pixels.

In other words many times more than 15 pixels on your imager.

Which would explain the huge excursions.

So you may need a figure more like 5 pixels in PHD2.

Michael

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