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bottletopburly

guiding log phd2 from last session

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So my last session i managed 2hrs 50 min  or so guiding with good results but how does the guiding log look is anything looking like it needs tweak ,mount is an eq6 belt modded , using a 200pds ,qhy5L -11 c, qhy mini guidescope. 

PHD2_GuideLog_2019-02-27_191533.txt

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I had a look using Pempro log viewer. Its a bit hard to analyse due to the dithering but there are signs of quite severe flexure (hundreds of arc seconds)

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1 hour ago, kens said:

I had a look using Pempro log viewer. Its a bit hard to analyse due to the dithering but there are signs of quite severe flexure (hundreds of arc seconds)

Would this likely be caused by the guidescope ken ?

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Ken, I see he's using a 3 second exposure, isn't Z filter best run at much faster rate eg 1 second ?

Michael

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9 hours ago, bottletopburly said:

Would this likely be caused by the guidescope ken ?

Most likely yes. Due to not being anchored securely enough. The following show the amount of drift on both axes (RA then DEC)

You can also see the size of the dithers. Given the short focal length you could reduce the size of the dithers.

RA.thumb.PNG.2133356418f358a856ea6300e6b1d66b.PNGDEC.thumb.PNG.76f6895ad19f13505f7d921b8394a335.PNG

8 hours ago, michael8554 said:

Ken, I see he's using a 3 second exposure, isn't Z filter best run at much faster rate eg 1 second ?

Michael

At 3 seconds the Z-filter offers no real advantage over Hysteresis. But it should not do any real harm. It can make recovery from dithers slow but does not look like an issue here.

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Posted (edited)

I will have a tweak thank @kens I thought I had changed back to hysteris obviously not will reduce dither in Apt or should I reduce scale in phd2 

edit - phd2 scale set to 0.5 ,apt dithering distance -5 , exposure set to 3 sec  will change back to hysteris(would predictive pec be beneficial using it with an Eq6 ken ) for now  see how the next session goes .

Edited by bottletopburly

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Having a closer look at the log, PemPro log viewer appears to be miscalculating the arcsecond values so both the dithers and drift are not as large as I first thought. Normally it does not show up but as you were guiding at 70deg declination the calculation error is magnified. I'll need to do some manual calculations now as you may not have any major issues at all. The performance between dithers looks pretty good,. I need to see if the drift is consistent with refraction ordue to flexure.

Your dithers are averaging around 5 pixels and the largest was 7 pixels. A 5 pixel dither should equate to 30 arcseconds or so. Depending on your imaging scale that sounds reasonable if a little on the high side. I understand that 10-20 pixels is the usual.

 

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5 hours ago, kens said:

Having a closer look at the log, PemPro log viewer appears to be miscalculating the arcsecond values so both the dithers and drift are not as large as I first thought. Normally it does not show up but as you were guiding at 70deg declination the calculation error is magnified. I'll need to do some manual calculations now as you may not have any major issues at all. The performance between dithers looks pretty good,. I need to see if the drift is consistent with refraction ordue to flexure.

Your dithers are averaging around 5 pixels and the largest was 7 pixels. A 5 pixel dither should equate to 30 arcseconds or so. Depending on your imaging scale that sounds reasonable if a little on the high side. I understand that 10-20 pixels is the usual.

 

Thanks for taking the time  ken , I use a canon 1000d  and the recommended dither I believe for this camera is around 10-12 pixel dither  so I will leave scale value as it is for now in phd2 , I am looking at securing cabling better on the guidescope so as to eliminate flexure .

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Don’t forget that to dither 10 pixels on your imaging camera you only need to dither around 3 or 4 pixels on your guide camera at 650mm FL, and 2 or 3 pixels at 1000mm FL.

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1 hour ago, kens said:

Don’t forget that to dither 10 pixels on your imaging camera you only need to dither around 3 or 4 pixels on your guide camera at 650mm FL, and 2 or 3 pixels at 1000mm FL.

So would I be better droppping scale in phd2 to say 0.5 , fl of guide scope is 130mm if memory serves me right I do find all that confusing at times ken .

Edited by bottletopburly

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For dithering you need to know both your imaging scale as well as your guiding scale. That’s because you want to dither , say, 10 pixels on your imaging camera and need to convert that to guiding pixels for PHD2 to do the dither.

I don’t use APT so I just had a look at the documentation and it is indeed confusing. I’m not sure what it sends to PHD2

Can you post your debug log? That will tell me what APT sends to PHD2

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4 minutes ago, kens said:

For dithering you need to know both your imaging scale as well as your guiding scale. That’s because you want to dither , say, 10 pixels on your imaging camera and need to convert that to guiding pixels for PHD2 to do the dither.

I don’t use APT so I just had a look at the documentation and it is indeed confusing. I’m not sure what it sends to PHD2

Can you post your debug log? That will tell me what APT sends to PHD2

I will have a look ken and get back to you 

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1 hour ago, kens said:

For dithering you need to know both your imaging scale as well as your guiding scale. That’s because you want to dither , say, 10 pixels on your imaging camera and need to convert that to guiding pixels for PHD2 to do the dither.

I don’t use APT so I just had a look at the documentation and it is indeed confusing. I’m not sure what it sends to PHD2

Can you post your debug log? That will tell me what APT sends to PHD2

Found this on Apt forum posted by ivo Dithering scale exists in both PHD and PHD2. So both the end dithering will be "Distance sent in APT"  x "Scale set in PHD" :)  i can't find the log file  though i do have the imaging values for guide scope and imaging camera if that helps , so in Apt i had set to 5(equates to 500ms) and phd set to 1.0

 

 

imaging scale values Capture.JPG

Edited by bottletopburly

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The dithering distance is controlled by APT. The scale in PHD is a multiplier of the distance set by APT. For example, say if 3 in APT gives a dither distance of 10 pixels ( at a guess) then a factor of 1 in PHD will give the same value of 10 pixels. If you set the scale at 5 then you would get a value of 50 pixels.

 

For the record, I've never actually measured the APT dither distance on my setup. It was quite large for my DSLR and I've made it a little smaller for the ASI1600.

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