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"Correctly configuring SubFrameSelector

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#1 Ballyhoo

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Posted 20 April 2019 - 05:12 PM

Per Wade,  Wade recommended me posting here for help on configuring my PI script, SFS, which also has a process of same name. Thanks because I have not been able to get the right parameters. And once I get them, (and for settings in scripts and processes in general) how do you get the settings to stick? For example, integration and calibration settings, sometimes I notice reset when I launch a new instance.

 

Telescope:  Orion eon, 85MM FL 560 mm (6.6)

(the linked subs were imaged also with use of 2x barlow.)

Focal Length, above
Focal Ratio above
Camera Model, ASI 294 Pro

Include a link to a sample raw sub exposure that you'd like to test (below)  Make sure that it's of good quality - one of your best,,

 

Not sure about the Fits thing.(???)

 

 

LINK:

 

https://www.dropbox....NzZcmwmCVa?dl=0

 

 

For some reason I had to super crop my final processed image which was about 2 hours of integration. 

 

Note, these subs from the link were 3 min subs, gain 120. As stated, I was using a 2 x barlow and no flattner,

Attached Thumbnails

  • triplet april 10.gif

Edited by Ballyhoo, 20 April 2019 - 05:40 PM.


#2 fmeschia

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Posted 20 April 2019 - 05:23 PM

Isn’t this the third of fourth time you ask this same question? Weren’t the previous answers satisfactory?



#3 Ballyhoo

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Posted 20 April 2019 - 05:30 PM

Isn’t this the third of fourth time you ask this same question? Weren’t the previous answers satisfactory?

Whatever values I got in SFS, I am not 100% confident about. Or, I do not like the results. 

 

Edit,

 

Another topic and John Rista opined against use of barlow. I bet that would account for an increased eccentricity. But, so, the eccentric values where high (?). Is it numbers we care about, or final product?  I am not doing this to produce nice numbers, but great images.  Without a barlow I feel that my objects are too small; FOV too giant.  And barlow increases resolution (when seeing permits.)  


Edited by Ballyhoo, 20 April 2019 - 05:38 PM.


#4 StephenW

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Posted 20 April 2019 - 05:38 PM

There are no "magically" correct numbers to use - it depends on the quality of the frames you have captured and are providing as input, and how strict/fussy you want to be about the frames you should keep and include in your stack.

 

>I do not like the results.

 

If there is something specific you can identify about what you don't like in the results, then maybe(!) there is some advice we can give on what to tweak, but in the end your best bet will be to play with the settings until you get results you are happy with (and of course, those settings/results may not be the same as someone else would chose, but that's Ok).



#5 Ballyhoo

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Posted 20 April 2019 - 05:42 PM

There are no "magically" correct numbers to use - it depends on the quality of the frames you have captured and are providing as input, and how strict/fussy you want to be about the frames you should keep and include in your stack.

 

>I do not like the results.

 

If there is something specific you can identify about what you don't like in the results, then maybe(!) there is some advice we can give on what to tweak, but in the end your best bet will be to play with the settings until you get results you are happy with (and of course, those settings/results may not be the same as someone else would chose, but that's Ok).

 Well as Wade had suggested, I would like to know my SFS parameters are right on. Actually I took some time to calculate them and the script did not save my parameters. 

 

I really would like to rely on SFS as a reference tool.



#6 Ballyhoo

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Posted 20 April 2019 - 06:17 PM

Here is my current SFS report. perhaps I need to just accept the #s and move on



#7 Ballyhoo

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Posted 20 April 2019 - 06:20 PM

Here is my current SFS report. perhaps I need to just accept the #s and move on

 

 

Edit

 

I think we touched on the before but cropping my images to remove the parts portion of the image not corrected by a flattner, reduces the eccentricity values.

 

Maybe the barlow is why my eccentricy values are high. The images from a night without the barlow has lower ecc values.

 

But again, weighing everything, I know the gurus would say "no barlow."  But I cannot escape the notion of better FOV and resolution.

Attached Thumbnails

  • SFS.gif


#8 StephenW

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Posted 20 April 2019 - 06:29 PM

OK - so are you only asking about your system parameter settings (as shown in your screen shot) or about the various "quality selection" criteria (e.g. as under the Star Detection Parameters)?

 

Obviously your system parameters need to be set to match your specific set-up.  The "quality" parameters are subjective. 

 

And again, when you state:  "I do not like the results.", what do you mean?  You think the measured results for each sub-frame are incorrect?  Something else??



#9 scadvice

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Posted 20 April 2019 - 06:31 PM

Are you using Flats???



#10 Ballyhoo

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Posted 20 April 2019 - 06:32 PM

OK - so are you only asking about your system parameter settings (as shown in your screen shot) or about the various "quality selection" criteria (e.g. as under the Star Detection Parameters)?

 

Obviously your system parameters need to be set to match your specific set-up.  The "quality" parameters are subjective. 

 

And again, when you state:  "I do not like the results.", what do you mean?  You think the measured results for each sub-frame are incorrect?  Something else??

 

I do not like the results, IE, eccentricity is too high in some frames and I think that might be because of the Barlow lens.   Incidentally I had taken some pics from random astrobin images, saved them as JPEG and ran them in SFS and I the eccentricity values are bw .4 and .6.

 

But in the last half hour I have double checked my parameters and I Think they are correct.



#11 Ballyhoo

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Posted 20 April 2019 - 06:33 PM

Are you using Flats???

Not in these images. Are you going to tell me " you should be using flats."    ?



#12 StephenW

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Posted 20 April 2019 - 06:45 PM

>I do not like the results, IE, eccentricity is too high in some frames and I think that might be because of the Barlow lens

 

If you think the eccentricity is due to some optical aberration (i.e. caused by your barlow), then:

 

- Have a close look at one of your captured frames and check whether the stars look the same in the center and in each of the corners.  If the stars are the same across the full frame then it is likely not an optical issue and the high eccentricity is likely due to bad guiding (mount tracking issues) or some other mechanical issue.

 

- Take an image without the barlow and do the same check.


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#13 fmeschia

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Posted 20 April 2019 - 06:55 PM

It seems to me that the solution to a part cut too short is not to use a different ruler to measure it. Tweaking the parameters of SFS may give you some temporary satisfaction in looking at “better” numbers, but it doesn’t change the underlying reality of the image.

By the way, the main problem I see in the image you posted is not one you can find via SFS: it has walking noise. Which happens if you don’t dither.

Francesco


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#14 StephenW

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Posted 20 April 2019 - 07:03 PM

Ok, just had a look at the images in your dropbox folder - you have coma.  The stars in the center of your field actually look pretty good (nice and round), but the ones off to the edge are flared. 

 

I don't think you're going to get a better overall eccentricity measure without adding a field flatner (as you apparently realized yourself back in this post: https://www.cloudyni...ain/?p=9286777)


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#15 CharlesW

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Posted 20 April 2019 - 07:10 PM

Load your system parameters into SFS. Drag the triangle onto your desktop. That will save your parameters. Rename the new instance and then save it under the Process menu button. Next time you use SFS, open the saved file from Processes. 


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#16 Ballyhoo

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Posted 20 April 2019 - 07:12 PM

It seems to me that the solution to a part cut too short is not to use a different ruler to measure it. Tweaking the parameters of SFS may give you some temporary satisfaction in looking at “better” numbers, but it doesn’t change the underlying reality of the image.

By the way, the main problem I see in the image you posted is not one you can find via SFS: it has walking noise. Which happens if you don’t dither.

Francesco

I have not even scratched the surface then because I do not know the first thing about dithering. As far as dithering, I am a dithering idiot.



#17 Ballyhoo

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Posted 20 April 2019 - 07:14 PM

Ok, just had a look at the images in your dropbox folder - you have coma.  The stars in the center of your field actually look pretty good (nice and round), but the ones off to the edge are flared. 

 

I don't think you're going to get a better overall eccentricity measure without adding a field flatner (as you apparently realized yourself back in this post: https://www.cloudyni...ain/?p=9286777)

EDIT (delete),

 

read your post again Stephen.

 

 

I agree that the flattner is going to improve the edges, but I just need to be sold on one, that the edges are important versus just cropping.

 

 

I might like to have a separate thread just on the use of barlows because I have unsettled ideas about them. The visual me wants to get up closer with the object and aim for better detail.

 

Stephen thank you so much for taking the time to check the images in my dropbox!


Edited by Ballyhoo, 20 April 2019 - 07:36 PM.


#18 StephenW

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Posted 20 April 2019 - 07:50 PM

>What do you think about the 2x barlow?  Do I really need to dump it?

 

I personally only use a barlow when imaging planets :).  But it's a free country so you should do whatever works best for you. 

 

 

>Telescope:  Orion eon, 85MM FL 560 mm (6.6)

>(the linked subs were imaged also with use of 2x barlow.)

...

>So the Harlow didn't mess things up then?

 

The fits images in your dropbox folder are not from a barlowed 85mm f/6.6 - the field of view is completely wrong - so I can't comment on whether the barlow messed them up or not.  


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#19 Night shift

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Posted 20 April 2019 - 07:51 PM

  Here we go on the Barlow again! Your phishing for someone to agree with you so you can justify using one. Did it help? Its entirly up to you what to use in the long run. I admire your tenacity to learn this hobby. I realy do, You should be much further ahead by now. So whats not clicking that we can help you with.  That being said it was months ago, if not last year you asked about flats, darks and so forth. And yet you are not doing it. Stop putting the cart before the horse. Why process without them? You are learning bad habits. Read and listen!  Truthfully, I believe you may have an easier time with EAA .

 

Good luck.  


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#20 zakry3323

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Posted 20 April 2019 - 08:01 PM

 

I might like to have a separate thread just on the use of barlows because I have unsettled ideas about them. The visual me wants to get up closer with the object and aim for better detail.

 

This seems like a good idea to me. I'm not the most knowledgeable imager, but here's my experience, for what it's worth 

 

I'm looking at the OTA's that you have listed, and if you're interested in imaging DSO's, I'm not sure how any of them could benefit for barlowing. 

 

I understand how it feels to be frustrated when you're not getting the detail that you're looking for. Any of your ota's are capable of providing a lot more detail than what you're seeing in your photos. It's comes with getting good weather conditions, taking more subs, having great focus throughout the imaging session, and guiding well. If any of the previous is lacking, image quality will suffer. Decreasing the image scale with a barow is increasing the challenge of getting a sharp, contrasty, detailed end result pretty drastically, even if it was perfectly corrected for your optics. 


Edited by zakry3323, 20 April 2019 - 08:12 PM.

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#21 Ballyhoo

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Posted 20 April 2019 - 08:15 PM

>What do you think about the 2x barlow?  Do I really need to dump it?

 

I personally only use a barlow when imaging planets smile.gif.  But it's a free country so you should do whatever works best for you. 

 

 

>Telescope:  Orion eon, 85MM FL 560 mm (6.6)

>(the linked subs were imaged also with use of 2x barlow.)

...

>So the Harlow didn't mess things up then?

 

The fits images in your dropbox folder are not from a barlowed 85mm f/6.6 - the field of view is completely wrong - so I can't comment on whether the barlow messed them up or not.  

I would have sworn that I fit a 2x Televue Big Barlow on my optical train with that set of images.  But you are saying the FOV does not match that?  Maybe it was so dark I thought I had the barlow and somehow I did not.   



#22 Ballyhoo

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Posted 20 April 2019 - 08:26 PM

 You should be much further ahead by now.

With all due respect that is completely incorrect statement. I am not in a race'I am having my own set of experiences in this hobby that suit me because it is my pursuit. And perhaps I just put into text thoughts and ideas I have, about barlows, etc to broaden my and others understanding. You are  a really nice guy but please be careful with discouraging statements because they are, well, irrelevant. 

 

Oh and the other statement I think it is the poster Zak(?)

 

I am not discouraged about lack of detail. But again,  coming from a visual past, I want to get closer to my object. That is not coming from a place of frustration, but from a place of, like I said, wanting to be close® to my object.

 

Maybe there are logistical or practical reasons for example that I did not have flats available for the set of frames on that night.  But it is really nothing that should be up for discussion. 


Edited by Ballyhoo, 20 April 2019 - 08:28 PM.


#23 WadeH237

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Posted 20 April 2019 - 08:28 PM

Wow, that went sideways fast...

 

Anyway, I took a look at one of your subs.

 

To get an accurate image scale, I plate solved it.  For some reason, the ImageSolver script failed to solve it, so I used PhotometricColorCalibraton.  To get it to work, I converted the image to the RGB color space, because that's a requirement of PCC (I could have debayered it).  I used the Search Coordinates button and used M65 as the target object.  Then I entered 560 as the focal length and 4.63 as the pixel size.  The date is not hugely important, so I just change the year to 2019 and didn't worry about the month and date (it would have worked, even if I left the year at 2000).

 

I then applied the process to the image.  I let it run until the solution was done and then aborted it.  Here is a paste from the Process Console window that has the information I was looking for:

 

Loading image: w=4144 h=2822 n=1 Gray UInt16
7 image properties
48 FITS keyword(s) extracted.
* Loaded astrometric solution:
Reference matrix (world[ra,dec] = matrix * image[x,y]):
+4.44020578e-04  +1.67690806e-04  -1.15661383e+00
-1.67509829e-04  +4.44012659e-04  -2.79412742e-01
WCS transformation ...... linear
Projection .............. Gnomonic
Projection origin ....... [2071.989700 1410.976400]px -> [RA: 11 19 00.097  Dec: +13 17 17.55]
Resolution .............. 1.709 arcsec/px
Rotation ................ -159.324 deg
Transformation errors ... ex=9.55e-12 ey=2.5e-12 px
Observation date ........ 2019-04-11 08:56:59
Focal distance .......... 558.96 mm
Pixel size .............. 4.63 um
Field of view ........... 1d 58' 0.2" x 1d 20' 21.5"
Image center ............ RA: 11 19 00.099  Dec: +13 17 17.58
Image bounds:
   top-left ............. RA: 11 14 15.242  Dec: +13 00 21.97
   top-right ............ RA: 11 21 47.945  Dec: +12 18 49.82
   bottom-left .......... RA: 11 16 10.901  Dec: +14 15 38.41

   bottom-right ......... RA: 11 23 45.613  Dec: +13 33 53.35

 

The important part of this for determining FWHM is the resolution of 1.709 arcsec/px.  This is the number that you use as the Subframe Scale in SubFrameSelector.

 

Next, I ran the FWHMEccentricity script.  I've pasted the output here.  The important parts are Median FWHM of 4.498px and Median Eccentricity of 0.6592.  With a little math, we can see that the FWHM in arc seconds is 4.498 * 1.709, or 7.7687 arc seconds.  I then ran SubFrameSelector on this image and it evaluated it as 9.2334 arc seconds.

 

Note that this is not quite an apples to apples comparison.  The FWHMEccentricity script computes the median, while SubFrameSelector computes a weighted mean.  For the mean to be larger than the median, it means that you probably have some pretty large stars in the corners that are bringing up the mean.

 

In any case, as a final reality check, I created a preview of M66 and extracted the debayered luminance, and found the focus to be pretty soft.  So I think that an assessment of FWHM between 7 and 9 arc seconds is probably correct.

 

Oh, and SubFrameSelector computed 0.6295, so pretty close to the FWHMEccentricity script.

 

If you want to explore the difference between the mean and median FWHM values, you could try debayering the original FITS, cropping it to a square that eliminates the corners and edges of the original, extract the luminance, and run both the script and SFS again.  I would bet that the FWHM values are closer.

Attached Thumbnails

  • FWHMEccentricity.jpg
  • M66_preview.jpg

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#24 Night shift

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Posted 20 April 2019 - 09:03 PM

 Ballyhoo,  I am sorry if I stepped on your toes. Hope it all comes together for you. 


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#25 Ballyhoo

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Posted 20 April 2019 - 10:27 PM

Wow, that went sideways fast...

 

Anyway, I took a look at one of your subs.

 

To get an accurate image scale, I plate solved it.  For some reason, the ImageSolver script failed to solve it, so I used PhotometricColorCalibraton.  To get it to work, I converted the image to the RGB color space, because that's a requirement of PCC (I could have debayered it).  I used the Search Coordinates button and used M65 as the target object.  Then I entered 560 as the focal length and 4.63 as the pixel size.  The date is not hugely important, so I just change the year to 2019 and didn't worry about the month and date (it would have worked, even if I left the year at 2000).

 

I then applied the process to the image.  I let it run until the solution was done and then aborted it.  Here is a paste from the Process Console window that has the information I was looking for:

 

Loading image: w=4144 h=2822 n=1 Gray UInt16
7 image properties
48 FITS keyword(s) extracted.
* Loaded astrometric solution:
Reference matrix (world[ra,dec] = matrix * image[x,y]):
+4.44020578e-04  +1.67690806e-04  -1.15661383e+00
-1.67509829e-04  +4.44012659e-04  -2.79412742e-01
WCS transformation ...... linear
Projection .............. Gnomonic
Projection origin ....... [2071.989700 1410.976400]px -> [RA: 11 19 00.097  Dec: +13 17 17.55]
Resolution .............. 1.709 arcsec/px
Rotation ................ -159.324 deg
Transformation errors ... ex=9.55e-12 ey=2.5e-12 px
Observation date ........ 2019-04-11 08:56:59
Focal distance .......... 558.96 mm
Pixel size .............. 4.63 um
Field of view ........... 1d 58' 0.2" x 1d 20' 21.5"
Image center ............ RA: 11 19 00.099  Dec: +13 17 17.58
Image bounds:
   top-left ............. RA: 11 14 15.242  Dec: +13 00 21.97
   top-right ............ RA: 11 21 47.945  Dec: +12 18 49.82
   bottom-left .......... RA: 11 16 10.901  Dec: +14 15 38.41

   bottom-right ......... RA: 11 23 45.613  Dec: +13 33 53.35

 

The important part of this for determining FWHM is the resolution of 1.709 arcsec/px.  This is the number that you use as the Subframe Scale in SubFrameSelector.

 

Next, I ran the FWHMEccentricity script.  I've pasted the output here.  The important parts are Median FWHM of 4.498px and Median Eccentricity of 0.6592.  With a little math, we can see that the FWHM in arc seconds is 4.498 * 1.709, or 7.7687 arc seconds.  I then ran SubFrameSelector on this image and it evaluated it as 9.2334 arc seconds.

 

Note that this is not quite an apples to apples comparison.  The FWHMEccentricity script computes the median, while SubFrameSelector computes a weighted mean.  For the mean to be larger than the median, it means that you probably have some pretty large stars in the corners that are bringing up the mean.

 

In any case, as a final reality check, I created a preview of M66 and extracted the debayered luminance, and found the focus to be pretty soft.  So I think that an assessment of FWHM between 7 and 9 arc seconds is probably correct.

 

Oh, and SubFrameSelector computed 0.6295, so pretty close to the FWHMEccentricity script.

 

If you want to explore the difference between the mean and median FWHM values, you could try debayering the original FITS, cropping it to a square that eliminates the corners and edges of the original, extract the luminance, and run both the script and SFS again.  I would bet that the FWHM values are closer.

Dude, it is going to take me a long time to digest all of that because you are light years ahead of me

particularity in PI.   I did not know t that PI can plate solve using PCC etc..

 

Great info...




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