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zero signal when trying to create masterflat in PI

astrophotography beginner dslr
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#1 peyoter

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Posted 23 September 2020 - 07:11 AM

Hello everybody.

I'm having a problem while trying to callibrate/stack/integrate my images in Pixinsight (first time, normally use Deepskystacker). I am following a tutorial on the light vortex astronomy site, I want to do the one with andromeda captured with a dslr but I am still working on the basics (https://www.lightvor...t.html#Section3).

I have have:

131 light subs of 1 min each

191 bias frames

30 darks

42 flats

 

first problem I run in to is with the superbias, if i do that step my result is significantly different. Al lot of streaks instead of some kind of evenly distributed 'signal/noise'. (having a hard time explaining lol)

After that is the imagecalibration of the darks, then integration of callibrated darks.
next up, imagecal of flats process runs till the end but those frames are just black? and imageintegration of those flats won't even succeed. I get the message that there is zero or insignificant signal so the process just stops.
i Have tried different flats and bias frames and started all over but everytime the same result. I have searched around but can't find anything that helps me or is understandable to me. Something about pedestals? Probably did something wrong in the beginning I suppose?

 

 



#2 clint.ivy

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Posted 23 September 2020 - 08:34 AM

Can you share/post a few of your subs for flats/darks/bias? Also, the integrated bias / superbias?



#3 peyoter

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Posted 23 September 2020 - 11:11 AM

trying like this

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  • Schermopname (4).png
  • Schermopname (5).png


#4 peyoter

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Posted 23 September 2020 - 11:15 AM

single stretched flat

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  • flat.png


#5 peyoter

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Posted 23 September 2020 - 11:20 AM

master bias and superbias, don't know if it a bit clear to see in such a small size

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#6 clint.ivy

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Posted 23 September 2020 - 11:26 AM

Hard to tell without being able to inspect the RAWs. What’s the histogram on the flat look like? What was the exposure time? 

 

Found this thread on pix insight forums, if you’re mixing debayered and non-debayered files that could be the problem. (Seems like your flats are not debayered based on the screen shot) https://pixinsight.c...258/#post-92679



#7 peyoter

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Posted 24 September 2020 - 01:20 PM

is there a way to post my RAWs? would be happy to share off course.

And is there a way to view my histogram in PI?
yes my flats... in the tutorial they made me change a setting in PI so I was thinking I would be doing something... this is what the tutorial said:

"If you are dealing with DSLR RAW colour images, you should change some image file format settings on PixInsight before you start. To access the relevant settings, click Format Explorer to the left of PixInsight and double-click the DSLR_RAW entry near the top.

 

By default, PixInsight reads DSLR RAW colour images as Debayered images, meaning it is artificially altering them to display them in colour within PixInsight. This may seem convenient as it is done automatically but technically, DSLR RAW colour images need to be calibrated while purely in their RAW state, prior to any alterations such as Debayering. Simply click the Pure Raw button on the bottom-left of the settings window and you will be set - click OK afterwards.

 

PixInsight will remember these settings for the future so you will not need to change this again. Please note that now opening DSLR RAW colour images in PixInsight will display them in monochrome, such as is the RAW image data. Once the images are calibrated, we will be converting them to colour images by Debayering them so do not worry about this."

 

But I have tried just now to debayer my flats first and then tried the calibration en integration again but integration still failed
 



#8 clint.ivy

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Posted 24 September 2020 - 01:53 PM

is there a way to post my RAWs? would be happy to share off course.

And is there a way to view my histogram in PI?
yes my flats... in the tutorial they made me change a setting in PI so I was thinking I would be doing something... this is what the tutorial said:

"If you are dealing with DSLR RAW colour images, you should change some image file format settings on PixInsight before you start. To access the relevant settings, click Format Explorer to the left of PixInsight and double-click the DSLR_RAW entry near the top.

 

By default, PixInsight reads DSLR RAW colour images as Debayered images, meaning it is artificially altering them to display them in colour within PixInsight. This may seem convenient as it is done automatically but technically, DSLR RAW colour images need to be calibrated while purely in their RAW state, prior to any alterations such as Debayering. Simply click the Pure Raw button on the bottom-left of the settings window and you will be set - click OK afterwards.

 

PixInsight will remember these settings for the future so you will not need to change this again. Please note that now opening DSLR RAW colour images in PixInsight will display them in monochrome, such as is the RAW image data. Once the images are calibrated, we will be converting them to colour images by Debayering them so do not worry about this."

 

But I have tried just now to debayer my flats first and then tried the calibration en integration again but integration still failed
 

1. So on the topic of sharing, you could upload your RAWs to google drive, One Drive, Dropbox, etc and then post the share link here.

2. Process —> All Processes —> Histogram Transformation (Make sure to select the appropriate View and hit the checkbox button at the lower right hand corner of the HT window to ‘track view’ (Photoshop would be better because it breaks out the RGB channels in a single or stacked view and PI doesn’t as far as I know)

3. Setting file handling for RAWs to Pure Raw is a critical step but only one of them. I’m familiar with the Light Vortex tutorial and I believe you’re missing the step where you actually debayer the flat files (either through the enable CFA checkbox or manually running the debayer process).

 

I’d also recommend running the Weighted Batch Pre Processing script (Script —> Batch Processing—> WeightedBatchPreprocessing) and let it do all the work. This will give you a quick-ish result Just make sure to enable CFA and Optimize darks



#9 peyoter

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Posted 26 September 2020 - 05:00 AM

thank you for the reply and suggestions. thanks to you I found the problem. I was using RAW files in combination with darks that I took with the asiair, so they were fits files. I took new darks with just the dslr and it was fixed banjodance.gif
I have been able to continue the tutorial until after the drizzle integration. But It seems I did something wrong with subtracting or dividing my master flat? I'm uploading the master flat and drizzle integrated files to my google drive so I can share them.

It looks like my master flat didn't do anything confused1.gif



#10 peyoter

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Posted 26 September 2020 - 05:11 AM

Master Flat

https://drive.google...iew?usp=sharing

 

Drizzle integrated

https://drive.google...iew?usp=sharing



#11 clint.ivy

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Posted 26 September 2020 - 02:03 PM

Hey Peyoter,

thanks for sharing the FIT files.

Ok, so first it looks (to me) like the flat was applied exactly as one would expect. If you boost both with STF you can see that the dark/light pattern in the flat is reflected in the drizzle file (bright areas in the flat become dark areas in the master light, etc).

 

2020-09-26_11-44-40-m.png

 

I'm worried that the flat was not debayered correctly (see the cross hatch pattern, that's usually indicative of the CFA).

I'm curious as to why the master light is in the gray color space, you didn't mention if you shot this as OSC or seperate channels?.

 

Also, do you have a specific reason for using FIT over XISF (other than that's what you're used to because of your ASAIR)?

 

There's obviously a problem somewhere in your imaging train, but determining it is beyond my skill level (I only ever shoot DSLR and have never run across issues like this).

 

I would strongly recommend posting to the PixInsight forums, there are a lot of folks more knowledgeable than I there including the software engineers who tend to be heavily engaged with the community.

 



#12 peyoter

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Posted 27 September 2020 - 12:44 AM

My first set of darks was taken with the asiair, and were FITS files. But that was why there was the 'no signal' error.
So now I am only using CR2 files with my dslr. I don't know why there would be problem with the debayering, I am completely new to PI... But in the tutorial they don't debayer the flats, they do that step with the calibrated and cosmetticaly corrected lights. But I still find it weird because at the end of the turorial I have my drizzleintegration file but that still has no colour? I'm confused... can't wait till I finally know PI enough the do things without constant tutorials hehehe.



#13 clint.ivy

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Posted 28 September 2020 - 11:37 AM

Ok, so the big issue here is that you always have to debayer your OSC images. The vortex academy tutorials come from a place of single channel images so while they try to remember and mention where OSC issues come into play, sometimes they miss.

 

All that to say, I think your master light is in grayscale because of a bayer/debayer mismatch.

 

You don't mention what kind of DSLR you have but CR2 is a Canon file extension. There are two things to consider here 1) what is the CFA pattern and 2) where do the axes originate (where is 0/0 in the file). So make sure to get those details for your camera (if you don't already have them). I encountered this recently when processing some data provided by backyardastronomer. I wasn't aware that I needed to deselect 'up-bottom' in the WBPP script and I didn't know the CFA pattern was NOT the usual RGGB. CFA Pattern detection in the latest release of PI is good, but it can still fail so it's often better to explicitly assign the CFA pattern rather than relying on PI to detect it correctly.

 

If it were me, and it has been me -- I started with the LV tutorials because I wanted to understand the process. (and I wasn't using WBPP), I would first debayer all of the images using the Debayer process (Process --> All Processes --> Debayer) and then proceed with the LV tutorial on the already-debayered files. All you to do then is ensure that any CFA options are disabled when you run a process.

 

FWIW, I only started with PI three months ago and have made more mistakes than I can remember but, if you provide all your subs, I'll happily run the LV tutorial in parallel with you and we can compare notes...

 

you can DM me if you'd rather keep your data private.



#14 peyoter

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Posted 02 October 2020 - 10:30 AM

Hello, thanks again for the reply.

I'm using a canon 700D, so it is RGGB as CFA pattern.
But I don't really know what you mean with where the axes originate...

 

So if I understand correctly, I should load al my frames into PI and debayer all of them? Flats, Bias, Darks, and Lights? all before doing anything else?

I'm going to try it out as soon as I have some time to actually get something done. I'm currently fighting water in my house, unfortunately...



#15 clint.ivy

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Posted 02 October 2020 - 11:32 AM

@peyoter, oh man. Sorry to hear your house is having water problems!

 

1. Yes, Debayer all of your subs.

If you're committed to running pre-processing manually (and I totally understand that) then run the debayer process manually. I'd recommend running it separately for each type (lights, darks, flats, bias) so you can store them in separate directories or with different file naming.

 

2. You can imagine your sensor as a 2-D graph with a vertical axis and a horizontal axis ... this means it has an origin (0/0) and image processing software will use that origin to interpret the file -- if we get it wrong the image will not be interpreted correctly and (for instance) totally mess up the debayer process. In most amateur camera control apps, the origin is at top left but in professional cameras, the origin is bottom left. Honestly this only seems to matter when you are using either the batch pre-processing script or the weighted batch pre-processing script so keep in in the back of your mind for later.



#16 alphatripleplus

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Posted 04 October 2020 - 08:12 AM

Moving to CCD/CMOS Astro Camera Imaging & Processing for a potentially better fit.




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