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PI flat calibration


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Having embarked on the rather mountainous learning curve that is PI processing I have found that I am not getting the expected results out of my calibration frames.

When I use flats in DSS it removes the dust bunnies and gradients from the lights, in PI this doesn't seem to be happening.

I have tried manually calibrating and integrating them which was a complete failure so I then tried batch post processing which happily calibrated and integrated the frames but the flats didn't appear to do their job as I still have a gradient (that is also visible in the raw flat) and dust bunnies. I opened the master flat that PI made and it was really dark, I had to stretch it to see anything. The raw flats were 50% exposed.

Anyone have any idea what I am doing wrong?

I don't think it is the raw data at fault as DSS seems happy with it.

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Having embarked on the rather mountainous learning curve that is PI processing I have found that I am not getting the expected results out of my calibration frames.

When I use flats in DSS it removes the dust bunnies and gradients from the lights, in PI this doesn't seem to be happening.

I have tried manually calibrating and integrating them which was a complete failure so I then tried batch post processing which happily calibrated and integrated the frames but the flats didn't appear to do their job as I still have a gradient (that is also visible in the raw flat) and dust bunnies. I opened the master flat that PI made and it was really dark, I had to stretch it to see anything. The raw flats were 50% exposed.

Anyone have any idea what I am doing wrong?

I don't think it is the raw data at fault as DSS seems happy with it.

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What are the camera and the illumination level for the flats? I find that PI is superior to DSS in every way.

A.G

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Yes I expect it is, I just need to work out how to use it properly ;)

Camera is a Fuji finepix S5 Pro, histogram for the raw flats is about half way exposed on all channels.

When I view the raw flats they are light grey with black splodges and a darker area at one side. The DSS master flat looks identical to the raw ones. The PI master flat is black unless stretched.

Is it normal for it to look like that?

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Yes I expect it is, I just need to work out how to use it properly ;)

Camera is a Fuji finepix S5 Pro, histogram for the raw flats is about half way exposed on all channels.

When I view the raw flats they are light grey with black splodges and a darker area at one side. The DSS master flat looks identical to the raw ones. The PI master flat is black unless stretched.

Is it normal for it to look like that?

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Here is a master flat from my Atik 428EXC, WO Star71 and Baader UHC-S. No stretch has been appliedIt was taken using an Aroura Panel with a white T shirt on the scope and the ADU value was about 23000 or about 2/5th of way on the histogram all acptured using NEB3. If the Flat is dark then some setting not correct.

post-28808-0-87199800-1412100284_thumb.j

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Hmm yeh mine look like that when they come from the camera but once PI gets hold of them they go black.

I wonder if it has something to do with the 14bit camera data in a 16bit raw package?

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

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Hmm yeh mine look like that when they come from the camera but once PI gets hold of them they go black.

I wonder if it has something to do with the 14bit camera data in a 16bit raw package?

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

This one is from my modded canon 1100d, it does look darker but the ADU was slightly lower at about 20000 ADU for fear of over correction. PI still corrected the subs quite well. May I ask how many flats did you take , I normally take about 50+ and times about 100. I am not sure if it makes a difference but was worth mentioning. All my DSlR subs are taken either in FITS or RAW format.

A.G

post-28808-0-35190800-1412160941_thumb.j

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I had 20 flats, I will be taking new ones now since I just cleaned the CCD, there was way too much dust on it.

Maybe the dust was just to much to correct for, the lights were well dithered though so I would have thought it could manage.

It doesn't explain why there was still a gradient though as this is clearly present in the flat and light frames.

All my subs are raw (.raf) as other than JPEG that is all my camera will take.

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Here is a master flat from my Atik 428EXC, WO Star71 and Baader UHC-S. No stretch has been appliedIt was taken using an Aroura Panel with a white T shirt on the scope and the ADU value was about 23000 or about 2/5th of way on the histogram all acptured using NEB3. If the Flat is dark then some setting not correct.

The flat in this post isn't debayered. Does that get taken care of at some point?

Olly

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Ok I've had a faff around and managed to solve a few issues, my flats are still really dark but they seem to solve the small dust bunnies. Bigger ones I can remove with low range clipping since on a 5 min exposure there really shouldn't be anything that dark. Cleaning the CCD helped a lot too.

I've been debayering between calibration and registration as otherwise I seem to get poor results.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

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