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Topics - dpaul

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« on: 2018 February 14 01:51:28 »

Presently I only take darks and bias frames and no flats. This is because I have to return my 30'' scope to a cabin after observing and the width of the entry means I can't leave a camera/filter wheel sticking out sideways, it will get knocked.

I'm aware of the importance of taking flats with the focus position remaining as per the light frame captures, also the camera rotation itself.
So here's my question:

How accurate must this position be? For example if I carefully remove the camera then return it to the scope the following day without adjusting the focuser 'and' noting the rotational position, will that be good enough. The rotation is probably the hardest to replicate but within 1 or 2 degress ok but no if it has to o.1 degrees?



Gallery / LRGB Images with Atik Horizon Mono Camera
« on: 2018 February 13 18:21:16 »
Just wanted to share my attached results of a ''single night of imaging''.

The camera is Atik Horizon Mono (CMOS) and LRGB filter set.
Images are M51, NGC 4565, M13, M100, M99, NGC 2903
Except for M13, all objects were imaged with approximately 20 frames for each filter, 12secs to 15 secs each
M13 only needed 6 second frames
All were 2x2 binning on a high gain setting

The scope is Starstructure Horizon, with amazing 30'' F3.5 optics by Mike Lockwood.
Scope is mounted on Equatorial Platform (by Tom Osypowski), without guiding
Baader 2 element coma corrector (now going to try 4 eleemnt - I have the Paracorr type II).

All processing done in Pixinsight (but still a novice):
0.001 sec bias frames
Dark frames exact match to the light frames
Frames calibrated without subtracting bias from the Master dark
No flats were taken
Stars reduced with MT/star mask
Deconvolution with background sky masked out
TVG de-noise
Each master R, G and B were then combined using Chanel combination, then color corrected using Photometric Color Calibration (worked 4 out of 6 times)
Lum then added using LRGB combination (dragging a new instance from the Lum onto the RGB)
Final stretching, curve adjustment (including saturation level to get stronger color), etc.

Each object is about 1-2 hours work after some practice.

Interestingly, the pixel size is only 3.8 so with a 2667mm focal length so I'm seriously over-sampling, even with 2x2 binning. However the results are not too bad (for me) and hopefully this encourages other novice CMOS users and newcomers to Pixinsight that you can get quite good results.  Also with a big scope you get a ''lot done in one session''.

I'm having fun!

As an example of what's possible, I recently too an image of Hickson 50 and some of the galaxies were Magnitude 20-21 (I couldn't see them visually - my limit is about mag 17).


David (UK)

General / Pixel size / Photometric Color Calibration
« on: 2018 February 11 08:41:03 »
In general I am reasonably familiar with Photometric Color Calibration and more often than not, it works!  However, I've wondering if I'm entering the right pixel size?

I have a CMOS camera and typical use 2x2 binning. I know with CMOS this is software binning not hardware binning (as it for CCD) but should I use 2x the pixel size when color calibrating?



I've started a new topic based on feedback from RICKS in the recent discussion topic ''Colour images come out black and white''.

Up until now I have done LRGB integration by working on R, G, B and L separately then stretching and saving them ''separately''. I then used LRGB combination process with the 4 separate non-linear files.

Rick - I did as you suggested and combined RGB linear files into a single RGB file using channel combination. Then I did colour calibration whilst still linear before saving as a non-linear RGB file. Then I tried to combine this with a non-linear Luminance file using LRGB combination and it doesn't recognise the RGB file at all (not a comptable image).

Am I doing something wrong?



General / Checking for clipped pixels?
« on: 2018 January 21 08:23:26 »
I have a cooled CMOS camera (Atik Horizon) and just wanted to check the offset value was set appropriately. I believe there is a way to check for any pixels below zero in Pixel Math (and possibly Statistics?).

I need a very simple explanation, for example I've seen notes on this before but I need to know exactly where to place an expression or formula (Pixel Math) and what does the output mean.  Statistics looks easier to understand if that can do it too?

All help very much appreciated.



« on: 2017 December 10 09:55:10 »
I've started a new topic to help with some fundamental questions -

I'm currently using a One-shot-color camera (CMOS) and it seems at the moment I can't save data as true RAW (setting DSLR Format Explore as 'pure RAW makes no difference) - whatever is saved comes out as RGB.

So here are some basic questions if the experts can help me:

1/. I believe calibration of light frames with bias, flats and darks is bets done in pre-debayered state (CFA-color filter array), but must it be? Can a result although maybe not ideal be still achieved with RBG files for everything?

2/. Is there a way to convert RGB data to FCA (in PixelMath or Debayer Process?) so essential the reverse what is normally needed?

I only recently started calibrating the light frames. I started last week and and captured Master Bias and Master Darks. The Bias actaully seems to make a big different on the final result so even as an RGB master bias, it seems to be reducing the final noise result. The Darks I'm having more problem where the calibration process says the darks are incompatible with light frames. I reposted the Master Dark which shows a sudden drop off to the left.

Thanks in advance for the help


General / Deconvolution & Bias Frames
« on: 2017 December 05 01:43:12 »
I've been doing basic image processing whilst gradually learning PI. I've always used master dark frames but only just started taking bias frames.
I've experienced something unexpected and want to know why?

Without calibrating the pre-integrated light frames with bias frames - I can use deconvolution on the linear files and it works (to varying degrees) with deranging and no-deranging, although I usually check the box.

Now when calibrating the light frames with bias frames and then applying deconvolution, I get a weird mosaic effect across the whole image (so its unusable). It only happens when I choose deringing and without it, all is fine except for the dark rings (which I don't want).

Can anyone suggest what's going on?

I have one final question.
I took 30 bias frames then integrated them with Image inetegrator and fails to work when I use the defaults Iterative K-sigma setting for the scale estimator
I got it to work only with Percentage bend variance and average absolute deviation from the median.
Is this expected (Its a CMOS chip not CCD).



General / XISF File Conversion
« on: 2017 November 24 01:41:03 »
I have a general question -

The output saved filed from cameras cannot be XISF format (as this is native only to Pixinsight) so if the original data files were TIFF or FITS, is there any benefits of converting these to XISF before processing in Pixinsight. For example do the processes work better or faster or will be the same either way?

I am currently saving FITS files then converting to XISF before processing.

One last question is FITS better than TIFF regarding data quality?



General / Photometric colour calibration
« on: 2017 September 16 14:19:50 »
I read the recent software tutorial explaining the new ''Photometry based colour calibration'' and tried in vain to use it.
I have version 1.8.5 version which has ''Photometric colour calibration'' in the programs menu. I tried using this on various galaxy images that were not yet stretched (and in fits files format). I continually get the same message:

FAILURE TO PLATE SOLVE IMAGE, then in more detail it says:
0 star pair matches found - need at least eight matches pairs
Error - unable to find an initial set of putative star pair matches
Error - the image could not be aligned with the reference star field.

Can someone help - the tutorial doesn't seem to explain how to actually use the program.



General / Stitching images together
« on: 2017 August 01 16:58:03 »

Can anyone help with the following question -
I've got a 30'' F3.5 scope which is great for getting fine detail on individual smaller deep sky object such as M81 but would only capture a fraction of M45.
I'm aware from the past that there were ways to stitch images together to get panoramic shots. Is there an process with PI that allows stitching a mosaic of smaller fields of view to get a big one?



I'm new to this group and have invested in Pixinsight software. I have a monochrome camera from Mallicam (DS16c) but having problems with stacking individual RGB and L images.
I'm taking individual exposures with a luminance filter then a R, G and then B. These are the correct imaging filters from Baader (not visual ones).
I've learnt how to successfully star align the four separate images and also to dynamically crop them. I've also done a histogram transformation to make them non linear (at least I think I have).

The problem occurs when I use colour space then LRGB combination. I open the four image files but it says 'no compatible images'. I've tried xisf, tif, fits formats but still no success.
If I convert each file to gray scale then it works but then I've obviously not getting the right result (although a washed our colour stacked image surprisingly occurs).

I must be doing something fundamentally wrong. I'm using the Mallincam SKY software to capture the images and tried both the RAW and RGB setting when I save the images (RAW is what I usually do). I love the other thing so far that Pixinsight can do after reading lots of helpful advice on this forum and elsewhere - I just need to get past this fundamental problem.


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