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Image of the day 09/26/2022

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    IC 434, Wolfgang Promper
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    IC 434

    Image of the day 09/26/2022

    Getting plate-solving status, please wait...
      IC 434, Wolfgang Promper
      Powered byPixInsight

      IC 434

      Equipment

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      Acquisition details

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      Description

      A early Horsehead
      This is a fresh processed data set from last winter.
      LRGB 60 30 30 30 min.

      Here is a short writeup about how I aquire and process the data.

      I use ASA´s own observatory automation software "Sequence" to run the sessions.
      Usually I program it during the day and it handles everything, roff automation, mirror covers, telescope fans, and the aquisition of multiple objects.
      All of my LRGB sets are aquired unguided, I only use the guider for exposures longer than 7min.
      I use a fairly high camera gain, with the C3 that is 2750, it is the equivalent of 100 for a ASI camera with the IMX455 sensor.
      I tested unit gain but didn´t really like the results, it sure has a higher full well but the dynamic range is pretty much the same due to the higher  readnoise.

      The internet connection at my site is stable but pretty slow, so I do all the preprocessing on the remote computer and just transfer the masters.
      I still use CCDinspector to select the best subs, if possible I discard anything worse than 1.8" for nebulas, and anything worse 1.3" to 1.4" for galaxies and planetaries.

      I then use Pixinsights batch preprocessing to calibrate and stack, once finished I drop the masters into the OneDrive folder and wait until they are availible here.

      I then do the RGB combination and color calibration in Pixinsight and save it as Fits file, same with the luminance.
      The reason for this is because I do all the stretching in CCDstack, I know its old but to me it has the best visualisation, I then save the streched data as 16bit Tiffs and do the luminance layering in Photoshop.
      I always work with rather dull looking images, so until the end there is no real black and no real white, to avoid any clipping.
      I couple of months ago I started using StarXterminator, so I process the object and the stars independently and later add the stars with screen in PS.
      I rerely use deconvolution, if I do then in Pixinsight but just with parametric PSF, maybe its my ignorance but I´m getting better results this way.
      In Photoshop I use the unsharp mask with layer masks and just brush it on the high snr areas only, this is sometimes a iterative process with different radiuses.

      I´m very careful with noise reduction, we don´t have a lot of high frequencies in our data as we are imaging through the atmosphere  which is a perfect low pass filter.
      The problem is that our brain is used to seeing high frequencies in our everyday life, so if we remove all noise it gives the image an unpleasant look.
      Anyway I use it a bit in that case either Imagonomics Noiseware Professional in PS or NoiseXterminator in PI.
      After that I adjust the histogramm in PS, and enhance the saturation a bit mostly in PI with curves.

      The last step is to downsample the image to a reasonable display size, sometimes I use a bit of wavelet sharpening on the final result.

      One important thing for me is to never overstretch, there is always more information in the data but I never squeeze out all of it to keep an aestethic apearance of the object, at leasI try.

      Wolfgang

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      IC 434, Wolfgang Promper

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      Made in Tivoli/Namibia