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January, 2012:

Another Mosaic Test

Still working hard on this. Getting there…

This is the first large mosaic I’ve ever worked on and it is quite a tough one. Still working on getting all the background gradients in each frame squared away, you can still see the seam areas. I need to get more data for some of the frames, nearly every session was plagued by high winds. Some frames have 100 minutes of integration time, others have 20.

I’ve learned a few lessons throughout this process.

  • Framing. I went for 15% overlap, looks like 20% would have been a better choice. Each session you should plate solve with the center image to make sure positioning and camera rotation are dead on.
  • Flats. Take them after every session. Just do it.
  • Throw away any subs with gradients that differ from the rest of the subframes in the particular frame.
  • Do not take any photos near the horizon. Frames taken below 45 degrees altitude have very difficult gradients to get under control. Seems like I should just give myself a four hour window when the object is nearest the meridian to capture the frames.
  • Pixinsight’s DBE tool is your second best friend. GradientMergeMosaic is your 1st.

Rosette Nebula



Image Location and Date: SDAA dark sky site at Tierra Del Sol on December 31st, 2011
Object: Caldwell 49: The Rosette Nebula.
Mount: Orion Atlas EQ-G
Imaging scope: Tair-3C
Imaging FL: 300mm
Imaging focal ratio: f4.5
Imaging camera: Modified Canon 350D
Lights: 17 x 600sec @ ISO 800 in Hydrogen-Alpha, 13 x 600sec RGB
Calibration: Darks
Guide scope: 9×50 Finder with Orion StarShoot Auto Guider
Other details: guiding with PHD, captured with APT, stacked in Deep Sky Stacker, processed in PixInsight.