Comet Schwassmann - Wachmann 3/73P

M57/Ring Nebula Flyby

Fragmenting Comet in Lyra

Uploaded 5/7/06

This close alignment between a naked eye comet and a far more distant planetary nebula provided a unique opportunity to develop a processing technique which used ONLY global stack processing to the images taken during the event to yield the final result. Consider this technique something to try on your images, and you may find the result is both pleasing and accurate.

Here's The Problem: A stationary deep sky object (The Ring Nebula and stars) are to be combined with a rapidly moving comet. Both need long exposure times to yield a deep noise free image, and yield accurate colors. Lets first start by showing you my final result, The comets actual image stack is stationary on the true star field, taken at the SAME time:

The dusty yellow comet with its diffuse dust tail, appearing sharper on the top edge contrasts in color to the blues and reds of the hydrogen emissions of the tiny disk of the planetary nebula, to its left. See the larger images for the details on this planetary nebula.

C Fragment Select an image size for a larger view: 1024 x 768 1600 x 1200
This is the series of image stacks that when properly stacked again using the correct combine math, will yield the final image presented above.
 This is a normal star aligned image of all 18 frames, each one minute exposure each. The comet has moved from left to right and is apparently speeding away from the planetary at a rate of over 1 degree per day. You can see that the comet is quite yellow in color from dust.
 In this image, the 17 stack above was combined using darken to produce a low noise, and the moving comet was automatically replaced by the sky from the other frames. Next, we combine this 17 stack frame with the first single frame using the lighten combine method. This yields one first comet image as it was exposed, suspended in a rich star field.
 Next, the original 17 images were combined with the comets nucleus in register in Maxim DL using Median combine. This results in the removal of the trailed stars and leaves only the comets image stacked 17 times for a dense and colorful image.

The stack of 17 comets is registered directly onto the comets nucleus in the second image above (the 18th frame) automatically using a 1 star automatic centroid alignment, to remove any human factors and the combine type is set to Lighten. This has the result (since the backgrounds are set exactly the same) to sum in the remaining exposures onto the first image in a complete registered stack.

Instrument: Stellarvue SV80s with TR2008 Focal Reducer/FF Platform: Astrophysics 1200 QMD CCD Camera: Canon 10D unmodified Guider: none Exposure: 18x1m each to avoid trailing of comet against stars Location: Payson, Arizona Elevation: 5150 ft. Sky: 8, Transparency 6/10 Outside Temperature: 45 F Processing Tools: Maxim DL, Photoshop, PixInsight HOME GALAXIES EMISSION NEBS REFLECTION NEBS COMETS GLOBULARS OPEN CLUST PLANETARIES LINKS


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