IC4954 & IC4955
IC4954 and IC4955
Reflection Nebulae in Vulpecula

Click here for uncropped versions: 25% (994x967) 40% (1590x1546) 65% (2584x2513) 100% (3976x3866)


IC4954 and IC4955 are the nebulae (gas/dust clouds, so appear fuzzier than stars) near the center of the image (this photo is severely cropped from the original, and shown at about 65% of full resolution; you can click the links above the image to see four diffrent sizes of the uncropped field); IC4954 is the nebula higher in this photo, appearing to be vertical, while IC4955 is just below and to the left of IC4954, appearing to be horizontal. This field is located in the constellation Vulpecula, around 6500 light years from us (so the full field of this photo--in the uncropped versions--is about 65 light years across at that distance) Each nebula is about 7 light years long (to put that in perspective, a light year is about 63,000 times the distance from our sun to the earth).

Research has shown a continuing cycle of star formation here over three stellar generations. Astronomers believe that these types of high density molecular clouds often become star-forming regions after supernova explosions when intense radiation from young high-mass stars sweeps the interstellar material together into these (relatively) high-density regions. The arc-like structures of IC4954 and IC4955 each is formed by a young-massive star (not seen in the image) at the centre of the nebulae, sweeping material outward by its strong radiation pressure. The shock-wave is particularly evident in the sharp right edge of IC4954. Where the dust has been blown away, we can see a denser swarm of background stars (again particularly evident to the right of IC4954 in this image). The star cluster this star-forming has created is known as Roslund 4, which should not be confused with the entire dense star field of this image--the image is in the midst of the Milky Way as seen from earth, so any photo of it from earth will include a myriad of stars not associated with the object. This also explains the reddish hue of so much of the field (especially the fainter stars), since the intervening dust scatters the blue light more than the red light.

I love dense star fields, and showing objects in the greater context of the region, so (in addition to this cropped image), I have presented four sizes of the uncropped version.


Technical Information:

LRGB: 555:180:225:165 (a total of over 18 hours of light-frame exposure time); all were all 15-minute exposures.

Equipment: RC Optical Systems 14.5 inch Ritchey-Chretien carbon fiber truss telescope, with ion-milled optics and RCOS field flattener, at about f/9, and an SBIG STX-16803 camera with internal filter wheel (SBIG filter set), guided by an SBIG AO-X, all riding on a Bisque Paramount ME German Equatorial Mount.

Image Acquisition/Camera Control: Maxim DL, controlled with ACP Expert/Scheduler, working in concert with TheSky X.

Processing: All images calibrated (darks, bias and sky flats), cosmetically-corrected, aligned, combined and cropped in Pixinsight. Color combine in Pixinsight. Some finish work (background neutralization, color calibration, deconvolution, lessening the dynamic range and noise reduction) done in Pixinsight; some cleanup finish work was done in Photoshop CC.

Location: Data acquired remotely from Deep Sky West Remote Observatory, Rowe, New Mexico, USA.

Date: Images taken on many nights in September 2019. Image posted October 28, 2019.

Image scale of full-resolution image: 0.56 arcseconds per pixel.

Seeing: Quite variable over the course of the month, with individual subexposures varying from 1.7 arcsecond FWHM to 2.7 arcsecond FWHM; integrated luminance layer was deconvolved to 1.5 arcsecond FWHM.

CCD Chip temperature: -25C

Copyright 2019 Mark de Regt

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