Andrew’s Astronomy Blog

I’ve imaged this object before using the Canon 350D in some very early experiments with imaging the night sky. This is the result of narrow band imaging using Ha, OIII & SII filters (3 ten minute exposures of each) with all three summed to produce a luminance frame. The telescope used was GRAS-2.

These images were taken with the moon in the sky as telescope time is much cheaper when this is the case and narrow band images are much less sensitive to the light from the moon.

This image is in false colour with Ha depicted in green, OIII in blue and SII in red. What is clear is that there is very little emission at the SII wavelength as there is very little red colour in the nebula. There is a central star in the nebula however, as it doesn’t emit light at the wavelengths used in this image it doesn’t appear in the picture.

OIII is an oxygen molecule in an ionised state that can only exist in very rarified gas clouds. It was first noticed during spectroscopic analysis of emission nebulae in the mid 19th century and mis-identified as a new element called Nebulium. It wasn’t until the 1920s that physicists correctly deduced it’s true form.

Gyulbubaghian’s Nebula (pronounced gyool-boo-DAH-ghee-an) is a Herbig-Haro object (HH215) – a variable bipolar nebula generated by the shock waves from the variable star PV Cephei. As a reflection nebula it does not emit light of it’s own but is illuminated by the nearby star. It has also been observed to fluctuate rapidly in brightness.

A request from the Deep Sky section of the BAA alerted me to the possibility that this object was currently very faint and I decided to image it using the GRAS-1 telescope to confirm this.

The result is shown here, the nebula is marked by the intersection of the two lines. The image is in negative form as this makes the nebula easier to see. Five 180 second  exposures with a photometric V filter reveals that it is very faint at the moment but large, rapid fluctuations in brightness have been reported before so I shall return to this in the near future.

For my next attempt I will try and use more exposures to reduce the noise level in the picture. As usual, clicking on the image will show the full size version.