Tuesday night was pretty clear so after taking the pictures of Albireo on the club’s 20″ reflector I switched to M27. The 20? has some problems with tracking and field rotation as it’s on a motorised Dobsonian mount so it’s best to use a high ISO setting on the camera and keep the exposures as short as possible. I took 30x 20 second exposures at ISO 1600 and 15 were usable although there’s some elongation visible in the final image.
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.
Boxing day was clear and bright which continued into evening so a visit to the observatory was in order to take some more footage of Venus (pictures to follow, hopefully).
Once Venus had set then I switched to the Canon 350D as the sky was beautifully transparent (a truely rare occurance this year!). I had some problems with the EQ-5 mount as it wouldn’t align, seemingly unable to locate Vega during a single star align. Giving up on this I manually aligned it on Orion for some pictures of the nebula. 15 30-second exposures at ISO 800 are combined for this image.
After a pretty fruitless evening trying to image Venus with the webcam on the club Celestron 9.25″ I fitted the Canon 350D instead and took this picture of the Ring Nebula in Lyra.
Not a good image as it’s out of focus and the stars have trailed slightly, but it’s still an amazing sight. This is the result of a single 60 second exposure.
M57 has a white dwarf star at the centre which has shed it’s outer layers towards the end of it’s life, forming a Planetary Nebula. Despite the name, these have nothing to do with planets, the term was coined by William Herschel in 1785 as in his telescopes they looked like small faint disks of light.
As promised, and in no particular order, here are the remaining pictures from my rent-a-scope trial: