IC 1396 - The Elephant Trunk Nebula. This 189.2 TRILLION mile long pillar of dust is silhouetted against a much larger nebula in the constellation Cepheus.
This was the last image that I took over the summer of 2017 before heading back to university for the fall. I had recently discovered an over flow parking lot about an hour from my house that laid in an unlikely dark zone, nestled in the hills, south of the Bay Area's extravagant display of what can only be described as a tactical assault of light pollution. Having visited the site a week prior with promising results on the Lagoon Nebula, I decided to give the site a real test- a dim cloud of ionizing hydrogen in Cehpheus.
As usual, I was met with couple of expected, and unexpected challenges. The night started with a dash of good luck. A thick marine layer had been building up along the ocean-side of hills to the west across the bay all afternoon, and by the time I had arrived, the natural dam seemed to have broken. Fog was streaming down the hillsides, socking in San Fransisco and San Jose. I watched as the semi-dark site slowly plunged further and further into darkness, the lights of the cities were being captured by the friendly clouds. I happened to be at the perfect elevation all night to keep me just above the new overcast layer.
At the begging of the summer I bought a new telescope. The old 80mm refactor was great, but it lacked the speed (light gathering power) that I (a very busy person) needed. The new scope, an Orion 8" Astrograph clocking in at F/4 was multiple times faster at gathering light than my old F/7 refactor. In theory this meant that I could get twice as much data per night than I used to. In reality, it wasn't so grand.
See, reflectors use mirrors to magnify and gather light. Mirrors are very finicky pieces of optics that require quite exact alignment to create a sharp image - something that I was woefully lacking on my dark site expedition. A reflecting telescope is typically comprised of a primary and secondary mirror. The primary mirror is a silvered disk at the tail end of the scope. It sits on whats called a "three point cell" that allows the astronomer to carefully rotate and translate the mirror. At the front of the scope is the secondary mirror. This is a small oblong mirror at a 45deg tilt that takes the focused light from the primary mirror, and directs it out of the telescope into the camera. Both of these mirrors have direct their light perfectly or else the whole imaging train will suffer.
To combat this, I use a laser to make sure that the light is traveling through my telescope the right way. I place the laser exactly where the camera would be, and point in down into the scope. The straight beam of light it produces simulates the path cosmic photons should take when arriving from space. If the laser goes into the scope, bonces off the secondary mirror, is directed into the primary mirror, bounces off the primary mirror, is directed into the secondary mirror, and then straight back through the small hole in the laser it came out of, everything should be aligned. The reasons for misalignment are varried. The car ride could be bumpy, the pressure could change, or it could just be cold out. In my case, I was able to get the scope aligned and ready to image. Or so I thought.
If you look at a photograph taken by the Hubble Space Telescope, you will notice that all of the stars have four spikes coming out of them. These are called "Diffraction Spikes". This optical effect is present in all reflecting telescopes. The secondary mirror in the Hubble, and in my scope, is held in place by four thin vanes. These are all carefully placed at exactly 90deg to each other when the telescope is built, and then never touched again. This reason for this four vane system was a mystery to me before the night at the dark site. I suppose I always assumed the number four was chosen by engineers as the most structurally stable configuration. The reality is, NASA engineers are much craftier than I gave them credit for. The four diffraction spikes you see in Hubble's images are actually an optical trick. In reality there are actually eight spikes! Each vane creates a spike that goes all the way through the star from one edge of the image to the other. The only reason we don't see eight spikes is because the vanes are placed perpendicular and parallel to each other, meaning that each pair of veins create overlapping spikes - two "+" signs laid over each-other.
Now look carefully at my image. Do you see something wrong with the stars? We're seeing 6 spikes! The only reason for this that I can think of is that one of the vertical vanes is either bent or twisted. Luckily it's only happening on the vertical spikes, and not the lateral, meaning that the whole system likely isn't twisted. Still this will take quite some time to fully fix, and may bean having to but a new secondary assembly.
Despite this, I'm quite happy with the data that the scope was able to collect - optical issues aside. I'll have to fix the vanes in the winter.