Carbon Capture

A few weeks ago I found that my iPolar software in my HEM27 iOptron mount was routinely crashing when trying to perform polar alignment. The latest missive from tech support suggested that I should update the firmware. So with a clear sky and open schedule I took the opportunity to finally apply the update and re-test the software. Sadly, and a bit frustratingly, it still crashed when trying to do an alignment.

Despite the technical hiccup, I decided to pop on the Vixen and start an observation session with the objectives of evaluating the new (to me) 13mm TeleVue Delite eyepiece purchased at the HAL Christmas Party auction and visiting some items on the AL Carbon Star observing list. The sky was devoid of moonlight, offering seemingly clear visibility with a thin haze. Orion was dropping below the western tree line while Boötes was yet to climb over the roof from my backyard vantage point.

To keep it simple I elected to visit three carbon stars for the evening’s itinerary. Carbon stars are a fascinating subset of stellar objects that capture the interest of many amateur astronomers. These stars, characterized by their deep red hues, have atmospheres containing more carbon than oxygen, leading to the formation of carbon compounds that give them their distinctive color. The attraction of carbon stars lies not only in their sometimes striking appearance but also in their varying luminosity. They lend themselves well to the skies often encountered by the suburban amateur astronomer.

My first target was Y CVn, a carbon star in Canes Venatici, also known as “La Superba.” Despite the challenges with the iPolar alignment, the accuracy of the pointing allowed me to use the Slew & Center function efficiently on Cor Caroli. Upon keying in the coordinates for Y Canis Venaticorum, I inspected the field at low power and immediately identified the star by its red tint compared to other field stars. Switching to the 13mm eyepiece enhanced the color slightly, but the sparse field and light pollution subdued the redness. In comparison, I recalled Mu Cephei and Hind’s Crimson Star as being more striking.

Next, I attempted to observe T Cnc in Cancer. Using the Sync to Target function after slewing to Mars, I fine-tuned the positioning and centered the object. Initially, the field appeared pleasant but lacked any sun with the characteristic cerise coloration. Increasing magnification to 46x revealed a star with a slight hint of red, which I am guessing was T Cancri. Its faintness (probably at around 9th magnitude according to current AAVSO observations) likely made it challenging to detect its red coloration distinctly. It’d be worth targeting again with either a larger aperture or maybe from a darker sky.

After my challenging observation at T Cnc, I bid the scope to move a couple degrees to neighboring carbon star X Cancri. This time the low power view, a field busy with stars of a wide range in brightness, quickly revealed one breaking the monochrome black and white palette with a distinctive ruddy glow. Again, the 13mm eyepiece offered a better view at 46x by darkening the background a bit to increase the contrast a tad. To my eye this one is similar in brightness and redness (maybe even a slight bit ruddier?) than La Superba visited at the start of the session. That along with a more interesting field makes this a nice addition to the Astronomical League’s Carbon Star observing program.

Observing carbon stars for the suburban astronomer requires a little patience and modest equipment to work with their faint luminosity and distinctive color which can be obscured by light pollution or a sky lacking good transparency. Nevertheless, the pursuit of these celestial furnaces nearing their end of life certainly can be a rewarding endeavor and a pleasant evening’s celestial pursuit.