Back in December, I finally placed the order for the astro-modification of my newly-acquired, and quite beaten up, Canon 6d! Some of the most common modifications one can perform to a camera sensor include ‘full spectrum’ and ‘hydrogen alpha’. 

Full spectrum, as the name suggests, typically removes the filter that cuts out those invisible ultraviolet/infrared wavelengths, and may optionally remove the low pass filter. The removal of the low pass filter provides significant gains in sharpness, but you risk a bit more color noise and moiré. 

The second conversion, hydrogen alpha, also requires that one removes the UV/IR cut filter in front of the sensor, but this time, is replaced with another filter with an expanded spectral range compared to the stock camera. This modification can be a bit variable, so it’s important to pay attention to which filters, or at the very least, what wavelength range is disclosed on the website selling the conversion. Optolong’s expanded UV/IR cut replacement filter ranges from 390nm to 700nm, whereas the ones installed by Spencer’s Camera and Kolari vision only cover about 420nm to 680nm. Neither of these only pass hydrogen alpha, which sits at about 656nm, but also pass Sulphur II (Sii) at 672nm, which I’d consider a welcomed addition since plenty of targets have emissions in this wavelength. This extra piece of high-quality glass in front of the sensor can increase the costs quite considerably, so it’s important to weigh the differences in utility before purchasing or performing the modification by oneself.

I personally went with the hydrogen alpha modification, since I wouldn’t have to worry about buying essentially the same filter in clip-in form if I wanted to cut back on the stray infrared and ultraviolet light. These wavelengths can be very useful for planetary astrophotography, but I currently don’t own a scope that can resolve details on the planets anyway, so it made the most sense to me. I’ve kept the investment on the low end with respect to needs, added to the fact that I essentially bought the camera itself for solely its sensor condition and low cost.  

The results of this modification are the beautifully enhanced reds in the image in both the Rho Ophiuchi cloud complex (right), and the cygnus region’s North America, pelican, and butterfly nebulae (left)! There’s even some subtle airglow present that I’ve chosen to leave subtle, so as not to draw away from those reds and the dust lanes of our home galaxy. 

Technically speaking, there were a lot of blunders here. Thanks to panoramas being panoramas, a lot of these are simply hidden by viewing distance, which is partially why I love them so much; you get such a high resolution view of things that little imperfections become minuscule! For example, my live view screen was unusually dark, which made focusing on the stars a bit of a dice roll. On the back of the camera, the stars looked fine. As per usual, when I got home, the issues started to show up! The focus was inconsistent with the stars bloating ever-so-slightly, and a brief tracker failure towards the very end of one of the exposures caused some minor trailing in one of the images. Luckily for me, they all stitched fine, and the colors contained in them. I had quite a few of these tracker failures throughout the night, and lost about an hour or so, mid arch. It was because of this that I decided to stick to capturing just the arch and forego the ‘play-frames’ I would have liked to take to give myself some more sky to work with in case the stitching went wrong. It was the first tracked astro-pano of the Milky Way I had ever tried, so I was more than content to just call it a test run and get some rest with minimal expectations for how it would turn out. It’s safe to say, my expectations were blown out of the water!