Husband and wife photographer team Antoine and Dalia Grelin spent 81 hours capturing a photo of NGC 2264, a large and colorful nebula 2,500 light-years away in the constellation Monoceros, not far from the famous Orion Nebula.
Most recently, the Grelins — who operate the Galactic Hunter website — shared a photo of both a green comet and Mars together but recently completed a much more long-term project: a photo of NGC 2264, specifically the Christmas Tree Cluster and Cone Nebula.
The duo tells PetaPixel that most amateur astronomy photos have a total integration time — the amount of time spent gathering data — of, on average, between one and four hours. The Grelins will sometimes spend a lot more time than that, and a recent image of a distant nebula beat out their previous record of the 61 hours they spent on the Seagull and Thor Nubulae by a considerable margin.
The Grelins say that they actually spent 114 total hours taking photos of NGC 2264 over the past three months because they wanted to show the object in both true color and narrowband (in the style of the Hubble Space Telescope).
“In astrophotography, the total integration time is very important because the signal-to-noise ratio gets better the more time you spend on a target, up to a point. The goal of spending so much time on this specific target was to reveal as much faint gas as possible, and completely eliminate all visible noise from the data to get the cleanest possible image,” the couple says.
Part 1: The First 33 Hours
The two explain that the first aspect of the project was to capture true color and was done from their backyard.
“We spent a total of 33 hours with our beginner telescope and full-frame camera and were able to get the picture you see below. It shows the true color of the hydrogen alpha gas (red) which overwhelms the entire nebula,” the two explain.
“It is a beautiful image, but we wanted more, we wanted to start again from scratch but this time using a monochrome camera and a full set of narrowband filters.”
Part 2: 81 hours of Integration Time
In contrast to the 61 hours the duo spent on the image of the Seagull and Thor’s Helmet nebula last year, this exposure took 20 more hours and different equipment.
“We this time used a bigger telescope which we have installed permanently in the middle of the desert in Utah at a place called Utah Desert Remote Observatories,” the Grelins explain.
“We are able to connect to our telescope remotely from anywhere in the world and take pictures under a very dark sky. Using this telescope and six different filters, we spent several weeks slewing to the Christmas Tree every single clear night and gathering as much data on it as possible. Our telescope can be seen below in the orange square.”
The telescope the duo uses is a Stellarvue SX130 on a 10Micron GM1000HPS mount and equipped with a QHY600M camera. As mentioned, the two used six filters, exposing the S, H, and O at 20 minutes per frame and the R, G, and B at 60 seconds per frame for a total of 81 hours.
“Below you can what the data looked like through each narrowband filter (HA, SII and OIII). The three other filters (R, G, B) were used for the stars,” they explain.
The Grelins say that processing this image was extremely time-consuming and tricky.
“The total number of individual files we had to calibrate and combine, which includes all light and calibration frames, was 533. It took the computer almost a full night to finish the calibration and stacking,” they explain.
“We were able to get a color image of the object once the three monochrome channels were combined, and it looked incredible. Having so much data on this object made all the colors pop and mix naturally before even starting processing the image, and the noise was basically non-existent. We then had to be careful while processing to not clip any highlights, or bring out the details too much to keep any noise from showing.”
The Final Photo
The finished image that the Grelins put together is about 60 megapixels in resolution and is bursting with color and detail.
“Overall, this image turned out incredible, mostly due to the natural mix of colors, the crisp details, and the fact that there is no visible noise at all,” the two say. “When viewed in full resolution, looks very clean even in close-up zooms.”
The full-resolution image of NGC 2264 — the Christmas Tree Cluster and Cone Nebula — along with more technical information about the capture can be found on the Galactic Hunter website.
Image credits: Antoine and Dalia Grelin, Galactic Hunter