As the season transitions from summer to fall, the nights have become longer and cooler in the backyard. This is beneficial for deep sky astrophotography for many reasons, with more time to capture exposure time on incredible targets like the Elephant’s Trunk Nebula being one of them.
For those that have been following my YouTube Channel, you’ll know that I’ve been testing out a new APO refractor telescope, the Sky-Watcher Esprit 100 ED. I was shocked to see just how many of my subscribers were already using and enjoying this exact telescope for astrophotography.
In the following post, I’ll show you how I captured the Elephant’s Trunk Nebula using a camera and telescope from my backyard in the city. The final image includes 1 hour and 50 minutes of total integrated exposure time.
Photographing the Elephant’s Trunk Nebula
From my little backyard, I like to choose targets that offer a long run of imaging time before running into an obstruction (like my neighbor’s roof). This can be challenging at times, and certain objects have a very small window of opportunity.
This, unfortunate reality that many of us backyard astrophotographers face often has a lot to do with the deep sky targets we choose to photograph. I’d love to simply choose the most interesting nebula or galaxy to shoot each month, but I usually opt for something that I can spend a fair amount of time on.
Total integrated exposure time is the single biggest factor to consider when executing a new deep sky astrophotography project. The best images in the world usually include 10 hours of exposure time or more, not an hour and a half.
With that being said, the Elephant’s Trunk Nebula is well placed in the night sky for plenty of exposure time during the months of September and October. I expect to collect a much more time on IC 1396 throughout the month of September.
Setting up the Sky-Watcher Esprit 100ED APO Refractor
Targets that rise almost straight up in the sky benefit from less turbulence in the air, which (in my experience) results in tighter stars. It’s also free from the tall obstructions present on my back patio such as an increasingly tall Northern Hackberry tree.
The plan was to capture as many 5-minute exposures as possible during the brief stretch of clear nights we’ve experienced in September this month. These nights have all been mid-week, which can often lead to some groggy days at work to follow. But that’s what we signed up for.
To properly showcase this 5-degree wide emission nebula and cluster of young stars, I’ve decided to use a narrowband filter with a color camera. Not just any filter, a duo-narrowband filter that captures both Ha and OIII at the same time.
- Common Name: Elephant’s Trunk Nebula
- Catalogued: IC 1396 (Embedded Star Cluster), vdB 142
- Object Type: Emission Nebula with embedded star cluster
- Distance: 2,400 light years
- Constellation: Cepheus
The location of the Elephant’s Trunk Nebula – Sky and Telescope
The Camera and Filter Used
The STC Astro Duo-Narrowband filter has been an astonishingly useful addition to my growing collection of light pollution filters. Together, with a cooled color CMOS camera, I have been able to produce some of my best deep sky images to date.
With the cooler temperatures at night, I’ve managed to lower the sensor temperature on the ZWO ASI294 MC Pro to -20C. This helps capture low-noise images that make the image processing stages so much more enjoyable later on.
The sensor size of the ASI294 MC Pro is an excellent fit in terms of pixel scale with the wide field Sky-Watcher Esprit 100ED refractor. The field of view using the Esprit 100 with the included field flattener (corrector) and this camera is perfect for large nebulae objects like the Elephant’s Trunk Nebula. I used this handy tool to calculate the field of view.
The image above illustrates where I threaded my 2-inch filter on the imaging train of this configuration. Finally, I think I’ve got the correct spacing between the camera sensor and the flattener!
The ZWO ASI294 MC Pro Camera attached to the Esprit 100 2-Element Corrector
Update: A number of folks contacted me after seeing the way I had the camera and filter connected to the field corrector in my Pacman Nebula video. Two helpful options for placing the 2-inch filter in front of the sensor have surfaced.
Thank you to Jimmy and Kevin for the tip. I appreciate the advice, guys!
The Starizona Filter Slider.
In late August, I was sent a Sky-Watcher Esprit 100ED APO to review. It’s a wide-field apochromatic triplet refractor, my absolute favorite type of telescope for astrophotography. I have only recently mounted the telescope to the iOptron CEM60 mount and sorted out all of the necessary accessories for astrophotography.
The Sky-Watcher Esprit 100 ED included a threaded 2-element field corrector (or, “field flattener”) and a Canon t-ring adapter. Instead of connecting my DSLR camera, I’ve opted to try the ASI294 MC Pro for some more narrowband imaging.
I’d like to eventually take advantage of the full-frame corrected focal plane with my stock Canon 5D Mk II. I may try shooting a reflection nebula using this camera such as the Iris Nebula, or Witch Head Nebula.
Sky-Watcher Esprit 100ED Super APO Triplet Specs:
Glass: Schott/Ohara ED
Focal Length: 550 mm
Focal Ratio: F/5.5
Weight: 16.3 lbs.
At a focal length of 550mm, this triplet is best for capturing large nebulae and galaxies. In my early tests on the Elephant’s Trunk Nebula, the very edges of the image showed elongated stars. After correcting the spacing between my camera sensor and the threaded field corrector, I am happy to report that the stars are now pin-points to the edge of the image.
Overall the Esprit 100ED has been a welcome addition to the AstroBackyard with yet another focal length and native magnification to play with. In contrast, my Explore Scientific ED102 has a focal length of 714mm despite only being 2 inches larger in aperture.
The following image was captured over 2 nights in early September from my backyard. The complete photo details and equipment breakdown are listed below.
IC 1396 – The Elephant’s Trunk Nebula – Trevor Jones
Total Exposure Time: 1 Hour, 50 Minutes
(22 x 5 minutes)
Mount: iOptron CEM60 center-balanced equatorial mount
Telescope: Sky-Watcher 100ED Super APO triplet
Camera: ZWO ASI294MC Pro
Reducer: Sky-Watcher 2-Element Field Corrector
Filter: STC Astro Duo-Narrowband Filter
Autoguiding: Starfield 60mm Guide Scope Package