This post is part of a larger 4 step series, check them all out:
Step 1: Using the Star Adventurer Tracker
Step 2: How to Shoot the Moon
Step 3: Choosing Gear for Deep-Sky Imaging
Step 4: Shooting Deep-Sky Images
Using a star tracker gains you experience with the fundamentals of deep-sky imaging. Shooting the Moon gains you experience focusing and framing through your telescope.
Through your sessions you’ll encounter challenges like clouds, dew, aircraft, satellites, wind, and dumb user errors! If, despite all that, you want to continue your astrophoto adventure, the next big step is shooting deep-sky objects through a telescope.
For example here’s an image of the Andromeda Galaxy shot with a Sharpstar 61EDPH refractor.
What You Need to Know
Success in deep-sky imaging requires proficiency at several key skills:
- Polar aligning a mount
- Setting up and aligning a GoTo mount so it can find things accurately
- Knowing the sky well enough to decide what to shoot and when to shoot it
- Knowing how to focus and set exposures for the best results
- Patience! To wait for the best nights, and to accept and learn from your mistakes!
Using a low-cost star tracker teaches you all those skills, with the exception of using a GoTo mount, an essential item for telescopic deep-sky imaging.
Choose an Astrophoto Rig: The mount
The literal foundation of any astrophoto setup is the mount. Entry-level models include the Sky-Watcher EQM-35 Pro, a lightweight but solid German equatorial mount (GEM) with full GoTo capability. Its polar axis scope makes it easy to polar align, just like a star tracker.
The new Star Adventurer GTi, a GoTo version of the Star Adventurer tracker, will be ideal for those looking for utmost portability without sacrificing GoTo and full auto-guiding capability. It will work well with small 60mm-class photographic refractors.
The standard fittings of such mounts allow them to be used with a variety of telescopes. But the cardinal rule is to not overburden a mount with too heavy or large a telescope. Doing so risks poor tracking, vibration from wind, and trailed images.
Choose an Astrophoto Rig: The Optics
Astrophotographers prefer to select “à la carte” from a wide range of optical tube assemblies (OTAs), to mate to a mount purchased separately, often from another brand.
By far the most popular type of telescope for not only beginners, but also among advanced photographers, is the apochromatic (colour-free) refractor, typically with a relatively fast (for a telescope) focal ratio of f/4.5 to f/6. “Apos” with just 60mm to 80mm aperture might seem small, but their focal lengths are ideal for framing many deep-sky targets and photogenic starfields. Their lightweight OTAs work well with a small, portable and affordable mount.
Bigger telescopes such as larger refractors, photographic Newtonian reflectors, or Schmidt-Cassegrains do frame smaller objects such as galaxies better, but they require bigger, heavier and more costly mounts. Start small and modest.
Some astrographs have the required optics built-in to flatten the field to ensure pinpoint star images corner to corner. With other telescopes a field flattener lens (which might also serve to reduce the focal length and speed up the focal ratio) is an optional, but usually essential, accessory.
A deep-sky imaging rig (mount and telescope) will start at $2,000. We offer several astrophoto packages, from entry-level systems to advanced packages for the more experienced astrophotographer. Or you can mix and match components to assemble your own custom dream system.
Use the Astrophoto Camera You Own
To start, use a standard DSLR or mirrorless camera. They can take excellent deep-sky images in the 4- to 12-minute exposures needed. The common practice is to shoot as many “sub-frames” as the night or your time allows, for later stacking to smooth noise and eliminate satellite trails.
A DSLR or mirrorless camera doesn’t need a computer to power and control it, nor store its images, making for a simpler setup to hone your skills and get great images.
Upgrade to a Cooled Astro Camera
With their greater affordability in recent years, using dedicated astro cameras has become popular. These often have CMOS sensors similar to those in standard cameras, but with greater sensitivity to the deep red wavelengths emitted by nebulas, and active cooling circuits to chill the sensor to below freezing. This reduces one form of noise (thermal noise) that can plague deep-sky images, especially in summer.
We offer the hugely popular ZWO line of cooled astro cameras, starting at $1,200, in both “one-shot” colour (OSC) and monochrome models, with a choice of sensor sizes, such as: micro four-thirds (13x18mm), APS (15x23mm), and full-frame (23x36mm).
They are best controlled with their specialized computer, the ZWO ASiair Plus ($399), that rides along on your telescope, and stores the images.
Add power Sources
Powering a mount requires a source of 12 volts. A cooled astro camera also demands 12-volt power, as does an auto-guider camera and its control computer. In all, for field use you need a battery (or batteries) capable of delivering several amps of 12-volt power. The Celestron PowerTanks (shown) will do the job.
The finest images come from shooting under dark, moonless skies away from urban light pollution. However, specialized “narrowband” filters (like the Optolong L-Xtreme or the Antlia ALP 5nm Golden) can block a great deal of light pollution and moonlight, making it possible to do some deep-sky imaging from suburban backyards.
The targets suitable for such filters are limited to gaseous nebulas that emit only at very specific wavelengths, primarily red Hydrogen-alpha and green Oxygen-III. The Milky Way, visible in summer, autumn and winter, is rich in such targets.
We carry filters from popular brands such as Antlia, Optolong and ZWO, in dual-band (red + green) models suitable for colour cameras, as well as single-band filters for use with monochrome cameras favoured by advanced users.
Choosing the right gear is just the start. See our Astrophotography Tutorial Step 4: Using Gear for Deep-Sky Imaging for the steps on using it all in the field.