Astrophotography, or ďimagingĒ as itís usually called by those in the hobby, can be both rewarding and a bit challenging. Technology has revolutionized all aspects of astronomy. Todayís amateurs can take better images with specialized digital cameras than professional observatories could using the old film technology of just a few years ago. Itís really easy to hold a cheap digital camera up to an eyepiece and take a great image of the moon. But, if youíve got any geekness inside you, donít do it! You might get caught in the world of imaging. It can become an all-encompassing endeavor eating up countless hours while making your bank account vanish. Although you can start with relatively inexpensive hardware and free software, youíll progressively want more expensive cameras, bigger telescopes, better mounts, and fancier software. Itís an addiction that never ends. Plus, there is a fairly lengthy learning curve involved in this hobby and a million things can (and do) go wrong, so donít even think about it unless youíve got an amount of patience and perseverance that borders on masochism.
If itís so challenging and expensive why do I do it? Perhaps itís because it isnít easy. Perhaps because it reveals a universe we canít otherwise experience. And I get to do it myself, with my equipment, in my backyard, without relying on some massive government project. Thereís a popular belief that high magnification is required. Of course this is true for many objects, but most of the images I take magnify objects just 10 to 50 times (if printed on 10Ēx8Ē and held a couple feet away). This isnít a lot. Many deep sky objects viewed by amateurs are fairly large; some are several times larger than the full moon. But they are very dim requiring the hardware to gather much more light than the human eye can detect. My 12.5Ē telescope obtains 2300 times more light, a digital camera can increase this by a factor of 50 times, and a 5 hour exposure increases it by an additional factor of 500,000. I canít think of another field capable of over a 50 billion times amplification. Perhaps itís just the technical challenge. Regardless, I find it very rewarding (yes, I may be a bit crazy Ė itís practically a requirement in this hobby).
When I started taking digital images, I was amazed at what I could see with a camera compared to an eyepiece. Visual astronomy requires a very dark site with absolutely no stray light destroying your dark adapted eyes. Of course, dark skies are always an advantage, but a camera doesn't care about that street light down the block. Cameras are always Ďdark adaptedí and they are better at capturing photons. To record dim objects you need to take long exposures. Our eyes gather light for only about 1/30 of a second before resetting our mental image while a digital camera can build up an image practically forever. A simple 10 second exposure gathers roughly 300 times more light than our eyes can capture with an eyepiece on the same scope Ė and thatís not including the fact that the camera is over 50 times more efficient at detecting photons. I initially took a lot of 10 to 60 second exposures each evening. The images were crude with lots of noise but the objects were far more recognizable than what I could see using an eyepiece. I'd brag about how many objects I captured. Two or three dozen during the evening wasn't unusual. Now I realize how foolish that was. The images recorded by a camera can last forever so why not take extra time and strive to make them look as good as possible. Better images require longer exposures. I now know the figure of merit isn't "how many images per night" but rather "how many nights per image". I usually use exposures of 5 to 20 hours. Obviously, this canít always be done in a single night. Given daylight, clouds, rain or snow, and perhaps a full moon coupled with some objects only being visible part of the night, it may actually require several days, weeks or sometimes even months just to get sufficient time with the right sky conditions (I told you patience is required). How can such an exposure be made? Well one benefit of today's digital world is that we can get the advantages of a very long exposure by combining many shorter exposures. I may take as many as fifty or sixty 10 minute exposures throughout a night's session and repeat this over several nights. I then tell my computer to add all the good ones together after discarding the images where something went wrong. This effectively gives me a very long exposure without worrying about shifting clouds destroying the image or a plane, satellite or meteor going through my field of view (all very common). Yea, there's actually a lot required to make this happen. But that's what makes it challenging.
Iím not a novice and clearly not an expert. Guess that makes me a fairly typical deep sky imager - at least among those serious about the hobby. I started the activity shortly after collage (many years ago) when Celestron came out with their C8 Schmidt-Cassegrain scope. This very popular little 8Ē orange scope revolutionized amateur astronomy and eventually led to todayís fantastic equipment. In those days imaging meant using specially hyped film with hours of manual guiding just to get something vaguely similar to what youíd see in magazines. Well it was just too hard for me. I put the scope away until I discovered the new world of digital imaging. I followed the rule of acquiring ever more expensive hardware starting, like many others, with a classic 10Ē Meade LX-200 scope and an SBIG 7E camera. Then, like everyone, I slowly improved my equipment getting a better camera, mounting the scope on a better mount and finally getting a better scope. Iíve now got some great hardware including an Astro Physics AP-900 mount on a permanent pier, a Rainbow Astro RST135E portable mount, Takahashi FSQ-106 4Ē refractor, Planewave 12.5Ē CDK scope, and Finger Lakes Proline 16803 camera. Better equipment doesnít necessarily lead to better images but it does mean less effort is required. Someone starting out in the hobby today has the advantage of an explosion in the availability of really good hardware and software at very low cost thatís occurred over the last few years. This has made the hobby much easier and far more affordable.
I specialize in deep sky images. This means galaxies, star clusters, super nova explosions, planetary nebula, and emission, reflection and dark nebula (the clouds of space). Although I have many great Televue eyepieces, I almost never use them. I just canít see observing a dim fuzzy blob when you can get great images through digital time exposures. And since everything is computer controlled I can do it in a nice warm living room in the winter or hiding from bugs in the summer. I also donít do much solar system work. Imaging planets or the sun uses a totally different process than deep sky imaging. I do have special filters for the Sun and several good video cameras key to solar system imaging, but for some unknown reason havenít done much with them.
Deep sky imaging is dependent on equipment, processing skill and sky conditions. I have good equipment and am working on my processing skills but thereís no substitute for dark steady skies. Unfortunately, my sky is neither dark nor steady.† I use 2 observing sites. Most images are taken at my home 60 miles north of New York City. Observing conditions are not the greatest. I have limited sky visibility, considerable light pollution and poor seeing. Surrounding trees hide altitudes under 35 degrees to the east and 55 degrees to the west with a visual magnitude limit of about 5.4 at best. Itís rarely that good. In fact, I usually have a hard time spotting the magnitude 2 star, Polaris. Itís normally a class 6 location (orange) on the Bortle scale, occasionally moving into class 5. Summer images are often taken at a location 144 miles further north. Here the sky is better at about a 6.3 visual magnitude and the Milky Way is clearly visible with a lot of detail. However, thanks to a nearby lake, there is a lot of water vaper in the air which often fogs up after midnight significantly limiting imaging time. Iím often asked ďhow can you do astrophotography with these sky conditionsĒ. I know my images will never compete with those taken from a better site. But, this hobby is about enjoying what you can do yourself, even if it isnít the best in the world Ė just like every other hobby from playing golf to painting landscapes.
I consider both locations to be semi-permanent. They both utilize a fixed pier with all equipment mounted 24/7 but not contained within a permanent structure. I use a TeleGizmos 365 series cover plus a garden variety Home Depot brown tarp to protect the equipment.† Power supplies and all electronics, including a headless computer (no monitor or keyboard), are contained in a simple box hung on the pier. This keeps cables short and organized with a simple bundled cable set feeding the camera/focuser/heater units and a second bundled cable set feeding the mount. This computer runs all the software controlling the scope, mount and cameras plus a couple of weather stations monitoring clouds, darkness and rain. A LAN connection allows remote control of the system using VNC software. I use a remote laptop to setup a nightís operations then usually an iPad to periodically monitor or modify operations. Occasionally Iíll use my iPhone when Iím away from home.
I use software popular with many deep sky imagers: Windows 10 Pro with TheSkyX planetarium software, ASTAP for plate solving, PHD2 for guiding, NINA for image capture, MaxIm for image calibration, CCDStack for stacking and initial stretching, and Photoshop for image processing. NINA lets me run the whole thing while I get a good nightís sleep. It can automatically sequence through the objects Iíve selected with the appropriate filters, focus the scope, rotate the camera as needed, correct for pointing errors, select guide stars, make calibration frames, and of course take the images that I can process the next day.
I can fully understand why multi-hour exposures or processing with complex programs like Photoshop or PixInsight might not be for everyone. But that doesnít mean you need to suffer looking through an eyepiece at dim ill-defined blobs. Sometimes I just like to do what I call visual imaging. This is where I attach a digital camera to a scope and just take short exposures of just a few seconds. A highly binned monochrome astro camera works best but a normal DSLR or mirrorless camera is fine. The scope could be as simple as a DSLR lens attached to an inexpensive tracking device on a standard camera tripod. Objects are then viewed on a computer, tablet or camera screen: a slight variation of whatís often called a live view. As I said before, the camera is far better at capturing dim images than the human eye. This configuration lets me enjoy many of the sights available in the night sky with clarity but without complexity. They wonít be as impressive as the processed long exposure photos seen in magazines but galaxies, bright nebula and larger planetary nebula actually look like they should. Visual imaging is a simple way to enjoy deep sky astronomy and in my opinion more rewarding than using an eyepiece.