Spectrum Scientifics Blog

At Spectrum, we often get asked by telescope shoppers “Can I do astrophotography with this telescope?” Very often we have to brace ourselves, because there is no easy answer to that question.

Let’s put this question in perspective: Most people when they think of astrophotography are thinking of the excellent shots seen on astronomy books, online sites, and even on posters. But what is not conveyed is that these magnificent photographs are the result of many hours of set-up, thousands of dollars of special equipment, and often even more hours on the computer.

Imagine if you owned a music store and someone came in to look at violins and asked ‘So can I play in the Local Syphony Orchestra if I buy this’? Very likely the answer would be ‘no’. - the same situation applies to our telescope shopper and those gorgeous astrophotos. However, even if our potential violin buyer never plays at the orchestra they can certainly enjoy learning how to play scales, some simple violin pieces, and maybe even acquire enough skill to play in string quartets or even the orchestra. A similar situation applies to our telescope buyer: They can do some astrophotography. Just don’t expect miraculous results right from the start, and even those results will take a lot of time.

So with that picture in mind, let’s look at how you can do some astrophotography from the basic stuff to the advanced work.

Afocal Photography: This is perhaps the simplest form of astrophotography. The idea is simple: If you can see it in the eyepiece then you should be able to hold up a camera near the lens and take a photo of the image, right? Well, sort of. This technique does work, and digital cameras made it a viable option again. You still need a SLR camera (preferably digital) set to focus at infinity. Then just hold it up to the lens and snap a sufficiently long exposure shot. This is the hard part as it may take some time and hold the camera up to the lens and still may not be easy. There are some mechanical devices that will help you hold the camera up to the lens, but even they have limits. This kind of photography should be limited to very bright objects like the moon or the brighter planets.

Direct Objective Photography: Here is where you only need the body of a SLR camera. In this case the telescope becomes your cameras lens. Almost all telescopes made these days have threads that can accept a T-Ring adapter. T-Ring adapters are brand specific to your camera and need to be purchased from a camera supply store. Once the camera can be coupled to your telescope, you need to aim the telescope at the object you want to photograph, then couple the camera and set the exposure time.

Sound easy? It isn’t because I am skipping a few details. For one, exposure time can be as long as a 1/2 hour, your telescope has to be stable enough to not wobble at all (steel tripod legs are a must), and you will likely need to use a guidescope - a smaller telescope on top of the main telescope used to center on a single star that is used to measure if the telescope mount’s motors are tracking properly. This is in addition to other equipment designed to get the best images: filters, software, etc.

These days, the advancement of CCD (Charged Coupling Device) technology has allowed the development of specialized cameras that are designed to work on telescopes. These ‘cameras’ slip right in the eyepiece and produce digital images designed to be stacked on computers later on. They don’t eliminate the need for sturdy mounts, tracking, and long exposures but they do make life easier for potential astrophotographers.

So to summarize, if you plan to do any astrophotography you will need at least the following:

Telescope: Minimum of 3″ Diameter, larger preferred.
Mount: Steel legs a must
Camera: SLR or devoted astrophorography camera unless you are doing afocal photography and even then an SLR is a good idea.
Time: Lots of it.

Getting back to our violin buying metaphor. One good thing about astrophotography is that almost anyone can do it for the most part if they take the time and effort to learn. The same is not true for every violin buyer, where factors like finger dexterity, pitch sense and other things come into play. So while all that has been written here may sound discouraging, keep in mind that if you put the effort in, you will have success with astrophotography.

In Part 2, we will talk about photographing specific things and what is needed.

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Filed under: Astronomy