The Newtonians, for example, are very handy and good instruments for astrophotography, though they need to be collimated very precisely and often. On the other hand ED and APO refractors are better, but they are much more expensive. The SCTs are compact and provides longer focal lengths but they are rarely well-made.
So the question is what telescope to choose for deep-sky astrophotography with DSLR camera?

There are several different answers, depending on our object to be captured. Let’s start with the largest: wide-field images of the sky. If you are planning to capture the wide-field images of the night sky you don’t need the telescope but the lens. This is because telescopes are optical instruments with longer focal lengths and that means smaller field of view (FOV) whereas the lenses has a really wide range of focal lengths, from 4mm up to 1200mm and more. The most common target in this range of objects is the Milky Way. This kind of astrophotography is especially appropriate for beginners because the auto-guiding is not necessary and most of the cameras already comes with “kit” lenses which have wide field of view.
One of my images of Milky Way in Cygnus taken with 50mm lens:

Mosaic of Milky Way taken with 50mm lens

Next step are large deep-sky objects. For this objects I recommend the middle-sized APO and ED refractors (80-120mm) or telephoto-lenses. If we have a good mount we still don’t need auto-guiding at this focal length but in most cases it’s better to use it if possible. The most common objects in this range are constellations, detailed locations of Milky Way, large nebula complexes (Orion) and bright comets. The next picture represents Comet Holmes as it was seen 8th January, 2008, taken with Canon EF 70-200 f/4.0 lens:

Comet Holmes with Canon EF 70-200 f/4.0 at 200 mm

Next are middle-sized deep-sky objects. The best focal lengths for them are from 1000 mm to 2000 mm. Newton telescopes and larger refractors has the most appropriate specifications for imaging this type of objects. The auto-guiding is really necessary here because just the best mounts can slew accurate enough to assure the pin-point stars at these magnifications. In this range we find almost all the object from Messier’s catalogue and the brightest NGCs. One of my pictures taken with Orion Optics Europa 8″ f/4.5 are Pleiades.

The last type of object, accessible to amateur astrophotographers, are smaller deep-sky object. They are mostly galaxies and planetary nebulas. Because they are small, we need long focal length to capture the details inside them. The SCTs and other catadioptric telescopes are the most appropriate for these objects.

So, now you know which objects are in the range of your equipment. I hope that you enjoyed reading.

There are some important factors when we are deciding for the telescope which will be used for astrophotography:

• good control of chromatic aberration
• 2″ cryford focuser (micro focuser is even better)
• flat-field or additional flattener available
• good and quality mechanics
• good optics
• low f-ration (focal length / aperture)

Now let’s take a look at three of the telescopes up to 1.000$ (800€) which are good choice for astrophotography:

1. William Optics Megrez 88 Doublet FD
   William Optics is well-known of quality of their instruments. Their latest Megrez seems to be one of the best choices this year. With the 88mm of aperture and 500mm of focal length (f/5.6) it covers large field with DSLR cameras.
2. Sky-Watcher Equinox 80
   Sky-Watcher’s the best series of ED telescopes works very good for astrophotography. They looks and performs like more expensive William Optics telescopes. The color is also different – some prefers black . With smaller aperture (80mm) and the same focal length as Megrez 88 has a little worse f-ratio (f/6.25) but it’s still very good choice!
3. Orion EON 80mm ED
   Orion EON 80mm ED seems like another version of equinox. Nevertheless, maybe some finds it more useful and cheaper in USA since Orion is more popular in America. The lens characteristics are just the same as Equinox’s.
   

Do you have your own preference? Express your doubt, agree or disagree under comments!

Thank you for reading!