With a DSLR camera filter modification you will get much improved transmission of hydrogen-alpha wavelengths and you will be able to take great pictures of red emission nebulae.
The Losmandy G-11 mount is a proven performer and is the most substantial mount that you can get for the price. It can last a lifetime, and will hold much bigger scopes if you upgrade. If you can't live without Go To, get the Atlas mount. The Explore Scientific 102mm scope is a very reasonably priced entry into a 4 inch ED air-spaced triplet apochromatic refractor. Don't forget an autoguider!
The modified and cooled Canon 5D Mark II should be as good as it gets for long-exposure deep-sky astrophotography with a DSLR camera because it passes a lot of hydrogen-alpha light for shooting emission nebulae, has extremely low noise because it is cooled, and has a larger sensor with wider fields of view.
For high-end equipment, you have a much wider selection of telescopes and mounts. For scopes, there are several excellent 5 inch triplet apochromatic refractors. The consensus is that the Astro-Physics is the best, but can be difficult to find. Refractors from Takahashi, Tele-Vue and Telescope Engineering Company are also excellent.
In larger-sized telescopes, virtually all of the high-end astrophotographers are using Ritchey-Chretiens. Check out scopes made by RC Optical Systems, Takahashi, and Optical Guidance Systems.
Don't forget to budget for accessories. Your budget will determine how you decide to shoot and that will influence what kind of accessories you need.
There are three basic ways of shooting:
Easiest / Budget - You don't really need much equipment to get started this way. Usually you'll be shooting piggyback with a camera mounted on top of your telescope. The equatorial mount is accurately polar aligned, and tracking is not that critical because you're not shooting at that long of a focal length. You'll need a ball head to attach your camera to your scope so you can aim it independently of where the scope is pointing.
You might also try shooting through your scope with no guiding and just keep the frames that are accurately tracked and throw out the bad ones. In this case, you don't really need much more than a T-mount and camera adapter. You can open the shutter and start your exposures with the self-timer on the camera to minimize vibrations. If you want to shoot longer than 30 seconds, you can use a cheap remote release.
Intermediate - You will want to start shooting multiple exposures for stacking to improve your images and you will need something to automate this process. You won't want to stand there and trip the shutter manually every 5 minutes for a couple of hours. You'll need a Remote Release Interval Timer.
If you are shooting long exposures, you may run into problems with dew, so you'll need some anti-dewers.
For anything more than a couple of quick shots, especially if it is cold, you will probably need an extra
battery for your camera.
For all-night astrophotography sessions, you will want a 12-Volt DC Power Adapter from Cercis Astro.
It is a very good idea to get a separate 12 volt deep-cycle battery to power your telescope and anti-dewers. Do not use a regular car battery. You need a deep-cycle marine battery.
It's not absolutely necessary, but it's a good idea to have an extra memory card or two for your camera.
One of the biggest challenges you will face will be focusing your camera. If you have a new camera with live-view focus, this will be easy, you just zoom in on a star at high magnification while you focus. If you have an older camera, you may find a Bahtinov mask, or hardware focusing aid helpful.
Advanced - You may want to use a computer in the field to automate your imaging session. In this case you will need another 12-volt battery just to power the laptop, especially if you plan to stay out all night.
If you have an older camera, you'll need two cables to automate your imaging session: one USB cable for camera control, and one serial-to-bulb-port cable for long exposures. You can get them from Hap Griffin. You'll need a program like Images Plus for camera control, focusing and image acquisition automation. If you have a new Canon, you can use Canon's software or Images Plus for remote live-view focusing, camera control, and image automation, all through a single USB2 cable.
Once you get really serious you will want to guide your images for pinpoint stars during long exposures. A stand-alone autoguider like the SBIG SG-4 is a perfect solution because it does not require a computer, with its additional power demands, in the field.
If you plan to use a computer at the scope and don't need a stand-alone autoguider, the Starlight Express Lodestar is the most sensitive guide camera you can buy. It is great with an off-axis guider because it is so sensitive you will almost always find a guide star in the field already and won't have to go to the pain of rotating the off-axis guider to find one.
For a Newtonian or SCT, you really should use an Off-axis guider .
If you manually guide, you'll need a guiding eyepiece like the Meade Series 4000 9.0mm Plössl Illuminated Reticle Guiding Eyepiece. Even if you autoguide, you'll find a high power reticle eyepiece a help in centering a guidestar on the guiding camera's chip. A wide angle eyepiece like the Tele Vue 40mm Plössl is also helpful in finding your way around.
If you image through a refractor, you can use a smaller refractor riding piggyback on top of the main scope with an autoguider like this Orion autoguiding rig and some software like PHD to run the autoguider on a computer.
Other optional accessories discussed in detail on the accessories page.
*Prices and availability of all items are subject to change without notice by the vendors and manufacturers.