To connect your DSLR to a telescope you simply need a T-ring and T-adapter. The T-ring attaches to the DSLR and the T-adapter to the telescope. The T-adapter 42mm thread is a worldwide standard to connect cameras to other devices, but T-rings are brand specific, like lenses.
Once the T-ring and adapter are fitted the DSLR simply slides into the eyepiece draw tube of the telescope.
Once your camera is connected, you can use the live view to find focus on a bright star. You can shoot in 2 ways, to card (in camera) or to hard drive connected to a computer (tethered). The latter being suitable for deep sky objects as it affords better control over the entire process.
Shooting to card, make sure that the image quality is set to RAW and that the in camera noise reduction is turned off. Shooting to card you’re limited to either the in camera settings for the timer which only goes up to 30sec, or using a bulb shutter release. This can be manual or an intervalometer where you can set the time.
Tethered shooting via astronomical and standard photographic software is available to help automate the acquisition process. It helps greatly to automate an exact timed sequence and shoot straight to hard drive. This is, however, not a necessity and using a simple shutter release with the camera set to the bulb function, shooting to memory card also works well.
Many astrophotographers see shooting tethered as a drawback, as you need more power out in the field to operate more devices. Sadly, if you want superb results you’ll have to be realistic about “ease of use”.
Unfortunately as with most things worthwhile, if you want round stars the answer would be to use the best (not always costly) equipment/software out there.
For deep space photography modified DSLR cameras are generally used. These are more sensitive to Hydrogen Alpha wavelengths of light, the reddish hues in diffuse nebula. Canon manufactures the 60Da which is tailor made for astrophotography. Current stock, from the factory, DSLR cameras have CMOS sensors with anywhere from 1-3 filters in front of them, meant to block everything but the visible light spectrum to create realistic digital photos. For astrophotography, we want the sensor to record more of the spectrum, the frequencies invisible to our eyes. Many people remove the filters to allow the sensor to record more infrared or sometimes even full spectrum. The 60Da is however shipped ready for astrophotography use.
As with any photographic hobby, accessories can aid in overall improvement of image quality, but are not always necessary. However, they do go a long way to ensuring your stars remain round and rich in colour.
Coma correctors and field flatteners: A coma corrector is a lens accessory that reduces the elongation of stars at the edges of the photographic field ensuring the image stays sharp and flat across the the entire field.
Filters: Various filters are available that cut out unwanted light wavelengths, the most popular being light pollution filters that reduce the unwanted light produced by populated areas.
Guiding: Although auto guiding can be a whole article in itself, it’s worth a mention here as it’s not a necessity. The principle of guiding is simple – it aids in keeping your telescope tracking an object precisely. A secondary telescope and camera is fitted to the main imaging telescope and is locked on to a star. This camera sends corrections to the computerised telescope mount to correct inaccuracies in alignment that will show up in long exposure photos at longer focal lengths.
Barlow lenses: A Barlow lens multiplies the effective focal length of the telescope (magnifies the image). There are multiple sizes ranging from 1,1x to 5x or more.