new to astrophotography

[tomselleck]

I am a beginning photographer and considering the purchase of a dslr for astrophotography. i dont want the newest 'stuff'; other forums i only got a new camera as advice

i would like to know what specifications such as iso, shutter speed, etc i should focus on.

Also, is full frame better for this role. especially long exposures?

Thanks

 

[rpm]

your only concern will be iso performance. shutter speed etc are standardised if i can even describe it as such but the real question is how much are you willing to put into a camera and lens?

 

[TCampbell]

Full frame is not necessarily better. But astrophotography is a whole new topic.

First, some questions...

Do you have a budget?

Do you just want a fairly normal camera to take photos of the open sky?

Are you planning to use a camera with a telescope and, if so what are you planning to use for a telescope?

Are you a member of any astronomy club?

When someone says "astrophotography" to me, I'm never quite sure what they're experience is and what they mean. For example... for some people, they just want to take a fairly ordinary camera, point it at the sky, and take photos. For others... they plan to mount a fairly normal camera onto a telescope and take photos. And for still others... they plan to use a high-end monochrome imaging sensor with an active cooling system and a color wheel which is connected to an equatorially mounted telescope being continuously corrected by an auto-guiding camera and combine all of these images to create a final color result... which looks stunning.

That final category (the high-end imagers) is very expensive and also very complicated. I could go on detail about how they do it if you're interested (I know guys who do this... on every clear night they can.)

However... you can just connect a camera to the back of a telescope that mere mortals can afford and take photos, but there are some limitations. These are usually short-duration images. It's very hard to get exposure times exceeding maybe 30 seconds unless you've got an equatorial mount & tracking system with "PEC" (periodic error correction) and an auto-guider. But for planetary imaging or imaging of the brighter deep-sky objects you can do this with normal cameras. The guys doing the deep-sky imaging of very faint objects are running VERY long exposures, usually with a monochrome imaging sensor combined with a filter-wheel and they take a series of these very long exposures using each of their filters and then combine these to create a color image. It's very hard work, but they can image very dim objects that a normal camera & scope would never even be able to see at all -- and yet they capture them in rich, vivid detail.

Canon makes a special-purpose camera just for astrophotography... called the Canon 60Da (not to be confused with the "60D" ... without the "a" suffix.) The camera is modified to allow greater sensitivity to IR light -- specifically for astrophotography. You can still use the camera for normal photography but you need to get a screw-on IR filter for your lenses.

You can also use any DSLR camera with a telescope using a T-mount (for the scope) and a T-adapter which mates with the camera. The T-mount/T-adapter system is a standard. ALL T-adapters can connect to ALL T-mounts. But the T-mounts are specific to your scope model. The T-adapter is specific to your camera model. The T-adapter mounts directly to the camera body. Effectively making the entire telescope your "lens". But this means you have only ISO and shutter speed to control... no aperture. Your stuck at the fixed focal-ratio of the scope.

There are people who will buy used DSLRs are then modify them -- essentially they perform surgery to remove or replace the IR & UV filters in front of the sensor. If you did this to a new camera, you'd immediately void the warranty. You don't "need" to modify the camera, but they get better results if they do.

Most imagers prefer to use telescopes with faster focal ratios. My larger scope is an f/10 scope... and although it's a popular scope for imaging, the serious imagers all want faster scopes... f/8 or even f/6, etc. This also provides a wider field of view to the sky (my own scope can only see a very narrow angle of view -- it's about a 3500mm focal length) and shorter exposure times. You can buy focal-reducers which drop the focal ratio for wider fields, but these don't work the same with all scopes.

The reason I asked about the astronomy club is because if you really want to get into astrophotography, most clubs will have members that are doing this and can be VERY helpful to someone trying to get started. There's so much to learn and know that having a few mentors can be a tremendous help.

I advanced my knowledge of astronomy topics more in just 1 year of belonging to a club than in 10 years of trying to figure it all out on my own.