Celestial Lens for Canon

[astrostu]

I'll respond here rather than to your PM. I do not think you'll be happy with a longer but cheap mirror-type camera lens. In order to capture most planets and deep-sky objects, you will need a rather significant telescope that will give you a field of view no larger than around half a degree (somewhere around 2000 mm in focal length). For something like that, you'll need a rather large diameter so that the aperture isn't something like f/64 or bigger. And then you'd need a mount that rotates with the sky so that you can taken an exposure longer than a second or so with that focal length.

An alternative is a good-quality telephoto lens like something between 200 and 400 mm and possibly with a 2x extender. You'll still need to have a clockdrive mount to track the sky so that you can take longer exposures unless you take hundreds of photographs at higher ISO and average them together. Which is actually what you should do with planets - the best photos of planets these days are taken by people using webcamps.

Thanks for the post. So the mirror is out? Are Telescopes that allow you to attach your camera out as well? I was actually looking at a Sigma the other day. It was a 150-500 i believe and not too expensive. Sound good?

The mount sounds really good and all, but the price for a good one is just not in my budget. I just wish i could build an observatory in my back yard. :er:

To be perfectly honest I didn't look at the links to the lenses you were pointing at, but just from some that I've looked at in the past, they seem to be cheap telescope substitutes. And just from experience, going the cheap way will not make you happy with the results. I have no experience with the specific lenses that you are looking at, but keep in mind that astrophotography is one of the most demanding forms of photography on your equipment -- even my L-quality lenses show some significant issues that have to be corrected for by other methods (when possible).

Any telescope that you would be looking at would allow you to attach a camera to it. You would need a T-ring and a T-mount (these things are like $20). A T-ring is custom to your camera on one end and a universal thread on the other. The T-mount is custom to your telescope - either 1.25" or 2" diameter usually - and converts to a universal thread on the other. Thread one to the other and you have your camera on your telescope.

Not getting some type of motorized mount is kinda out of the question for this sort of thing. Unless you want to be taking dozens to hundreds of images and doing a lot of post-processing, you MUST compensate for Earth's rotation. These days, almost all telescopes sold come with a motorized mount that should be reasonably accurate. I haven't seen periodic errors listed for most, which generally isn't a good sign, but otherwise I do not have an informed opinion to make in regards to them.

 

[Sachphotography]

Regardless of the camera used. You are going to have noise. The way you get rid of a lot of in camera noise is by taking a dark frame with the lens cap on and using it to subtract that "fake" star noise. Most astrophotography programs have this as a preset. truthfully you can get a telescope with a trackable mount for not to much. You could use the ETX line of telescope and get a decent mirror telescope "Maksutov Cassegrain" with a fully motorized mount and a goto "autofinder" function built in. for under 1000. It would be good for planets but Deep space object would take a little longer. You can however mount your camera and lens on the top. Just make sure if you use a fork mount, balance it perfectly to not destroy the motors.