How do I take Astrophotography with a Cannon 40D?

paulviking

I have a Cannon 40D digital camera, and I’ve already purchased the T-mount//body connection, for my Meade telescope. I’ve been wanting to merge these two hobbies together (Photography/Astronomy) for about a decade now, and am finally getting around to it, but with much difficulty.

The problem is that the camera body doesn’t focus on anything without a lens. This is where I’m stuck at. I know that in Astrophotography the telescope is the lens…I get it. But, the cannon body doesn’t have any focus point (50 million miles or 5ft) without a lens attached. I’ve been told that the lens extenders (i.e. 1x or 2x) don’t have a focus of their own, but they do have the appropriate male-to-body-fitting and the female-to-lens-fitting where the T-mount could attached, and the lens extender would be in between, but that doesn’t work, like I said, I was told it doesn’t have a focusing mechanism in it.

Does anyone know how to overcome this bridging problem? Once again, the telescope can be in perfect clarity and when I pull the eyepiece out and slide the camera into its 1.25” T-mount connection, the camera doesn’t have a means to focus with. (I’m repeating this because, everyone I asked already keeps coming back with “the telescope is the lens”…yea I get it, but how do we get the camera to focus, so that it can see what the eyepiece in the telescope can see.

Thanks

Shane422

You may merely need a longer adaptor. I was at our local observatory this weekend and one of the members had been doing some astrophotography and had left an extender on the scope that made it impossible to focus with just and eyepiece. So I think it is common to use more than one coupling to achieve the right distance for focus.

I have been looking at adaptors to accomplish both "Prime focus" (i.e. no eyepiece involved), and "eyepiece projection" which allows you to shoot through an eyepiece to use the magnification of the eyepiece.

Here is one from Orion that accomplishes both
http://www.telescope.com/control/product/~category_id=photo_accessories/~pcategory=photo_accessories/~product_id=A0321

And another from Orion for Prime Focus with a 2in focuser
http://www.telescope.com/control/product/~category_id=photo_accessories/~pcategory=astro-imaging/~product_id=05269


Here is another place with several different choices of adaptors.
http://www.cncsupplyinc.com/

SKnight

I'm sure someone far more experienced will chime in but I'm going to do my best.

On your camera body, on the top is a circle with a line through it. That is the focal plane of your camera. On my XSi it's on the left side right next to the shoe mount.

What has to be done if to achieve the correct distance from the focuser so that the focal plane of the camera matches that of the scope. At that point it becomes a giant lens.

That's the extent of my knowledge, I'm a visual observer so that info is from talking to friends that astrophoto.

Really the best bet is to join a club in your area that has astrophotographers that can help you hands on. You won't believe how helpful it will be to have someone right there to help you.

Click this link, on the left side is a club locator. Just out in your zip and off you go.

http://astroleague.org/

Robinivich

I don't have a lot of knowledge of specific connections used with telescopes, but from the sound of things you might already have the focus mechanism in front of you.

All that focusing is is moving the focal plane of the camera (Sknight referenced this) to the point of focus of the scope. In real terms, to do this, turn the live view mode of the camera on, so you see exactly what the camera sees (better to use the sensor than the viewfinder, liveview gives you incredible magnification, makes focusing really easy), and slide the 1.25" fitting back and forth until little blurs become little points, and voila, you should be in focus. As far as I know, this is how it's done. I'm assuming that there is some kind of mechanism on the telescope or the camera mounting assembly that allows you to move the camera forwards and backwards.

Personally I would try this during daylight hours first, so you can see what you're doing with all those fittings, and more light will make everything easier to focus. Just pick a target that's a good distance away.

Hope this helps!

hgernhardtjr

I'm not being flippant here, but I focus with my telescope's focus knob.

I have used my Celestron Schmidt-Cassegrain for 30 years now, and simply t-mount the SLR or dSLR to it, and focus with the focus knob while looking through the viewfinder. I have used the same technique using the focuser knob on reflector scopes, also.

The Celestron is great for both astro and terrestial photography, though for astro I get the scope aligned and the tracking all set before I mount the camera. Dobsonians are a challenge simply because they have no real tracking mechanisms to keep costs down.

Oh, to make things a bit easier, I use a quality right angle finder adapter on my camera which helps as I focus at odd neck-breaking angles.

ziggy53

paulviking wrote:

I have a Cannon 40D digital camera, and I’ve already purchased the T-mount//body connection, for my Meade telescope. I’ve been wanting to merge these two hobbies together (Photography/Astronomy) for about a decade now, and am finally getting around to it, but with much difficulty.

The problem is that the camera body doesn’t focus on anything without a lens. This is where I’m stuck at. I know that in Astrophotography the telescope is the lens…I get it. But, the cannon body doesn’t have any focus point (50 million miles or 5ft) without a lens attached. I’ve been told that the lens extenders (i.e. 1x or 2x) don’t have a focus of their own, but they do have the appropriate male-to-body-fitting and the female-to-lens-fitting where the T-mount could attached, and the lens extender would be in between, but that doesn’t work, like I said, I was told it doesn’t have a focusing mechanism in it.

Does anyone know how to overcome this bridging problem? Once again, the telescope can be in perfect clarity and when I pull the eyepiece out and slide the camera into its 1.25” T-mount connection, the camera doesn’t have a means to focus with. (I’m repeating this because, everyone I asked already keeps coming back with “the telescope is the lens”…yea I get it, but how do we get the camera to focus, so that it can see what the eyepiece in the telescope can see.

Thanks

Paulviking, welcome to the Digital Grin.

The Canon 40D has Live View and this would be a good application for that feature. Use the optical viewfinder to get close to prime focus and then engage the Live View and zoom/magnify that view for prime focus.

There is even a You Tube about this:

http://www.youtube.com/watch?v=lxTalp6f7kw