astrophotography w/ 300d and Meade ETX 125 question

[mickeymouse1]

I've been looking at scopetronics.com for the parts I'll need to hook my Digital Rebel up to my Meade ETX 125 telescope.

It looks like I should just need a T-adapter (meade part #64) and T-ring specific to my camera to get started.

Now here's my question...

It appears the camera body hooks to the telescope without having a camera lens attached. The camera is also not going through whatever eyepiece I currently have on the telescope.

So how do I tell what kind of magnification I would be getting w/ no lens or eyepiece? Would there be a plain glass (no magnification) eyepiece that could go in the telescope to mimic what the camera will capture? Or should I just use the camera viewfinder (that can be a lot tougher to look through depending on the orientation of the telescope).

Or is there a different type of adapter I should be using that actually puts an eyepiece in-line w/ what the camera is seeing?

Thanks for any pointers on this. It's just starting to warm up enough that I'd like to start taking the telescope out again.

-Mark

 

[Eneref]

I've been looking at scopetronics.com for the parts I'll need to
hook my Digital Rebel up to my Meade ETX 125 telescope.

It looks like I should just need a T-adapter (meade part #64) and
T-ring specific to my camera to get started.

Now here's my question...

It appears the camera body hooks to the telescope without having a
camera lens attached. The camera is also not going through
whatever eyepiece I currently have on the telescope.

So how do I tell what kind of magnification I would be getting w/
no lens or eyepiece? Would there be a plain glass (no
magnification) eyepiece that could go in the telescope to mimic
what the camera will capture? Or should I just use the camera
viewfinder (that can be a lot tougher to look through depending on
the orientation of the telescope).

Or is there a different type of adapter I should be using that
actually puts an eyepiece in-line w/ what the camera is seeing?

Thanks for any pointers on this. It's just starting to warm up
enough that I'd like to start taking the telescope out again.

Two types of basic astrophotography... prime focus, and afocal.

Prime focus basically uses the telescope as a giant manual-focus camera lens. In this way, just attach the camera directly and use the camera viewfinder (as best you can) to focus on the subject. It takes a little practice getting focus right this way.

With afocal, you have a camera lens on the camera, and attach that to the telescope lens, and drop that on the scope. In this way, you're actually focusing on the image that is seen by the lens. This makes the telescope a LOT slower, however, and, while it's okay for planetary work (super-close-up) or double-stars, it's not so great for DSOs because it's so cursedly slow.

As for magnification, it doesn't quite translate perfectly with prime focus... it varies depending on the size of the sensor and how much of the image is hitting it, as well as just the focal length of the telescope. However, you can think of an ETX 125, with a focal length of 1900mm, as essentially the same view you'd get from a 1900mm lens attached to your camera. That's a LOT of magnification, but I'm not sure how that works out to telescope power nor what lens would be an equivalent view for that.... I'd have to do that math on that one.

--
N.

Post your files and links to http://www.rebelwithaclue.net
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[Mark Preston]

So how do I tell what kind of magnification I would be getting w/
no lens or eyepiece?

To give you an idea of the field of view when shooting something really close, this was taken with Meade ETX-125 and 300D, in prime focus:



This is the entire frame - it was my first attempt so it's not entirely in focus but hopefully you can get the idea. I found that the magnification was probably insufficient to get much detail out of the Orion Nebula, for instance.

Or should I just use the camera viewfinder (that can be a lot tougher to > look through depending on the orientation of the telescope).

You'll certainly need to look through the camera's viewfinder to focus - this can be tricky. The other problem is that you can't view objects directly overhead because the camera will collide with the base of the telescope tripod mount.

Hope that's useful,

Mark

 

[dare11]

Start with prime focus, that's the camera attached to the lens with a T-ring. It is easiest by far. Take your scope/camera out during the day and practice. At night focus on something bright and leave it set. Mak's typically have some focus creap when you change the angle of the scope so its best to pick something close to the object you want to photograph. It turns out that the moon is a bit too bright for my eyes so I prefer a bright start .

You can buy a good eyepiece projection adapter at Orion, http://www.telescope.com . This will give you more magnification but at the expense of greatly increased exposure times. This is clearly an advanced technique.

Focusing is difficult. There are knife edge focusers available for the Rebel at Hutech http://www.sciencecenter.net/hutech/canon/index.htm . They also explain how to use them and why you want one.

BTW the Rebel on your ETX will give about 61X. The Rebel acts like a 31mm eyepiece except that the view is a lot darker.

David

I've been looking at scopetronics.com for the parts I'll need to
hook my Digital Rebel up to my Meade ETX 125 telescope.

It looks like I should just need a T-adapter (meade part #64) and
T-ring specific to my camera to get started.

Now here's my question...

It appears the camera body hooks to the telescope without having a
camera lens attached. The camera is also not going through
whatever eyepiece I currently have on the telescope.

So how do I tell what kind of magnification I would be getting w/
no lens or eyepiece? Would there be a plain glass (no
magnification) eyepiece that could go in the telescope to mimic
what the camera will capture? Or should I just use the camera
viewfinder (that can be a lot tougher to look through depending on
the orientation of the telescope).

Or is there a different type of adapter I should be using that
actually puts an eyepiece in-line w/ what the camera is seeing?

Thanks for any pointers on this. It's just starting to warm up
enough that I'd like to start taking the telescope out again.

-Mark

 

[mickeymouse1]

Great, thanks to everyone for the explanations. Looks like it's both cheapest and easiest to get started w/ prime focus, so I'll plan on that route to start out.

-Mark

You can buy a good eyepiece projection adapter at Orion,
http://www.telescope.com . This will give you more magnification but at
the expense of greatly increased exposure times. This is clearly
an advanced technique.

Focusing is difficult. There are knife edge focusers available for
the Rebel at Hutech
http://www.sciencecenter.net/hutech/canon/index.htm . They also
explain how to use them and why you want one.

BTW the Rebel on your ETX will give about 61X. The Rebel acts like
a 31mm eyepiece except that the view is a lot darker.

David

I've been looking at scopetronics.com for the parts I'll need to
hook my Digital Rebel up to my Meade ETX 125 telescope.

It looks like I should just need a T-adapter (meade part #64) and
T-ring specific to my camera to get started.

Now here's my question...

It appears the camera body hooks to the telescope without having a
camera lens attached. The camera is also not going through
whatever eyepiece I currently have on the telescope.

So how do I tell what kind of magnification I would be getting w/
no lens or eyepiece? Would there be a plain glass (no
magnification) eyepiece that could go in the telescope to mimic
what the camera will capture? Or should I just use the camera
viewfinder (that can be a lot tougher to look through depending on
the orientation of the telescope).

Or is there a different type of adapter I should be using that
actually puts an eyepiece in-line w/ what the camera is seeing?

Thanks for any pointers on this. It's just starting to warm up
enough that I'd like to start taking the telescope out again.

-Mark

 

[Xipper]

I always intended to get into astrophotography but never did, this almost makes me want to move back towards giving it a try. I have an ETX-125 with tripod and several optics, just none of the camera mounts. I don't see me actually doing it, as the ETX has been in the box for ~ 7 years...perhaps its time for it to find a new home.

I love the images that can be produced though, just not sure if I have the patience to stay up that late...the curse of summer and living further from the equator I suppose. And the winter is just too cloudy/rainy here for that to work so well.

-- edit

Wow, I didn't mean to dig this back from the graves for this worthless reply. doh!

 

[strike1]

If you have a laptop and can connect that up to your camera when shooting, you can use EOS Utility to take a 30 sec picture of your target, enlarge the view and check focusing. I use that with my 350D all the time because looking through the viewfinder is usually awkward and my eyes are not good enough to tell if it is in focus that way. Another accessory that I find invaluable for focusing is a Bahtinov mask (you can purchase these for about $20 or find directions for making them on the net). It usually takes me between 3-6 pictures to nail the focus using this process, which is a lot better than it was using just the viewfinder.
--
Beautiful light is a precious thing