I just got the Orion variable adapter and EOS T ring to hook my 20D up to my Orion SkyView Pro 6 EQ telescope. However, I was unable to reach anything close to focus. The paper that came with the adapter suggested using a barlow. So, I put my 2x barlow in between and it appears to be possible to focus (although I can't really say that I've achieved that yet), but I appear to have a very small field of view. For example, I pointed it toward the Pleades and can only get a couple stars in the view. Is this normal? Do I have any other options to get a wider view? Help! -Bill
adapter question
Started by BillH101, 03/10/2005 02:52AM
Posted 03/10/2005 02:52AM
Opening Post
Posted 03/10/2005 03:26AM
#1
Bill,
There are so many adapters, I hesitate to give you directions, but, I believe the Variable adapter is designed to have an eyepiece in it. You slip the eyepiece into the big tube, hold it with a setscrew. Put one end of the adapter in the focuser tube and the other end holds the t-ring and camera.
This will give you a whole lot of magnification. Such a setup is used mainly for planets.
If you instead skip the eyepiece, and just stick one end in the focuser tube, and attach the camera at the other, you are just adding length to your tube.
I believe that same adapter can be used in a third way-- Unscrew the part that fits into the focuser tube from the larger adapter tube. You will notice that the back end of this little piece is just a set of t-threads. Screw your Eos T-ring onto it. Then mount your camera. Now you are using Prime Focus. In effect, your telescope is a long telephoto lens. NOw, it may be possible that you can't reach focus in this situation. You may need to add some tube length through another adapter, or more likely just try to insert your diagonal into the focuser, and the camera and adapter into the diagonal.
And of course, any of these methods can be used by adding a barlow--but you would be overmagnifying in many cases.
Good luck
Alex
There are so many adapters, I hesitate to give you directions, but, I believe the Variable adapter is designed to have an eyepiece in it. You slip the eyepiece into the big tube, hold it with a setscrew. Put one end of the adapter in the focuser tube and the other end holds the t-ring and camera.
This will give you a whole lot of magnification. Such a setup is used mainly for planets.
If you instead skip the eyepiece, and just stick one end in the focuser tube, and attach the camera at the other, you are just adding length to your tube.
I believe that same adapter can be used in a third way-- Unscrew the part that fits into the focuser tube from the larger adapter tube. You will notice that the back end of this little piece is just a set of t-threads. Screw your Eos T-ring onto it. Then mount your camera. Now you are using Prime Focus. In effect, your telescope is a long telephoto lens. NOw, it may be possible that you can't reach focus in this situation. You may need to add some tube length through another adapter, or more likely just try to insert your diagonal into the focuser, and the camera and adapter into the diagonal.
And of course, any of these methods can be used by adding a barlow--but you would be overmagnifying in many cases.
Good luck
Alex
Posted 03/10/2005 05:30AM
#2
Hi Bill, 
The instuctions at the site read;
"All models are composed of [COLOR="Red"]two detachable parts[/COLOR]: a [COLOR="Blue"]T-adapter for prime-focus photography[/COLOR], and an extension tube for eyepiece-projection photography. A setscrew in the extension tube holds the eyepiece in place"
It sounds like you are either using it incorrectly or you need an extention to reach focus. Although that 2" T-adapter for prime-focus looks like it's got a lot of room. Pull the camera back and if it reaches focus but isn't in the focuser you just need an extention. I have a Vixen R200SS and a D30 and there is a sweet spot where you need to be to reach focus. Are you aware that for prime focus you only use the 2" tube part and not the eyepiece projection pieces. I don't think you have to use a barlow unless it's what you want to do. It also adds backfocus and if you are connected to the 2" tube only and all the way in your focuser there shouldn't be a lack of back focus. If you are bottoming out in your focuser and not reaching focus then you may have a problem and need a shorter tube. I am not the Orion expert so I could be wrong.
Good luck and enjoy the D20. The 90 finder with the 2.5X is another helpful but expensive toy.
The instuctions at the site read;
"All models are composed of [COLOR="Red"]two detachable parts[/COLOR]: a [COLOR="Blue"]T-adapter for prime-focus photography[/COLOR], and an extension tube for eyepiece-projection photography. A setscrew in the extension tube holds the eyepiece in place"
It sounds like you are either using it incorrectly or you need an extention to reach focus. Although that 2" T-adapter for prime-focus looks like it's got a lot of room. Pull the camera back and if it reaches focus but isn't in the focuser you just need an extention. I have a Vixen R200SS and a D30 and there is a sweet spot where you need to be to reach focus. Are you aware that for prime focus you only use the 2" tube part and not the eyepiece projection pieces. I don't think you have to use a barlow unless it's what you want to do. It also adds backfocus and if you are connected to the 2" tube only and all the way in your focuser there shouldn't be a lack of back focus. If you are bottoming out in your focuser and not reaching focus then you may have a problem and need a shorter tube. I am not the Orion expert so I could be wrong.
Good luck and enjoy the D20. The 90 finder with the 2.5X is another helpful but expensive toy.
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