Camera Attachment

If you are going to take prime-focus pictures with your telescope you have to connect a camera.  Welcome to a topic that can be frustrating.  Different cameras, scopes, focusers and accessories may require a stash of parts that can boggle the mind.  You might find you cannot get your system to focus with a camera, or you may find that camera spacing is critical to eliminate coma, or the setup that works well with one scope doesn't work worth a hoot with another, or...  Fear not, you can get almost any camera to work with almost any scope with enough trial and error, and maybe some research.

The biggest hint I have is to eliminate any flex and loose spots in the system - use threaded connections any time you can.  Clamping parts together creates pivot points that can lead to a lot of frustration.    Simple thumbscrews in a focuser work OK with an eyepiece, but hang a heavy camera, maybe with other accessories from it, and it will be wobble city.  Clamp ring style thumbscrews are an improvement, but several I have are marginally better than a plain thumbscrew.

ScopeStuff is my favorite supplier of the odd threaded goodie I need for my scopes.  No one has the selection of weird hardware they do, and I believe they will custom make most anything.

We need a couple of definitions here:

T-ring - In the '50s, Tameron was making high quality manual camera lenses and wanted to be able to sell their lens to any photographer.  They developed the T-ring concept - an adapter that fits your camera on one side and a thread to fit their lens on the other side.  Manual lenses gave way to lenses controlled by the camera body and the T-rings almost died away, but astronomers snagged onto the concept and they live on.

T-thread - M37x0.75 thread for camera adapters.  Originally spec'd by Tameron, guess that's why it is called a "T-thread".
T2-thread - M42x0.75 thread, spec'd by Tameron a few years later.
These terms seem to be used interchangeably leading to some confusion when ordering parts.  Generally any parts you order will actually have the T2-thread. 

Nosepiece - a metal barrel that has a T2-thread on one end and the other end is 1.25" or 2" to fit your telescope.

Attaching the camera

T-ring First, you need to a way to attach the camera.  CCD cameras typically have a T2-thread for a direct connection.  SLRs required a T-ring.  They attached to the camera's bayonet mount and are internally threaded in a T2-thread.  Even though most of these pictures are of a SLR setup, my CCDs are attached to the telescope in the same manner, just minus the SLR's T-ring.
Nose piece The simplest camera connection is with a nosepiece threaded into the camera.  Allows the camera to be rotated to any position desired, however the connection may have some wobble depending on the quality of the focuser and nose piece.  Things can also start to slip apart as temps change.  Don't want that expensive camera to go crash!
ST-8E Best bet is to use threaded connections.  No wobble, no slip.  Here my ST-8E is threaded onto the TV 60is.  The items between the camera and focuser are a field flattener and a 10mm extension ring.  The flattener threads into the focuser, the thumbscrews lock it in place or hold an eyepiece if the flattener is removed.
Eyepiece t-ring Eyepiece camera Several companies make adapters to attach a T2-thread onto an eyepiece, then you attach the eyepiece to your SLR or CCD.  Great for extra magnification. 

I can't focus moving in!

Baader  First, check to see if you can physically shorten the chain somehow:

Eliminating a diagonal will remove a lot of length and wobbles.  Don't use one unless you have to.

A Newtonian can have the spider moved towards the mirror.  You will have to move it back up, or use extension tubes, to use an eyepiece again.

Using my Baader Herschel Wedge, I shortened the system over 25mm by changing how I connect the camera to the wedge.  Instead of using a nosepiece into the Click-Lock, I found Baader made a T2-ring to attach the wedge directly to my camera's T-mount. 

Powermate Invest in one or more Televue Powermates.  Yep, they ain't cheap, but they are designed to be parfocal with their eyepieces.  If your optical/camera system is too long to achieve focus replace the camera with an eyepiece.  If it will focus then a Powermate should solve the problem.  Also, sometimes you WANT the magnification the Powermate provides.  Barlows sometimes work too, but Powermates have optical properties that make them superb for imaging.  You can get a T2-thread adapter for the newer Powermates so the connection to your camera is solid.

Available in 1.25" & 2" versions, powers of 2 - 5x.

I can't focus moving out!

Extension tube  Extension tubes are your friend.  Available in 1.25" & 2", they can be had in a variety of lengths.  Threaded extensions are preferred; slip fit, like this one, can be made to work OK.  Experiment with different locations in the optical/camera chain.

I have horrible coma!

Extension ring Extension rings are your friend.  Due to the rising popularity of DSLR and large format CCD imaging many scopes have corrective optics incorporated somewhere in the optical path, often in the focuser.  They need a specific clearance to the imaging plane - have the spacing wrong and the coma can be significant.  Extension rings are available in a myriad of lengths.

The scope manufacture can tell you what the required space is and the camera manufacture can tell you what the front plate to chip space is.  Choosing the correct length extension is then simple.  Rarely you may have to experiment to figure it out yourself. 

Many focusers are 2" or larger.  use the largest extension rings you can, until you get to the camera, to keep things as rigid as possible and prevent vignette.

These examples are a 10mm from ScopeStuff and a 15mm from Baader.


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