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PlaneWave CDK 14, Instructions Manual

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PlaneWave CDK 14 Instructions Manual Download Page 6

V20160909 

5 

 

 

 

Step 3: Setting the Primary-to-Secondary Spacing: 

 
The primary-to-secondary spacing is set at the factory. You will typically not need to adjust 
this unless the secondary has been moved.   
 
For your CDK optical system to perform as well as it should, the spacing between the 
primary mirror and secondary mirror should be set to an accuracy of +/- 1mm!  Fortunately, 
you won’t have to directly measure this spacing.  When the primary-to-secondary spacing is 
set correctly, the focal plane will land at an exact known distance behind the fully racked in 
focuser.  The Ronchi Adapter and Spacer places the Ronchi grating of the Ronchi Ocular 
precisely where the focal plane is supposed to be. 

Collimation knobs 
 
Central Secondary Spacing Bolt 

For the CDK12.5 there are four collimation screws and a central 

bolt used for spacing 

Summary of Contents for CDK 14

Page 1: ...PlaneWave CDK Telescope Instructions Setting the spacing and collimation for the CDK12 5 14 17 20 24 ...

Page 2: ... the factory and typically does not need to be adjusted unless it was moved after shipping Figure 1 The optical layout of the CDK system The system contains 4 elements the primary mirror the secondary mirror and a two element lens group Step 1 Collimation Spacing Adapters for the CDK 14 17 20 24 For CDK 12 5 proceed to Step 1b below If your CDK came with the optional Hedrick focuser 200340 attache...

Page 3: ...ock it down with the thumb screw e Place the barrel of a low power eyepiece for collimation or the Ronchi Ocular for spacing into the Ronchi spacer and lock it down with the thumb screw Step 1b Collimation Spacing Adapters for the CDK12 5 only 1 For the CDK12 5 the included Ronchi adapter will be placed inside the barrel of the focuser and locked down using the thumb screws 2 The Ronchi Spacer is ...

Page 4: ...or so that the defocused star moves in the direction of the fat side of the donut as shown in Figure 5 Re center the star and repeat this process until the donut hole looks centered as shown in Figure 6 See below for details on how to adjust the collimating screws Figure 5 An example of what you would see through a low power eyepiece for an out of focus out of collimation telescope To collimate th...

Page 5: ...person looks through the eyepiece while one person adjusts the collimating screws Attempting to do this alone can be quite difficult and frustrating If necessary you might try using a webcam with a 1 1 4 nosepiece such as the Celestron NexImage in place of an eyepiece With this setup you can watch the video stream from the camera while you make adjustments Note that the central spacing knob is not...

Page 6: ... mirror should be set to an accuracy of 1mm Fortunately you won t have to directly measure this spacing When the primary to secondary spacing is set correctly the focal plane will land at an exact known distance behind the fully racked in focuser The Ronchi Adapter and Spacer places the Ronchi grating of the Ronchi Ocular precisely where the focal plane is supposed to be Collimation knobs Central ...

Page 7: ...nd they become wider When the focal plane and the Ronchi grating are perfectly aligned no lines or perhaps one very wide line are visible See Figure 9 for an example In order to set the primary to secondary distance you will be moving the secondary mirror By adjusting secondary mirror distance you will be moving the focal plane relative to the fixed position of the Ronchi grating The job here is t...

Page 8: ... not need to adjust it If you see two or more lines you should move the secondary toward or away from the primary Determining the Direction to Move the Secondary To determine which way to move the secondary gently slide the Ronchi Ocular out of the spacing tube If the Ronchi reaches null as you do this the focal plane is too far back and you need to move the secondary mirror away from the primary ...

Page 9: ...e central bolt of the secondary assembly Rotate the central bolt in a clockwise direction For reference rotating turn moves the secondary 4mm which moves the focal plane 1 76mm in the case of the CDK17 4 Turn the collimation knobs in equal amounts until the assembly is tight again 5 Check the Ronchi grating and repeat this process as necessary until you get a null To move the secondary away from t...

Page 10: ...is means that the focal plane of the telescope is a set distance behind the backplate of the telescope The back focus for the various telescope models in shown in Table 1 below Backfocus from mounting surface of telescope backplate Back focus from fully racked in focuser CDK12 5 10 45 7 2 CDK14 11 09 8 09 CDK17 10 24 7 24 CDK20 8 81 5 81 CDK24 14 1 5 81 CDK700 12 8 5 Table 1 Shows the back focus w...

Page 11: ... your SecureFit adapter to mount it on the face of the focuser 2 The remaining four holes has screws that hold the face plate to the body of the focuser and should not be removed 3 There are also a series of set screws that are used to level the face plate relative to the image plane These set screws should not be removed or loosened in any way 1 SecureFit Mounting Screws 2 Face Plate Attachment S...

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