Quote:
Originally Posted by frolinmod
Peter, what does your image train consist of? How close to the back of the scope are you placing the reducer? How far from the reducer are you placing your image plane? What spacers are you using, etc?
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The best way to describe the Optec Lepus setup is visually - have a look at these:
http://www.pbase.com/wjshaheen/optec...educer_testing
and
http://www.flickr.com/photos/59555496@N04/5587075807/
They are with an EdgeHD 11inch I believe.
With the AstroPhysics CCD Telecompressor, I hav tried it in 2 different ways:
1. Using the same AstroPhysics 2" adapter as shown in the pbase images above. This has 3 screws on the compression ring and I think gives a more secure and straight connection that a single-screw system. I attached the AP CCDTC to a couple of spcaers/adapters and set a separation between the mid-point of the AP CCDTC and the imaging plane of the camera at 101mm. I then inserted it as far into the AP 2" adapter as it would go without actually making contact with the HD correcting optical element nd srewed it up firmly but not overly so.
The downside of this method was that I had to rely on the standard focuser on the scope - not good because it has no micro-focus capability. If I persist with this method, I'll have to invest in a starlight or JMI Micro-Focuser.
2. I installed a JMI event horizon focuser on the back of the scope instead of the AP 2" adapter. This focuser is motorised and can produce smooth and precise focus via a handpad or ASCOM drivers. But the downside of using this focuser was that it meant the AP CCDTC would necessarily have to be backed off a bit furter back from the EdgeHD corrector than in method 1 above. Every mm back would impact on the coma. SO I set the focuser at the absolute minimum position, inserted the camera and the same adapters and AP CCDTC into the back of the JMI focuser and oved it as far in as I could without making contact with the optics inside the scope. I then backed if off a couple of mm and used the scopes standard focuser to get as close to focus as I could and then tweaked that minutely with te JMI until it was right.
I didn't like this methid overal because I think that the JMI's tube has only a single screw compressoin ring and in my opinion, throws the camera and tube slightly off the straight and narrow resulting in a slight tilt of the imaging plane. That made it hard to interpret any residual coma so the results of this second methid are ambiguous and inconclusive.
Overall, the simplest answer is method one with a Micro-Focuser.
Hope that helps.
Peter
Peter