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So I finally figured out collimation and can shoot with Celestron EdgeHD 8". But I'm having trouble getting the Celestron Off Axis Guider working. I have a Zwo ASI 174 MM mini guide camera that I know works. I have the OAG pointing the correct direction. But my image for the Guide Cam looks like this, more or less no matter how much I push it in or pull it out.I'll try it tomorrow in the daylight but I figured I'd post this anyway though in case someone knows exactly what the issue is based on the screen shot, then I can fix it tonight. First clear night in a couple weeks. Any ideas? Thank you.  |
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Given the long back-focus of that OTA and where the OAG sits in the image train, you may find you still need to add an extension nose piece to your guide camera to hit focus. I believe you need 55mm back-focus from the pick-off prism to the guide camera sensor with that OTA/OAG combo. You may well still be able to achieve focus with the helical focuser all the way out and the camera mounted as far out as possible but it may be difficult with a short nose on the 174MM. You may also need to adjust the depth of the prism to ensure it is correctly in the light path. A little deeper will take it further from the guide sensor which should help you - keeping in mind any potential interference with your main sensor. It would be a good idea to try in daylight if you don't manage to resolve the problem at night as it can be hard to ensure the OAG is correctly positioned if you aren't picking up stars. Some good diagrams here: 93648-Off-Axis-Guider_Manual.pdf |
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| remove the extension of 174mm mini, let the cmos near the oag |
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| I have the exact same setup myself but I haven't had any clear nights to test it myself yet. I have however tested the camera with an OAG on my Esprit 100ED and found that I had to remove the black extension tube that is attached to the camera in order to get it close enough to the prism, as mentioned above here. |
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I have the exact same setup myself but I haven't had any clear nights to test it myself yet. I have however tested the camera with an OAG on my Esprit 100ED and found that I had to remove the black extension tube that is attached to the camera in order to get it close enough to the prism, as mentioned above here. Thank you. I don't have it in front of me but I think there are two tubes on it that unscrew. One is about 2 inches, one shorter. Do you mean remove both of them? I think one has the UV / IR filter in it. |
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Michael W. Dean:I have the exact same setup myself but I haven't had any clear nights to test it myself yet. I have however tested the camera with an OAG on my Esprit 100ED and found that I had to remove the black extension tube that is attached to the camera in order to get it close enough to the prism, as mentioned above here. Sorry, didn't even cross my mind. I only meant the larger one! |
