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Thread: Problem - Celestron Off-Axis Guider with ZWO ASI174MM Planetary Camera, Please help

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    Default Problem - Celestron Off-Axis Guider with ZWO ASI174MM Planetary Camera, Please help



    Hi,
    I have been having issues with my Celestron Off Axis guider that I need fixed. My equipment is a combination of very old and very new.

    I have a Meade 6.3 focal reducer attached to a very old Celestron 9.25 SCT Ultima OTA.

    To this, I have attached a new Celestron Off-Axis Guider (93648).

    Attached to the Off-Axis Guider, I have a DSLR and a ZWO ASI174MM Planetary Camera.

    The ASI174MM is off course my guide camera.

    I have been using this setup for a little less than a year. To get it to work, I had to have a custom adapter made to get the back focus just right.

    I can focus the DSLR at the moon or a distant terrestrial object and at the same time, have the off axis guider in focus. I am using PHD2.

    As seen in the images, PHD2 only sees the bright part of the chip. It seems more than half of my chip is being wasted on the guide camera.

    A related problem is caused by differing brightness values when moving from a bright area of the chip to the darker area of the chip.

    For instance, if I aim my ota at the moon and focus the guide camera. The area between the dark section of the image and the bright section will focus clear. Towards the bright section, the image will become blown out and maybe not focus as well. It is not evenly illuminated on the camera.

    The off axis guider has a pick off prism that collects light and sends it in the direction of the guide camera. I have experimented in moving this a little back and forth, but that didn't fix the problem. It is in a position where it captures enough light, but does not interfere with the DSLR image too much.

    The prism cannot be moved from side to side in the guider. It can only send the light in one direction. The guide camera cannot be moved around too much either.

    It seems that teh prism does not seem to direct the light directly on the sensor. As a result, my guiding is sub par.

    When I do guide, I only capture a star in the illuminated part of the picture and guide there.

    I wish to open up the entire sensor for guiding.

    The camera I am using a NOT the 174MM mini camera. It is the "Hockey puck" version of this camera. I bought that version of the camera so I can also use it on a filter wheel and try it in a different setup/one missing the off axis guider in the light path.

    In the attached images, I was probably aiming at a distant star or the moon. It was a while ago.

    Please advise how this is fixable? Is this a defective off axis guider. Do I need a different guide camera that has the sensor closer to the prism?

    Thanks,
    Jeff

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    Default Re: Problem - Celestron Off-Axis Guider with ZWO ASI174MM Planetary Camera, Please he

    I cannot seem to be able to add the pics. Each pic looks like the moon/terminator between a very bright area and black area, curved/an arc.

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    Default Re: Problem - Celestron Off-Axis Guider with ZWO ASI174MM Planetary Camera, Please he

    Hi Jeff,

    Due to a huge spambot problem, broken image uploading, and many other problems plus lack of admin support, the bulk of the active membership here have moved: https://www.theskysearchers.com/index.php

    Hope to see you there.
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