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    Default Coma and other issues



    I have recently purchased the ZWO ASI1600MM Pro camera with Electronic Filter Wheel. I am using the Orion 8" Astrograph which requires me to use a Coma Corrector to produce a great image. I have successfully used my Baader MPCC Mark III with my Nikon DSLR and produced some nice images. I took the plunge to a new camera and have had nothing but issues since. As you look at my picture I took last night of a 5 minute exposure of the Horsehead Nebula in H_Beta you will see a number of issues. I would like confirmation that I have terrible coma and hopefully a little guidance as to the large circle at the bottom of the image and the smaller one near the top. I also attached my train from camera to coma corrector. From ASI's website they say 55mm is the optimal distance but clearly that's not the case. One modification that I had to do is moving my primary mirror a little forward as I could not achieve focus. Now I have plenty of back focus but I believe that moving my primary mirror forward also cause the large halo at the bottom and the smaller one at the top. ZWO has on their website for this camera an example train that I followed to the letter. https://astronomy-imaging-camera.com...a-solution.jpg If someone is an expert at where this Coma Corrector should be in the imaging train and can give me some guidance that is greatly appreciated.

    Thank you -Stu

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    Default Re: Coma and other issues

    I'm having a heck of a time trying to upload a 500kb image to this forum. Here's a link to my dropbox instead for both the 5 minute exposure and imaging train.

    Imaging Train
    https://www.dropbox.com/s/ciiuwi0otf..._4303.jpg?dl=0

    Horsehead
    https://www.dropbox.com/s/mj5nbhprul..._0131.jpg?dl=0

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    Default Re: Coma and other issues

    Hello Stu.

    Image uploading on this forum has been broken since November of 2018. Also, since about April of 2019, the spammer defenses are broken. As a result, we now have over half a million members, the majority of which are spam bots.

    Please see this thread: ***READ BEFORE SIGNING UP!!!*** This Forum is Going Under...
    Bryan

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    f/5; Celestron C6-R f/8; ES AR127 f/6.4; ES AR127 f/9.4; Stellarvue SV102T f/7; ES AR102 f/9.8;
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