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Thread: Explore Scientific problem?

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    Default Explore Scientific problem?



    I bought a Orion xt8 a couple of weeks ago and being a true gear head I had to get an “upgraded” eye piece pretty soon after. I did some research on here and elsewhere and decided that for the money an Explore Scientific 8.8 mm 82 degree would be my best choice for a higher magnification wide view EP. I’m pretty disappointed about the view. I’m not able to get it to focus clearly at all. My Orion 25 mm EP and a 2X Barlow puts it at 96x magnification and is very clear. The explore scientific 8.8 with no Barlow is 135x magnification and sucks honestly. Maybe that extra magnification is the tipping point but it seems unlikely. Is it possible that the 82 degree EP is too much for this type of scope? I’m having a hard time wrapping my head around how you can get that wide of an angle out of a 5’ tube.

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    Default Re: Explore Scientific problem?

    Your skies may not have been steady enough to use the extra magnification.
    The eyepiece has a Apparent Field Of View (AFOV) of 82° that is not the True Field Of View (TFOV) which would be 0.603°, slightly larger than the full Moon.

    I would also check the collimation of your telescope to be sure it is accurate.
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    Default Re: Explore Scientific problem?

    A couple of things...

    Your scope has a focal ratio of f/5.9. Any eyepiece below twice that number, expressed in millimeters, is going to need pretty good seeing conditions to come to focus. The 8.8mm eyepiece fits within that zone. If your seeing conditions were suspect, give it a chance for another night. (Or look at the moon. You can focus a coke bottle on the moon.)

    Secondly, your last sentence leads me to think that you are confusing the 82o AFOV of the eyepiece with the FOV you'll get from the scope... TFOV, or True Field of View.

    To get the TFOV of the 8.8o eyepiece in your scope, take the AFOV/magnification, or...

    82o/135 = 0.61o

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    Default Re: Explore Scientific problem?

    Quote Originally Posted by Gabby76 View Post
    Your skies may not have been steady enough to use the extra magnification.
    The eyepiece has a Apparent Field Of View (AFOV) of 82° that is not the True Field Of View (TFOV) which would be 0.603°, slightly larger than the full Moon.

    I would also check the collimation of your telescope to be sure it is accurate.
    Spot on, when you ramp up the magnification the collimation becomes even more critical.
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    Default Re: Explore Scientific problem?

    ES82 8.8mm is a very sharp EP. Most likely the viewing conditions prevent you from getting a sharp focus. What was your target?

    Try your EP during daytime and see if you can get sharp focus on some far away tree or house.

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    Default Re: Explore Scientific problem?

    Collimating may be a legitimate issue. I’ve never messed with it. Would it be reasonable to have a clear view with the25 mm and 2X Barlow and then fall off the cliff with the 8.8 by its self? I’ve tried viewing the moon and random stars, same result.

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    Default Re: Explore Scientific problem?

    If you had a problem with the 82° AFOV eyepiece being too wide, the problem would be out along the edges of your FOV (Field of View). The center would still come into focus.

    1) Have you checked your collimation?
    2) What I really suspect is the eyepiece is sitting to far out away from the secondary. Could be your eyepiece is not sitting all the way down in the 2" to 1.25" adapter or the adapter and focuser together are just are too tall. Orion and several other companies have low profile focusers just for this problem. The Orion Low Profile focuser is 10mm (0.4") shorter than the standard height focuser. Then when you add the standard 2" to 1.25" adapter the difference is even greater. Probably close to 19mm (3/4" or 0.75"). The Low Profile focuser has the 1.25" adapter recessed into the focuser, so it doesn't raise the eyepiece but a very small amount if at all.

    A 2" eyepiece may work too, as you can get rid of the 2" to 1.25" adapter and have the eyepiece further in. But they are more expensive.
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    Default Re: Explore Scientific problem?

    If you defocus on a star with 25mm with or without the Barlow you should be able to check collimation.
    A round donut means you have good collimation, a lopsided donut means you don't .

    Look at the pictures at
    Collimation

    If you have never collimated, it is most likely the issue.
    If you bought the Xt8 new it probably came with a collimation eyepiece. You can use that to check collimation.
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    Default Re: Explore Scientific problem?

    Yep... I’ve got a jacked up donut. Thanks for the help everyone. I will need to buy a collimation tool.

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    Default Re: Explore Scientific problem?

    Quote Originally Posted by Codydorris1 View Post
    Yep... I’ve got a jacked up donut. Thanks for the help everyone. I will need to buy a collimation tool.
    Your XT8 should have come with a collimation cap. These are great for general checking of your collimation (check and verify mine at setup each time with a collimation cap).

    For getting your secondary mirror optimally centered, a Cheshire collimating eyepiece is excellent.

    https://agenaastro.com/agena-1-25-co...eflectors.html

    https://agenaastro.com/rigel-systems...-eyepiece.html

    I've got a laser collimator too, but that had me chasing my tail. It needs collimating itself. Once these are properly dialed in, they can be effective as well.

    I also have the ES 82º 8.8mm eyepiece, and I've always enjoyed it with my 12" dob. It serves as a wonderful back up to my favorite 11mm eyepiece with faint galaxies, and it puts up a fine view of Jupiter and Saturn too.
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