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Thread: Orion Short Tube 80A Observing Report - Testing Eyepieces

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    Smile Orion Short Tube 80A Observing Report - Testing Eyepieces



    A few days ago, I took out my Orion Short Tube 80A (ST80A) for a spin and did some eyepiece comparisons between the wide-field 66 degree FOVs that I normally use (Orion Expanse, Agena Wide Angle) vs. regular Plossls, which besides the Celestron 32mm, I rarely use for medium to high magnification observing. Bigz (Bigzmey) mentioned that these wide-field eyepieces produce “soft” views at higher magnifications compared to regular Plossls. Reviewing the literature, Phil Harrington in his “Star Ware” books gave unflattering comments about these Eps - fair contrast, so-so image sharpness, ghosting in the 6mm & 9mm versions and astigmatism in the 15mm & 20mm. In his classic review of the Short Tube 80A on Astromart (2007), Patricko sold off the 9mm and 20mm Expanse EPs that came with the scope and replaced them with higher-end Plossls for use on his scope. Personally, I have been using these as my main eyepieces for deep-sky and planetary observing the past 4 years and have been satisfied with their performance on my two 4.5" Newtonians.

    But given these criticisms, it was time to do some EP comparisons between these two types of eyepieces and see the differences for myself, if any. However, rather than using my workhorse Newts, I decided to test it on the ST80A, simply because the scope was conveniently lying near my work desk, getting very little observing time. A fast F/5, this scope should show a lot of chromatic aberration (CA) on bright objects like Jupiter, which might be a good thing for this test.

    First thing I did was check the lenses – slid off the dew shield, unscrewed the plastic (!?) objective retaining ring, and took out the crown and flint elements of the achromat:

    IMG_4701.JPG

    Note the erratic blackening of the lens edges, sloppily done with a black marker.

    After blowing off excess dust from the surfaces of both lenses, I reassembled the objective end, then wiped the smudges off the front end. I inserted a Cheshire refractor collimator into the focuser end and checked the alignment of the scope:

    IMG_4703.JPG

    A bit off center. I inserted the Orion EZ red-dot finder into the finder slot (the original 8x40 finder now lives with my C90 Mak), put the Orion Dielectric mirror diagonal on the focuser end (the original stock diagonal was a little off-collimation), and mounted the entire OTA onto the Astromaster alt-az mount.

    IMG_4704.JPG

    The testing spread over 2 evenings.

    On the first night (5-16-17), conditions were partially cloudy, but seeing was good. But before I began the test, took a cue from Not Fritz Argelander's last observing report on testing Ortho eyepieces and went to the local diner for a steak:

    IMG_0001 (4).JPG

    My first choice was prime rib, but they ran out. Note the book by Neil English (Classic Telescopes), which is a great read.

    All I wanted to do was test the eyepieces on Jupiter. Took out my Orion Expanse 9mm and Agena Wide Angle 6mm, along with the Orion Sirius 6.3mm and 7.5 mm Plossl EPs. I’ve used the ST80A on the planets once or maybe twice the entire 4 years I’ve owned this scope. Note that the inside of the dew shield (and OTA, but not visible) is flocked with black felt:

    IMG_4717.JPG

    First checked out the 9mm (44x) and then the 6mm (67x); CA was heavy, but the two equatorial bands were clear, with a hint of the southern belt using the 6mm. Very large FOV and very good eye relief, especially with the wide-field eyepieces used. Next up was the Plossl Eps. Jupiter looked noticeably sharper and cleaner using the 7.5mm (53x) and the 6.3 mm (63x), with less CA. Of course, eye-relief is not as good on these short focal length Plossls; I had to press my eye close to the glass to see the entire FOV. Ended the observing session when the power on the EZ red dot finder went out.

    Repeated the test on Jupiter the following evening (5-17-17). This time the OTA using the 32mm Plossl (12.5x) worked as the finder. Despite the clear evening, seeing conditions were average to below-average. The views through the wide-field or Plossl EPs were not as good as the previous evening; couldn't get the planet to focus sharply. In fact, the views through both types of eyepieces looked about the same, with heavy CA on both. Obviously, higher magnifications using the Barlow (1.5x and 2x) on these eyepieces didn’t help.

    In short, on the ST80A the views through the Plossls looked better than the wide-field Eps on nights of good seeing, but were virtually indistinguishable from each other in poor seeing conditions

    Not sure how the differences will be in a Newtonian or apochromatic refractor, where CA is virtually a non-issue. Will find out the next time I take out the 4.5” F/7.9.

    Once the EP testing was done, I did a star test on this scope, using the 6.3mm Plossl (63x). The out of focus view showed round concentric circles and the slightly triangular shape I used to get with this scope (which would have been a sign of pinched optics) was no longer there. Looking at Algieba (in Leo) I could see a peanut shape using the same 6.3mm; at 94.5x (with the 1.5x Barlow), the split was evident, though a somewhat messy view. I took out my Meade NG60 60mm F/11.7 using the star diagonal that came with that scope; the view looked cleaner at 93x (7.5mm Plossl):

    IMG_4722.JPG

    Looking forward to testing the eyepieces again on both Jupiter and Algieba, this time on a night of better seeing with the 4.5" Newt. But the ST80A deserves another test as well because as Neil English says, it is an iconic telescope.
    Terry
    ------------------------------------------------------------------------------------------------------------------------------------------------------------
    Scopes: Celestron Powerseeker 114EQ, Meade Polaris 114EQ, Orion Starblast 4.5EQ, Orion Short Tube 80A, and a whole bunch of others that get very little or no usage.

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    Default Re: Orion Short Tube 80A Observing Report - Testing Eyepieces

    Great comparison of eyepieces, Terry. Made me hungry for a nice steak too!
    I have the Agena version of the 9mm Expanse. It was the my second eyepiece and first actual eyepiece purchase. I have only used it in my XT 8 and found it to have decent performance in the center of the field of view, but towards the outside the view is not very sharp. It did see some good use in my scope until I got my ES 82 8.8mm. Pretty much no competition there and the 9mm is now just a placeholder in my eyepiece case.
    j.gardavsky and terrynak like this.
    Craig
    Telescopes: Zhumell Z12, Orion Skyquest XT8 Classic, Celestron Omni XLT AZ 102
    Eyepieces: ES 82˚ 18mm, 11mm, 8.8mm, 6.7mm, ES 70˚ 25mm, Sirius Plossl 25mm, Agena EWA 9mm, Zhumell 30mm
    Other: GSO 2x Barlow, 2" GSO 99% Dielectric Diagonal
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    Default Re: Orion Short Tube 80A Observing Report - Testing Eyepieces

    Thanks much for the narrative and comparisons on these eyepieces, Terry! A good read on a stormy night.
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    Bryan
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    Default Re: Orion Short Tube 80A Observing Report - Testing Eyepieces

    Thanks Terry for your comparisons using the ST80A. I have certainly enjoyed using mine. I have used various eyepieces but I haven't done an official documented comparison as yet. Thanks for sharing with us.
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    Ed
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    Default Re: Orion Short Tube 80A Observing Report - Testing Eyepieces

    Quote Originally Posted by Prowler75 View Post
    Great comparison of eyepieces, Terry. Made me hungry for a nice steak too!
    I have the Agena version of the 9mm Expanse. It was the my second eyepiece and first actual eyepiece purchase. I have only used it in my XT 8 and found it to have decent performance in the center of the field of view, but towards the outside the view is not very sharp. It did see some good use in my scope until I got my ES 82 8.8mm. Pretty much no competition there and the 9mm is now just a placeholder in my eyepiece case.
    Thanks for the comparison with the ES 82 Craig! I currently don't use or own any premium EPs - just the stock ones that came with the scopes (e.g. Celestron 32mm Plossl, Orion Expanse 9mm), or the cheaper Agena wide-field or Orion Sirius Plossls I purchased individually.
    Terry
    ------------------------------------------------------------------------------------------------------------------------------------------------------------
    Scopes: Celestron Powerseeker 114EQ, Meade Polaris 114EQ, Orion Starblast 4.5EQ, Orion Short Tube 80A, and a whole bunch of others that get very little or no usage.

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    Default Re: Orion Short Tube 80A Observing Report - Testing Eyepieces

    Quote Originally Posted by bladekeeper View Post
    Thanks much for the narrative and comparisons on these eyepieces, Terry! A good read on a stormy night.
    Thanks Bryan! Hope it was entertaining enough.

    Currently a clear night in So Cal; I plan to do some late night observing (around midnight) to catch Hercules and Lyra.
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    ------------------------------------------------------------------------------------------------------------------------------------------------------------
    Scopes: Celestron Powerseeker 114EQ, Meade Polaris 114EQ, Orion Starblast 4.5EQ, Orion Short Tube 80A, and a whole bunch of others that get very little or no usage.

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    Default Re: Orion Short Tube 80A Observing Report - Testing Eyepieces

    Quote Originally Posted by 10538 View Post
    Thanks Terry for your comparisons using the ST80A. I have certainly enjoyed using mine. I have used various eyepieces but I haven't done an official documented comparison as yet. Thanks for sharing with us.
    Thanks Ed! This was the first time I've ever tested and reported on eyepieces, albeit budget ones (which are the only ones I use). They complement my entry-level, "beginner' telescopes that I use. Actually, my ST80A is one of the more higher-end scopes I own, along with a few others that take up space doing nothing.
    Terry
    ------------------------------------------------------------------------------------------------------------------------------------------------------------
    Scopes: Celestron Powerseeker 114EQ, Meade Polaris 114EQ, Orion Starblast 4.5EQ, Orion Short Tube 80A, and a whole bunch of others that get very little or no usage.

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    Default Re: Orion Short Tube 80A Observing Report - Testing Eyepieces

    Thanks, Terry! A good read with good information!
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    Default Re: Orion Short Tube 80A Observing Report - Testing Eyepieces

    Quote Originally Posted by MistrBadgr View Post
    Thanks, Terry! A good read with good information!
    Thanks Bill! My ST80A has been used primarily for deep-sky work like what you did with the Messier hunt.

    Took it to a green zone site once and saw a bunch of galaxies fainter than 11th magnitude with it.
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    ------------------------------------------------------------------------------------------------------------------------------------------------------------
    Scopes: Celestron Powerseeker 114EQ, Meade Polaris 114EQ, Orion Starblast 4.5EQ, Orion Short Tube 80A, and a whole bunch of others that get very little or no usage.

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    Default Re: Orion Short Tube 80A Observing Report - Testing Eyepieces

    Thank you for your report Terry. When I read the part about taking out the lense cell...I clinched....but it all turned out well. Interesting pic of the lense edges. Really appreciate your testing report. Thank you.
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