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Thread: Siebert Telecentric Barlow first light

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    Default Siebert Telecentric Barlow first light



    I had a surprise clear(-ish) night, the first in three weeks, so an opportunity to try out my new Siebert 3x Telecentric Barlow.

    My reason for ordering the barlow was to be able to take pictures of planets. With an 800mm focal length, Mars at prime focus was a mere 10 pixels across; Saturn was 32 pixels. So some magnification was essential. I opted for the 3x barlow since, by my approximate calculations, it would put both my scope and my camera at their respective performance limits. ANd I didn't want to have such a long effective focal length that my guider couldn't handle it. So, with the bartlow, my scope becomes an f/12 2400mm scope, like an SCT at much lower cost.

    Target selection was a challenge. Saturn is long gone from my limited sky, and it will be a while before Jupiter comes around. So, I decided to re-do M57. I just imaged it a few weeks ago, so I can remember how I processed it to get a good comparison. It is high in the sky now, making for good imaging conditions.

    My session was challenged by random clouds that obscured Polaris when I wanted to do my polar alignment (and which eventually cut short my session), and by a flaky USB hub that forced me to re-cable my setup and reboot my laptop. The sky was still light at 23:00 when I was setting up. Seeing and transparency were both excellent, and if it hadn't been for the @#$% midnight Sun and the clouds, it would have been a perfect night.

    I was pleasantly surprised at the barlow's performance. I shouldn't have been, because Harry Siebert's optics are legendary. The Telecentric acts as a field-flattener, so a Paracoor is not necessary when using it. That is a good thing, since the stack in my focuser would be unmanageably long with both the barlow and the Paracorr. As it is, the Siebert is a long unit. And, being a barlow, it solves the back-focus problem, which, on my astrograph, means that I have to use it with an extension tube because I have too much back focus for it.

    As far as results go, my image was just a quick and dirty grabbed between clouds. The bright stars are a bit blobby, perhaps because my guiding was at its limit. Nex time, I'll pay a little more attention to balancing, which should help. But there is no trace of coma at the edges. And M57 is a nice big ring, which bodes well for planetart imaging. I'll never get the kind of planetary images that the folks with barlowed SCTs get, but I might be able to get some that are recognizable.

    Here are M57 without the barlow and with it. Both images are full-frame, uncropped.
    M57-s2-p2-800px.jpg M57-s1=p2-800px.jpg
    Last edited by KathyNS; 06-17-2012 at 04:45 PM.

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    DSO AP: Orion 200mm f/4 Newtonian Astrograph; ATIK 383L+; EFW2 filter wheel; Astrodon Ha,LRGB filters; KWIQ/QHY5 guide scope; Planetary AP: Celestron C-11; ZWO ASI120MC; Portable: Celestron C-8 on HEQ5 pro; C-90 on wedge; 20x80 binos; Etc: Canon 350D; Various EPs, etc. Obs: 8' Exploradome; iOptron CEM60 (pier);
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    Default Re: Siebert Telecentric Barlow first light

    I have a 10" Skywatcher Dob., a 13 mm Ethos and was thinking about a Siebert Barlow. Which Siebert would you recommend? How does the quality of the Siebert compare to the Televue barlow. Thinking maybe 2X since visual is my game right now.
    Thanks.

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    Default Re: Siebert Telecentric Barlow first light

    I can't really do comparisons, since I have only ever used a cheap 1.25" Antares barlow vefore. I have heard that Siebert barlows, especially the Telecentrics, are comparable to Televue Powermates. I don't know that from personal experience, though. It is probably true.

    I determined which one to get based on my needs. I needed considerable magnification for planetary imaging, without exceeding the diffraction limit of my scope, the resolution of the camera, or the capability of my guider. Your mileage may vary. You should determine what your needs are first, and then look for a product that matches them.

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    DSO AP: Orion 200mm f/4 Newtonian Astrograph; ATIK 383L+; EFW2 filter wheel; Astrodon Ha,LRGB filters; KWIQ/QHY5 guide scope; Planetary AP: Celestron C-11; ZWO ASI120MC; Portable: Celestron C-8 on HEQ5 pro; C-90 on wedge; 20x80 binos; Etc: Canon 350D; Various EPs, etc. Obs: 8' Exploradome; iOptron CEM60 (pier);
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    Default Re: Siebert Telecentric Barlow first light

    Thanks for the reply. I was mostly concerned with the comparison in quality. Looks like the Siebert might fit the bill.

 

 

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