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Thread: TS-Optics Imaging Star 102 mm f/5.1 - Any good?

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    Default TS-Optics Imaging Star 102 mm f/5.1 - Any good?



    Does anybody have anything good or bad to say about?

    TS-Optics Imaging Star 102 mm f/5.1
    Teleskop-Express: TS-Optics Imaging Star 102 mm f/5,1 - 6-Element-Flatfield-Apo-Teleskop

    I have a Celestron AVX mount and would be using it probably exclusively for astrophotography, although it can be used for visual if felt like it.

    Many thanks and clear skies :-)

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    Default Re: TS-Optics Imaging Star 102 mm f/5.1 - Any good?

    I do not have any experience with that exact scope, but according to the specs it looks like it would be very good. I do have the AVX and it should hold the scope very well. I image with my 102mm APO f/7 on mine.
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    The spec looks interesting - sounds like it's another attempt to produce something similar to a Tak fsq106 (106mm, f5) for folk who only need a full frame ish DSLR image circle.
    f5.1 is somewhat faster than most designs, so I suspect how well it performs depends on the quality - the Tak (which is a 4 element petzval variant) demonstrates that it's possible to achieve amazingly good results at that sort of speed, so if combining a triplet and flattener can manage something similar, it should be interesting.
    I think skywatcher did something similar in their Esprit range a few years back, then switched away from it - not sure why, and I may be wrong .

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    Default Re: TS-Optics Imaging Star 102 mm f/5.1 - Any good?

    Quote Originally Posted by jerryTheC View Post
    The spec looks interesting - sounds like it's another attempt to produce something similar to a Tak fsq106 (106mm, f5) for folk who only need a full frame ish DSLR image circle.
    f5.1 is somewhat faster than most designs, so I suspect how well it performs depends on the quality - the Tak (which is a 4 element petzval variant) demonstrates that it's possible to achieve amazingly good results at that sort of speed, so if combining a triplet and flattener can manage something similar, it should be interesting.
    I think skywatcher did something similar in their Esprit range a few years back, then switched away from it - not sure why, and I may be wrong .
    Hi Jerry,

    Another stupid noob question. I do not have a full frame DSLR. I have a Canon 600D. Would this scope not be suitable? I've not seen anywhere about what size sensor it is suitable for and TBH it's not something I've thought about until you mentioned it. I admit I'm not fully clear on how sensor size and telescope design are linked.

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    The only stupid questions are the ones you don't ask .

    It'd be fine with the 600D.

    Telescopes (and camera lenses) produce a usable image over a circular area - this is called the "image circle", usually measured by diameter. This will be limited by various design factors, including focuser size, baffle tubes in SCTs, add on or built in reducers/flatteners etc.

    As long as the image circle is big enough to completely cover your sensor, you're fine. There's no problem using a smaller sensor - that just uses the central part, but with a bigger sensor the image circle wouldn't completely cover it and you'd have unexposed black bits in the corners. (One example of where this is done deliberately are circular fisheye lenses, where the whole circle fits inside the frame).
    In the case of complex lens designs (like camera lenses) it can be possible to make them smaller/lighter for a smaller image circle - Nikon DSLRs use the same mount for both APS and full frame sensors, so you can use full frame lenses with an APS sensor camera just fine, but you'd get dark edges going the other way.

    For a full frame sensor, the diagonal size is around 42-43mm. Especially when you start looking at adding a reducer, there are a number of smaller scopes where the reducer is only designed to cover the smaller APS size.

    (The Tak fsq106 has a 4" focuser, and a flat field image circle of 88mm at the native f5 - so you could use it with some medium format cameras - and 44mm with the optional reducer or extender, so fine for full frame 35mm with those. It's also quite a bit heavier than the TS scope, and way more expensive.)

    The other thing you may want to consider is framing - how much of the frame various objects will fill. Longer focal length gives you a larger image scale, so objects will cover more pixels, while shorter focal lengths let you fit more in but objects cover fewer pixels. There's a free (pc) CCD calculator available from www.newastro.com where you can enter camera and scope details and see how big various objects will come out in the frame - or you can do something similar with the eyepiece plugin in stellarium, or the (non-free)
    Astro aid iOS app.
    It's the combination of (overall) sensor size and focal length that determines how much you can fit in the frame, and focal length and individual pixel size that gives you the arcseconds/pixel resolution (from which you can work out how many pixels an object will cover).

    At 520mm (or 530mm for the FSQ) it's great for widefield views of big objects (and medium field views of average objects when used with a small sensor CCD), and the small image scale means you're not affected much by seeing conditions - but you may want to check how big the sort of targets you want to image will come out - while you can always crop the results down (and its the number of pixels that counts in the end) if you find that you've always got lots of space left around the target, then you might think about whether a slower scope of the same aperture and a longer focal length (and thus bigger images, but needing longer exposures) would suit you better - everything's a trade off, and you want to find the best balance for the sort of things you want to do .
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    Default Re: TS-Optics Imaging Star 102 mm f/5.1 - Any good?

    Thanks for the CCD calculator , very useful ( though it seems out of date with 'scopes and cameras ) .

    Similar here on Astronomy Tools ... https://astronomy.tools/calculators/field_of_view/
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    The CCD calculator has been around for a long time, and the author may not have updated the lists - but it's easy to add extra items. Because it was designed for CCDs, I think the image size is limited to 1degree max, but it's still very useful.
    Atik also do a similar free iOS app - might be limited to the Atik cameras, but it won't run on my old iPod touch so I'm not certain.
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    Default Re: TS-Optics Imaging Star 102 mm f/5.1 - Any good?

    Quote Originally Posted by jerryTheC View Post
    The only stupid questions are the ones you don't ask .

    It'd be fine with the 600D.

    Telescopes (and camera lenses) produce a usable image over a circular area - this is called the "image circle", usually measured by diameter. This will be limited by various design factors, including focuser size, baffle tubes in SCTs, add on or built in reducers/flatteners etc.

    As long as the image circle is big enough to completely cover your sensor, you're fine. There's no problem using a smaller sensor - that just uses the central part, but with a bigger sensor the image circle wouldn't completely cover it and you'd have unexposed black bits in the corners. (One example of where this is done deliberately are circular fisheye lenses, where the whole circle fits inside the frame).
    In the case of complex lens designs (like camera lenses) it can be possible to make them smaller/lighter for a smaller image circle - Nikon DSLRs use the same mount for both APS and full frame sensors, so you can use full frame lenses with an APS sensor camera just fine, but you'd get dark edges going the other way.

    For a full frame sensor, the diagonal size is around 42-43mm. Especially when you start looking at adding a reducer, there are a number of smaller scopes where the reducer is only designed to cover the smaller APS size.

    (The Tak fsq106 has a 4" focuser, and a flat field image circle of 88mm at the native f5 - so you could use it with some medium format cameras - and 44mm with the optional reducer or extender, so fine for full frame 35mm with those. It's also quite a bit heavier than the TS scope, and way more expensive.)

    The other thing you may want to consider is framing - how much of the frame various objects will fill. Longer focal length gives you a larger image scale, so objects will cover more pixels, while shorter focal lengths let you fit more in but objects cover fewer pixels. There's a free (pc) CCD calculator available from The New CCD Astronomy Home Page where you can enter camera and scope details and see how big various objects will come out in the frame - or you can do something similar with the eyepiece plugin in stellarium, or the (non-free)
    Astro aid iOS app.
    It's the combination of (overall) sensor size and focal length that determines how much you can fit in the frame, and focal length and individual pixel size that gives you the arcseconds/pixel resolution (from which you can work out how many pixels an object will cover).

    At 520mm (or 530mm for the FSQ) it's great for widefield views of big objects (and medium field views of average objects when used with a small sensor CCD), and the small image scale means you're not affected much by seeing conditions - but you may want to check how big the sort of targets you want to image will come out - while you can always crop the results down (and its the number of pixels that counts in the end) if you find that you've always got lots of space left around the target, then you might think about whether a slower scope of the same aperture and a longer focal length (and thus bigger images, but needing longer exposures) would suit you better - everything's a trade off, and you want to find the best balance for the sort of things you want to do .
    Thanks for the thorough explanation. I already have an edge 8 hd sct 2032 focal length or 1422 with the reducer so i was thinking that this refractor would compliment it.

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    Yes, it should complement the SCT nicely - and also work as a nice widefield scope visually too.
    One other even faster (around f2) alternative would be to look at a hyperstar unit for the edge, but since (I think) you need at least a 9.25 or larger to use a DSLR with one, the hyperstar plus a suitable CCD camera would be quite a bit more expensive.
    (And I'm a refractor fan anyway - it's hard to beat the pinpoint jewels on a black velvet background view that you get with a good refractor, even if reflectors and cats make bigger light buckets )
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    Default Re: TS-Optics Imaging Star 102 mm f/5.1 - Any good?

    Quote Originally Posted by jerryTheC View Post
    Yes, it should complement the SCT nicely - and also work as a nice widefield scope visually too.
    One other even faster (around f2) alternative would be to look at a hyperstar unit for the edge, but since (I think) you need at least a 9.25 or larger to use a DSLR with one, the hyperstar plus a suitable CCD camera would be quite a bit more expensive.
    (And I'm a refractor fan anyway - it's hard to beat the pinpoint jewels on a black velvet background view that you get with a good refractor, even if reflectors and cats make bigger light buckets )
    How embarrassing. I spelled complement wrong. Woops.

 

 

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