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    Default question about TV barlows



    I'm thinking of buying a 5X barlow, but after view TV's website I found that they only have 5X Powermate, which is more expensive than their normal barlows. While I saw a magnification chart about TV 3X that it can raise its magnification to 5X when the focus position is 100mm from the top surface. I'm not quite sure about the "top surface". If I make a 100mm-long tube to connect barlow and eyepieces, can I get a 5X effect? By the way is there any recommendation for a good barlow and eyepieces for a 80mm ED refractors? I'm new here so please help me to improve, THX!

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    Default

    HI Kid,

    If your scope is an 80mm, what is the focal length?

    I have a 102mm Ed refractor, and I use a 2x barlow and that is all I need. I have an f6.95 ratio. A 9mm EP with a 2x barlow gets me 157x, which is about all you can get on many nights, even with great optics. Some nights I have used the 5mm and the barlow, but it's rare and provides 284x.

    If you have an 80mm ED with good optics, on a good night you should be able to do better than double your aperture, so maybe 175x to 200x max (with great skies only).

    What EP's do you have now?

    Mike

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    Default

    Hi Kid,

    Yeah I can only go along with Mike's comments above. Why 5x?

    FWIW I have an ED80 f/7.5 which I mainly use as a Grab n Go.

    The only EPs I use in it are Vixen LVW 17mm (35x) for wide field, Vixen LVW 8mm (75x) as an all rounder, Vixen LVW 5mm (120x) for high magnification, and a GSO 2" 2x ED Barlow with the 8mm (150x) for maximum magnification, all over a William Optics 2" Dielectric diagonal

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    Default

    Hi Mike
    Thank you for your explanation. I have an 80mm ED with 480mm focus length, is that means that in most situations 175X is almost the limitation for my telescope? I live in Shanghai where air pollution is really serious and the seeing is rarely good. But I've taken a picture of Jupiter with my Jinghua(a Chinese brand) 3X barlow and SPC900NC camera, and I think it's OK. So I'd like to try a higher magnification with a better barlow. Thank you for your reminding me.
    I just started and I'm still a student, so I do not have a lot of money to spend. Right now I have several PL eyepieces: PL25, PL10, PL15. I just bought a TMB planetary 6mm eyepiece but haven't try yet.

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    Default

    Hi kid,

    Your equipment and its abilities to photograph the planets appear to be very good. If I were you I would not worry about getting a higher magnification factor barlow or powermate. In fact if you or a friend have another barlow you could experiment with stacking them together rather than purchasing new equipment. A 2x barlow inserted into a 3x barlow most likely will not generate 6x but its combined amplification factor may be close to the 5x which you are inquiring about. Seeing conditions will interfere greatly with that much magnification on your telescope but it would not hurt to experiment.

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    Default

    Thank you for your advice. I'll try a 2X with 3X together later. While I've heart that optic quality will decrease if lights pass through more lenses. I can see a little chromatic aberration in my photo of Jupiter, and I think it's because of the barlow lens. It's also a problem that it is difficult to make sure all of my equipments (barlows and the camera) are in a strict line, because the junction places are not perfectly fitted~~ Anyway I'll take your advice and have a try

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    Default

    Kid, sometimes when you add things that are long, you might run out of focuser travel--don't know for sure, but you might. If you must have a Barlow, and that's ok, get a 2x--and it doesn't have to be Televue. (Televue is VERY good quality, but you will pay for it). The Orion Shorty Plus 2x is a fine one. Also the Celestron Ultima and GSO Vinnie mentioned. There are others as well.

    I think you will like the TMB eyepiece. I have the 8mm.

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    Default

    hi kid

    i have a 3x televue and if you look at my plato pic in astrophos i have a web cam in the barlow and it does fine@ 1000mm
    Celestron C9.25 moonlte CS, explore scientific AR102, Skywatcher mak102mm, Orion short 80mm, Celestron Cg5, Canon t3, Philips spc900nc, dbk21au618 ,ZWO ASI224MC

    flicker. https://www.flickr.com/photos/74059838@N00/

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    Default

    Quote Originally Posted by ozzmozizz View Post
    hi kid

    i have a 3x televue and if you look at my plato pic in astrophos i have a web cam in the barlow and it does fine@ 1000mm
    Sounds great! But now I'm reconsidering my choice of TV barlows. It's expensive for me, and I'm not sure whether I need their outstanding qualities or not... I mean after all I'm just an amateur~
    Is there any brands of barlows with also good qualities but cheaper?
    80480ED, 80500 refractor/ LXD75, EQ3-2/ PL25, PL15, PL10, TMB 6mm
    Just started...

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    Default

    Hi Kid,

    Here is the one I use, and it has excellent properties:

    1.25" 2x Orion Shorty-Plus 3-Element Barlow Lens - Telescope.com

    Mike

 

 
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