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Thread: TV Ethoas eyepiece an answer for lightpollution ?

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    Default TV Ethoas eyepiece an answer for lightpollution ?



    Hi all,

    I live in a lightpolluted country and use now cheap eyepieces, because i didn't do many visual observations, but ,now i want to do more visual work because it is fun and i like it very much! I use for now my median quality C11 CT telescope and i have the intention to build me a traveler dobson with primary mirror of 0.25-m f/4.5 (glas for the mirrors are bought, and i start at end of this month).

    If i use an eyepiece with longer FL (say about 28mm) then the background is more lighting and i loose contrast. I read a lot the last weeks about eyepieces and it turned out that the TV Ethos can be dropped in focal length, because the wide view of 100mm, so that the magnification can be increased for the same FOV for a more, let say FOV 50° eyepiece. So the main question is if this eyepiece from, TV Ethos can be an (small) answer for the visual observer for the more lightpolluted area ? I don't have any TV eyepiece right now. What is want to observe is deepsky object an aslo some planets, but the quality of my scope and the seeingconditions here it comes more rare to observe planets (regrettable). But i hope that the traveler dobson can give me more good views in the future for planets. (but with a 0.25-m f/4.5 i doubt it). important to say, i like wide views very much.

    I considering to do the investment in good eyepieces like Televue, maybe Baader Morpheus and so on. All suggestions are welcome for buying me a set of eyepieces that can be used for C11 and dobson 0.25-m f/4.5, (note that I unfortunately can not do much many planets waiter feathers, I do hope to improve my C11 in the coming months). My funds are not infinite

    Thank you very much for your time,

    best regards,

    Erik
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    Default Re: TV Ethoas eyepiece an answer for lightpollution ?

    A good EP will improve your views and a wide field is desirable for most people, but nothing will help much with LP except moving to darker skies. You can do some things like covering your head with a towel while viewing and trying to stay out of direct light to help a little, but there is no substitute for dark skies.
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    Default Re: TV Ethoas eyepiece an answer for lightpollution ?

    I have a C8 so roughly like your C11 in how it responds to eyepieces

    With my 30mm eyepiece, the background is lighter and it appears than with my 13mm ethos that the background is darker and that can be pleasing with light pollution

    this is a function of the exit pupil size of a 13mm versus 30mm eyepiece, and not because it is a 13mm ethos

    on the other hand i have this cheap 20mm 72 degree eyepiece that looks pretty good. i think because of a fairly simple design and the field stop is visible.

    there is nothing magic about the ethos in regards to light pollution. They are fine instruments. There are cheaper wide angle alternatives.
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    Default Re: TV Ethoas eyepiece an answer for lightpollution ?

    I've moved to a dark sky site and used to live in a highly light polluted suburb. So I have relevant experience.

    When in the burbs I used the ES 100 series eps and they certainly helped. Your logic about greater AFOV getting the same TFOV and darkening the background is correct. It can help by as much as ~1.5 magnitudes I'd guess.

    But dark skies help more. I picked up more like 2.0-2.5 magnitudes by relocating. So relocating is more effective bur what you plan is a good idea. The ES 100s are a good alternative to TV Ethos and perform quite well.

    There is no reason why your Dob can't do well on planets btw. On nights of good seeing my Z12 has given wonderful details on the planets using TV Delos, Plossl, and especially BCO Orthoscopics. It's f5.

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    Default Re: TV Ethoas eyepiece an answer for lightpollution ?

    Quote Originally Posted by Ozman13 View Post
    A good EP will improve your views and a wide field is desirable for most people, but nothing will help much with LP except moving to darker skies.
    Hi Ozman13,
    thanks for your answer, you have 100% right, a dark sky, and if i haven't, is moving to dark sky the best option. Unfortunately i must drive at least mor than 100 km to get a darker sky. For a real dark sky, let's say background magnitude about 21, i must drive several hundreds of km. It's here terrible and it get's worse. My oldest sister has a second home in a very dark place in Spain. the reason why I want to make a traveller Dobson is to take it to Spain, so I got to enjoy the dark sky. btw: this is the design i want to make as traveller dobson but a 0.25-m instead of 0.2-m of the design.

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    Default Re: TV Ethoas eyepiece an answer for lightpollution ?

    Quote Originally Posted by not_Fritz_Argelander View Post
    I've moved to a dark sky site and used to live in a highly light polluted suburb. So I have relevant experience.

    When in the burbs I used the ES 100 series eps and they certainly helped. Your logic about greater AFOV getting the same TFOV and darkening the background is correct. It can help by as much as ~1.5 magnitudes I'd guess.

    But dark skies help more. I picked up more like 2.0-2.5 magnitudes by relocating. So relocating is more effective bur what you plan is a good idea. The ES 100s are a good alternative to TV Ethos and perform quite well.

    There is no reason why your Dob can't do well on planets btw. On nights of good seeing my Z12 has given wonderful details on the planets using TV Delos, Plossl, and especially BCO Orthoscopics. It's f5.
    Hi,

    thanks for the reply !
    The listed links in your reply AFOV and TFOV I understand better how the optics really works! The wide view so you can go lower in focus of the EP and get so a darker background and contrast, a seeming darker sky gives compared with an EP with longer focal length and, as example, a Plossl design. I have just a brand new Baader Morpheus 12.5mm and it performs very well, good eye relief (very comfortable !), wide view (wow), about the sharpness to the edges, this is hard to tell due the not exactly very sharp stars in my c11. But i presume these is OK as well. The ES 100s look the same as the TV Ethos series, only the price is more budget friendly .

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    Talking Re: TV Ethos eyepiece an answer for lightpollution ?

    Quote Originally Posted by astrobry View Post
    btw: this is the design i want to make as traveller dobson but a 0.25-m instead of 0.2-m of the design.
    there was something wrong with the link of the traveller dobsonian telescope here the correct one: Propdob Nano: een ultrakleine 20cm reistelescoop | Roelblog

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    Default Re: TV Ethoas eyepiece an answer for lightpollution ?

    Quote Originally Posted by astrobry View Post
    I have just a brand new Baader Morpheus 12.5mm and it performs very well, good eye relief (very comfortable !), wide view (wow), about the sharpness to the edges, this is hard to tell due the not exactly very sharp stars in my c11.
    It might be that the c11 needs collimating. SCTs have curvature of field of course so that might be it. Some eyepiece designs are soft. I'd want to track down the problem. My 9.25 Edge is sharp to the Edge of field but it's optics are designed to have flat fields.

    But i presume these is OK as well. The ES 100s look the same as the TV Ethos series, only the price is more budget friendly .
    The ES 100s are very similar in design. When you design your travel Dob be sure you allow for a mechanism to balance these heavy eyepieces!
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    Default Re: TV Ethos eyepiece an answer for lightpollution ?

    Quote Originally Posted by not_Fritz_Argelander View Post
    It might be that the c11 needs collimating. SCTs have curvature of field of course so that might be it.
    A quick check with a ronchi EP gives some small amount of astigmatism. I have yet to find out what the exact cause was, I thought turning the corrector plate with steps of 15 ° , collimating back and then view the image in / out focus to examine how to determine the best position of the corrector / secundary. I also think that the collimation isn't stable when changing the telescope position, each time with change of position, i get change of the collimation . Possible backlash from the primary mirror to the central axis ? This phenomenon is not really the topic eyepieces and subject of a new topic for " Celestron telescopes forum ".


    Quote Originally Posted by not_Fritz_Argelander View Post
    The ES 100s are very similar in design. When you design your travel Dob be sure you allow for a mechanism to balance these heavy eyepieces!
    Thanks for the tip, I definitely keep an eye on this .

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    Default Re: TV Ethos eyepiece an answer for lightpollution ?

    Quote Originally Posted by astrobry View Post
    A quick check with a ronchi EP gives some small amount of astigmatism.
    Very sorry to hear that.

    Thanks for the tip, I definitely keep an eye on this .
    On my Z12 solid tube a strong magnet with a carabiner and a 0.5 kg exercise weight does the trick. With an open truss design something that slides along a truss pole is safer.....
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