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  1. #1
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    Default ETX-125 EP recommendations



    Hello all!

    I am new to the forums here and am looking for advice on what eyepieces/accessories I should get for my old telescope that I got back around 2001.

    So, as stated in the title, I got an ETX-125 (5" - f/15 - 1900mm focal length) w/ AutoStar back around 2001. When I first got it I used it maybe a handful of times but kind of lost interest mostly because I was a lot younger and didn't know what the hell I was doing (as in I wasn't able to see anything cool) . But now, 13 years later, I found the thing in my garage in great condition and want to get it setup again. Now, when it was first bought, I got the following Meade eyepieces with it:

    Series 4000 Super Plössl 26mm
    Series 4000 Super Plössl 9.7mm
    Plössl 6mm
    Plössl 4mm
    2x Telenegative Barlow

    However, I feel these are probably a bit outdated and I should look into some new ones that give better images, mostly because I wasn't too impressed with the images I saw and I didn't like how small the exit hole was for stronger EPs. I know there are a lot of criteria when it comes to eyepieces such as AFOV, coating, etc, but there's so many different types/brands of eyepieces out there I don't know where to begin. I've read about things like Ultra Wide Angle pieces or zoom eyepieces.

    So I guess I would like to ask a couple things:

    1. Is it worth looking into new eyepieces for this telescope considering its specs/age, as in will I still get great looking images through the scope with newer/better eyepieces or would it be better to just try and sell this scope and get a newer one?

    2. If it is would be worth it (as in the telescope still would produce great images with better eyepieces), then what would be a good set to get that would be good for viewing planets/moon in detail, but also deep-space objects clear too? I've looked at various things like Zoom Eyepieces (Meade 4000 zoom, Hyperion baader), and other individual EPs like Meade UWA/SWA or GSO brand. But I know there are a lot of other brands so any idea of what would be a very good starter set for most objects worth viewing would be helpful. (And of course not super duper expensive)

    3. If it would not be worth it, what would be some better replacement telescopes that have the GOTO functionality but also not super duper expensive?

    4. Is it a good idea to try and update the AutoStar firmware or is it a hassle for not much gain? (I do have the USB connector and the AstroFinder disc that came with the connector). Along with this question, is this a good software to use or is there a better one?


    Sorry for the long post, any help you all can provide would be awesome.

    Thanks!

  2. #2
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    Default Re: ETX-125 EP recommendations

    One thing to bear in mind is that a 5" scope is capable, on a good day, of up to about 250x magnification. Your 4mm and 6mm EPs go well over that (magnification = scope focal length / EP focal length), and unless seeing is excellent the 9.7 is about as high as I'd go. This may have something to do with your sub-par experience, as the smaller focal length EPs aren't giving you any extra detail, so the image will look fuzzy. The barlow lens you have could only be used with any decent results on the 26mm eyepiece (Giving you a 13mm EP, or 146x mag).

    Honestly, eyepieces don't really become "outdated." For example, the orthoscopic design was invented in the late 1800's and is still hailed as one of the finest planetary eyepiece designs there is. As previously stated, the issue is probably not in the type of EPs you have but rather the focal lengths. If your scope is in good condition, I see no reason to buy a new one. Most of the observation I do is with a low magnification. Even if I'm looking for something small, I will start at a low mag so that I can find it easier, then gradually work up more magnification until seeing causes the image to start looking bad, then back off a little. With the 475x magnification your 4mm EP is giving, you will hardly be able to see anything, much less find it.

    My personal recommendation would be to invest in a lower power eyepiece. Televue makes an excellet 40mm Plossl EP that sells for around $140 and would be an excellent choice. Other 40mm plossls could also be had for quite a bit less if this is too much to spend.

    Hope this helps a bit!

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  3. #3
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    Default Re: ETX-125 EP recommendations

    Hello and welcome to the forum. Stop by the introduction forum and tell us a little about you.

    First off your telescope is an excellent planetary scope due to it's design. You have picked a good time to dust it off too. Right now you have Jupiter, Mars, Saturn and the Moon to use for target practice. As far as the eyepieces are concerned the Meade kit eyepieces are not top of the line, but they are a long way from junk too. They are pretty decent. As Ravenhawk stated, The 6mm and 4mm are way too powerful for that telescope. That is why you were dis satisfied with the performance.

    I would keep the 9.7, you won't use it much but on the nights where the atmosphere is extremely stable you can get some use out of it. The 25mm is a keeper as well, you will use it a lot. If it were me, I would add a decent 30mm, and perhaps a 35mm, maybe even a 40mm since you have a lot of focal length to work with.

    I wouldn't go on the expensive side either. Have a look at some of the astronomy classified for some good used eyepieces. I have bought several used ones and all of them were in excellent shape.

    If your telescope works good I wouldn't bother updating anything. Make sure you train the drives and calibrate them as well. It will make your goto's accurate and tracking very good.

    Even though that scope is 13 years old, it is probably still worth in the range of 400 bucks if its in good shape and the electronics are good. I doubt you would find anything better in that size and price point.

    Good luck and clear skies to ya
    Jim
    Celestron C9.25. Atlas EQG mount. Canon 500D unmodded, Celestron ST80 guide scope, SSAG, Meade 6.3 FR, Thousand Oaks dew control with Dewnot straps. Zhumell 8/24mm Zoom, 2"Gso Superview 42mm, Meade 2"QX wide angle 30MM, Meade 1.25 EP and filter set. Tasco 10x50 Zhumell 20x80 bino and a few other odds and ends.
    Now where did I put that clear sky button!

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  4. #4
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    Default Re: ETX-125 EP recommendations

    Honestly my favorite ep for my etx125 is the factory 4000 26mm,Next in line is a cheap orion 40mm I have(even though 32 is the lowest useable)That scope has very impressive optics and I know of no other 5" That can beat its performance.I went head to head with a 150mm refractor and beat it,beats the celestron 127mm's also.

  5. #5
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    Default Re: ETX-125 EP recommendations

    You typically don't want an eyepiece with a focal length which is lower than the scopes' focal ratio unless you have extremely stable atmosphere (excellent "seeing" conditions). Go to cleardarksky.com and look at the clear sky charts (search for conditions in your area) to check the "seeing" conditions.

    For most locations, however... the magnification should usually not exceed the diameter of the scope when measured in millimeters (for your scope that's 125x) and it turns out that the the eyepiece which gives the same magnification as the scope's aperture is always the one where the focal length of the eyepiece is equal to the focal ratio of the scope.

    THAT means... most of the time you probably don't want to use an eyepiece with a focal length shorter than about 15mm.

    This means that your 4mm and 6mm eyepiece will probably never be useful and your 9.7mm will only rarely be useful.

    A 17mm or 20mm... those would be great.

    It's not actually necessary that you spend a lot of money on a nice eyepiece... your scope has a very high focal ratio. It turns out that high focal ratio scopes are extremely tolerant of eyepiece quality. Low focal ratio scopes are intolerant of low eyepiece quality and views will suffer... but not on your ETX-125.

    The Meade Plossl eyepieces that you have probably offer an apparent field of view of somewhere between 50 to 55º ... that's apparent, not "true". When you look into them you see the black sides of the eyepiece and the round field of view in the middle.

    You could try a wider angle eyepiece... Explore Scientific makes a 16mm and also a 20mm eyepiece (with 1.25" barrel to fit your scope) that offers a 68º apparent field of view. This offers a slightly more "immersive" view because your eye has to look farther to see the sides of the eyepiece. Those are around $139 each. William Optics makes a 15mm and also 20mm with a 72º apparent field of view (AFOV) for about $80.

    While the optics on your ETX are great, the motorized mount is a bit wobbly and breaks easily. Due to the cost and convenience, that was an extremely popular scope and probably the most common scope ordered by schools. But due to the build, it was also the most easily damaged. As you use it, don't over-tighten anything. When you snug the azimuth and altitude axis clutches, just tighten them enough so things don't slip -- but no more.

    Should the mount ever break, it's fairly trivial to un-fork it and the bottom of the optical tube has two 1/4"-20 threaded holes which are standard tripod-type holes. The scope can be mounted onto another mount.

    I unformed my ETX-125 not because the mount broke (my mount was fine) so that I could put it on a dual-saddle on a Celestron CG-5. I bought a Thousand Oaks Solar filter for it and used the ETX-125 as a white-light solar scope alongside an Ha solar scope so I could easily see the sun's photosphere alongside the sun's chromosphere for comparison. (incidentally... should you ever be interested in using it to view the sun with a safe solar filter, don't forget to either remove the finder or cover it. Also... the sun is not in the Autostar database but there's a way to define the sun as an asteroid. Never point it at the sun without a filter or your'll melt it (the ETX cannot take the heat unless it has a good filter.)
    Tim Campbell


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  6. #6
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    Default Re: ETX-125 EP recommendations

    Oh man, you guys are awesome, and very helpful!

    So what I am getting is that for this scope, I really shouldn't go for anything less than the 9.7mm that I have. And better yet I should stick with >= 15mm EPs because beyond that it will just be blurry because of the focal ratio of the scope. Which I guess also rules out the zoom eyepieces I was looking at considering half of the focal lengths will be more or less unusable, or is a zoom EP still something worth considering (like that Baader Hyperion or the Meade series 4000 zoom)?

    As for the Barlow lens, I could use it more successfully for the 26mm lens or anything higher. And I assume the Barlow lens I have is a good one and I don't need to invest in another one? Or are there any other recommended ones I should consider?

    In terms of these "wide angle" EPs, is there any drawback to them? because I'm not sure why I would even look at the ones with < 68º AFOV if its somewhat easier on the eye to use the wider ones or if it looks better. I guess what I am getting is that the actual amount of image seen can't actually increase, but it can be "widened" so it feels like there is more to look at. So would I just go for the ones with the largest AFOV?

    In terms of EPs I should invest in, I should basically look at a good 15mm, a 17-20mm, a 30mm, and a 32-40mm. And that should more or less cover the magnifications that would work best? Although, with the 2x Barlow lens, is it still a good idea to get one of each of the focal lengths? I mean I guess if the quality of the image is going to be noticeable better without the barlow lens like viewing through a good 15mm vs (30mm + 2x barlow), then I should definitely look into it.

    In terms of some specific brands, I should look at Explore Scientific, Tele Vue, maybe Meade? I was looking at things like Meade series 5000 SWA/UWA, and the Explore Scientific ones mentioned above, but so many choices! Any specific ones for the above mentioned focal lengths I should really consider or are highly recommended?

    Thanks again for your help everyone!

  7. #7
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    Default Re: ETX-125 EP recommendations

    Quote Originally Posted by Nevdawg View Post
    Oh man, you guys are awesome, and very helpful!

    So what I am getting is that for this scope, I really shouldn't go for anything less than the 9.7mm that I have. And better yet I should stick with >= 15mm EPs because beyond that it will just be blurry because of the focal ratio of the scope. Which I guess also rules out the zoom eyepieces I was looking at considering half of the focal lengths will be more or less unusable, or is a zoom EP still something worth considering (like that Baader Hyperion or the Meade series 4000 zoom)?
    The Meade zoom has a variable field of view depending on zoom factor. At it's narrowest, it's a 40º apparent field of view which is fairly narrow. Plossl eyepieces are usually in the low to mid 50's (e.g. 52º afov for example). Richer fields (wider fields of view) tend to look better, more filled with content, stars, etc. and provide a more "immersive" experience. It's sort of like going to an IMAX theater instead of going to a theater with a smaller movie screen. You actually have to "look around" to take things in and you don't notice the "walls" of the theater.


    As for the Barlow lens, I could use it more successfully for the 26mm lens or anything higher. And I assume the Barlow lens I have is a good one and I don't need to invest in another one? Or are there any other recommended ones I should consider?
    Correct. If you use a 26mm eyepiece on a 2x barlow then it's as if you used a 13mm eyepiece. You can think of it either as halving the focal length of the eyepiece or doubling the focal length of the scope.


    In terms of these "wide angle" EPs, is there any drawback to them? because I'm not sure why I would even look at the ones with < 68º AFOV if its somewhat easier on the eye to use the wider ones or if it looks better. I guess what I am getting is that the actual amount of image seen can't actually increase, but it can be "widened" so it feels like there is more to look at. So would I just go for the ones with the largest AFOV?
    There's a point where wide-field eyepieces NEED bigger eyepiece diameters in order to work. This depends on the apparent angle of view offered. For example the TeleVue Ethos (pretty much the premier ultra-wide angle eyepiece and VERY wide... 100º*AFOV and some are 110º AFOV but these things are also very expensive... $300-800 for a single eyepiece) can only offer these field of view in 1.25" diameter eyepieces up through their 13mm size. Their next size up is 17mm but that's a 2" eyepiece (your telescope will only accept 1.25" eyepieces.)

    Baader Hyperions have combo 1.25"/2" tubes. It's designed to fit into either size eyepiece seat. But they only go up to 24mm (that's their lowest power). The same is sort of true of the TeleVue Panoptics (TeleVue is a top-end eyepiece brand)... their 68º AFOV "Panoptic" eyepiece line can only provide that field of view in a 1.25" size up through 24mm. To go to any longer focal length they switch to 2" eyepiece size.


    In terms of EPs I should invest in, I should basically look at a good 15mm, a 17-20mm, a 30mm, and a 32-40mm. And that should more or less cover the magnifications that would work best? Although, with the 2x Barlow lens, is it still a good idea to get one of each of the focal lengths? I mean I guess if the quality of the image is going to be noticeable better without the barlow lens like viewing through a good 15mm vs (30mm + 2x barlow), then I should definitely look into it.
    Keep in mind that the difference in focal lengths seems more dramatic when you're in the lower focal lengths. Eg. suppose you were comparing a 5mm vs. 10mm... that 5mm worth of difference is going to be a 2x magnification difference. If, on the other hand, you had a 20mm vs. a 25mm eyepiece, that same 5mm of difference is only about a 20% difference.

    I have a 14" LX-200. The eyepieces I tend to use with that scope are a 41mm TeleVue Panoptic, a 27mm Panoptic, a 21mm TeleVue Ethos... and I also have a 17mm and 13mm Ethos (I have other scopes and eyepieces so I'm only mentioning the eyepieces that actually get used with that particular scope. OF THESE... I tend to use the 41mm and 21mm quite a bit... and then the 17mm and 13mm get used based on how good the seeing conditions are. So in other words... between the 13mm, 17mm, and 21mm... I tend to "pick one" and that's what I use for the night. If I want low power I use my 41mm and if I want high power I tend to use whatever I can get away with.

    Previously I only owned the 41, 21, and 13. But I found that there were many times when the skies couldn't handle the 13... but could clearly handle more than the 21. So I _eventually_ bought a 17.


    In terms of some specific brands, I should look at Explore Scientific, Tele Vue, maybe Meade? I was looking at things like Meade series 5000 SWA/UWA, and the Explore Scientific ones mentioned above, but so many choices! Any specific ones for the above mentioned focal lengths I should really consider or are highly recommended?

    Thanks again for your help everyone!
    TeleVue is top-notch... but they will be the most expensive. It's like buying a designer brand... except their stuff really is extremely good. Especially their wide-field eyepieces. Their Plossls will be the most affordable... but your ETX-125 won't be able to tell the difference. Their Pantopics will be considerably more expensive... the 19mm Pan is $250. The 24mm Pan is over $300.

    Explore Scientific are also very nice and their 68º AFOV eyepieces in, say, the 16mm and 24mm sizes are going to run around $140.

    I mentioned the William Optics brand in a previous post. Those eyepiece I mentioned (the William Optics SWAN eyepieces in the focal lengths appropriate for your scope) are of reasonably high quality and also a reasonable price tag.

    The Meade is going to be the most affordable. The quality is certainly good enough for your scope (low focal ratio scopes need really good eyepieces... but you have a high focal ratio scope so you won't notice the difference.)

    If you were going to buy anything better than the Meade then I'd probably consider them an investment toward future telescope purchases (ask around... if you stick with this long enough, you'll eventually own lots of telescopes.) ;-)

    AVOID buying eyepiece "sets". Those tend to come with just a few useful eyepieces and then many that you can't use... and they throw in some filters which also aren't very useful. Much better to pick and choose the two eyepiece that are actually VERY useful and stick with those for a while.
    Tim Campbell


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  8. #8
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    Default Re: ETX-125 EP recommendations

    I'll tell you the inexpensive eyepieces I use with my 125, Orion's Expanse 20, 15, 9, and 6mm eyepieces. Nice wide apparent fields and low prices. The little MCT is very forgiving of eyepieces, and these are darn near perfect in it.
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  9. #9
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    Default Re: ETX-125 EP recommendations

    Ah awesome, this is some good information. Thanks a lot guys!

    I'm gonna start searching online and comparing prices.

 

 

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