Different approach for my EP collection?

[JJDOBBER79 (Jas)]

I think I am going to try a different approach to an EP collection. Let me explain. Recently, I have been on a bit of a spending spree buying up on premium EP’s. I now have a N16T2, a xw10, a Tak LE 24mm and a Parks 32mm plossl. I definately wouldn’t say that I am disappointed with any of them, but none of them stand out either. I find I enjoy the views equally in all of them which I find interesting given that they are all very different in price, FOV, sharpness etc. Those of you who have helped me before on this forum will know that I am still very new to atronomy so I am wondering if maybe my observing skills are not at a level to be able to instantly recognise the areas in which these EP’s individually excel. So, I have decided to notch it back a little.

I have recently read numerous posts on different forums by people praising the TV plossls and claiming that it is the same glass and coatings as used in their premium EP’s. If this is correct , then it would be fair to say that all we are paying extra money for is a wider field, and seeing as this is something that I obviously don’t value at the moment, I feel I may be wasting my money.

So…… I have decided to keep my parks 32mm, and I have just bought a 20mmTV plossl, I will use these barlowed with my TV 2x barlow (that I already have) and I will be purchasing a TV 3x barlow. The 3X will be to achieve a high power 6.6mm equivalent out of the 20mm because I figure I don’t like looking through a pin hole so would rather use a 20mm piece of glass and barlow it and also I don’t have a problem or find it a nuisance using barlows like others do. This will give me 30, 20, 15, 10, 6.6 which I figure is all I need and it will be my main collection which will not change. Now… I figure (going through the IIS archives and checking prices) that I have about $750 in value in my 3 premium EP’s, and the 3x TV barlow will cost me about $100. With the extra $600, I plan to always hold 1 premium Eyepiece which I will buy on the used market and sell when I have had ample time with it. (not every week, but maybe 2 or 3 times a year) I figure that I wont lose money doing this, providing I always get them at a reasonable price, because the premium EP’s tend to hold value. I have 2 reasons for doing this, 1.) It will allow me to try pretty much any eyepiece on the market which will hopefully allow me to find what I like. 2.) I can kind of tailor this choice to what targets are visible at the time or at least the ones that I like to observe regularly.

The only down side I see to this is the risk of getting stung buying something damaged on the used market, and also losing a bit on postage. I am interested in others thoughts on this particularly any from others who use a similar approach.

I am thinking I should be able to get a 13mm (or maybe 17mm) ethos to start with for $600 used. The 100 degrees will probably settle the “do I appreciate wide FOV” question.

[AG Hybrid (Adrian)]

Hi Jas,

Interesting post. Eyepieces are ultimately a personal choice. However, I will say this. If your not satisfied with the view a Pentax XW 10mm gives you. I'm afraid your next accessory will have to be a CCD camera and a laptop. Because visually. The Pentax 10mm XW and less focal lengths with the TV Delos equivalents are about as good as it gets visually.

Also, you didn't mention what scope(s) you are using.

[JJDOBBER79 (Jas)]

Hi AG,
I wouldnt say that I am not satisfied with the view, i just feel that I didnt look through the xw and go. Maybe I am expecting too much. I didnt get this from the nagler or the tak either and to be honest I am indifferent to the 70/84/whatever degrees the tak is. I find that I dont even notice it, I tend to look at the target and I dont care how big a chunk of sky is around it because I am not even looking there. Does that make sense?
I am keen to test this theory with an ethos though, I may completely change my tune after using one of those. who knows? But the nagler for example is an older one, so a new plossl will probably have the same optics, (or possibly better) bar the FOV at a fraction of the price. I think the TV plossls are about the same degrees as the tak anyway. I definately dont take the xw out of the focuser, put the tak in and want to put the xw back in. Maybe I am just an oddball.

[astro744]

Originally Posted by JJDOBBER79

I have recently read numerous posts on different forums by people praising the TV plossls and claiming that it is the same glass and coatings as used in their premium EP’s. If this is correct , then it would be fair to say that all we are paying extra money for is a wider field, and seeing as this is something that I obviously don’t value at the moment, I feel I may be wasting my money.

In the case of Tele Vue, the extra money is for a highly corrected wider field so much so that in a Newtonian you actually see pure coma (a function of the primary mirror) and no other aberration and then all you need to eliminate the coma is a Paracorr if it bothers you for say f5 and under. There are many other branded wide field eyepieces on the market and some have considerable field curvature and off axis astigmatism. Surprisingly a Paracorr can improve the view with some of these eyepieces but in the end it comes down to what you're prepared to accept as far as off axis aberrations go.

My take is this; if I want an 80 deg field I want it all available to me not just 50 degrees of it otherwise I too would use a Plossl. Also when an eyepiece has significant field curvature then there is a significant part of the field that is out of focus. Any faint galaxy for example would be invisible in the outer part of the field.

Note highly corrected eyepieces such as Tele Vue perform well on any telescope. However some less well corrected eyepieces perform well on telescopes with longer focal ratios.

Your idea of using Plossls is fine but note the eye relief extends out further when using a Barlow with an eyepiece and eye placement and vignetting become an issue in say 30mm and over. A Powermate would eliminate this problem.

Buying and selling all the time is a personal choice. Some people do it all the time for various reasons and sometimes end up buying the same eyepiece back. It depends on what you want or need at the time but you should also think of what you may need in the future. You don't want to have to pay twice for an eyepiece you already had once.

[astro744]

Originally Posted by JJDOBBER79

Hi AG,
I wouldnt say that I am not satisfied with the view, i just feel that I didnt look through the xw and go. Maybe I am expecting too much. I didnt get this from the nagler or the tak either and to be honest I am indifferent to the 70/84/whatever degrees the tak is. I find that I dont even notice it, I tend to look at the target and I dont care how big a chunk of sky is around it because I am not even looking there. Does that make sense?
I am keen to test this theory with an ethos though, I may completely change my tune after using one of those. who knows? But the nagler for example is an older one, so a new plossl will probably have the same optics, (or possibly better) bar the FOV at a fraction of the price. I think the TV plossls are about the same degrees as the tak anyway. I definately dont take the xw out of the focuser, put the tak in and want to put the xw back in. Maybe I am just an oddball.

Maybe you're a purist and a simpler eyepiece design is for you.

The Tele Vue Plossls are very nice.

Also to consider would be Vernonscope Brandons. See http://www.vernonscope.com/ They are available individually or in sets.

Another outstanding alternative would be University H.D. Orthoscopics. See http://www.universityoptics.com/

No wide fields for any of the above just pure quality glass!

[JJDOBBER79 (Jas)]

AG, I am using a f5 12" lightbridge

[MortonH]

Consider a 14mm Delos. Very nice.

[Varangian (John)]

Originally Posted by JJDOBBER79

AG, I am using a f5 12" lightbridge

I've used the Tele Vue plossls at f5 and find them very satisfying. I think your position of using a 20mm plossl (so retaining good ER) and barlowing it is a good one. At f5 I personally struggle to find a good EP without considerable field curvature over 20-25mm focal length without a paracorr.

[JJDOBBER79 (Jas)]

Thanks guys,
Hopefully I will get to all of those, astro. I have even considered giving clave a go for a while. If anyone is looking for any of my Ep's, keep an eye on the classifieds because I will be selling through here.

[David Niven (David Niven)]

Hi Jas,
My eps are $200 and less.
82D afov is my sweet spot and IMHO is more than sufficient.
So, I am not chasing after 100D or the exotic glasses!
Simplicity is the way to go and you can certainly enjoy the night sky without having to spend a fortune.

[Renato1 (Renato)]

My suggestion is don't buy another TV Barlow (I own two) instead get a TV Powermate. When looking at an image, in the back of my mind I always "know" when I'm using a Barlow, but that isn't the case with a Powermate.

I have astigmatism, so most low power eyepieces I can't really assess well. But even to my lousy eyesight I notice that the stars seem to be sharper and the contrast better in the more expensive eyepieces - much nicer - though in actual usage it doesn't make that much practical difference to me.

With higher power eyepieces where astigmatism isn't a problem, a lot depended on my telescope. I recollect buying what was supposed to be a really good orthoscopic eyepiece and not seeing any real difference compared to my standard plossl in my then C8 and 80mm ED refractor. I scratched my head about it, and then tried barlowing my little refractor up to 200X and looking at Jupiter. And sure enough, at the extreme high power for the refractor, the orthoscopic was showing somewhat more detail than the plossl (I could see a shadow transit easily with the orthoscopic, which was much sharper and better defined than in the Plossl).

Anyhow, that's my perspective, but I know that people with better vision see things differently.
Regards,
Renato

[Camelopardalis (Dunk)]

I'd say that if you're not craving the wider AFOV, don't buy an Ethos...as you won't appreciate the crater it'll leave in your wallet.

[Profiler (Profiler)]

Painfully expensive but I would have to say that the 13mm Ethos is the only eyepiece I have ever purchased which really did hit me with a 'WOW' experience when I looked through it.

From what I understand sales of all other Ethos fls combined equate to the number of 13mm alone which are sold

[JJDOBBER79 (Jas)]

Hi Profiler,
All the rest of my gear is 1.25" and I think the 17ethos is 2" so 13 would probably be as low power as I would want to go

[astro744]

Originally Posted by JJDOBBER79

Hi Profiler,
All the rest of my gear is 1.25" and I think the 17ethos is 2" so 13 would probably be as low power as I would want to go

Are you sure? The 13mm Ethos will give you a true field of only 0.85 degrees.

Using 1500mm focal length and field stop diameter in mm from Tele Vue here are some more examples. TFOV=FSDx57.3/FL

FL=Focal Length of Telescope
AFOV=Apparent Field of View
FSD=Field Stop Diameter
TFOV=True Field of View
EPD=Exit Pupil Diameter

32mm Plossl, AFOV=50deg, FSD=27mm, TFOV=1.03deg, EPD=6.4mm
24mm Panoptic, AFOV=68deg, FSD=27mm, TFOV=1.03deg, EPD=4.8mm
31mm T5 Nagler, AFOV=82deg, FSD=42mm, TFOV=1.60deg, EPD=6.2mm
26mm T5 Nagler, AFOV=82deg, FSD=35mm, TFOV=1.34deg, EPD=5.2mm
20mm T5 Nagler, AFOV=82deg, FSD=27.4mm, TFOV=1.05deg, EPD=4mm
16mm T5 Nagler, AFOV=82deg, FSD=22.1mm, TFOV=0.84deg, EPD=3.2mm
21mm Ethos, AFOV=100deg, FSD=36.2mm, TFOV=1.38deg, EPD=4.2mm
13mm Ethos, AFOV=100deg, FSD=22.3mm, TFOV=0.85deg, EPD=2.6mm

I suggest you create a spread sheet using data from the following table http://www.televue.com/engine/TV3b_p...4#.U0csPmcRC9I

Note the same FSD gives the same TFOV. Note also if you have a different brand eyepiece and do not have FSD then you can use TFOV=AFOV/Magnification. The result is very close and any difference is due to distortion effects within the eyepiece. See http://www.televue.com/engine/TV3b_p...3#.U0czJWcRC9I

See also http://www.televue.com/engine/TV3b_p...9#.U0cyzWcRC9I

There are many ways to select a series of eyepieces and magnification spread is only one. However when there are different AFOV you could end up having the same TFOV. TFOV spread is another method and yet another is exit pupil spread giving say 6mm, 4mm, 2mm, 0.5mm (maybe 3mm & 0.7m) exit pupils.

I personally like observing with the same AFOV since TFOV and magnification spreads then correlate. (Of course this is not critical).

The actual magnification, TFOV & exit pupil depend a lot on what you a looking at. See also this article http://www.televue.com/engine/TV3b_p...4#.U0czT2cRC9I Yes it is promoting Ethos but there is a lot of useful info there. Also refer Para beginning "The 1991 article ..."

On the issue of exit pupil, if you are young you can easily accommodate 7mm or more and provided the sky is dark enough you will get a spectacular view. A 41mm Panoptic with your telescope will give you the maximum TFOV of 1.76 degrees at the expense of a large exit pupil.

41mm Panoptic, AFOV=68deg, FSD=46mm, TFOV=1.76deg, EPD=8.2mm
35mm Panoptic, AFOV=68deg, FSD=38.7mm, TFOV=1.48deg, EPD=7mm

The 35mm Panoptic is a very good alternative to the 41mm being lighter and giving slightly less exit pupil.

Note if your purpose is to have as a large TFOV for easier star hopping then a large exit pupil does not matter. The amount of contrast you have will depend a lot on you location and sky conditions but under a dark sky a 41mm Panoptic will still give a very good view. If your eye cannot accommodate 8.2mm exit pupil (and only the young can barely) it just means you're not using all of your mirror diameter but if you're only finding stuff it really doesn't matter.

The 13mm Ethos is a nice choice and if you like it you may end up complementing it one day with a 21mm Ethos.

[JJDOBBER79 (Jas)]

wow, information overload. That's a lot to take in. I basically just want to hold 1 premium EP and rotate it a bit to allow me to try a few. 41 pan is on the list with a 31mm, type 6 nagler, I would also like to try a docter 12.5, dont like my chances of getting a used one of those for around $600. Probably more like $800. Thank you for the analysis astro, this will come in handy when assessing potential purchases.

[casstony]

I'd recommend you take the 31 Nagler off the list since it's mainly a finder eyepiece in your scope - better to spend your money on a primary observing eyepiece around 13 to 17mm. An ES 30mm 82 degree will serve just as well as the 31 Nagler.

IMO the 41 Pan is wasted in an f/5 scope due to the exit pupil being too large.

[Camelopardalis (Dunk)]

Surprised you would sell your 10XW as that's one of (if not) the best eyepieces in that focal length. Great throughput, easy to use and pin sharp to the edge. The Ethos will only give you a wider FOV from there, the image isn't otherwise any different. If you're looking for a slap around the face experience from an eyepiece, you're expectations are probably too high from what you have now. The immersive experience from a Nagler or Ethos shouldn't be underestimated though, it just comes at quite a cost.

I'd be checking your telescope optics are in good condition and well collimated, as on a good clear night the XW range are excellent, as are the Delos and Ethos.

[MattT]

The first thing I would buy is a Coma Corrector. I have an ES one that is as good as a TV Paracorr type 1 I had. No point in buying a 100º eyepiece if half the field is a mess. The ES 68º eyepieces all work beautifully in my 10" Newt with the ES CC. Nothing wrong with buying and selling eyepieces but I have to spend about a year with an eyepiece before I decide if I like it or not.
For the wow view your after....binoviewing....my suggestion, doesn't have to be expensive either!
Matt

[Kunama]

Originally Posted by MattT

.........
For the wow view your after....binoviewing....my suggestion, doesn't have to be expensive either!
Matt

+1
The WOW factor between various eyepiece brands was nothing compared to putting a pair of them side by side.
Eye fatigue is a thing of the past, my first foray was not successful but now I think I have the eyepieces that suit me well.
I wish I had kept the RKE28s