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Binary/Double/Variable Stars Eyepieces

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#1 SeptemberEquinox

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Posted 23 March 2013 - 09:28 AM

I have been obsessed in observing double/binary/variable stars. I think, it all started after reading Jon Issacs comment on how much he loves observing double stars. Then I thought, what's so special about double stars? So not expecting too much, I guided my scope to Star Castor with 25mm and thought 'uh i see one star, boring'. Then I popped in my 6.7mm, AMAZING!!! I saw two!! That was the moment when everything changed, my favorite objects to observe were not messier objects anymore. Thank you Jon :)

So I am looking for a good eyepiece with bang for your buck deal. I guess off axis and Wide FOV aren't too important. What would you guys recommend? Which eyepiece do you use to observe binary/double/variable stars?

#2 azure1961p

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Posted 23 March 2013 - 10:17 AM

The the wider angle the better for contrast. More glass is not a detracting element.
Pete

#3 Dan Williams

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Posted 23 March 2013 - 11:14 AM

Think planetary, and you will be fine. Plus there are many more reviews for planetary than binary.

~ Dan

#4 Dan Williams

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Posted 23 March 2013 - 11:27 AM

The cleanest views I've gotten were with the TMB supermonos. However, the 2-4 Nagler zoom was about it's equal when I had to barlow the supermonos. The best color I have ever seen on Izar (Epsilon Bootes) was with Meade series 3000 plossls. Televue plossls, UO orthos and Konigs are also very nice.

~ Dan

#5 CelestronDaddy

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Posted 23 March 2013 - 12:10 PM

I'd really like to get one of the ES 6.7mm 82* or something similar to that. I've missed one or two of these in the classifieds. I've got a very inexpensive Astro-Tech 6mm Plossl that is actually not a bad EP especially considering the low cost but I'd still like one of the 6.7mm :jump:

#6 mgwhittle

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Posted 23 March 2013 - 12:36 PM

If you are interested in seeing the colors of double stars, I can not recommend ES eyepieces. In my experience, they do not transmit the color of stars very well compared with other options. Other than that they are excellent eyepieces for the money.

If as you say FOV is not important, check out the Sterling Plossls (or the Astro Tech version)....very inexpensive and they render star colors very vividly. If you want to pay just a bit more and get a bigger FOV and better eye relief then the Astro Tech Paradigms in the shorter focal lengths are excellent all around. They are excellent for double star and planetary work. Both of those options are cheaper than the ES options and are in stock right now.

#7 hottr6

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Posted 23 March 2013 - 02:52 PM

Doubles require definition and contrast (think short hi-po eyepieces with few elements) and variable stars require wiiiiide fields. Two completely different missions.

#8 azure1961p

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Posted 23 March 2013 - 10:01 PM

I think if you went with Televue or Sterling plossls you'd be first rate front row. Nice simple four element ocular does many things well and something's the best. Variable stars for magnitude comparisons are easier in wide field. These days people swear by heavy multi element t wide angle oculars but it isn't needed if you don't seek a super wide field.

Pete

#9 Jeff Morgan

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Posted 23 March 2013 - 10:52 PM

I have been obsessed in observing double/binary/variable stars. I think, it all started after reading Jon Issacs comment on how much he loves observing double stars. Then I thought, what's so special about double stars? So not expecting too much, I guided my scope to Star Castor with 25mm and thought 'uh i see one star, boring'. Then I popped in my 6.7mm, AMAZING!!! I saw two!! That was the moment when everything changed, my favorite objects to observe were not messier objects anymore. Thank you Jon :)

So I am looking for a good eyepiece with bang for your buck deal. I guess off axis and Wide FOV aren't too important. What would you guys recommend? Which eyepiece do you use to observe binary/double/variable stars?


AFOV is not at all important. Not even minimally so. You're after clarity now, ditch the wide fields. Even if they are "just as good" (which they are not), they cost more.

Lots of opinions, but I think you'll find most center around Brandons, Orthos, and Plossls.

One of the nice things about four element eyepieces (compared to the wide fields) is that experimentation doesn't break the bank. The limiting factor in comparisons is available observing time and lack of truly outstanding seeing nights.

#10 CelestronDaddy

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Posted 23 March 2013 - 11:14 PM

Which line of the Astro-Tech plossls is the equivalent to the Sterling plossls?

#11 7331Peg

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Posted 24 March 2013 - 12:27 AM

The Astro-Tech High Grade Plössls are the Sterling equivalents: ----> HERE

I'll echo other comments on the Astro-Tech/Sterling and Televue Plössls for double star work. Orthos work well, too, but I've actually found the Astro-Tech/Sterling do a noticeably better job of controlling light scatter, which you'll find handy when you have the magnification cranked up to 500x in search of a faint companion half an arc second from the primary. :grin:


John :refractor:

#12 buddyjesus

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Posted 24 March 2013 - 12:34 AM

if you plan on measuring the double stars, a celestron 12.5mm orthoscopic reticle eyepiece is discontinued but still the gold standard for position angle measurement and not so bad at separations. Barlows to get different magnifications would help this out too.

If all you are looking for is a good show, plossls or orthos should do you fine. I think it is nice to have diverse magnifications to see how low you can go with magnification and get a split. It helps the colors come out.

#13 hottr6

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Posted 24 March 2013 - 08:07 AM

AFOV is not at all important. Not even minimally so. You're after clarity now, ditch the wide fields. Even if they are "just as good" (which they are not), they cost more.

That is true for looking at doubles, but is wrong for observing variables which the OP mentions. AFOV is extremely important for variable star observing. Many times the comparison stars can be many minutes, even degrees distant from the variable and you need wide fields to see both variable and comparison stars in the same field. Make sure vignetting will not be a problem if using stars at the edge of the field.

The extra glass in wide fields do not impact magnitude estimation. Accurate magnitude estimation is best done at least a couple of magnitudes or more brighter than the limiting magnitude of the telescope.

#14 CelestronDaddy

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Posted 24 March 2013 - 08:36 AM

John - Thanks! I already have the 6mm plossl so I'll look at some others maybe... Thanks again... Tony

#15 Jeff Morgan

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Posted 24 March 2013 - 09:30 PM


AFOV is not at all important. Not even minimally so. You're after clarity now, ditch the wide fields. Even if they are "just as good" (which they are not), they cost more.

That is true for looking at doubles, but is wrong for observing variables which the OP mentions. AFOV is extremely important for variable star observing. Many times the comparison stars can be many minutes, even degrees distant from the variable and you need wide fields to see both variable and comparison stars in the same field. Make sure vignetting will not be a problem if using stars at the edge of the field.

The extra glass in wide fields do not impact magnitude estimation. Accurate magnitude estimation is best done at least a couple of magnitudes or more brighter than the limiting magnitude of the telescope.


The AAVSO recommends a single low power widefield eyepiece (that is to say, large true field) for the function you mention, they seem rather agnostic on apparent field of view issue.

In any event, eyepiece ownership is not an either/or proposition until one fills up his eyepiece case. Then you buy a second case.

#16 jrbarnett

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Posted 24 March 2013 - 10:08 PM

My favorite double star eyepieces are the Pentax SMC Orthos.

They do a really decent job *not* diluting star colors. Perhaps it has to do with some combination of their glasses and coatings, or maybe their baffling, but in any case at a given focal length in a given telescope, no eyepieces beat the SMC Orthos for color saturation on stars.

- Jim

#17 SeptemberEquinox

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Posted 24 March 2013 - 11:29 PM

Thank you for all your helpful replies. I do have a sterling plossl from astrotech. It performs ok, it does better job in splitting doubles than ES 6.7mm. But contrast and sharpness aren't that great. I guess I need to spend bit more money on better plossls or Orthos.

Is Pentax XO their Orthos?

Most or ALL of the Good Orthos and good Plossls have been discontinued. I'm not sure why bigger manufactures aren't copying these designs. It seems like University Optics Orthos were one of the most popular, and Baader Orthos, both in HD designs.

Takahashi LE 5mm, is that a plossl design? It looks promising. But of course, I can't find it anywhere.

If anyone is selling or not using their good 5mm Plossl, or Ortho Eyepiece. Please PM me, I'm so fascinated with binary stars, I will take very good care of that ONE eyepiece.

What is the maximum magnification you use for binary and variables?

#18 jrbarnett

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Posted 26 March 2013 - 10:57 PM

Hiya.

False color increases in an achromat with magnification. At a certain point, you'll hit a wall of diminishing returns where the extra false color generated by the increased magnification will reduce contrast to a degree that exceeds the benefits of the larger image scale.

Some may disagree, but I suspect that you could improve your double star satisfaction by either sticking with less tight doubles suitable for splitting at lower, more color free magnifications or stopping down your scope with an aperture mask to quell false color and allow use of higher magnification (though this will also reduce ultimate resolving power, so it's a balancing act). An aperture mask would be something like a lid or extra lens cap that covers you objective and has a hole cut out of the center of a smaller aperture than the objective. Stopping your 150mm down to 100mm the focal ration becomes f/7.5 and it will have a lot less false color than 150mm at f/5. Dropping down to 80mm, the focal ratio becomes f/9.3 and will offer even better false color control.

At full aperture (150mm at f/5) I'd stick with wide, colorful doubles and not worry about pushing the magnification.

Good luck!

- Jim

#19 Dan Williams

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Posted 27 March 2013 - 12:49 PM

I once had a fantastic double star image in a 5" f/15 telescope with a modified ortho eyepiece. I took the field lens out of the ortho (I don't remember if I inverted the eye lens) for a 1 element 1 group combination. Extremely crisp view - drinking straw view of usable field? Nope, coffee stirring straw view. Did it once, may try again someday.

~ Dan

#20 Cotts

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Posted 27 March 2013 - 06:49 PM


AFOV is not at all important. Not even minimally so. You're after clarity now, ditch the wide fields.


Allow me to take a contrary 'view', as it were.... I am a dedicated double star observer and I use 17mm Ethos, 13mmEthos, 8mm Ethos, 5mm Nagler and a 6-3mm Nagler zoom with both the 16" Dob and the 8" Mak. I truly enjoy the sense of space given by the 100 and 82 degree eyepieces. I see a delicate little Struve pair, perhaps 7 and 8 mag, at 2.5" separation floating in space, in context, surrounded by other little stars, as if I were approaching the system in a space ship.

With regard to contrast and definition, I have used the Ethos' and the 5mm Nagler many times to take my scopes to Dawes' limit and beyond to clearly see the 'peanut', 'notched pair' and 'elongated oval' of really tight doubles. I have used orthos and other simpler designs and they are no better (and no worse, either) at revealing these not-quite-resolved pairs.

The monocentrics and other narrow field designs really show their stuff on planets but in my experience they are not needed for observing close double stars and using them ruins the aesthetic experience.

Dave

#21 Dan Williams

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Posted 30 March 2013 - 09:25 AM


I never thought about Dave's "contrary view". I'm going to have to experiment now! I will barlow my 82 degree 4.8mm eyepiece and compare to my 45 degree 2.5mm ortho. A spaceship view sounds like my childhood fantasies.

~ Dan

#22 RAKing

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Posted 30 March 2013 - 12:29 PM

I agree with Dave. I use "regular" wide field eyepieces for most of my doubles and only pop in the high magnification if it's really needed. I get a real kick out of seeing a "Small White Twin", such as Alrakis (Mu draconis) with its two tiny white dots in a humongous black sky. :)

For a tough triple like Zeta Cancri, I'll use the orthos and crank up the magnification.

Is the OP planning to estimate variables or just look at the cool colors? For estimating, you should get the widest field eyepiece you can afford that gives you the best view. As mentioned earlier, the object is to get the comparison stars in the same field if possible. This makes it easier to do an accuarate estimate. For my 140mm refractor, I use a 21mm Ethos and for my 8 inch Mak, I prefer the 40mm Pentax XW. I only boost the magnification if the variable is close to my seeing limit.

Cheers,

Ron






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