Author Topic: New Eyepieces  (Read 920 times)

Nicholas Becker

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Re: New Eyepieces
« Reply #15 on: January 20, 2018, 08:28:00 PM »
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Quote

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<p class="citation">QuoteAn 8" f/6 or 10 F/5 "Dobsonian" would have similar focal-lengths, at 1200mm and 1250mm, respectively.

The difference being that a 5.5mm eyepiece being used in an f/6 Dob would produce a more reasonable exit pupil of 0.9mm and in an f/5 Dob an exit pupil of 1.1mm. In an f/13 scope, the exit pupil would be 0.4mm.

A 1mm exit pupil gives you maximum planetary detail and is excellent for splitting binary stars. A 0.5mm exit pupil is useful for splitting close double stars, but only during very good seeing.

https://www.astronom...t-pupils_t.aspx

Dave Mitsky
I have to admit that I didn't realize the significance of exit pupil diameter at the time of purchase, but it certainly explains why my 12mm Dual HD is, roughly speaking, the shortest focal length EP I use for the majority of my planetary and DS work with my f/10 SCT. (exit pupil dia. = 1.2mm) I've ordered a Lunt 60mm, f/8 solar telescope, for which I will want some shorter EPs, but for the SCT the 12mm does best under typical (poor to marginal) seeing conditions. Fighting the urge to "power up" has been tough, but experience is the best teacher.
I have only done solar observing a few times through a black polymer filter. I was using an 120mm refractor with an 80 mm aperture mask. bringing me to f/12.5. I could only push that scope to up to about 100x before image breakdown. I think it
has something to do with the column of air in the direct path of the sun as being extreemly turbulent.  So you may not need
that short eyepiece with your lunt scope.

Marquise Nation

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Re: New Eyepieces
« Reply #16 on: January 20, 2018, 10:23:42 PM »
Quote
<p class="citation">QuoteAn 8" f/6 or 10 F/5 "Dobsonian" would have similar focal-lengths, at 1200mm and 1250mm, respectively.

The difference being that a 5.5mm eyepiece being used in an f/6 Dob would produce a more reasonable exit pupil of 0.9mm and in an f/5 Dob an exit pupil of 1.1mm. In an f/13 scope, the exit pupil would be 0.4mm.

A 1mm exit pupil gives you maximum planetary detail and is excellent for splitting binary stars. A 0.5mm exit pupil is useful for splitting close double stars, but only during very good seeing.

https://www.astronom...t-pupils_t.aspx

Dave Mitsky[/quote]

Through my short time planetary observing I think this is a good rule of thumb. I usually go just a little bit higher. but about .75 is where I draw the line. Maybe the slightly higher power is due to some subjective/cognitive desire for a little larger image. Maybe my brain works best with a bigger and a little less detailed image? Do older eyes respond differently to small e.p's?

I see people here posting up huge mag numbers and I can't figure out how they are doing that unless they have truly giant
scopes and perfect air. I read a paper on line that says at roughly sea level 200x is all the atmosphere is going to
give you.

When viewing mars for example right now I can't see much detail, so I use the plane'ts edge. If the edge is nice and clean
I know I can push up the power a bit. Once the edge starts getting "furry" , I know I'm getting close to the max mag.
Once I'm at this point, I sit and wait for detail to "appear" when the air cooperates.  In my 120mm f/8 I find my highest mag view
is usually with a 6mm ortho. That is about 167x with an exit pupil of .72mm

James Bagby

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Re: New Eyepieces
« Reply #17 on: January 21, 2018, 04:48:51 AM »
Quote
Quote
<p class="citation">QuoteAn 8" f/6 or 10 F/5 "Dobsonian" would have similar focal-lengths, at 1200mm and 1250mm, respectively.

The difference being that a 5.5mm eyepiece being used in an f/6 Dob would produce a more reasonable exit pupil of 0.9mm and in an f/5 Dob an exit pupil of 1.1mm. In an f/13 scope, the exit pupil would be 0.4mm.

A 1mm exit pupil gives you maximum planetary detail and is excellent for splitting binary stars. A 0.5mm exit pupil is useful for splitting close double stars, but only during very good seeing.

https://www.astronom...t-pupils_t.aspx

Dave Mitsky
I have to admit that I didn't realize the significance of exit pupil diameter at the time of purchase, but it certainly explains why my 12mm Dual HD is, roughly speaking, the shortest focal length EP I use for the majority of my planetary and DS work with my f/10 SCT. (exit pupil dia. = 1.2mm) I've ordered a Lunt 60mm, f/8 solar telescope, for which I will want some shorter EPs, but for the SCT the 12mm does best under typical (poor to marginal) seeing conditions. Fighting the urge to "power up" has been tough, but experience is the best teacher. [/quote]
I have only done solar observing a few times through a black polymer filter. I was using an 120mm refractor with an 80 mm aperture mask. bringing me to f/12.5. I could only push that scope to up to about 100x before image breakdown. I think it
has something to do with the column of air in the direct path of the sun as being extreemly turbulent.  So you may not need
that short eyepiece with your lunt scope.[/quote]
To this point all my solar observing and photography has also been through a Thousand Oaks film filter. I've used my 12mm EP with reasonable success, considering the atmospheric heating, but then I typically view the sun around noon, minimizing the thickness of atmosphere through which I'm viewing. But I prefer my 25mm lens or even my 40mm Plossl, probably for the same reason you cite above. What I don't know is whether the atmospheric turbulence will affect viewing as significantly when filtering out all but the 656.3nm (+/-) band.
Sorry, I think I'm getting pretty far off topic here.

calbeyrefrows

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Re: New Eyepieces
« Reply #18 on: January 23, 2018, 12:03:59 AM »
Quote
Through my short time planetary observing I think this is a good rule of thumb. I usually go just a little bit higher. but about .75 is where I draw the line. Maybe the slightly higher power is due to some subjective/cognitive desire for a little larger image. Maybe my brain works best with a bigger and a little less detailed image? Do older eyes respond differently to small e.p's?
Indeed they do. Crystalline lens opacification, vitreous floaters, normal aging loss of foveal photoreceptor cells all conspire to reduce clarity, resolution, and increase diffractive light scatter. Those 25 year olds most definitely see better than we do.

kahrorisupp

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Re: New Eyepieces
« Reply #19 on: January 23, 2018, 10:14:49 AM »
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I am in the same boat when it comes to eye pieces,

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Welcome to CN, Stargazer.

I'm relatively new myself, and thanks to the advice of more experienced CN members I ended up purchasing several Astro-Tech Paradigm Dual ED EPs, a 12, 18, and 25. The telescope came with a decent 40mm Plossl. The Dual EDs are bargains--I've compared them with premium-priced EPs (on my telescope) and I find it difficult to see a significant difference. With a fast refractor, the differences might be slightly more apparent, but then the price I paid per EP is roughly 1/5 the cost of a Type 6 Nagler. My Nagler-owning friend was truly impressed with the Dual EDs himself. They have good eye relief and decent field of view, which is something Plossls, especially those in shorter focal lengths, lack. I have a Baader 2.25x Barlow, and it's fine, but seldom used.

The Astro-Tech Paradigm Dual EDs are available from Astronomics, but they are also available from Agena under the name of Starguider Dual ED--same EP, same price.  For someone just getting into astronomy the Dual EDs are tough to beat. 

Thanks for the advice! I'm i in need of some eye pieces at an affordable cost since I'm looking at a kit of eyepieces, I'm looking at The Astro-Tech Dual ED / Agena, and the Meade Series 5000 1.25" HD-60 Eyepieces

Rasheed Grayson

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Re: New Eyepieces
« Reply #20 on: January 23, 2018, 03:42:40 PM »
Wow, thank you everyone for the replies. I'll admit, I got lost toward the end, but there was some really great information there.

I appreciate someone bringing up exit pupil, it is a term I had not heard before and definitely something to consider when selecting eyepieces.

As for budget, I don't really have one. I would like to buy something that will last as my experience grows. So, I would prefer to spend a little more upfront to get something that will be satisfying to use for years. I was considering around $150 for one eyepiece, maybe more if it makes a big difference in quality.

I picked the brands I did based on several hours of google searching. Those brands seem to be preferred for quality.

Thanks again for the help. Telescopes can be a little overwhelming, but it's nice to know there are passionate individuals out there willing to help a newbie.

ermaudyvi

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Re: New Eyepieces
« Reply #21 on: January 25, 2018, 06:36:35 PM »
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At f/13, almost any brand of 32mm Plössl should perform well.

You may want to consider one of the Celestron X-Cel LX, Meade Series 5000 HD-60, Astro-TechParadigm Dual ED, orAgena Starguider Dual ED eyepieces for planetary observing. The first two lines are similar to each other, as are the third and fourth.

https://www.astronom...pieces_c62.aspx

https://www.astronom...pieces_c73.aspx

https://www.astronom...pieces_c52.aspx

A 6mm eyepiece will produce an exit pupil of less than 0.5mm in your telescope. You may want to get a 7 or 8mm instead.

Dave Mitsky

I have a 90mm Mak and the highest power eyepiece I use in it is a 9mm for 150x. That's about as high as I go with that scope om most nights of really good seeing. Otherwise I back off to a 12mm EP.

chlorleifilwhirl

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Re: New Eyepieces
« Reply #22 on: January 31, 2018, 09:15:17 AM »
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As for budget, I don't really have one. I would like to buy something that will last as my experience grows. So, I would prefer to spend a little more upfront to get something that will be satisfying to use for years. I was considering around $150 for one eyepiece, maybe more if it makes a big difference in quality.

It does. If you ever get the chance to view some DS objects through a quality 130mm apochromatic refractor with a 2" TV Ethos, the quality will be apparent. But most of us don't allot $600+ for an EP, especially when starting out. Televue makes great products, and some of the best EPs money can buy (and they are currently on sale), but don't let the respect TV commands break the bank, especially when so many other fine EPs are available for a fraction of the price. When you've accumulated many years of viewing, you may want to upgrade, and there will always be a viable market for your less expensive equipment. But I'm guessing that you probably would want to keep your better, but less-costly, starter EPs even then. I can't imagine getting rid of my AT Paradigm Dual-EDs--they are simply great EPs, cost notwithstanding. So are many other brands and designs at less than TeleVue prices.

Cory Bass

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Re: New Eyepieces
« Reply #23 on: January 31, 2018, 10:14:55 AM »
I get what you're saying, but i'm not talking about $600 dollar eyepieces.

The original eyepieces I was looking at was a 32mm TV Plossl, which is only $125 and the Baader ortho 6mm, which is only $87. Although, based on the conversations above, the 6mm won't work well based on the exit pupil.

The AT Paradigm Dual ED, are only $60. So it's not that much cheaper than the ones I was looking at. So my fear is, I pay $60 for an eyepiece and later kick myself for not just spending a little more and buying a better one.

Not that I'm saying the AT Paradigm Dual ED is so inferior to the others, because frankly, I don't know. I'm just using that as an example.

Jason Harlan

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Re: New Eyepieces
« Reply #24 on: January 31, 2018, 01:47:48 PM »
+1 for the Explore Scientific 82 or 100 degree EPs. I looked through several of these, as well as many TeleVue EPs before finally deciding on the ES 82 degrees. I'm saving up to hopefully get one of the 100 degree EPs they make too. Wonderful pieces at only a fraction of the cost of TV, and I personally couldn't see a difference.

If you do decide to go with ES, they go on sale quite frequently if you're willing to wait a bit.

consurflola

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Re: New Eyepieces
« Reply #25 on: January 31, 2018, 02:00:11 PM »
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I get what you're saying, but i'm not talking about $600 dollar eyepieces.

The original eyepieces I was looking at was a 32mm TV Plossl, which is only $125 and the Baader ortho 6mm, which is only $87. Although, based on the conversations above, the 6mm won't work well based on the exit pupil.

The AT Paradigm Dual ED, are only $60. So it's not that much cheaper than the ones I was looking at. So my fear is, I pay $60 for an eyepiece and later kick myself for not just spending a little more and buying a better one.

Not that I'm saying the AT Paradigm Dual ED is so inferior to the others, because frankly, I don't know. I'm just using that as an example.


The comparison I made earlier, Stargazer, was between an Astro-Tech Paradigm Dual ED at $60 and a Type 6 Nagler at over $300. Both the Nagler owner and I found virtually no apparent difference when used with my telescope, which is similar to yours, if somewhat larger in aperture. Both OTAs are relatively slow (f/10 or slower) with longer focal lengths, and the two EPs, one costing 5x the other, were very, very close in resolution. Even peripheral stars in both appeared roughly the same, but some of that credit must go to my particular OTA, which is optimized for that.

Mostly what you pay more for is wider field. That is not a huge consideration with a smaller Mak, like yours, but perhaps more so with a Dob which must be moved frequently to stay with planets and DS objects. A wider field allows longer viewing periods before moving the scope.

Some people equate price with quality, and that often is the case. But I think you'll be impressed with the quality and the optics of under-$100 EPs such as the Dual EDs. You'll also appreciate the greater eye relief in shorter focal lengths compared with Plossls of the same length. But if you feel more confident in spending more, by all means do so. You'll be happier, and it helps the industry.

Justin Prasad

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Re: New Eyepieces
« Reply #26 on: February 02, 2018, 06:16:16 PM »
Quote
Wow, thank you everyone for the replies. I'll admit, I got lost toward the end, but there was some really great information there.

I appreciate someone bringing up exit pupil, it is a term I had not heard before and definitely something to consider when selecting eyepieces.

As for budget, I don't really have one. I would like to buy something that will last as my experience grows. So, I would prefer to spend a little more upfront to get something that will be satisfying to use for years. I was considering around $150 for one eyepiece, maybe more if it makes a big difference in quality.

I picked the brands I did based on several hours of google searching. Those brands seem to be preferred for quality.

Thanks again for the help. Telescopes can be a little overwhelming, but it's nice to know there are passionate individuals out there willing to help a newbie.


So I have a spread of entry to mid-range eyepieces. Clearly I am no authority on the subject. Others here know a lot more than I do.

Of all the eyepieces I have I think the Explore Scientific 82 degree is about the best. If I had known then what I know now I would have purchased a couple more while they were on sale. And I have heard similar praise for the 68 degree eyepieces.

http://agenaastro.co...scientific.html

If you are looking for a set of eyepieces in this price range you could probably pick these and be very happy with them for a long long time. And they should serve you well in your future scopes.

Christopher Mendez

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Re: New Eyepieces
« Reply #27 on: February 03, 2018, 03:23:06 AM »
Quote
Quote

At f/13, almost any brand of 32mm Plössl should perform well.

You may want to consider one of the Celestron X-Cel LX, Meade Series 5000 HD-60, Astro-TechParadigm Dual ED, orAgena Starguider Dual ED eyepieces for planetary observing. The first two lines are similar to each other, as are the third and fourth.

https://www.astronom...pieces_c62.aspx

https://www.astronom...pieces_c73.aspx

https://www.astronom...pieces_c52.aspx

A 6mm eyepiece will produce an exit pupil of less than 0.5mm in your telescope. You may want to get a 7 or 8mm instead.

Dave Mitsky

I have a 90mm Mak and the highest power eyepiece I use in it is a 9mm for 150x. That's about as high as I go with that scope om most nights of really good seeing. Otherwise I back off to a 12mm EP.

It's true that small apertures "run out of light" fairly quickly as magnification is increased.

When one drops below an exit pupil of 1mm there are a number of issues such as floaters to take into consideration. With many of the telescopes that I own or use, I rarely use even a 1mm exit pupil for planetary observing. For example, the 17" f/15 classical Cassegrain at the Naylor Observatory produces a magnification of 432x at a 1mm exit pupil. I usually use 259x and sometimes 324x with that telescope when the seeing is good.

An f/13 Maksutov-Cassegrain reaches a 1mm exit pupil with a 13mm eyepiece. However, some observers use exit pupils around 0.5mm for resolving very close binary stars. Whether having an eyepiece that produces that magnification/exit pupil is worthwhile when another with a longer focal length would be more useful in general is something to consider.

Dave Mitsky

closfockralperp

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Re: New Eyepieces
« Reply #28 on: February 08, 2018, 08:12:33 PM »
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Interestingly, and perhaps wildly-optimistic to boot, Celestron states "15x" as the "Lowest Useful Magnification" to somehow realise with its 4" f/13 Maksutov...

That would require an 88mm ocular, and with a 6.8mm exit-pupil; not impossible however, as I've read of someone having made a 100mm even.

I'm not sure about a mak scope, but if you use too long of a focal length in newt, you can get "ghosting" of the secondary
in the eyepiece. I have an 6" f/5 newt and some eyepieces 40mm and over had this issue. I'm not sure if it has to do with
the huge exit pupil or what?

This 2" 60° 50mm ocular would produce a 10mm exit-pupil with a 6" f/5...

http://agenaastro.co...w-eyepiece.html

Perhaps up to 40% or more of the light gathered would be wasted, falling upon the iris instead. In the case of a Newtonian, the secondary would be evident there in the eyepiece, especially during the day. I have a 6" f/5 Newtonian, and during the day, even with a 25mm, I saw this...

...the secondary's shadow. The camera didn't capture the shadow in the very first image; odd, but in every subsequent shot it did.

The longer focal-lengths above 32mm benefit those with long-focus telescopes; Schmidts, Maksutovs, and the like. I use a 30mm, maximum, with my 6" f/5.

I do know that ghosting can be due to reflections of some sort, and with either an eyepiece's or telescope's interior that's not blackened properly. I recently flocked my 6" f/5, as I had experienced some ghosting.The desire to emulate a pair of 7x50 or 10x50 binoculars with a telescope is understandable, however telescopes are intended to observe objects closer; much closer. Last winter, I observed the Trapezium in Orion at over 200x with the 6" f/5; stunning.




acbanlota

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Re: New Eyepieces
« Reply #29 on: February 09, 2018, 07:10:10 AM »
A true field of view approaching a 10x50 binocular can be obtained with some rich-field telescopes. My 101mm f/5.4 Tele Vue refractor produces a TFOV of ~4.6 degrees at 18x with a 30mm 82 degree eyepiece and ~4.4 degrees at 15x with a 35mm 68 degree eyepiece. Being able to see M16, M17, and M18 in the same FOV is a lot of fun. I can use the same telescope at magnifications approaching 200x, although I rarely do.

One night a number of years ago, I observed M42 at over 600x through a friend's unique 20" f/10 classical Cassegrain. The results were quite interesting.

Dave Mitsky