Current Eyepieces
21mm Denkmeier (2)
14mm Televue Radian (2)
Previously Owned Eyepieces
35mm Televue Panoptic
32mm Univeristy Optics Konig 2″
32mm GTO Plossl (2)
25mm Orion Epic ED-2 (2)
25mm Sirrius Plossl (2)
24.5mm Siebert Ultra (2)
24mm Televue Panoptic (2)
18mm UO ortho (2)
16mm Nagler type 5 (2)
15mm Televue Panoptic (2)
14mm Meade Ultra Wide
13mm Nagler type 6 (2)
12.5mm UO Ortho (2)
11mm Televue plossl (2)
10mm Sirrius Plossl (2)
10mm Antares Ultima (2)
10.5mm Pentax XL (2)
9mm Orion Expanse (2)
9mm Antares HD Orthos (2)
9mm UO ortho (2)
9mm Nagler tpye 6 (2)
8mm Edmund RKE
7.4-22mm GTO Zoom (2)
7mm UO ortho (2)
2x Televue barlow
2x Orion Shorty barlow
3x Televue barlow
2x Televue Powermate
2.5x Televue Powermate
5x Televue Powermate
LIFE BEFORE BINOVIEWERS
My favorite eyepiece is the Pentax XL. I would own the entire line of the 1.25″ Pentax XL’s and never find myself wanting for more. They are the most comfortable eyepiece that I have ever used. They also happen to be very good optically. Very, very good. But, alas, I cannot use them in my binoviewers because they are too big for my eye spacing. Otherwise I’d have 2 of each one.
I have never had a large collection of premium eyepieces. I am a barlow/powermate kind of observer, as evidenced by my 4 magnifiers. All of them work extremely well. Although I have not done a side by side comparison, others have, and they assure me that the view using a high quality barlow or powermate is very close to or equal to a higher power eyepiece. I have found nothing in my viewing to refute this. If I find a focal length that I use a lot by barlowing, I’ll buy a single ep that fits in there.
Choosing an eyepiece for your new telescope
I have found eyepiece selection can be a very personal and subjective experience. Just go and post one of those ubiquitous “what is the best eyepiece” question on any of the groups, then standby for 100 different answers. This can be frustrating for rookies, as it was, and still is for me. The Nagler vs Meade UWA vs Radian vs Panoptic vs Pentax argument could rage on for weeks with no clear winner identified. Cloudy Nights has a good set of articles and reviews that you should read through before buying any more ep’s. This article in particular is a good read.
The best way to buy eyepieces is to try them first. Your local club can be a great source of try before you buy. Star parties are a good source as well, but I’ve found that strangers aren’t keen on loaning out their $300 oculars.
Another great source for all things astronomical is Astromart. I bought my Meade 14mm UWA for $200 off of Astromart (it retails for $300). It was in perfect condition. Used it for 6 months and it was a fantastic eyepiece. But a pair of them was just too huge for the binoviewers. So, I sold it for $200 on Astromart. I was out $8 for shipping. Not a bad price for renting a $300 eyepiece for 6 months. I bought my Pentax 10.5mm XL for $205, shipped. Sold it 5 months later for $210 ($5 to cover shipping), so that one was free. I had the use of 2 premium eyepieces that retail for over $500 and it cost me $8. In every transaction, the item I purchased was in great condition. That is key to the rental scheme. It must be in great shape when I buy it and then I keep it that way. Although this may not be for everyone, it has allowed me to try out many premium ep’s that I would otherwise not have been willing to buy. The key is to sell them if they are replaced. If you look through my ep table, you can see I’m not very good at that.
So, how does one choose the right focal length for a new eyepiece? Well, the best article I have read on the subject was written by Televue. In addition, Televue has recently added an articlespecifically for small dobs. For the XT10 (1200mm focal length), there are 3 sweet spots that should keep you going for a long time:
1. Max True Field Of View (TFOV) vs magnification
2. 100x
3. 200x
These 3 sweet spots are all that I need for a complete night of viewing. Is that all I have in my eyepiece case? No. If seeing is favorable, I am equipped to go all the way to ludicrous power on the Moon and planets, and I sometimes do. That’s where the barlows and powermates come in handy. But, don’t get sucked into the “I have a gap” syndrome. Just because you have nothing between 25mm and 14mm does not mean you have a gap.
What the heck does #1 mean? “Let me splain. No, is too much. Let me sum up.” Televue has a pretty good write-up here and here. I won’t begin to try to explain it all in my own words. But an example may help out. Let’s compare 3 eyepieces:
| EP 1 | EP 2 | EP 3 | |
| Focal Length | 32 mm | 24 mm | 20 mm |
| Apparent FOV | 50 deg | 68 deg | 82 deg |
| Field Stop | 27 mm | 27mm | 27.4 mm |
| True FOV in XT10 | 1.36 deg | 1.36 deg | 1.37 deg |
| Mag in XT10 | 38x | 50x | 60x |
Take a look at the TFOV vs magnification. All 3 ep’s provide a 1.36ish deg true FOV. But as you can see, it is at different magnifications. Who gives a hill of beans about that? Well, when magnification is increased, everything gets dimmer, that’s the nature of magnification. This makes the object you are looking at dimmer, but it also makes the background dimmer. This can be remarkable at lower powers, and not so important at high powers. Take a look at Andromeda (M31) or the Orion Nebula (M42) through each of the above ep’s in a moderately light polluted area. It will look much more distinct in EP 3 than the other two ep’s. Now, if you are lucky enough to always view from a dark site, then this may not be an issue. I am not that lucky, so I have EP 2 (24mm Panoptic). The catch is that EP 3 costs $440 (20mm Nagler type 5), EP 2 $280 (24 Panoptic) and EP 1 $110 or less (32mm Televue plossl). As a general rule, the higher the mag for a given field stop, the higher the price.
What would I buy for my new XT10? Well, that depends. Don’t you just love that answer? But it really does depend on a lot of things that vary from person to person (thus the personal nature of the decision). Here are some questions, the answers to which help determine which ep might be suitable for you:
1. What is your budget?
2. Telescope type, aperture and focal length
3. Will you be wearing eyeglasses while viewing?
4. What do you like to look at?
5. What are your current eyepieces?
6. What is your local seeing and light pollution like?
Here are some considerations for each point:
1. What is your budget?
There are ep’s out there from $25 to $750. You would think that the $750 eyepiece would be some uber ep that has a perfectly sharp, flat and color free 90 deg apparent field of view. Nope. It’s an orthoscopic design with a paltry 45 deg AFOV made by Carl Zeiss and no longer in production. But that’s what people are paying for one used off of Astromart. If you have a full set of these puppies sitting in your attic, you could sell them and afford to get on the waiting list for an Astro Physics APO. What do you get for all that hard earned cash? You get that last 2%, baby. The nirvana of optical perfection. So, we need to know your budget before we can recommend ep’s. Post something like this:
“I ordered an Orion XT10 from a local astronomy shop and I was wondering if some knowledgeable folks could recommend some quality eyepieces that would allow this dob to get the most out of DSO’s, planets, etc…”
And you won’t get many answers. Actually a good answer might be “buy all the Naglers, Panoptics, Radians and Pentax lines and pick the ones you like.” This may not be compatible with a lot of folk’s pocket books. Many folks bought the Guen Sheng and Synta dobs because they are frugal and I would expect as much when choosing an ep.
Premium ep’s seem to start at $200 or so and go up from there. The thing to consider is that ep’s can be used in any telescope. Buy a good one now and you’ll keep it even as you buy new telescopes (and you will, believe me).
2. Telescope type, aperture and focal length
This information is useful because it helps determine several things. First, what focal length ep might be useful. A 3mm ep might not be very useful in an XT10 (400x) but it would be a great ep for the Televue NP101 (180x). The type of focuser will help determine whether you can use 2″ ep’s. Also, balance might be an issue. Throw a 31 Nagler on an XT8 and watch it take a nose dive. Aperture size helps determine what the maximum useful magnification is for your telescope. 50x per inch is an oft quoted limit, but this is not an absolute. My XT 4.5 (4.5″ dob) does not like anything above 180x and it’s really sweet spot is about 160x. Folks who own a scope similar to yours will be able to share this kind of experience with you and help determine a good ep. So, share your equipment type when asking for advise.
3. Will you be wearing eyeglasses while viewing?
Folks who wear eyeglasses generally prefer eyepieces with long eye relief. What the heck is eye relief? I’m not sure what the official definition is, but I think it’s the distance your eye needs to be from the top of the top lens in order to see the entire FOV of the eyepiece. This can vary from zero to 20mm plus. If you wear glasses, you’ll want to buy ep’s with longer eye relief. How much longer? I dunno, depends. Some eyeglass wearers say 15mm, some 12, some say 20mm is their minimum. It’s one of those things that varies from person to person. Geesh, that’s starting to sound like a broken record, isn’t it?
I’m not sure if long eye relief causes this, but it looks like a good spot to talk about black outs. Some ep’s exhibit a tendency to just black out when you move your eye the slightest bit. This can be very annoying as I cannot hold my head perfectly still while viewing. My 9mm Expanse has this problem and it is going away because of it. Just something to be aware of when reading about ep’s.
Another thing to be aware of is the effect of a barlow on eye relief. If you put a 40mm plossl that has 28mm of eye relief into a 2x barlow, the eye relief will probably increase to 32mm or more. That will make it very hard to put your eye in the right place. Too much eye relief is a bad thing as well. This effect is diminished as the focal length of the ep is reduced. I put my 16mm Nagler into my 2x barlow and it only increased the eye relief about 1.5mm. On my Pentax 10.5mm, which starts at 20mm, I noticed no measurable increase in eye relief. The Powermate will not have this effect. They are a different design and will not extend eye relief.
Keep in mind that long eye relief is not just for eyeglass wearers. I don’t wear glasses and I love generous eye relief. That is one of the reasons I like the Pentax XL line so much.
4. What do you like to look at?
Besides telescope catalogues and magazines. This may be a difficult question for a beginner to answer. Or not, I guess. I didn’t know what I wanted to look at when I got my new telescope. I wanted to look at everything. But, some folks are specialists and know it. So, their ep requirements might be different from a guy who is a deep sky specialist with an occasional tryst with the planets. This is important because a DSO ep might have different design requirements than a planetary ep. For example, the orthoscopic design is a marvelous planetary ep but might not be great for large galaxies or nebulae due to its 45 deg AFOV. On the other hand, the Orion Expanse ep is adequate for DSO observing (66 deg AFOV) but not so good on the planets. So, let us know what you like to look at.
5. What are your current eyepieces?
This helps determine where you might have some holes in TFOV and/or magnification that need to be filled. It may also help determine what sort of ep preferences you have already established. For the first time owner, this might only be the stock ep’s, But since some retailers include different ep’s, let us know what those are. Also, let us know what barlows you have.
6. What is your local seeing and light pollution like?
You may not know how to answer these right away. Light pollution is fairly easy. How many stars can you see at night? How much of the Little Dipper (Ursa Minor) can you see? Can you see the Milky Way or just the skyglow from a nearby city? This is important when choosing a low power eyepiece.
For seeing, the local prevailing seeing conditions are what is important. What is seeing? Some more light reading:
Cloudy Nights article on seeing
Seeing forcast for North America (what the Clear Sky Clocks are based on)
If you live somewhere under the jet stream all the time with terrible seeing, buying an ep that goes to 400x on an XT10 might be a lesson in frustration. I live in southern MD and the jet stream spends most of the late fall, winter and early spring right over my house. The nights that I can get above 200x on the planets are rare. So, I certainly wouldn’t recommend an entire set of short focal length Radians to anyone living nearby. But, someone living in Key West or the high deserts of Arizona might be well served by ep’s with more power.
So, that’s what helps us help you. A good post asking about ep’s might read something like this:
“Hello,
I have a 10″ dob from Hands on Optics and so far I only have the 32mm and 9mm ep’s that came with the scope. I live in Detroit and like to look mostly at planets and brighter DSO’s due to the light pollution from the nearby motor city. I don’t wear eyeglasses to observe. I am looking at adding an ep to my collection and my budget is $150. Also, would a barlow be useful and, if so, which type?
Thank you,
Billy Bob”
I know that there will be recommendations to search the archives of the many groups out there. This is good advise, but my experience as a newbie searching the archives is information overload. Do a search on “favorite eyepiece” on the Talking Telescopes Yahoo group and you’ll be reading posts until a 6″ APO cost $500. So, if you get tired of trying to sort through all the posts, go ahead and ask away. Just try to be specific with your request for information. The 17th “which eyepiece should I buy” post in a week might get a deadpan response.
BOTTOM LINE (WHAT WOULD I GET)
Here’s where I put it all on the line and recommend specific eyepieces. Or not. I’m getting tired and need to go to bed, so this part will have to be finished later. For now, I’ll leave in what I wrote about a month ago when I first created this page.
“I’d get a 2x barlow first. Orion Shorty Plus, Celestron Ultima or Televue are great choices. Keep the 25mm plossl and never sell it. I still use mine. Keep the 10mm plossl for now. Add a 13-14mm ep. Budget and personal choice will dictate which one. I would get the 14mm Pentax XL. If you want to have a lot of fun for a little money, get a GTO zoom for $50.”
LIFE AFTER BINOVIEWERS
The biggest change that comes with the purchase of a binoviewer (besides the views) is the fact you have to buy 2 of each eyepiece. If you think one Nagler costs a lot, 2 costs exactly twice as much. Visit my binoviewer page for the full story on why I’m willing to shell out that much $$$ for binoviewing.
If you are considering binoviewers in the future, consider the ep’s you buy now for cyclops viewing. I had to sell my 14mm Meade UWA and 10.5mm Pentax XL because they were too big for binoviewing. Had I purchased Naglers or Radians in the first place, I would not have had to sell the larger ep’s when I got the binoviewers. I just would have had to buy 1 more of each 😉
Reading through my eyepiece list, you might wonder why I have 5 pairs of eyepieces in the 22-25mm range. I am in search of the perfect eyepiece pair in that focal range. The unanimous recommendation from the groups was the 24mm Panoptic. I bought a pair and found that my nose was a tight fit between them. Not a terrible situation, but not ideal. The 25mm plossls are very good, but only 50 deg AFOV. The 25 Epics are fantastic, but I wanted a bit more AFOV. The 24.5 Siebert Ultras are one of the most comfortable ep’s I’ve used, but they don’t perform well below f/8. Always a trade off. I’ll end up keeping the Panoptics and getting a nose job. As you can see, I am starting to work on the 9-10mm range now (7 pairs so far, but who’s counting?). Borrowing single eyepieces is fairly easy, but finding a pair to try out is difficult.
I have gotten my collection to a very comfortable point now. I have been able to do a lot of comparisons between my Denkmeier Standard binoviewers, Televue Binovues, Denkmeier 2″ OCS and Televue 2x corrector. For now, I am using the Denks for deep sky with the 2″ OCS in 1.4x mode (I measured the actual mag at 1.38x). This is my deep sky line up:
| Deep Sky | ||||
| Config | Mag | TFOV | Exit Pupil | |
| 35 Pan | Cyclops | 44x | 1.5 deg | 6.4 mm |
| 24 Pan | Cyclops | 64x | 1.0 deg | 4.4 mm |
| 24 Pans | Denks/2″ OCS/1.4x | 88x | .74 deg | 3.2 mm |
| 13 Naglers | Denks/2″ OCS/1.4x | 162x | .46 deg | 1.7 mm |
| 13 Naglers | TV/2x corrector | 235x | .33 deg | 1.2 mm |
I have found that when viewing deepsky objects, it is all about framing. You want the most magnification that the brightness of the DSO will allow. At the same time, you want to be able to see the whole DSO. That is why I prefer wide field ep’s for deep sky. The 13 Nagler gives me a .46 deg TFOV at 162x. This is a very useful magnification for a lot of DSO’s and the .46 deg TFOV allows me to get a lot more in the FOV. Interestingly, the 15mm Panoptic gives me the same TFOV as the 13 Nagler, just at a lower magnification (140x). That’s why I use the 13 Naglers for deep sky and the 15 Pans for planetary. There may be a few DSO’s that look better at 140x than 162x, but I haven’t found them yet.
I will eventually get a pair of 16mm Nagler T5’s to add to the deep sky line up, but that will have to wait.
In all my testing, I determined that the 1.4x mode of the 2″ OCS does not perform as well at high powers as the 2.5x mode. I also determined that the 2″ OCS in 2.5x mode performs as well as the Televue 2x corrector. I gotta tell ya though, it is a PITA to re-configure an OCS in the cold with gloves on. First time you drop part S on the driveway and watch it roll into the woods, you will re-consider your plan of attack. For now, I have gone back to using the Denkmeiers for deep sky and leave the 2″ OCS on it in 1.4x mode. I use the TV binovues with the 2x corrector for higher power work.
Here is a table of my high power / planetary line up. The first table is what I’m currently using with the Televue 2x corrector. The second is if I use the 2.5x mode of the 2″ OCS.
| High Power Plan w/ 2x TV Corrector | |||
| Mag | TFOV | Exit Pupil | |
| 24 Pans | 127x | .51 deg | 2.2 mm |
| 18 Orthos | 170x | .25 deg | 1.7 mm |
| 15 Pans | 204x | .32 deg | 1.4 mm |
| 13 Naglers | 235x | .33 deg | 1.2 mm |
| 11 TV Plossls | 278x | .18 deg | 1.0 mm |
| 9 Orthos | 339x | .13 deg | .8 mm |
| 7 Orthos | 436x | .10 deg | .6 mm |
| High Power Plan w/ 2.5x Denk 2″ OCS | |||
| Mag | TFOV | Exit Pupil | |
| 24 Pans | 159x | .41 deg | 1.8 mm |
| 18 Orthos | 212x | .20 deg | 1.3 mm |
| 15 Pans | 255x | .26 deg | 1.1 mm |
| 13 Naglers | 294x | .27 deg | .95 mm |
| 11 TV Plossls | 347x | .14 deg | .8 mm |
| 9 Orthos | 424x | .10 deg | .7 mm |
| 7 Orthos | 545x | .06 deg | .5 mm |
For planetary work, I find that picking the right magnification is everything. FOV becomes more of a luxury than a requirement. But a nice luxury it is. I have an eq platform so I don’t need the wider AFOV to reduce the frequency of the nudges. Even at 545x, I only nudge about once a minute. But that may be an important factor for folks with undriven scopes.
Denkmeier is coming out with a new Power X Switch OCS that has piqued my interest.
According to Russ at Denkmeier, it has an upper element that can slide out of the way. That makes switching between 1.4x and 2.5x mode easy peasy, as my daughter would say. The first ones should start shipping in Mar 2004, and I’m on the list to get one. If this works and retains the excellent optical characteristics of the original 2″ OCS, I’ll be a very happy binoviewer.
UPDATE: 27 Nov 04: The Power X Switch has been on my Denk II’s for a while now and I have a very happy lineup of ep’s for binoviewing. I am using a special low power Newt PXS that gives me 1.2x/1.67x/and 2.11x for magnification factors.
24 Pans (76x, 106x and 134x): DSO’s
13 Nagler Type 6’s (141x, 195x, 248x): Higher power DSO and most planetary/lunar work
10.5mm Pentax XL’s (175x, 241x, 307x): Better nights of seeing
9mm and 7mm UO orthos (ludicrous power): Best nights of seeing
I have used this setup for nigh on 6 months now and I am very happy with the results.
Anyway, back to the magnification story. The required mag varies according to:
1. Seeing. The single most important factor in deterring what magnification to use.
2. Object. Jupiter is less magnification friendly whereas Saturn loves to go to ludicrous power. That is, if the seeing is good.
That is why I have a few pairs of ep’s for planetary work. I like the spread with the 2.5x OCS better than the 2x corrector. I’m counting on that Denk Power X Switch OCS to save my bacon. If not, the magnification spread with the 2x corrector is still workable.
Here’s an example:
Saturn, poor seeing. The 18 orthos almost always put up a good image. The mag is pretty low at 212x, but the image is better. Go to the 15 Pans and the image will not be crisp.
Saturn, average seeing. The 15 Pans at 255x are the weapon of choice. The higher mag starts breaking out more belts on the planet and some detail in the rings.
Saturn, good seeing: Now I can start to get to what I consider good planetary power: 294x with the 13 Naglers. The image is larger so more detail is visible. The bands on the planet start resolving into myriad individual bands. I can start to make out detail in the polar hood. The crepe ring takes on a shaded look and I can make out the Enke minima. This is a sweet spot for Saturn. Go higher in mag and the moments of better seeing might put up a better image momentarily, but the image is more pleasing at the lower mag.
Saturn, great seeing: Katie bar the door! Now we are going to stupid power. I generally go right for the 7mm UO Orthos at 545x. Sometimes I wish I had more power, but at 545x, Saturn takes up nearly 50% of the FOV of the ortho. A few weeks ago, I had one of these nights. It was warmer (42 deg F) out and the sky was rock solid. My explatives must have gotten the neighbors interested because they all started migrating outside to have a peek. They sure got a treat. Saturn at 545x in steady skies. The most common comment was “Oh my God, it looks like a picture!” The tracking platform was a must for this. The capability of your telescope is the only real limit with Saturn under steady skies. My friend had his 12.5″ Portaball (Zambuto mirror) at 750x on Saturn and the image held up great. So, Saturn and steady skies = LUDICROUS POWER!
Now, Jupiter is another story. While Saturn has some low contrast detail that might disappear with too much power, Jupiter is all about low contrast detail. Too much magnification on Jupiter, even in steady skies, will look bad. The highest power I have ever used with success on Jupiter was 345x. That was in PERFECT seeing. No kidding, the seeing one morning was perfect. 10 of 10. I never saw any turbulence in the image. But that doesn’t happen but, hmmmm…., once in the past year. Most of the time, Jupiter looks best at 200-255x. Only on rare occasions do I make it above 255x.
Mars is another target that likes higher mags. Not as high as Saturn, but not as finicky as Jupiter.
So, that’s why I have so many pairs of ep’s so close together. Being able to dial in the perfect mag for the current conditions is critical to getting a quality view. When I was a cyclops viewer, I did that with barlows and Powermates. With the binoviewers, I do it with more ep’s. The bonus is I have to buy them in pairs 😉