92 replies to this topic

[ihf]

AliExpress has "TMB Planetary Oculars" for half the price of Agena, if you can wait a few weeks. I have them and they are easy to use. The flat top is a bit bulky though and they tend to rattle unless tightened. I have not used them in years, so can't say much about how much quality they really deliver. I tend not to go below 6.5mm often and like wider angle eyepieces[1]. I liked the SvBony Redline 9mm 68' when I tried it in a very fast refractor, and people say the 6mm is nearly as good. Drawback is that the Redline may cause more blackouts than the TMB and the focal length is a bit longer than you are shooting for. Not sure there are many good budget 4mm eyepieces. I assume the SvBony Gold 62' isn't going to make you happy.

 

If you are willing to spend half the price of the Pentax 5mm for the BST/TMB then why not bite the bullet and get a second copy of the eyepiece that you do like?

 

Then again 4-5mm sounds quite agressive for a BT.

 

[1] In fact when I look at planets then likely with the 6.5mm Morpheus and SkyWatcher f/9 100ED for 138x. Ay higher and I get disturbed by floaters.

[jrazz]

If you are willing to spend half the price of the Pentax 5mm for the BST/TMB then why not bite the bullet and get a second copy of the eyepiece that you do like?

With shipping and tax the Agena loosk to be $116 and would be here next week.

The TMB is $64 so yeah, pretty much half the price. 

The Pentax would be approx $280 with S&T so quite a bit more expensive. Not sure I want that for a 5% usage scenario.

 

I'm almost willing to roll the dice on the TMB just for gits and shiggles. 

[oldmanrick]

Just in case you didn't know, Pentax is having a sale on their XW eyepieces thru the end of July.  I think B&H, and probably others, have them for $266. with free shipping.  One thing to know about the Pentax XW is that their diameter is so wide that if your IPD is less than about 63mm they may not work for bino use.  At +/- 63 mm, I can barely use my XW7 pair.  Probably pretty easy to re-sell one though, if you don't like them for bino.

 

I like to buy the best that I can afford, then I spend less time wondering "what if", after purchase.

 

Rick

[elzopilote]

I sold the BT and went to a Evolution 8 telescope and it showed much more than you can see in a binocular telescope.  Now I am into EAA and that beats anything out there.  Short 8 second shots stacked show things you could never see with a BT or telescope with an eyepiece.  I also went whole hog and got a HyperStar 8 to get down to f2 instead of the normal f10 or f6.4 with a reducer.

WOW!

[jrazz]

Just in case you didn't know, Pentax is having a sale on their XW eyepieces thru the end of July.  I think B&H, and probably others, have them for $266. with free shipping.  One thing to know about the Pentax XW is that their diameter is so wide that if your IPD is less than about 63mm they may not work for bino use.  At +/- 63 mm, I can barely use my XW7 pair.  Probably pretty easy to re-sell one though, if you don't like them for bino.

 

I like to buy the best that I can afford, then I spend less time wondering "what if", after purchase.

 

Rick

Maybe I should also say that I have the 10mm and the 7mm as pairs that I use regularly. CO adds sales tax so they end up around $280. 

I absolutely love the Pentax EPs but even the 10mm is bulky, the 5mm is absolutely huge in comparison. I think that's part of my reluctance.

 

 

BTW, while EAA can definitely show more my goal is to observe with my eyes. I spend way too much time in front of a screen and there's a quality to direct viewing that simply cannot be matched by EAA and/or NVA IMHO.

[oldmanrick]

Ah, I forgot about the sales tax, we are spoiled here, we have none.  They find other ways to get our $$.

 

Glad to hear that you have and are enjoying your XW7 and XW10 pairs.  I like my 7mm's, but I think my Morpheus 6.5's are just a wee bit better plus more comfortable.

 

How do your XW10's compare to your 7's?  I'm contemplating adding a pair of 10's to my collection, but I already have 9mm Morpheus, so the 10's might be a waste of $$?   Do you consider them more comfortable than your 7's, and how do they compare for sharpness and definition?  Thanks for any info!

 

Rick

[Rich V.]

BTW, while EAA can definitely show more my goal is to observe with my eyes. I spend way too much time in front of a screen and there's a quality to direct viewing that simply cannot be matched by EAA and/or NVA IMHO.

 

I'm still after the simplicity of my eyes being the photon detectors and my paper charts as my way of manually finding objects.  For me, it's all about the peaceful experience without electronics;.  SkySafari is a great way to do my research and do some double checking of faint starfields, though I don't generally bring it outside to use all night.

 

I've seen Mallincam EAA at star parties back in the day, though, and it was remarkable the detail and color that could be seen on a monitor.  It's just not the experience I'm looking for, though.

 

Rich 

[jrazz]

Ah, I forgot about the sales tax, we are spoiled here, we have none.  They find other ways to get our $$.

 

Glad to hear that you have and are enjoying your XW7 and XW10 pairs.  I like my 7mm's, but I think my Morpheus 6.5's are just a wee bit better plus more comfortable.

 

How do your XW10's compare to your 7's?  I'm contemplating adding a pair of 10's to my collection, but I already have 9mm Morpheus, so the 10's might be a waste of $$?   Do you consider them more comfortable than your 7's, and how do they compare for sharpness and definition?  Thanks for any info!

 

Rick

If I was to have only one eyepiece (or pair) it would be the 10XW. (phew, almost wrote 10WX... Freudian?) 

Anyway, both the 10 and the 7 are comparable in sharpness, flatness, comfort, etc..., but the 10mm is a much more useful focal length. I would say that in my F4.7 Dob I use them 80% of the time and in the BT I use them 50% of the time (with the 24mm taking up 40%). 

 

So the Pentax SMC-XW 10mm is absolutely my favorite by a mile. 

 

However, I think that if you have the Morpheus 9mm and you like it you'd get nothing of value by getting the Pentax. There's just too much overlap an I don't think there's a significant optical difference.

[cimar]

eyepiece pairs of 20mm and 10mm focal length work well with my smaller BT

[jimhoward999]

I had the Oberwerk BT-XL-ED with their 70 degree 14mm and then I purchased Explore Scientific eyepieces 82 degree 8.8mm & 6.7mm eyepieces for the wider views.  Oberwerk had their own 70 degree 7mm eyepiece but I couldn't get a good focus with it and returned it for the 6.7mm.  On my BT, the 6.7mm was just about too much power and was a little dark but I loved the other two.

 

I sold the BT and went to a Evolution 8 telescope and it showed much more than you can see in a binocular telescope.  Now I am into EAA and that beats anything out there.  Short 8 second shots stacked show things you could never see with a BT or telescope with an eyepiece.  I also went whole hog and got a HyperStar 8 to get down to f2 instead of the normal f10 or f6.4 with a reducer.

Binocular astronomy and EAA are very much complimentary not mutually exclusive.  An EAA system/robotic telescope with a small refractor and Stellarmate or an ASIair (or a prepackaged version like stellina or evscope) is highly portable and sets up in less than 5 minutes. So you can set your BT and EAA side by side in two trips and just a few minutes.  No laptop, very few cables, small batteries, no ac, no big power pack.   You look with the BT, and if you can't see the object, you slew to it with the EAA livestack a few short exposure frames

and voila, image on your phone or ipad.  Or you go the other way, capture and image with the EAA then point the BT at it and see what you can see with your eyes.    My set up is shown below, an ASIAIR is attached to the telescope now as an experiment, but actually I usually use Stellarmate.

 

I didn't mean to hijack the post, I was just disappointed to see a get a BT get dropped in favor of EAA when one can do both.

 

Back on topic, my favorite eyepieces for the BT100 are the DeLite 9mm.  60X is a very nice magnification, the eyepieces are reasonably small in diameter, and they seem to work very will in the BT.  Noticeably better than the Oberwerk eyepieces.

Attached Thumbnails

• 

[Crusty99]

I've been swayed by certain people on this forum () and off to buy a 100mm BT (OB 100XL-SD). Now that I'm fully bought in, I'm looking for recommendations for eyepiece focal lengths that would be useful with this BT (560mm, F5.6)

 

So, what are your recommendations and why? Should I go for wide field x25 (22mm) or focus on really deep 80x (7mm). Something in the middle? Anyone has experience with this BT and can tell me what are the most useful focal lengths/magnifications?

Why not settle for a quality 16x70, and then save your money for a 4" and a few quality eyepieces.

 

Bob

Kentucky

[Richard Low]

For my APM 100-90 ED bino, I use the following pairs:

22mm Vixen LVW 20%, sharp to the edge of field

12.5mm Doctor 40%

8mm Ethos 35%

5mm Vixen LVW 5%

[25585]

Maybe I should also say that I have the 10mm and the 7mm as pairs that I use regularly. CO adds sales tax so they end up around $280. 

I absolutely love the Pentax EPs but even the 10mm is bulky, the 5mm is absolutely huge in comparison. I think that's part of my reluctance.

 

 

BTW, while EAA can definitely show more my goal is to observe with my eyes. I spend way too much time in front of a screen and there's a quality to direct viewing that simply cannot be matched by EAA and/or NVA IMHO.

You might like to try Nikon NAV SW eyepieces. They are smaller and lighter than Pentax, and can also be decloaked easily.

[Masonry00]

20mm -- 40%

14mm -- 30%

10mm -- 20%

07mm -- 8%

05mm -- 2%

 

If the base of the eyepiece is wider than the lock ring diameter on the BT, swapping eyepieces becomes a major pain. It is much(!) easier to swap eyepieces if the base is the same diameter or smaller because the lock can be easily tightened and loosened.

 

Wait a minute...Unless my memory is failing me, it wasn't more than a couple of months ago you said your Pentax 10mm XW's were your favorite/most used eyepieces!

[Fiske]

Wait a minute...Unless my memory is failing me, it wasn't more than a couple of months ago you said your Pentax 10mm XW's were your favorite/most used eyepieces!

Sounds more like Jordan than me. 

[jrazz]

Hmmm… yeah, I think he might have had us mixed up. I’m the 10mm aficionado.

My current preference for the BT100 is as follows:
24mm UFF: 35%
14mm Oberwerk: 5%
10mm Pentax: 50%
7mm Pentax: 5%
4mm BST planetary: 5%

[Fiske]

The Pentax 10mm XW is a superb eyepiece, one must say. Pinpoint sharp to the edge of the field, amazing ergonomics, a joy to use.

[Masonry00]

The Pentax 10mm XW is a superb eyepiece, one must say. Pinpoint sharp to the edge of the field, amazing ergonomics, a joy to use.

Agreed, I just picked up a pair of those yesterday. I must say, I like them even better than the Pentax 7mm XW's (which I have been super impressed with). All four Pentax XW eyepieces are essentially perfect, with no hint of any quality control issues and appear perfectly concentric. They blow the quality of the Oberwerk eyepieces out of the water and make me wish I had never believed the advertising rhetoric claiming that Oberwerk eyepieces were the "special sauce" that made the binoculars what they were. They are not even comparable really.

 

And it's not just the higher quality control, tighter manufacturing tolerances and better coatings that make the Pentax eyepieces stand out above the shoddy manufacturing of the Oberwerk eyepieces, it's that the design of the Pentax eyepieces seem to be tailor made for the BT-100XL while the highly hyped Oberwerk eyepieces I bought with the binoculars as additional accessories are seemingly designed for a completely different application. Which is odd considering how they are marketed. They are not parfocal with the standard 14mm eyepieces included with the BT-100XL while all the Pentax XW's are parfocal with one another. As you have already informed us, the diameter of the bases of the Pentax XW's are compatible with the diameter of the locking ring on the binoculars while the Oberwerk 7mm and 22mm are too large making them feel more awkward than a vegan in a butcher shop. Finally, the 14mm eyepieces that come standard with the BT are vastly lighter than the 7mm and 22 mm Oberwerk options which necessitates rebalancing the mount when switching between. All the 1.25" Pentax XW's have managed to keep the weight in the same ballpark which means re-balancing is not necessary when changing eyepieces.  

 

I can see offering a bargain basement set of eyepieces with the scope to keep budget orientated buyers happy, but the base diameter should at least be designed such that they seem like they are compatible with the instrument. Useability matters. Also, the lens elements inside the eyepieces must be held approximately concentric to avoid collimation issues that can seriously detract from the useability of the binoculars. This is something that anyone who sells eyepieces in pairs for binocular use should account for even if low price is one of your selling points. Service matters too. They shouldn't tell their customers who are having issues "they are within spec", everything's fine, and send them back to the customer to deal with. In other words, if you buy a binocular telescope, don't cheap out on eyepieces, it's not worth it! The Pentax eyepieces are exquisitely designed and made to high tolerances. It's almost like Pentax actually knows a thing or two about manufacturing with precision and they are more compatible with the interface of the BT-100XL than the ones offered by Oberwerk themselves! 

 

Thanks to you, Fiske, for your Pentax XW recommendation, I can finally enjoy using my instrument, after a year of frustration and wasting my time trying to figure out why my binoculars were not useable in any reasonable sense of the word!

Edited by Masonry00, 29 July 2022 - 05:24 PM.

[aznuge]

Sounds like a good pair to have for the OB BTs.

[Fiske]

Sounds like a good pair to have for the OB BTs.

  

[jrazz]

FWIW I think the Oberwerk 14mm EPs are far from bargain basement. I find them usable and pleasant. They can't, however, hold a candle to the Pentax EPs. They are not in the same league.

[Fiske]

Thanks to you, Fiske, for your Pentax XW recommendation, I can finally enjoy using my instrument, after a year of frustration and wasting my time trying to figure out why my binoculars were not useable in any reasonable sense of the word!

I'm sorry you went through so much frustration with the XL eyepieces, Masonry, and am glad the XWs are working well for you. I really love them. 

 

At their price point the XL14s are a good value, but they are half the price of the Pentax, after all. And the Pentax eyepieces are among the best on the market. They just don't get a lot of hype because of the 70 degree AFOV (compared with eyepieces like the Tele Vue Ethos with 100 degree AFOVs).

Edited by Fiske, 29 July 2022 - 06:17 PM.

[Masonry00]

 

At their price point the XL14s are a good value, but they are half the price of the Pentax, after all. And the Pentax eyepieces are among the best on the market. They just don't get a lot of hype because of the 70 degree AFOV (compared with eyepieces like the Tele Vue Ethos with 100 degree AFOVs).

Given the low price point I don't really have a problem with the XL 14's. These came with the binoculars and don't have the issues I had with my XL 7's and XL 22's. Specifically, they have the right base diameter to allow normal access to the eyepiece retainer ring. They are also much smaller and not as tall and top heavy as the other two. Not only do they fit better into the eyepiece retainers, their shorter, lighter form factor means they don't have as much tendency to rock back and forth when pointing the binoculars 35 degrees and higher from the tug of gravity. They are small and light enough that the little plastic split ring in the retainer assembly can keep them put. They were also not nearly as non-concentric as the longer and shorter pairs. That could be just luck of the draw, but I suspect the smaller elements are easier to keep centered.

 

The Pentax XW's are on a summer sale that's ending soon so the price is not that steep right now. I'm still looking for an eyepiece pair that can show the full available field of the BT-100XL's. Things that are important to me:

 

At least 70-degree AFOV so the power is as high as possible while still having the full actual field of view. A bit of vignetting is OK.

The diameter of the eyepiece base should allow normal access to the eyepiece retaining ring.

Good control of spurious reflections

Low distortion (I would prefer to avoid the "rolling ball" syndrome when panning, at least as much as possible)

I'm not too concerned with edge sharpness

 

Does such a beast exist? It seems like many eyepiece series switch to 2" barrels before they show the full field of the BT-100 XL's, no?

Recommendations? Should I just forgo the full field and go with the Pentax XW 20's? 

[ihf]

The Oberwerk has "24mm of clear prism aperture" and the XW20 has a field stop diameter of 24mm.  

[garret]

Full set, 12 eyepieces:

24

17

12

9

6.5

and 5 mm