29 replies to this topic

[Waterobert]

I will be getting Oberwerk BT100 next week and would like to get some solid recommendation for eyepieces. Since I am overspending on the binoculars I can only afford one pair of objectives. BT100 comes with 14mm ( 40 power ), so I am thinking of getting 11mm or 9mm. That will give me 51X or 62X. It is not that much more then 40X, should I get 7mm ( 80X ). At home, my sky is Bortle 6-7and at my dark site is class 4 Bortle. I only drive to the dark site 3-4 times a year, so I am thinking that in light polluted sky going to 80 power will not give me that much more details. I do have one Nagler 6  5mm ( 112X ), but I am guessing that such big magnification is not very practical. I can only afford one set, so I want something I will be using all the time and hopefully be satisfied for a long time. My next set will be Panoptic 24mm, but those are even more pricey. What magnification do you guys use most often? How often do you go to 60-80 power? Are BT 100 even big enough to go to 112 power?

Thank you for your advise ! 

[John Miele]

With my BT100 I used the following:

 

APM UFF 24 - gives widest possible field. Used about10% of the time

 

Morpheus 17.5mm - delivers superb wide and contrasty view. Used about 50% of the time

 

10mm Delos - Maximum power choice for me for DSO. Just below 2mm exit pupil for perfect ration of brightness and detail - Used 40% of the time

 

5mm Delites - Only used for planets and occasional double stars. The BT100s could handle the power, but tracking, merging, and focusing becomes difficult and I have other options for high power. So these were almost never used.

 

cs...John

[wrighty338]

Have a look here

[fishhuntmike]

My yard is ~ Bortle 6/7. I mostly use eyepieces between 12-18mm probably 75% of the time and the other 25% of the time either a 22-24mm or 9-10mm eyepieces. I rarely use my 6mm pair. If you go with an ED a widefield eyepiece may be more useful. I like the stock 14mm 70deg eyepieces, a good all around performer in ED or SD BTs and great for Bortle 6/7.

[jupiter122]

With my BT100 I used the following:

 

APM UFF 24 - gives widest possible field. Used about10% of the time

 

Morpheus 17.5mm - delivers superb wide and contrasty view. Used about 50% of the time

 

10mm Delos - Maximum power choice for me for DSO. Just below 2mm exit pupil for perfect ration of brightness and detail - Used 40% of the time

 

5mm Delites - Only used for planets and occasional double stars. The BT100s could handle the power, but tracking, merging, and focusing becomes difficult and I have other options for high power. So these were almost never used.

 

cs...John

You said "The BT100s could handle the power (5 mm?), but tracking, merging, and focusing becomes difficult and I have other options for high power."  I am having difficulty reconciling "could handle" with "focusing become difficult" for instance.  Can you explain?

 

Thanks!

 

Tim

[John Miele]

Focusing is difficult at high power because of mount shakiness. You need a very sturdy vibration free mount or it take a while to dial in the focus. But once focused, the 5mm gave a sharp view. If you have a rock solid mount, then the focus jitters is not an issue.

[Mike G.]

How steady are you at the EP?  Myself, I have a little bit of the shakes at 69 y.o. and keeping two sub-2mm exit pupils lined up without blackouts is a problem.  My lowest EP for my APM 100's is the 11mm DeLites although the APM's can definitely produce fine images down to a 5mm EP.  If I want more power, I get a scope out.  Much easier to keep small exit pupils in view when you only have to deal with one.  Personally, I would go the other way since you are budgetarily constrained and get something in the 20-25x range.

[dustyc]

None of them. The undercut and smaller barrel allows the Delites to slide down the eyepeice holder barrel when the binos are rotated past 45 degrees vertical. They don't fall out but it will give you pause when it happens. With 90 degree binos it is less significant.  If you're ok with copper tape on the barrels of the eyepiece set, that works (I'm not). 

[Waterobert]

None of them. The undercut and smaller barrel allows the Delites to slide down the eyepeice holder barrel when the binos are rotated past 45 degrees vertical. They don't fall out but it will give you pause when it happens. With 90 degree binos it is less significant.  If you're ok with copper tape on the barrels of the eyepiece set, that works (I'm not). 

What would you recommend instead of Delites ? Thank you

[Waterobert]

Takahashi eye TPL 12.5mm has no undercut, however it is only 48 degrees. Not sure if narrow field is recommended for BT , Oberwerk eyepieces are 70 degrees.

[dustyc]

What would you recommend instead of Delites ? Thank you

The 7mm set from Oberwerk are kinda tight on eye relief for me. Right price though. My highest power sets (9 and 6.5mm) are the Morpheous. Big sweeping views, love 'em. I wear glasses. 

[TomK1]

In terms of pairs used with my BT100XL-SD, I have:  24 mm Panoptic, 14mm Oberwerk, 18/11/9/7/5mm Delites.  I would go with a 7mm  Delite and then 24mm Panoptic (it has no undercut) or an 18mm Delite: sort of what Oberwerk sells and recommends.   I would then fill in the gaps with something around 10mm.  Initially low, medium and high will be satisfying.     

 

My ipd is small and I could not use the initially purchased Pentax XW 20/10/7mm: the circular fov would never overlap although the images were merged perfectly, and that is after I removed the rubber barrel, cut off the silver circular filler ring and carefully filed down the flange so it was the same diameter as the barrel body.  I would have never bought the 18/11/9 pair and an additional 5/7mm Delite ( I already owned a 5 and 7mm Delite) if the XW's had worked with my IPD:  very expensive lesson on ensuring your ipd is matched with the BT and eyepiece barrel. I'm glad I never bought the BT120 which has a larger min IPD.  

 

For the Delites, as recommefdended by others, I cut strips of aluminum duct tape with a razor blade, filled in the undercuts till they were flush to either side of the barrel:  absolutely no issues with my eyepieces fitting snuggly and no issues whatsoever with the images merging.  As it stands, I use all the eyepieces. Low power for sweeping views of lots of stars or large nebula.  Medium power for galaxies, open clusters and nebula. High power for planets, doubles and globular clusters.   I like the longer eye relief with the Delites and Oberwerk 14mm.  For more definition in the image, I use my dob at 112X or 185X.

[revans]

I will be getting Oberwerk BT100 next week and would like to get some solid recommendation for eyepieces. Since I am overspending on the binoculars I can only afford one pair of objectives. BT100 comes with 14mm ( 40 power ), so I am thinking of getting 11mm or 9mm. That will give me 51X or 62X. It is not that much more then 40X, should I get 7mm ( 80X ). At home, my sky is Bortle 6-7and at my dark site is class 4 Bortle. I only drive to the dark site 3-4 times a year, so I am thinking that in light polluted sky going to 80 power will not give me that much more details. I do have one Nagler 6  5mm ( 112X ), but I am guessing that such big magnification is not very practical. I can only afford one set, so I want something I will be using all the time and hopefully be satisfied for a long time. My next set will be Panoptic 24mm, but those are even more pricey. What magnification do you guys use most often? How often do you go to 60-80 power? Are BT 100 even big enough to go to 112 power?

Thank you for your advise ! 

I would not get any eyepieces that have slopes or undercuts.  As far as I know all Morpheus eyepieces work well and do not have them.  Neither do any of the Oberwerk eyepieces.

 

Rick

[jrazz]

I don't think Delites are a bad choice. I used Delites in my BT-100 successfully. The notch is annoying and you do need to fill it with aluminum tape but it's not a dealbreaker.

To me, the problem with Delites is the value proposition. Televue eyepieces seem to be really good for fast newtonians but seem to be somewhat of an overkill on refractors. Especially in a binocular sense where the periphery is less important.

 

On a binocular you don't really look at the periphery like you do in a telescope. In the latter you can move your head and actually observe with the enter of your vision at the periphery of the eyepiece. In that kind of use case the sharpness of the periphery matters a whole lot. With binoculars you lose the ability to move your head in relation to the eyepiece and therefore you only really use the center. That's why you hear recommendations for narrower eyepieces for use in a BT.

 

Case in point. I had used the Takahashi TPL eyepieces for quite some time and they are positively EXCELLENT for a BT, especially the BT-100.

 

Once I switched to the EMS equipped DoubleTak I could accommodate eyepieces with an undercut more easily and then I switched to the AT-UWA. Side by side the UWA are ever-so-slightly less sharp than the TPL but the wide width does feel very nice. Again, not really usable but it's a fun experience.

 

 

At the end of the day eyepieces without a notch are easier to use. TPL if you don't use eyeglasses, Vixen SLV if you do.

 

You can also fill in the notch and use whichever eyepiece you like.

 

[GADify]

In terms of pairs used with my BT100XL-SD, I have:  24 mm Panoptic, 14mm Oberwerk, 18/11/9/7/5mm Delites.  I would go with a 7mm  Delite and then 24mm Panoptic (it has no undercut) or an 18mm Delite: sort of what Oberwerk sells and recommends.   I would then fill in the gaps with something around 10mm.  Initially low, medium and high will be satisfying.    

 

This is similar to what I did when I got my BT-82XL-EDs. I now have: 

 

24mm Panoptic

18.2mm DeLite

14mm Oberwerk

11mm DeLite

7mm DeLite

 

I rarely use the 7s. Honestly, I mostly use the 24mm and 11mm. 

[Waterobert]

Lots of good information, thank you.

Since I am new to the BT, maybe I should start with lower magnification. BT 100XL come with 14mm ( 40 power ), perhaps  I should go to 24mm first.

How Takahashi TPL 25mm (22.4X) would perform vs TeleVue 24mm Panoptic (23.3X)? Panoptic has wider AFV, Takahashi is only $200. Better price vs wider field.

[jrazz]

You don't have to spend a lot of money. 

If anything I found the cheap eyepieces very comparable to expensive ones. The Panoptics are great and will give you a wide field but a set of cheap 25mm Plössls are a great start. I would avoid 33mm Plössls though as they tend to have annoying amounts of distortion.

 

The only eyepiece I would spend real money on is the 9-11mm range. That is where the BT seems happiest. Get a good eyepiece for that range. Morpheus and Pentax are good candidates if your IPD is sufficient.

[wrighty338]

+1^^^

 

What are you looking to observe? the standard EP's deliver 40x on the BT100 this may be plenty, or you may want to go down to a 22mm/24mm for that classic 25x100 view? Iv found im more inclined to zoom in than out on my BT so you might want to try a cheap 24mm rather than getting spendy on the panoptics to begin with?

 

Lots of good information in the eyepiece forum, according to what i read the KUO UFF 24mm delivers 90% of the performance of the 24mm Panoptic for much less money, you might want to spend less on zooming out so you can spend more on zooming in where the EP quality may matter more? YMMV but that's my take

 

https://oberwerk.com...-compatibility/

 

https://oberwerk.com...e-secret-sauce/

[fishhuntmike]

+1^^^

What are you looking to observe? the standard EP's deliver 40x on the BT100 this may be plenty, or you may want to go down to a 22mm/24mm for that classic 25x100 view? Iv found im more inclined to zoom in than out on my BT so you might want to try a cheap 24mm rather than getting spendy on the panoptics to begin with?

Lots of good information in the eyepiece forum, according to what i read the KUO UFF 24mm delivers 90% of the performance of the 24mm Panoptic for much less money, you might want to spend less on zooming out so you can spend more on zooming in where the EP quality may matter more? YMMV but that's my take

https://oberwerk.com...-compatibility/

https://oberwerk.com...e-secret-sauce/

I agree. My UFF 24mm and OB 22mm are good enough for me. Even though the 70deg 22mm has a slightly soft field stop it is wide and priced right and I am quite happy with it.

Since the OP was referencing the ED instead of the SD I also agree as Jordan did that a 9-11mm is good eyepiece to go with the stock OB 14mm for a higher power. I like the 10mm XW in my Orion BT100 ED. I tried 6mm but wasnt satisfied with the loss in sharpness but 6mm works fine with the SD BTs.

Edited by fishhuntmike, 20 April 2025 - 09:16 AM.

[Waterobert]

Thank you guys for you opinions, I appreciate them all !

My IPD is under 60mm so Morpheus and Pentax are not going to work for me. I am intrigued by Takahashi TPL series, recommended by jrazz. What are your thoughts about 9mm TPL?

Also, I didn't order BT100xl yet, I was going to go with ED version but SD will be a little better for planets. Today is the day I have to make my final choice 

Edited by Waterobert, 20 April 2025 - 10:21 AM.

[jrazz]

If you have a narrow IPD then the TPL are very highly recommended! They are very comfortable.

 

The eye relief numbers are short especially with the 9mm and the 6mm but the reality is that they don't feel as short. Certainly not for use with glasses but they are super easy to use.

Like I said before, if eye relief is an issue then the Vixel SLV are the solution.

[balcon3]

Thank you guys for you opinions, I appreciate them all !

My IPD is under 60mm so Morpheus and Pentax are not going to work for me. I am intrigued by Takahashi TPL series, recommended by jrazz. What are your thoughts about 9mm TPL?

Also, I didn't order BT100xl yet, I was going to go with ED version but SD will be a little better for planets. Today is the day I have to make my final choice 

I think you could be disappointed if you are expecting detailed planetary views with the BT100. For planetary it is more satisying to get to 150x or more, and I don't think your BT's can get there easily. Preferable would be a regular 100mm refractor with a binoviewer, or better yet a 12omm-class refractor, if you can deal with the size.

[Dale Smith]

+1 on Jordan’s comment about the Vixen SLV—use a pair of 9mm SLV EPs in my 82mm BT. Gives great “whole Moon” views of Luna, along with showing the two EB on Jupiter, Saturns rings, and especially goes deeper on open clusters.

Edited by Dale Smith, 20 April 2025 - 11:14 AM.

[Astromancer]

 

I don't think Delites are a bad choice. I used Delites in my BT-100 successfully. The notch is annoying and you do need to fill it with aluminum tape but it's not a dealbreaker.

To me, the problem with Delites is the value proposition. Televue eyepieces seem to be really good for fast newtonians but seem to be somewhat of an overkill on refractors. Especially in a binocular sense where the periphery is less important.

 

On a binocular you don't really look at the periphery like you do in a telescope. In the latter you can move your head and actually observe with the enter of your vision at the periphery of the eyepiece. In that kind of use case the sharpness of the periphery matters a whole lot. With binoculars you lose the ability to move your head in relation to the eyepiece and therefore you only really use the center. That's why you hear recommendations for narrower eyepieces for use in a BT.

 

Case in point. I had used the Takahashi TPL eyepieces for quite some time and they are positively EXCELLENT for a BT, especially the BT-100.

 

 

Once I switched to the EMS equipped DoubleTak I could accommodate eyepieces with an undercut more easily and then I switched to the AT-UWA. Side by side the UWA are ever-so-slightly less sharp than the TPL but the wide width does feel very nice. Again, not really usable but it's a fun experience.

 

 

 

At the end of the day eyepieces without a notch are easier to use. TPL if you don't use eyeglasses, Vixen SLV if you do.

 

You can also fill in the notch and use whichever eyepiece you like.

 

 

 

Jordan, how easy is it to fill in the notch? I tried my TV Nagler T6 7mm  in my BT-120XL for size today and couldn’t really get them to stay in place because of the notch. Based on your recommendations I purchased a pair of AstroTech UWA 10mm and those have very slight undercuts. They weren’t as easy to seat as the Oberwerk 14s, but I got them to stay snug and they looked great. I would love to avoid having to purchase a different set of 7mms given that I already have the Naglers.

 

Hopefully the clouds will clear a bit tonight so i can actually get everything outside and actually look at the skies, as opposed to the woods outside my house…

 

Chris

[jrazz]

Not too hard. You can get thin copper foil tape: https://www.amazon.com/dp/B0C3Z37LZK/

 

It might take a couple a tries. If you already have the Nagler it's worth a try.

 

 

 

I will say this. The UWA are wonderful little eyepieces and a set of 7mm, 10mm and 16mm will cost about the same as one set of Naglers.