Oberwerk BT-100


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Brand and Model:Oberwerk BT-100
Price ($USD):$1695.00
Attributes:un-checked Waterproof un-checked Armored
Objective Lens Size:100 mm
Magnification:25-62x x
Prism Type:
Coatings:Fully Multi-Coated
Field of View:2.5 degrees
Eye Relief:16 mm
Near Focus:0 ft
Weight (lbs):450 oz.
Dimensions (w/h/d):
Description:Amateur astronomers have been asking for this for years, and it's finally here- a special version of the Oberwerk Astronomy Binocular with 1.25" non-rotating helical focusers! Just like the 25/40x100mm Astronomy Binocular, broadband multi-coatings (non-reflective green/purple) are used throughout, including on the massive porro prisms. Two matched pairs of fully multi-coated wide-angle eyepieces are included- 24.43mm (25x) and 10mm (62x). And because the helical focusers are a non-proprietary 1.25" design, your favorite 1.25" eyepieces can be used as well. The eyepieces do not rotate when focusing- a feature found only on high-end helical focusers. The rest of the binocular, including the semi-apochromatic triplet objectives, is the same proven design as found in the original 25/40x100mm, but the beautiful champagne finish gives it a contemporary look.

Vote Highlights Vote
Oberwerk BT-100
BT100 – Oberwerk 100mm Binocular Telescope

I’ve had these for about a year now.

The theoretical combined effect of light delivered to the brain by the BT100, with two beautiful 100mm f/6.2 refractors, is like looking thru a 118mm scope from 21x to 69x. The visual effect seems more pronounced than that.

The BT100 is a different animal altogether than any other 5# to 12# binocular in the 80mm to 100mm range. The BT100 at 26# (12k) is heavier than my largest telescope, a 4.5' long 6" refractor. The BT100 cannot be picked up while mounted on its tripod. You must first set out the tripod then attach the BT100s. You would not move it while mounted. You must first take the binocs off the tripod.

The BT100 is a straight thru viewing binocular. The standard tripod, a specially modified heavy-duty wood surveyor's tripod results in the need to sit in a chair under the binocs to view at high altitudes. Actually, I’ve found this is very comfortable.

The views are simply stunning. It does come standard with two sets of wide WA eyepieces, a 24.5mm = 2.5°Tfov at 25x and a 10mm = 1°Tfov at 62x. Both eyepieces have an apparent fov of 62°. There is no eyepiece field stop inserted in the eyepiece housing. There is more than enough depth to insert a 2x TV barlow without hitting the prisms.

With the Oberwerk BT100 at 50x100 using 12.5mm UO orthos in mag 5.5 skies I was able to see stars to mag 12.0. The BT100 used with a pair of Televue 26mm plossls at 24x100 saw stars all the way down to mag 11.5, slightly better than seen at 25x100 with the stock 24.5mm WA eyepieces provided. While both are pretty good, neither of the supplied WA eyepieces provides the same degree of sharp view right out to the edge.

Best views yet with the BT100 were with the Televue 26mm plossl at 2.0°fov and with Televue 20mm plossl at 1.5°fov. View is quite a bit narrower than the stock WA 2.5°fov eyepieces, but in both sets of TV plossls, you can literally put objects right out to the edge of the field stop and still see a near perfect view with almost no distortion present.

The BT100 has a nice even coating with a green/purple tinge. A better indicator of the quality of antireflection coatings may be any reflections you can see when looking into them. Any reflections you see is the reflected light coming off the lens and not passing thru the lens. Look into the objectives of an Oberwerk BT100 binocular telescope and you will barely see the outline of your head. You will not see any detail in your face.

BT100s are equipped with non-rotating helical focuser, individual focus. That means if you have eyepieces with eye guard wings attached, the eyepieces don’t rotate as you focus.

The focus diopter range seems unlimited. I haven’t found the end. Accepts any 1.25" eyepieces. The Inter-pupilary distance, IPD, has a range from 58mm to 80mm. It’s possible some very large eyepieces might hit together when used for a narrow IPD. However the supplied WA eyepieces are pretty large and these do not come in contact even at the narrowest setting.

The prism housings hold what are described as massive prisms. There are three separate covered openings into the prism housings to make adjustments to the prisms if necessary. This is not like the common binocular with prism tilt screws. Collimation is quite different, very precise and well designed. The massive prisms are mounted to plates that float on three points, each point finely adjustable. I have not needed to open the housing. Using a double star of known separation, I measured image separation between the objectives at approximately 40 arcseconds. Normally separation is measured in several arcminutes. Images readily merge at every magnification I’ve used up to 50x.

The BT100 tripod is not very tall. It’s similar in height to many EQ mount scope tripods. However, it is a heavy-duty surveyor’s tripod constructed out of nicely finished wood. The binocs stand pretty tall on top of the mount post and the binocs weigh 26#. I haven't tried any other mounting setup. So far, I've been doing all my viewing with them from a seated position. Yeh, I need to bend my neck, but that's no different than every other binocular I own. The tripod assembly permits only reaching to about an altitude of 75-80°. To get closer to zenith, I shortened the two back tripod legs a few inches tilting the entire mount assembly slightly. Be very careful here, as this whole mounted setup is really very top-heavy. An off-balance tripod could be a dangerous situation. The way I had it set, if they were to topple, they would be falling towards me.

The BT100s come in a suitcase sized well-padded zippered case. They come with an easy to mount 7x (or8x?) 50mm finder scope. At magnifications below 40x, I have not needed to use the finder. I’ve actually had very good luck just pointing them at objects like the Christmas Tree cluster at 30x to 40x, looking in the view and there it was. The finder scope could be better.

I had to question whether I was seeing any false color on the edges of Jupiter's disk. There may have been a minor blue fringe, but very little. Among other objects, Sirius was observed to have no CA but seemed blue when focusing on it. Venus at 5/8 phase had no CA. Saturn had a little ghost off one edge.

AT 62x, Focus was much more difficult. Merge was slightly out of alignment. Some yellow CA on Jupiter out of focus, blue CA on Jupiter in focus. It was much more difficult finding anything with the small field of view. I did not use the finder scope. At 62x, I clearly see astigmatism, more-so in the left lens, but also in the right to a minor degree. Both sides had difficulty focus at 62x. I was surprised to find at 25x I saw NO astigmatism in the images. Had great views of many objects. Mostly open clusters, but also a wide range of doubles, the Rosette Nebula, Venus, Saturn and Jupiter.

Along with Mesartim at 7.8”, other successfully split doubles were Struve 953 Mon 7.2-7.7/7.1” at 24x = 170 arcseconds, Struve 232 Tri 8.0-8.0/6.6” at 31x for 204 arcseconds, and 95 Herc 5.0-5.1/6.3” at 25x = 158 arcseconds. I have no eyepiece combinations for the BT between 31x and 25x.

To check edge sharpness, first I used the 30” double Struve 855 about 5° or 6° WSW of the Rosette. It was still easily seen as double 80% to edge all the way around. It has a mag9+ C star which was lost from view at about 60%-70% out from center. I could still see the A-B clearly separated at 90%-95% out but the two stars had become fuzzy blobs. For this magnification (25x) the 30 arcsecond double was too wide for the test. While observing M47, I found another much closer double.

The double at the center of M47 is Struve 1121, with components of 7.9-7.9/7.4” and it was cleanly split at 25x. It was still clearly seen as a separated double at 60%-70% from center. So the 24.5mm Oberwerk WA eyepieces that come standard with the BT100 give 25x with a 2.5+ Tfov and they provide 25x7.4= 185 arcseconds resolution at 60%+ out from the center of the fov. That’s better than many people have as a limit of visual acuity even at the best resolution at the center of the fov.

In the BT100 with a 26mm TV plossl at 24x, a 14” double can be put right on the edge of the field stop and still be seen as two separate stars for an edge resolution of 330 arcseconds, a feat which I have not been able to equal with either my 16x70 Fujinons or my 12x50 Nikon SE.

Impressive views of M42 and resolved the four stars of the Trapezium at 25x. I must admit, the image of the M42 nebula in the BT100s at 36x was one of the most stunning views I have ever seen. The coatings and baffles in the BT100s seem to be a huge step up from anything I've seen.

The best low power views I had in the BT100 were with the 26mm TV plossl at 24x. The only instrument I've ever own/used that was able to see a portion of the Merope nebula is the Oberwerk BT100 binocular telescope with a pair of 26mm TV plossls at 24x with a 4.2mm exit pupil and a 2.2° fov. Using the stock 25x WA eyepiece, I saw slight definition to the Rosette nebula.

Among other objects, Sirius was observed to have no CA but seemed blue when focusing on it, Venus 5/8 phase no CA, M42 stunning, M78 seen easily, Belt nearly fits in fov, M41 had 50-75 stars, M46 was very faint but many stars are resolved, Rosette faint nebula just barely seen. Saturn had a little ghost off one edge.

Some Minuses:
Straight thru viewing
26# weight w/o tripod
tripod not very tall
supplied eyepieces OK
narrow Tfov (but expected)
minor astigmatism
minor miscollimation at high power

Some Pluses:
Interchangeable 1.25” eyepieces
Sharpness of field
Very good illumination of exit pupil
Stable mount
Superior coatings and baffles
Very little if any chromatic aberration
Stunning views

Some Suggestions for Future Consideration:
A better finder scope
45° eyepieces holders would make these unbeatable.

edz

Overall Rating: 9
Optics:10 Value:9
Weight: 10 (Trustworthy Vote)
Date:
By: edz
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=410667


Oberwerk BT-100
Great optics
Great finish
Great looks
This is the top of the line in a binocular telescope
focusers are smooth & precise
pinpoint stars across 90% of the field
minimal color on bright objects
wont break the bank purchasing one

Overall Rating: 10
Optics:10 Value:10
Weight: 10 (Trustworthy Vote)
Date:
By: vpdwl
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=205065


Oberwerk BT-100
BT100 – Oberwerk 100mm Binocular Telescope

I’ve had these for about a year now.

The theoretical combined effect of light delivered to the brain by the BT100, with two beautiful 100mm f/6.2 refractors, is like looking thru a 118mm scope from 21x to 69x. The visual effect seems more pronounced than that.

The BT100 is a different animal altogether than any other 5# to 12# binocular in the 80mm to 100mm range. The BT100 at 26# (12k) is heavier than my largest telescope, a 4.5' long 6" refractor. The BT100 cannot be picked up while mounted on its tripod. You must first set out the tripod then attach the BT100s. You would not move it while mounted. You must first take the binocs off the tripod.

The BT100 is a straight thru viewing binocular. The standard tripod, a specially modified heavy-duty wood surveyor's tripod results in the need to sit in a chair under the binocs to view at high altitudes. Actually, I’ve found this is very comfortable.

The views are simply stunning. It does come standard with two sets of wide WA eyepieces, a 24.5mm = 2.5°Tfov at 25x and a 10mm = 1°Tfov at 62x. Both eyepieces have an apparent fov of 62°. There is no eyepiece field stop inserted in the eyepiece housing. There is more than enough depth to insert a 2x TV barlow without hitting the prisms.

With the Oberwerk BT100 at 50x100 using 12.5mm UO orthos in mag 5.5 skies I was able to see stars to mag 12.0. The BT100 used with a pair of Televue 26mm plossls at 24x100 saw stars all the way down to mag 11.5, slightly better than seen at 25x100 with the stock 24.5mm WA eyepieces provided. While both are pretty good, neither of the supplied WA eyepieces provides the same degree of sharp view right out to the edge.

Best views yet with the BT100 were with the Televue 26mm plossl at 2.0°fov and with Televue 20mm plossl at 1.5°fov. View is quite a bit narrower than the stock WA 2.5°fov eyepieces, but in both sets of TV plossls, you can literally put objects right out to the edge of the field stop and still see a near perfect view with almost no distortion present.

The BT100 has a nice even coating with a green/purple tinge. A better indicator of the quality of antireflection coatings may be any reflections you can see when looking into them. Any reflections you see is the reflected light coming off the lens and not passing thru the lens. Look into the objectives of an Oberwerk BT100 binocular telescope and you will barely see the outline of your head. You will not see any detail in your face.

BT100s are equipped with non-rotating helical focuser, individual focus. That means if you have eyepieces with eye guard wings attached, the eyepieces don’t rotate as you focus.

The focus diopter range seems unlimited. I haven’t found the end. Accepts any 1.25" eyepieces. The Inter-pupilary distance, IPD, has a range from 58mm to 80mm. It’s possible some very large eyepieces might hit together when used for a narrow IPD. However the supplied WA eyepieces are pretty large and these do not come in contact even at the narrowest setting.

The prism housings hold what are described as massive prisms. There are three separate covered openings into the prism housings to make adjustments to the prisms if necessary. This is not like the common binocular with prism tilt screws. Collimation is quite different, very precise and well designed. The massive prisms are mounted to plates that float on three points, each point finely adjustable. I have not needed to open the housing. Using a double star of known separation, I measured image separation between the objectives at approximately 40 arcseconds. Normally separation is measured in several arcminutes. Images readily merge at every magnification I’ve used up to 50x.

The BT100 tripod is not very tall. It’s similar in height to many EQ mount scope tripods. However, it is a heavy-duty surveyor’s tripod constructed out of nicely finished wood. The binocs stand pretty tall on top of the mount post and the binocs weigh 26#. I haven't tried any other mounting setup. So far, I've been doing all my viewing with them from a seated position. Yeh, I need to bend my neck, but that's no different than every other binocular I own. The tripod assembly permits only reaching to about an altitude of 75-80°. To get closer to zenith, I shortened the two back tripod legs a few inches tilting the entire mount assembly slightly. Be very careful here, as this whole mounted setup is really very top-heavy. An off-balance tripod could be a dangerous situation. The way I had it set, if they were to topple, they would be falling towards me.

The BT100s come in a suitcase sized well-padded zippered case. They come with an easy to mount 7x (or8x?) 50mm finder scope. At magnifications below 40x, I have not needed to use the finder. I’ve actually had very good luck just pointing them at objects like the Christmas Tree cluster at 30x to 40x, looking in the view and there it was. The finder scope could be better.

I had to question whether I was seeing any false color on the edges of Jupiter's disk. There may have been a minor blue fringe, but very little. Among other objects, Sirius was observed to have no CA but seemed blue when focusing on it. Venus at 5/8 phase had no CA. Saturn had a little ghost off one edge.

AT 62x, Focus was much more difficult. Merge was slightly out of alignment. Some yellow CA on Jupiter out of focus, blue CA on Jupiter in focus. It was much more difficult finding anything with the small field of view. I did not use the finder scope. At 62x, I clearly see astigmatism, more-so in the left lens, but also in the right to a minor degree. Both sides had difficulty focus at 62x. I was surprised to find at 25x I saw NO astigmatism in the images. Had great views of many objects. Mostly open clusters, but also a wide range of doubles, the Rosette Nebula, Venus, Saturn and Jupiter.

Along with Mesartim at 7.8”, other successfully split doubles were Struve 953 Mon 7.2-7.7/7.1” at 24x = 170 arcseconds, Struve 232 Tri 8.0-8.0/6.6” at 31x for 204 arcseconds, and 95 Herc 5.0-5.1/6.3” at 25x = 158 arcseconds. I have no eyepiece combinations for the BT between 31x and 25x.

To check edge sharpness, first I used the 30” double Struve 855 about 5° or 6° WSW of the Rosette. It was still easily seen as double 80% to edge all the way around. It has a mag9+ C star which was lost from view at about 60%-70% out from center. I could still see the A-B clearly separated at 90%-95% out but the two stars had become fuzzy blobs. For this magnification (25x) the 30 arcsecond double was too wide for the test. While observing M47, I found another much closer double.

The double at the center of M47 is Struve 1121, with components of 7.9-7.9/7.4” and it was cleanly split at 25x. It was still clearly seen as a separated double at 60%-70% from center. So the 24.5mm Oberwerk WA eyepieces that come standard with the BT100 give 25x with a 2.5+ Tfov and they provide 25x7.4= 185 arcseconds resolution at 60%+ out from the center of the fov. That’s better than many people have as a limit of visual acuity even at the best resolution at the center of the fov.

In the BT100 with a 26mm TV plossl at 24x, a 14” double can be put right on the edge of the field stop and still be seen as two separate stars.

Impressive views of M42 and resolved the four stars of the Trapezium at 25x. I must admit, the image of the M42 nebula in the BT100s at 36x was one of the most stunning views I have ever seen. The coatings and baffles in the BT100s seem to be a huge step up from anything I've seen.

The best low power views I had in the BT100 were with the 26mm TV plossl at 24x. The only instrument I've ever own/used that was able to see a portion of the Merope nebula is the Oberwerk BT100 binocular telescope with a pair of 26mm TV plossls at 24x with a 4.2mm exit pupil and a 2.2° fov. Using the stock 25x WA eyepiece, I saw slight definition to the Rosette nebula.

Among other objects, Sirius was observed to have no CA but seemed blue when focusing on it, Venus 5/8 phase no CA, M42 stunning, M78 seen easily, Belt nearly fits in fov, M41 had 50-75 stars, M46 was very faint but many stars are resolved, Rosette faint nebula just barely seen. Saturn had a little ghost off one edge.

Some Minuses:
Straight thru viewing
26# weight w/o tripod
tripod not very tall
supplied eyepieces OK
narrow Tfov (but expected)
minor astigmatism
minor miscollimation at high power

Some Pluses:
Interchangeable 1.25” eyepieces
Sharpness of field
Very good illumination of exit pupil
Stable mount
Superior coatings and baffles
Very little if any chromatic aberration
Stunning views

Some Suggestions for Future Consideration:
A better finder scope
45° eyepieces holders would make these unbeatable.

edz

Overall Rating: 9
Optics:10 Value:8
Weight: 1 (Unreliable Vote)
Date:
By: Anonymous (xxx.xxx.149.199)
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=410666

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