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Yes, I modified my Docter Aspectem to make the best 20x80 money can buy…

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#26 RickyD85

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Posted 18 June 2018 - 03:03 AM

I can see why you say that Matt.

My 90 degree bino's are supremely comfortable for viewing, BUT I would always prefer the feeling of my head and eyes in the same direction of what i'm viewing. for that natural feeling.

I'm used to it now, but it felt odd at first looking down to see something I knew was 60 degrees above the horizon!
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#27 lit

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Posted 18 June 2018 - 10:04 AM

hi there MM

 

 

l am to wonder if this had an improvement on the illumination of the exit pupil

thanks



#28 Mad Matt

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Posted 18 June 2018 - 10:16 AM

hi there MM


l am to wonder if this had an improvement on the illumination of the exit pupil
thanks

No, if anything it is slightly worse as the panoptics use the maximum field the rear prism baffle allows. The exit pupil illumination is defined by focal ratio, prism free aperture, and where the prisms are positioned. I did not change any of that. As mentioned, there is vignetting at the field stop making it slightly blurry. Light dropoff prior to that is about 50% of the exit pupil. The drop off of illumination is notnoticable to me at least.

Edited by Mad Matt, 18 June 2018 - 10:33 AM.

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#29 lit

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Posted 18 June 2018 - 10:19 AM

No, if anything it is worse as The panoptics use the maximum field the rear prism baffle allows. The exit pupil illumination is defined by focal ratio, prism free aperture, and where the prisms are positioned. I did not change any of that. As mentioned, there is vignetting at the field stop making it slightly blurry. Light dropoff prior to that is about 50% of the exit pupil.

thanks

 

lm still trying to learn more abt binoculars



#30 GlennLeDrew

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Posted 18 June 2018 - 02:10 PM

If one wishes to upgrade a bino to a wide angle configuration, consider the model of 25X100 used by Celestron (and Burgess before Celestron got on board). It uses a front prism which has a larger half where first intercepting the light cone, thus providing full aperture performance. The focus is located just outside the body, and so is a bit more accessible for other eyepieces.

 

A seeming downside is the quite small rear prism aperture of only 17mm. It was made this small so as to provide maximal baffling consistent with the provided eyepiece's field stop of the same diameter. But here's the interesting bit. The combination of large first prism and fairly large distance the focus lies behind the rear prism aperture certainly permits to employ a 24.5mm diameter field stop, as for my own mod using 85 degree AFoV eyepieces taken from another bino. I see no discernible vignetting, and the 3.5 degree TFoV at 26X is awfully immersive.

 

I chose these eyepieces for cost considerations as well, a big part of this deriving from the helical focusing cells taken from the same bino as the eyepieces (a 10X50 Bushnell Xtra-Wide; the 7X32 could do too, it having the same body/eyepiece construction.)

 

I'd recommend seeking out the early model of 25X100, as the more recent models are not as well executed.

 

Finally, the prism cover plates will have to be left off due to their thickness in the curved molding. Simple, flat plates of thin aluminum could be fashioned to cover the area surrounding the eyepiece holder. (The holder should seat flush with the body casting itself, with no additional material lifting the eyepiece holder.)

 

In my Gallery are a couple of pics showing the assembled bino.


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#31 Mad Matt

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Posted 18 June 2018 - 02:14 PM

Sounds like a very interesting project Glenn! I will have a look

Edited by Mad Matt, 18 June 2018 - 02:15 PM.


#32 lit

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Posted 18 June 2018 - 03:26 PM

l had alook at your gallery

 

l would like to try this sometime



#33 C.Hay

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Posted 19 June 2018 - 10:22 AM

Matt, if you want to take the course Glenn has piloted, I've got a Bushnell 7x32 Extra-Wide which you could slaughter. Occasional glimpses through the resulting instrument would give me full compensation smile.gif

 

Christopher


Edited by C.Hay, 19 June 2018 - 10:23 AM.

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#34 Mad Matt

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Posted 20 June 2018 - 02:57 AM

@Glenn, Christopher

 

I did try the modified aspheric 5 element Galoc (88° AFoV) from my Huet 8x40 Marine Nationale, and the 5 element Erfle(?) from my Swift 804 8.5x44 type 3c (72° AFoV). Both have roughly a 19mm focal length which is typical for wide angle eyepieces and provide 26x in the Aspectem. The results where Ok, but not at the level I was aiming for. The Huet eyepieces had very good center sharpness but the edge performance was still not acceptable. The Swift where even more disappointing with both center and edge resolution at 26x being slightly less then what the ES 68° 24mm at 21x provide. shocked.gif I also wanted to get as close to a 4mm exit pupil as I could as these are intended for the extended faint stuff so 26x was actually more magnification then what I wanted.

 

Bear in mind that I purposely set the bar very high as I knew that if I can't get Swarovski EL class edge performance, there was no point in modifying them. As mentioned, there are obviously cheaper alternatives that are quite good. blush.gif flowerred.gif grin.gif


Edited by Mad Matt, 20 June 2018 - 03:20 AM.


#35 range88

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Posted 20 June 2018 - 04:01 AM

I think there is not a single ep on the market which can meet all your requirements, i.e., 20+ fl, sharp to the edge, super wide afov. 

You may wait for the APM 18.75, it may be the closest call, or you can simply buy a Nikon WX and dig out its marvelous ep.


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#36 Mad Matt

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Posted 20 June 2018 - 05:22 AM

I think there is not a single ep on the market which can meet all your requirements, i.e., 20+ fl, sharp to the edge, super wide afov. 
You may wait for the APM 18.75, it may be the closest call

The 24mm panoptics pretty much tick all the boxes except for super wide FoV. Unfortunately the APM, Naglers, Ethoi and other “barlowed” wide angle designs would not work without extensive modifications to the eyepieces due to the physical space the porro-I prisms occupy. Porro-II would be less of a problem but porro-I is all I had to work with. blush.gif 
 

or you can simply buy a Nikon WX and dig out its marvelous ep.

Now wouldn't that raise an eyebrow or two grin.gif not sure it that would work though... looking at the cutaway view, I am not sure where the objective elements end and the eyepiece begins. I imagine they are an all or nothing design crazy.gif


Edited by Mad Matt, 20 June 2018 - 06:05 AM.

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#37 GlennLeDrew

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Posted 20 June 2018 - 07:23 AM

The Bushnell Xtra-Wide eyepieces leave much to be desired in outer field performance due to their fairly simple design. And the eye relief is *mighty* short!

 

My suggestion primarily was to consider the 25X100 as the foundation. And I wanted to point out the surprising degree of accommodation for an 'oversized' field stop w.r.t. the small 17mm rear prism aperture.

 

The ~f/3.9 objective will be harsh for most eyepieces not having more sophisticated designs--many of whose Smyth lens could interfere with achieving focus. But if one is more like me, where it is realized that outer field softness does not significantly impair peripheral vision when looking mostly axially, a wide angle ocular's expansion of field, involvement of more outer retina and immersiveness more than compensates.


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#38 Mad Matt

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Posted 21 June 2018 - 12:56 AM

hi there MM

can u see the belts of Jupiter through these now

I need to correct myself lit. I was out last night and conditions where much better. I could definitely see the bands of Jupiter at 20.8x. Mostly as a darker region at the equator but in moments of steady air I could clearly see two distinct bands.

I also tried a few double stars. I was just able to clearly resolve stf2725 (True sep. 6.2”, Apparent sep. 129" or 2.15') as two point sources. The split was observable at the Rayleigh criterion in the center, degrading to Dawes' limit at about 50% to the edge. Gamma Delphini (8.9" true sep.) could be split to about 90% to the edge. According to Edz, Str2725 is a good test for 25x resolution so I think I can safely say that when using these, my eyes are the limiting factor for resolution, not the instrument. grin.gif


Edited by Mad Matt, 21 June 2018 - 02:22 AM.

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#39 Prescott702

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Posted 22 June 2018 - 04:33 PM

I wonder if it’s very expensive or/and difficult to modify binos and/or eyepieces for replace the stock ones in fixed straight binos

the apm 25x100 apo would be a decent cheaper alternative to the docters at 40-50x


Edited by Prescott702, 22 June 2018 - 04:36 PM.


#40 lit

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Posted 23 June 2018 - 06:17 PM

I need to correct myself lit. I was out last night and conditions where much better. I could definitely see the bands of Jupiter at 20.8x. Mostly as a darker region at the equator but in moments of steady air I could clearly see two distinct bands.

I also tried a few double stars. I was just able to clearly resolve stf2725 (True sep. 6.2”, Apparent sep. 129" or 2.15') as two point sources. The split was observable at the Rayleigh criterion in the center, degrading to Dawes' limit at about 50% to the edge. Gamma Delphini (8.9" true sep.) could be split to about 90% to the edge. According to Edz, Str2725 is a good test for 25x resolution so I think I can safely say that when using these, my eyes are the limiting factor for resolution, not the instrument. grin.gif

looks like they have excellent results



#41 Mad Matt

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Posted 24 June 2018 - 03:25 PM

I wonder if it’s very expensive or/and difficult to modify binos and/or eyepieces for replace the stock ones in fixed straight binos
the apm 25x100 apo would be a decent cheaper alternative to the docters at 40-50x

Too be honest I doubt you could improve them much. I looked through the 20x100 of the series and it was quite good. I have done several Frankenbino projects in the past and the biggest challenge is the fast focal ratio objectives. The are usually f3.8 to f4.2 and it is very difficult to find eyepieces that work well at those focal ratios without requiring extensive modifications. Even I would shy away from tearing apart a Nagler to repurpose as the tolerance of element spacing can be very tight.

Edited by Mad Matt, 24 June 2018 - 03:26 PM.

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#42 lit

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Posted 24 June 2018 - 05:15 PM

I need to correct myself lit. I was out last night and conditions where much better. I could definitely see the bands of Jupiter at 20.8x. Mostly as a darker region at the equator but in moments of steady air I could clearly see two distinct bands.

I also tried a few double stars. I was just able to clearly resolve stf2725 (True sep. 6.2”, Apparent sep. 129" or 2.15') as two point sources. The split was observable at the Rayleigh criterion in the center, degrading to Dawes' limit at about 50% to the edge. Gamma Delphini (8.9" true sep.) could be split to about 90% to the edge. According to Edz, Str2725 is a good test for 25x resolution so I think I can safely say that when using these, my eyes are the limiting factor for resolution, not the instrument. grin.gif

hi there MM

 

last nite l was lookin for belts of Jupiter in my 22x rather (21)x70 WO semi apo with gibbous Moon near by

 

l was able to see the Belts and some of the Polar Brown markings only after l first looked at the bright Moon..for awhile ...to make my eye pupils smaller aperature

 

seen excellent results,,thought l would like to share this

 

l will try tht on Saturn on the rings next time its clear

 

other wise l had a hard time at all trying to see belts on Jupiter


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#43 CAAD9

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Posted 25 June 2018 - 06:47 PM

Congratulations Matt on an awesome project.

 

Great thread everyone, learning lots here.


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#44 C.Hay

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Posted 29 June 2018 - 06:03 AM

Dear Matt,

 

Thanks for your report on resolving stf2725 (True sep. 6.2”, Apparent sep. 129" or 2.15') and Gamma Delphini (8.9" true sep.) in your FrankenAspectem. I often use Gamma Del to test resolution at 20x and am delighted to learn that there is an excellent 25x test star just a few arcminutes below Gamma.

 

I am most impressed that you can resolve stf2725 at 20.8x. This really shows how excellent the overall system must be (and tells a little about your excellent eyesight).

 

Please keep up the reports about what you can see with this instrument!

 

CS, Christopher


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#45 Mad Matt

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Posted 30 June 2018 - 04:12 AM

Dear Matt,


I am most impressed that you can resolve stf2725 at 20.8x. This really shows how excellent the overall system must be (and tells a little about your excellent eyesight).

Please keep up the reports about what you can see with this instrument!

CS, Christopher

Have good eyesight is both a blessing and a curse. 😳 it’s nice being able pick out details at slightly lower magnifications but also means that often what i see is limited by the optics, not my eyes. That ultimately drives me to spend more money then my wife would like me too and do other crazy things like this project 😳😁

I think my acuity is quite good up until about a 4mm exit pupil but starts to degrade after that. Between 5 and 6.5mm (my maximum) a have noticable astigmatism that turns brighter stars into comets.

I have yet to find an optometrist that can test my eyes at maximum EP so I simply stick to smaller EP’s for now until it gets worse.

Edited by Mad Matt, 30 June 2018 - 04:14 AM.


#46 garret

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Posted 30 June 2018 - 05:25 AM

 

I have yet to find an optometrist that can test my eyes at maximum EP

Maybe Zeiss i-scription is what you are looking for, it measure your eyes also when the pupil is wide...

However it cannot measure correctly if your eyes-pupils in the dark are too wide, I have tried this test but it failed... my pupils are too wide! 

https://www.zeiss.de...echnologie.html



#47 Mad Matt

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Posted 30 June 2018 - 09:11 AM

Maybe Zeiss i-scription is what you are looking for, it measure your eyes also when the pupil is wide...
However it cannot measure correctly if your eyes-pupils in the dark are too wide, I have tried this test but it failed... my pupils are too wide!
https://www.zeiss.de...echnologie.html


Many thanks for that Garret! I will definitely look into that. According to the website there is an optometrist with the device not too far from where I live.

#48 Mad Matt

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Posted 09 July 2018 - 11:38 AM

I was out late last night with the 20.8x80 and its sister sibling the 40x80 UWA. At 50° North latitude it does not get completely dark here at this time of year but the excellent transparency made up for that. I did not scientifically measure it but I would judge the NELM was about 5.8 mag. I forgot the UHC filters so all observations where done "naturally" using the full spectrum laugh.gif .

After "warming up" on Jupiter and Saturn with the UWA, the first object with the 20.8x80 was the North America nebula (NGC 7000). The gulf region was immediately visible with the outer extents towards "Canada" being more challenging due to the background milky way. I was able to to roughly trace most of the nebulas extent by paying specific attention to the differences between the grainy appearance of the milky way and the more diffuse glow of the nebula. This is where the sharpness these provide really paid off.

Obviously, next up was the Veil Nebula. blush.gif The eastern component really jumped out nicely. On the western component I could easily see the bright wisp that extends north of 52 Cyg (and is easily mistaken for glare from that star) but the the southern portion was much more challenging. I tried to pick out Pickering's Triangle but had no luck. Simply not enough aperture for the sky conditions.

Feeling somewhat overconfident, I moved up to the Gamma Cyg to see if I could catch see the brighter parts of IC1318. To my surprise I was able to see nebulosity in both of the bright areas east of Sadr (Gamma Cyg). On a side note... The combination of exit pupil and sky conditions made a cool angular figure "8" asterism jump out about 3° due east of Sadr. Unfortunately I cannot simulate it in Skysafari but once my brain registered it I could not stop seeing it grin.gif .

I then moved towards the south a little to give the bubble nebula a try but had no luck seeing it.

I continued south towards the steaming teapot stopping at the usual suspects along the way. I also spent some time scanning the dark nebula in Scutum (which are absolutely gorgeous in this instrument) and "stumbled" across M11... The funny thing is that I did not recognise it at first blush.gif... At 20x it was only partially resolved which made it look more like Omega Centauri then the M11 I remembered seeing last in the 40x80 and 100mm APM. tongue2.gif The 3.8mm exit pupil and small image scale made for very interesting views with dark lanes intersecting the central portion and the outer regions becoming more predominant. This was the most fun I had ever had looking at M11. grin.gif

I then spending some time on the usual suspects in the area (M16, M17, M18, M20, M8, etc.). I occasionally switched between the 20.8x80 and 40x80. As to be expected, the 20.8x80 showed less detail then the 40x80 but allowed more of the fainter areas of the nebula to be seen.

I closed up the night with a quick look at M33 and M31. M33 was still a bit too low for me to be able to tickle out any details but still I could see a hazy patch with a notable brighter core. M31 was a wonderful sight with the faint outer extents taking up almost the entire FoV. I suspect it to be an optical illusion but I have on several occasions had the feeling that visually, M31 extends further out then what is shown on photographs. I though I could just make out the rear dust lane (on the M101 side) but only indirectly and after about a minute of relaxed viewing. It may have been my brain wanting it to be there so take that with a grain of salt.

In summary, I am very pleased with the modification and have absolutely no regrets. Now I need to modify my p-mount to mount both Aspectems simultaneously so I can easily swap magnification without having to fiddle with eyepieces or even get out of my chair cool.gif


Edited by Mad Matt, 10 July 2018 - 12:30 AM.

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#49 Mr. Bill

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Posted 09 July 2018 - 12:22 PM

You should repost this over on the "what I saw last night..." thread....very good narrative. 

 

I particularly like your description of the nebulae around Sadr; I use them as a test of sky conditions.

 

High summer is indeed a treasure trove of MW goodies.

 

watching.gif


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#50 jrbarnett

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Posted 09 July 2018 - 01:00 PM

That would be an honor Sir! Stellafane is actually on my bucket list

Are you an astronomer or a historian?

 

I'd think you would want conditions not like home - i.e., high elevation, low humidity, black zone darkness, etc.

 

Go west young man!

 

Those 80mm used at Stellafane (Yellow-Green zone; 1200ft elevation) would act more like 110mm if used at a darker, higher, drier star party locale and as an added bonus you'd have access to deep south targets like Omega Centauri and Centaurus A.

 

:grin:

 

- Jim


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