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1.8X Siebert OCA

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#1 Guest_**DONOTDELETE**_*

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Posted 29 April 2003 - 04:41 PM

This is an initial report on the Siebert Optical 1.8 OCA as setup for a BWOptics binoviewer.The temp was between 55 to 60 degrees seeing was 4.5 to 5 in my semi-urban location.You couldn,t quite read a newspaper but dark adaptation was severely compromised.The scope used was a 15in F5 Discovery Truss-dob laser collimated at the start of the session and checked in the middle. The targets were Jupiter,M81,M82,M65,M66.Jupiter looked pretty good considering it was located above the roof of the adjacent townhouse and the mirror wasn't cooled down yet.Both equatorial bands were noted and three of the moons were sharply in focus,148x was used seeing wouldn't allow more.M81andM82 were easy targets with very good extension mottling in M82 was easily seen with direct vision with more available with averted vision.M65andM66 were once again easily aquired and very good extension was seen with direct vision, averted vision made them a little larger. 148x was used on all M objects.I was very pleased with the performance of this OCA so far.I might have been even more impressed if I had better dark adapation.I am going to a dark sky site this coming weekend I will report further details after trip.I used Siebert Optics 22.5mm Ultra Plus eyepieces for these observations. Clear skies Scotty. :)

#2 Guest_**DONOTDELETE**_*

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Posted 29 April 2003 - 05:41 PM

Glen, Im interested in how the 1.8x OCA makes, preferably, cheap plossls look, I'm trying to get some kind of handle on how the Siebert OCA's compare with my Denk' 2"OCS which I only use (cheap)25mm plossls in, I'm really interested in the look of the FOV. Flat? sharp? Any other impressions, Does the 1.8OCA have another power mode? Does it sit inside the focusser? How many elements are used? Isn't there another version of an OCA that gets 1.3x.

And sorry Glen, but is that really a photo of the actual person that goes by the name Fence Ron Sitter on the other thread - boy this is going to be interesting, Jim? and others I would love to get a gander at you all.
Scott.

#3 rboe

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Posted 29 April 2003 - 06:22 PM

Scott;

Yup, that's me. Any complaints will have to be taken up with my folks. I had nothing to do with it.

:shrug:

Ron

#4 Tom T

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Posted 29 April 2003 - 06:24 PM

... and others I would love to get a gander at you all.
Scott.


http://hatchet.badax...stro/lurch.html

Tom T.

#5 rboe

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Posted 29 April 2003 - 06:59 PM

Tom;

Do you think standing next to a dob (two no less) will make you look skinnier? :foreheadslap:

By the way, have you made your special shroud for Lurch yet?

What this has to do with 1.8X Seibert OCA's I'm not sure. But I miss the kicking girl icon.

Ron

PS: Scott, I guess it's your turn... :shocked:

#6 Guest_**DONOTDELETE**_*

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Posted 29 April 2003 - 07:43 PM

Hi Scott,I have three sets of Nexstar plossls, they don't look any better in a binoviewer than they do used in cyclops mode.I have really only used them in my F10 Nexstar8 with my BWOPTICS straight into the diagonal.I have not tried them yet with the 1.8OCA. They only have a 52degree AFOV, at high power in a dob this isn't much fun.While it's true that an AFOV greater than 52degrees isn't mandatory to enjoy a binoviewer an AFOV of 70degrees is addictive. The eyepieces I use in my Dob are 70degree AFOV designs from Siebert Optics,with the sole exception being a 32mm pair with 52degree AFOV. 4out of 5 pairs are 70degree. The 1.8OCA is almost parfocal in my scope about a 1/4 turn of the focuser to swap between a single eyepiece or the binoviewer OCA combo.FOV with the OCA in place looks just as sharp and flat and contrasty as a single eyepiece in the focuser.The OCA appears to be transparent in operation or very nearly so.Harry machined the snout on my BWOptics bino to accept the OCA.The snout has an unfortunately located baffle inside which has to be removed.With the baffle gone the OCA screws right into the snout and the upper element is as close to the beam splitter as possible.NO infocus or back focus is required.The total length seated in the focuser of the OCA binoviewer combo is 2 and 5/8in.In otherwords 1 and 11/16in. are added to the binoviewers snout.This is a single piece unit with only a single power. Harry explained that I can't effectively use the light throughput of the 1.3OCA with 22mm lower aperture the BWOptic has.Something like you can't get there from here. I don't know how many elements are used in the 1.8OCA you would have to ask Harry.I will have a better understanding of how well it works after this coming weekend,assuming the weather co-operates. Clear skies,Scotty :)

#7 Guest_**DONOTDELETE**_*

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Posted 29 April 2003 - 09:20 PM

Thought I would give Glen some help here by posting a set of pictures that shows the effect the 1.8x OCA has on an inexpensive 32mm superplossl costing about $30. The picture below shows the barlowed image when using a pair of BW Optics and the 1.8x OCA. The picture above is an unbarlowed image. Please excuse the slight difference in rotation and slight vignetting since I was holding the camera by hand and was unable to keep the lateral movement and the eye relief perfectly coordinated. This was the best out of about 25 pictures. But it definitely conveys the difference in correction between the barlowed and unbarlowed images. Well corrected eyepieces will not be overcorrected. But those that are undercorrected will certainly be enhanced with the field marginally flattened. This is a byproduct of these type of optical systems. The lower negative element increases focal length. The upper element has a postive crown at the bottom flattening the field slightly. The correction comes from an increase in focal length caused by the lower magnifier and a positive crown facing down from the upper element which flattens the field a slight bit more. What you get is a double correction which is good for undercorrected, inexpensive eyepieces. All of these type of optical systems will have similar field flattening tendencies. The lower the power the corrector typically the less correction although this is not a hard fast rule. These are a 4 element system.

Harry Siebert

Attached Thumbnails

  • 1137-CORRECTION.JPG


#8 Guest_**DONOTDELETE**_*

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Posted 29 April 2003 - 10:01 PM

Thanks Harry, my reply to Scott may have erroneously implied that I had tried the Nexstar plossls with the BWOptics-1.8OCA combination and saw no improvement.The fact is I haven't tried them with this combination yet.I will be taking them with me for sure just see what happens.I have amended my earlier post to clarify this. Scotty :)

#9 Guest_**DONOTDELETE**_*

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Posted 30 April 2003 - 06:41 AM

Thanks Glen, let us know how the plossls go with the OCA, the comparitive fields shown in Harry's photos are very familiar to me. Makes me think that at least some of the sense of comfort I get from using a bino on my f5 newt stems from the reduced need to refocus across the FOV as is required in cyclops ie, in the absence of the 2"OCS.
Scott.

#10 Guest_**DONOTDELETE**_*

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Posted 05 May 2003 - 09:40 PM

Hello Scott,here is the follow-up to my initial report on the Siebert 1.8 OCA BWOptics combination.The dark-sky site was about a Mag 6 with the Mag 6.2 star just to the east of Polaris wavering on the thereshold of direct visibility.Dan, who is one of the keener eyed members of our club could have probably seen it with direct vision.I didn't ask him because I didn't want to hear that he could also see the Mag 6.4 star directly to the Northwest with direct vision.The man causes eyesight envy.The seeing was 8to9 on a scale of 10 using the guidelines given by the Astronomical
League in The Universe Sampler.We had a period where I would say it was a solid 9 for about 2hrs. on Sat. between 11:33pm and1:30am. The temp was 57degrees at 6:00pm and had dropped to below 30degrees by midnight.I had a partially full water bottle that was half frozen by 1:00am on Sat.My 15inch Discovery truss dob has a 2.5in thick mirror with two 30cfm
3in fans mounted just above the mirror and facing one another with a 1in. offset and about a 5to7degree tilt toward the mirror they are just out of the optical path.I started them at 6:00pm and by 10:00pm the mirror was cooled down and it appeared to follow the temperature drop very nicely through-out the observing session.Other scopes present were two MagOne 12.5in Portaballs and two LX90s A homemade 14in tube dob and an 8in Discovery DHQ.Every Messier Object I looked at was an easy target and never failed to impress the other observers at the site when they looked through my bino-OCA combo.Some of the reaction was definitely due to the "Binoviewer Effect" as these people had heard about them but had nerver looked through one before.The most common comment was how much more detail could be seen and the lack of fatigue while observing.DSO challenges were Abell 2151 and Abell 1656 and another cluster in chart 37.5 in the Night Sky Observers Guide Vol.2 in the Coma Berenices section.I didn,t get the name of that one.At 100x it was strange to look at with fuzzy spots all over the field of view,like ghosts of fire-flies in front of your eyes,it was acually hard to look at.Abell 2151 was much more rewarding with many galaxies easily seen.Abell 1656 wasn,t quite as impressive.The galaxies appear smaller and were not as interestingly shaped as Abell 2151.The high point for me was seeing the connecting bridge between the two galaxies in M51 on Sat. during that 2hr.window of excellent seeing.The Messier Objects were viewed at 100x to 180x with 225x used on M5.Hard focus on M5 was acheived at 180x the image started to waver a little bit at 225x.150x seemed to offer the best views of M objects that were galaxies.Globular clusters looked best at 180x.I screwed-up and forgot try 225x on M13,it looked great at 180x.I made the ultimate sacrifice and loaned my BWOptics-1.8OCA setup to Paul our Asst.Obs.Director for approximatley 1hr.14min.16secs and I had to twist his arm to get it out of the focuser on his MagOne.He may be a convert to binoviewing. ;) The M Objects were M3,M5,M13,M92,M4,M22,M70,M69,M54,M28,M17,M65,M104,M66,M95,M96,M64,M51,M57,M27,and countless galaxies on the Coma Berenices/Virgo border.Nexstar Plossls tested were 40mm,32mm,25mm,all showed improvement in correction in the Bino-OCA combo, they didn't magically turn into Naglers.The eyepieces used for observing were Sieberts 32mm,22.5mm UltraPlus,19mm and 15mm Ultra series.The 22.5mm at 150x were slightly preferred over the others on most objects.The 19mm at 180x was the ticket on M104.Even though the light cone was split between two eyes and I was at a technical disadvantage to cyclops viewing through a 22m Panoptic in a 12.5in MagOne, in actual fact the views with two eyes in my scope appeared just as bright and I was operating at 100x to 150x.On paper I should have been noticeably dimmer.
In summation I would say that the Siebert 1.8OCA is a finely finished instrument of excellent design that delivers exactly the performance promised.It corrects to a degree the short-comings of inexpensive plossls when used in faster scopes and has excellent light through-put in combination with the BW-Optics binoveiwer.I give it two thumbs up. Clear skies and no mosquitos,Scotty

#11 Guest_**DONOTDELETE**_*

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Posted 06 May 2003 - 08:05 PM

Glen, sounds as if you had a great evening, if it was last saturday night I was sharing a few of those ancient photons from the galaxies on the Virgo/Coma B' border with you. We had a solid dark night as well, limiting mag must have been 6ish too. When the Emu (an Australian aboriginal 'constellation')is apparent you can be assured that the sky is well dark. The Emu is defined by the dark dust lanes through the Milky Way, beginning with the head of the Emu being the Coal Sac dark nebulae in Crux and the body expands on down though Scorpius, perhaps being in NZ we should call it a Moa (now extinct) anyhow...
I was Bino'd too of course (Denk and 2" OCS), although because I had, if not the first, then certainly the only bino present, I was consequently sharing those photons with not just a few other folks. Queues were the order of the evening and they didn't get any better when I took the bino out of my 10" and put it into Daves 16" dob. I eventually had to sneak around in the dark and say nothing to avoid them! :-)I might also add that no one (other than poor old Dave who has problems even with binoculars) even mentioned any difficulty merging the images. Those I did ask said ther was no problem at all)
I only have one set of EP's for the bino - 25mm plossls (as in cheap) however with the two power modes of the OCS provided for beautiful views (around 65x and 125x in my 10" and 100x and 200x in the 16") Dave was cyclops with a 16mm Nagler, and it was intriguing (although admittedly perhaps a little absurd) to compare the bino plossl vs the cyclops Nag' views. However, in short, both are a WOW view and my mind boggles at the thought of binoing with two naglers or their like! Anyhow a quick comparison at seeing mottling or arm definition in M83, as we might expect, it was probably fair to give it to the cyclops nagler but, gee, there wasn't much in it. The 'keyhole' (dark area in the bright nebula) in Carina on the other hand was more apparent in the bino - it was the old brains enhanced texture rendering process I think which just made it easier to see and define with the bino (given 'enough' brightness). Viewing Omega Centauri in the bino'd 16" brought enough Ooooh's and Ahhh's to double the length of the queue and the Nag' was never going to have that popularist effect.
The jewel box, a georgeous tight cluster with a dominant ruby star in Crux was definitely best in the bino, and if I may say, probably better even in my 10" bino'd than the 16" with Nagler (I might say the same about the Carina nebula in general really), there was such a sense of being right there, seeing it in the flesh somehow that made the bino view impossible to beat.
Anyhow thanks Glen, yes the plossls I see, are offered good correction from the OCA yet given the choice the attractions of a greater AFOV are impossible to deny.
Scott.

ps I've now got a set of 15mm plossls, woohoo - so bring on the moon, oh I see it's there and waiting... so bring on the clear skies!


#12 Guest_**DONOTDELETE**_*

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Posted 07 May 2003 - 02:08 PM

Boy, sure is a lot to take in...I am new to bino's and just picked up a used Lumicon the other day...I believe it is the same as the BW Optic one as they look identical...it came with a barlow which I was told since I use a LX-90 8in I wouldn't have to use it. Well, I don't but am confused as heck as to what all your supposed to do to get the best image. I sent an email to Harry Siebert and he was kind enough to reply and answer my question and said I should check out this forum. I was looking at the 1.8 OCA and was wondering if this would make my viewing better? Currently I am using a pair of 32's, 26's, and 15's...I have both a meade 140 barlow and the orion shorty and a 2in university all going thru my williams optics new 2in diagonal. Anyway, if someone could maybe answer my questions I sure would appreciate it very much.

James White
WPB

clueless in West Palm........hehe....

#13 Guest_**DONOTDELETE**_*

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Posted 07 May 2003 - 02:56 PM

Hi James,
I just stick my Lumicon/BW-Optics into my diagonal on my Nexstar8 and observe no special preparation required.The Siebert 1.8 OCA is a superior design and would make a great barlow if you need one at 1.8x. If you unscrew the field element from your 140 barlow this would give about 3x when screwed directly into the bottom of your binoviewer which might be handy for use on the planets.I may be stating the obvious here, but be sure to collimate your scope straight through with no diagonal,as this gives the most accurate collimation possible.The more pieces that are screwed together to assemble your optical path the greater the chance for deflection and mis-collimation.
A focal reducer from Siebert or Denkmeier might be nice for a wider field of view on open clusters.I hope to have one of Sieberts Galaxy Viewer's soon.I will let you know how it works out. Scotty :)

#14 Guest_**DONOTDELETE**_*

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Posted 07 May 2003 - 03:01 PM

Hi James,
So, u live in WPB, and I live in Loxahatchee, about 20 miles west from WPB.
I know that's not related to ur inquiry, but when I saw that u live in WPB, and wanted to drop u a line here, to introduced myself here, and updated u on what has happened with me and this newly founded hobby.
I used to be a member of PB Astronomical club back then, and it's just very difficult for me to communicate with the members in the dark, because I am deaf.
My wife is a hard of hearing herself and it's very hard for her to interpret in the dark....
I am considering to join back, but haven't decide.....because it's no fun doing it alone now....
So, anyway, I do believe u'll love the binoviewing,.and I am sure that Harry's products are very good!
I do have two sets of Harry's Ultra Plus 32" and 16"s Eps.
I like to use 16"s (65 deg AFOV) ep's for the moon and with the high powered OCS mode set up for the planetary views with my 11" Shorty.
(razor sharp than any other eps that I have here, and I was impressed)
I do have other sets of ep's beside Harry's, which are 24 pan, 19 pan, 7 nag T1.
I probably would need the set of 11 mm wide angle ep's to have the complete sets for binoviewing purpose, and I do not have that kind of money to spend right now.
The 32"s eps AFOV is too narrow (50 deg.) for me, and I am very particular with the AFOV. I have put it off putting this set and other ep's in the ads to sell.
Just that I tend got a cold feet, on each time.....oh well! Hate to be apart with them!
So, anyway, welcome to the club, and enjoy....
Talk later,

#15 Guest_**DONOTDELETE**_*

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Posted 07 May 2003 - 03:19 PM

Hi, wow! I'm closer than ya think..i'm in the acreage...if you want to shoot me a email offline i'm at jwhite@moredirect.com...i'm off Royal Palm and Orange...not far from ya I would assume...also, thanks for the welcome...just starting out with this hobby so i'm new to everything about it...trying to soak up as much info as I can...look forward to your reply....

James


#16 Guest_**DONOTDELETE**_*

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Posted 07 May 2003 - 03:37 PM

Oh my goodness...
It's a stone throw away, if u're a HULK! :grin:
I am off from Hamlin Rd, about two miles west from Seminole Pratt Rd. (Hamilin Rd is two road south of Northlake Blvd and Seminole Pratt Rd.)
Yeah, I did stop doing this hobby for a while, till the binoviewer came.
It kinda of rekinkled and I still have to relearn alot here...
It'll come back to me....just that I need to be out more often, than I normally do.
In the first few years, I was commited, but later it got jaded, after stop coming to the club.
It just stopped for a few years, till now.
We can always get together and learning together.
I do have The Sky Commander on my 20" and make it easier on us to find the objects...
I am thrilled and I am looking forward to it...
Just that I need to get busy working on my 20" and get it up and running ASAP!
I do have the 11" Shorty, but no compare with the 20"!
Keep in touch....




#17 Guest_**DONOTDELETE**_*

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Posted 07 May 2003 - 03:55 PM

OOPS.....
Emailed u offline....



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