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Anyone try the Siebert 1x OCA?

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#1 Eddgie

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Posted 04 May 2013 - 08:27 AM

Seibert sells a two-part optical set of lenses that he promotes as giving .93x with no in-travel requirement.

It appears that there are two lenses. The first screws into the front of a standard 2" diagonal using the filter threads.

The second part appears to go into the eyepeice holder, and I would assume that the binoviewwer with a 1.25" nose is inserted into the top of the diagonal.


Anyone here tried this setup yet?

#2 SteveSMS

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Posted 04 May 2013 - 04:49 PM

I've had one for quite awhile and I love it for low power wide fields. I can detect the slightest bit of astigmatism when I put in my 5mm Vixen LVs. I keep it permanently installed in the dielectric diagonal that came with my Skywatcher 120ED.

#3 Eddgie

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Posted 04 May 2013 - 08:26 PM

Thanks, Steve.

I would use it with my 6" f/8 refractor, and it would only be used for low power, so if it has some astigmatism, I would not worry about it.

Again, thanks.

#4 SteveSMS

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Posted 05 May 2013 - 08:08 AM

Hi Ed,

I use it in my 150R refractor and I have measured the exit pupil with my Denks and Orion 40mm Plossls at 7.9mm. I haven't tried in my EdgeHD 8 but it could be interesting.

Clear Skies,

Steve

#5 Eddgie

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Posted 10 May 2013 - 12:22 PM

Just as a follow-up, I just ordered one of these.

Also, for anyone that is interested, this can be used with the Baader T2 diagonal if you order a special connector.

The front element fits into the 2" nose the same way that that it does for any other diagonal (uses the filter thread).

The adapter I mentioned, allows the second element to be connected to the top of the diagonal using the T2 thread, and the Baader Dovetail is then connected to the top so that the second element is sandwiched in between.

This seems like an expensive component, but then again, it keeps you from having to buy a 1.25" nose for the binoviwer.

If it works, I could see buying a dedicated dovetail for it. That way when I used it, I could simply undo the quick connector on either side, then re-attach the Mark V directly to the ring on the top of the diagonal.

I assume that it was Harry that I talked to.

I asked him about the optics. The optics are all coated, and he says that the transmission in very good.

He also confirms that the optical quality may not be sufficient for planetary observing.

Since I don't use my 6" APO for planets, this does not bother me.

Also, this may be the solution for my EdgeHD 8". I have tried everything and cannot get the scope to work at full aperture.

This may give me back my full 8" and give me a bit wider true field of view to boot when using the EdgeHD, so I am eager to try it out.

The first lens is a mild magnifier that expands the light cone slightly.

The second element is reducer type lens.

The idea is to create a "Relay" lens that simply eliminates the distance between the lenses.

Seibert offers a 30 day return policy, so I figured it is risk free.

I did not see cutting the tube on my 6" APO as an option for me, so I hope this works out. My goal is to get a 1.4 degree field of view.

#6 Astrojensen

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Posted 10 May 2013 - 01:18 PM

This sounds very interesting, especially since I asked Al Nagler whether such a device was possible (it is essentially a one-power PowerMate) and he said it was impossible!!


Clear skies!
Thomas, Denmark

#7 Eddgie

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Posted 10 May 2013 - 03:29 PM

Well, it would appear that the two previous posters feel like this system works.

To be 100% fair about it, I asked (Harry?) about the optical quality. He was very quick to reply that planetary views might be soft.

One person reported astigmatism, but my bet is that the real problem will be that there is very likley some spherical abbration (maybe the astigmatism was an isolated issue).

I believe that what he has done was just to find low power barlow and a low power reducer that when combined together simply cancel each other out when spaced out over a particular distance.

This was one question I forgot to ask. I should have asked if the closer spacing of the Baader prism would still give the .93x he says on the web page.

I am wondering if you only get the .93 when the lenses are seperated by the typcial 4" or so of a standard 2" diagonal (which is what he shows in the pictures).

Will I get more than .93x? Or would I possible get maybe a bit less than .93x?

Will find out soon enough.

#8 SteveSMS

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Posted 10 May 2013 - 05:07 PM

Here's a photo of the one I own and have "actually used" not speculated, conjectured, or wondered about. It works as advertised despite what a competitor of Siebert Optics says. I have found that this unit when used with my own BW Optik, Denk STDs, or TV binoviewers produces slight astigmatism with Vixen 5mm EPs. The telescope(s) that I have used this in with the 5mm EPs are are a very well figured 120ED, a Vixen 102EDSS, and a, to my eye, virtually perfect Vixen FL102S that I stupidly sold. If used for what the OCA was made for, low power views, it is a truly excellent product. YMMV. but I doubt it. :tonofbricks:

Clear Skies,

Steve

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#9 Eddgie

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Posted 10 May 2013 - 10:04 PM

Thanks for the picture.

Yes, this is only for low power in my 6" APO.

I did not want to cut the tube to be able to reach focus.

I was thinking about buying a 6" or 8" reflector, but I already have the refractor, and I like the coma free performance.

So, hoping I can get about 1.4 degrees. I haven't been using the 6" since I started binoviewing, and I miss the wide fields. 1.4 degrees is not a lot for most people, but when your primary binoviewing scope is a C14, 1.4 degrees seems like a bunch of true field.

Thanks for posting.

#10 John F

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Posted 02 July 2013 - 11:01 PM

Seibert sells a two-part optical set of lenses that he promotes as giving .93x with no in-travel requirement.

It appears that there are two lenses. The first screws into the front of a standard 2" diagonal using the filter threads.

The second part appears to go into the eyepeice holder, and I would assume that the binoviewwer with a 1.25" nose is inserted into the top of the diagonal.

Anyone here tried this setup yet?



You are correct about the number of lenses and their placement. I think I may have got the very first one Harry made and sold back in 2004. I wanted one for use with a TeleVue NP127 Refractor and TeleVue binoviewer combination.

The first one Harry made for me did not work well with my setup so I returned it and he offered to try again and see if a different design would work and I'm glad to say that it did. He told the me magnification would be a little less than 1x and I tested it and compared the size of objects I was viewing between using his device and at 1x and based on the difference I subjectively estimated that the magnification factor to be about .93 and that's where Harry got that figure from. I don't know if it would be the same on other scopes but on mine that figure should be pretty close.

I've been using it for 9 years now and it has been one of the best astro-equipment investments I've ever made. With the Standard TV Binoviewer the lowest magnification/largest field I could get was 55x with a pair of 24mm Pans. With the Seibert device I can use my pair of 24mm Pans at about 26x, my 19mm Pans at 32x, my 16mm Naglers at 38x and 13mm Naglers at 47x. Of those 4 powers the one I find the most useful is 38x. It still provides a larger TFOV, a reasonable amount of magnification, and a nice dark sky background. I mainly use the 24mm Pans at 26x for large DSOs like M31 & M45. I also experience some vignetting when I use the 24mm Pans with this unit but not with the other eyepieces which don't have as wide of field stops.

In any case I would recommend trying one to see how well it works with your scope and if it doesn't Harry will probably will take it back.

During the 9 years that I've been using this device I'd had some of the most memorable Milky Way/Rich Field panning/viewing experiences I've ever had.

I'm an avid rich field bino observer and the main reason I never succumbed to the temptation to get a pair of the Kowa Highlanders (which enable 21x, 32x & 50x binocular viewing) is because of the capabilities that the Seibert device provides me with when I use it with my NP-127 Apo Refractor and the TV Binoviewer and TV's Panoptic and Nagler eyepieces.

John Finnan

#11 Eddgie

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Posted 03 July 2013 - 07:37 AM

Thanks for the detailed response.

I was a bit disappointed to hear that they may vignette with 24mm wide field eyepeices, but my scope is f/8 and maybe it is a focal ratio thing.

Also, because your scope is so fast, perhaps you goat a better (.93) reduction than I might at f/8.

Will see. I have had these on order for 7 weeks or so, with no real indication on when they will finally arrive, but hopefully in the next 4 weeks as the Milky Way gets high overhead.

#12 HowardK

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Posted 07 July 2013 - 03:40 PM

Looking forward to your report Eddgie

#13 Sarkikos

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Posted 24 July 2013 - 01:49 PM

Could this 1x OCA possibly be adapted to work with Newts?

Mike

#14 johnnyha

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Posted 24 July 2013 - 04:40 PM

Could this 1x OCA possibly be adapted to work with Newts?

Mike

Possibly, but in a fast (f5 or faster) newt you would be dealing with aperture loss and maybe quite a bit of it.

#15 Eddgie

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Posted 24 July 2013 - 06:18 PM

Initial impression is not very positive.

Of course I wanted them for low powers in my 6" APO, but when I used eyepeices with a 27mm field stop, there was bad vignetting with the relay lens close to the mirror, and when I put it at the other end, I could not reach focus.

I have not given up on it yet, but if I have to use a higher power eyepiece to eliminate the vignetting, then I would have been better off with the 1.5x GPC and a pair of Maxbrights.

Again, have not given up. I will contact Seibert and see if I am doing something wrong, but for now, I have my reservations that it will work out.

#16 dvb

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Posted 13 August 2013 - 11:40 PM

Could this 1x OCA possibly be adapted to work with Newts?

Mike


The one I have can be adapted to used either with a refractor or a reflector. I hadn't used it much with my Newts, but now that I have a 120ED, I will follow the advice above and install it permanantly in "refractor" mode in a spare diagonal.

#17 Ain Soph Aur

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Posted 15 September 2013 - 06:03 PM

Initial impression is not very positive.

Of course I wanted them for low powers in my 6" APO, but when I used eyepeices with a 27mm field stop, there was bad vignetting with the relay lens close to the mirror, and when I put it at the other end, I could not reach focus.

I have not given up on it yet, but if I have to use a higher power eyepiece to eliminate the vignetting, then I would have been better off with the 1.5x GPC and a pair of Maxbrights.

Again, have not given up. I will contact Seibert and see if I am doing something wrong, but for now, I have my reservations that it will work out.


Any update? I am buying one off these to use with a WO bv + T-2 prism diagonal and C102 GT and Carton 4" f/13 refractors.

Also, for anyone that is interested, this can be used with the Baader T2 diagonal if you order a special connector.


By the way, exactly what adapter is this that you mentioned for use with the T2?

Thanks!






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