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Lunt LS50 H-Alpha scope and Siebert Black Night binoviewers

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#1 saguaro

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Posted 13 May 2015 - 01:38 PM

I recently received my Seibert Black Night binoviewers from Siebert Optics (http://www.siebertoptics.com/). I also purchased the Siebert 1.2x OCA that allows my Lunt 50 to achieve focus without over-magnifying the image. I have found that eyepiece pairs in the 15mm - 20mm range work best but higher magnification (around 12mm) is also usable.

 

Here are my Seibert Black Night binoviewers mounted on my double-stacked Lunt LS50. One of the great features of the Black Nights is their light weight, which is a good match for a small scope like the Lunt 50. I can achieve good balance on my small equatorial tracking mount by sliding the scope forward in the dovetail mount. The double-stack module which screws onto the front of the scope also helps to balance the added weight of the Black Night binoviewers.

 

Binoviewer and Lunt LS50.JPG

 

Black Night binoviewer.JPG

 

After a bit of troubleshooting with Harry Siebert, I discovered the best placement of the two lens elements that comprise the Siebert 1.2x OCA so that I can achieve focus with various eyepiece pairs.

 

The 1.2x OCA has two lenses numbered #3 and #4. The #3 lens cell is threaded into the binoviewer's 1.25-inch nosepiece. The #4 lens cell is threaded into the rear of the Lunt diagonal's nosepiece (after removing the O-ring on the #4 lens cell), shown here:

 

Part 4 position for most eyepieces.JPG

 

I have been able to achieve focus with 15mm and 20mm eyepiece pairs. I also tested this configuration with the one Lunt zoom eyepiece that I have, and the Lunt zoom can achieve focus across its entire zoom range.

 

The pair of Baader zooms I have did not quite come to focus - I needed a bit more inward focus travel than the Lunt Helical focuser allows, even with both diopters fully lowered on the binoviewer. Here is a photo of one of my Baader zooms next to the Lunt zoom; the Baader zoom has a slightly longer optical path length:

 

Baader zoom and Lunt zoom.JPG

 

I also tried threading the #4 lens cell into the front of the diagonal's nosepiece as far as I could. I found that I needed a bit more outward focus travel than the Lunt Helical focuser allows. I was able to just achieve focus with the Baader zooms by extending the height of the diopters, but I would much prefer to use the Helical focuser because it's more convenient than having to fiddle with both diopters just to get focus.

 

It appears that if I could move cell #4 further inside the diagonal nose, I could achieve focus with the Baader zooms. Harry has told me he can make the cell #4 placement adjustable, so I am just waiting to hear back from him about this.

 

The Black Night binoviewer is very easy to use, and the self-centering diopters are very well executed. Even the Baader zooms with their undercuts on the barrels stay fixed in the eyepiece holders and don't wiggle around. However, I am going to replace the Baader zoom barrels with the custom smooth barrels currently being fabricated by Gary Susik (vkhastro1), so that they will work better with the eyepiece holders on my Binotron which I use with my C-14 SCT.

 

It is fantastic to be able to use both eyes for solar viewing. The double-stack module on my Lunt 50 does not significantly reduce the overall brightness of the solar disk, so that's not a concern for me. I do use a Dark Skies Apparel Observing Hood (the white one with 2-layers of black lining) which I find is indispensable for solar viewing.


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#2 nickatnight

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Posted 13 May 2015 - 05:44 PM

Thanks for the great write-up. I'm actually a big fan of two eyed viewing, and have been waiting to see what you came up with. I've got white light filters for my 25x100 binos I enjoy using. Not sure I'm ready for the Bino viewer path yet. Seems like their might be a lot of fiddling to use various eyepieces, and I'm not a fan of fiddling while viewing. I have been curious if the LS50 can be used side by side as a Bino Telescope. Yet to do the measurements. I too picked up the white Dark Skies Apparel hood and love it. I also just ordered an eyepatch as I like keeping both eyes open, and even with the hood there's a slight speckling of light with both eyes open. Then again, I'd be happy viewing from a sensory deprivation chamber.
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#3 saguaro

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Posted 13 May 2015 - 06:01 PM

I have been curious if the LS50 can be used side by side as a Bino Telescope. Yet to do the measurements.

I know it's been done with PSTs and the Lunt 35. Now that you've brought it up you simply must do this and let us know  :waytogo: 



#4 saguaro

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Posted 13 May 2015 - 06:09 PM

I just heard back from Harry. He suggested I try screwing the #4 cell further into the back of the diagonal nose (as seen in my photo above). I just tried it again and I can in fact screw the #4 cell further into the back of the nosepiece than on my earlier attempt. I can screw it in so no threads are showing, and only the unthreaded end of the #4 cell stick out. I guess I didn't want to force it and risk stripping the threads on the diagonal nosepiece. Now I see that it was just the black anodizing paint on the threads that was preventing me from threading it in further. I will try this next time I get some clear weather here in southern Arizona. We are having unusually cool and cloudy May weather, but I'm not complaining since normally temperatures would be in the 90's by now instead of the 80's. :)



#5 saguaro

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Posted 15 May 2015 - 05:48 PM

I can now confirm that by threading the #4 cell further into the back of the diagonal nose, I can achieve focus with all my eyepieces, including the Baader zooms.

 

IMG_1511.JPG

 

I picked up a second nosepiece from Lunt (cost $20). This allows me to keep the #4 cell threaded into one of the nosepieces, for use with the binoviewer. For monoviewing, now all I have to do is swap nosepieces, so it's pretty convenient.


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#6 Live_Steam_Mad

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Posted 31 December 2017 - 01:13 AM

It appears that you are inserting your binoviewer into the rear end of the Blocking Filter / diagonal's eyepiece holder on your Lunt 50. I came across someone who is instead directly screwing their binoviewer nose end into the Blocking Filter / diagonal on their Lunt 60, by firstly simply removing the eyepiece holder on their BF (easy to unscew) ;-

 

https://stargazerslo...comment=3225382

 

https://stargazerslo...comment=3125197

 

...this same guy also uses a Baader NT Focuser with their Lunt 60 instead of the stock focuser - although I am concerned whether this focuser fits the LS50, details here ;-

 

https://stargazerslo...comment=3125208

 

 I am thinking of getting a binoviewer for my own Lunt 50, and will try to go this route since it shortens the light path (however it still needs a x1.7 GPC screwed inside his MarkV binoviewer), requiring less in-travel. I think the reason you can do this is because the Lunt Blocking Filter / diagonal at the eyepiece end (at the bottom of the eyepiece holder) has a male T2 thread connection and goes into the female thread on the front of the Baader heavy Duty T2 Quick Changer that this guy uses on the nose of his binoviewer?

 

I notice that my own eyepiece holder on my Lunt 50's Blocking Filter / diagonal is a slightly slack holder for my eyepieces, and I would prefer a threaded connection.

 

However your approach does have the merit of only having 1.2x magnifying compared to the 1.7x magnification from a 1.7x GPC... so that would be good, but means I have to get hold of the 1.2 OCA and / or BlackNight binoviewer (I am in UK and would have to import them).

 

Regards,

 

Alistair G.


Edited by Live_Steam_Mad, 31 December 2017 - 02:17 AM.


#7 contrailmaker

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Posted 03 February 2018 - 07:17 PM

Ha binoviewing is great fun. I have the Denk setup for my PST. Much better than mono.

 

CM



#8 faackanders2

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Posted 03 February 2018 - 07:53 PM

Ha binoviewing is great fun. I have the Denk setup for my PST. Much better than mono.

 

CM

Not my experience, possibly due to 5mm blocking filter with my Conorado 40mm Solar Max wjich I almost exclusively use 20mm or 10mm possils recommended by Conorado.  I found it extremely difficult to get both eyes to get sun in view of denk II binoviewers and then having to pull the system in and out to get the powerswitches to focus (not enough focus travel with focuser), and tuning the H-Alpha filter just to exhausting; and I could see prominences better with less glass of single mono possils.

 

P.S.  But I love binoviewing ith my 17.5" f4.1 dob!


Edited by faackanders2, 03 February 2018 - 07:55 PM.



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