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Connecting Baader T2 Prism to Takahashi FC76DCU?


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This afternoon I purchased a Baader T2 Zeiss prism to try out with my FC76DCU & FC100DC scopes. I am keen to see how it compares optically against the Tak diagonal I currently use, and am particularly keen to see how much easier the Clicklock system is to use (especially with EP's that have undercuts). I just purchased the Baader prism alone today (no adaptors etc. yet).

All of my EPs are 1.25", and I don't have any plans to get 2" EPs in the near future, so initially I was thinking of just getting the 1.25" T2 nosepiece (to fit on the scope side of the Baader prism), and a 1.25" clicklock adaptor to go on the EP side.

However, I am wondering if there is merit in using a 2" clicklock on the scope side of the prism? Even though I will still be using the 1.25" clicklock adaptor on the EP side?

Below is the current setup on the rear of my FC76DCU. Sometimes, I rotate the diagonal from the vertical position (for more comfortable viewing when seated), and quite often, when I do this I end up loosening one or more of the threaded adaptors currently on the scope. So, I am thinking that the larger diameters offered by a 2" clicklock adaptor on the scope side, might better resist the rotation forces when trying to adjust and position the diagonal from the vertical? Maybe I am wrong about this and should just stick with 1.25" nosepiece on scope side, and 1.25" clicklock on EP side to save cost?

If I went for the 2" on the scope side, I assume it would be 2" clicklock M56 adaptor (Baader Part No 2956255), and 2" nosepiece  (Baader Part No 2408150)? And I assume the 2" clicklock would screw directly onto the blue connector below, with the red, green & yellow connectors taken out of the system? Or would the blue connector go as well?

Any thoughts or comments welcome and appreciated.

Thanks,

Chris

image.png.2bcd064573448bb56bf62680d0c4c3e8.png

 

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I use the Baader T2 Zeiss prism with my FC100-DL. This is the back end of the scope. This arrangement seems to suit all my various eyepieces. I use 1.25 inch eyepieces most of the time with this scope. There is a T2 15mm extension tube between the topside of the prism and the 1.25 inch click lock adapter which is not obvious in this photo:

takFTstee2.jpg.5db38cfce332e694266fde76a6b42861.jpg

Oops ! - I've just noticed that your Taks don't have the same focuser that mine does so the above might not be too much help. Apologies for missing that.

Edited by John
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If you want a really solid connection to the scope,  a t2 to 2" adapter is good, and if you want to be able to swing the eyepiece to the side easily a heavy duty t2 quick changer and bayonet would do that.

I don't really use 1.25" into the scope these days, only 2" or 2" to t2 for the solidity.

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I used a FC100DC for five years, and although I would use the visual back configuration that you're using, I also used the 2" back that with the D.C. needed to be bought separately. Along with the 2" Tak adapter I'd also use a SW low profile 2" to 1.25" reducer which enabled me to use my Tak prism. This got rid of the screw in fittings that unwind, and gave me a visual back that would hold my prism and binoviewer at any angle without issue.   I now have a FC100DZ and use both the Tak prism and the Baader Zeiss BBHS prism with a 2" nose. The 2" Tak adapter holds the 2" nose of the Baader prism, and the 2" to 1.25" reducer I use with the Tak prism solidly and at any angle.

The pic's below show a close up of the DZ 2" visual back and Baader prism, and one with the Binoviewer with Tak prism at the usual angled position I often observe from.   (Tak offer a standard 2" v back as seen here, but also a shorter version that will permit more inward focus). 

2023-03-1216_40_10.jpg.438b9f75413f6baed8ca918d4e6ec1cb.jpgIMG_20230125_170945.thumb.jpg.4011a03a13c9d3386c3cb8f463969da5.jpg

 

Edited by mikeDnight
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Bought my Tak FS-60Q second hand and it came with the same 1.25" visual back as yours and also a Tak 2" as mentioned by @mikeDnight 

I tend to use the 2" VB with my Baader prism diagonal and 2" nose piece #2408150.

Not 100% sure about the click-lock but asked FLO a similar question about my FC-100DL and they suggested click-lock #2956268 which would screw directly onto the focuser tube, no original adapter required. 

Your focuser tube is smaller than the FC-100DL with an outside thread (55mm OD?) so I think the click-lock #2956255 you mentioned might need another adapter ring to fit, I would contact FLO.

Couple of pics below of my Tak FS-60 & Baader prism diagonal with 2" nosepiece.

 

IMG_4724.jpeg

IMG_4725.jpeg

Edited by jock1958
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11 hours ago, Paz said:

If you want a really solid connection to the scope,  a t2 to 2" adapter is good, and if you want to be able to swing the eyepiece to the side easily a heavy duty t2 quick changer and bayonet would do that.

I don't really use 1.25" into the scope these days, only 2" or 2" to t2 for the solidity.

Snap - this is what I do on all my scopes, with T2-2” adapters in the focuser, T2 Baader diagonals and heavy duty changers, and either 1.25” or 2” clicklock EP holders. They make undercuts irrelevant, and the whole system is extremely strong (and flexible, if you need to rotate a binoviewer or eyepiece for example). Adding T2 spacers is easy to vary barlow powers, and it’s surprising how few 2” eyepieces vignette with a T2 diagonal. Finally, it’s light and offers a short light path. 

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I have the 76DCU and have the M56i clicklock scope side into a clicklock 1.25” reducer. The Tak prism light path was too short for my EPs though (XWs) so I needed to extend the light path with a Moreblue camera rotator. I think the Baader prism’s light path is slightly longer than the Tak’s though.

 

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Thanks very much everyone. All of the replies above provide useful ideas.

These replies have given me reassurance that my thoughts about using 2" on the scope side of the prism is the correct way to go. Yesterday afternoon I ordered a 2" Baader Clicklock, a 2" nose piece, and a 1.25" clicklock for the EP side of the prism. I hadn't even thought about the advantage of 2" on the scope side for better rigidity/clamping when binoviewing (which is something I might be keen on trying out in the future).

Thanks @IB20 for your linked post above. I was guessing yesterday that after removing all of the threaded Tak adaptors and replacing with the single Baader 2" M56 clicklock, that my light path might be too short when using eyepieces in the prism. I am assuming I might need a bit of an extension to return the light path length back to what it is now. It might be that I try leaving the first threaded Tak coupling (arrowed blue in my post above), and mount the 2" clicklock onto this? This appears to be one solution indicated by Malcom in the post linked above. Or I might consider the More Blue Camera rotator that you are using @IB20. I guess Baader T2 extensions might also be something that could provide a cheap way of adjusting the length.

The clicklock parts are due to arrive next Tuesday. So I will see how I get on with my EPs and assess how much (if any) focal extensions are required. Will post back once I have tested.

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