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Focal reducer with binotron 27

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#1 V-Rock

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Posted 09 January 2019 - 10:52 AM

Question: I have a c11 with moonlight focused, is it possible to use my Meade 4000 focal reducer on the c11 and reach focus with B27 and power switch ? I can screw the focal reducer directly to the visual back or I could screw it inside of the Moonlite focuser. Anybody try this?

#2 Jeff B

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Posted 10 January 2019 - 11:13 AM

Maybe, maybe not.  The meade's focal reduction is calculated for use without a bino-viewer's extra light path taken into consideration.  Placing it directly on the visual back will more than likely result in way more reduction than originally intended.  Even if you could get to focus, you have heavy vignetting of the aperture and the field of view edges.

 

Best focal reduction solution is the Denk's which places the reducer in the power switch or, in some of the older, sans switch versions, at the top of the nosepiece.

 

Jeff


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#3 V-Rock

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Posted 10 January 2019 - 07:06 PM

Thanks Jeff B, I'll experiment tomorrow night.with the C11 and new binotron 27's with pwer switch. Supposed to be real clear here in L.I. It will be interesting to see what happens, only takes a minute to set up.

#4 Bob4BVM

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Posted 13 January 2019 - 03:25 PM

Interesting idea !

I will try that tonight with my 8"SCT & BVer.

CS
Bob



#5 Eddgie

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Posted 13 January 2019 - 11:05 PM

Interesting idea !

I will try that tonight with my 8"SCT & BVer.

CS
Bob

If you can even reach focus, expect over an inch and a half of aperture loss with the C8. That does not mean you should not do it, it just means that it is a huge compromise.  You may not be able to reach focus in the C8.

 

The C11 might reach focus, but the field will be vignetted, and spherical aberration will be well over half a wave.  (Will be over half a wave in the C11 too, and worse if using a 2" diagonal. Half a wave is not going to stop the scope from working, but it will be devastating for contrast.   

 

That does not mean you can't or should not do it, it just means that physics penalizes you in some way.  No free lunch. 



#6 V-Rock

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Posted 14 January 2019 - 06:31 AM

Thanks ed,
I was out with 6"f/12 and B27 last night 1st time!!! Moon looked great! Tonight will experiment with C11 !
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#7 Jeff B

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Posted 14 January 2019 - 11:13 AM

Thanks ed,
I was out with 6"f/12 and B27 last night 1st time!!! Moon looked great! Tonight will experiment with C11 !

Excellent.  Is your Istar "bino-friendly"?    

 

And why not? grin.gif

 

Jeff



#8 V-Rock

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Posted 14 January 2019 - 11:55 AM

Hi Jeff,
No (1800mm focal length) but last night could almost get whole moon in with 23 mm 52°eyepieces (Almost).Thats why I need to pick up something like 26mm 62/68° but otherwise a pretty amazing view.

#9 V-Rock

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Posted 14 January 2019 - 11:56 AM

Hi Jeff,
No (1800mm focal length) but last night could almost get whole moon in with 23 mm 52°eyepieces (Almost).Thats why I need to pick up something like 26mm 62/68° but otherwise a pretty amazing view.

#10 Jeff B

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Posted 14 January 2019 - 08:33 PM

Ah, you had a "bino-answer" grin.gif

 

That means you really want one.  

 

When you reach focus with your favorite 1.25" format eyepiece, how much focuser in-travel is left?

 

Jeff



#11 faackanders2

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Posted 14 January 2019 - 11:15 PM

Question: I have a c11 with moonlight focused, is it possible to use my Meade 4000 focal reducer on the c11 and reach focus with B27 and power switch ? I can screw the focal reducer directly to the visual back or I could screw it inside of the Moonlite focuser. Anybody try this?

Denkmeier used to have a "Star Sweeper" focal reducer OCS for SCT scopes.  I never had a SCT so I have never seen how it worked.  You could ask Russ if no users respond.

 

P.S.  From what I read on cloudy nights most SCT owners liked to go native (No OCS).



#12 Jeff B

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Posted 15 January 2019 - 10:11 AM

Denkmeier used to have a "Star Sweeper" focal reducer OCS for SCT scopes.  I never had a SCT so I have never seen how it worked.  You could ask Russ if no users respond.

 

P.S.  From what I read on cloudy nights most SCT owners liked to go native (No OCS).

Well, there were a couple of versions of the stand alone SCT Star Sweeper.  One looks just like a typical 2" OCS/multiplier and screws into the bottom of the 2" nosepiece.  I'm not sure what its reduction factor is.

 

The other version is smaller in diameter and nested in the  2" or 1.25" nosepieces, at the top in the feature that threads into the bino-viewer body. Again, I'm not sure the reduction factor but I have a feeling it's the same as the reducer that's in a power switch arm.  With this version, you could simply screw an OCS/multiplier into the bottom of the nosepiece to achieve magnification as well.

 

Jeff



#13 Bob4BVM

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Posted 16 January 2019 - 12:22 AM

Interesting idea !

I will try that tonight with my 8"SCT & BVer.

CS
Bob

Well I tried it but no joy, none of the threads adapted to my 2" vis. back tube, which I needed to mount the 2" BVer nosepiece into.

I could turn out an adapter to go from the FR's SCT threads to 2" ID, but I am too busy with other projects right now. The big one will kind of make my BVers obsolete I guess...

CS

Bob




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