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51 Redcat with Standard Astronomy Diagonals!

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#1 Sarkikos

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Posted 17 August 2022 - 07:40 PM

Several years ago, I bought a 51 Redcat version 1.  I use it for visually only.  I don't do AP. 

 

It has excellent optics with a flat field.  But the only diagonal that will work with the 51 Redcat is the proprietary Amici diagonal.  I'd like to adapt the scope to accept a standard 1.25" mirror or prism diagonal.  Or even a standard Amici diagonal, if that's what I want.  How do I do this?

 

I'm not sure what threading the rear port has.  It isn't 48mm.  I've heard that it is 55mm or 56mm.  I can't find any specs on the threading online.  If it's out there, I haven't found it.  Williams Optics and their vendors talk about everything but the threading on the rear port.  ohmy.gif

 

I need a ring adapter with male "whatever-it-is" threading on one side and male T2 threading on the other.  I'd like to connect my Baader mirror or prism diagonals directly to the rear of the 51 Redcat.  The threading on both of these diagonals is T2. 

 

The 51 Redcat has a rotatable visual back and the scope can be rotated in the ring.  So no problem if the diagonal isn't lined up correctly when I connect it.

 

The 51 Redcat 1 included a 48mm adapter, but it is too long.  If I connect a diagonal to this adapter, eyepieces won't come to focus.  There is not enough back focus.  Yeah, an astrograph with not enough back focus for visual.  Don't they usually have too much?  That's my experience with Newt astrographs, anyway.  lol.gif

 

So does anyone know what threading is on the back of the 51 Redcat version 1?  What ring adapter can I use to connect a 1.25" diagonal which has female T2 threading?

 

Mike


Edited by Sarkikos, 17 August 2022 - 07:47 PM.


#2 Sarkikos

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Posted 17 August 2022 - 07:52 PM

I just did a search for "51 Redcat refractor threading."  The only relevant hit I got was this very thread that I started a few minutes ago!  lol.gif   No, it's not funny, not really.  frown.gif

 

:grin:

Mike


Edited by Sarkikos, 17 August 2022 - 07:53 PM.

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#3 bmcclana

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Posted 17 August 2022 - 09:13 PM

on the agenaastro page for the redcat v2, there is a diagram that shows 3 thread sizes on the rear, M48, M54 and M56 all x0.75mm

 

https://agenaastro.c...escope-red.html

 

i think the rotator is attached to the drawtube with the M56 internal thread. 

 

i dont know if or how different the v1 is...


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#4 Sarkikos

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Posted 17 August 2022 - 09:26 PM

on the agenaastro page for the redcat v2, there is a diagram that shows 3 thread sizes on the rear, M48, M54 and M56 all x0.75mm

 

https://agenaastro.c...escope-red.html

 

i think the rotator is attached to the drawtube with the M56 internal thread. 

 

i dont know if or how different the v1 is...

Thanks for the answer.  But the M54 and M56 threading to the right of the M48 threads are apparently on the tilt adjustor that is new on the 51 Redcat II.  These threads aren't on the 51 Redcat I.  

 

https://agenaastro.c...escope-red.html

 

The Redcat  I has the "what's-it" threading, and then a longer adapter ending with 48mm threading attaches to the "what's-it" threading.  The M54 and M56 aren't on the 51 Redcat 1.

 

If the 48mm adapter supplied with the 51 Redcat I were a ring adapter, then I could rig something up with a T2 diagonal.  But it isn't, so I can't.  Well, actually I can rig it up and I did, but then eyepieces won't come to focus.  I need a shorter connection between the rear of the 51 Redcat I and the diagonal.

 

I don't do AP, so I have no use for a tilt adjustor.  Though, if I did have the tilt adjustor, it might be short enough for eyepieces to come to focus in a standard T2 diagonal. 

 

But a regular ring adaptor would be ideal.  The shorter the adapter, the greater variety of eyepieces that could come to focus in the diagonal.

 

Mike

 

The attached thumbnail is for the 51 Redcat II.

Attached Thumbnails

  • L-RC51 II Back Focus.jpg

Edited by Sarkikos, 18 August 2022 - 07:23 AM.


#5 bmcclana

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Posted 17 August 2022 - 09:41 PM

I think it is highly likely that whatever thread it is it is an M??x0.75 thread.

 

Can you accurately measure the ID or OD of the threads where the visual diagonal attaches? the OD of the male threads should be fractionally smaller than the 'M' thread number.


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#6 Sarkikos

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Posted 17 August 2022 - 09:57 PM

I just now measured the ID of the threads to be 55mm with a digital caliper.  Of course, that depends on the accuracy of my measuring. 

 

My measurement matches, though, one of the measurements I mentioned in the Opening Post.  I'm not sure where I saw the 55 and 56mm measurements.  IIRC, here on CN.

 

Mike


Edited by Sarkikos, 17 August 2022 - 09:58 PM.


#7 Sarkikos

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Posted 17 August 2022 - 10:06 PM

I measured the male threads at the back of the WO AMICI diagonal.  They come close to 56mm (largest measurement was 55.9mm).

 

Mike


Edited by Sarkikos, 17 August 2022 - 10:18 PM.


#8 Sarkikos

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Posted 17 August 2022 - 10:07 PM

Here are pics of the visual back of the 51 Redcat I and the WO AMCI diagonal:

 

Mike

Attached Thumbnails

  • IMG_0454.jpg
  • IMG_0455.jpg


#9 Sarkikos

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Posted 17 August 2022 - 10:13 PM

Is there such a thing as a male 55mm or 56mm (x0.75) to male T2 ring adapter?   If so, should it be 55mm or 56mm?

 

Actually, shouldn't the male threading (on the diagonal) be slightly less than the female threading (on the visual back)?  :shrug:

 

Mike


Edited by Sarkikos, 17 August 2022 - 10:15 PM.


#10 Sarkikos

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Posted 17 August 2022 - 10:28 PM

Assuming 55mm is correct, then I need M55x0.75 male to M42x0.75 male ring adapter.  I think. 

 

Mike



#11 Sarkikos

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Posted 17 August 2022 - 10:31 PM

I see M55x0.75 male to M42x0.75 female ring adapter, but no M55x0.75 male to M42x0.75 male.  Maybe I'll need a female to male M42 ring, too.

 

Mike



#12 Sarkikos

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Posted 18 August 2022 - 07:22 AM

Yesterday evening, I submitted an email to William Optics requesting the thread size on the visual back of the 51 Redcat I.  (It's probably the same on the 51 Redcat II, if you remove the new tilt adjustor thingamaroo.)

 

If and when I receive an answer, I'll post it here.

 

Mike 


Edited by Sarkikos, 18 August 2022 - 07:23 AM.


#13 Sarkikos

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Posted 18 August 2022 - 07:37 AM

This morning I sent an email to rafcamera to see if they have the ring adaptor I need.

 

Mike



#14 Sarkikos

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Posted 18 August 2022 - 07:41 AM

Would this work?

 

M55x0.75 male to M42x1 male thread adapter

 

https://rafcamera.co...0-75m-to-m42x1m

 

Mike


Edited by Sarkikos, 18 August 2022 - 07:48 AM.


#15 Sarkikos

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Posted 18 August 2022 - 09:41 AM

Would this work?

 

M55x0.75 male to M42x1 male thread adapter

 

https://rafcamera.co...0-75m-to-m42x1m

 

Mike

 

Here is Rafael's answer:

 

Adapter to M42x1 (you asked about on the product page) will not work due to different pitch.  Please contact me as soon as you have a precise specification from the manufacturer, and we'll be able to make you the necessary adapter.  Thank you.

Is anyone else interested in this adapter?

 

Mike


Edited by Sarkikos, 18 August 2022 - 10:01 AM.


#16 Sarkikos

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Posted 18 August 2022 - 10:00 AM

The first message I sent to WO was directly through their website.  I just now sent an email to them at wo@williamoptics.com.

 

What is the threading size and pitch on the rear port of the 51 Redcat I?  I mean the female threading at the rear after you remove the 48mm adapter.  I have a 51 Redcat I and I want to connect a T2 diagonal to it with a ring adapter.  I can't find the threading size/pitch anywhere.

Mike

 

Update:  

 

I received this response late yesterday evening:

 

 

You have to use a special erecting prism with Redcat51, see the image below, it also shows how to attach it:
https://williamoptic...edcat-51-only-1
Regards,
Tim

bangbang.gif

 

Mike


Edited by Sarkikos, 19 August 2022 - 08:36 AM.


#17 Sarkikos

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Posted 18 August 2022 - 10:04 AM

I wonder how many are interested in a ring adapter to connect a T2 - or even a 48mm - diagonal directly to the rear port of the 51 Redcat?  (It should probably work the same for version I and II.)

 

I'm sure the number who bought either version 51 Redcat is pretty small.  The percentage of this small number who are interested in the 51 Redcat is probably much smaller.

 

But if there are others out there, let me know! grin.gif

 

I like these small Petzval refractors for visual only.  I have absolutely zero interest in any telescope for imaging!   AP is a good view ruined! lol.gif

 

Yeah, he said it!  coolnod.gif

 

Mike


Edited by Sarkikos, 18 August 2022 - 10:07 AM.


#18 bmcclana

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Posted 18 August 2022 - 11:06 AM

I measured the male threads at the back of the WO AMICI diagonal. They come close to 56mm (largest measurement was 55.9mm).

Mike


Since the male threads measure 55.9, it is almost assuredly a M56 size.

The ID of the opening will measure smaller because of the meshing of the threads. If it wasn’t smaller the threads wouldn’t overlap to screw in and make a connection.
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#19 PeteDavidsonTheFirst

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Posted 18 August 2022 - 11:47 AM


I'm sure the number who bought either version 51 Redcat is pretty small. The percentage of this small number who are interested in the 51 Redcat is probably much smaller.

But if there are others out there, let me know!

 

 

I think some NV users, myself included, would be interested in an NV-compatible 50mm scope for wide-field views.


Edited by PeteDavidsonTheFirst, 18 August 2022 - 11:50 AM.


#20 Sarkikos

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Posted 18 August 2022 - 11:57 AM

Since the male threads measure 55.9, it is almost assuredly a M56 size.

The ID of the opening will measure smaller because of the meshing of the threads. If it wasn’t smaller the threads wouldn’t overlap to screw in and make a connection.

I was thinking about ordering a set of step up / step down rings to check the threading.  This set has 55mm, but not 56mm. (No 42mm / T2 threads, either.)  I don't see sets with 56mm.  

 

Neewer 18 Pieces Metal Camera Lens Filter Ring Adapter Kit

 

https://www.amazon.c...GSD2Z498Y&psc=1

 

STEP-UP RING FILTER ADAPTER SET: 37-49, 49-52, 52-55, 55-58, 58-62, 62-67,67-72, 72-77, 77-82mm

STEP-DOWN RING FILTER ADAPTER SET: 49-37, 52-49, 55-52, 58-55, 62-58, 67-62, 72-67, 77-72, 82-77mm

 

Mike


Edited by Sarkikos, 18 August 2022 - 12:01 PM.


#21 fmendes

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Posted 18 August 2022 - 12:23 PM

The first message I sent to WO was directly through their website.  I just now sent an email to them at wo@williamoptics.com.

 

What is the threading size and pitch on the rear port of the 51 Redcat I?  I mean the female threading at the rear after you remove the 48mm adapter.  I have a 51 Redcat I and I want to connect a T2 diagonal to it with a ring adapter.  I can't find the threading size/pitch anywhere.

 

 

Take a pencil and rub on the thread. Then take a piece of paper and rub against the thread. The thread will mark the paper, then you can measure the pitch on the paper. If it all looks too small (my eyes are not as good as they used to be), scan the paper on the side of a ruler and see zoomed in on the computer. You'll find either 0.75mm or 1mm. Measure as many threads that you can, then divide the distance found by the number of threads.


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#22 fmendes

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Posted 18 August 2022 - 12:26 PM

I have here an old 2" diagonal. For the sake of it, will try to design and 3d print adapters for my Redcat II and a 1.25" eye piece. Won't use it much, but won't cost anything other than my time.


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#23 ad701xx

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Posted 18 August 2022 - 02:43 PM

Mike,

 

I posted a picture of my Spacecat with a 2" diagonal in a thread you started a few years ago. I can get the thread dimensions of the adapter I used when I get home tonight if you still need it.

 

See post #54:

 

https://www.cloudyni...sual/?p=9866836

 

 

 

 


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#24 ad701xx

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Posted 18 August 2022 - 06:33 PM

Ok, the thread size needed is M56x0.75.

 

 

I used this for my 2" Baader Maxbright and Celestron diagonals.

 

M48x0.75 male to M56x0.75 adapter:

 

https://agenaastro.c...apter-m-12.html

 

Baader SCT male to M48x0.75 female adapter:

 

https://agenaastro.c...-2-2454834.html

 

 

To go to a T2 diagonal the M48x0.75 male to M56x0.75 adapter coupled with a M48 female to T2 male adapter would work:

 

https://agenaastro.c...apter-t-06.html

 

Hopefully it would reach focus alright. It's also possible you may need an M48 or T2 spacer depending upon the focal positions of the eyepieces you are planning to use. The TV 55mm Plossl was able to reach focus with the 2 inch diagonals because it needs a lot of out focus.

 


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#25 Sarkikos

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Posted 18 August 2022 - 07:30 PM

I have here an old 2" diagonal. For the sake of it, will try to design and 3d print adapters for my Redcat II and a 1.25" eye piece. Won't use it much, but won't cost anything other than my time.

AFAIK, the 51 Redcat II includes a shorter adapter which ends in 48mm threading.  See the diagram in post #4. 

 

My 51 Redcat I came with a 48mm adapter, but it is too long to accommodate a diagonal and still have eyepieces come to focus.

 

But you might be able to connect the 48mm threads that are exposed on some diagonals when you remove the neck, with the 48mm threading on the 51 Redcat II.  A 48mm gender change ring could be required.  You might have a better chance of eyepieces coming to focus with that setup.

 

The basic problem with getting either 51 Redcat version to work with eyepieces in a diagonal, is that the scope does not have enough back focus. 

 

Is this the way most astrograph refractors are?  My experience with Newt astrographs is that they have too much back focus for visual.  To have eyepieces come to focus in a Newt astrograph, I've had to install a long extension tube at the focuser.  It does make it easier, though, to stack a filter wheel without having to use a Barlow or OCA.

 

Mike


Edited by Sarkikos, 18 August 2022 - 07:34 PM.



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