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NEW! Sky-Watcher EvoGuide 50mm ED GuideScope


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Shortest optical path is with a 90° 1.25" prism diagonal.

- Celestron 1.25" prism diagonal (it comes with SCTs)

- Takahashi 1.25" prism diagonal

- Baader T2 prism diagonal

- Vixen 1.25" prism diagonal

Optical lenght of all of these should be around 60mm. They provides an upright but mirrored image. An erecting prism uses a totally different optical layout; it's generally a 45° diagonal and provides a completely erected (correct orientation) image.

Edited by Rick_It
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For visual use, straight through, I have found a 15mm spacer works great.  This is with a televue 32mm plossl, or 19mm panoptic.  Inevitably, the skies have been obscured since I got all the bits.

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22 hours ago, Oldfort said:

For visual use, straight through, I have found a 15mm spacer works great.

That's the same as my findings using it straight through with the rear section attached. Though I don't have a spacer so was testing using hand held eyepiece. I'll have to rumage around to see if I can find something I can use.

Something like this @Oldfort do you think please? Link here

Edited by happy-kat
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4 hours ago, happy-kat said:

That's the same as my findings using it straight through with the rear section attached. Though I don't have a spacer so was testing using hand held eyepiece. I'll have to rumage around to see if I can find something I can use.

Something like this @Oldfort do you think please? Link here

Yes, that's the one I have used.  It weighs next to nothing.

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I received my ED50 today and tested it with a Baader 45 degree Amici Prism (which I think is identical to the William Optics) and a TV 32mm Plossl and it would not reach focus.

It would be good to know of a prism or diagonal that works with this little scope.

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Quote

Baader 45 degree Amici Prism

(...)

That's quite a few diagonals tested now with no luck

If I have not miss something, anyone has tried the ED50 with a 90° 1.25 prism diagonal. Those are the diagonals with the shortest optical path. Amici prisms have a very long optical path.

To be clear, the Celestron prism diagonal which comes with all SCTs is a very common example of a 90° 1.25 prism diagonal. Baader T2 prism is another example.

A barlow should also extract focus a little bit.

Edited by Rick_It
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With the diagonals I own with the extension removed (39mm) there is still not enough back distance with the focuser fully wound in (focuser has 20mm of travel to fully wound out). Rick_it  suggests a few other diagonal types to try but I don't have those.

I don't have the prism diagonals suggested by Rick_it to test with and obviously neither does DRT. So still unanswered whether there is any diagonal that will.

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32 minutes ago, happy-kat said:

With the diagonals I own with the extension removed (39mm) there is still not enough back distance with the focuser fully wound in (focuser has 20mm of travel to fully wound out). Rick_it  suggests a few other diagonal types to try but I don't have those.

I don't have the prism diagonals suggested by Rick_it to test with and obviously neither does DRT. So still unanswered whether there is any diagonal that will.

I'm trying to get a hold of a cheap prism to give it a go. If it works I might order a Tak or Baader equivalent but don't want to do that and find that it doesn't work.

What was the configuration that worked for you when you said you could focus on leaves?

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Back piece removed and focuser fully wound in

The Orion erect image diagonal with the 25mm sw standard eyepiece was really close watching the ant brush it's teeth on the lawn being stood on.

The unknown brand star diagonal with 25mm eyepiece focused on the hedge about 30+ feet away.

In my image here the unknown diagonal is the one on the far left.

15255437562021.jpg

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I've just managed to modify (i.e. butchered!) a cheap 90 degree mirror diagonal to reduce the light path by around 10mm and it now reaches focus on terrestrial objects. There is still around 8mm of inward focus available to try to reach focus on infinity but can't test that until this evening.

Whilst this isn't a long term solution it at least convinces me that a short light path diagonal or prism will work :grin: 

Here is what I did to the diagonal...

 

1. Cut out the internal lugs that set the position of the mirror

IMG_0950.thumb.jpg.920a55aaa128c2d0b759d80588e45ea6.jpg

 

2. Raise the height of the mirror on the base plate using a sponge pad

IMG_0951.jpg.5786821de814ffca765a4d4eec4af6d3.jpg

IMG_0952.jpg.318940444038d188ddd3b05df1c61e04.jpg

 

3. Cut half the length of the eyepiece holder with a hacksaw and tap a new hole for the retaining screw

IMG_0953.jpg.db15dc00fb89bda0b862bc6cc27819ff.jpg

 

4. Hey presto! A cute looking wide field scope that actually reaches focus :grin: 

IMG_0956.jpg.462d37575785e42d8f4dd1aee251e8be.jpg

 

 

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1 hour ago, happy-kat said:

Looking good. I guess that's about the same length as my unknown star diagonal. 

 

It is now :grin:

I’ve just bought a Meade prism diagonal from a member here so will report back on that later this week. 

 

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