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Choice of Finderscope.

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#1 Princess Leah

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Posted 05 October 2024 - 05:31 PM

Was musing how Skywatcher produce a 9x50 finder that is not correct image.

 

https://www.rotherva...nderscopes.html

 

Advantages would be it matches the diagonals most of us use, but also the optics should be superior with higher transmission.

This is because no Amici prism would be required.

 

isadvantage would be difficulty reading star charts etc.

 

Anyone experienced the pros and cons?


Edited by Princess Leah, 05 October 2024 - 05:31 PM.


#2 Shorty Barlow

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Posted 05 October 2024 - 06:13 PM

AFAIK you can get RA finders with conventional and Amici prisms. I tend to use Baader Amici prisms primarily just for lunar viewing.

 

IPUMKTql.jpg

 

To Amici or not Amici is your personal choice. Many people prefer standard prisms on their finders as it is more similar to what they view through the eyepiece. Unless you're using a Newtonian of course. 


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#3 BQ Octantis

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Posted 05 October 2024 - 07:13 PM

Once I went right angle, I never went back. Yes, with the conventional prism things are flipped, just like through the EP in the diagonal on the scope. But on the flip side, I haven't knelt before my scope or had to bend my neck at a right angle in almost a decade…

 

BQ


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#4 Jon Isaacs

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Posted 05 October 2024 - 07:42 PM

My 2 cents:

 

I prefer RACI finders to RA finders.

 

RA finders are OK on Alt-AZ mounts if mounted vertically, the image is correct top-bottom but reversed left right. 

 

If it's mounted at an angle as it often is on a GEM or a Dob, then the field is flipped at an angle which is difficult to interpret.

 

For that reason, I much prefer RACI finders, they're always correctly oriented.

 

Transmission differences are minimal and more dependent on the quality of the finder. I prefer finders with 1.25 focusers so I can use eyepieces of my choice and rotate them so the cross hairs are aligned Alt-AZ.

 

Jon


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#5 Princess Leah

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Posted 06 October 2024 - 04:13 AM

Very good point Jon.

I've always used RACIs, so didn't really appreciate all the benefits.

 

I've just realised the 90 Amici path is only one extra direction change (at low mag phase coatings are not requiired).

It's the 45 degrees prisms that have a more convoluted path. 

 

 

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#6 Princess Leah

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Posted 06 October 2024 - 08:11 AM

Anyone know what kind of prism is in a correct image straight through finderscope?



#7 triplemon

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Posted 06 October 2024 - 11:39 PM

Most likely https://en.wikipedia...dt–Pechan_prism


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#8 Princess Leah

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Posted 07 October 2024 - 02:46 AM

Thanks - another roof type prism!



#9 UnityLover

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Posted 07 October 2024 - 08:15 AM

Was musing how Skywatcher produce a 9x50 finder that is not correct image.

 

https://www.rotherva...nderscopes.html

 

Advantages would be it matches the diagonals most of us use, but also the optics should be superior with higher transmission.

This is because no Amici prism would be required.

 

isadvantage would be difficulty reading star charts etc.

 

Anyone experienced the pros and cons?

The incorrect image, would the image be upside down? 


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#10 Princess Leah

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Posted 07 October 2024 - 11:04 AM

The incorrect image, would the image be upside down? 

I don't think so...



#11 Bill Barlow

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Posted 07 October 2024 - 11:30 AM

I star hop to my targets using alt-az mounts and using star charts.  So I only use RACI 50mm finder scopes.  I once had a Meade reverse image finder but quickly ditched that as it was hard to use.

 

Bill


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#12 rjacks

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Posted 07 October 2024 - 12:21 PM

RACI. I have one straight through finder scope, and I hate it. I'm always grubbing around on my knees to look through it. 

 

Or Telrad.



#13 25585

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Posted 07 October 2024 - 12:38 PM

Was musing how Skywatcher produce a 9x50 finder that is not correct image.

 

https://www.rotherva...nderscopes.html

 

Advantages would be it matches the diagonals most of us use, but also the optics should be superior with higher transmission.

This is because no Amici prism would be required.

 

isadvantage would be difficulty reading star charts etc.

 

Anyone experienced the pros and cons?

I go the other way and use an Amici on my main refractors. Its the Baader Astro. or APM, both good quality.

 

I prefer correct image finders as I move to them after my Telrad, both make orientation easier using star atlases.




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