left :45 deg erect prism sold , right :The construction figure of my finder

There is one roof prism in this accessory .
This roof prism consume long focal path (about 90 mm) . So it is good to make a small size finder .
I used D=25mm f=100 mm objective lens from junk bino and no tube was needed .
 The eye piece ( konig type 25 mm 52 deg )is also from broken bino .
The mag power is 4 times and  the diameter of exit pupil is 6 mm .So the field of view of this finder is bright enough to see the cross without inner light .

Erected or inverted ?

It is said that ,
-Erect image finder is suitable to compare with the image by naked eyes and star map

-Up side down image finder is suitable to compare with the image of the parent telescope.

 I think small size view finder should be erect image type because it is mainly used to compare with the real star pattern in the sky .
 But many of the small view finders on the sold telescopes have up side down images . The main reason of it is " more cheap than erect type "

Inclined eye piece and site
 It is common sense to make it straight between the objective lens and eye piece of the view finder .
But this is not comfortable to look through when installed on the refractor and cassegrain type .
 There exist some 45 deg or 90 deg inclined finder but those are not good to catch the objects in its field of view .You may wonder the the use of those finder .
 To solve this dilemma I adopt the pointer like my ergonomics telescope series .
 This pointer works as a cap for the objective shown like below .

left : using style eye cap has a string and magic tape . Put it on the left side during using
right : not using time . To avoid dangerous lay from the sun and protect the cross , caution mark is attached on the cap pointer .

Setting
L bracket is used to set on the telescope.