STEP BY STEP

Sky at Night Magazine - - HOW TO -

STEP 1

A card tem­plate is use­ful to test that you’ve mea­sured cor­rectly. Draw around the tube to get a cir­cle, then care­fully mea­sure the bay­o­net con­nec­tor of the right-an­gled fin­der and draw its shape in the cen­tre of the cir­cle you’ve drawn.

STEP 3

Care­fully cut out the aper­ture in the end of the tube, en­sur­ing you fol­low any safety pre­cau­tions rec­om­mended by the tool’s man­u­fac­turer. Re­mem­ber – be­cause you drew in­side the tem­plate aper­ture, you will need to cut out­side of the marked lines.

STEP 5

If you used a film can, cut it to 25mm long and re­in­force the cut edge with in­su­lat­ing tape. Mate the tube to the fin­der and ro­tate it through 90°. Tighten the lock­ing ring on the fin­der un­til the tube will no longer ro­tate.

STEP 2

Cut out the tem­plate and make sure it fits the fin­der. If it does then – en­sur­ing the tem­plate is prop­erly po­si­tioned on the tube end – draw around the aper­ture with a per­ma­nent fine-point pen (non-per­ma­nent marks may not sur­vive the next step).

STEP 4

Use a fine file to smooth any rough edges and ‘tweak’ the shape of the aper­ture. Ex­per­i­ment to de­ter­mine the ap­pro­pri­ate amount of loop tape to give a snug fit to the eye­piece of the po­larscope. Film can­is­ters usu­ally need less tape than end-caps do.

STEP 6

Fit the fin­der to the po­larscope and en­sure that the retic­ule is vis­i­ble in the cen­tre of the field of view. If it isn’t, this is usu­ally be­cause it is tilt­ing slightly, so you will need to ad­just the amount of loop tape in­side the tube.

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