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Modifying an astro telescope ring for use as SL lens collar


dkCambridgeshire
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Yesterday when using the SL 24-90mm lens with recently acquired Polaroid and Canon 77mm diameter achromatic close-up lenses  ...    http://www.l-camera-forum.com/topic/262292-sl-macro-adapters/?p=3080877   … I found the whole set-up rather too front heavy and unbalanced for efficient close-up composition. Thus today considered ordering the latest £139 Novoflex ASTAL SL tripod collar - but it's not yet available in the UK.

 

In my astro telescope 'bits box' I have a pair of 90mm internal diameter, telescope / guide 'scope mounting rings bought secondhand for £5 in a WEX Norwich 'SALE'. The SL 24-90mm lens is approx. 85mm diameter - thus the telescope ring fits over the SL lens' rear but with 2.5mm clearance. Fitting a 2.5mm thickness shim will take up the clearance. The 'scope rings have regular ¼" tripod screw threads

 

 

To make the 2.5mm (ish) shim I cut a strip of Daler art card and covered both sides with strips of self adhesive, black, 'VELOURSFOLIE' ( a self adhesive matt black velvet fabric used for flocking / light baffling telescope tube interiors) . Three strips of Velour stuck onto the card were sufficient to provide the required 2.5mm (ish) thickness. The soft velour is 'kind' and will not scratch the SL lens .

 

 

 

Fitting the trimmed shim into the mount/collar

 

 

 

 

The finished shimmed collar mount on the SL lens 

 

 

Finished collar supporting lens and camera 

 

 

The modified 'scope mount is secure and works fine; when slightly loosened the lens/camera combination can be turned easily through 360º;

 

 

 

Collar mounted onto ball head via regular ¼" tripod screw thread. 

 

 

 

Rear view of lens mounted on an ancient Benbo ball head. The Benbo head is not really large enough / smooth enough for efficient close-up photography composition - but was convenient to use it this afternoon. 

 

The shim's velour covering compresses when the clamping screw tightens the collar around the lens - thus no risk of being over-tightened 

 

Time to construct approx. 45 minutes. 

 

Total cost less than £10 . 

 

Now unlikely I'll need to buy the £139 Novoflex tripod collar.

 

In practice I will be using a larger Arca Swiss ball head plus a Novoflex Castel focusing rack . 

 

 

Best wishes

 

dunk

 

EDIT: If anyone wishes to construct something similar it's at your own risk!  If made a too tight fit, the ring might compress the rear lens group. The golden rule with telescope mounts, especially SCT OTAs is, " do not  over-tighten the 'scope rings" 

Edited by dkCambridgeshire
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