DIY Light/Dew shield

[phoobar]

Hi

is there a maximum length from the end of my telescope that I should not exceed when attaching a light shield?

I intend to use a black yoga mat that are sold by aldi, and was just wondering why I dont see many that are longer than about 12".

Cheers

[Bizibilder]

They are usually made to "overhang" by about 1.5x the aparture of the tube although there is no set rule for this.  With yoga mat the overall length is often governed by the ability of the mat to hold its shape and not start to flop all over the place!  You can get round this if you need to by gluing some thin strips of spare mat longitudinally onto the outside of the shield to stiffen it a bit.

[phoobar]

Thank you very much Bizi