[ATM] Shroud v.s no shroud

[Tim Nott]

Hi again,

Thanks to the people who responded to my earlier post.

After various responses (and after trawling through the archives) that 
agreed that a shroud would make little or no difference to an already 
baffled scope at a dark site, I've decided to go with the simple plastic 
shield  and velcro option (similar to Jim Miller) to protect the primary 
from unwanted objects. I also couldn't be bothered making the shroud as it 
would be more complex than usual due to the nature of the scope's design.

No direct stray light makes it into the eyepiece of my scope due to the 
baffles (all that is visible through the focuser is the baffles, primary & 
secondary plus holder) but, doing the flashlight test, I noticed significant 
glaring when an assistant shone a flashlight at the top end.  This, I 
discovered, was mainly due to secondary reflections coming off the diagonal 
holder which - even though it was painted flat black - was many more times 
reflective than the Protostar flock that I have on the baffles.  I have 
since flocked the secondary holder (as well as the lower part of the focuser 
drawtube) and this has reduced the amount of this reflected light greatly.

To experiment with, I've also made up some smaller baffles (each designed 
for a particular eyepiece) that I can press-fit inside the focuser drawtube 
to further restrict the surfaces other than the mirrors that are seen by the 
eyepiece.  I'll probably leave it at that.  Every surface (including flock) 
is going to reflect some light, but surely at some stage you reach the law 
of diminishing returns, where further efforts in blocking stray light 
results in an effect negligible to the human eye.  I hope I've reached that 
point and don't end up building a "flocked observatory with a baffled slit".

By the way, thanks Mel for making your tridob design available for others to 
copy (steal) and modify on the internet.  It works fabulously well!

Tim