Flocking Material

[multiweb (Marc)]

http://www.fpi-protostar.com/flock.htm

Can this be sourced in Oz or equivalent product for flocking?
I want to do the inside of my C11. Thanks.

[gbeal]

Marc,
I bought a swag of this stuff direct from him a few years back, he (Brian IIRC) is a nice guy, so unless you are hell bent on buying locally, give him a try.
Gary

[Jone5y (Steve)]

I came across some flocking paint during an unrelated search for some woodworking products. Not sure if it would be suitable but here is a the link http://www.timbecon.com.au/products/flocking-439_0.aspx .

Hope that helps
Steve

[astronut (John)]

Marc,
I purchased a few metres of Spotlight adhesive backed matte black felt.
It works very well and is A LOT cheaper than the Protostar material.

[Paul Haese]

Spot light adhesive backed black felt. Great stuff, that is what I used on my C14.

[multiweb (Marc)]

Thanks for all the info guys. One more question. Is flocking or light baffles better? Is it worth doing?

[rmcpb (Rob)]

Both work but flocking is simpler and less likely to cause you problems if you don't quite get it right (baffles need to be different diameters along the tube).

However, when you spend the time to flock the tube make sure gaps around the mirror are baffled so the light cannot get in, but still allows air flow, and that the tube extends 1.5x the mirror diameter in front of the focuser (use a light baffle here) so off axis light does not get into your tube and reduce the contrast you are after.

Cheers

[multiweb (Marc)]

Originally Posted by rmcpb

Both work but flocking is simpler and less likely to cause you problems if you don't quite get it right (baffles need to be different diameters along the tube).

However, when you spend the time to flock the tube make sure gaps around the mirror are baffled so the light cannot get in, but still allows air flow, and that the tube extends 1.5x the mirror diameter in front of the focuser (use a light baffle here) so off axis light does not get into your tube and reduce the contrast you are after.

Cheers

Hi Rob, you lost me at : "and that the tube extends 1.5x the mirror diameter in front of the focuser (use a light baffle here) "

[rmcpb (Rob)]

I meant that if you are going to flock your tube in essence you are trying to improve the contrast of the image produced by the scope.

Off axis light (ambient light) is one of the worst enemies of contrast and we are trying to reduce this. So:

• We flock the tube with an extreme flat black material to reduce any reflections to the minimum possible so and off axis light that enters the front of the tube is not bounced off the side of the tube to the mirror.
• We baffle behind the mirror so light cannot sneak in around the mirror edges and start bouncing around but it still has to allow for air flow. This light we can eliminate so its best to do it, especially if we are in light polluted areas.
• We "extend" the OTA 1.5x the mirror diameter in front of the focuser. By extending the tube we stop off axis light from directly entering the focuser and reducing contrast. If you get light in there it bounces around in your eyepiece and you end up with a really washed out image. Why 1.5x the mirror diameter? Its generally accepted that this length will stop the problem, any less could allow some ambient light into the focuser. But more is not necessarially better as it adds weight to the front end of the scope and can get into the light path and reduce the light gathering capabilities of your scope.

Does all that waffle answer your question?

Cheers

[Dennis]

Originally Posted by multiweb

Hi Rob, you lost me at : "and that the tube extends 1.5x the mirror diameter in front of the focuser (use a light baffle here) "

Originally Posted by rmcpb

>snip
We "extend" the OTA 1.5x the mirror diameter in front of the focuser. By extending the tube we stop off axis light from directly entering the focuser and reducing contrast. If you get light in there it bounces around in your eyepiece and you end up with a really washed out image. Why 1.5x the mirror diameter? Its generally accepted that this length will stop the problem, any less could allow some ambient light into the focuser. But more is not necessarially better as it adds weight to the front end of the scope and can get into the light path and reduce the light gathering capabilities of your scope.
Cheers

Mixed messages? One is talking SCT and one is talking Newtonian. Eyepiece in mirror cell at bottom of OTA vs. eyepiece at side near top of tube.

Cheers

Dennis

[peter_4059 (Peter)]

Spotlight black felt worked a treat for me

[ausastronomer (John Bambury)]

Originally Posted by rmcpb

(baffles need to be different diameters along the tube).

Cheers

Rob,

That's not totally correct.

If you want to be totally anal about it you can certainly size the aperture of each baffle to be just larger than the diameter of the light cone at each baffle point. However, the main objective of anular baffles is to reduce internally reflected light by breaking down the "angles of incidence" along the tube periphery. A few annular baffles appropriately placed and sized to the maximum aperture of the light cone with a little clearance effectively achieves this. I have a fully flocked tube as well as 3 annular baffles in my 10" tubed newtonian, one either side of the focuser drawtube and one just above the primary mirror and they work beautifully. The scope gives "refractor like" views. The spotlight self adhesive black felt works beautifully as a flocking material. Warning: Cut the strips before you peel the backing off.

Cheers,
John B

[multiweb (Marc)]

Originally Posted by Dennis

Mixed messages? One is talking SCT and one is talking Newtonian. Eyepiece in mirror cell at bottom of OTA vs. eyepiece at side near top of tube.

That's what I thought Yeah the C11 is a SCT. I don't have to worry about the focuser

[multiweb (Marc)]

Originally Posted by rmcpb

Does all that waffle answer your question?

Cheers

I does now Rob. I'll apply these tips to my 5" newtonian. Thanks heaps for the detailed explanation.

[multiweb (Marc)]

Originally Posted by ausastronomer

Warning: Cut the strips before you peel the backing off.

Thanks John. Been there done that
What material did you use to do your baffles on each side of the focuser? Standard "foam" material or similar? Got no idea what they can be made off.

[astro_nutt]

Hi everyone!..
I used some thick black paper from the local newsagent to line the tube of my 10" dob with good results..although I didn't glue it directly to the tube rather to the paper itself!
Cheers!

[rmcpb (Rob)]

Originally Posted by Dennis

Mixed messages? One is talking SCT and one is talking Newtonian. Eyepiece in mirror cell at bottom of OTA vs. eyepiece at side near top of tube.

Oops. Need to read the post a bit closer even if it is on the bosses time.

However, a light/dew shield would help any scope in a light polluted area so all is not lost.

Cheers

[ausastronomer (John Bambury)]

Originally Posted by multiweb

That's what I thought Yeah the C11 is a SCT. I don't have to worry about the focuser

I got confused as well, probably because I was replying to Rob's post.

Nope, you don't need to worry about the focuser. Just use the Spotlight adhesive backed felt and flock the tube.

Cheers,
John B

[Glenhuon (Bill)]

Originally Posted by Paul Haese

Spot light adhesive backed black felt. Great stuff, that is what I used on my C14.

Thanks for the tip Paul , got enough to do both my newt and 102 refractor for under $30.

Bill

[Glenhuon (Bill)]

After doing the 150mm reflector and 80mm refractor with the Spotight stuff and seeing the improvement, just finished doing the 102 refractor as well. Works a treat.

Bill