|Black Amateur Telescope Making Materials|
|Black velvet paper flocking (not
Picture of flocking installed on 6" OTA. Note that a white dot is opposite the focuser to help determine the center of the focuser and the screws holding the focuser have not yet been painted flat black.
In addition to the contact cement shown above, DAP now sells in quarts and gallons, a low odor less flammable version that works quite well too.
27" wide, $1 /lineal foot +$12 shipping (Select the number of units (feet) you want). Shipping packages 27+ inches long has become quite expensive. If you don't mind the material folded, we can ship for $8. This usually leaves a crease, but a crease makes little difference in how much light is absorbed.
Unfolded flocking: ($1/foot + $12 shipping).
Folded flocking ($1/foot + $8 shipping).
Some people find that they get better contrast with a patch of black flocking across from their focuser in the tube. For this reason we offer
a 6"x6" patch and a 9"x12" patch.
6"x6" patch for opposite your focuser ($3 shipped)
9"x12 patch for larger scopes $5 (shipped)
which is and
excellent light absorber. It is suitable for lining
telescope tubes and
eyepiece tubes and any other surface that to eliminate reflections.
Unlike other black velvet available this material is not adhesive backed. One can spread the adhesive, put the flocking on it and move it into
the exact desired position before it dries. (you should test the adhesive you use with the tube material before doing the main job). I have
personally had trouble with the peel off backing stickinq to the wrong spot while I attempt to move them into place.
Excellent Light absorber
|Flat black self adhesive
(left) 9"x12" peel off back self adhesive sheet $1.50/sheet +$2 shipping
It is 2mm thick.
|More Information on Black
|After doing a few newtonians, I
have found that you can get 95+% of light blocked by
flocking the whole tube by doing the top 24 inches or so of
the tube, and maybe 12 inches down by the mirror. As
one can easily reach into the tube 24", this is a much
easier way to go. Of course if you try this, and you
feel it is not effective enough, you can put another strip
further in at a later date.
For metal and non porous (waxed sonotube), I find that Weldwood Contact cement works well for me, and remains flexible over time.
Be sure to do your own testing on whatever tube material you are using to be sure that this will work well for you. DCS cannot be responsible
for the decisions you make. Weldwood Contact cement is available at Ace Hardware for about $4 for a 3 oz bottle or less than $10 for a 32 oz
can. I usually keep a bottle with brush on hand, and refill from a can.
BE WARNED: this stuff is flammable and noxious. Use with good ventilation and be able to give it a few hours to dry some place where
you don't have to smell it. It has toluene in it along with other solvents that can seriously hurt you.
So It depends on what the tube is made of. It the tube is paper or cardboard(porous like the flocking) I would recommend doing a small
test gluing to be sure:
1) it sticks well
2) the glue can be applied thinly enough so it doesn't come through the flocking in gobs and dry that way,
3) your choice stands up to dew. I take the glued test and apply moisture to it (say with a cool humidier or little spritzer bottle) to see
how it reacts to dew.
I have put sample strips glued with Elmer's and Weldwood into a closed container with a tray of water and they held up for weeks in the
high humidity. Elmer's white glue did not remain flexible after drying, but it did hold quite well in all the tests.
Strategy for newtonians:
The way I find it easiest to install the flocking follows. This is by no means the only possible or best possible way, just the way I usually use.
First I measure the length and diameter of the tube to be done. I then measure how far up the tube the front surface of the main mirror is.
(I calculate things so that the flocking extends past this point but not to where the screws hold the mirror in place. The effective tube length is therefore the total tube length - the part I don't cover.
I then calculate the inside circumference of the tube (2*pi*radius or pi * diameter) I will cut pieces 27" long and one-third the
circumference wide. If the effective tube length is less than 54", I will then cut 3 more and shorten them to the effective tube length - 27".
If more than 54", a 3rd set needs to be cut. Remove mirrors, spider, focuser, etc for their protection. It may be worthwhile to spray paint the inside of the tube flat black at this point to cover any minor seams that the flocking will miss. (It may already be black if you are upgrading a tube)
I then put the glue on the backing for a single strip and install it in the tube starting at the front end. Lay the strip in the tube and roll it out with a piece of cardboard tubing or pvc pipe about 30" long. Once it appears well stuck, allow it to remain on the bottom of the tube while it dries. Rotate the tube 1/3 of a rotation and do the next strip. Don't worry about minor seam gaps. Once all the flocking is installed the light won't make it far enough down the tube to see it anyway. If you have a major gap, cut a piece of flocking to fill it and glue it on to cover. By doing this in thirds, gravity is always your friend, helping to hold the flocking in place while it dries. Let each section dry before moving on. Using the contact cement above I have been able to dislodge a strip and move it once when I had misplaced it. A second time can be difficult. If you find that edges stick up because you didn get glue to the edge, you have the opportunity to put a littlce contact cement there after the section dries, but before you put the next section on. Edges should be checked for adhesion at that point. The bottle with brush inside is convenient to touch up edges.