Gave my scope a good Flocking!

Posted by XTSee on 26th September , 2008

Yesterday evening I got home from work and took the dog out for his walk. It was a lovely clear night and the stars were nice and bright, so I was feeling quite excited about the prospect of some decent star gazing (wifey is away tonight). Got back home and immediately took my XT10i telescope outside to start cooling down. Next I went in, did the dogs supper and prepared myself some tea, and ate it quickly so I could get back out for some observing. I was about 20 minutes in all. Went back outside and couldn’t believe it. Once again those blasted clouds had moved in to spoil the fun. Damn!

Oh well. Plan B. At the weekend I had ordered some Protostar black velvet flocking material to line the inside of the scope to reduce reflections from ambient light bouncing off the insides, and so increasing the contrast of the view. And it had just been delivered that morning.

So I set about carefully dismantling the scope to remove the primary and secondary mirrors, and the finder scopes, so I could install strips of the flocking material easily. The job took about 2.5 hours, by which time it was too late to put everything back together.

Tonight I decided to finish the job by cleaning both primary and secondary mirrors, and adding a touch of black matt paint to various bolts inside that were shiny, and apply some to the edges and back face of the secondary mirror. I carefully followed instructions for the best method to clean the mirrors, so as not to scratch them or remove their aluminised protective coating (I’ve had the scope almost a year now and a fair amount of dust has gathered on the primary).

Finally I re-assembled everything and re-collimated the mirrors as precisely as I could. When all was done I took the scope outside to see what improvement the flocking had given. It’s been a fairly clear night, with the occasional cloud passing over. The Pleiades were visible so I lined up on them and checked it out.

Now my rear garden has a white light (mercury) street lamp to the North side, and I have always noticed when pointing the scope to the North or East, that the light entering the end of the scope tube (unless I get our large patio table umbrella out to shield the light) always gives a lightening or greyness to the view.  But with the new flocking there is a considerable difference, with a very much darker view, which does indeed give better contrast. Certainly looking down into the tube from the top it looks very dark inside.

Nice one. As usual I have taken some photos of the flocking work, and will create a new page in my main web site describing how it was done, and where I got the material from. Watch this Space.

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3 Responses to “Gave my scope a good Flocking!”

  1. Dave (1 comments)

    I’m sitting in Iraq now just soaking in information for my reunion with my beloved XT10 at home near Seattle, Washington. I just wanted to let you know I’ve learned a good bit from you on your sites. I downloaded Stellarium a while back and am impressed with it. I intend to try the flocking material when I can because those neighborhood lights are a big problem. Anyway, your efforts are appreciated.

  2. XTSee (24 comments)

    Hi Dave, thanks for the comment, glad its been of use! Yes, I really like Stellarium. I think its probably very similar to TheSky6 which should be far superior, and I would like to get some time soon. The flocking was well worth the effort and seems to help on nights with full moon also. Its only when the scope is pointing almost directly at the street lamp that it affects the view, so I’m quite pleased. The only thing I should have paid attention to was the overlap of each strip of flocking material, because the material has contact adhesive on the back which sticks VERY well to the metal tube interior (have to be careful to line it up properly before sticking down as its a pig to lift up again), but it does not stick to itself too well. Of course this is probably to be expected, but over a few days the material curls up and away from the overlaps. Where I used narrow overlaps (e.g. 5-10mm) its not too much of a problem. But where a larger overlap occurs (e.g. 25mm), because I didn’t place it properly but was committed because the adhesive is so strong, the curling lifts the corners or edges of the strips a bit too far for my liking, to the point where it could start encroaching on the field of view. Also I learnt that it is a mistake to add small pieces of flocking to cover bolt/nut heads (at the altitude bearing mount points) as these soon un-stick and fall off and down onto the primary mirror! Another piece 2inches x 6inches which I had cut to stick over a long narrow triangular section of bare metal (that badly placed piece again!) also came un-stuck after a few days, and it wasn’t until I set the scope up and looked through that I thought, “What the heck is that oblong shadow?”, and discovered the strip laying across the mirror, which I had to shake the scope horizontally to get it to fall off the mirror, then gingerly remove with one of those long flexible grab tools. So the moral is to use some strong resin glue (i.e. Araldite) to help glue down corners and wide overlaps when you do the job the first time round!! I’m going to have to dismantle the scope again to do the job properly. You’ve been warned! ;-) I wonder what the night skies are like in Iraq?
    Jim

  3. garden gift (1 comments)

    Very interesting blog. Im new to stargazing but this info is useful thanks


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