Wesley's Tool-Box

Using a Schmidt-Cassegrain telescope (SCT) like my Celestron NexStar 6SE requires the secondary mirror to be collimated properly to get a crisp image. I've done the collimation after fixing the screws, but I wanted to fine-tune further. The adjustment I will be making won't be the definitive for all the cases because the gravity affects the secondary mirror subtly with differing angles. But because the diameter (and consequently, weight) of the mirror is relatively small the deviation after the fine adjustment was hoped to be small.


Unfortunately, the real stars often look too shaky, so I decided to try the artificial star method for this tuning instead. An artificial star is basically a bright light source coming from a tiny hole. For the light source, I do indeed have one - an LED flashlight that I bought many years ago. It's actually an external battery for charging phones with a bright LED as a bonus feature, but it's so old that the charging port is a Korean 24-pin standard that was popular about a decade prior. Now it was time for this little gadget to be useful again.


I initially tried it out as is, but the LED part was too big. It was time for a little modification. After trying out different materials, I found that a sheet of back cover for making presentation handouts was effective at blocking light, yet did not require complicated tools to work with. A pair of scissors let me cut one up to make a cover over the flashlight. Next, I punched a tiny hole where the LED was supposed to be at.

I've mentioned earlier that one of the collimator screws on my Celestron NexStar 6SE telescope was completely stuck, preventing proper calibration. It was so bad that the screw's head became stripped in the attempts to unscrew it, and pliers were of no use, either. To fix this problem, I ordered Anex ANH2-065, a stripped screw extraction kit made in Japan for US$20. It had a lot of favourable reviews, so I thought I might as well try it.

The kit came with two drill bits, one for working with 2.5 to 3mm screws (red) and the other, 4 to 5mm screws (yellow). One end of each bit is used for drilling a small hole in the middle of the screw and the other end is a reverse-threaded tap that gets inserted into this hole. As you turn the bit counter-clockwise, the tap burrows into the screw. Eventually, the screw is supposed to turn with it and come out.


NexStar 6SE's collimator screw is the same one used with C6, an M3 (3mm) type with 12mm length, so I got my old cordless drill charged up and inserted the red bit. I set the torque level to low to reduce the risk of damage, and carefully drilled out a tiny hole about 4mm deep into the stuck screw.