Collimation

[Mongo75]

I was curious about my collimation , after reading about it so doing some research, I came across a DIY artificial star that sounded simple enough to give it a look-see. I realize that my DIY project has a lot to be desired, but just as a reference...

My "star" is a milk bottle cap painted black, with a pinhole from a very small sewing needle, and fitted over my LED flashlight. Distance is about 49-50 feet. I have a Celestron C8-A XLT OTA, 8" SCT and my collimation looks horrible! No "donut"!

These photos are with my DSLR, "in focus" and looking for the "donut". I rotated the focus CCW looking for the "donut".

Where would I even start with this other than using a real star rather than my DIY "star"? As a newbie, I'm terrified of screwing up my scope!

[Ozman]

I have no experience with an artificial star, I would just leave it to the real thing.

[JayTee]

A simpler and more exact artificial (sort of) star is to use a chrome ball bearing partially stuck into modeler clay then affixed this to a fence post top, placed 50-100 meters away, during a sunny day. That small reflection of the sun (a star) will work well as an artificial star. Give it a try and see what you think. It works because the sun's rays are parallel rays of light even when reflected off a curved surface.

Cheers,
JT

[Mongo75]

Thanks again, to all!

Lessons learned...use a real star!!!!!
Order collimation knobs from Bob's Knobs!!!!!
Don't look at the moon without a moon filter!!!!!

I received my Bob's Knobs last Saturday, and replaced the factory screws. Following the instructions, I got the collimation in the ballpark looking through the end of my scope and eyeballing it. I could tell it wasn't going to take much to get it done once I got it outside at night. It's been hovering around 100 degrees during the day, and by the time it gets dark enough, I'm drained, so I've been procrastinating, lol.

Last night at 21:30, I got a spurt of energy and headed out to the back yard with all my gear, set up, and got a poor but usable polar alignment. Still fearing the worst, I decided to have a look at the Moon and Saturn, being as they were so close together. OMG! That dang ole moon is bright! I ordered a moon filter, the Orion 5560 1.25-Inch Variable Polarizing Filter while waiting to get my night vision back.

Night vision back, I took a look at Antares. A bit out of focus, but not too bad. Time to start tweaking those knobs. After about 10 minutes, I had it really close. Time to have a look at Arcturus. WOW! looking good. Just a couple more tweaks and there it was. Due to my poor eyesight, I can't get a real sharp focus, but now, the fuzziness is concentric, not flaring off to one side like it was when I started.

Again, thanks to everyone for the input. It really helped!

[Lokifish]

I use an artificial star all the time, it's a fiber optic cable and an LED. It's always diffraction limited collimation friendly, impervious to weather conditions, and comes with heat and AC.

[helicon]

Thanks again, to all!

Lessons learned...use a real star!!!!!
Order collimation knobs from Bob's Knobs!!!!!
Don't look at the moon without a moon filter!!!!!

I received my Bob's Knobs last Saturday, and replaced the factory screws. Following the instructions, I got the collimation in the ballpark looking through the end of my scope and eyeballing it. I could tell it wasn't going to take much to get it done once I got it outside at night. It's been hovering around 100 degrees during the day, and by the time it gets dark enough, I'm drained, so I've been procrastinating, lol.

Last night at 21:30, I got a spurt of energy and headed out to the back yard with all my gear, set up, and got a poor but usable polar alignment. Still fearing the worst, I decided to have a look at the Moon and Saturn, being as they were so close together. OMG! That dang ole moon is bright! I ordered a moon filter, the Orion 5560 1.25-Inch Variable Polarizing Filter while waiting to get my night vision back.

Night vision back, I took a look at Antares. A bit out of focus, but not too bad. Time to start tweaking those knobs. After about 10 minutes, I had it really close. Time to have a look at Arcturus. WOW! looking good. Just a couple more tweaks and there it was. Due to my poor eyesight, I can't get a real sharp focus, but now, the fuzziness is concentric, not flaring off to one side like it was when I started.

Again, thanks to everyone for the input. It really helped!

Glad to see you are well collimated. Another technique is the star test.

http://aberrator.astronomy.net/html/star-testing.html