Collimation probs

[Guest Derek S]

Hi i a,m new to this site and astronomy, i have just bought my first telescope,it was a toss up to buy the Evostar 120 or the EXplorer 150pl.I finally decided on the Explorer.I have to honest here am wondering if made the right decision.Reasons are the culmination of 2 mirrors which is not going well at all.Now i realise it takes  practise and time but i have spent 3 hours in my garden trying to line up both mirrors and failed,problem is the secondary mirror, i have a  Cheshire tool basic.Now my prob is in using the phillips screwdrive and alan key every time i try to center things they move as soon as i tighten up any screws.Basically i am like a fish out of water,i decided to take this up as a hobby after taking some moon shots with my canon camera i am 74 retires so have plenty of time. I believ the refracture does not need colminatin.I will be   scanning the skies from my garden only and have no idea where to find anything or where except the Moon of course.Now unless i get these mirrors sortedi will be doing not a lot.Any help be appreciated.Regards Derek

[Ruud]

Does this help?

 

[Guest Derek S]

Yes i saw this did not help me though it was perfomed to fast 

 

[Demonperformer]

Hi, Derek, and welcome to SGL.

New collimated a newtonian, so I'm not sure I can be a lot of help. This is quite a popular guide to newtonian collimation by one of our members. Other than that, I am sure some of our newt-owning members will be of more use than me.

Enjoy the journey.

[Peter Drew]

Where are you based Derek, maybe someone nearby can help you, amateur astronomers are everywhere.   😀

[spillage]

Hi Derek 

If I am reading this right then you are talking about the secondary mirror.

I  find that making it just loose enough to rotate helps. Rotate it till its looks like a full circle in the focuser and then just nip the central screw a little so you can actually still move it if needed. You are not trying to tighten it soo much that it cannot be moved. Then you can use the three allen bolts for final adjustment.

I spent way too long trying to collimate my kit and I am still not happy with the results but I am getting better.

I think you may be best taking your time and not trying to rush to get those views. Us a night or two (even if its not clear enough for observing for clear enough to see some stars) Find a bright star and then focus out and in to make it look like a doughnut and see how it looks. With visual you do not need perfect collimation. 

[bingevader]

What made you feel you needed to adjust the mirrors straight away?

Maybe I'm lucky, but my 'scope tends to hold it's collimation well.

I don't think three hours on your first attempt is too bad though.

I spent a very wet and rainy afternoon getting to grips with collimation the first time I did it.

spillage's advice is spot on.

I've always used a cheshire and a collimation cap as in Astrobaby's guide, but having just watched the video above, it does seem a lot easier with a laser!

Saying that, it does get quicker and easier when you get the hang of it.

Stick in there, you will get it.

[Guest Derek S]

Vacuum i bumped the barrel and threw it all out

[Astro-Geek]

Adjustment of the secondary can be very confusing to anyone who has not done it before because it involves the very slight simultaneous adjustment of four screws, each of which affects the other three, so it can seem impossible.

In addition, that mirror has to be adjusted simultaneously for rotation, tilt, and distance in from the front of the telescope, so that it is exactly opposite the centre of the eyepiece focusing tube.

Once a Newtonian is reasonably well collimated, only the tilt needs very occasional adjustment, via the three smaller screws, and the trick is to tighten or loosen them in very small increments, less than a quarter of a turn, whilst maintaining the rigidity of the mirror by gently tightening or loosening the screw(s) opposite the one you have loosened.  If all three are loose at the same time, the mirror will just slop around under gravity.

Think of it as pivoting on the point of the large middle screw with the three smaller outer screws holding it tilted at a precise angle.  You have to minutely loosen at least one before you can tighten any of the others.

If however, it is well out of adjustment after a failed attempt to adjust it, then it's probably best to seek the help of a someone who has mastered the art.

[Ricochet]

When adjusting the angle of the secondary mirror you use the three outer screws and leave the centre one. You must unscrew one a touch and then screw one of the other two up. You should be able to see which way the mirror has moved. It is a case of trial and error to learn how to adjust the screws to get it to move in the way you want it to. 

[Guest Derek S]

Thanks for the help guys,some one mentioned,a guide to Collimation by Gary Seronik,i have just had a look at that ,going to give it a try over the weekend..

[Guest Derek S]

Hi a update on my calamity i have manged to collumate with the aid of a cheshire,what i did wrong from the off was i thought the alan screws at the front was for columatin live and learn eh.now i have had a go at the secondary mirror which i miss aligned my fault..the view from my cheshire it what  my viewer is aligned to but when i take the cheshire out and put a eyepiece  in i can not see a thing