Jump to content

548140465_Animationchallenge.jpg.32379dfa6f3bf4bba537689690df680e.jpg

Need help with Secondary Mirror


Recommended Posts

6 minutes ago, Dinoco said:

On the other side of the tube there is screw, but I think I have just fixed it, where the bar goes into the circle part (where the screws are located) it wasnt properly tightened. As you could see it was quite low down the bar ( I think this is what you guys were saying sorry if it was) but however it’s still going to one side maybe I’ll try and tighten the screw on the tube 

edit: the screw  doesn’t move as it’s already tight. The mirror doesn’t move as much now as before I think the scope needs to be colimated so it does move?

Sounds promising.  If tightening the screw into the upper part makes the back of the secondary holder no longer 'roughly' at right angles to the tube, ie cranked over, then you will have to loosen the screw at the other end to level it up as the adjusting screws will only be able to take out so much adjustment...maybe 10 degrees or so.  In order, I would make sure the holder is tight on the end of it's support bar, then make sure by adjusting where this support bar  slides though the tube that the secondary holder 'back plate' is roughly flat/perpendicular to the tube... roughly parallel to the main mirror if you like.  Finally you can set about collimating by adjusting the screws through the backing plate as per the many excellent guides on the web.

John

  • Like 3
Link to comment
Share on other sites

24 minutes ago, runoffshed said:

Sounds promising.  If tightening the screw into the upper part makes the back of the secondary holder no longer 'roughly' at right angles to the tube, ie cranked over, then you will have to loosen the screw at the other end to level it up as the adjusting screws will only be able to take out so much adjustment...maybe 10 degrees or so.  In order, I would make sure the holder is tight on the end of it's support bar, then make sure by adjusting where this support bar  slides though the tube that the secondary holder 'back plate' is roughly flat/perpendicular to the tube... roughly parallel to the main mirror if you like.  Finally you can set about collimating by adjusting the screws through the backing plate as per the many excellent guides on the web.

John

Thanks John, don’t think I have the right tools to use on the screws yet but will let you know when I try and do it slowly getting there :) thanks for the help. Doesn’t move as much when I move the scope as before which is a good sign

Edited by Dinoco
  • Like 1
Link to comment
Share on other sites

16 hours ago, alanjgreen said:

This is normal. Someone has collimated the scope (changed the angle of the mirror) by loosening the screws in varying amounts. Don’t worry about the height of the collimating screws (unless they have been loosened so much they have come out !)

First job is to read the collimation guide linked above and buy a collimation tool such as a “Cheshire eyepiece”

https://www.firstlightoptics.com/other-collimation-tools/premium-cheshire-collimating-eyepiece.html

Dont mess with the collimation until you are prepared. Just turn the whole secondary assembly while looking down the focuser hole. Turn it until you see the maximum amount of mirror through the focuser hole. Then tighten the middle locking screw. That will be good enough for now.

Now WAIT until you have a Cheshire and read and learn the collimation procedure...

Thanks, I’ll do what you suggested I was doing what you said earlier about the secondary assembly before but  didnt really work as it kept turning but have ( sort of ) fixed it. It’s much better than it was need to buy the correct tools. 

Edited by Dinoco
Link to comment
Share on other sites

Dinoco,

The screws shown in your first photo are simple "Philips" cross-head. The Wickes set that you mention are "Torx" 6-point star-shaped, and will not fit a cross-head screw.

When making any adjustments, keep the tube horizontal, so that if you drop the tool it does not slide down the inside of the tube and smash into the mirror.

Geoff

  • Like 1
Link to comment
Share on other sites

3 hours ago, Geoff Lister said:

Dinoco,

The screws shown in your first photo are simple "Philips" cross-head. The Wickes set that you mention are "Torx" 6-point star-shaped, and will not fit a cross-head screw.

When making any adjustments, keep the tube horizontal, so that if you drop the tool it does not slide down the inside of the tube and smash into the mirror.

Geoff

Thanks, i did think they were,  but couldn’t properly tell. 

 

Link to comment
Share on other sites

Have just managed to get the telescope to work :). It wasn’t anything to do with the screws. I had to  just properly tighten it like I mentioned previously. And now it doesn’t move at all when the telescope moves in a different direction. Only problem now is I need to find the eyepieces. I’ve only got a 20mm one. Is it worth buying cheap ones for this scope? Thanks for all the previous help. 

Edited by Dinoco
Link to comment
Share on other sites

33 minutes ago, Dinoco said:

Have just managed to get the telescope to work :). It wasn’t anything to do with the screws. I had to just just properly tighten it like I mentioned previously. And now it doesn’t move at all when the telescope moves in a different direction. Only problem now is I need to find the eyepieces. I’ve only got a 20mm one. Is it worth buying cheap ones for this scope? Thanks for all the previous help. 

If youve decided what scope you are buying next then buy one that you can also use on the 130

the 130 comes with 25mm and 10mm in the box (according to the spec)

the 130 has focal length of 650mm, so 25mm = 650/25 = x26 mag & 10mm = 650/10 = x65 mag

in the 76/350, your 20mm will be 350/20=x18

the max magnification for the 76mm will be likely around x80. You should be able to get x175 out of the 130mm. some options would be...

7mm       350/7 = x50           650/7 = x92

6mm       350/6 = x58           650/6 = x108

5mm       350/5 = x70           650/5 = x130

and so on...

https://www.firstlightoptics.com/celestron-eyepieces/celestron-omni-plossl-eyepiece.html

https://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-sp-plossl-eyepieces.html

  • Thanks 1
Link to comment
Share on other sites

2 minutes ago, alanjgreen said:

If youve decided what scope you are buying next then buy one that you can also use on the 130

the 130 comes with 25mm and 10mm in the box (according to the spec)

the 130 has focal length of 650mm, so 25mm = 650/25 = x26 mag & 10mm = 650/10 = x65 mag

in the 76/350, your 20mm will be 350/20=x18

the max magnification for the 76mm will be likely around x80. You should be able to get x175 out of the 130mm. some options would be...

7mm       350/7 = x50           650/7 = x92

6mm       350/6 = x58           650/6 = x108

5mm       350/5 = x70           650/5 = x130

and so on...

https://www.firstlightoptics.com/celestron-eyepieces/celestron-omni-plossl-eyepiece.html

https://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-sp-plossl-eyepieces.html

Thank you.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.