Celestron c11

[Virgo man]

Hi guys Virgo man here its about my c11 tried to collaminate it got bobs knobs I have tried three time cant get it ?? I can't even see a star through it to focus on having major problems guys does anyone live in central Scotland looking for someone to have a look at it incase it's something else ? Is anyone out there : would pay someone to fix it it's doing my head in guys ? Cheers rob.

[YKSE]

Maybe you can tell us a bit more about the C11?

1. Have you replaced the bobs knobs by youself?

2. Have you replaced them one at a time? i.e. not unscrewed all the three original ones first.

3. Could you focus on a star before the bobs knobs replacement?

4. Have you turned the focuser slowly from one end to the other to reach focus?

5. How did you do the collimation? Tools and methods to do it?

Collimating a SCT is not easy (can be frustrating) for a first-timer, but once you learn it, it's very easy and fun too.

[Davesellars]

1:  Calm down...  take a deep breath....

Lets assume that at least you followed the instructions to change one screw at a time and at least your secondary mirror isn't flopping about loose.

So, the mirror most likely is way out of collimation...  but I'd check one thing first since this stuff is harder at night at least check your focus in the daytime on an object in the distance.  Use your lowest power eyepiece you have.  How's the focus?  If it looks OK Increase the magnification.  If you can get to 100x at least then you possibly just need to fine-tune collimation.

To collimate from scratch start with all the thumb-screws so they are equal and finger tight.  Then loosen off all three by a 1/8th of a turn - this should be your starting point to collimate on a star.  If the screws are reasonably equal the collimation while it will be out should  not be horrendous at least.  Start with the lowest power and follow this guide on how to collimate it (by far the clearest I've found):

http://www.asterism.org/tutorials/tut14-1.htm

 

[Virgo man]

Hi mate yes I changed all the screws one at a time and I tried to focus on daylight objects tried with the focus slowly to left then to right can see just light it must be way off used 32m eyepice and then 40m but both same then 13m will check the website you sent thanks rob ?

[Virgo man]

16 hours ago, YKSE said:

Maybe you can tell us a bit more about the C11?

1. Have you replaced the bobs knobs by youself?

2. Have you replaced them one at a time? i.e. not unscrewed all the three original ones first.

3. Could you focus on a star before the bobs knobs replacement?

4. Have you turned the focuser slowly from one end to the other to reach focus?

5. How did you do the collimation? Tools and methods to do it?

Collimating a SCT is not easy (can be frustrating) for a first-timer, but once you learn it, it's very easy and fun too.

Hi yes I replaced the bobs knobs one at a time turned focus knob slowly to right then left tried scope in day light with 32,40,13, eyepices struggling to get any focus at all it wasn't that great before I changed knobs I went with celestron book that came with scope on hoy to collimating it was working good when I got it six months ago I think it's been moved or bumped in my garage but don't know ?

[alanjgreen]

You can achieve a rough collimation in daylight, using bobs knobs and looking through the front of the scope

Here are the steps.

1. set the scope level - pointing level with the ground

2. stand back 3 meters

3. place your head central and look into the "big end" - you should see sets of concentric circles (being reflections of the 2 mirrors inside the scope)

4. if not, then pick any "bobs knobs" and tighten 1/6 of a turn

5. step back to 3m and examine the result of what you just did

6. if it made things a little better then repeat (on the same knob)

6b. if it made things worse then turn it back and move to another knob

7. Once any knob becomes "tight" then you need to loosen the other two by 1/6 th turn to enable the tight one to loosen up

 

TAKE YOUR TIME and work your way around the 3 knobs.

 

Once you are happy, then tighten all 3 knobs by moving them all 1/8th turn & keep repeating...

You need to end up with all 3 tight, this may involve returning to an earlier step to loosen/tighten

 

 

When you see concentric-ish circles then you should only need to do a small adjustment "outsiide at night "to finish off

1. choose Polaris if you can see it

2. use a 10mm eyepiece and defocus the star very slightly (high power 300x is essential) until you see one (or 2) faint circle around the star

3. adjust bobs knobs 1/8 turn on the opposite side to where you see the tightest defocused lines - remember that its the other side to the side you see them in the eyepiece

3a. always "tighten" the choosen knob - only loosen knobs if you need to free up another knob to turn tighter (as in step 7 above)

4. Aim to end up with perfect concentric circles around the defocused star

 

KEY POINT: for the scope to hold collimation for a long time - ALL 3 KNOBS should be "tight" at the end of the process.

[YKSE]

3 hours ago, Virgo man said:

Hi yes I replaced the bobs knobs one at a time turned focus knob slowly to right then left tried scope in day light with 32,40,13, eyepices struggling to get any focus at all it wasn't that great before I changed knobs I went with celestron book that came with scope on hoy to collimating it was working good when I got it six months ago I think it's been moved or bumped in my garage but don't know ?

Good, then we know that the secondary is not loose, it's too out of collimation.

I'd suggest that you try the methods proposed by Alan to begin with. You should be able to get a somewhat collimated scope at least. If you have difficulty to get more satisfactory collimation, I'd suggest that you read and follow the steps proposed here:

http://www.astromart.com/articles/article.asp?article_id=548

Good Luck 

[Putaendo Patrick]

Great hints here, but if you give up and need someone to help you, you could get in touch with a local astronomical club. There are several links here: http://www.astro.gla.ac.uk/~martin/sss/sss_groups.html

[Peter Drew]

In daylight it's slightly easier to look through the rear end of the tube without an eyepiece in. You should see the secondary mirror full of light. If not, adjust the Bob's knobs until you do. Once the secondary is illuminated you should see a black rim round the secondary, this is the outline of the secondary holder, adjust the secondary until this rim is concentric and even thickness all round, once it is the optics are near enough to fine tune on a star.    

[ngwillym]

Here's a few more useful articles on how to collimate - both during daylight and using the stars:-

http://www.robincasady.com/Astro/collimation/

https://starizona.com/acb/basics/using_collimating_sct.aspx

http://www.midkentastro.org.uk/?&p=guide-collimatescope

http://skywatch.brainiac.com/collimation.pdf

http://alpha-lyrae.co.uk/2013/12/31/schmitt-cassegrain-collimation-made-easy-using-a-duncan-mask/

I particularly like this last one - the mask is very easy to make

Hope these help

Neil

[Virgo man]

20 hours ago, YKSE said:

Good, then we know that the secondary is not loose, it's too out of collimation.

I'd suggest that you try the methods proposed by Alan to begin with. You should be able to get a somewhat collimated scope at least. If you have difficulty to get more satisfactory collimation, I'd suggest that you read and follow the steps proposed here:

http://www.astromart.com/articles/article.asp?article_id=548

Good Luck 

Thanks mate ?

[Virgo man]

6 hours ago, ngwillym said:

Here's a few more useful articles on how to collimate - both during daylight and using the stars:-

http://www.robincasady.com/Astro/collimation/

https://starizona.com/acb/basics/using_collimating_sct.aspx

http://www.midkentastro.org.uk/?&p=guide-collimatescope

http://skywatch.brainiac.com/collimation.pdf

http://alpha-lyrae.co.uk/2013/12/31/schmitt-cassegrain-collimation-made-easy-using-a-duncan-mask/

I particularly like this last one - the mask is very easy to make

Hope these help

Neil

Cheers Neil will have a go later here's hoping ??

[Virgo man]

17 hours ago, Peter Drew said:

In daylight it's slightly easier to look through the rear end of the tube without an eyepiece in. You should see the secondary mirror full of light. If not, adjust the Bob's knobs until you do. Once the secondary is illuminated you should see a black rim round the secondary, this is the outline of the secondary holder, adjust the secondary until this rim is concentric and even thickness all round, once it is the optics are near enough to fine tune on a star.    

Cheers peter will have a great go st it on Saturday morning will try to see if it works thanks again cheers rob ??