Collimating Again (Sorry)

[Boyd_CygnusX1]

Hi,

I bought a cheap and very nasty reflecting telescope. I've managed to observe Venus but had trouble getting it in focus.as a result I decided to have a look at the alignment with a view to collimating it. When I look into the viewer without an eyepiece the reflection of the secondary mirror looks odd. Rather than the circle I was expecting it looks like an eye shape (with my eye inside it) Is this correct? It is also off centre so presumably the primary mirror needs adjusting. However there is no centre mark on my main mirror for adjusting the alignment. How do I get around this.

Cheers

Boyd

[tms48]

The secondary mirror should be a round shape, the reflected view of it will be off centre. how much depends on the focal length of you telescope. Small F numbers have more offset.

It sounds like you do need to collimate your telescope, but as far as my knowledge goes you will need to mark your main mirror with a centre spot.

Collimation methods are described on lots of sites, and Astro Babys is the one I used when I first started.

[Tribal-Wolf]

Come on share.....how cheap and how nasty lol?

[Boyd_CygnusX1]

Come on share.....how cheap and how nasty lol?

bushnell voyager 114 £40

[Tribal-Wolf]

What EP were you using to view?

[mdstuart]

114mm thats a great little scope...

You should be able to see the whole of the primary mirror in the secondry with the three mirror clips around the edges..In the middle you should as you say see your eye reflected in the middle of the view..

Try pointing the scope at the pole star and then defocusing to see if you get a nice circular paturn...

Mark

[Boyd_CygnusX1]

114mm thats a great little scope...

You should be able to see the whole of the primary mirror in the secondry with the three mirror clips around the edges..In the middle you should as you say see your eye reflected in the middle of the view..

Try pointing the scope at the pole star and then defocusing to see if you get a nice circular paturn...

Mark

Well it was till I started fiddling!

I can see the 3 clips and my eye. My main concern was the shape of the secondary's reflection as it looks round in all the collimating diagrams that I have seen.

[Boyd_CygnusX1]

What EP were you using to view?

H20 and H12. I found that Venus looked ok in twilight but when fully dark the bright side was too bright and I could not seem to focus on it.

[pel]

Hi Boyd ,

It sounds like you're getting a good view of Venus. In my experience it is very very bright and difficult to focus. How about having a go at Mars, that is high in the sky fairly early in the evening. It's less bright and will prove there is nothing wrong.

The images I produced with my SPC900, were darkened significantly -

http://stargazerslounge.com/members/pel-albums-planet-pictures-picture16363-1st-ever-venus-sw-200p-pre-ding.html

Perry.

[Boyd_CygnusX1]

The picture of Venus looks pretty much like what I can see though Mar is much larger than anything that I have observed. It was just a fuzzy blob in my telescope and that was before I started messing around with the secondary mirror!!!! I will give it another try this evening if it is clear.

[pel]

The picture of Venus looks pretty much like what I can see though Mar is much larger than anything that I have observed. It was just a fuzzy blob in my telescope and that was before I started messing around with the secondary mirror!!!! I will give it another try this evening if it is clear.

What about viewing stars, are they nice and round or mis-shapen?

I found collimating with a lens cap with a hole through the middle the easiest way to collimate. I have a laser collimator but the alignment doesn't seem consistent when I tighten up on it in the viewer.

I found this link very easy to follow for Collimating -

Collimating a Newtonian

[Boyd_CygnusX1]

I haven't had a chance to check the stars since I "adjusted" the secondary mirror. What size hole should I put in a lens cap for collimating? The video does make it look very easy so hopefully using that an Astro Baby's Guide I should be able to get it sorted out.

[pel]

I'd say the hole I made was 3mm. I can just about see all 3 primary mirror clips. I see the secondary/my eye in the centre when I look and on my scope there is a little circle in the centre of the primary.