Seeing secondary mirror in stars?

[efdee]

Hello everyone,

I just got my first telescope (a SkyWatcher Explorer 130p) a few days ago, so forgive me if this is a rookie mistake.

I've been able to successfully calibrate and mount my telescope and last night, I spent some time watching the stars. I can get them into view, but it seems that whenever I see a star, it is covered by the secondary mirror. Is this normal ? On one hand, I think it might be, since well, that mirror thing is dangling right in the middle of my telescope, so I don't get how it could *not* be in the way. But on the other hand, I haven't seen this on any of the SWE 130p pics I've seen so far.

As a bonus, I have attached an... artist's rendering of this phenomenon. This is what I see through the telescope when watching a star.

The cover of the telescope opening (the one you take off when using the telescope) also has an opening in it that allows you to see if there is too much light (you put the cover on, unscrew the opening, and basically it acts as a smaller opening). This way I can bypass the mirror (since the light passes next to it) but my stars are a lot smaller.

Can anyone shed some light (he he. I'm sorry!!) on this?

Thanks!

[StarryBob]

Sounds to me like you're not correctly in focus. Try winding the focuser in and out all the way till you get a better view.

[DirkSteele]

You are seeing the shadow of the secondary mirror which is a consequence of not bringing the scope to focus. Rack in and out the eyepiece using the focuser and the stars will come to focus when they are small points of light.

[olander08]

Are you looking through an eyepiece or just through the focusing tube?

Edit: Now that I clicked on your image I can see that the white blob actually is the star heavily out of focus, so follow the instructions of the posts above.

[swamp thing]

^^^What they said. No amateur scope is ever going to be able to resolve the discs of stars they're far to far away. In fact the bigger your scope the smaller the stars will appear as the resolving power of the scope goes up the star images get smaller.

This ability to see a smaller star image translates to being able to see finer detail in objects, split closer double stars etc ,the bigger the scope the better the resolving power.

HTH

[Kevdan]

HI,

If you want to check focus you can use a bahtinov mask, these will show a star as a 6 point object and when correct the focus of your scope will be in focus,

go to http://astrojargon.n...CookieSupport=1 to make your own from a bit of A4 cardboard put 650 in the focal length box and 130 in the apperture box and then click generate, then print out onto a bit of paper put that over a bit of card and cut it out, shouldnt take long and you can then check your focus, if it works for you then FLO sell them http://www.firstligh...ocus-masks.html properly made at £15 and they are worth the money.

Kev.

just to add they are £15 for your scope, bigger ones are more expensive

[farunj]

Yup I think it's definitely due to incorrect focusing.

[knobby]

I'd agree with olander08, that looks like no Eyepiece to me, looks pretty well collimated though!

Have you got a small lens in the holder or is it an open hole?

Should have a Lens in place.

[earth titan]

HI,

If you want to check focus you can use a bahtinov mask, these will show a star as a 6 point object and when correct the focus of your scope will be in focus,

go to http://astrojargon.n...CookieSupport=1 to make your own from a bit of A4 cardboard put 650 in the focal length box and 130 in the apperture box and then click generate, then print out onto a bit of paper put that over a bit of card and cut it out, shouldnt take long and you can then check your focus, if it works for you then FLO sell them http://www.firstligh...ocus-masks.html properly made at £15 and they are worth the money.

Kev.

just to add they are £15 for your scope, bigger ones are more expensive

Not sure bahtinovs work well with visual observing, but then I've never tried. I thought they only worked for long exposure photos.

Will have to try and see.

[scoobymike]

Not sure bahtinovs work well with visual observing, but then I've never tried. I thought they only worked for long exposure photos.

Will have to try and see.

A bahtinov mask allows you to achieve precise focus, whether you are imaging or viewing. People tend to use them more for imaging as imprecise focus of a faint/wispy cloud of gas means the image will be blurry and have no detail.

[knobby]

A bahtinov mask allows you to achieve precise focus, whether you are imaging or viewing. People tend to use them more for imaging as imprecise focus of a faint/wispy cloud of gas means the image will be blurry and have no detail.

Yes ... but from the O.P.s picture that's so far out of focus a Bahitov would be of no use at all, I still think he's not got an EP in the holder!

[efdee]

Hey guys,

Thank you all for replying, I wasn't expecting such a massive response. The issue was with the focus indeed. I'm almost ashamed to admit that I didn't even notice the focus dial. In hindsight, I should have known, and the fact that I saw a star that big should have been a big hint too :-)

I tried again yesterday with correct focusing and it worked like a charm. Spent an hour looking at the moon, too. Just awesome!

[DirkSteele]

Fantastic. Glad we could all help.

Clear skies,

Matthew

[knobby]

Hey guys,

Thank you all for replying, I wasn't expecting such a massive response. The issue was with the focus indeed. I'm almost ashamed to admit that I didn't even notice the focus dial. In hindsight, I should have known, and the fact that I saw a star that big should have been a big hint too :-)

I tried again yesterday with correct focusing and it worked like a charm. Spent an hour looking at the moon, too. Just awesome!

Result!