Is this out of collimation?

[Nikolai De Silva]

Hello, 

This is how I see through the DIY collimation cap I made. Is this out of collimation? The scope is a SW Starquest 130p. 

And also how to adjust the the secondary mirror where no bolts are there?

[happy-kat]

Is the telescope f5 or something else?

 

[Ricochet]

58 minutes ago, Nikolai De Silva said:

Is this out of collimation?

It is impossible to tell. You need to place some light coloured card or paper behind the secondary mirror so that we can see where the edges of the mirror and focuser are in order to judge whether they are concentric. You also need to smooth down the foil on your collimation cap so that the entire surface looks bright. The dark dot formed by the eye hole should be inside the doughnut on the primary mirror but with such a large dark section in your cap the hole is not visible.

1 hour ago, Nikolai De Silva said:

And also how to adjust the the secondary mirror where no bolts are there?

The three outer bolts are recessed and need adjusting via a suitably sized hex/allen key.

[Mkv]

I'm not sure about your particular telescope, but if the secondary collimation screws are missing, then you'll need to find a replacement. You might as well get yourself thumb-turn screws, the SkyWatcher 250P uses M4 thread 35mm length screws, so yours might be similar

[Nikolai De Silva]

Yes @happy-kat. This is a f5. And the Primary mirror is fixed.

@Ricochet Now I smoothed the foil and torched to see. 

[PeterStudz]

As mentioned above - on these SkyWatcher telescopes the outer secondary adjustment bolts are usually recessed bolts that require a hex/allen key for adjustment. Unless someone has removed/replaced them. 

However, unless you are 100% certain that the secondary requires adjustment do NOT attempt to touch it. I have a small SkyWatcher 1145p reflector and I’ve never had to adjust the secondary. Even after a journey that involved taking a four hour flight on an aircraft, 2 hours in a car, another 2 hours in a taxi on mountains roads. Wheeling the case over cobbled streets, finally a short journey on the sea via ferry. Oh… and back again. In fact I was surprised to still find the primary spot on too. Phew… I’m exhausted just from typing that! 

[PeterStudz]

PS - to me it looks like the secondary adjustment bolts are there. Just recessed (as they should be) and difficult to see. 

[Nikolai De Silva]

Yes @PeterStudz and @Ricochet, there are Allen screws recessed. Thank you!

[Spile]

My guide explains the relationship between the outer screws and central bolt which work in a push pull way. As @Ricochet says in order to confirm the secondary is aligned you need to see the outside of the sight tube. Place a sheet of paper behind the focuser and take the picture again. This is what you are aiming for…

[bosun21]

13 hours ago, Mkv said:

I'm not sure about your particular telescope, but if the secondary collimation screws are missing, then you'll need to find a replacement. You might as well get yourself thumb-turn screws, the SkyWatcher 250P uses M4 thread 35mm length screws, so yours might be similar

They are recessed. If they were missing the mirror would be moving all over the place.

[Nikolai De Silva]

4 hours ago, Spile said:

My guide explains the relationship between the outer screws and central bolt which work in a push pull way. As @Ricochet says in order to confirm the secondary is aligned you need to see the outside of the sight tube. Place a sheet of paper behind the focuser and take the picture again. This is what you are aiming for…

Ok I'll do it soon as possible and upload it.

[dweller25]

@Nikolai De Silva

I would suggest before you change the collimation screws that you do a star test first to see if it needs adjusting.

If it does here is what to do…..

Edited January 14 by dweller25

[Ricochet]

40 minutes ago, dweller25 said:

@Nikolai De Silva

I would suggest before you change the collimation screws that you do a star test first to see if it needs adjusting.

If it does here is what to do…..

Some points on this:

• A star test must be performed with an eyepiece with a focal length equal to or shorter than the focal ratio of the telescope
• The star must be precisely centred in the field of view and stay centred during collimation. A off centre star looks the same as a uncollimated scope. For an undriven scope this means using Polaris, which at only 8° Nikolai may not be able to see.
• I believe the above instructions apply to adjustments made to the primary mirror, which cannot be adjusted for the scope in question.
•  Based on experience, never attempt to adjust the secondary using a star test, it will not go well.

Given the above, I would suggest a quick star test is a good way to check if the collimation looks ok, but if it is shown to be out it is better to accept the collimation is out and to just enjoy the views the scope provides in its uncollimated state, and then attempt collimation of the secondary the next day during daylight.

[Nikolai De Silva]

Thank you @Ricochet and @dweller25. Surely I will do it.

[Spile]

As @Ricochet states, the star test will not tell you if your secondary is misaligned and in addition to the check list above, it needs to be carried out under high magnification.

[Nikolai De Silva]

Dear @Ricochet, @dweller25 and @Spile, 

Last days we didn't have good skies. Yesterday night we had good skies and I did the star test. Fortunately it is in collimation 😊. It's ok as @dweller25 has told.

Thank you all for your kind responses! 👍🙂.