New scope with crap eyepieces?

Hi Crescent, Firstly congratulations on an excellent first telescope and secondly welcome to the dark art of collimation.

Just make sure your laser collimator is collimated or erroneous results may occur leaving you scratching your head in confusion. I personally don’t favour the laser approach for a number of reasons, I may be old fashioned but I prefer mark one eyeball star test. You could opt for a Cheshire eyepiece which is a well established and proven method for collimation for your type of instrument. Remember your telescope is a precise optical instrument so caution should be noted when adjusting any of the main optical components, very small adjustments can go a long way in this case, there are some horror stories out there when things go wrong with collimation, but don’t let that put you off, there is also plenty of good information in printed and software form in order to help you do things correctly. As the guys rightly say if your telescope got a knock or if you intend to move it around by car and setup etc then collimation checking (and adjustment if required) should be part of your pre-observing routine to get the best out of your telescope.
I don’t have a Newtonian telescope myself but an SCT. I started out with mark one eyeball star testing method (still use that method) and recently in combination with software entitled CCD Inspector, but of course this requires a CCD camera which I am sure you may use with your telescope one day. It may turn out that your eyepieces are fine once you have the collimation sorted, I think the reason why the image is worst with the 10mm is that it magnifies the off axis optical error, in this case the magnification is x75 as opposed to the 25mm eyepiece which gives a magnification of x30. Anyway, as the saying goes “there is more than one way to skin a cat” and collimation can be completed in different ways with different instruments and each with their good and bad points.

Clear skies
Mike

Thanks everyone for your advice. I think i will get the cheshire tool first, I hope it will give me a better understanding of the workings of the mirrors and i will get a laser one in the future. The tool Seanie has a picture of above is £29 delivered from ace cameras. I think i will get that.

I'd really recommend the use of a cheshire eyepiece before using a laser. The laser will certainly allow the primary and secondary to be aligned, but without using the cheshire first there is the possibility for an off-centre diagonal.

The resource that I learned from is currently offline for whatever reason, but there is an acceptable alternative here: www.skyandtelescope.com/howto/diy/3306876.html .

For years I made a mess of collimation, and once I got my hands on the right tool it all came together.

Using a cheshire eyepiece for collimation:

1. Get the focuser aligned correctly, to the centre line of the tube and at right angles to the tube wall. (Usually done by the manufacturer, but sometimes adjustment is necessary).
2. Centre the secondary mirror in the telescope tube using the spider arm adjustments. Very slightly offset the secondary mirror away from the focuser, maybe 1-3 mm.
3. Centre the secondary mirror in the view along the focuser tube.
4. Centre the primary mirror central spot using the secondary's rotation and tilt. If there is no central spot, I'd suggest putting one on. If the secondary was way off collimation, step 3 may need to be repeated.
5. Get the primary mirror aligned using the primary mirror cell collimation bolts/screws until the reflection of the cheshire eyepiece silvered portion is centred.

That is usually close enough for most people.
After this it's startesting with a high power view of e.g. polaris.

Centre the star in the field of view.
Focus the star.
Note the direction of the coma.
Defocus the star a bit, and use e.g. hand or a finger around the tube opening to see where the coma direction was pointing.
Select the bolt nearest the coma direction, and turn it a small but known amount e.g. 1/8 of a turn.
Re-center the star in the field of view, and see how the coma looks now. If it has more coma, go back to the bolt and turn it back to the start position and turn a further e.g. 1/8 turn.
Repeat as the appearance improves until there is no coma present in the star's image in the centre of hte field of view.
Once this is done, focus the star and enjoy the pin-sharp view that you now should have.

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If you are still getting bad views in the eyepiece, try to borrow an eyepeice or eyepieces that are known-good to use for testing. That will be a good way to isolate if it's the scope or the eyepieces.