Secondary mirror, worth editing? (Right shape, possibly mis-aligned with primary?)

[pipnina]

With some time to kill before the next clear sky I've been practicing with the new kit. Since this is going to be a photographic setup I should probably have tighter tolerances for collimation error, especially in the secondary mirror.

Looking through my cheshire and the 130-PDS I see the right shape for a "fast" f5 (elliptical secondary shadow) but the edge of the primary is not visible in all of the sides. Does this mean the secondary mirror is aligned properly with the focuser but not the primary mirror, or the other way around?

I took a flat (not of good quality, just to see roughly where the center of the light beam lands) and stretched it a bunch.

And I took a photo with my phone down the cheshire:

Obviously there are many degrees of freedom available to adjust the secondary with, which one fixes this?

On a second note, I'm struggling to loosen the central screw. I'm turning it counter-clockwise and have to hold the secondary support as it started bending the spider veins, didn't budge.

 

Thanks

[spillage]

try easing off the three secondary collimation screws first then undo the center screw. Have you followed astrobaby's collimation guide?

[alacant]

54 minutes ago, pipnina said:

Does this mean the secondary mirror is aligned properly with the focuser but not the primary mirror, or the other way around?

Hi. Both. Move the secondary up or down to get it centred in the focuser first using the advice @spillage gave above.

[pipnina]

34 minutes ago, spillage said:

try easing off the three secondary collimation screws first then undo the center screw. Have you followed astrobaby's collimation guide?

I'll have to dig out the allen key set! Never sure how they can provide you with so many allen keys when you buy telescopes and mounts, but never one that fits the secondary screws!

I'll have to read it again carefully. Primary alignment is so easy, I'll have to take my time with the secondary though I think...

13 minutes ago, alacant said:

Hi. Both. Move the secondary up or down to get it centred in the focuser first using the advice @spillage gave above.

Is this a both as in "the primary, secondary and focuser are aligned" or "neither are aligned"? Is my only problem that the mirror is merely displaced and not with incorrect rotation?

[spillage]

off the top of my head (so may be wrong) I think you need to make sure the secondary mirror is round and central in through the cheshire, then using the three screws get space on all the clips around the primary the same and then line up the primary using the centre spot. Maybe!!!

[alacant]

4 hours ago, pipnina said:

neither are aligned

Hi. A few ideas.

Neither are aligned. The adjustment screws are m4. Replace them with bolts to make thumb screws, thus obviating the need for the dreaded Allen key.:

Then loosen all 4 screws on the secondary, look through the empty  focuser, then tighten the screws gradually to be able to see all the mirror clips like this:

Now put in the sight tube. Still adjusting only the secondary (it will need far less movement now) put the cross hairs on the donut reflection which marks the centre of the primary. Lastly, adjust the primary to make it look like this:

No need to get it perfect. Close is fine.

HTH.