Secondary issues

[Dave_D]

So, trying to sort this scope out and iron out the wrinkles... Here are a couple of pics of the secondary showing the position the laser from my collimator strikes the mirror and the great splodges of whateveritis they used to attach it. The spider is centralised but the mirror is definitely off-axis, most likely because of the lousy method the previous owner attached the mirror to the spider. Anyways,

Looking for suggestions on the best method of reattaching the secondary as, from my calcs, reseating the mirror will bring it back into alignment.

[Stargazer33]

Looks like they have used hot glue!

Is there not enough adjustment on the secondary to compensate for the mirror not being centred on the carrier properly?

[John]

I have a feeling the secondary mirror is positioned as it is on purpose. It looks like it's from an Orion Optics (UK) scope and I believe the offset is deliberate and required in newtonians of F/6 and faster.

Skywatcher and Meade also design the secondary offset into the positioning of the secondary mirror on it's holder.

You secondary may need re-coating at some point though. 

Believe it or not, that attachment method is the one used by Orion Optics !

[Dave_D]

No, there's not :/ i need a good 10mm+ extra which i don't have. not to mention the spider vanes would look like the CND logo lol. I think remounting the mirror is the best option, just not too sure whether to go for a mechanical method or bond it on.

[Dave_D]

I have a feeling the secondary mirror is positioned as it is on purpose. It looks like it's from an Orion Optics (UK) scope and I believe the offset is deliberate and required in newtonians of F/6 and faster.

Skywatcher and Meade also design the secondary offset into the positioning of the secondary mirror on it's holder.

You secondary may need re-coating at some point though. 

Believe it or not, that attachment method is the one used by Orion Optics !

That's interesting to know i'll leave it be for the moment and give them a ring during the week and get their feedback

[stargazerslivingroom]

On Astro Baby's collimation guide there is mention of this offset on fast Newtonians.

Check it out. See the bit about fast/slow telescopes....http://www.astro-baby.com/collimation/astro%20babys%20collimation%20guide.htm

HTH

Steve

[Moonshane]

the geometric centre of a secondary and the optical centre are not the same. this is why the secondary is fast newts is offset slightly.

I also agree that although that silicone (clear originally) is looking old, that's how you fix a secondary. all looks pretty standard to me. I don't use a laser I use a cheshire which provides good results.

[Jason D]

 the secondary showing the position the laser from my collimator strikes the mirror

For a properly collimated scope, the laser beam is expected to hit the secondary mirror above its geometric center. See attachments to understand the reason.

[Dave_D]

Thanks for the input people... a bit of late-night reading (instead of watching battlestar galactica for the 50th time lol) cleared the theory up. didn't help that my laser collimator was also pointing in completely the wrong direction