A productive afternoon..

[Astroscot2]

In preparation for some Planetary imaging i swapped out the frac for the newt, decided to clean the primary as it was looking quite dirty plus a few frustrating hours collimation with the cats eye tools. Got there in the end.  Roll on clear skies.

[Mr H in Yorkshire]

Now you've done it. Three weeks of solid cloud.

[bosun21]

I actually spent today by collimating my 6” reflector and classical Cassegrain. The reflector was the easy one and took literally minutes whereas the CC was a bit more tricky. All done now and just waiting for clear skies.

[Astroscot2]

I find making adjustments to the secondary a real chore, the changes required are minute to align the reflections,  must be a better solution mechanically than the push/pull of the secondary screws, I find myself going around and around with the adjustments.

Mark

[Astroscot2]

48 minutes ago, Mr H in Yorkshire said:

Now you've done it. Three weeks of solid cloud.

To add to the 3 weeks I've just had 😀

[bosun21]

1 hour ago, Astroscot2 said:

I find making adjustments to the secondary a real chore, the changes required are minute to align the reflections,  must be a better solution mechanically than the push/pull of the secondary screws, I find myself going around and around with the adjustments.

Mark

Isolate the secondary mirror with a sheet of coloured paper inserted in the tube blocking the primary and a white sheet flat directly opposite the focuser. This allows you to isolate the reflection of the primary and highlights the secondary. Just get it perfectly round and concentric with the focuser draw tube.

[Spile]

1 hour ago, Astroscot2 said:

I find making adjustments to the secondary a real chore, the changes required are minute to align the reflections,  must be a better solution mechanically than the push/pull of the secondary screws, I find myself going around and around with the adjustments.

Mark

Start with the offset and move the secondary towards or away from the primary in order to get a=b and to get the rotation error as minimal as possible. That will be a coarse adjustment because the central screw will be loose. Next adjust the three outer bolts (the fine adjustment) to correct the tilt/rotation so that b=c and d=e. 
I don’t recommend covering the reflection of the primary mirror. The dark  offset secondary “pointing” away from the focuser is an alignment check.

[Mandy D]

@Spile a=b, b=c, d=e? It would help us all if you could perhaps indicate what these letters represent.

[Spile]

8 hours ago, Mandy D said:

@Spile a=b, b=c, d=e? It would help us all if you could perhaps indicate what these letters represent.

It’s how I avoid using terms like roundness and concentric in my collimation guide in an attempt to reduce the number of words used to describe the intended result…

Edited August 29, 2023 by Spile

[Mandy D]

@Spile Thank you. That is clearer, now. However, the two words concentric and circular work for most people and require no further explanation and no need to keep referring back to a diagram.

[Astroscot2]

I would spend lots to time focusing on getting the secondary  to appear circular at the beginning of the collimation process for the life of me I've never been able to get it exact. I've done all the checks that mirror, spider and focuser are central and square to the tube but something must be askew somewhere

 Anyway I read that the secondary being very slightly off circular won't affect the collimation if everything else is looking aligned, it will only show as a slight unevenness of the illumination on the fov which is not a huge concern for my imaging. I would love to know what the issue could be but for now I live with it.

[maw lod qan]

Wow, your observatory looks so neat and cleaned compared to mine! 😒

[Astroscot2]

1 hour ago, maw lod qan said:

Wow, your observatory looks so neat and cleaned compared to mine! 😒

It's just the camera angle . Plenty of debris,  spider webs galore. Needs a good sweep out.

[Spile]

22 hours ago, Mandy D said:

@Spile Thank you. That is clearer, now. However, the two words concentric and circular work for most people and require no further explanation and no need to keep referring back to a diagram.

That’s my point - words work for some but others like me prefer diagrams or photos and as we all learn in different ways, having a range of different guides is  great.