Mars 19/04/2014

[RikM]

I intend to make the most of this while it's close to us. Something odd with my scope last night though. I checked the collimation with a Cheshire (as always) and it looked spot on, however a star test showed quite an asymmetric set of diffraction rings. I tweaked the primary until the star test pattern looked concentric both inside and outside of focus and the detail visible on Mars and the sharpness of the disc was much improved. I also took a quick before and after look at Izar and it was a very much cleaner split after I tweaked the primary. Looking now with the Cheshire, the dot is half-in and half-out of the doughnut. What's going on there then?

Graphite pencil on cartridge paper, overwritten with coloured pencils and smoothed with a blending stump.

[Mike73]

I know everyone says how good Cheshires are but I had exactly the same problem as you a while ago Rik.

I used to use a Cheshire just to check the secondary and a Hotech for the primary and they never agreed, I checked collimation of the Hotech and it was spot on so I bought a TS Concenter and binned the Cheshire and all has been good since.

[Daniel-K]

I know everyone says how good Cheshires are but I had exactly the same problem as you a while ago Rik.

I used to use a Cheshire just to check the secondary and a Hotech for the primary and they never agreed, I checked collimation of the Hotech and it was spot on so I bought a TS Concenter and binned the Cheshire and all has been good since

mike ive looked at these are they simple to use?

[Mike73]

mike ive looked at these are they simple to use?

Very simple Dan, easy to use in the dark aswell.

For what it is its completely overpriced but for me its just a very quick and simple way to check the secondary looks good.

[dweller25]

That's an excellent drawing Rik

[Moonshane]

great drawing Rik! is your centre circle in the centre? are your eyepieces equally inserted (e.g. in my focuserI recently noticed with some eyepieces their own weight means you have to hold then in the focuser when tightening to ensure the shoulder sits evenly)?