Monday, 14 March 2011

CaK Full Disk 13th March 2011

Cak full Disk lrg, originally uploaded by Mark Townley.

If you look at my previous CaK images on this blog you will see there is a smearing of the image. This is due to astigmatism - the penta prism that is in the 'black box' part of the PST is misaligned, a common problem with Coronado Ha & CaK PSTs. I had tolerated this for sometime, however decided that with a new year of solar observing starting in earnest it was time to act.

Opening up the black box to reveal the penta prism, it can be seen it is out of alignment by some several degrees - this may not seem a huge amount but it is more than enough to cause smearing of the image snapping pics. The penta prism is connected to a mounting block by means of a soft sticky goo - the sort of stuff that fixes cd's to the cover of magazines. I had contemplated replacing this with another glue, however had visions of getting this all over my fingers and then all over the faces of the prism - which would have been bad - very bad, as it would have meant the prism was a write off.

I ended up deciding on heavy duty sticky backed velcro strips - I figured once I had these in place I could locate the prism in postion, and then , after imaging, if this was not optimum relocate it again.

Seems this method works as the image above shows. It's the sharpest CaK image i've got to date and i'm really pleased to be honest.