Sunday, 22 April 2018

Ha Full Disk - 22nd April

If you take a look back at my recent full disks with the Lunt 50 there is a distinct haze and softness to the images.  I had noticed that visually there was a bright offset circular patch when looking through the eyepiece, this was quite clearly an internal reflection, and some clearish skies this afternoon allowed a bit of experimentation that led me to conclude there was a reflection between the ITF on the blocking filter and the internal optics of the Lunt 50.  Always the key to supressing a reflection is to use a circular polarising filter so I tried one on the nose of the blocking filter.  Immediately through the eyepiece I was pleasantly surprised how black the background sky was now, and also how much more contrast there was on the disk.  Exposure time was longer as might be expected, but still within what is acceptable at this image scale.  The resultant image is also sharper.  Taken with the Lunt DS50 and PGR Chameleon 3 camera.