Filter Woes

[martin_h]

I started on a HOO target the other night, Ha went perfectly, but the Oiii was terrible, every star looked like it had gone supernova! So I set about establishing focus but to no avail, no matter what I did I could not get anywhere near focus so I sent the filterwheel back to the luminance filter to check if the focuser was working ok, it was then that I heard a crunching grinding sound. I set about stripping down the filterwheel only to find that the retaining ring holding the Oiii filter had totally come undone and dropped off followed by the filter glass, hence the grinding sounds as the wheel indexed. As luck would have it the glass and coating are unscathed apart from one tiny scuff to a coating close to an edge.

After reassembly all is well but I did find another retaining ring very loose.

Its worth a check now and again people, that could have been a costly incident.

[Pete Presland]

A lucky escape Martin, i have never had that happen to me. Worth checking the filters occasionally, mine seldom leave the filter wheel.