Solar H-a from today 18/09/11

[markt]

I use a SM60 double stack external etalon set-up on the ED80.

With the T max tuners on each filter, I've never had a problem with newton rings (NR)..

IMHO it comes from the interference behind the blocking filter between the optics and the chip.

Do you get NR with a straight camera connection to the BF??

I agree, NR definitely is definitely caused between the camera chip and an optical surface before it. I've never got newtons rings with the cam straight in the blocking filter, but as soon as either a barlow or powermate is introduced into the optical train NR become obvious, normally more so with increasing image scale.

NR definitely not caused with the 2 external etalons, however there are 'subtle' much broader scale banding pattern visible. It is subtle but there, I have reduced it by mechanical tweaks to the etalon hinge plates to make things as near perpendicular and parallel (as appropriate) as possible. But the CP removes these completely... A brief look online shows my CP has a transmission of 50% at 656nm (serves me right for buying it for £4 of fleabay) - however have discovered a £40 alternative with 95% Ha transmission; think will be getting one... You should give this a try Ken if you have alarge enough CP lying around... Mines just all rigged together with a series of step up/down rings...

Maybe, CP will work with NR? Maybe will just form another surface to generate them? OK, who's got a 1 1/4" CP and suffers from NR to give it a try...