Reflections/diffraction?

[martin_h]

Got an interesting effect last night imaging the Pleiades, got a Bahtinov mask diffraction spike - and no I didn't have one on! I havn't got one for this scope. and its a refractor! so I dont know where it came from.

[Catanonia]

I get the same sometimes with the ED120 on very bright stars such as these.

When i posted it, people though it might be the lens clips causing it.

[glennbech]

On bright stars I sometimes get a "dent". Almost like an inverted spike moving a bit into the star. I have a megrez 90. Never seen anything like that

[davew]

That's interesting, in a strange kind of way. If it was as Cat said, I would have expected the spikes to be equidistant as they are usually set at 120* from each other. Also one of them must be intruding into the light path a long way due to it's length.

The only thing I can suggest is that you take the camera off and get your eye up to the rear of the tube and have a look. Maybe try this with the scope pointing at a white wall.

Is there anything else ie in the camera that is intruding ? What camera were you using ? Any filters ?

Dave.

[martin_h]

Nothing else intruding that I can see, the camera is the QHY8 and a LP filter....It doesnt bother me as its only shown up on that one set of images, but interesting none the less for the Bahtinov mask diffraction spike effect!