Lunt driving me mad

[Dawson]

I have a 50mm Lunt with a double stacked etalon on the front (LS50FHa) and B600 diagonal, pressure tuned; currently using an ASI ZWO 174MM non-mini with IR cut filter. For the life of me I cannot get an evenly illuminated disc of the Sun on any chip. I’ve tried single stack, tilt adapter(s), different cameras. There is no sweet spot where there is even illumination. I feel as though the blocking filter is too narrow, else something else is amiss. It was a second hand scope and the details it reveals are amazing, but even illumination is impossible. Lunt talked me through various things to try, but nothing has solved it. Do you think the B1200 filter would fix it? Unfortunately I don’t know anyone with one to try. Else is it unlikely the blocking filter and time to just get a new solar scope and stop wasting my time and surges in blood pressure 🙂

Thanks.

James

[Dr Paul Leyland]

May be cheating, but have you tried using a pseudo-flat to even out the illumination?

[Dawson]

I’ve not. Invariably this scope is set up outside so tracking is usually awful. I just feel there is somethign fundamentally wrong and I’d like to resolve it one way or another.

Thanks.

James

[Dawson]

This is from today. The gradient in brightness is not a natural feature, it is artefact.

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