I checked with Christian on this; here's his reply:

"The work of the book is advancing at a slow pace for a number of reasons. I think we will have it ready by the end of the first semester of 2020... We have included a lot of new stuff compared to the French version."

Hi Alexandra, I too think I prefer the old PST image, even though it is dimmer - it appears a bit more uniform. Just a thought - have you checked the ITF for rust? Replacing it in the older PST might give you a considerable bump in brightness. Better yet, using a Baader 35 nm Ha filter as an objecti...

Double stacking reduces the overall transmission of the filter system, but also removes the parasitic continuum from the photosphere itself. Both contribute to the overall perception of reduced image brightness, but vastly improved disc contrast. For two Lunt etalons in series with a transmission of...

Agreed Mark, Indeed it would theoretically be even smaller, since the FWHM of the PST is generrally closer to 0.1 nm, and a double stacked air spaced etalon is less than 0.05 nm; the Jacquinot spot is proportional to the square root of 2 x the FWHM.

Just visited with Brian at Lunt where this telescope is located... an impressive instrument when seen up close and personal. Objective has ERF coatings. Middle section has a large tilted precision polished optical window with additional ERF coatings. Open tube design in order to prevent build-up of ...

Just visited with Brian at Lunt where this telescope is located... an impressive instrument when seen up close and personal. Objective has ERF coatings. Middle section has a large tilted precision polished optical window with additional ERF coatings. Open tube design in order to prevent build-up of ...

That is indeed a rather old citation, and one must take most predictions with a grain of salt. One of the most respected sources for solar information is Dr. David Hathaway, who is now retired from NASA, but who maintains an active solar prediction interest with solar physicist Lisa Upton: We predic...

"Anyone ever tried placing a Coronado / Lunt blocking filter in a collimated beam to see if it trims down continuum leakage in the wings?" Hi Mark, not sure this would get much improvement. If the BF has a Lorentzian profile - just as with FP etalons - the main effect would be to improve field angl...

Did this with my Chameleon a few years back:

https://www.cloudynights.com/topic/3266 ... chameleon/

I would consider active cooling for about any camera employed during the day for solar imaging.

Very nice images Mark! What generation of SM90 do you have? Just an etalon/BF or the whole SM scope?

For your DS images I'm assuming you're using the telecentric version. Has anyone tried the Combo version for DSing?

Those appear to be either Newton's rings or FP etalon interference fringes: https://en.wikipedia.org/wiki/Newton%27s_rings https://en.wikipedia.org/wiki/Fabry%E2%80%93P%C3%A9rot_interferometer They could be an internal reflection issue with your imaging system, or there might be something amiss with...

No, not true. The "sweet spot," technically known as the Jacquinot spot, is generated by the field angles (and for the mica filters - instrument angles) produced by the optical configuration within which the etalon is placed. For collimator based etalon systems, it has little to do with the f ratios...

Good luck with your journey David - but I did want to get back to you about your question: " Fascinating Bob. So a question then, of the front mounted etalons on the market are some generally better than others e.g. Coronado vs Lunt vs Solarscope vs ?? Or do the variations in each make it pretty muc...

I have seen first hand that if something can go wrong, it will eventually actually go wrong - at least for someone. So when it comes to safety, I'm pretty conservative. I also believe there is a reason most solar telescope OEM's incorporate IR blocking as a safety AND liability issue. Here's a slide...

" Front mounted etalons are fickle and unreliable in terms of their performance - I have been through and own quite a few; a couple of them are lovely and flat, and show no banding etc due to needing excess tilt. Then there are quite a lot that do have banding and especially with imaging more so sho...

Hi Valery, I don't think it is valid to apply processing to only one image and not the other to come to a conclusion that the questionable filter has no faults. Under the circumstances of using identical scopes, camera, and processing to obtain the images, the significant differences between the two...

Hi Alexandra, I noticed you called yours a "Lunt CaK wedge." I'm assuming that means it's the B1800 diagonal, and therefore the diagonal mirror itself might be a part of the problem. If you are beyond the Lunt 5 year warranty and end up stuck with it (and since you likely do only imaging for CaK any...

You've covered all the bases David.

Front etalon(s) will generally give you the best performance - especially for full disc views/imaging, and of course will cost the most...

That's really very good Marty, and better than a lot of others I've seen with the more recently made filter systems.

Here's the skinny from Lunt: https://mailchi.mp/luntsolarsystems/join-us-at-neaf-and-double-stack-your-savings-save-10-off-gift-cards-starting-now-2205613?e=657ad57360 Intriguing for the ability to do "full disc" imaging - which indeed would require very large etalons to keep the Jacquinot spot larg...

Looks great George!

Marty, I would be very careful about compression Richview tuning. 1) The DS etslons sometimes are farther to the red wing, and may require more compression to come on-hand with no tilt. 2) Going to the blue wing could apply too much pressure, stressing or fracturing the ERF (there are no collimating...

I would try the SM40 on its own on another small refractor. Leave the tilt alone (e.g. no tilt) and use the Richview only (compression - tightening) to tune the etalon. Add the etalon to the pre-tuned PST, and tilt the etalon just enough to get the reflections of the disc far enough to get the full ...

I recall the general parameter for both external and internal filter tilts is about 2 degrees.

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