Christian also posted these fantastic images on CN. I replied with some links to articles on faculae and bright points that some may find of interest:

https://www.cloudynights.com/topic/7221 ... ry10404755

The larger "nosepiece" filters are ERF's, the smaller filter in the eyepiece holder is the narrow transmission CaK filter. So you would only need one of the "nosepiece filter" assemblies and two of the eyepiece holder filters in order to double stack the Lunt CaK modules. Lots of people have success...

What's the optical train in your filter Bob? I hear what you're saying about more energy coming through the L1. Hi Mark, I don't have it all worked out as of yet. I'm working with a double-stacked pair of PST CaK filters, and going from there. My primary goals are to 1 - reduce reflections, and 2 -...

In my home brew CaK module the Badder B CCD filter lets way too much off-band energy trough for my tastes (which seems to be converted to lots of heat), and the Astronomick filter would be worse in that regard. I'm now considering one of these two filters as an CaK module ERF, perhaps combined with ...

Hi H Mark,

Thought you might be interested in this thread if you haven't seen it already:

https://www.cloudynights.com/topic/6844 ... pe-sf70ds/

Ditto to what Alexandra has stated - with the caveat that if your single stack etalon allows significant background glow, faint prominences might be unaffected, if not even more visible, due to the suppression of this scattered light (i.e. poor transparency). This is especially true with front mount...

You might find this CN thread of interest:

https://www.cloudynights.com/topic/4809 ... on-basics/

So going a ways back in this thread here's the four element ~ 3.5 x UV Barlow corrector designed for the Celestron 9.25 by H. Rutten (yes, that Rutten), and it uses simple plano convex & concave COTS lenses which can be sourced from Edmund or other vendors. It might work well for other SCTs - especi...

For full-disc double-stacked views, and given you have stated you're "not concerned about the cost," I would recommend you not consider double stacked internal or external/internal set-ups, and go the 'full monty' of double stacked external (objective-mounted) etalons. These will give you overall th...

Hi DT6,

I do a lot of outreach in the PNW, feel free to PM me for advice or a gettogether. The only real issue now is the solar minimum and paucity of continuum activity. Otherwise you tailor your outreach to the age/audience.

Hi Marty, you can not rely on retail vendor advertising images to reflect the current model production. Many of them show previous generation models for the current version. I would stick to the manufacturers site for the correct image of the filter production - and this is not even 100% reliable.

Unfortunately, Christians' experience with Omega filters is also my experience. FYI - Not all blocking filters are 0.6 nm - it depends on the etalon and blocking filter generation. Some of the early Coronado BFs were closer to 0.2-0.3 nm, and the etalons themselves had a narrower FSR. Using a Lunt B...

Very nice references Christian :-) Bray and Loughhead noted the photospheric limb begins to manifest itself at +/- 0.65A off the center line, which seems to be essentially confirmed and refined by the higher resolution SST CRISP double stack to be +/- 0.6A. They also noted - and the CRISP images cle...

Hi Ken,

I suspect Meade is stating the physical diameter to the entire etalon plates, not the effective diameter of the reflective coated portion of the etalon itself.

Hi Christian, Very nice images! ;-) I'm thinking one or both of the filters is slightly off-band, and hence the double limb is still present. Alternatively, even at f35 you may not be getting the theoretical 0.5A and 0.6A FWHM of either filter, especially if your telecentric optics are not optimized...

There's the Celestron brand owners perhaps...

Wouldn't it be poetic justice if Lunt bought back their original patents and possibly production infrastructure for pennies on the dollar at auction?

Yes, exactly. At sea level, over 50% of the energy from the Sun lies in the near IR. The combination of the two ERF's essentially removes everything out to 2500 nm, where the atmosphere then blocks most everything beyond. Solar Energy Distribution.png The larger Solar Scope filters - lacking a centr...

Hi Rainer, It means I added a Baader DERF to the etalon assembly, which already included the Solar Scope OEM RG630 ERF with some IR blocking. DSF100 v SM90DS DERF comp.jpg The OEM Solar Scope ERF apparently has significant IR leakage, which exacerbates the thermal instability of the 100 mm etalons (...

Hi James, At 60-70 mm, an unobstructed etalon can perform quite well. But your minimally obstructed 60 mm will likely do just as well, and the wavefront effects of the obstruction will likely be indistinguishable from an unobstructed etalon, especially given daytime seeing rarely gets to diffraction...

It does quite well but I never have liked the idea of the central obstruction it has in the light path. A refractor should be unobstructed. An etalon is a filter, not a telescope. Etalons are quite sensitive to thermal variations of both the gap spacers and etalon plates themselves. A central (or o...

My gut is telling me that the original Coronado blocking filters may have been a bit more temperature stable. Then again I'm a lightweight and don't really enjoy cold weather observing in the middle of deep solar minimums, so my experience level may not be valid. The OEM's face a tough niche competi...

Just as a FYI, Brian Stevens at Lunt did mention the issue of tube currents was one of the reasons their 30 cm scope uses a open truss design. The other issue I want to highlight is that etalons are very sensitive to temperature changes. My Solar Scope DSF100 etalons suffered greatly from thermal in...

Hi Ken, You are of course correct in that 18 W in remains the same (conservation of energy), it is the energy density per unit area which has increased ~ 188 times at the focus. Therefore the 18 W falling over the surface area of the objective can be converted to heat through warming would be equiva...

Now I am seriouly beginning to wonder whether I wasn't cooking my old ASI120MC when it began to show a film of solar-surface like artefacts in the field of view. Though it seems unlikely given the Maier ITF and PST IBF5 in series. Is this likely given the extreme exposure in my case? I doubt it, as...

I have discovered some serious downsides: A hot exit beam from the empty focuser despite the D-ERF! This suggests the PST etalon is being baked for hours every day when I am imaging all day. Quite often! The smaller D-ERF is also being cooked by the same converging beam. A fierce, re-focused beam j...