Very Nice - detailed and contrasty - especially for SS.

Looks like you nailed it Mark! Your greyscale is perfect:

https://www.flickr.com/photos/brierleyh ... otostream/

Hi Marty, "... and if that kills the double limb, I'd be happy with that for the time being until I can figure out something better that is affordable." What do you consider affordable?! "Better" H alpha performance (especially double stacked) and "affordable" is kind of working at odds with each ot...

Very nice implementation George! After the Quark, you are over f/30 and don't need the lenses. RE: PST etalon. Remember, an air spaced etalon is a different beast than a solid spaced etalon, and suffers from the decreased refractive index of air compared to a solid spaced etalon, and field and instr...

Hi George, If I were you, I'd just add the PST to the Lunt as described, and get a pre-filter attached to the front of the Lunt module for larger aperture use: https://www.edmundoptics.com/p/394nm-cwl-50mm-dia-hard-coated-od-4-10nm-bandpass-filter/19839/ or https://www.edmundoptics.com/p/390nm-cwl-5...

I'm on 3G speeds with my air card (I live in the boonies), so even if I shaved it down, it would take a long time to upload some where. But I'd be willing to try something if you have any ideas on how to best shave it down without culling good data. HI Marty, Don't really have any suggestion other ...

Hi George, I think the Baader B-CCD is an all dielectric reflection filter on a clear BK7 or similar substrate, not an absorption filter. My CaK system has and continues to evolve. And I have only done this for CaK imaging use. Many years ago I and a few others started with a Baader Blue CCD filter ...

Hi Marty, Much improved! Yeah, you still have a little double limb. Could be a PST etalon tuning issue. And to my eye still a little soft towards and at the limb - but still much better ;-) How big is the above double stack video file? Perhaps if you can uploaded it to Dropbox, I could download it a...

I agree Mark. I use minimal gamma in my capture process, generally underexpose, and bring out almost everything in post-capture processing. Marty PM'd me about this possibly being a double limb issue, but it doesn't look like it to me. The last image looks pretty good at the center of the disc, but ...

"Painted the inside of the OTA with Berger Antireflexfarbe."

Unfortunately, can't be delivered to the States. Anyone know of a similar product available in North America?

Ditto to what Mark has said ;-) Here's a little more detail as to why: All etalons are sensitive to the angle of light passing through them, and theoretically perform best with only parallel light passing at a 90 degree angle ("normal") to the reflective elements. The Sun, being an extended object i...

"If an airspaced etalon is just two pieces of partially reflective glass contacted between mica spacers..." Not quite Apollo! Polishing to lambda/100 flatness across 25 mm is not too difficult using relatively standard production techniques, achieving this over the full area of a larger filter becom...

As shown in Ken's pics, and as in the above Cloudy Nights link, the Lunt issue now appears to be "glass disease:" https://en.wikipedia.org/wiki/Glass_disease See the Stage 1 and Sage 2 descriptions. It is known the Lunt uses BG glass (verses an ITF), which is a simple soda lime glass. It seems the K...

Hi Bart, No doubt a killer deal, as the filter itself is probably worth 10 times the price advertised. I have 3 BF 30's and they all have different brightness levels. Sometimes darker is better... Your proposed ancillary filters should work well, as the DERF will block UV and near IR, the 35 nm H al...

I checked out this filter as well... The Isle of Man blocking filters were designed for an etalon with a higher finesse and narrower FSR than the later Coronado or Solar Scope etalons. As opposed to today's Coronado and Solar Scope BF's with about a 6-8 A FWHM, the one in question probably has a 2-3...

" Here are the simulations for a re-spaced classic C8 :
http://astrosurf.com/viladrich/astro/in ... -Plate.htm "

Thanks so much for this Christian!

Hi George, I don't know if you saw these, but here's my recent results using a $350 Chameleon CCD camera. I already knew from a few years ago that double stacking CaK filters provides a contrast improvement. Triple stacking CaK filters is useful for bringing out details near to the solar limb. The s...

Without the optical prescriptions of the lens system, it is impossible to know. The respaced SCT corrector probably does a better job of coma reduction, while I believe a separate system would be required for chromatic spherical aberration correction at 393 nm. For CaK work, the PST filters will be ...

Hi Christian, It's the standard (not the Edge-HD) C8. Any chance you could "cook up" a spherical aberration corrector using COTS fused silica len(es) from Edmund, Thor Labs, etc? That seems like it would be an ideal CaK imaging platform and relatively less expensive compared to a custom CaK refracto...

Hi Christian,

Thanks you very much - that would be wonderful :-) I have seen your C14 re-spaced write up and have purchased a carbon fiber tube towards the implementation...

Hi Valery, Do you have a transmission plot for the C8 DERF? I also would like to know the physical dimensions, and if it is possible to put a central hole in the filter. I'm considering a re-spaced SCT mod and would prefer to mount the secondary mirror to the DERF if it could be made to replace the ...

Thanks for that Peter ;-) OK, so now we add a sounding rocket to the equipment list: https://www.youtube.com/watch?v=sQw_C5KLhFM Alternatively, one could always move to Antarctica: Solar-Spectrum-GballEditz.png https://www.youtube.com/watch?v=fzN0LbZXX1s&feature=youtu.be But you'll probably also nee...

An interesting research paper - thanks for sharing it Valery. "If one will go this way, he should not save money on a too small telescope. 100mm is a minimal size I would say. Minimal SA is a must for such a telescope. A must have also a SSM. The main price driving factor is an etalon with a 0,5A ba...

Hmmm - this is a notch filter (not bandpass), hence the NF prefix. What would it be useful for in a CaK solar filter?

Hi Dano, If at all possible, for whatever you decide to buy, make sure you can return it if you are not pleased with the performance. Even the very most highly regarded manufacturers can have a lemon slip through, and with commercial production pressures, overall quality has seemed to slip from what...