At 150 mm you really do need something beyond the 2 inch UV/IR type of filter... Go with Valery's Tri-band filter for the most versatility. If you only want H alpha, the Baader DERF would work as well. Avoid the simple red or yellow glass absorptive objective ERF's. See this recent Cloudy Nights pos...

Thanks Bart, nice to see in the comparisons!

"Personally, no. Lots of people on here have tried the telecentric / air spaced etalon route and it yields results with too wide a bandpass." I would expect that, since 0.7 angstrom air spaced etaons were originally intended for use on the front objective, where the 0.25 degree field angle of the Su...

Thanks for the trials you gone through Bart! Could you post or PM me the image trials of the filter combinations? Just curious to see all the results for the comparison...

Hi Marty, In some of your most recent images I'm seeing just a hint of the double limb, which is not obtrusive. In others I'm seeing processing artifacts, not the double limb of the photosphere: M Wise highlight.jpg Note the irregular hard edge appearance all along the limb and at the indicated loca...

"I think as we become more seasoned and experienced solar observers our expectations in terms of how even the illumination of our filters are gets higher. I think back to some of my earlier setups and the illumination of the etalons and while I was happy then I wouldn't accept it now." Hope the new ...

Hi Bart, Wonderful images! The Baader 0.4 reducer is the "research grade" to mate with the TZ3 and restores the original f ratio / EFL of the system. Haven't had a chance to use it yet but looking forward to when the weather improves. Looks indeed like we're on the same path... The Chroma Tech CaK f...

ED 80 might be better for the CaK, but hard to say w/o having accurate data.

You set up sounds like it will be ideal. Two thumbs up!

Awesome and beautiful scope Mark, and the contrast uniformity looks great. I'm assuming it uses an internal 60 mm filter for minimum field angle magnification. It sounds like the front etalon you tried was a dedicated DS filter, and apparently required excessive tilt. I experienced this with a 60 mm...

Precise Parts in Miami is your ticket Marty:

https://www.preciseparts.com/ppmain//index.html

Production cost and demand realities are what they are.

But I don't think CaK will become a unicorn, dino-dodo, etc. It seems DayStar has (and perhaps SolarSpectrum as a custom order) and will likely keep the CaK option available in the mica based etalons.

Now you're cooking Marty! Pretty much right on band to me. The normally processed greyscale bright and dark mottles look exactly as they should, and there is no discernable double limb.

Thanks guys, I guess I'll give a little more time for a response, and then try again. Mark, it sure looks like a Baader T2 device, but I looked at their site and didn't find this particular implementation. So I'm hoping to hear back from Astrograph... Seems like it would be ideal for a modular syste...

Very cool Bart. I'm looking at a total redesign of my CaK module, but hitting a roadblock with filter mounting implementation with some ability to tilt multiple individual filters fairly close together. I found this nifty tilt adapter which seems like it would be perfect, but it says "not in stock,"...

I have been struggling to get my 2 point grey cameras to work with Firecapture recently and so I don't fancy another to add to the pile... I recently had the same problem with my PGR Chameleon, downloading the latest SDK fixed this - it might get your current two PGR cameras working again. BTW thei...

Thanks Mark - I was lucky to be able to get these etalons when such quality was available and still relatively affordable. I should note that the above images were wavelet processed in RegiStax6, but had no additional post processing, and the their RG630 ERF's were replaced by a single Baader DERF f...

... you can get this chip in ZWO, PGR and Basler versions, does it make any difference? Just an FYI, A couple of years ago I fried my Point Grey Chameleon's sensor when the Baader film filter I made intermittently partially blew off in the wind. Point Grey replaced the entire camera for a standard ...

One thing I do notice is that depending on the processing I can "pull" the double edge out of almost any image... Hi Ken, For me it was a long learning curve to discover exactly what an on-band image should look like. I still have trouble at times, especially in the typical relatively poor seeing I...

Hi Marty, Upon reflection and going back to some references, I believe there could be a couple of things going on with your images. The recent images are better with regard to the double limb, but it is still subtly revealing itself. According to Bray & Loughhead in The Solar Chromosphere (1974, pag...

Not until reading Bob Yoesle's writings about the dreaded double limb did I realize that it was undesirable and must be eliminated. Yes, it's true - apparently a cult of righteous Double Limb Slayers has developed and is dedicated to eliminating for all mankind the dreaded Double Limb! Double Limb ...

Some would say no, and that it's over-kill, but I would go full-aperture for the best IR reduction. Depending on the scope mechanicals, you could also consider an internal ERF such as a smaller ~ 100 mm or so Baader, BelOptik, or Lunt ERF placed within the OTA. I also would consider a 50 mm KG3 filt...

These are a major improvement Marty! Very much closer to being on band I would say.

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...