Fantastic work, Stu, much interesting indeed.

Beautiful discs, Eric!

Thanks for your comments. Confirm, is the LS50 as it exactly fits in the M68 female thread on the focuser tube. A Baader D-ERF is in front of the objective.

Thanks Alexandra & Maurits. Here are the rear filters I used

Great comparison Stu. I have understood the train is B1800 --> Filter --> Barlow --> camera, am I right ?

Raf

Thanks to all in the meantime that small active region is now visible at E limb, I can't see if it is spotless or not

Returned to image the Sun after a long pause due to bad weather. A small equatorial active region is rotating into view however is still on the limb and today I could not see it yet. Few prominences were visible on the W and E limb while the disc was peppered with some minor plages and filaments. He...

great images, Eric, nice to see some activity around the limb.

There are signs of change coming from multiple approaches to the study of solar activity https://iopscience.iop.org/article/10.3847/2041-8213/aad1ed/meta https://www.sciencedirect.com/science/article/pii/S1364682617307009 https://www.swpc.noaa.gov/news/solar-cycle-25-preliminary-forecast let's wait ...

That graph is quite old now and was much disputed at the time. Current predictions for cycle 25th are quite promising

http://sidc.oma.be/silso/
https://www.nature.com/articles/s41467-018-07690-0

so better not to sell anything for the moment.

Thank you for your report, Alexandra, a joy to read. Or was this altitude 700m vs 2181m? I can't say nothing about your PST, of course, however every summer I take my solar equipment from Milan (200 m) to my home in the Italian Dolomites at 1600 m, I can assure you that the difference in terms of sh...

Fine, Marty, great images indeed!

Hi Magnus Quark chromosphere is very demanding in terms of seeing due the strong amplification factor of the internal telecentric, you need a fairly still air to obtain some decent results. Try on the morning or in the evening within two hours from sunrise or sunset respectively. As far the imaging ...

Very nice images, Brian, with fine details and contrast.

Great detail and very nice colouring, really impressive.

An apochromat is certainly not necessary, actually my preferred refractor for CaK imaging is a 80 mm f/11.3 TMB achromat. However a 115 mm achromat well corrected @393 nm would be too long, at least for my observing site. This apo is not only well corrected but also much more versatile.

Resuming this thread as I started calcium imaging with a 115mm f/7 Tecnosky triplet refractor. First results seem promising, the scope is better corrected than my previuos ones except the long focus TMB 80. If I am not wrong Peter Zetner obtained some very good images (better than mine) by using of ...

Great animation, Paul. I too experienced that kind of artifacts when wind or turbulence are strong. Sometimes I am able to get rid of the problem by selecting and stacking only few frames and/or adding some very large alignment poins in AS3! within the dark area.

Thanks for the detail. Unfortunately that Meade barlow is now difficult to find except in the used marked but I will try anyway. I tried yesterday to modify an airspaced meniscus Barlow but results were disappointing, no gain in contrast compared with the barlow in the original configuration. May be...

Interesting, thanks for sharing. It would be useful to know which brand is the Barlow you used because not all triplet barlows are equal. The spaced element of many triplets is a converging meniscus which is used mainly to correct the divergence of the marginal rays. However other triplets - some GS...

I think the graf you are showing for SCT spherochromatism in the blue end is way too exaggerated for optical engineers "blue" means the F line that is 486nm. At this wavelength SCs are still usable as one can see from the graph posted by Christian as well as in spot diagrams for SC. However CaK is ...

Absolutely fantastic, Stu.

Is there any tutorial for making animations with IMPPG ? Thks.

To my eyes negative 1 or zero seem the best, however I agree with Valery, send it back, no good.

Fine images, Mark. I too use my Quark to darken filaments through my Lunt-mod scope, my results depend much on finding the best matching tuning of both systems, not always easy to do.

Nice discs Alexandra. If the 100mm is the ED version it should be capable of doing much better than that in fine seeing conditions. I have it and in CaK or CaH is really fine at full aperture.