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Possibly one of the last active regions of cycle 24? AR12757 ends january with decent activity for solar minimum. Taken by Marty Wise with his 8" SCT, Aries ERF and PST mod.

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Moving forward from solar cycle 24 to 25

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by Bob Yoesle
Fri Jan 17, 2020 2:12 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Meade / Solarmax Etalon Future?
Replies: 17
Views: 588

Re: Meade / Solarmax Etalon Future?

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?
by Bob Yoesle
Tue Jan 14, 2020 2:56 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Meade / Solarmax Etalon Future?
Replies: 17
Views: 588

Re: Meade / Solarmax Etalon Future?

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...
by Bob Yoesle
Mon Jan 13, 2020 7:49 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Meade / Solarmax Etalon Future?
Replies: 17
Views: 588

Re: Meade / Solarmax Etalon Future?

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 (...
by Bob Yoesle
Mon Jan 13, 2020 4:41 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Meade / Solarmax Etalon Future?
Replies: 17
Views: 588

Re: Meade / Solarmax Etalon Future?

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...
by Bob Yoesle
Sun Jan 12, 2020 9:58 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Meade / Solarmax Etalon Future?
Replies: 17
Views: 588

Re: Meade / Solarmax Etalon Future?

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...
by Bob Yoesle
Sun Jan 12, 2020 9:15 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Blocking filters and wintertime
Replies: 20
Views: 978

Re: Blocking filters and wintertime

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...
by Bob Yoesle
Sun Dec 15, 2019 3:53 pm
Forum: Solar Scope Modifications
Topic: D-ERF in converging beam?
Replies: 26
Views: 826

Re: D-ERF in converging beam?

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...
by Bob Yoesle
Sat Dec 14, 2019 4:27 pm
Forum: Solar Scope Modifications
Topic: D-ERF in converging beam?
Replies: 26
Views: 826

Re: D-ERF in converging beam?

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...
by Bob Yoesle
Fri Dec 13, 2019 4:01 pm
Forum: Solar Scope Modifications
Topic: D-ERF in converging beam?
Replies: 26
Views: 826

Re: D-ERF in converging beam?

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...
by Bob Yoesle
Thu Dec 12, 2019 5:50 pm
Forum: Solar Scope Modifications
Topic: D-ERF in converging beam?
Replies: 26
Views: 826

Re: D-ERF in converging beam?

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...
by Bob Yoesle
Wed Dec 11, 2019 1:32 am
Forum: Solar Astronomy Shop and Swap
Topic: "Astronomie Solaire" - New (French) book on Solar Observation now available
Replies: 28
Views: 3290

Re: "Astronomie Solaire" - New (French) book on Solar Observation now available

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."
by Bob Yoesle
Sun Dec 01, 2019 12:28 am
Forum: This is SolarChat !!
Topic: Coronado PST testing
Replies: 31
Views: 765

Re: Coronado PST testing

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...
by Bob Yoesle
Fri Nov 22, 2019 2:40 pm
Forum: Solar Scope Modifications
Topic: Removal of lunt erf double stack possible?
Replies: 3
Views: 496

Re: Removal of lunt erf double stack possible?

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...
by Bob Yoesle
Fri Oct 25, 2019 4:28 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Lunt monster
Replies: 14
Views: 1773

Re: Lunt monster

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.
by Bob Yoesle
Wed Oct 23, 2019 1:55 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Lunt monster
Replies: 14
Views: 1773

Re: Lunt monster

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 ...
by Bob Yoesle
Wed Oct 23, 2019 1:28 pm
Forum: This is SolarChat !!
Topic: When I win the lottery
Replies: 20
Views: 1536

Re: When I win the lottery

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 ...
by Bob Yoesle
Wed Oct 23, 2019 1:01 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Time for selling...
Replies: 11
Views: 876

Re: Time for selling...

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...
by Bob Yoesle
Mon Aug 19, 2019 9:57 pm
Forum: Solar Scope Modifications
Topic: Blocking Filter In a Collimated Beam?
Replies: 10
Views: 825

Re: Blocking Filter In a Collimated Beam?

"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...
by Bob Yoesle
Wed Jul 31, 2019 5:47 pm
Forum: Solar Scope Modifications
Topic: asi120mm-s DIY cooling
Replies: 6
Views: 742

Re: asi120mm-s DIY cooling

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.
by Bob Yoesle
Tue Jul 02, 2019 9:35 pm
Forum: This is SolarChat !!
Topic: Tuesday Morning Sunshine - 2nd July
Replies: 7
Views: 474

Re: Tuesday Morning Sunshine - 2nd July

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?
by Bob Yoesle
Sat Jun 15, 2019 5:34 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Help me to know what is that...
Replies: 3
Views: 541

Re: Help me to know what is that...

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...
by Bob Yoesle
Fri Jun 07, 2019 4:36 pm
Forum: Solar Scope Modifications
Topic: Relation between BF size and the PST Sweet Spot
Replies: 8
Views: 748

Re: Relation between BF size and the PST Sweet Spot

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...
by Bob Yoesle
Sun Apr 28, 2019 12:18 pm
Forum: This is SolarChat !!
Topic: Hydrogen Alpha Upgrade
Replies: 19
Views: 1145

Re: Hydrogen Alpha Upgrade

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...
by Bob Yoesle
Sun Apr 28, 2019 11:52 am
Forum: This is SolarChat !!
Topic: Photographic Benefits of UV/IR Blocking Filter
Replies: 10
Views: 769

Re: Photographic Benefits of UV/IR Blocking Filter

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...
by Bob Yoesle
Fri Apr 26, 2019 9:53 pm
Forum: This is SolarChat !!
Topic: Hydrogen Alpha Upgrade
Replies: 19
Views: 1145

Re: Hydrogen Alpha Upgrade

" 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...