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Transit of Mercury in the Spicule Layer. Phil took this great image with his Quantum 6 Scope, Solar Spectrum etalon and PGR Camera.

Welcome to Solar Chat! The best forum for Solar Astronomy
Moving forward from solar cycle 24 to 25

Search found 47 matches

by langleif2
Thu Oct 17, 2019 5:30 pm
Forum: This is SolarChat !!
Topic: 11" SCT for imaging at 393nm.
Replies: 17
Views: 493

Re: 11" SCT for imaging at 393nm.

It seems almost unbelievable at that image scale without some kind of corrector. But a German optical solar expert once said to me he didn't believe the plot about spherochromatism for a SCT because the aberration should only be a 1/4 wave from 550 nm. Then it would perhaps match the image given. Or...
by langleif2
Wed Oct 16, 2019 10:20 am
Forum: This is SolarChat !!
Topic: C11 CAK Images on different days, New, added 16 Oct images
Replies: 18
Views: 336

Re: C11 CAK Images on different days, New, added 16 Oct images

Nice images, Alfred, especially the first one. Impressive with a 11" SCT. Maybe you went "lucky" with your SCT being a little undercorrected. But you will most likely never get a sharp picture with the SCT whatever the seeing in this wavelength particularly at high mag. In this plot you can see why:...
by langleif2
Tue Oct 15, 2019 5:32 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Time for selling...
Replies: 7
Views: 380

Re: Time for selling...

Yeah, it's old data but perhaps still viable, because are the gauss measurements for the last years still declining? Also solar seismologists should see the startup of the jet streams that will cause Cycle 25. But so far (old data), there is no trace of them in either hemisphere, as shown in the dat...
by langleif2
Tue Oct 15, 2019 8:42 am
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Strehl ratio for a Celestron C11
Replies: 7
Views: 241

Re: Strehl ratio for a Celestron C11

C8 with full aperture Aries D-ERF. You can also take a look at https://solarchatforum.com/viewtopic.php?f=10&t=25125&start=25#p239889 and get the story behind the Barlow. Now I'm waiting for a nice sunspot to appear and for winter so I can try it on Venus. In the first place I experimented with a Sk...
by langleif2
Mon Oct 14, 2019 8:16 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Strehl ratio for a Celestron C11
Replies: 7
Views: 241

Re: Strehl ratio for a Celestron C11

While I like CaK pictures done with a refractor it's possible as mentioned to correct the Schmidt plate for spherocrhomatism in the CaK wavelength. I made a modified Barlow to do this and it worked out successfully despite I by accident flipped a lens. At 2nd of oct I took this picture of AR2749 and...
by langleif2
Mon Oct 14, 2019 7:41 am
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Time for selling...
Replies: 7
Views: 380

Time for selling...

I would say sell your solar gear while there is time. The average magnetic field strength in sunspot umbras has been steadily declining for more than a decade (don't know about the last years, though) NN_Sep11_Sungraph_400px.jpg Where the field is less than 1,500 gauss, spots do not appear at all. I...
by langleif2
Wed Oct 09, 2019 2:57 pm
Forum: Solar Scope Modifications
Topic: PST modification - idiots guide
Replies: 28
Views: 907

Re: PST modification - idiots guide

As mentioned, you don't need the helical focuser. Especially if you want to remote control the focuser. You just need a back adapter or extension tube at the length of 14cm as seen on this picture: Assembled%20Tube%201.jpg Eventually you can take a look at my thread: "Is a C8 and a PST mod really us...
by langleif2
Sat Sep 28, 2019 5:59 am
Forum: This is SolarChat !!
Topic: A small flare on a quiet sun. 280mm scope
Replies: 14
Views: 393

Re: A small flare on a quiet sun. 280mm scope

Outstanding! It's like looking at a Ha picture from the Dutch Open Telescope.
by langleif2
Fri Sep 27, 2019 1:17 pm
Forum: Solar Scope Modifications
Topic: A big solar newton for ultra narrowband imaging, possible?
Replies: 30
Views: 1138

Re: A big solar newton for ultra narrowband imaging, possible?

Hello langleif2, This is a textbook example of loss of information in a communication process : A tells a story to B, which B repeats it to C, etc. After a short while the story becomes quite another story :-) So here the actual story : Every year, we have a solar gathering at Serbannes (France). N...
by langleif2
Thu Sep 26, 2019 5:42 am
Forum: Solar Scope Modifications
Topic: New CaK filter assembly.
Replies: 5
Views: 306

Re: New CaK filter assembly.

Nice looking disk. There's not much going on. With apertures 40-80mm you don't need an ERF, the filter it self acts as an ERF so belt and braces really.
by langleif2
Wed Sep 25, 2019 7:47 am
Forum: Solar Scope Modifications
Topic: PST modification - idiots guide
Replies: 28
Views: 907

Re: PST modification - idiots guide

Aries triband DERF. So I use the Baader 35nm H-alpha filter in front of the etalon. It's safe and will reduce temperature to about 40 deg C.

When using my PST CaK mod I don't need a suitable filter in front because the CaK filter rejects the excess radiation itself.
by langleif2
Wed Sep 25, 2019 7:36 am
Forum: Solar Scope Modifications
Topic: PST modification - idiots guide
Replies: 28
Views: 907

Re: PST modification - idiots guide

Just curious, with an ERF in front of the C11, why add another HA filter in the back? Assuming the ERF is going to cover UV and IR and most of the visible (simple red glass will not). Is the PST etalon particularly sensitive? By the time you get to the blocker, the etalon comb filter gets rid of mo...
by langleif2
Mon Sep 23, 2019 6:45 am
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

Okay then, I'm excited to hear because the EgdeHD is a different beast from the standard SC, but to my knowledge the Schmidt plate should be the same. If working you are in for a surprise. It's literally going from myopia to wearing glasses if seeing collaborates. I've also been looking at the 2.5x ...
by langleif2
Sun Sep 22, 2019 7:12 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Experimenting calcium imaging with small refractors
Replies: 49
Views: 5081

Re: Experimenting calcium imaging with small refractors

Btw, I found in the EO catalog these special corrector plates but I have no experience with them.
https://www.edmundoptics.com/f/spherica ... tes/14001/
Could be used with SCT systems as well, I guess.
Not cheap :|
by langleif2
Sun Sep 22, 2019 5:14 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: Experimenting calcium imaging with small refractors
Replies: 49
Views: 5081

Re: Experimenting calcium imaging with small refractors

Not that you need a TOA or even an apo. A long Fraunhofer is actually a good choice for CaK, when looking at the chart for chromatic and spherochromatic aberration: Aberration.jpg Some of them are a little undercorrected from the factory. I did this photo years ago with a simple Skywatcher 90mm f10:...
by langleif2
Sun Sep 22, 2019 2:28 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

Ok, can you show the design? Did a video today in the afternoon with my Barlow mod. There is some aberration in the corners when the barlow is not perfectly aligned, but overall good performance especially seen on a screen. Sun0011_g4b.jpg Not that I really like the CaK in a SC mainly because of the...
by langleif2
Sat Sep 21, 2019 4:14 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

Okay, I don't think it matters much. While not an optical designer a triplet Barlow with an air space in a typical design will have a bi-concave lens and a cemented part whether it is a plano-concave best form lens in case of the Meade or a meniscus in another design. The resulting outcome when incr...
by langleif2
Sat Sep 21, 2019 7:32 am
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

Hi, Marty It's really straight forward. All information is given. You can use all triplet barlows with an airspace. However, the magnification will depend on whether it's a long type or short type of Barlow. You just need to increase the airspace about 8-10mm or so at least for the long type. I did ...
by langleif2
Fri Sep 20, 2019 1:08 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

No one seems to make a suggestion for a "work-around" solution to the sphero-chromatism inherent in the Schmidt plate. Of course, custom solutions are there, but rather too expensive. In my stores I found a so called apo Barlow I never found any use for. It's a triplet with an air gab, a cemented pa...
by langleif2
Thu Sep 19, 2019 2:26 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

Yes, temperature is the key here with the long tube Newton. I can't think of any other reason. But it's not useless, you need to do an open structure for the Newton so the heat is going else were and you will notice a better performance. And a CC or RC is the right "weapon" in this short wavelengths...
by langleif2
Thu Sep 19, 2019 6:11 am
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

Hello Marty Thanks for the update. What you are experiencing with the long Newton is most likely thermal turbulence. You are letting in radiation in a long tube that at near focus will be around 70 deg Celsius at least! That's my temperature measurement with the DERF and a SCT at the exit hole nearb...
by langleif2
Wed Sep 18, 2019 7:59 am
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

No one seems to make a suggestion for a "work-around" solution to the sphero-chromatism inherent in the Schmidt plate. Of course, custom solutions are there, but rather too expensive. In my stores I found a so called apo Barlow I never found any use for. It's a triplet with an air gab, a cemented pa...
by langleif2
Mon Sep 16, 2019 8:44 am
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

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 ...
by langleif2
Mon Sep 16, 2019 8:38 am
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

Hey, that's a fine picture, Valery, but it's not sharp even when using sharpness algorithms. There are some spherochromatism and it's getting severe quickly below that F-line. That's why a Newton and a classical Cassegrain is way better below 450nm. It can be done to some extent as you pictured, but...
by langleif2
Sun Sep 15, 2019 3:36 pm
Forum: Commercial Solar Filters/Cameras/Hardware
Topic: What do you think is the most versatile high resolution solar telescope design?
Replies: 43
Views: 2558

Re: What do you think is the most versatile high resolution solar telescope design?

Hello Christian, I see you linked to the reference, the telescope "bible", Telescope-Optics.net. Very well, there you can read on SCT spherochromatism: "In general, SCT spherochromatism is low. For a typical commercial ~ƒ/2/10 version, with both mirrors spherical, k~0.25, σ~0.4 and m~5, relative cor...