Options for high resolution?

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Options for high resolution?

Post by Helen »

Hi All,

I hadn't done much solar imaging for a while, but have recently got some mojo back :cool:

I have a variety of nice kit! gathered over 10 years. My highest quality is a 70mm solarscope filter set which I use with a borg 71 scope. I've also got a LUNT DS 50mm filter set with a 1200 bf. My Quark seems to have died so I need to get that sent back. I also have the bits for a pst mod, although the bf10 I bought doesn't seem to be performing. To finish off I have a Cak 600 diagonal.

I've got some significant Christmas/birthday money available and am wondering about putting it towards getting a high resolution rig. The pictures on here from RCT/SCT are inspiring! I've got a C11, an old C8 and a 125 etx Mak.

So..... what might my options be???

Thanks
Helen


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Re: Options for high resolution?

Post by MalVeauX »

Hi Helen,

Depends on budget.

Depends on your local seeing conditions too. Going high res is not as simple as getting the gear. Your seeing really needs to support it or its a time sink with very little fruit. If your daytime seeing is rather excellent, or you're willing to be very patient with a solar scintillation monitor (SSM), it's something to explore.

You could take a refractor from 100mm to 150mm with a Quark and have excellent resolution without the need of expensive D-ERF's.

You could take anything like a SCT/Mak and put a full aperture D-ERF on it and slap a Quark behind it, or something better, like a Quantum, etc, or you could go with a PST etalon or even a Lunt etalon option as a modification if you're willing to risk it.

Very best,


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Re: Options for high resolution?

Post by Valery »

Hi Helen,

I can help you with any DERF be it 150mm, 214mm (C8) or 295mm (C11). With 11" scope you can imaging with 9", 10" and 11" apertures as I doing in my practice. And I do not use a Solar Seeing Monitor, I have a bit of patience to hunt for the seeing during an 60-90 min in a morning. My location and local seeing is nothing special, especially in night time. But morning or early morning there is a certain time with atmosphere equlibrium and this is the time for really high res imaging. Later then only 80-100mm apertures can work with good chances for full resolution for a given aperture. A similar period of atmosphere equilibrium can happen before sunset.
And such atmosphere equilibrium is a common event for absolutely most locations on the Earth. At some locations these equlibrium periods are longer, at others they shorter, but they always happen.
But in a cloudy days with lower temperature changes it is possible to catch "windows" between the clouds and meet an excellent seeing in any part of a day.

Recent Alexandra's and Stue's takes with their 11" and 10" telescopes show that even at such nothern latitudes like England, there is a seeing for high res imaging. If to do this more or less systematically and with a SSM aid, the chances for excellent images should be solid.
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Re: Options for high resolution?

Post by christian viladrich »

I would say basically the same as Marty and Valery,
A 100-150 mm refractor is very easy to set up and operate. This is no need to check collimation. Usually, the seeing is fine with this range of aperture.
With a 200 mm and above, you will be more dependant on seeing condition, proper collimation, etc.
So it could make sense to start with a 100-150 mm refractor to get familiar with your local seeing conditions.


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Re: Options for high resolution?

Post by marktownley »

christian viladrich wrote: Thu May 02, 2019 11:44 am A 100-150 mm refractor is very easy to set up and operate. This is no need to check collimation. Usually, the seeing is fine with this range of aperture.
With a 200 mm and above, you will be more dependant on seeing condition, proper collimation, etc.
So it could make sense to start with a 100-150 mm refractor to get familiar with your local seeing conditions.
I plan to add a 120-150mm scope to my arsenal. I am wasting my (infrequent) time with my 8" HaT all too often sadly due to my seeing conditions...


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Re: Options for high resolution?

Post by Starry Jack »

Wow. That says a lot coming from a pro like you. Makes me feel more content pursuing optimizing my 152mm.

Tomorrow I test out going from f22 (Barlow) to about f15. I'm hoping the PST stage one Sweet Spot is minimized while still getting lovely medium res details.

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Re: Options for high resolution?

Post by Valery »

Starry Jack wrote: Thu May 02, 2019 5:40 pm Wow. That says a lot coming from a pro like you. Makes me feel more content pursuing optimizing my 152mm.

Tomorrow I test out going from f22 (Barlow) to about f15. I'm hoping the PST stage one Sweet Spot is minimized while still getting lovely medium res details.

Jack
With a PST Mod-2 a 150mm refractor will provide about 1/4 of solar disk diameter within Ha. Quite enough for impressive med res images. And with a C8 the useful FOV will be about 1/5 of the solar disk - enough for high res good images.


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Re: Options for high resolution?

Post by Helen »

Thanks for all the advice and suggestions everyone 🙂

I live in Wales, which is not known for its astro-friendly weather! I live about 800 ft above sea level, my seeing can be variable. On the upside, I work a lot from home, and could set up a larger Solar scope in my observation to be ready at short notice. At the moment I just set up as and when, but my set up is light enough to carry in one.

I could easily start with larger refractors, Indo like their simplicity. I have a Tak 100DC 740fl, which when used with the 90mm derf would be about right for the PST mod. I would need to sort out the bf problem or get a new one - or alternatively would the Lunt 1200 be work? Or would a pressure tuned Lunt mod be a better option?

I need to get the quark fixed if possible!

Going larger... My main imaging scope in the obs is a wo123flt, but is this an excuse to get a 150 scope....😉 With these scopes and a quark or a quantum would I need a front derf?

And I suppose I need to ensure I have a camera which matches the resolution..

Sorry for all the question!

I’m getting excited about the possibilities 😎

Thanks!
Helen


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Re: Options for high resolution?

Post by MalVeauX »

Hi Helen,

The difference between a triplet/doublet APO and a basic doublet Achromat for this purpose will be insignificant, so if you're interested in a 150mm refractor, I would get any of the F6~F8 varieties that are achromats and put a good linear bearing class focuser on it to hold a heavy imaging train. You do not need a full aperture D-ERF for this, and you can use an internal sub-aperture D-ERF (such as a Baader Red CCD-IR Block Filter). A full aperture D-ERF is nice to help keep most heat out of the OTA, but again, it all depends and it may be ok without it (A Quark can be used with up to 150mm without a full aperture D-ERF, but lots of factors contribute to whether or not localized seeing conditions are a factor). All mods come with gambles in terms of everything lining up nicely and requiring adapters and other fittings to make it all marry together and mods using a PST, Lunt etalon, etc, will need a D-ERF as they are not behind a blocking filter of any kind in these modifications. A Quark on the other hand can be used this way without any modification and without any adapters. So a 150mm achromat + Focuser + Quark Chromosphere + 0.5x focal reducer + IMX174 based CMOS camera will work right out of the box without modification, no collimating, no fuss. Leave it set up and ready to go, and target your best seeing moments and you're set.

Very best,


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Re: Options for high resolution?

Post by Valery »

MalVeauX wrote: Sat May 04, 2019 1:59 am Hi Helen,

The difference between a triplet/doublet APO and a basic doublet Achromat for this purpose will be insignificant, so if you're interested in a 150mm refractor, I would get any of the F6~F8 varieties that are achromats and put a good linear bearing class focuser on it to hold a heavy imaging train. You do not need a full aperture D-ERF for this, and you can use an internal sub-aperture D-ERF (such as a Baader Red CCD-IR Block Filter). A full aperture D-ERF is nice to help keep most heat out of the OTA, but again, it all depends and it may be ok without it (A Quark can be used with up to 150mm without a full aperture D-ERF, but lots of factors contribute to whether or not localized seeing conditions are a factor). All mods come with gambles in terms of everything lining up nicely and requiring adapters and other fittings to make it all marry together and mods using a PST, Lunt etalon, etc, will need a D-ERF as they are not behind a blocking filter of any kind in these modifications. A Quark on the other hand can be used this way without any modification and without any adapters. So a 150mm achromat + Focuser + Quark Chromosphere + 0.5x focal reducer + IMX174 based CMOS camera will work right out of the box without modification, no collimating, no fuss. Leave it set up and ready to go, and target your best seeing moments and you're set.

Very best,
Marty,

About two and hald years ago I asked Andover Corp. if they can recommend to place their blocking filters (used in Quarks) at very near to the focus of 150mm F/5 and F/6.5 achromats. Their answer was NO, absolutey not recommended! These filters are not hard coated and can quickly degrade or damage at such a conditions. They cost $625 - a great part of a 150mm DERF cost.

In the focal plane of a 150mm F/6.5 objective the sun energy density is about 600x higher than at a direct sun ligh unfocused.
You can easily melt a piece of plumbum in the focus!

In the case of 150mm F/5 objective it higher nearly in 900x! In the case of 150mm F/8 objective it higher in 185x.

Note that energy density in the focus of C8 is only in 80x higher than at a direct unfocused sun light. But would you recommend to use a C8 + Quark without front DERF?

Day Star finally starts to recommend to use front DERF for 5" and 6" telescopes. :)


Valery


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Re: Options for high resolution?

Post by Dennis »

what about cak, can it be done with an c8 edge hd? or will the internal correctorlens make results worse than with standart c8?
anybody doing this succesfully?


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Re: Options for high resolution?

Post by Valery »

Dennis wrote: Sun May 05, 2019 8:50 am what about cak, can it be done with an c8 edge hd? or will the internal correctorlens make results worse than with standart c8?
anybody doing this succesfully?
I doing CaK imaging regularly even with C11 with achieved resolution in 1,7x higher than in Ha with this same telescope.
And in the UV continuum as well.

In the C8 things are easier.


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Last edited by Valery on Tue May 07, 2019 4:24 am, edited 1 time in total.


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Re: Options for high resolution?

Post by MalVeauX »

Dennis wrote: Sun May 05, 2019 8:50 am what about cak, can it be done with an c8 edge hd? or will the internal correctorlens make results worse than with standart c8?
anybody doing this succesfully?
I do not recommend the C8 Edge, or any SCT, for 393nm specifically. Can it be done? Sure. But frankly, you'll only see limited results. While my evidence is anecdotal, the opposite is true of evidence for it, also quite anecdotal. I have successfully imaged at 393nm with my C8 Edge. However, it's not great. To appropriately sample, it requires really excellent seeing and depending on pixel size, requires a significantly longer focal-ratio than the longer wavelength frequencies such as Ha to best critically sample. It just puts a lot of demand on good seeing. More so than 656nm. I've put a lot of time on my C8 Edge's mirror in 393nm, with and without a SAFIX, and it really is just not a good instrument for 393nm. My cheap 150mm achromat crushes it effortlessly for correction and resolution at this wavelength.

You are far better off with a 6" refractor for an "all wavelength" approach. Or, for cost, a quartz mirror long-focal ratio parabolic reflector mirror, such as a 200mm F6 or 200mm F8 (if available). These will have much, much better figures for handling 393nm. Or larger, if you really want to (will require substantial mount of course).

+++++++++++++++++
+++++++++++++++++

Here's a C8 Edge HD + SAFIX operating at F20 (seeing limitations did not support anything more than this, ideally it needs to be F37 for my pixels!) on an IMX174. As you can see, it's fairly well focused as structures are defined. This needed 1500 frames stacked to even come close. Fewer frames was a mess and even more fuzzy. Compared to 656nm from this same instrument, this is very poor results.
Surface_CaK_200mm_F20_1500frames_Colored_04292019.jpg
Surface_CaK_200mm_F20_1500frames_Colored_04292019.jpg (345.64 KiB) Viewed 5848 times
And here's my cheap CR150HD (150mm F8 achromatic refractor) stopped down to 100mm F12, operating at F36 with the IMX174 (properly sampling for the pixel size):
Sunspots_AR2740_AR2741_CaK_102mmF30_61frames_BW_05062019.jpg
Sunspots_AR2740_AR2741_CaK_102mmF30_61frames_BW_05062019.jpg (420.11 KiB) Viewed 5848 times
+++++++++++++++++++
+++++++++++++++++++

Soon I will test a new instrument and potentially move away from SCT design in general for solar. I'll update as I get the gear together over the next few weeks.

Very best,


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Re: Options for high resolution?

Post by Valery »

MalVeauX wrote: Mon May 06, 2019 11:39 pm
I do not recommend the C8 Edge, or any SCT, for 393nm specifically. Can it be done? Sure. But frankly, you'll only see limited results. While my evidence is anecdotal, the opposite is true of evidence for it, also quite anecdotal.
Images worth of thousands of words.

See the results. C11 + ARIES Tri-band DERF, no SAFIX or other specially made SA correctors, no special sized pixels.

Any disadvantage in these images?

Note, that C8 has significantly less SA at 393nm.

To see the images in a full resolution right click on them and choose to open them in a separate window.

Valery
Attachments
CaK  core 1.5A BW
CaK core 1.5A BW
August-5-2018-05h-12mUT-C11-ARIES-295mm-DERF-PST-CaK-Basler-1920-55.jpg (858.78 KiB) Viewed 5837 times
393nm continuum
393nm continuum
August-5-2018-05h-42mUT-C11-PST-filter-#2.jpg (1.01 MiB) Viewed 5837 times
393nm continuum
393nm continuum
August-05-2018-05h-32mUT-C11-ARIES-295mm-DERF-PST-#2-filter-393nm-10nm-wide.jpg (1.08 MiB) Viewed 5837 times


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Re: Options for high resolution?

Post by MalVeauX »

Heya,

As mentioned, the evidence for using a SCT for 393nm is also anecdotal. It's not that simple. One cannot just take an average random copy sample of a SCT of any size and just easily image high resolution 393nm. It demands exceptional seeing conditions. One cannot just walk outside any day of the week and image the resolution you're presenting. Lots of people with interest in 393nm are avoiding SCTs due to spherical abberation, suggesting they're great for this isn't that simple. One does not non-chalantly do 393nm in high resolution from an SCT mirror any day of the week. Exaggerating this to be a simple thing and that just anyone, anywhere, with any copy variation can do it without exceptional conditions is not representative of reality.

Under great seeing, just looking at 393nm vs 656nm from the same instrument (C8 Edge), the 656nm is pencil drawing sharp, while the 393nm is not sharp, never gets close to sharp focus, and is blurry. I found that to image 393nm this way, one has to capture a lot of good seeing blurry frames, stack many many of them, to have more latitude in processing. This is asking a lot of good seeing. But again, I'm happy to learn new ways to do this if it's indeed a simple thing to accomplish with just any SCT mirror at 393nm.

However, I am not one to really argue, I would much rather learn. I'm very interested and happy to learn how you record high resolution from your SCT in 393nm and how you process it. I have much better seeing on average here in Florida. I'd be happy to employ other methods or try other things. By all means, please share how to accomplish this, how to process it this way, etc. This may be better in another thread of course.

Very best,


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Re: Options for high resolution?

Post by Valery »

Marty,

If you will stop down your C8 to 185mm you will get a scope which is DFFRACTION LIMITED at 393nm.
It will work same good for imaging (+ deconvolution and sharpening) as it work in Ha. But... it will have 1,5x higher resolution than it has at 656nm at a full 203mm aperture!!! And this equals to 12" scope resolution in Ha !!!

All is not so poor with SA at 393nm in SCTs as peoples saying.

Just don't use poor barlow lenses which do not work properly at 393nm and makes things much worser.

Of cousre, you need good seeing.

Valery


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Re: Options for high resolution?

Post by MalVeauX »

Thanks, I will give that a try some time. I have a 200mm F6 parabolic quartz mirror on the way to further test with the same D-ERF for shorter wavelength as well that is also quite light weight. I'm interested to see which is easier to work with for this, as both are similar enough to easily mount and handle, but which design would be better suited for solar especially at shorter wavelength to gain any potential advantage there is to have.

I'm curious how my C8 Edge mirror at F10.8 becomes diffraction limited at 393nm, but not at F10?

Very best,


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Re: Options for high resolution?

Post by Valery »

MalVeauX wrote: Tue May 07, 2019 4:31 pm Thanks, I will give that a try some time. I have a 200mm F6 parabolic quartz mirror on the way to further test with the same D-ERF for shorter wavelength as well that is also quite light weight. I'm interested to see which is easier to work with for this, as both are similar enough to easily mount and handle, but which design would be better suited for solar especially at shorter wavelength to gain any potential advantage there is to have.

I'm curious how my C8 Edge mirror at F10.8 becomes diffraction limited at 393nm, but not at F10?

Very best,
For good results with Newton telescope, you need to use the Baader fluorite barlow lens, otherwise with poor standard Barlows the SA at 393nm will be too bad.

For modelling of C8 behavior I do use my Zemax optical simulation software.


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Re: Options for high resolution?

Post by Dennis »

many thanks for your valuable input guys. my primary focus is h-alpha anyways.. but im also curious with trying some calcium imaging later on. ok so the most important thing is to stop the c8 edge down a bit (185mm). and of course only use barlows that pass the wavelenght good enough. and seeing. thx.


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