What is the cheapest mod to view details of the sun up close?

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What is the cheapest mod to view details of the sun up close?

Post by daslolo »

I saw three prominences through binoviewers on a PST stock and now I'm hooked to solar - I want to see very tight close ups.

I have a Meade lx65 8" ACF.

Do I need to spend $1000 on a Baader d-ERF for an 8"? Is an 8" SCT even workable with solar given the heat? Some recommend a cheap achromatic like a $200 Orion 9836, a $500 110mm baader d-erf and a few extensions to get that 200mm sweet spot.

There are so many questions and permutation that for a newbie like me it's vertiginous so I'd rather ask people who really know the blanket question : what's the cheapest way to get a massive boost over stock PST, the combination of parts and mods to get good close up views of the sun with nice detail?

Note: I like being immersed in the image so I use only 2" wide angle eyepieces on the CST, so ideally, keeping using 2" on the mod would be more cost effective, a bino is ok as well as I've found a really cheap one that works for my eyes.

Thanks you.
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Re: What is the cheapest mod to view details of the sun up close?

Post by MalVeauX »

Heya,

Daytime seeing rarely supports, visually, a large aperture like 6".

I would suggest something like a Quark + your Binos + 102mm~127mm aperture achromatic doublet around F7 if you want to have the most cost effective, real world useful setup for viewing proms at the limb at high mag with comfortable long eye relief eyepieces.

The cost of a D-ERF for the C6 or any 6" instrument is very expensive just to find out that visually your seeing doesn't support that aperture during the day.

Very best,


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Re: What is the cheapest mod to view details of the sun up close?

Post by daslolo »

MalVeauX wrote: Sun Feb 16, 2020 11:52 pm Daytime seeing rarely supports, visually, a large aperture like 6".
Can you explain why?

Thanks for the suggestion Marty. I'm surprised you of all people didn't suggest a PST mod :D


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Re: What is the cheapest mod to view details of the sun up close?

Post by MalVeauX »

Heya,

Daytime seeing is bad. Really bad. Relative to nighttime seeing. It's of course dependent geographically where you are. And typically its better in the morning hours, not afternoon. But that too is a generalization. Overall though, you would be hard pressed to find a typical location able to support a 6" aperture at medium to high magnification during the day. Most seeing simply cannot support this during mid-day. Imaging makes it seem like you can, but lucky imaging is just getting lucky with a brief moment of good seeing. Visual is completely different. Also, the idea of aperture visually for solar, its already pretty crazy at 102mm aperture and high magnification; tons to see on the limb. Our star is close and bright. For visual, I do not advise a big 6~8" aperture, D-ERF and etalon series for visual observation. Instead, I would far more suggestion a Quark + 102mm aperture scope, or 80~90mm Lunt/Coronado dedicated double stack. I would take that any day, visually, over a 6~8" aperture scope with etalon single stack. And I have just that, a 8" with single stack + binos. Visually its useless. Imaging, I can do differen things. For visual, I would highly suggest a 102mm tops aperture + Quark or 80/90mm aperture double stack Lunt/Coronado.

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Re: What is the cheapest mod to view details of the sun up close?

Post by daslolo »

Interesting! And you recommend the quark because it doesn't need an ERF below 150mm = lower cost?

I've been looking at the sun for the past hour through my PST. The air moves. The one prominence was so nice to watch through binos.
What's the max magnification where you are?


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Re: What is the cheapest mod to view details of the sun up close?

Post by MalVeauX »

Heya,

Quark is great in cost effective high mag high res views with large apertures; nothing can beat it for cost at large aperture right now, single stack wise with a refractor. It's an entry etalon, but its good enough to see features and proms and again you cannot find another system that will let you use 102mm~150mm fracs with nothing else but the filter and a UV/IR block filter for cost.

But in general, seeing doesn't allow huge apertures & high mags. So there's severe diminishing returns.

I generally would look at 60mm to 80/90mm apertures tops honestly. 102mm max. Visually.

Visually I don't venture much past 120x magnification in my seeing conditiosn visually. But that's with a 120mm aperture and 10mm focal length eyepieces via binoviewers. Visually I don't bother with my full 150mm aperture or even my 200mm aperture, that's imaging only. For visual, I like 60 to 120mm tops in my seeing. 120mm when I'm single stack and want resolution. 60mm when I want double stack (contrast). But I generally keep it from 40x to 120x magnification in general as seeing doesn't allow much more. And my seeing is about 1.2~1.8 arc-seconds on average per measurements.

Very best,


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Re: What is the cheapest mod to view details of the sun up close?

Post by daslolo »

I tried a few things, to see how much the PST mod really costs.
I tried going cheap and was surprised to find out that you don't get what you don't pay for. For example, the Astromania helical focuser you get on Amazon for 100$ can't handle the weight of a bino.
Adding all up, the price is close enough to a Quark.

So I bought a Quark :D


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Re: What is the cheapest mod to view details of the sun up close?

Post by AndiesHandyHandies »

Hi

A compact PST mod I did was to use a Vixen VMC110 F9.4 OTA. Got a cheap OTA only return on EBAY.
Luckily moving the PST Collimator lens forward enabled me to just reach focus.
My engineering friend used a cheap barlow body for the mod. Which is a nice fit with 'opticians tape' in the scopes back.
I use a Baader 35nm filter right behind the PST Collimating lens as internal ERF, as when the rejected light goes back out of the PST Collimating lens its spread out again so no dangerous hot spot. The scope is vignetted to F10.
I find a 25mm eyepiece is enough to see details.
I have seen as much detail as in Pedros images, perhaps a tad sharper.

Andrew.


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Re: What is the cheapest mod to view details of the sun up close?

Post by daslolo »

How much did you pay your OTA?
I got a Orion 120st and now I know why everyone buys APO :-D
It's fine for solar I'm sure, I'll know when the sun gets less shy.
We need cloud filters!


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Re: What is the cheapest mod to view details of the sun up close?

Post by Merlin66 »

I’ve done and been involved in many PST mods over the years.
The current component prices are very high.....
IMHO nowadays i’d suggest going for the DayStar Quark solution rather than a PSTmod.
Just my 2c


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Re: What is the cheapest mod to view details of the sun up close?

Post by daslolo »

The quark is crisp at 1/4 disc, super blurry at 1/8th disc but that must be atmospheric conditions, there was some haze always taunting me.
I like the quark but I miss the instant feedback of turning the PST's ring to explore the sun's spectrum, it was more fun.

Is there anything you know that's continuous (real time) tune, allows high magnification, contrasty and not a bank breaker ... as a mod?


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Re: What is the cheapest mod to view details of the sun up close?

Post by george9 »

MalVeauX wrote: Mon Feb 17, 2020 2:42 am Heya,

Daytime seeing is bad. Really bad. Relative to nighttime seeing. It's of course dependent geographically where you are. And typically its better in the morning hours, not afternoon. But that too is a generalization. Overall though, you would be hard pressed to find a typical location able to support a 6" aperture at medium to high magnification during the day. Most seeing simply cannot support this during mid-day. Imaging makes it seem like you can, but lucky imaging is just getting lucky with a brief moment of good seeing. Visual is completely different. Also, the idea of aperture visually for solar, its already pretty crazy at 102mm aperture and high magnification; tons to see on the limb. Our star is close and bright. For visual, I do not advise a big 6~8" aperture, D-ERF and etalon series for visual observation. Instead, I would far more suggestion a Quark + 102mm aperture scope, or 80~90mm Lunt/Coronado dedicated double stack. I would take that any day, visually, over a 6~8" aperture scope with etalon single stack. And I have just that, a 8" with single stack + binos. Visually its useless. Imaging, I can do differen things. For visual, I would highly suggest a 102mm tops aperture + Quark or 80/90mm aperture double stack Lunt/Coronado.

Very best,
Just a comment on the earlier post. I really think this is overly pessimistic. At NEAF, which is downstate New York and not known for great seeing, Jim's 7" refractor with 0.3A filter, or Frederic's 8" SCT with 0.3A, or the 8" Lunt PT have all given wonderful views over the years, clearly better than the 4" scopes right next to them, especially on prominences. Others must have seen the same at NEAF, no? A 6" refractor is a great visual high-power H-alpha scope.

I do notice that a large-aperture 0.7A scope is generally a waste. I guess the brightness washes out the contrast, and it only produces pretty views during rare spectacular seeing. But with narrower filters, the view really benefits from the extra inches. You are gaining brightness more than resolution, I suspect.

But on the advice for daslolo and anyone relatively new to H-alpha, I agree 100% with Marty. Don't go big H-alpha. A lot of optimizing goes into producing great views. And a lot of money.

George


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Re: What is the cheapest mod to view details of the sun up close?

Post by daslolo »

george9 wrote: Fri Mar 06, 2020 8:58 pm Jim's 7" refractor with 0.3A filter, or Frederic's 8" SCT with 0.3A
How can I *cheaply* know the bandwidth of my quark?
george9 wrote: Fri Mar 06, 2020 8:58 pm A lot of optimizing goes into producing great views.
Apart from, say, add a beloptik UV/IR cut in front of the diagonal I don't know how else I can optimize Ha.
I read that adding a Ha filter could narrow the bandpass or shorten the transition to the central wavelength, if you're lucky with the intersection.
Could you give me a few examples of optimizing?


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Re: What is the cheapest mod to view details of the sun up close?

Post by marktownley »

daslolo wrote: Sat Mar 07, 2020 6:19 am Apart from, say, add a beloptik UV/IR cut in front of the diagonal I don't know how else I can optimize Ha.
I read that adding a Ha filter could narrow the bandpass or shorten the transition to the central wavelength, if you're lucky with the intersection.
Could you give me a few examples of optimizing?
No, this isn't going to narrow the system bandwidth.

Increasing the focal ratio with a quark is going to narrow the bandpass.


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Re: What is the cheapest mod to view details of the sun up close?

Post by Rusted »

marktownley wrote: Sat Mar 07, 2020 11:10 am
daslolo wrote: Sat Mar 07, 2020 6:19 am Apart from, say, add a beloptik UV/IR cut in front of the diagonal I don't know how else I can optimize Ha.
I read that adding a Ha filter could narrow the bandpass or shorten the transition to the central wavelength, if you're lucky with the intersection.
Could you give me a few examples of optimizing?
No, this isn't going to narrow the system bandwidth.

Increasing the focal ratio with a quark is going to narrow the bandpass.
Is anything gained from stopping down a 6" f/10 PST mod?


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Re: What is the cheapest mod to view details of the sun up close?

Post by george9 »

daslolo wrote: Sat Mar 07, 2020 6:19 am
george9 wrote: Fri Mar 06, 2020 8:58 pm Jim's 7" refractor with 0.3A filter, or Frederic's 8" SCT with 0.3A
How can I *cheaply* know the bandwidth of my quark?
george9 wrote: Fri Mar 06, 2020 8:58 pm A lot of optimizing goes into producing great views.
Apart from, say, add a beloptik UV/IR cut in front of the diagonal I don't know how else I can optimize Ha.
I read that adding a Ha filter could narrow the bandpass or shorten the transition to the central wavelength, if you're lucky with the intersection.
Could you give me a few examples of optimizing?
For bandwidth, I just tell by experience. I have had three Quarks. One was 0.7A or a little more, one was about 0.5-0.6, and one is about 0.4-0.5. Generally I look at filaments and see how they look on the GONG H-alpha web site. If they are dark and big on GONG but faded in the scope, that is more towards 0.7A. And if they are very faint on GONG but obvious in the scope, then that is more toward 0.4A or 0.3A. And I check for a double limb, which disappears double stack, but even single stack gets notably dimmer as you get to 0.3A

For optimizing, most of the work has gone to double stacking. That is having two H-alpha filters in series to reduce the bandwidth. I recommend against it early on unless you are buying a commercial solution. I did single stack for a while before double stacking. And I had many years experience before I designed my own double stacking solution.

You optimize exact placement in the optical train of the two etalons, do you keep them exactly parallel or purposely tilted, adding a circular polarizer between them (and where to put it exactly), rotating the circular polarizer for the best view, how to get the blocking filter to be brighter, exact temperature to set the etalon under different outside temperatures, tuning the pressure tuners. Also what binoviewing setup is optimal, what scope is best, what ERF works best, best place in the yard for best local seeing at that solar altitude, time to observe, magnification, solar seeing monitor. You are looking at things like contrast, resolution, brightness, sweet spot size and shape.

With a Quark, I think you mainly try different scopes and see what works best. You can get small improvements by optimizing the temperature, but not a big difference once you are somewhere in range. And try different eyepieces to get the best compromise on magnification and field of view and brightness.

George


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Re: What is the cheapest mod to view details of the sun up close?

Post by marktownley »

Rusted wrote: Sat Mar 07, 2020 12:53 pm Is anything gained from stopping down a 6" f/10 PST mod?
No


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Re: What is the cheapest mod to view details of the sun up close?

Post by Rusted »

marktownley wrote: Sat Mar 07, 2020 1:40 pm
Rusted wrote: Sat Mar 07, 2020 12:53 pm Is anything gained from stopping down a 6" f/10 PST mod?
No
:bow


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Re: What is the cheapest mod to view details of the sun up close?

Post by daslolo »

Increasing f ratio means f/5 -> f/9? Is that to increase parallelism of the rays?

I saw faint prominences and one long faint filament in my quark, didn't see it in the GONG... our sun is sleeping, but yeah probably <0.5A

I think that, given the ultra low activity, prominence are more fun to observe... is there a way to increase prominence brightness with a quark?


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Re: What is the cheapest mod to view details of the sun up close?

Post by marktownley »

daslolo wrote: Wed Mar 11, 2020 7:38 am Increasing f ratio means f/5 -> f/9? Is that to increase parallelism of the rays?
Using a Quark with a telecentric lens, yes, will increase contrast. PST etalon uses collimated lens - totally different optical system

daslolo wrote: Wed Mar 11, 2020 7:38 am is there a way to increase prominence brightness with a quark?
Yes, reduce the focal ratio presented to the quark to get a wider bandpass.


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Re: What is the cheapest mod to view details of the sun up close?

Post by daslolo »

marktownley wrote: Thu Mar 12, 2020 7:14 am
daslolo wrote: Wed Mar 11, 2020 7:38 am Increasing f ratio means f/5 -> f/9? Is that to increase parallelism of the rays?
Using a Quark with a telecentric lens, yes, will increase contrast. PST etalon uses collimated lens - totally different optical system

daslolo wrote: Wed Mar 11, 2020 7:38 am is there a way to increase prominence brightness with a quark?
Yes, reduce the focal ratio presented to the quark to get a wider bandpass.
That's very interesting, I will try that.

This will do the contrast increase?
https://www.amazon.com/gp/product/B00A2 ... UTF8&psc=1

How do I reduce focal ratio? One of these screwed at the head of the quark?
https://www.amazon.com/SVBONY-Telescope ... ics&sr=1-4


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Re: What is the cheapest mod to view details of the sun up close?

Post by physicsguytoo »

I have used a Coronado SM40 as an off-axis ERF with tuning and doppler adapter on my Meade LX200 a while ago. It was okay but the view was a bit restrictive since it was a 40mm aperture. Count not really focus correctly but for views it was okay. I recently, I found a 67mm Lunt ERF for $75 and I used it instead along with a PST etalon at the rear of the scope to tune while using a Coronado BF10. It works much better and the FOV is a bigger and views are sharp. The current aperture size is 52mm but I ordered on eBay some step up and step down rings for 67mm to 62mm and vice versa to enclose the Lunt ERF. I would also have to make the hole bigger to match the size of the new aperture from it's current size of 52mm to 62mm.

I bought the step up and step down adapters for like $3 a piece on eBay.
The PST etalon I bought an older model on Cloudy Nights for $150 with a rusty objective.
AOK Swiss PST Etalon Adapter $100
Coronado BF10 was part of the Solarmax II SM-60 kit which I paid $875


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Re: What is the cheapest mod to view details of the sun up close?

Post by marktownley »

Hi there,

Is the SM60 kit just the etalon and blocker or is it the scope?

Welcome to the forum btw!

Mark


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Re: What is the cheapest mod to view details of the sun up close?

Post by physicsguytoo »

Hello, the SM60 kit is the etalon and the blocker that comes inside the plastic case. Here is link to show you what it looks like

https://telescopes.net/solar/solar-acce ... gJ9FfD_BwE

Thank you by the way for saying, "Welcome to the forum"


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Re: What is the cheapest mod to view details of the sun up close?

Post by marktownley »

Rather than mounting on your big sct i would buy something like a second hand ed60 or 80mm scope and use it that way, the resulting focal ratio will be much friendlier.


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Re: What is the cheapest mod to view details of the sun up close?

Post by Bob Yoesle »

And I check for a double limb, which disappears double stack, but even single stack gets notably dimmer as you get to 0.3A... For optimizing, most of the work has gone to double stacking. That is having two H-alpha filters in series to reduce the bandwidth.
Just a bit of detail about the "double limb" and double stacking etalons and why it is done. While double stacking does indeed reduce the filter system bandwidth, most of the improvement in image contrast comes from reducing “parasitic continuum” from outside the etalon systems FWHM. Hopefully the illustration below and the discussion that follows will help to understand what double stacking does.

Double stacking.jpg
Double stacking.jpg (101.85 KiB) Viewed 1657 times

At the top panel A we see the absorption line spectrum of the Sun. Buried inside the H alpha absorption line of the photosphere, we can see there is the much fainter emission line produced by the chromosphere. For solar H alpha filters, we ideally want only to see the chromosphere emission line and none of the light intruding from the photosphere coming from outside the absorption line - aka parasitic continuum from the photosphere.

In panel B, we can see that the absorption line of the photosphere is only about 1.3 Angstroms wide. Beyond this +/- 0.65 A of the H alpha emission line, parasitic continuum begins to appear. Also shown in panel B is the transmission profile of a single 0.7 A etalon filter, and the transmission profile of two such filters in series - aka "double stacking." Note that each filter basically has a Lorentzian distribution transmission profile, and the "tails" or "wings" near the bottom are much wider than the Full Width Half Maximum (the width of the profile at 50% transmission peak) - aka "bandpass" - of 0.7 and 0.5 A, which both reside well within the absorption line. The most important effect of double stacking therefore is not the reduction of the FWHM (it's actually irrelevant - if you could have a filter with a square wave transmission profile 1 A wide it would be perfect!); it's the reduction or suppression of the transmission profile wings or tails, which reduces the amount of parasitic continuum passing through the filter system.

In panel C, we can see the effects of this for H alpha observation and imaging – with both exposures “normalized” for the brightness of the prominences. On the Left, the single 0.7 FWHM filter has a lot of continuum from the photosphere passing through, and this "noise" decreases the contrast of the chromosphere's disc detail. Note sunspot detail is quite visible. Photosphere continuum is also evident as the "double limb" where the outline of the photosphere lies 2000 km below the general edge of the chromosphere, which is dimmer. On the Right, we see the effect of double stacking, which pushes the filter profile more towards a Gaussian distribution profile and suppresses the amount of parasitic continuum from the photosphere leaking through (note the decreased visibility of the sunspot detail and disappearance of the "double limb" of the photosphere), and greatly improves disc contrast, while having virtually no effect on prominence visibility.

However, an overall decrease in peak filter transmission does make double stacked images relatively dimmer, and why increased aperture and ERF/blocking filter modifications can be employed to increase overall filter system transmission and improve image brightness. Some additional issues arise with double stacking, including reflections between the two etalons that need to be addressed – usually via slight tilting one of the etalons; and with internal etalons, the additional collimator optics can lead to more scattered light and brighter backgrounds. A circular polarizer can be employed to remove this, but also decreases image brightness even further. For double stacking, I generally prefer two front mounted etalons, followed by a front and internal, and lastly two internal filters. Rear mounted filters are monolithic systems incorporating many filter elements and polarizers, and therefore are rather difficult to double stack – but this has been done, and is easiest with using a front etalon (without the need of the blocking filter).

Bob


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Re: What is the cheapest mod to view details of the sun up close?

Post by Merlin66 »

Bob,
I’m not sure how the PSF curve of the slit spectroheliograph working at 10 micron slit width and typical x3 sampling (2.4 micron pixel) and giving a 0.06A/pixel dispersion, approx 0.18A resolution compares.
The curve I think would sit much further into the absorption curve, that seems to be the case, and gives minimal continuum parasitic light.


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Re: What is the cheapest mod to view details of the sun up close?

Post by Bob Yoesle »

Hi Ken,

Thanks. My diagram was the best I could do with what I could find on google images and therefore is probably more conceptual. Could you get me a better set of curves?


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Re: What is the cheapest mod to view details of the sun up close?

Post by Merlin66 »

Thanks,
I may need Peter Z’s help with the details…….
I do see a significant difference in the CaK image taken with the SHG and the others taken with a “2.4A “ Lunt filter.
They Lunt clearly shows the sunspot detail as per the continuum, rather the flocculation of the narrow bandwidth.


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