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Tuesday, 17 November 2009


What?...No Sunspot Images from your new scope?


I have often wondered about these scopes...

Much Appreciated Ctein!


Trust you to buy this 'scope during a period of low Solar activity :-p

Enjoyed the article, and look forward to seeing some photos taken through it. C'mon, this is a photography blog, after all :-)

Cool! I worked at Orion for a couple of years, back in the late '80s...

Ditto what Jay and Miserere said: where are the photos?!

I was curious at your mention of seeing the floaters in your eye. The way you write this implies that they're common; I'd always thought they were pretty rare. I have a prominent one which I can always see, and have had it for 25 years or more, but I've never met anyone else who's even heard of floaters.

I didn't understand all of this ... but I was very happy to see it, regardless. Thanks, Ctein!

Given the minimal solar activity for most of this year ( 242 days -76%- with no sunspots) I hope you got a good deal on this gizmo. You probably would get more excitement getting a $25 used spotting scope and looking at the next door teen's face.

Just fooling. Have fun. I remember how exciting it was to whip up a sun viewer when I was 9 or 10 to see the black spots.

First of all Ctein, you are completely insane. Take that as a complement. Also, I too was bummed for the lack of sun pics.

Second of all, your description of "eyeball floaters" made me go "huh." Every once and a while I have something that I guess I would say appears to float across my field of vision, sort of like glitch in the Matrix, but I never really thought anything of it.

Blowing my mind even more, the Wikipedia page for "Floater" is specific to eyeball floaters:

Thanks, really enjoyed the post.

I always thought that solar scientists are looking at the sun with wide band instruments and taking spectrograms to study the "chemistry", and now I have learned that they use very narrow band and study the dynamics through doppler effect.

But there is a number I don' understand. You tell me that 40mm aperture is enough to enjoy the sun with 1 Angstrom bandpass. But then, for a filter with 0.1Angstrom 70mm should be enough. How can solar scientists complain about having not enough light?


How idiotic of me...
I thought we were about to discuss about Nina Simone.

Dear Murray,

No, almost all folks have floaters to some degree or another. For a very small fraction of the population, they are a serious visual problem. For a very small fraction of the population, they are essentially nonexistent. For all the rest of us, they're something that usually doesn't present any visual difficulties...except in circumstances like these.

Monochromatic, collimated-light, monocular viewing is the perfect recipe for producing clear visual images of floaters.


~ pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 

Dear Ken and Miserere,

Indeed, the sun is rather late out of the gate this sunspot cycle. Very tardy of it, if I do say so myself.

However, a "quiet sun" is never, ever truly quiet. Even during sunspot minima, there are always plages (bright patches on the surface of the sun), flares, dark filaments, and prominences. It is very rare to have a day when there's nothing interesting going on.

I would say that we've gotten in about 20 days of viewing since we bought the scope. Indeed, I have seen sunspots on fewer than a quarter of those days. But out of those 20 days, there've only been two when I didn't see anything worth looking at. On half-to-three-quarters of the days, there were one or more interesting prominences along the edge.

In fact, the day we bought the scope, there was a small but quite decent sunspot group with nice filament activity in the middle of the disc and two prominences on the edge. Over the next several days, we tracked that group as evolved and rotated out of view, and as it passed the limb of the sun, it produced a very fine prominence.

For an idea of what the Sun is doing every day, check out the Big Bear Solar Observatory (where I used to work) website:


The photograph for Nov 17, 19:00 UT matches very closely what I saw (with nowhere as good resolution, of course)this morning. I saw all three plages, the dark filament across the bigger one, and the U-shaped darker cloud closer to the limb.

~ pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 

Perhaps just an idea to issue a warning that no-one should attempt to view the Sun through any optical instrument unless they are using suitable solar filters. Please don't try this with an ordinary telescope or binoculars, your eyesight will be permanently damaged.

Floaters are indeed a real problem and a common problem. They are more common as one ages. They range from being a nuisance to a visual impairment. They are more noticable when looking at something bright. They can sometimes be much more prominent in one eye vs the other. Sometimes they come and go (when they are a result of thickened eye fluid). Often they are just debris floating around forever.

The important point is that chronic floaters do not lead to blindness or anything, which is good because there is really no cure or treatment.

If you have floaters that are new or significantly increased or if you see flashes of light with them - see a doctor.

Perhaps just an idea to issue a warning that no-one should attempt to view the Sun through any optical instrument unless they are using suitable solar filters. Please don't try this with an ordinary telescope or binoculars, your eyesight will be permanently damaged.

My most embarrassing moment with a telescope was when I couldn't locate the sun in the sky with the solar filter attached. Fortunately I didn't try the spotting scope. Still looked at the sun too long that day.

The important point is that chronic floaters do not lead to blindness or anything, which is good because there is really no cure or treatment.

Yet another reason I should have a clone growing in a tank right now. I'm about to the point where lathering up my brain in stem cells and lowering it into a new body would be a good idea.

Ah, floaters. They are the bane of my optical existence.

Floaters are generally the de-pigmented "ghosts" of red blood cells that manage to leak out of retinal capillaries into the eye. They are indeed completely harmless, but the magnified shadow they cast upon the retina makes them annoying far out of proportion to their tiny size. I had a retinal tear in my left eye over a decade ago, and this released a boatload of floaters into my field of vision, and they've been there ever since. The four or five I have in the other eye are trivial by comparison. This killed my birding hobby; I used to visit hawk-watches every spring, but now it's just too frustrating. About 90% of glimpses of distant hawks turn out to be a floater. They're not nearly so annoying when it comes to photography, at least for me, as the viewfinder of a D-SLR has a different apparent distance and a narrow enough field of view that they are rarely visible.

This was a Xmas gift, huh? Makes me think of A Christmas Story: "You'll burn your eye out!"

About the floaters and flashes of light..

Flashes of light can be a detaching retina.

Had a friend go through this a couple weeks ago. (Omaha NB USA area.) Prompt laser surgery and all is well. But HE DID NOT KNOW until his wife INSISTED he see an ophthalmologist, that he was in trouble!

So good info from all on this blog.

Curse you Ctein! I have successfully avoided buying a PST for years, and now you bring this up.
Fortunately, I have to buy a Rotatrim and some printing paper (via TOP, of course), so I have an excuse not to run down to Orion.

Dear Tom,

You shouldn't be embarrassed. That's why I included a tip for aligning this scope by checking the shadow on the barrel. I mean, it's not like you can look through a finder scope to center the main scope on the Sun!

Well, not more than once.


Dear Roberto,

People still do "chemical" studies of the sun, but at this point they're doing them to so many decimal places that collecting enough photons is STILL a problem.

But, you are correct in your understanding; narrow-band observing is how most of the work is done. There are also a bunch of other elemental emission lines that are worth looking at and provide very useful information about the sun (like the structure of the magnetic fields) that are nowhere as bright as the H-alpha.

Your math was a little off, but I get your point. You're arguing that if a 40 mm aperture provides enough light to enjoy 1 Å, then 10 times the aperture (130 mm diameter) should be good down to 0.1 Å. It's not quite that easy. First, the filters aren't 100% efficient. I don't have the curves at hand that I need, but I'm going to make a wild ass guess and say that you'd actually need a 200-250 mm aperture to get the same viewing brightness at 0.1 Å.

(One can get supplemental filters for the PST that will take it down to 0.7 or even 0.5 Å. That substantially improves viewing contrast. The filters costs as much as or more than the PST. The image will get enough dimmer that I'm not sure I will ever invest in one of these. If you're really interested in higher contrast viewing, you'd probably want to go to the next larger scope, which is MUCH more expensive - circa $3000.)

But, we're not done. That 250 mm aperture gives you the same viewing brightness only at the same magnifications. And the useful magnifications for a 40 mm scope are pretty limited; it is diffraction-limited to three arc seconds resolution (with some clever image-processing tricks, you could probably improve that by a factor of two). But a 250 mm aperture can resolve down to half an arc second, and good seeing will support that. To take real advantage of improved resolution, you'd want to increase the magnification by a factor of four or five. Which means, to keep viewing brightness up, you need to double the diameter again. A 20 inch solar telescope is a SERIOUS research instrument: The one on the roof of the astronomy building at Caltech was, I think, an 8 inch scope and was used for doing serious research. The brand-new, totally-state-of-the-art NST scope at BBSO is 64 inches.

It gets worse. The big limitation on seeing for solar astronomy is atmospheric turbulence! Heat ripples! The scope at Caltech was a good research tool because it pointed across the parking lots and athletic fields-- acres of uniform land that created a nice rising column of stable air. BBSO was built on a little artificial island in the middle of the lake so that it would be surrounded by uniform-temperature water. It gets fabulous seeing. For a long time it was the consistently best solar seeing in the world. For all I know it may still be.

Even so heat ripples are a real problem, so you want to keep your exposure times as short as possible to freeze the turbulence; that's the only way to get sub-arc-second resolution. The smaller the fraction of a second, the better.

That's why solar astronomers always whine about not having enough light.

In fact it was just this problem that led me to invent the CCD array in 1971... unfortunately, two years behind Bell Labs, so no fame and fortune for me! Taught me the importance of doing a literature search BEFORE putting in lots of brain power.

~ pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
-- Ctein's Online Gallery http://ctein.com 
-- Digital Restorations http://photo-repair.com 

Hey Ctein,

Glad you found the APOD. It was what got me back into photography over three years ago. A programmer friend of mine recommended it.



Dear Animesh,

That's pretty cool! It's a pleasure to find out my print was so inspirational.

I found an original print and scanned it. It's posted here, as a high-quality JPEG:


pax / Ctein

Thanks Ctein!

Another example of why I love this site. The joy of looking at the "forbidden place" in the sky! Back in the '80s I used to work at a photo store that sold Celestron scopes, and picked up an 8" SC kit on an employee discount from the factory. Since I was the in house "expert" I could try out all the goodies so I could talk to customers about them. When Mars was in opposition in 1986 some friends and I hauled that scope up to 4500 feet in the South Cascades to observe it. The next morning I brought out one of the goodies I could borrow, a full aperture solar filter, It was amazing to look at the Sun that way, to see that it was not a bright featureless ball, but had texture and variation. It truly is something to look at that "forbidden place", let alone under magnification for as long as you please! If you ever get a chance to observe the Sun with tools like this take it!

Thanks again Ctain

and apologies for the wrong math, I forgot to go back from radius to diameter, shame on me!

In any case, I'm not at all surprised that the more light you have, even from the sun, the better it is. Just it did not come out straight from the firts post, and now you have give us plenty of reasons (and a nice connection to digital photo via the CCD sensors invention)


It's great to know that amateur solar astronomy can be affordable. I have in the past looked at the work of Thierry Legault - http://astrosurf.com/legault/ whom I am certain does not use anything affordable, but his results are spectacular.



Dear Michel,

Yes, Thierry's site is great.Includes lots of excellent technical information, too.

Good H-alpha filters are expensive.Often more than the scope. But you can do great white light solar photography, as Thierry demonstrates, and the equipment for that can run you under $1,000. His remarkable ISS-against-the-Sun photo is a masterpiece of planning and technique, not equipment.

Thierry's current preferred scope for night astronomical work costs $3,000.

Yes, by the time you get done with all the important ancillaries (a good mount can cost more than a scope), your bills can mount up... the same way the purchaser of a $2K-$3K DSLR body can easily spend more than that on lenses and accessories.

But, you can do award-winning astrophotography for a total expenditure of under $3,000. Probably under $2K, if you really know what to buy. And that's NEW gear-- there's a good market in used gear at prices from 30% to 70% of new.

Great astrophotography requires lots of time, skill, and knowledge. It does not require deep pockets.

pax / Ctein

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