PST no visual change when focusing

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PST no visual change when focusing

Post by Lruacho16 » Mon Nov 04, 2019 12:59 pm

I bought a brand new Coronado PST. I realize the Sun is quiet now, but my concern is as I use the focus knob or turn the tube adjustment, the color of the Sun remains steady (red). I see no change. On utube it seems to brighten to a whiter color to see flares nod more to red/orange for sunspots. Even though there isn’t lots to see at the moment, am I doing something wrong or might my scope be damaged? I would imagine I should see some color changes as I adjust the tube. Right? Thank you

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Re: PST no visual change when focusing

Post by solarchat » Mon Nov 04, 2019 6:08 pm

Tuning the etalon moves the filter centerline wavelength to compensate for the refractive index of the air in your locale at different air pressures. It will not change the color. It may change the brightness a bit.
If you saw something on youtube that changed color, it was because they were trying to use a color camera to film through a monochrome scope (PST)

If you're talking about focussing the scope rather than tuning, it should not change the color either, only make it more crisp.

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Founder/Director Charlie Bates Solar Astronomy Project

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Re: PST no visual change when focusing

Post by robert » Tue Nov 05, 2019 7:32 am

Changing the exposure time alters the apparent colour and reveals the prominences. It would become more white with increasing exposure. Normally our eyes have such a wide dynamic range that we can see the prominences faintly. Cameras need help.

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Re: PST no visual change when focusing

Post by Rusted » Tue Nov 05, 2019 10:55 am

Let's try to improve your chances of seeing something different. Other than a plain, blank, red disk:
There's not much happening on the disk at the moment but that doesn't mean there is nothing at all to see:

First step: Check Gong Ha [] website for clues as to where the main prominences [bonfires] lie on the limb.
Click on any of the sun's H-alpha images for an enlargement.
Now remember the position[s] of the larger prominences like the hours of a clock dial.
Like [say] a prom at 2 o'clock and another at 10 o'clock.

Cover your head with something dark to improve the contrast of your view through the telescope.
It doesn't matter what it is as long as it's not slippery.
A dark coloured towel won't blow away in a breeze and drapes nicely to exclude light.
They are also cheaper than buying a special sunshade cloth.

Now, is the limb [edge of sun's visible disk] sharp in your view through the telescope?
If not, make it as sharp as you can with the focusing knob. Leave the etalon tuning band alone for the moment.

Now look really hard at the clock dial times where you saw some activity on the sun's limb on Gong Ha on their website.
Turn the knurled, etalon tuning band very, very slowly while staring at the sun's disk.
Slowly turn the etalon band from one end of its range to the other.
Impatience won't help and you are only cheating yourself. You paid good money for your solar telescope. You want it to earn its keep!

Hopefully you will find an etalon band setting where you can begin to detect slight fuzziness projecting from the limb.
This could be your very first prominence!

If Gong Ha shows clear or large sunspots then you can remember the hours on the clock dial to more quickly find it in your view of the sun.
Remember "9 o'clock and half way towards the centre." That sort of thing.

It isn't going to be easy to see very small details on the sun without a lot of practice.
That just means staring hard at your solar telescope's view of the sun. One day the surface texture may just pop into view.
That's how it worked for me despite decades of observing in white light.
You eye just isn't used to seeing things in a fairly dark, deep red colour. So your vision needs to be exercised and trained like a flabby muscle.
My first moment of real excitement was when the sun's disk suddenly turned into burning "coals" with brighter "cracks" in between.

If all this sounds too patronizing then you are denying yourself full value for your investment in solar equipment.
The experts have usually been at it so long they forget which questions really matter.

Baader 160mm D-ERF, iStar 150/10 H-alpha, Baader 35nm H-a, Beloptik KG3, PST etalon, Lunt B1200S2, ZWO ASI174.

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