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Hawkeye164

Help seeing granulation

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I recently bought a Orion 70mm Solar telescope with a built in white light solar filter.

I am having trouble finding grainulation even at high power.

Am I able to see grainulation with a telescope of this aperture?

thanks. 

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Hello Hawkeye, welcome to SGL. A 70mm telescope is on the small side to easily see solar surface granulation. It is possible but you will need excellent seeing conditions. A solar continuum filter should give you a better chance. Good luck.     🙂

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You should be able to spot granulation with that telescope, but it will be tiny.

It will also depend on seeing effects very much - you need steady atmosphere for comfortable viewing of such small features. You also need high power eyepiece - and a good, sharp one, for best views.

Typical size of features is 1500km, and at a distance of 150x10^6 km from earth, that translates into around two arc seconds - that is tiny. Human eye can resolve features up to about 1 arc minute in angular size (20/20 vision). So in theory you should be able to start resolving granulation at x30 power, but it will be extremely tiny.

Your scope is theoretically capable of going up to x140, but with 500mm focal length that is hard to do unless you use some sort of barlow.

It is also probably best to keep your power below x100 with such scope.

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A simple pale red (#23A) or orange (#21) filter can help, too. These colors are less disturbed by turbulence, which is necessarily stronger in the daytime. And high power is not always the best way to see finer structure, placing the scope at a place of lesser turbulence like grass does a lot to steady the view.

Eyepieces become sharper in single color light because they no longer have to focus colors with different properties at the same spot, which never succeeds perfectly. The pale red 23A is a strong contrast enhancer but other colors might work for your eyes, experimenting with filters is very cheap, 15€ each.

I see the solar grain with my 80mm scopes at low power, but it is an unusual thing to look for very small features which go from bright white to pale grayish white on an almost blank surface. It also take practice. Just insisting might be the whole solution for you; several days are normally needed to develop a new ability.

 

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In all the times I've observed Sol, I've only once seen granulation. This was with an 8" newt with high magnification. As someone already mentioned, conditions have to be just right to see without specialized gear. Keep trying and eventually you'll see it. :)

8 hours ago, Ben the Ignorant said:

A simple pale red (#23A) or orange (#21) filter can help, too. These colors are less disturbed by turbulence, 

Ben, I wasn't aware of that. Thanks for the info. I'm gonna try those.

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A variable polarising filter can also bring out detail, it is a similar effect to a thin hazy type cloud passing in front of the sun 🌞 

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@Hawkeye164 as has been mentioned, granulation can be tricky to see, needing a number of factors to be right in order to be visible.

Many people view the sun at lower powers and, seeing the mottling effect across the surface consider this to be seeing the granulation (I used to think the same before I learned more :)). The reality is that this is more a ‘macro granulation’ effect, the density of the smaller cells varying across the surface and being visible as this mottling. You are seeing granulation effects but not the individual cells.

As @vlaiv rightly says, the cells themselves are tiny and require high power (probably x150 to x200) to see. At these powers, you can really see the individual cells and under good conditions can watch them change and evolve over relatively short periods of time (minutes, not hours).

I find that these cells are most easily visible towards the centre of the sun where you are effectively looking right into them so the contrast is highest, they are hardest towards the edges. Conversely, faculae which are the bright filament like structures are easiest towards the edges where the limb darkening allows them to show up more.

To see granulation I use a decent quality 100mm refractor with a Herschel Wedge, Binoviewers and high powers. Binoviewers help me because of floaters in my eyes but are by no means essential. Seeing conditions need to be right, and observing in the early morning or evening often gives the best results. The atmosphere can often be hotter and more turbulent during the day.

So, can you see granulation with your scope? I genuinely don’t know the answer but I suspect you may struggle. It is an achromatic scope so will show some chromatic abberation  or false colour. This can hurt the detail, so as mentioned a colour filter or even a narrowband continuum type green filter can help to remove this. Your scope is f7.1, which is not too fast so other abberations should be reasonably well controlled. Finally at 70mm you may struggle for the resolution needed to see such small structures based on the aperture (visible resolution increases with aperture)

I say just carry on trying! Stack the odds in your favour be observing frequently at the best times of the day, and avoiding tarmac surfaces or observing over houses. Use a range of powers including high power, and try some coloured filters if you have them, bearing in mind that a narrowband one would not be cheap and other upgrades may make more sense and give you better views of the granulation so do consider this before buying one.

Good luck, and let us know how you get on! :thumbright:

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With My 90mm refractor solar granulationon is observed on clear days with good transparency yes he said daytime transparency, the observed granulation seems more apparent when Sol is at it's highest in the sky. Even when I don't visually see it if a photo is taken often at least some granulation is captured. Focusing the Sun without sunspots can be a trick, it helps to focus the edge to a crisp circle and reajust focus a few times as your one attempt at focus might be slightly off but just enough to smear the grain. I have observed granulation in my 1964 Sears 60mm so you should see it 🙂

Edited by SIDO
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2 hours ago, SIDO said:

With My 90mm refractor solar granulationon is observed on clear days with good transparency yes he said daytime transparency, the observed granulation seems more apparent when Sol is at it's highest in the sky. Even when I don't visually see it if a photo is taken often at least some granulation is captured. Focusing the Sun without sunspots can be a trick, it helps to focus the edge to a crisp circle and reajust focus a few times as your one attempt at focus might be slightly off but just enough to smear the grain. I have observed granulation it my 1964 Sears 60mm so you should see it 🙂

I find that you can focus just using the granulation cells when seeing is good.

I guess if you can split the Double Double with a 60mm frac, which is a little over 2 arc seconds separation then you should be able to see the granulation cells of similar size with sufficient power.

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