HOWTO with TiltingSun?

[SimonM]

Today we had an (unusually) fine morning and early afternoon with seemingly few clouds.

Out with the WL wedge and a sketch was made.

Now I'm trying to work out where the sunspot is located using TiltingSun.

An Equatorial mount with a WL wedge - I flipped the image in TiltingSun to match the view seen.

Three pieces of info, but I haven't worked out where it is:

1. Sunspot is at 03:00 (on a clock);
2: Sunspot is 80% away from the center;
3. Pressing the Up Arrow on HC, the direction of movement is towards 05:30 = mount's north?

How do I place the sunspot correctly? Perhaps there is an easier way to figure out the angle of the sunspot?

Simon

[SimonM]

I did some maths and sunspot relative to "north" was 3 - 5:30 = - 2:30 or -37.5 degrees.

Since the Sun is already tilted at -21 degrees, this is only -37.5 - (-21) = -16.5 degrees.

If I flip the image of the Sun horizontally and remember that the sunspot is 80% out, then I get a location at 12:30, being 80% towards the limb.

Comparing that with AR2804 that is off to the West e.g. close to 3:00 - something has gone wrong in determining the location?

Simon

[rsfoto]

1. Sunspot is at 03:00 (on a clock);

Hi Simon,

Three o'Clock, is West !, is on the right side and so your Titling sun Sun image is wrong, You should NOT flip the image horizontally.

12 o'Clock is North
3 o'Clock is West
6 o'Clock is South
9 o'Clock is East

Make your life easy. Take a look at my images from today, go back 15° in my image, and compare to what you saw. I was not able to shoot yesterday due to clouds.

viewtopic.php?f=4&t=30898

[SimonM]

1. Sunspot is at 03:00 (on a clock);

Hi Simon,

Three o'Clock, is West !, is on the right side and so your Titling sun Sun image is wrong, You should NOT flip the image horizontally.

12 o'Clock is North
3 o'Clock is West
6 o'Clock is South
9 o'Clock is East

Make your life easy. Take a look at my images from today, go back 15° in my image, and compare to what you saw.

Thanks, Rainer. I looked at your collection of images from yesterday.

https://rainerehlert.com/00_SCHForum/20 ... _RE_TS.jpg

Perhaps I was having a "Senior" moment? This time, I think I have "got it"!

Revisiting it again - without flipping the TiltingSun, I can see that the direction North is at 5:30 and the sunspot is at 3:00 so that it is "back" 2:30 - on a clock. Factoring in the diagonal (where I went wrong last time)...

Using the TiltingSun with 12 o'Clock is North and putting the sunspot "forward" by 2:30 I get a position that is also 80% out.

Looking at the position of AR2804 yesterday (one day on) and knowing the direction of rotation, it is now at 3:00 and close to the limb which matches the 15 degrees of daily movement.

Also evident is that it is in above, in the northern hemisphere and close to passing out of view, late to the party, then! so, I will know for next time.

Simon

[Montana]

With a Herschel wedge I always found you had to flip the image vertically not horizontally, does that work for you?

Alexandra

[SimonM]

With a Herschel wedge I always found you had to flip the image vertically not horizontally, does that work for you?

It is certainly true that a wedge will (like a diagonal) "flip" the image vertically, but with a refractor (like a straight thru' finder) the image is already inverted (rotated by 180 degrees). The final result is that the image is the right way up but reversed left to right:



I also think I was putting too much faith in the maths and to get the "correct" answer I used the simpler approach of saying how far clockwise or anticlockwise was the sunspot from moving the scope north e.g. pressing the HC "Up" button. Knowing the "answer", this maps directly onto TiltingSun after "reversing" the direction e.g. what appears as 2:30 anticlockwise is now 2:30 clockwise on TiltingSun (without any inverting or flipping).

What I hadn't appreciated was that the images are shown with North Up and the Sun tilted by an angle that varies (currently P = -21 degrees) so the Sun is tilted clockwise 21 degrees (positive angles are a rotation anticlockwise).

The second thing I hadn't appreciated was that you cannot assume that a sunspot is in the southern hemisphere if there is an hour shift of more than 3 hours clockwise/anticlockwise. Looking at the Sun in TiltingSun, it becomes obvious that this can only be determined once the position is mapped onto the Sun and it is only "true" when the Sun has not rotated away from North.

Simon