Boring sun yesterday

[Kaptain Klevtsov]

PST shot yesterday. I couldn't find the spots that were suposed to be there, just the tiny one on the right. No prominences to be seen anywhere, in fact it's the least interesting view of the sun that I've had with the PST. So to make this much more exciting, it's an image of the sun close to the solar minimum.

Ha PST, Atik 16HR camera with shortened nosepiece and Barlow lens screwed into that.

Captain Chaos

[SteelRat]

S'a great shot CC - can see why you like the PST so much 8)

[The Warthog]

Interesting, eh? I didn't bother to put my scope on the sun yesterday, having looked at the SOHO pics. I so want to catch some sunspots.

[geppetto]

Not boring at all CC

Lovely colour and textures.... few spots would have livened

it up though

So of those sun scopes

[Astroman]

What a coincidence, I set up the solar scope Sunday and saw the same quiet sight in white light. One, teeny weenie spot, maybe the size of Earth and that's it. Didn't even bother to call the wife. You're right, though. It's not easy getting a totally featureless Sun! Even if there's no spots, there's almost always a prominence or filament or something. Nice catch.

[Andrew]

OK, get ready for a really stupid question.........

I was admiring your image when it struck me that it looks a little like 3D ball with light shining on it slightly from above - a little like the sort of thing you might generate in a graphics package in which you can set the orientation of lighting relative to the position of the object in the image. However, the light here is coming from the object rather than originating above it and reflecting off it. So, why does it appear that the upper hemisphere is brighter than the lower hemisphere?

Sorry - I did say it was a stupid question

[Kaptain Klevtsov]

I don't know, we'd better wait for Astroman to tell us.

My guess, based on what happens when you twist the tuner to alter the actual wavelength being filtered, is that it's caused by the differential redshift of the surface caused by the rotation. Its just a guess!

The brighter part can be moved around the image using the tuner, it doesn't appear to happen visually, but that could be the amazing Mk.1 eyeball compensating for differences in brightness across the disk. I'd like to know why it is for real, as that might help get the whole thing at the same brightness which would be easier for imaging.

Captain Chaos

[Andrew*]

I agree - that's dead boring, CC. We've had that same sun for as long as I can remember. Aren't we all getting rather tired of it?

...

I want a PST... it's so beautiful!

Andrew

[Astroman]

So, why does it appear that the upper hemisphere is brighter than the lower hemisphere?

I don't know, we'd better wait for Astroman to tell us.

My guess, based on what happens when you twist the tuner to alter the actual wavelength being filtered, is that it's caused by the differential redshift of the surface caused by the rotation. Its just a guess!

The brighter part can be moved around the image using the tuner, it doesn't appear to happen visually, but that could be the amazing Mk.1 eyeball compensating for differences in brightness across the disk. I'd like to know why it is for real, as that might help get the whole thing at the same brightness which would be easier for imaging.

Captain Chaos

Oh jeez, I was hoping you had an explanation, CC. It's your scope/image/entry after all. :?

My original thought was vignetting. This is the 40mm PST, right? But when you say you can "move the brighter part around the image", how far, which direction and does it change character in doing so? By "character", I mean does it get bigger or elongate or simply move toward/away from center?

[Kaptain Klevtsov]

Its sort of, you can have one side, the centre OR the other side bright, by turning the tuner ring. This is why I guessed that its picking up the bit that's coming towards us, staying equidistant, or going away from us.

I need to check out exactly what it does and maybe post a series of animations. I should also figure out which is the top of the sun and which way it turns I think.

To get this done right, I need to post images with North up right? Can I see a little post stuck out somewhere? Can I heck as like.

Also, as it's a Frac. the image should be the right way round east-west wise I assume?

Don't all hold your breath as it doesn't do sunny here often, but I'll have a go armed with the "need to know more stuff" attitude.

Captain Chaos

BTW I just take their pictures, like I took a picture of my gorgeous chick. You think I understand her?

[Astroman]

South is up, Sun rotates right to left in your image.

"BTW I just take their pictures, like I took a picture of my gorgeous chick. You think I understand her?"

Point well taken.

It doesn't matter which way is up, as long as you're consistant.

It's also possible you're picking up the Doppler shift, but I think it's more likely an issue with the etalon filter itself as regards the angle of incidence, could create hot-spots. Maybe the price of low cost.

[Greg]

Feel free to shoot me down in flames....

It wouldn't just be detuned of Ha due to ghosting????

So in effect showing white light???

i'll get my coat....

[Greg]

PS..

it's not boring at all CC ...Smashing pic...

[Astroman]

Feel free to shoot me down in flames....

It wouldn't just be detuned of Ha due to ghosting????

So in effect showing white light???

i'll get my coat....

That's brilliant, Greg! "Ghosting" is the word for the etalon issue I was searching for. You may have it right on the nose. One of the reasons Coronado can sell these so cheap is the quality of materials and precision of assembly. While safe, they're not the most accurate filters and therefore have less than perfect characteristics. (Another big factor is small aperture.)

Nice one. I think you've solved it.

[barkis]

Now that all the why's and wherefore's have been ironed out, can I just congratulate you on a very nice image of our life giver.

Yeah, Yeah, I know I'm a boring old Tw--.