Prominence - 14th May

[TakMan]

Glorious morning. Chance to have another play with the new camera.

A quick go tonight at processing the first set of data. Dark and **flat frame calibrated.

Best 300 from 2200.

TSA102s > Quark Chromo > Basler acA1920-155um (Sony IMX 174m). Captured in Basler's Pylon software as separate Mono12P .tif files on a MacBook Pro.

Processed in AS!2 and ImPPG (via Wine), then PS CC2017

 

HELP!

**Struggling with flats over compensating in the dark areas. I have a lot of dust to remove (sensor swabs turned up this afternoon via Amazon!) Currently I just move to the centre of the sun and take a 'bag flat'. Should I take the flat frame at the position of the lights capture? Or is there something (setting wise) I'm missing?

 

NO FLAT

 

WITH FLAT CALIBRATION - see white dots in the black areas.

Any thoughts..?

Damian

[tooth_dr]

Very nice job! I had a go at this myself earlier.  The more I do, the more complex this solar imaging becomes 😂

[michael.h.f.wilkinson]

Flats don't correct accurately in areas where the signal is saturated. Flat correction assumes a linear response of the sensor to light (hence the need to capture at unity gamma), something that is clearly not the case in saturated areas. 

[Montana]

I think Michael says it all. Flats are very hard to get right. I think taking a flat near the centre is OK in most circumstances, but when you have such a close up with huge lights and darks it will compensate in the opposite direction. I once chatted with Emil about this and he seemed to indicate that it would never work well.

Also, do you have two images here and doing a composite? if so, you don't need to use a flat on the over exposed image as dust bunnies never show on the black of space anyway, then use the flat on the disc part only as you aren't using the black space area for that picture anyway, so it should be win win all around. It is called the art of fudging, getting round the problem to get a great image  

Why are you still using ASK2? ASK3 has been around for ages is is much better

These are terrific images by the way, superb resolution and it looks like you got round the dust bunny situation anyway  

Alexandra

[TakMan]

Thanks for the responses, advice, etc.

Michael, I'm confused..."Flats don't correct accurately in areas where the signal is saturated."

My issue is that the flats are overcorrecting in the dark areas of the light frames, but successfully removing the dust in the lighter (sun surface area), fine - see here...

Alexandra - Hi ! 🙂

Yes, "when you have such a close up with huge lights and darks it will compensate in the opposite direction.", yep, that's the issue!

Also, "do you have two images here and doing a composite?", no this is a stack of a single set of exposures. But I see what you're saying. Process TWICE, once with the flats to remove the dust on the solar surface and then again WITHOUT the flat for the prominence and the black 'space'. I'm off to try that in a mo!

"Why are you still using ASK2? ASK3 has been around for ages is is much better" - because I'm on a Mac and running AS!2 (32bit) in Wine (emulation), and haven't worked out how to 'wrap' AS!3 into the newer Wine package as it's 64bit ! If any Mac folks can lend a hand, please pm me.

"looks like you got round the dust bunny situation anyway", yep, like you said - fudged after, I'd like to not have to!

Thanks for the praise and all your help and advise. I'm hoping when the D-ERF filter comes and I switch over to the TEC140, I'll see another positive jump in my images 🤞

On another note, I've just successfully removed most of the dust this morning using these sensor swabs, so things should be better next time out!

 

And lastly, I should send a shout out to Vlaiv, who has been unbelievable with his help and advise helping me get the best out of this new camera. The amount of time this total stranger has helped a fellow amateur astronomer out is just crazy - I'm, indebted to him - 'thank you V'! I'm amazed he hasn't told me to 'sod off'!

😀👍

Damian

Edited May 15, 2020 by TakMan

[Pete Presland]

A fine set of images.

[TakMan]

Experimenting with processing, learning and re-learning.

Wringing the neck out of the (same) data.... making slow progress.

This time processed twice - once with the flat to remove the dust motes on the solar surface and then without for the prom/space. Mashed back together in Photoshop.

Tried a variation on the colour palette as I'm still looking for my own 'look'.

Have not even opened the other data sets, perhaps tomorrow, once I've completed my Mono8 gain/offset experiments for Vlaiv to work out the optimal settings for the camera!

As 'tooth_dr' said above, a massive learning curve this solar imaging lark! Good fun though and keeps the ole brain cells ticking over...

Alexandra is another who has been helping out and answering my odd queries, a big thanks to her also 👍. I know she is not a fan of the 'inverted tone curve', so I'm keeping away from that... for now! I still have this dark line between the spicules/edge and the surface which bugs me greatly!!!

D