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First (sun) Light with Lunt LS50THa


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A first decent day of sun and first light with my new Lunt LS50THa...
Perhaps I'm trying to run before I can walk, but a bit disappointed. :o

What worries me particularly is the significant variation of the image
detail / quality / brightness from top to bottom - Before I process it? 


The above image is with a ZWO ASI120MC attached directly to the diagonal. 
But a different combination of adapters + Watec 910HX gives a similar effect?


(OK, the "Sun" is elliptical - The pixels are rectangular + the chip needs a clean!)
But not really sure where to START addressing the (many?) issues right now...
Perhaps like 2001's Star Child, I'll "think of something"? But all ideas welcome! :p

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Aaaah, that's better?!?!?

I've overcooked the processing to illustrate the acceptable (more even) illumination.
But THIS looks like image DATA I can actually work with... :)

Basically, I rotated and firmly *clamped* the diagonal at 90 deg to the above setup!

I know that "Imaging - Solar" is not a priori a discussion forum, but if this can help
calm the shredded nerves of any aspiring/ future / fellow H-Alpha Lunt 50 users? :p



Edited by Macavity
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3 hours ago, michael.h.f.wilkinson said:

It is always hard to get the tuning just right to avoid gradients. 

It seems so! :p (I do wonder if this is/was an issue with diagonal collimation) 

Anyways, despite knowing little about processing H-Alpha solar images - and
a conversion from ASI 120MC colour to mono, I'm much happier with things:


I will have to read your post on how to process things properly now... :)

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Heheh - As the media are wont to say: An "emotional rollercoaster"? lol
But I was vaguely concerned I'd bought an expensive paper weight!  ;)

And Thanks! Not easy to reply when a first image is a tad indifferent?
But frantic reading on the subject suggested it might be an idea to try
rotating the diagonal. So it proved. The setup is now firmly clamped! :p

Close examination of the (somewhat striated!) image confirms that I
might yet benefit further from a genuine monochrome camera...
But a small (and later) price to pay if the basics work! :)

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A great first shot but gradients are part and parcel of a H alpha etalon, the knack is learning how to overcome it. The biggest point of all is that the right hand side is not on band so will always be brighter. Try to get the etalon on band as possible by eye, then add the camera and move the sun around the camera chip until the Sun is more evenly on band, sometimes this can be to the bottom right, top left etc. You don't need to image the Sun directly in the middle of the frame, just trim in Photoshop afterwards. Obviously if your chip is small and you don't have room to move this can be a problem and you have to tune to bang on in the centre, sometimes it is then better to just take a mosaic after using a Barlow.



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Belated thanks,  Alexandra! I begin to appreciate the issue (and solution) better now. :)

The (entirely arbitrary) rotation of the diagonal by 90 deg proved somewhat a "Eureka"
moment, so things can now be worked on! (Might influence choice of Mono chip etc.)
Sadly, it's "grey cloud" for several days now, but I sense it will hold setup meanwhile. ;)

Hopefully not to tempt providence, but I do begin to really *like* my LS50THa now.  :p

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  • 1 year later...

I know this is an old thread, but I am just starting out with a Lunt LS50tha single stack and a borrowed asi120mc. It took me a while to find focus and I'm not getting anything close to the great images posted above.  I'm using SharpCap and Registax am wondering if anyone can recommend gamma/gain/etc settings. (or better/simipler software? there are so many setting options!! I'm overwhelmed)  There are lots of youtube videos on other astronomy imaging, but not much solar/sun.  Thanks.

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