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Proper "First light" of Lunt60 double-stack


jarbi
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Hi Everyone,

Finally some sunny days here, so I got the chance to test my double stack upgrade :p. The most remarkable difference I see between single and double stack is increased contrast between different surface features ( filaments, sunspots, protuberances ). I don't have full understanding yet how to find the ideal tuning of two etalons, but I am getting closer and closer :). My images below were acquired with a DFK31 cameran in B/W mode in direct focus. The "close-up" images were taken through an Orion shorty plus 2x barlow. Processing was done in Registax 5.1 - it is just released, and feels much more stable than v5.0, there are also remarkable new features.

All comments are welcome !

Clear skies,

Janos

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Edited by jarbi
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Looking good.

I also have a double stack set-up - SolarMax60, which as you say gives far better surface resolution, but I do find the single stack is slightly better from proms... the doppler shift??

On the images there appears to be a horizontal banding, probably form the processing(?)

I found tuning the double stack to be a PITA for the first few times! For my set-up, tune the outer most filter first and then fine tune with the second.

Look forward to your next results.

Ken

Edited by Merlin66
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The banding I suspect is Newton rings, be interesting to see this at F40, and how it holds up..

I agree Nick, this banding doesn't come from processing. I have read on the Lunt Yahoo group about it as well, they say you can get rid of it by finding the proper distance between the camera and barlow ( question of experimenting ). Since I am on holiday abroad now, I cannot try F40 but I will do it at home.

cheers,

Janos

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Looking good.

I also have a double stack set-up - SolarMax60, which as you say gives far better surface resolution, but I do find the single stack is slightly better from proms... the doppler shift??

On the images there appears to be a horizontal banding, probably form the processing(?)

I found tuning the double stack to be a PITA for the first few times! For my set-up, tune the outer most filter first and then fine tune with the second.

Look forward to your next results.

Ken

Thanks Ken,

Tuning is for me still not completely clear, this is related to banding as well as I see. When I try to find the best contrast, I always get a band where it lookd-s the best, not the whole image. There are tuning positions where I have the whole solar disc equally illuminated, but than I never have the best contrast. Seems to be a characteristic of these Lunts. I am planning to run some comparison imaging between single and double stack to see what happens.

Janos

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Very nice images Janos!! After having a go imaging with the single Lunt60 I am now very keen to get the double stack option working after seeing your remarkable 'first light' images!

Do you record as avi? How many frames were stacked for your images on this thread? Amazing details!!

Cheers,

Sheri

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Reading through a number of posts on the Lunt forum on the subject of banding it seems that it can also be down to the focuser. So check the focuser to make sure the drawtube is not sagging at all and adjust it if needed. It doesn't take much misalignment to cause banding problem. Or you could just upgrade to a Feather Touch I suppose.

John

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Reading through a number of posts on the Lunt forum on the subject of banding it seems that it can also be down to the focuser. So check the focuser to make sure the drawtube is not sagging at all and adjust it if needed. It doesn't take much misalignment to cause banding problem. Or you could just upgrade to a Feather Touch I suppose.

John

Thanks John,

You may have a good point here. I have the "standard" dual speed focuser, and the drawtube seems OK. The weak point is the compression ring, because it doesn't hold the 2" tube of the diagonal tight enough. Even when I fasten it well, it can wobble a bit sideways. I will try to figure out how to fix this.

cheers,

Janos

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Very nice images Janos!! After having a go imaging with the single Lunt60 I am now very keen to get the double stack option working after seeing your remarkable 'first light' images!

Do you record as avi? How many frames were stacked for your images on this thread? Amazing details!!

Cheers,

Sheri

Thanks Sheri,

I am recording in AVI indeed, using IC capture for the DFK camera. The posted images were processed from a stack of the best 1500-2000 of 4000-5000 frames. Specially when working with barlow, I need to gather enough frames to compensate higher noise ( caused by high gain ). To shorten processing time, I never record full frames. In IC capture, I can select an "area of interest", so you have smaller file as well.

cheers,

Janos

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I have the standard focuser on my 60 as well and I've found that if the drawtube is only about half way out there's no sag at all, but if the drawtube is all the way out it does flex a bit. So I start with the drawtube a bit less than halfway out and then get rough focus by pulling out the diagonal. That seems to prevent any problems and I don't see any banding at all on mine.

John

PS

On mine the diagonal tube is a very tight fit into the drawtube so no problem there.

Edited by johninderby
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Banding i s down to the glass and CCD...the newton rings I don't get on the SV50 using the Lumenera, I did get them with the DMK...same scope, same televue powermates, only difference was the CCD back space and any additional glass covers

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