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Sunny Sundays Sun in HaHa


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This was todays sun in Ha, or at least my version of it. It was an experimental day again but I did take 10gig of mosaic data. I thought I would try 4,6 and 8 pane mosaics to see if I could get rid of the banding I get with the double stack filter.

I did not like the 6 pane, but here is a comparison shot of the 4 and 8. Stacked in AS!2 and pp in CS5. The processing was similar with both pics, but not equal. Opinions please...What colour do you see?

4 pane, LS60T DS and DMK31.

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30-06-2013 mosaic 1 by allcart2, on Flickr

8 pane, LS60T DS and DMK31. Obviously with 8 panes you get much more overlap to iron out the banding and hot spots.

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29-06-2013 8 pane mosaic by allcart2, on Flickr

Edited by allcart
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I concur that the 8 pane is a bit more even, although the NE quadrant is a tad softer than the rest. The imaging took 4 minutes more than the 4 pane so its worth the trouble. The processing was longer and more involved, but worth it too I think. I had less trouble with unneven illumination across the frame today. I don't know why, maybe I tuned differently or had the camera tilted differently. I will fathom this out eventually.

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Both sunning images and something to aspire to, more kit may be needed though...

Personally I prefer the 4 panel, more even tone and feature sharpness is uniform across the whole disc - softer on the left, well to my eye anyway.

Seems I am in the minority with the 4 panel..

Trevor

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4 pane for me. Strangely it seems the tuning is much better on the 4 pane than on the 8 across the whole disc. The SE quadrant of the 8 pane has more detail in it but the NE quadrant of the 8 pane lacks the contrast of the 4. Both are very good, I would be pleased with both and I am still struggling a bit with my double stack, after 3 months.

Do you change your tuning during a run? I am not great at mosaics, but once set I change nothing during the panes, apart from maybe the gain if the histogram maxes out. If time allows I adjust the tuning and run a second set, but often my first guess at the tuning seems best, so it's the first run that makes the cut.

With single stack I would say I spend 25% of my time setting up and tuning and the rest imaging, with double stack it is the reverse, 75% of the time fiddling with tuning, Etalon position and endless focusing and readjustment.

Robin

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I have only just got the DS filter so am still working out the best way to use it. I set up as normal and tune with the single stack first. When I think I have it the way I want I add the second filter and tune that one to match what I saw in the first, allbeit with greater detail. When I am happy I swap ep for camera and refocus. Like you Robin, when I start a mosaic run I don't change anything and hope I don't get any cloud for a few minutes.

I have started to tilt the cam to match the movement of the mount, so that the sun moves left /right, up/down as I shift to the next frame. I used to always have the cam upright, but that often makes the sun move diagonally across the frame and takes longer to reposition for the next shot.

I have removed my ERF from the double stack. A simple process but it makes the image a bit brighter again. I am making a new housing with a clear glass window for the etalon so that it won't be exposed to the elements. I don't know if that made any difference to the uneven field I was experiencing, but things went easier on this session.

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Hi Allan,

I might be wrong here, I know that with the double stack you end up with two ERFs and it only needs one, but I think it has to be on the front. The ERF is there to reduce the energy from entering the scope and without it the Etalon might overheat and lead to advanced wear. I would seek expert advice on this.

The ERFs, even if you have two are extremely unlikely to cause the unevenness or banding, but will reduce the light entering the scope and increase the exposure times.

Robin

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Yes, Robin is correct, on my double stack the one which faces the Sun has the ERF, the double underneath is blank (no ERF) and the instructions say that it mustn't be used first, only second.

Alexandra

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Interesting thoughts.

Obviously I cannot remove the ERF from inside the Lunt, so to only have one ERF does mean removing the front one.

I did read a topic on Cloudy nights discussing the removal of the ERF from the ds unit and the concensus was that it was fine to do so. I did check the temp of the etalon after an hour of sunshine and it was only at 30C so it wasn't reaching any extreme temps.

I will look into this further, just in case.

Thanks for the advice.

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Allan,

I still can't see the advantage of removing one of the ERFs, other than to increase the amount of light passing through the scope. I can see several disadvantages, like potentially shortening of the Etalon lifetime and almost certainly invalidating the manufacturer's warranty.

Robin

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I'm not sure how big the advantage is either. The image is brighter, so seeing detail is easier, and having a brighter image means faster exposure times. How much difference this really makes is something I will have to test out on a clear sunny day with stable conditions. I can then take comparison captures to tcompare settings and results.

Removing the ERF is a simple operation...just unscrew the red cover. Making a suitable protective housing requires just a little thought. I'll post some pics when I have assembled.

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