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January 31, 2015: Disappointing first imaging results with the SM-II 60


michael.h.f.wilkinson
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I have discussed these results over at Solarchat, and a solution has presented itself, but thought I would share the issue here as well. Yesterday I was excited to see clear skies, and hoped to get a REALLY nicely detailed mosaic: at 1200mm rather than 1000mm focal length, but more importantly, at 60mm aperture rather than just 35mm. From the outset, things looked a bit weird. Even when switching back from the 3x TeleXtender (1200mm focal length) to the 2.5x PowerMate (1000mm) the exposure time had to be pushed down from the customary 15ms all the way to 0.4ms to keep the exposures within reasonable bounds. Given a light gathering increase between the LS35 and SM-II 60 (2.9x roughly), I was expecting 5ms would work. Apparently, over ten times that quantity of light was being detected by the CCD of my trusty DMK21. Worse still, I could not get proper focus, and the result looks like a seriously off-band image (poor-man's white light)

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No proms could be seen at all in the CCD image. No manner of tuning changed the image. Baffled by this, I replaced the camera by EP, and after refocusing found the scope was well tuned, and proms and details showed brilliantly. The only explanation I could come up with (after some head-scratching :icon_scratch: and general anguisher :angry4:) was that there must have been some problem in the IR blocking of (most likely) the BF-5 blocking filter. This hypothesis seems most likely, especially after feedback from experts at Solarchat. A simple solution would be to insert a UV/IR cut filter (I have two of those) in front of the BF-5 unit or even a Baader 35nm  H-alpha filter (I would have to order that). An ERF in front of the scope (I have a 63mm) might also work.

Unfortunately, I had by then packed up all the gear, so could not check it. I did have some time to check out one other issue quickly on the grab-and-go alt-az mount: Adding the 63mm ERF to the front of the scope makes the B1200 blocking filter work perfectly on the SM-II 60. I have since heard that I could also simply insert an R-band filter from my planetary set (or the Baader 35nm H-alpha) for the same effect. The B1200 is therefore still of use :D

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How frustrating, Michael, hopefully it will be resolved on your next light and you'll soon be hammering out the images, really looking forward to seeing how you get on with the 60.

Not on the same scale as you have here but I had an issue with IR leak through the solar continuum that made the camera view of white light fuzzy while the eyepiece view was sharp. A UV/IR cut of course sorted that,

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I am sure you will get this sorted quickly, let us pray for a sunny month of February :) :) :) I have lots of testing to do as well :)

Alexandra

Cheers, Alexandra. Very patchy at the moment here, but at least I did get another look. Adding the extra ERF and using the B1200 seems to give the best contrast visually. I will compare this to the BF5 with IR/UV cut and both with a Baader 35nm H-alpha filter in imaging mode a.s.a.p.

Clear skies

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