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Issues with flats


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So I tried taking some flats last night with my CCD, which was a fun filled evening in itself! Still not sure if i'm doing it right but the images produced seemed ok for now, I have a flat light panel on it's way which should give a more even illumination than just a pc monitor.

My problems lie with the SII channel. I have attached a single frame from each of Ha, OIII and SII. The Ha and OIII look about right to me...a little bit of vignetting and some dust motes etc but the SII looks terrible!! Is the filter faulty? Is it not sitting in the wheel right? Or is it fairly standard and it wont matter as long as it removes the issues from the actual lights in calibration?

Thanks guys and gals,
Phil.

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It looks to me as if the filter wheel hasn't properly centralised the filter. Is it a manual or motorised wheel? Have you tried repeating the shots e.g. after going back to the Ha and then return to the Sii? (You need to take a large number to average anyway)

Dave

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Dave makes a good point.

The first two look credible but the third doesn't. Just as an experiment you could try applying the first one to the second and vice versa. Notice how similar they are? I doubt you really need separate ones, quite honestly.

Olly

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Dave/Olly,

I cycled through the different filters a couple of times and it was the same each time. It's a motorised one, internal. QSI 583wsg. I'm going to take it to bits later and just reseat it to see if that makes any difference. I've taken about 15 of each to make a master flat for them all.

Thank you both for your replies.

Phil

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I'm not sure to be honest Olly? I'll have a look online and see if theres anyway I can do that, however the shutter is behind the filter anyway so i wouldn't be able to see the sensor even if the shutter was open.

I took everything to bits last night, removed and refitted the filter so i'll try again this evening to see how it looks.

Phil

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would not normally happen.seat

I'm not sure to be honest Olly? I'll have a look online and see if theres anyway I can do that, however the shutter is behind the filter anyway so i wouldn't be able to see the sensor even if the shutter was open.

I took everything to bits last night, removed and refitted the filter so i'll try again this evening to see how it looks.

Phil

It looks if either the filter is either not seated on the wheel squarely or the filter wheel is not centering the filter with the light path. I am not familiar with QSI but my Zagyl FW  uses software to get the centering right. A manual wheel has indentations and this would not normally happen.

A.G

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I've had problems with SII and a laptop screen ( Toshiba ) All the darker bits were in the wrong place.

Changed to a flats panel and all was well. It also worked off a white emulsioned wall so you could try that first.

This may not work for you and everyone else may be right,

Dave.

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