Old 19-11-2012, 01:50 PM
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PRejto (Peter)
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Diffraction Spikes?

I'm confused about seeing diffraction spikes on bright stars from my TEC140. Is this normal? Am I making some sort of fundamental error in capture?

The photo illustrates a crop from a single frame, and the bottom photo shows the result after stacking/processing etc.


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Old 19-11-2012, 04:56 PM
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Shiraz (Ray)
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Hi Peter. maybe check to see if it is the lens or the camera. If the patterns stay aligned (like they currently are) with the image frame when you rotate the camera, then it is something happening on the chip.

Last edited by Shiraz; 19-11-2012 at 08:05 PM. Reason: to add the critical bit about rotating
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Old 20-11-2012, 08:51 AM
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Hi Peter
Two possibilities that I can think of:
The spikes could be artifacts from the microlens layer on the front of
the camera sensor. Standard sensors have these lenses to increase quantum
efficiency. I know this has been discussed on the QSI Yahoo forum.

The other (vague) possibility is pinched optics, where the screws holding the refractor cell are too tight.
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Old 20-11-2012, 11:28 PM
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PRejto (Peter)
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Hi Geoff and Ray,

Thanks for your feedback! Tonight was just clear enough to get in 30 min of tests. The spikes remail aligned with the XY photo axis when the camera is rotated, remain with all filters, and are somewhat lessened by removal of the Hutech IDAS LP Filter. It's pretty clear that the LP filter makes the spikes more visible for some reason. Maybe it is the microlens cover. If so, that really is poor with no solution..... I am breathing easier knowing it's not my TEC140!


Edit: Well it is the microlens for sure. I found quite a few comments on various sites, including IIS, mentioning this effect. Not great to discover something like this after a purchase, though, even knowing about it I probably would have gone ahead given the price point in relation to larger pixel sensors. I guess I can always chop off the spikes with the clone tool or somesuch....

Last edited by PRejto; 20-11-2012 at 11:45 PM.
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