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Galactic Wanderer

DSS again not stacking well

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Hi all,

This isn't the first time I've had this problem. I have about 50 of these and then I get that. I'm assuming it could be to do with alignment or poor data but I have had decent results with similar photos so I am clueless.



Edited by Galactic Wanderer

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On opening the image larger I don't think DSS will like the star shapes it looks like the tracking moved maybe it was windy.


How long were the exposures?

Edited by happy-kat
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The star shape is probably the issue why DSS won't stack it, but DSS might still accept it if you adjust the threshold for star detection. Chech the "reduce the noise ..." box and adjust the slider until it finds at least a few stars.
Personally i aim for at least 10-12, but preferably aim for ~30-60 in images with few stars, and ~100-300 in wider images with loads of stars.
When sliding it towards the minimum, i think 2%, you might (especially if the noise reduction is not checked) find that it suddenly detects thousands of stars, if this happens, you need to back off a bit, as it's not detecting stars anymore, but noise. 


If all this fails, you might still be able to somehow save the data by resizing the images. I would suggest resizing the raw files and save them as uncompressed TIF files.
Try with 50% reduction to begin with, and retry the stacking. DSS will most likely then accept the stars. This will naturally result in lower resolution, but you might not really suffer too much from it as the tracking is already too far off.
 I remember i had to do this myself a couple of times both before i was guiding, and when it was very windy. 

Looking at the star shape i don't think your alignment is very off for a 120 sec exposure, but judging by the sharp 90 degree angle it might be that your balance in both axes is simply too good. If you have perfect balance in both axes you might problems with backlash from even the lightest wind. If your balance is rear perfect, try to ever so slightly make it off balance. This way the gears constantly have something to push against and might result in better tracking. 

Was this with or without guiding? 

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