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Author Topic: DSS star detection threshold  (Read 3784 times)

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Offline astrokumar

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DSS star detection threshold
« on: 12:05:02, 06 January, 2012 »
Hi All,

I have been trying to Image and stack M42 a few times now and DSS always says that "Only one frame(out of 20) will be stacked. Do you really wanna continue?". Now that is really depressing as I have focussed my SCT very well using the trapezium@x5 ISO3200 and then taken 20 subs of 60sec each at ISO800. DSS is not able to see stars even though the region is filled with them as we all know. It also says I must increase the star detection threshold which I have at 2% (Am I right here?). One kind friend also told me to stretch the images before stacking. Could some one please shed some light on this issue? Last time I tried was last night with the gibbous moon. Yet M42 registerd very well in each frame. This is the same case with M81 and M31 I imaged last night.

Please help.  :(

Online chris.bailey

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Re: DSS star detection threshold
« Reply #1 on: 12:21:20, 06 January, 2012 »
What format are you capturing in? Dont do anything to the images before loading them into DSS. a detection threshold of 2% may well be a bit low, I would go to more like 10%. Is it registering all the images (are you seeing Offset values and Number of stars detected) against each frame? A silly one but are you clicking on check all?

If using DSS I usually do each operation seperately - Register, Compute Offsets and then Stack.
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Offline Einari

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Re: DSS star detection threshold
« Reply #2 on: 18:46:43, 06 January, 2012 »
Could you show one example.
DSS might have difficulties detecting stars if there's lots of trailing.

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Offline AndiTurner

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Re: DSS star detection threshold
« Reply #3 on: 20:29:32, 06 January, 2012 »
If nothing else, try uninstalling and installing again, I've had the exact same problem before too.

How many stars is it 'detecting' when you register the images?
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Offline astrokumar

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Re: DSS star detection threshold
« Reply #4 on: 13:35:31, 07 January, 2012 »
DSS does not detect stars at all, even though they are obviously seen. Infact I can even see the M42 clearly as it is bright. When the threshold is set to 10% it does not detect any stars, when set to 2% it detects 1 star. :( . There is no trailing and it is in focus too. There is a lot of light pollution, but nothing else wrong. each frame is 25MB so uploading it is quite bad. I shall try reinstalling it, but I dont want to give up yet.

Offline Carole

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Re: DSS star detection threshold
« Reply #5 on: 14:55:28, 07 January, 2012 »
Is it possible to upload a few subs to something like dropbox and give us the link, so we can have a "go" at it.  If it then works on our DSS then that must eliminate problems with the subs themselves.

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Offline astrokumar

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Re: DSS star detection threshold
« Reply #6 on: 16:06:13, 08 January, 2012 »
Hi Carole,
Thanks, I admit that I still am learning to get around the posts here in UKAI. Meanwhile, last night I converted the RAW's into TIFF's, stretched them and then had a go at stacking. DSS chose 4 of 20 frames to stack and the result was good for me as a beginner. I donno how I may attach the image here though so you can see it.


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