Darks not working

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descott12
Posts: 57
Joined: Mon Dec 17, 2018 2:32 am
Location: Charlotte, NC USA

Darks not working

#1

Post by descott12 »

Hello,
I have long struggled with darks. I am using SC Pro 3.2.6383 with my Evo 8 + 0.63 reducer + 294MC Pro
My darks are matched for gain, resolution, color space, temp, exposure and flip.

The hot pixels show up with or without flats. And they seem to be worse without the dark so it appears to be doing something.

I was hoping somebody could take at the image and dark. The files are too large to upload so is there a better way to send them?

On a related note, I seem to have quite a bit of drift. I have attached a screen shot that shows the drift graph and the candy-cane hot pixels mentioned above. I am using an EQ mount. PA by SC was "good" and my mount is well balanced. What are some causes of the appearance of the drift graph. Interestingly, the pattern of the drift graph exactly matches the hot pixel trail but I guess that would be expected.

Thanks
Dave
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Drift.png
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admin
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Re: Darks not working

#2

Post by admin »

Hi,

I think we have discovered an issue with the hot pixel algorithm not kicking in in some circumstances - see this thread : viewtopic.php?f=17&t=3236

I am going to put out a new update to the 3.3 beta in a few days with a potential fix in it - that will be worth testing.

Robin
descott12
Posts: 57
Joined: Mon Dec 17, 2018 2:32 am
Location: Charlotte, NC USA

Re: Darks not working

#3

Post by descott12 »

Hey Robin,
That would be great. I will certainly test it and let you know.

What about my drift graph that I included above? Does that tell you anything about what I could be doing wrong with my mount?
Thanks
Dave
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Re: Darks not working

#4

Post by admin »

Hi Dave,

I'd guess that the shape of the drift graph is largely down to a periodic error in RA superimposed on a little DEC drift. The periodic RA error is usually related to the gearing in the mount – basically if the axis of the gear is even a tiny bit off centre then it will give this sort of problem. DEC drift can be associated with polar alignment issues or potentially something as simple as the legs of the tripod gradually sinking very slightly if the ground is soft.

In some of the areas where the drift is faster (further between the crosses) it looks as though you may be getting a few pixels of drift per frame – this will be affecting the sharpness of your images so you may wish to consider guiding to try and reduce this drift. Another possibility would be to take shorter exposures

Cheers, Robin
descott12
Posts: 57
Joined: Mon Dec 17, 2018 2:32 am
Location: Charlotte, NC USA

Re: Darks not working

#5

Post by descott12 »

Thanks Robin,
Yes, I think I need to look into my PE and see if it can be minimized.
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Re: Darks not working

#6

Post by admin »

Hi,

the two typical approaches are either periodic error correction (PEC) or guiding. I've always gone for the guiding approach myself, but it does add complexity to the setup and the software.

Cheers, Robin
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