Manual dithering success.

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goldstar
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Manual dithering success.

#1

Post by goldstar »


I 've finally had enough of walking noise in my images.
I have no more funds to indulge in laptop and PHD 2 to perform dithering and have to make do with just my NexGuide stand alone guider.
I experimented crudely by stopping after a random number of well guided lights and turning off the NexGuide.
When switched on again the guide star remains still on the cross hairs so I can then use fine RA/DEC movement on the NexStar HC to move the star slightly off the cross.
It is then just a matter off re-selecting LOCK and then AUTO CAL and within less than a minute the new position of the star on the sensor is locked on and guiding.
I was afraid the process would take too long but I think because the guider was using the previous parameters I found it was quite fast.
I was happy to loose a few frames now and again out of every 12.
I continued to randomly do this over 2 hours, moving to different quadrants around the cross and sometimes as much as +- 100 pixels!
I was not concerned too much and was happy to leave it all guiding while I went in for snacks and a warm up before returning.
I did about 6 manual dithers this way over 2 hours.
Now this was just an experiment. I realize that it is recommended to dither every frame and not use deviations of more than a few pixels but I just wanted to confirm the crude process would work and how arduous it was to perform.
And it did!
And it became easy after a few attempts. I can develop a routine now.

80 mm f 7.5 ED on AVX. 2 hours of 120 sec lights and some darks. Canon XS modded with Baader M+ SG filter.
Never mind the bloated stars or the patches to each side of the image or the dust spots (I took no flats).
DSS, ST and PS.
I just wanted to see the absence of walking noise which I can assure you would have been strolling all over my image otherwise.
hohd2019ndarks a ps.jpg
Scopes: 200mm f6 DOB:CR 6 150 mm f 7.5 refractor, SW ED 80 mm f 7.5. 2 X 80 mm f7.5 guides.
Mount: AVX.
NexGuide auto guider. Cameras 3 Ti and XS modded. I optron Skytracker.
Motley EP collection.
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Juno16 United States of America
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Re: Manual dithering success.

#2

Post by Juno16 »


Amazing job of manual dithering!

Glad that you got a routine down and saw success ir ridding the dreaded “walking noise” it sure does ruin an image!

Great work!

Jim
Jim

Scopes: Explore Scientific ED102 APO, Sharpstar 61 EDPH II APO, Samyang 135 F2 (still on the Nikon).
Mount: Skywatcher HEQ5 Pro with Rowan Belt Mod
Stuff: ASI EAF Focus Motor (x2), Orion 50mm Guide Scope, ZWO 30 mm Guide Scope, ASI 220mm min, ASI 120mm mini, Stellarview 0.8 FR/FF, Sharpstar 0.8 FR/FF, Mele Overloock 3C.
Camera/Filters/Software: ASI 533 mc pro, ASI 120mm mini, Orion SSAG, IDAS LPS D-1, Optolong L-Enhance, ZWO UV/IR Cut, N.I.N.A., Green Swamp Server, PHD2, Adobe Photoshop CC, Pixinsight.
Dog and best bud: Jack
Sky: Bortle 6-7
My Astrobin: https://www.astrobin.com/users/Juno16/
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