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Possible to eliminate Newton Rings?

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#1 drksky

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Posted 06 March 2013 - 11:17 AM

I've got an e2v Flea 3 that shows some pretty obvious Newton Rings when shooting with a 2.5X powermate. Are there any adjustments that I can make which might lessen or eliminate them? This is with an LS80DSII.

Oddly enough, I don't see any sort of artifacts when not using the powermate.

#2 ourobouros2k2

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Posted 06 March 2013 - 11:42 AM

Might try twisting the camera and see if it eliminates the rings. If not, google "newton rings tilt adapter" to find examples of DIY solutions that will let you tilt the imager off axis slightly to eliminate the rings.

In certain cases with imagers that use certain Micron or Aptina sensors, the rings are produced within the sensor itself (as I understand it). I have this problem when attempting to use the orion SSAG for imaging h-alpha. Unfortunately no amount of axial tilt can fix that.

good luck

#3 frolinmod

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Posted 06 March 2013 - 12:13 PM

Perhaps one of these T2 tilt adjusters may be of use:

http://www.optcorp.c...?pid=1289-17692

#4 neotesla

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Posted 06 March 2013 - 02:15 PM

There was another thread obout problems with the 2.5X Powermate...

http://www.cloudynig...5671143/page...

another Barlow might be the solution to the problem.

#5 ourobouros2k2

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Posted 06 March 2013 - 03:01 PM

Also if you wish to go with the teleskop adjuster, be advised they go out of stock quickly. I have seen solar imagers report success with that unit

#6 drksky

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Posted 06 March 2013 - 03:13 PM

I would think if it were the sensor, that I would see them when using native focal lengths, no? As far as the issue with the 2.5X powermate, that was in internal reflection and I'm not seeing that issue with mine. I've tried a normal 2X barlow and still got the rings.

#7 drksky

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Posted 06 March 2013 - 03:19 PM

There's a good amount of play in the blocking filter tube that might allow my to tilt it enough to eliminate the rings. or would it literally have to the camera itself that needs tilted?

#8 molniyabeer

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Posted 06 March 2013 - 06:06 PM

You can also try a "pseudo flat field." With the barlow or powermate in place, defocus on the center of the solar disk until you get a smooth grey wash with the rings visible in it. Use that video to make a "flat field" in Registax and then use that flat to process your normal videos. Seems to work pretty well, although it helps if you don't have a lot of drift in your tracking. I've found that the drift on its own will help to damp down the appearance of the rings but when you use the flat it seems to add them back in!

#9 ourobouros2k2

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Posted 06 March 2013 - 09:59 PM

I would think if it were the sensor, that I would see them when using native focal lengths, no? As far as the issue with the 2.5X powermate, that was in internal reflection and I'm not seeing that issue with mine. I've tried a normal 2X barlow and still got the rings.


Correct, my rings are present with or without barlow. They are certainly annoying.

#10 drksky

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Posted 07 March 2013 - 06:44 AM

Thanks for the tip Steve. I'll give that a try if I can't get rid of them otherwise.

I worry about using the Teleskop tilt adapter. It seems like with all the adapters that are needed to make it work might take up too much focal range to allow focus when using the powermate. That'd kind of defeat the purpose.

#11 marktownley

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Posted 07 March 2013 - 02:32 PM

Any pictures? At various focal lengths... That will help us diagnose you the best course of action...

#12 Spectral Joe

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Posted 07 March 2013 - 10:49 PM

Try a lens cap, works every time. But seriously, the problem may be in the camera, I'm sorry to say. This sort of fringing occurs in CCDs and is more pronounced with longer (red and IR) wavelengths. Some chip designs are worse than others and even with the same design there is variation from one chip to the next. If that's the case then tilting the camera is your best option.

#13 Spectral Joe

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Posted 07 March 2013 - 10:52 PM

Also, the problem is worse with larger F numbers, this may be why it's worse with the Powermate.

#14 drksky

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Posted 08 March 2013 - 06:56 PM

Any pictures? At various focal lengths... That will help us diagnose you the best course of action...


Finally got out today for a bit, although the seeing was lousy.
Here is a detail that was taken with the Powermate:
Posted Image

And, here is a two panel full disk mosaic:
Posted Image

#15 drksky

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Posted 08 March 2013 - 06:58 PM

Try a lens cap, works every time. But seriously, the problem may be in the camera, I'm sorry to say. This sort of fringing occurs in CCDs and is more pronounced with longer (red and IR) wavelengths. Some chip designs are worse than others and even with the same design there is variation from one chip to the next. If that's the case then tilting the camera is your best option.


I know that CMOS sensors tend to be worse for issues like this. The e2v sensor in the Flea was supposed to be not as susceptible. I guess that's not quite right. I may start looking for a different cam with a CCD, at least for solar. The Flea should still be good for lunar and planetary.

#16 molniyabeer

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Posted 09 March 2013 - 11:06 AM

Another possibility is to try dithering your video by slewing the image around while you capture it. When you stack the frames, you'll somewhat average out the rings. The drawback, of course, is you lose some of the margins of the frame.

#17 marktownley

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Posted 10 March 2013 - 03:53 AM

I think dithering is the best way to try first...

#18 drksky

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Posted 10 March 2013 - 07:40 AM

Do you need to do anything special in Registax to account for the movement, or will it automatically just adjust as it stacks?

How fast should the movement be? I have a CGEM, so are we talking Rate 1 speed?

#19 marktownley

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Posted 10 March 2013 - 08:12 AM

No, registax should automatically compensate for it. Often the best way to get the drift you need is just to do a poor polar alignment, it will naturally drift for you then...

#20 drksky

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Posted 10 March 2013 - 11:01 AM

No, registax should automatically compensate for it. Often the best way to get the drift you need is just to do a poor polar alignment, it will naturally drift for you then...


Being as I'm just plopping the thing on the patio and letting it rip, that shouldn't be difficult. :D






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