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Atmospheric Dispersion Corrector for visual?

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#1 jmillsbss

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Posted 11 October 2019 - 09:06 AM

Good morning all  -  Well it's right there in the title bar.... Somebody talk to me about the results of using an ADC on a 10" f4.7 newt/dob.  Straight up visual only.  Let other guys talk about the AP applications.  I'm talking only visual.

 

From what you know, from what you've seen, through scopes like mine.  Thanks for your time!   J



#2 rkelley8493

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Posted 11 October 2019 - 09:54 AM

I'm curios to know this as well. I've had some issues with Atmospheric Dispersion in both of my scopes [SCT & Apo].

Pardon this very crappy picture.. It was taken with my phone just to show the issue I was seeing. I don't do astrophoto either.

 

Saturn Atmospheric Distortion.jpg

 

 



#3 jmillsbss

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Posted 11 October 2019 - 11:54 AM

I'm seeing a lot of info concerning APD units and they're incompatibility with dobs because of the required, but unavailable, infocus.



#4 SeattleScott

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Posted 11 October 2019 - 12:40 PM

The ZWO ADC does help a little with atmospheric distortion, especially when you are seeing a clear red/blue shift like in that cell phone picture above. Infocus is an issue. Haven’t tried it on a reflector yet. With my Mak I had to remove the diagonal to reach focus. Fortunately it is really only meant for viewing targets low in the sky, so a diagonal isn’t that critical.

Scott
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#5 MartinPond

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Posted 11 October 2019 - 05:49 PM

For most atmospheric lensing, it is impossible

   to create the inverse of the abberation, and it varies rapidly.



#6 MartinPond

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Posted 11 October 2019 - 05:52 PM

I'm curios to know this as well. I've had some issues with Atmospheric Dispersion in both of my scopes [SCT & Apo].

Pardon this very crappy picture.. It was taken with my phone just to show the issue I was seeing. I don't do astrophoto either.

 

attachicon.gif Saturn Atmospheric Distortion.jpg

 

 

That looks a lot like disperison from high stratus ice crystals, unless your phone/camera is 

   running a slow shutter..  The veils can be undetectable to the bare eye, unless they are on the increase..

 

Altitude, even a few thousand feet, works miracles in messy-sky environments.



#7 Spartinix

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Posted 11 October 2019 - 07:14 PM

Bought the latest ZWO model last year for my F5 dob. The difference is worth every adjustment you need making to accomodate focusing issues. I never observed Mars as defined before.


Edited by Spartinix, 11 October 2019 - 07:15 PM.


#8 jmillsbss

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Posted 11 October 2019 - 09:11 PM

Bought the latest ZWO model last year for my F5 dob. The difference is worth every adjustment you need making to accomodate focusing issues. I never observed Mars as defined before.


What was the altitude, if you can recall? And how'd you resolve in focus?

#9 Spartinix

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Posted 12 October 2019 - 12:20 AM

I'd have to check the altitude Mars was at. I live at 35*. There was a very noticeable difference. I moved the primary forward by 1.2".

#10 Astrojensen

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Posted 12 October 2019 - 03:19 AM

I just use the lateral color aberration in my eyepieces as ADCs. Just place the planet away from the center of the field towards the edge, where atmospheric dispersion is minimized, usually up or down from the center. Works well for me. Doesn't work on eyepieces that are superbly well corrected for lateral color. There was an article about it in the latest issue of Astronomie - das Magazin. 

 

 

Clear skies!
Thomas, Denmark



#11 Endymion

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Posted 12 October 2019 - 11:29 AM

I’m at latitude 33 N and my ZWO ADC works well visually with my C11 for the planets.

#12 junomike

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Posted 16 October 2019 - 05:31 PM

Just picked one of these up (for Newt use).

Do you use it with a Coma Corrector?



#13 Miranda2525

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Posted 16 October 2019 - 07:55 PM

Good morning all  -  Well it's right there in the title bar.... Somebody talk to me about the results of using an ADC on a 10" f4.7 newt/dob.  Straight up visual only.  Let other guys talk about the AP applications.  I'm talking only visual.

 

From what you know, from what you've seen, through scopes like mine.  Thanks for your time!   J

Link?



#14 Redbetter

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Posted 18 October 2019 - 01:00 AM

I puttered around with one with the 110ED refractor from what I recall and it really didn't do much for me for visual.  But the seeing here is not that great, particularly at the low declinations that the planets have been at.   I accomplish essentially the same or better on Mars using a red filter, so I haven't gotten much out of the ZWO ADC.  In 1 arc second or better seeing it would likely have more impact on making high powers sharp.  I just haven't had that in the backyard this past year.

 

Haven't really tried it with the Dobs from what I recall.  The last conversation I had about it I was told that for short ratios it actually needs to be paired with a 2x Barlow to get the focal ratio to a point that works well with the device without producing astigmatism that exceeds its benefit.  So if a 2x or so Barlow can be employed to reach focus in a Dob, that could make it useful for me.  Like I said, I have been far more seeing limited than chromatic dispersion limited, so I haven't pursued this with the larger scopes...especially in the backyard where the seeing is the worst.  And if I don't work something out in the backyard, I probably won't employ it at a dark site with better seeing--at least not when it requires substantial fiddling to get it to work. 

 

I'll probably make another pass at this next year for Jupiter and Saturn...if the seeing is any good.   If I lived at a latitude 5 or more degrees north of here I would probably find it far more useful.


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#15 junomike

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Posted 18 October 2019 - 07:07 AM

I puttered around with one with the 110ED refractor from what I recall and it really didn't do much for me for visual.  But the seeing here is not that great, particularly at the low declinations that the planets have been at.   I accomplish essentially the same or better on Mars using a red filter, so I haven't gotten much out of the ZWO ADC.  In 1 arc second or better seeing it would likely have more impact on making high powers sharp.  I just haven't had that in the backyard this past year.

 

Haven't really tried it with the Dobs from what I recall.  The last conversation I had about it I was told that for short ratios it actually needs to be paired with a 2x Barlow to get the focal ratio to a point that works well with the device without producing astigmatism that exceeds its benefit.  So if a 2x or so Barlow can be employed to reach focus in a Dob, that could make it useful for me.  Like I said, I have been far more seeing limited than chromatic dispersion limited, so I haven't pursued this with the larger scopes...especially in the backyard where the seeing is the worst.  And if I don't work something out in the backyard, I probably won't employ it at a dark site with better seeing--at least not when it requires substantial fiddling to get it to work. 

 

I'll probably make another pass at this next year for Jupiter and Saturn...if the seeing is any good.   If I lived at a latitude 5 or more degrees north of here I would probably find it far more useful.

waytogo.gif  This is a critical piece of info for me as my Newts are F4 (2) and F4.4.



#16 Redbetter

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Posted 18 October 2019 - 01:44 PM

waytogo.gif  This is a critical piece of info for me as my Newts are F4 (2) and F4.4.

You might even need to go a bit higher in Barlow factor for a better result for the f/4.  I don't know.  It is a moving target because one's latitude and the elevation of the target determine the correct prismatic tilt for the ADC to clear up the atmospheric color, but this degree of tilt introduces increasing astigmatism and more trouble with a steeper light cone angle.  I don't have a good feel for the trade-offs.

 

I am at roughly 37 N for most of my observing.  Someone at 45 or 50 or 55 degrees is going to be dealing with a lot more atmospheric dispersion for Saturn and Jupiter than I have been.  If they happen to have some stable air down to low elevations they could find an ADC far more useful.  Here, targets roughly 30 degrees off the horizon or below are in the "heavy twinkle" zone nearly every night of the year.



#17 Spartinix

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Posted 21 October 2019 - 12:54 PM

Even without a barlow, the view with the ZWO ADC was much better in my F5 dob.
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