ADC- essential for planetary?

[johninderby]

Or perhaps an ADC airlines shirt? 😁

[andrew s]

3 hours ago, mikeDnight said:

ADC - essential for planetary?  It seems the answer is no!   

That's saved me a few bob! 

 

More like a score draw.🪐  Regards Andrew 

[chiltonstar]

Some interesting comments on seeing; I notice with mine (ZWO on 180 Mak) that where the poor seeing is of the sparkly, scintillating variety (you know what I mean) it appears to make no difference, but the slow swimming pool type that often appears if the sight line is over a hot road or roof or whatever, the ADC does appear to improve the view significantly.

Chris

[bomberbaz]

Finally got chance to properly try mine out tonight, I specifically made sure I gave it a workout. 

I used it while mars was at around 20 degrees rising over the next 30 minutes although I didn't need to alter the ADC settings. 

Anyway suffice to say that it certainly cleared up the view even in an F12 Mak and I concur with other peoples reports.

[globular]

Hope it's ok if I tag on to this old(ish) thread... I've read it all with interest.... and I'm keen to tap into the expertise of ADC users and AD sceptics alike.

My understanding of AD is that it is caused by different wavelengths of light being refracted by different amounts by The Earths atmosphere.... so all the wavelengths don't fully converge in a telescope.... and you get colour distortions (and possibly softer images too?).  And the lower in the sky the object being observed is, the more atmosphere the light passes through, so the more AD will be present.

And my understanding is that an ADC contains 2 prisms that can be rotated relative to each other and, when set correctly, they refract the light back into line.... correcting the colour distortions (and sharpening the image).

Now I'm happy with the physics of all of this.... and would happily get an ADC to correct AD.....  but so far in my observing I'd don't ever recall seeing the issue. 

Why aren't I seeing it?

I'm not complaining or anything.... but surely I should be seeing this phenomenon as it is atmospheric.... and I look through the same atmosphere as everyone else.

This thread is full of people who see AD and benefit from an ADC and others who don't.  I don't like not knowing why there is this different experience.... it's a gap in my understanding.... and I don't like gaps.

Can anyone explain what's going on?

[Stu]

@globular, it must be that clear Shropshire air! 😉

A couple of questions…. What scope do you use?

What sort of targets do you observe?

If you view planets when low down in the atmosphere then I would be surprised if it wasn’t present. All I can think is that perhaps your eyes just aren’t very sensitive to colour, but that’s a guess!

[markse68]

Dunno Glob, maybe aperture has an effect too but i don’t know why. Last year Jupiter benefitted a lot from my adc but this year i haven’t bothered as i’m not noticing any ad as it’s higher i guess and the views have been very good on many nights without.

But if you want to see the effects of ad have a look at Antares

Mark

[Peter Drew]

My experience has been that the larger the aperture the more beneficial an ADC can become when observing low declination bright objects.  I'm not particularly bothered by false colour that is not caused by poor quality but by unavoidable physics.  I was looking at Jupiter a couple of nights ago with a 16" SCT and the AD red and blue fringes were obvious.  Just for comparison sake I added an ADC to the binoviewer , if you want to see false colour try a badly set ADC!.  I duly adjusted it and supressed the AD, what I did notice immediately was that the streaming turbulence was also supressed, the net result was a better Jupiter image.  I'm in the ADC is worthwhile camp.     🙂

[globular]

I'm using an 8" EdgeHD and have been actively looking for AD on the planets the last few sessions.
Maybe I've just never looked "low" enough?... I don't have a great horizon (trees not houses) so they have to be 15° or so for me to pick them up.
Jupiter has been very stable and I've picked out all sorts of greys, browns, creams, tans etc... so I'm seeing colour just not "bad" colour.

I'll try Antares next clear night.... but I'll have to jiggle things to be able to see it... it's a bit too low....  so maybe this is the answer.... my horizon is high enough for my aperture not to be impacted by AD... ?   

Edited September 21, 2021 by globular

[globular]

I found this online...

I've been observing Jupiter at about 20° (or 70° Zenith Distance) so I should be seeing something like 5 arcsecond separation between red and blue.  And in my 8" that should be pretty noticeable..... shouldn't it?

4 hours ago, markse68 said:

Last year Jupiter benefitted a lot from my adc but this year i haven’t bothered as i’m not noticing any ad as it’s higher

Same goes you for @markse68 I guess?..... a year ago Jupiter was around 13° wasn't it..... so maybe 7 or 8 arcsecond separation of red and blue.  Does that extra 2 or 3 really make all the difference between needing ADC and not?

Maybe the UK has a much more back-ended curve than Mauna Kea?

🤔

[John]

I do see the effects of AD from time to time since the planets have been lower but never to the extent of feeling that I ought to be using an ADC. 

If others find one useful / beneficial, that's great so I'm not in the "against" camp, I just don't feel the need to use one myself

Similarly with a coma corrector for my 12 inch F/5.3 dobsonian.

It's good that these devices have been developed and are available for those who wish to use them though 

 

[Stu]

7 hours ago, John said:

I do see the effects of AD from time to time since the planets have been lower but never to the extent of feeling that I ought to be using an ADC. 

If others find one useful / beneficial, that's great so I'm not in the "against" camp, I just don't feel the need to use one myself

Similarly with a coma corrector for my 12 inch F/5.3 dobsonian.

It's good that these devices have been developed and are available for those who wish to use them though 

 

I’ve tried a couple of the ZWO ones out, and each time found that they just required too much faffing about and were too cumbersome (for me) when used with binoviewers.

This was with 4” refractors generally though, so perhaps as Peter said if I were using a larger aperture scope, the benefit would have felt more worthwhile. I certainly see that they have an effect which can easily be seen when people image using them.

[markse68]

9 hours ago, globular said:

I found this online...

I've been observing Jupiter at about 20° (or 70° Zenith Distance) so I should be seeing something like 5 arcsecond separation between red and blue.  And in my 8" that should be pretty noticeable..... shouldn't it?

Same goes you for @markse68 I guess?..... a year ago Jupiter was around 13° wasn't it..... so maybe 7 or 8 arcsecond separation of red and blue.  Does that extra 2 or 3 really make all the difference between needing ADC and not?

Maybe the UK has a much more back-ended curve than Mauna Kea?

🤔

according to sky safari last year this time Jupiter was at about 16 deg and now about 25. From your curves Glob it gets quite exponential at that low an altitude so those 9 degrees difference are significant- certainly seems so! I haven’t been gazing at the planets the way i did last year as my attention has been taken by struggling to get round stars on a ccd but i will have a go with my adc tonight if it’s clear as forecast and see if it still makes a difference at higher power on Jupiter and Saturn 👍

Mark

[globular]

Cheers @markse68.
Maybe point your ccd at them with and without (if you can get the right distance with) and compare that to your visual impression too?
 

[John]

2 hours ago, Stu said:

....they just required too much faffing about....

 

That alone is usually enough to put me off using a piece of kit, unless it's capable of providing massive benefits.

I really don't like any additional complexity / faffing

[johninderby]

That’s why I sold my ADC. Just couldn’t bothered with the meesing about with it. 😕

[markse68]

They should all be geared with a single control knob to adjust prism-prism angle and rotation- makes it much easier to adjust by eye

Mark

[globular]

They should come with a bigger clear aperture too.

[Voyager 3]

I wanted to know why you northerners always complain about low elevation of planets in recent times . So one day in early August , I cooled the dob and pointed the scope soon after it got dark . Jupiter would have been at 10-15° altitude . 

 

My first reaction was no thanks . Bam ! What a blurry mess . The interesting thing was , the blurry , seeing effect was much more prominent and disturbing than the very mild bluish-reddish AD . Mind you , I never view the planets that low and I've never seen AD before on planets to be that much prominent , but still it wasn't the major factor in the poor views of Jupiter and Saturn . Fortunately I didn't feel the requirement of ADC , at least for my eyes , equipment and location .

Now now I feel pity for folks who live much Norther than me . Luckily this trend will improve in the coming years .

[astro_al]

22 hours ago, johninderby said:

That’s why I sold my ADC. Just couldn’t bothered with the meesing about with it. 😕

Same. Especially when used with my binoviewers. 

[globular]

No clear skies here since posting above... so have been unable to have another look for AD on a star rather than the planets.....

But I have seen these images of with and without ADC on Jupiter and Saturn.....

Now maybe it's just me, but both of these No ADC images do not look particularly red/blue fringed.... but are clearly less sharp than their With ADC comparatives.
I suspect this is what I'm seeing visually.... no serious colour issues.... but some lack of sharpness over what could be achieved with an ADC.

I've had some jaw dropping views of Jupiter recently (at 20° from my location)... will it really be any better with an ADC?

I guess I should either forget all about it or just buy one and try it. 🤔 
(Shame they all seem to have gone out of stock in the few days I've been pondering.)

 

[markse68]

8 hours ago, globular said:

(Shame they all seem to have gone out of stock in the few days I've been pondering.)

you resurrected this thread and caused a panic buy frenzy Glob 😉

I don’t have anything conclusive to report Glob as both clear nights I had to test were a bit gusty and with my long f8 dob wind is it’s worst enemy unfortunately. But when looking for it I could see the red blue smear and can see it in Saturn in your example image above. And I was able to compensate that out. Image just wasn’t steady enough to be able say how much if any sharper it was. But it should have been

Mark

[globular]

4 hours ago, markse68 said:

can see it in Saturn in your example image above.

Agreed.... a blueness between the rings and the planet at the top.... and very noticeable when comparing the with and without images.... but I'm not sure I would have spotted that as AD when viewing visually with only the without ADC option available to me....  i.e. I've probably seen something like that but not thought  "ahhh AD spoiling things".... (shrug).

I'll definitely have a closer look next clear night.... I do now have a better appreciation of what AD can do to the views .... which was my aim from this thread. 

 

Edited September 26, 2021 by globular

[jetstream]

I could have used an ADC the other night, but this device does not improve "seeing" eventhough it would have got the colours back together.

[IB20]

I have just been observing Jupiter and it was quite clearly displaying blue and red fringes at opposite sides of the disc. There were moments where details (EBs) on the disc were showing but there were also plenty of blurred and wobbly moments. It is quite windy outside though and checking the jet stream location, it is just clipping my skies.

So my questions are:

Is AD more likely to show in poorer seeing conditions? Anecdotally that seems to my experience so far.

Would an ADC help with removing these coloured fringes in conditions similar to these? This was in a 3” achromatic f10 refractor.