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ADC- essential for planetary?


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26 minutes ago, Moonshane said:

I cannot think how it can align with the horizon in a newt as the focuser is perpendicular to it and at a slant. Hence my starting assumption that you align down the axis. The only thing I can think of is having the focuser vertical which would get you closeish.

ah yes good point well made

10 minutes ago, johninderby said:

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Not on your own John, somewhat perplexed myself now. 

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Just back from another superb seeing evening with the planets and did a few comparisons of with and without the ADC. This is the last time i’ll do such a thing as there is really no point in looking a

I couldn’t resist a little mod. 😁 The Altair doesn’t have a bubble level so thought I would add one so bought a rifle scope bubble level with a 40mm bore which fits the ADC perfectly. Just for Alt

I was clouded out, as usual. However I now have this awesome light-sabre-contraption ready for next time. I just need to find a step ladder to be able to look down into it!

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Hold up a spirit level to the front of the tube and look through the focuser with no ep so you can see the level and adjust it to horizontal. 

Mark the horizontal level you can see on your focuser with a pencil and that's your null point alignment for the ADC. Won't change from there for a alt az newt. 

The bubble is useless with newts as the horizon as seen through the scope won't be parallel with the true hotizontal 

 

More useful info from Martin Lewis here... http://www.skyinspector.co.uk/atm-dispersion-corrector--adc

Edited by CraigT82
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10 hours ago, Moonshane said:

Does that mean that you have to readjust throughout the night with an eq mount but not an altaz?

Yes on the bubble. Also on altaz if your diagonal is slightly rotated to the left or right in your focuser.

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If you don't have a bubble level and or can't see the horizon just line up with the direction of the dispersion as seen on the planet or a star.

After all that's what you are trying to compensate for. If you can't see it no need to worry anyway.

Nice link @CraigT82.

Regards Andrew 

Edited by andrew s
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4 hours ago, CraigT82 said:

Hold up a spirit level to the front of the tube and look through the focuser with no ep so you can see the level and adjust it to horizontal. 

Mark the horizontal level you can see on your focuser with a pencil and that's your null point alignment for the ADC. Won't change from there for a alt az newt. 

The bubble is useless with newts as the horizon as seen through the scope won't be parallel with the true hotizontal 

 

More useful info from Martin Lewis here... http://www.skyinspector.co.uk/atm-dispersion-corrector--adc

Just had a read of this, quite straightforward to align the ADC but tuning it is an altogether different thing. Thinking trial and error on tuning will be the order of the day. 

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46 minutes ago, johninderby said:

I have a plan. 🤔

Just twiddle with the levers until it works. 😁😁😁

To be fair for visual that's pretty much what he says.

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2 hours ago, bomberbaz said:

Just had a read of this, quite straightforward to align the ADC but tuning it is an altogether different thing. Thinking trial and error on tuning will be the order of the day. 

It's not as hard as it sounds... it's not an exact science... twiddle till you can't see any red or blue fringes! Be sure to have the levers adjusted equally either side of null point. With the planets so low and using big scope/long FL, you may not have enough correction even at max setting. In that case if you increase distance between eyepiece and ADC you'll gain more correction.

A good tip is each time you use the ADC make a note of the target altitide and the ADC lever position. Soon you'll have a library of what position you need to set it to by just looking up the target altitude (for that particular set up).

Edited by CraigT82
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Just had a thought... if you haven't done so yet, it's worth checking if your ADC is a righty or lefty (I.e. which way the prisms are stacked) as this will dictate whether you have the null point pointing left or right.

Nice and easy test for this here...

https://www.cloudynights.com/topic/525563-for-users-of-the-new-zwo-adc-important/

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didn't try mine last night, too hooked up on other things. 

However while doing a star test with the achro 102 on Arcturus I really noticed the prism split colouration on it. It was strikingly strong and a lot more than I had expected with the achro, quite remarkable.  

Had I had the time, i would have given it a go but there is always next time now I have a target to test it on. 

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9 minutes ago, bomberbaz said:

didn't try mine last night, too hooked up on other things. 

However while doing a star test with the achro 102 on Arcturus I really noticed the prism split colouration on it. It was strikingly strong and a lot more than I had expected with the achro, quite remarkable.  

Had I had the time, i would have given it a go but there is always next time now I have a target to test it on. 

Interesting to know.. looking forward to reading more on testing here

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2 hours ago, CraigT82 said:

Just had a thought... if you haven't done so yet, it's worth checking if your ADC is a righty or lefty (I.e. which way the prisms are stacked) as this will dictate whether you have the null point pointing left or right.

Nice and easy test for this here...

https://www.cloudynights.com/topic/525563-for-users-of-the-new-zwo-adc-important/

I just assumed that the spirit level on my ZWO ADC was intended to be on on the top of the unit when is use (which makes sense), which then puts the levers on the right, and is the way I have used mine.

I had more success with it on Jupiter last night (when atmospheric conditions were poor) through my 14in Newtonian, using it in conjunction with a Baader Neodymium filter, I simply moved the 2 levers in opposite directions until the false colour caused by atmospheric dispersion virtually disappeared.  I ended getting a more pleasing view of the planet through the 14 in, than through my 150 mm Esprit, normally the smaller refractor gives a better view when atmospheric conditions are poor, I didn't however try the ADC with the Esprit. 

The Baader Neodymium filter helps in particular on Jupiter through the 14 in, as otherwise the bright image tends to wash out some of the detail in the cloud belts.

John 

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12 hours ago, F15Rules said:

(In best Dragon's Den voice):

"I wish you all well, but this isn't my thing.

I'm out".

🥴😊

Dave

I feel the same Dave.

Good luck to those trying these things out though - it's interesting reading about their experiences.

 

 

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Just back from another superb seeing evening with the planets and did a few comparisons of with and without the ADC. This is the last time i’ll do such a thing as there is really no point in looking at them at their current altitudes without. I had my 10mm BCO in the ADC barlowed to 5mm and swapped back and forth with the 6mm BCO on its own. Jupiter Saturn and Mars all had orange tops and bluish bottoms with the 6mm. There was detail to see but it was soft compared to with the ADC. Despite a bit more magnification with the ADC (320x vs 266x) the ADC view was sharper on all of them- there was just more definition. Easiest to see why was when observing Jupiter’s moons. With the 6mm the moon’s were elongated with strong colour smearing stretching their form. With ADC they were perfectly round disks. I know which i prefer.

Mark

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6 hours ago, markse68 said:

Just back from another superb seeing evening with the planets and did a few comparisons of with and without the ADC. This is the last time i’ll do such a thing as there is really no point in looking at them at their current altitudes without. I had my 10mm BCO in the ADC barlowed to 5mm and swapped back and forth with the 6mm BCO on its own. Jupiter Saturn and Mars all had orange tops and bluish bottoms with the 6mm. There was detail to see but it was soft compared to with the ADC. Despite a bit more magnification with the ADC (320x vs 266x) the ADC view was sharper on all of them- there was just more definition. Easiest to see why was when observing Jupiter’s moons. With the 6mm the moon’s were elongated with strong colour smearing stretching their form. With ADC they were perfectly round disks. I know which i prefer.

Mark

Was that in your 8" dob @markse68? I was out with my 4" refractor and didn't see any colour smearing at about 140x. Are the effects of atmospheric dispersion more noticeable with larger scope due to their higher resolution?

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7 hours ago, markse68 said:

Just back from another superb seeing evening with the planets and did a few comparisons of with and without the ADC. This is the last time i’ll do such a thing as there is really no point in looking at them at their current altitudes without. I had my 10mm BCO in the ADC barlowed to 5mm and swapped back and forth with the 6mm BCO on its own. Jupiter Saturn and Mars all had orange tops and bluish bottoms with the 6mm. There was detail to see but it was soft compared to with the ADC. Despite a bit more magnification with the ADC (320x vs 266x) the ADC view was sharper on all of them- there was just more definition. Easiest to see why was when observing Jupiter’s moons. With the 6mm the moon’s were elongated with strong colour smearing stretching their form. With ADC they were perfectly round disks. I know which i prefer.

Mark

Absolutely agreed. I did the same comparison again the night before last with and without an ADC on a Mak 180. The increase in detail was very significant, and the contrast with Jupiter's belts very obviously improved. Looking at Saturn, Cassini really showed well with the ADC, barely without, and I'm sure the moon count was better as well. Adding a Baader Nd filter did make a modest improvement overall as well, but of course at the expense of colour verity. I had another look last night as well, but the seeing was seriously rubbish, so I gave up and admired the comet from a nearby darker site.

Referring to some of the above posts, I've never had an issue with adjusting the ADC; I just make sure that the spirit level is roughly aligned with the horizon, and then set the levers nearly at the max position at about the same angle above and below horizontal. If you have the levers on the wrong side, it is obvious by the orange and blue fringes on Jupiter. For my scope (mirror diagonal), the levers are on the LHS visually, RHS for imaging (without a diagonal).

Chris

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21 minutes ago, astro_al said:

Was that in your 8" dob @markse68? I was out with my 4" refractor and didn't see any colour smearing at about 140x. Are the effects of atmospheric dispersion more noticeable with larger scope due to their higher resolution?

Yes it was with the fullerscope astro_al. You may be into something there- I was using higher power too. Actually i spent most of the evening using the 18mm BCO barlowed to 9mm for 178x. Lower powers increase contrast on the planets I find but I didn’t do any comparisons at that magnification range. I swapped to the 10mm when Ganymede slithered behind the limb as the GRS rounded same limb- what a sight!. The distortion of the moons made it super obvious and Mars being a fair bit lower.  On the disk maybe smearing is too strong a word- the outline didn’t appear distorted  without the adc but the colour balance was very obviously. 

Magnification clearly amplifies the differences and aperture I think must have a role to play too- the big observatories take it very seriously.

Edited by markse68
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Makes sense Mark, thanks. My biggest scope is 6" and I have to mount that on a pier in my back garden from where the view south is a bit obstructed. This means that the planets need to be higher to be seen, which is why at the moment I go out the front with a grab and go setup from where I can see to a lower altitude.

Small scopes for low altitude planetary viewing out the front, and larger scope for higher altitude planetary viewing out the back. Maybe not much need for an ADC for me, although I will see how I get on with Mars with the bigger scope later in the year. 

Edited by astro_al
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As far as I read, in the UK at least the planets hardly ever go higher than the level that an ADC will benefit the view. I have never really felt the need other than once through my 12" dob but it will be interesting to try and it may be one of those things that you get by without until you use it and then wow.

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Had another go with my ZWO ADC coupled with a Baader Neodymium filter last night, despite a significant breeze, viewing conditions were much improved on the previous evening, and through my 14in Newtonian I can't recall previously having seen so much detail on Jupiter when it was so low down, the great red spot was obvious, and I also observed the Ganymede occultation.

Like Chris, I didn't mess about attaching a camera and running the camera through Firecapture or Sharpcap to obtain the optimal setting as per the instruction manual (I don't have an astro camera anyway, just a digital SLR). I simply pointed the telescope horizontal, and then rotated the ADC so that the spirit level (on the top) indicated horizontal, and then when viewing adjusted the 2 levers by an identical amount so as to minimise the amount of false colour due to atmospheric dispersion, I think in the case of Jupiter it was somewhere between 0.5 and 1 on the scale.

I also tried out the ADC through my Esprit 150, in this case the effect was more marginal, and the optimal position with the levers was less than 0.5. I therefore get the impression that larger reflectors benefit more from an ADC than smaller refractors, and that they will probably be of limited benefit in the case of 4 in or smaller refractors.

John 

 

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