Zwo Atmospheric Dispersion Corrector

[Relpet]

Mars has not been a good subject since I took up astronomy three years ago but everyone is getting pretty excited for 2018.  From Northern Europe it will be low in the sky and various experts, Damian Peach, Martin Lewis et al are recommending an ADC to improve observing and imaging.  The ZWO ADC comes recommended and is more affordable than previous ADCs.  At the age of 78 this may be my last chance to get up close and personal with Mars.  With a 3" APO refractor, 5" Newt and 8" Dob currently in the armoury am I likely to get any perceived benefit from an ADC using any of these 'scopes, please?

Observing latitude will be 43 degrees north.  Any advice, positive or negative will be very helpful.

[si@nite]

You will get the best results using an adc when imaging at low elevation with a colour camera, also the bigger the aperture the more benefit you get, 200mm upwards!

You will also benefit when using mono cameras too, the effect is much less as the filters help too cut out some of the dispersion anyway! Hope this helps!

Regards Simon!

[Relpet]

Thanks Simon.  There are some big Dobs (10" to 16") turn up s/h in France from time to time for observing.  If low altitude observing is improved with an ADC a Mars Party would be on the cards for friends, villagers and visitors come July but if there's no improvement on the blurred red spot I've seen so far over the last few years I wouldn't even think about it.  I'm still very much a beginner with imaging so that would be a secondary consideration.

Best wishes

Peter

[Merlin66]

The image shows the effects of atmospheric dispersion at lower altitudes.

[Relpet]

8 hours ago, Merlin66 said:

The image shows the effects of atmospheric dispersion at lower altitudes.

Thanks for that, Merlin.  (The same Merlin engine powers your Spitfire and my Hurricane!).

[Merlin66]

Yeah,

the Merlin66 was the best of the line......

 

[JPAG]

On 12/28/2017 at 18:24, Relpet said:

 At the age of 78 this may be my last chance to get up close and personal with Mars.

Last chance? At 78??? Oh, come on, I bet you still have many years ahead to observe Mars!

[Relpet]

18 hours ago, JPAG said:

Last chance? At 78??? Oh, come on, I bet you still have many years ahead to observe Mars!

Obrigado, JPAG.  Your encouragement is greatly appreciated and though I ain't knock, knock, knockin' on heaven's door just yet how often does Mars come this close?  The Association of Lunar and Planetary Observers says this:

The perihelic apparition of Mars will prove to be one of the most favourable since the 2003 apparition when the Red Planet came closest to Earth in 59,635 years (the year 57,617 BC).  

In 2003, Mars came within 34.6 million miles (55.7 million km) to Earth, closer than at any time in over nearly 60 thousand years! It’ll be only 1.2 million miles (just under 2 million km) farther away in 2018. Closest approach for Mars in 2018 will take place about two weeks after the opposition date, on July 31.

The next closest might not be until 2050, by which time I do confidently expect to be stardust, hence my possibly pessimistic forecast.

Best wishes and thanks again.

 

 

[Pondus]

7 hours ago, Relpet said:

Obrigado, JPAG.  Your encouragement is greatly appreciated and though I ain't knock, knock, knockin' on heaven's door just yet how often does Mars come this close?  The Association of Lunar and Planetary Observers says this:

The perihelic apparition of Mars will prove to be one of the most favourable since the 2003 apparition when the Red Planet came closest to Earth in 59,635 years (the year 57,617 BC).  

In 2003, Mars came within 34.6 million miles (55.7 million km) to Earth, closer than at any time in over nearly 60 thousand years! It’ll be only 1.2 million miles (just under 2 million km) farther away in 2018. Closest approach for Mars in 2018 will take place about two weeks after the opposition date, on July 31.

The next closest might not be until 2050, by which time I do confidently expect to be stardust, hence my possibly pessimistic forecast.

Best wishes and thanks again.

 

 

Mars will be way too low for me (at 59N) in 2018.

However :  Mars will also be very close to us autumn 2020 too, and considerably higher above the horizon. 

I`m certainly expecting some magnificent views of this planet then  .

Rune

[Relpet]

Thanks, Rune.  I have very happy memories of a night in June about 40 years ago with a Norwegian family drinking home-brew at a village on the side of a fjord just north of Trondheim, long before I took up stargazing.  As it never got dark at all that night I'm guessing astronomy is more of a winter pastime that far north.  Good luck in 2020.  I hope I'm still around!

Cheers

[mikeDnight]

On 30/12/2017 at 15:41, Relpet said:

Obrigado, JPAG.  Your encouragement is greatly appreciated and though I ain't knock, knock, knockin' on heaven's door just yet how often does Mars come this close?  The Association of Lunar and Planetary Observers says this:

The perihelic apparition of Mars will prove to be one of the most favourable since the 2003 apparition when the Red Planet came closest to Earth in 59,635 years (the year 57,617 BC).  

In 2003, Mars came within 34.6 million miles (55.7 million km) to Earth, closer than at any time in over nearly 60 thousand years! It’ll be only 1.2 million miles (just under 2 million km) farther away in 2018. Closest approach for Mars in 2018 will take place about two weeks after the opposition date, on July 31.

The next closest might not be until 2050, by which time I do confidently expect to be stardust, hence my possibly pessimistic forecast.

Best wishes and thanks again.

 

 

I'm not sure an adc will be of any real benefit visually. If your scopes are thermally stable and you continue to critically adjust the focus so as to keep the image as sharp as possible, you're bound to get some good views. In 2003 Mars was high in the UK skies and with a diameter of 25arc seconds it was spectacular. Sadly Mars will be much lower in the sky this time round from the northern hemisphere, but its still going to be large, and it will reveal a wealth of detail to the patient observer. Don't give up if the disc looks featureless! 

In 2015 - 2016 apparition the tiny disc needed careful study because the planet was so low. There was lots to see though, and if you make a rough sketch each time you observe it, you'll soon begin to realise there's more on view than first meets the eye.

Attached are a few sketches from 2015/16 using a 4" refractor.

 

[Relpet]

Thanks, Mike.  That's quite encouraging.  I bought my APO frac last summer, since when the skies were entirely unhelpful, even in SW France.  It's hardly been used but my equipment is all kept in an unheated barn so, usually, ready for immediate action without further acclimatisation.  I bought it for wide field but have since bought a Baader EP with tuning rings that should enable me to use it for planetary.  The 8" Dob usually gives high quality planetary views and even my Celestron 4SE gives sharp planetary views under good conditions.  It's the low altitude that bothers me.  It will be higher in the sky compared to any part of Britain at my latitude but still far from ideal.  In spite of encouragement from elsewhere my views of Mars have so far been so dismal I do see this summer as possibly a once in a lifetime chance for the best spectacle, hence my original enquiry.  There has been very little feedback so it would appear the ADC is not a "must-have" in everyone's arsenal.

Thanks again.

Peter

[BGazing]

Got my ADC from FLO, will see how it performs visually in SCT8. If the improvement is marginal, I'm sure my AP friends will put it to better use. 

[Relpet]

On 1/5/2018 at 11:43, BGazing said:

Got my ADC from FLO, will see how it performs visually in SCT8. If the improvement is marginal, I'm sure my AP friends will put it to better use. 

Thanks.  I would be very interested to know how you get on.

[BGazing]

On 07/01/2018 at 01:23, Relpet said:

Thanks.  I would be very interested to know how you get on.

I've finally had the chance to test in on Jupiter a week ago in my C8. Jupiter was low, around 25 degrees. Without ADC the top was blue, dispersion galore. Once I have set up the corrector and adjusted it (no biggie, keeping the diagonal straight and now to the side ensures fairly easy horizontal levelling of the white lever) the blue has cleaned up almost completely, I would say. Pity that we had jetstream, so I had to keep it at 130 and it was smudged, but for me and other fellas who were with me that night at the mini star-party the effect was obvious.

So far thumbs up from me. I will try it in 7.4 frac but with barlow in front, once I get the little Tak in my greedy hands.  

[chiltonstar]

It would be interesting to hear more accounts of visual observing with an ADC to see whether it is worth trying during the upcoming Mars season (particularly from Peter if he goes down that path, although with that location, he already has 9 degrees elevation or more compared with UK sites!)

Pity ZWO don't make an adaptive optics seeing corrector at the same price - that would be attractive as I suspect that most of us suffer more from seeing issues at low altitudes than refraction problems!

Chris

 

[Cosmic Geoff]

19 hours ago, BGazing said:

I've finally had the chance to test in on Jupiter a week ago in my C8. Jupiter was low, around 25 degrees. Without ADC the top was blue, dispersion galore. Once I have set up the corrector and adjusted it (no biggie, keeping the diagonal straight and now to the side ensures fairly easy horizontal levelling of the white lever) the blue has cleaned up almost completely, I would say. Pity that we had jetstream, so I had to keep it at 130 and it was smudged, but for me and other fellas who were with me that night at the mini star-party the effect was obvious.

That's interesting. Given the chart posted above for this topic, I am not too surprised.  I'm tempted to order an ADC.

[BGazing]

15 hours ago, chiltonstar said:

It would be interesting to hear more accounts of visual observing with an ADC to see whether it is worth trying during the upcoming Mars season (particularly from Peter if he goes down that path, although with that location, he already has 9 degrees elevation or more compared with UK sites!)

Pity ZWO don't make an adaptive optics seeing corrector at the same price - that would be attractive as I suspect that most of us suffer more from seeing issues at low altitudes than refraction problems!

Chris

 

LOL true. One of the guys watching with me Saturn at 15 deg (just for the kicks) commented that it is 'the worst Saturn ever'. 

I am moderately optimistic about ADC in the upcoming years, and this summer in particular. Will be on Kefalonia in Greece for the Mars opposition, it will peak at 30 degrees, hope that ADC will make a difference. Plenty of time to test its effect in C8 until then, and perhaps FC100 with barlow before the ADC. I understand that the f ratio has to be above 10 either in native mode or with a barlow before the ADC.

[chiltonstar]

Many of us use colour filters for low angle planets which can remove the refraction fringing effect such as a Baader Fringe Killer; in my case I often use a green filter which trims blue and red for this. I wonder if the ADC is more or less effective than this approach?

Chris

[Stu]

50 minutes ago, chiltonstar said:

Many of us use colour filters for low angle planets which can remove the refraction fringing effect such as a Baader Fringe Killer; in my case I often use a green filter which trims blue and red for this. I wonder if the ADC is more or less effective than this approach?

Chris

I think with filtering you are losing light, but the ADC keeps all (other than normal losses to reflection/absorption) of the light, and just shifts the different frequencies so they coincide. I think this should give a better view than just filtering. Worth a comparison though.

[geoflewis]

On 16/03/2018 at 08:43, chiltonstar said:

It would be interesting to hear more accounts of visual observing with an ADC to see whether it is worth trying during the upcoming Mars season

I use an ADC primarily for imaging but I did also use it last year for visual observing of Saturn and it made a significant improvement, getting rid of the horrendus fringing to the rings that was seen without the ADC. I will certainly be trying it again with both Mars and Saturn later this year for visual and imaging.

[chiltonstar]

25 minutes ago, Stu said:

I think with filtering you are losing light, but the ADC keeps all (other than normal losses to reflection/absorption) of the light, and just shifts the different frequencies so they coincide. I think this should give a better view than just filtering. Worth a comparison though.

Yes, well worth a comparison! I think with Mars I wouldn't worry about throwing a little bit of light away* whereas with Saturn this might be more of an issue.

Chris

* for comparison, do we know the light transmission of the ADC, after all there are a few optical surfaces....??

[Stu]

http://skyinspector.co.uk/atm-dispersion-corrector--adc

[chiltonstar]

24 minutes ago, Stu said:

http://skyinspector.co.uk/atm-dispersion-corrector--adc

Nice review - I want one! 

Chris

[Stu]

55 minutes ago, chiltonstar said:

Nice review - I want one! 

Chris

I confess I struggled with the extra faff when I had one, it seemed to get in the way of me enjoying observing but it might be worth trying again. Wonder if they work with binoviewers ok?