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markse68

ADC- essential for planetary?

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Posted (edited)
13 minutes ago, Peter Drew said:

I've just ordered a ZWO ADC from FLO.  I have a large range of telescope types and apertures to try it on so look forward to the experiments.     🙂

We look forward to your results.  When I was goggling ADC's it soon became obvious they were being used by the big boys at ESO, Kleck and now , soon to be,Todmorden .

Regards Andrew 

Edited by andrew s
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1 minute ago, andrew s said:

We look forward to your results.  When I was goggling ACD's it soon became obvious they were being used by the big boys at ESO, Kleck and now , soon to be,Todmorden .

Regards Andrew 

Not in that league I'm afraid, I'll be using an ADC.     🙂

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3 minutes ago, Peter Drew said:

Not in that league I'm afraid, I'll be using an ADC.     🙂

Oops I intended ADC. Must type slower!

Regards Andrew 

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There will indeed be a higher degree of AD visible with larger aperture. For double stars I also use the ADC to properly split binaries, that are aligned along the a north/south direction. Even for very low mag double stars I tune my ADC until I see a clear split, because color is almost not noticeable the less bright the stars are. I have done this often now with my FC100DC.

The AD effect is way more pronounced in my larger fracs.

regards

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I'm following this thread with interest as I have a 5" achro with my sights set on Mars (for me THE target that I'm so excited about). I shall have to go on a selling fest to afford one mind. I need to feel its worth it.

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Next stop ADC with binos. I will try it the next couple of days. Now the trick is one has to get GPC before the ADC body, and the ADC body alone is 30mm, which will push 2.6 GPC in Tak to over 3x easily...and possibly more. This might not be that bad in itself.

But to use ZWO ADC body on T2 diagonal also means that I will have to use binos at an angle (because ADC when fully screwed is slightly slanted) or use ADC with 1.25 nose and inserted into diagonal with eyepiece clamp. That is 32 additional mms of backfocus, I think I have them but will check.

C8 same thing, except that I do not use GPC before ADC but in the binos (1.25) to bring bino forward and avoid aperture reduction. Here I will probably have to opt for slanted binos because 1.25 nose on ADC would add 100mm of focal length...and there's plenty of focal length to start with and the f/ ratio is already pretty high.

The only way to rotate ADC on T2 diagonal without eyepiece clamp would be this https://www.teleskop-express.de/shop/product_info.php/info/p7744_Baader-2456322---Heavy-Duty-T2-Quick-Changing-System.html but it saves just 15mm of optical path. Not sure if worth the hassle.

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Can you use gpcs in mono views instead of the Barlow? I have three types (1.25x, 1.7x and 2.6x)

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sorry got lost on this thread, what is a gpc

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Glass path corrector  used with bino viewer I think.

Regards Andrew 

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50 minutes ago, bomberbaz said:

sorry got lost on this thread, what is a gpc

As Andrew says it’s a glass path corrector. A binoviewer adds around 180mm to the focal length meaning you can’t get focus with some scopes. The GPC shortens the the focal length ( 2.6x GPC Gives you the 180mm back & gives 2.6x Barlow). I need it on my 80mm F7, but ok with my MAK127. Thanks Andy.

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Ah yes, seen them mentioned before now you remind me. I only use the binoviewers with the mak so it isn't a problem that I come across.

Thanks

Steve

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Posted (edited)

GPC should only be used in combination with binos, because they are designed to reduced spherical abberation introduced by the binos. If you have a slow scope with/or a mirror bino a GPC may not be necessary. 

18 hours ago, Moonshane said:

Can you use gpcs in mono views instead of the Barlow? I have three types (1.25x, 1.7x and 2.6x)

 

Be careful positioning the GPC in front of the ADC. This may be too much distance and can introduce abberations by doing so. I tried placing a 1.25 x GPC in front of the diagonal/bino instead of Diagonal/GPC/bino and have seen quite severe color fringing.

 

edit: I add, that I think I used a GPC/ADC/diagonal/bino combo when I saw the effect of fringing.

20 hours ago, BGazing said:

Next stop ADC with binos. I will try it the next couple of days. Now the trick is one has to get GPC before the ADC body, and the ADC body alone is 30mm, which will push 2.6 GPC in Tak to over 3x easily...and possibly more. This might not be that bad in itself.

But to use ZWO ADC body on T2 diagonal also means that I will have to use binos at an angle (because ADC when fully screwed is slightly slanted) or use ADC with 1.25 nose and inserted into diagonal with eyepiece clamp. That is 32 additional mms of backfocus, I think I have them but will check.

C8 same thing, except that I do not use GPC before ADC but in the binos (1.25) to bring bino forward and avoid aperture reduction. Here I will probably have to opt for slanted binos because 1.25 nose on ADC would add 100mm of focal length...and there's plenty of focal length to start with and the f/ ratio is already pretty high.

The only way to rotate ADC on T2 diagonal without eyepiece clamp would be this https://www.teleskop-express.de/shop/product_info.php/info/p7744_Baader-2456322---Heavy-Duty-T2-Quick-Changing-System.html but it saves just 15mm of optical path. Not sure if worth the hassle.

best regards

 

Edited by fate187
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Been flipping between this and a thread regarding binoviewing and if my understanding is correct that in a slow scope (F10 or F12)  if I wanted to use binoviewers I could arrange my kit in the following order.

Diagonal - ANC - Barlow - Bino/Eyepieces.

The reason I ask is that the increase in the focal train when using binoviewers means a 2x barlow is actually around a  4x increase. So if you then stick the ADC after the barlow you are probably up over x5.

Can anybody add weight to this as I am thinking of having a go with the frac and binoviewers. 

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ANC?

You are probably right, that you will get a >>2x magnification factor. And according to my experience your will add "a lot" back focus distance. That means you need extension tube to come into focus.

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I thought the Barlow had to be scope side of the ADC?

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Another issue with binos and an ADC is that it would be a lot of height to reach in order to see anything. Especially with the scope at a low angle.

 

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1 minute ago, Moonshane said:

I thought the Barlow had to be scope side of the ADC?

It doesn't have to be if the scope has a long native FL ,but generally much better to be ahead of the ADC.

Lots of good info on this in Martin Lewis' ADC part 2 Web page that I linked to earlier.

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Cheers Craig

I have printed it for reading so will digest 👍

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Just had a read and for my f11 6" Newt, I hope I might just get away with no barlow for visual. I'll try it and see what the view is like.  The issue with a barlow would be that assuming 4x amplification, it would mean a 6.4m focal length LOL. This would make my 27mm Panoptic a high power planetary eyepiece at 237x.

That said I am more likely I think to use my 120mm Equinox. Over the next week I am hoping to actually put the thing into play.

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12 hours ago, bomberbaz said:

Been flipping between this and a thread regarding binoviewing and if my understanding is correct that in a slow scope (F10 or F12)  if I wanted to use binoviewers I could arrange my kit in the following order.

Diagonal - ANC - Barlow - Bino/Eyepieces.

The reason I ask is that the increase in the focal train when using binoviewers means a 2x barlow is actually around a  4x increase. So if you then stick the ADC after the barlow you are probably up over x5.

Can anybody add weight to this as I am thinking of having a go with the frac and binoviewers. 

Yes, you can do it. I use ADC in mono on my SCT without any barlowing. I will use binos after ADC in SCT, but will insert 1.25 gpc in bino body for reducing focal length and possible aperture loss.

Once you hit f/10 with our run of the mill ADCs I think you're OK, you are trading one aberration for another at equal exchange rate. There's a good primer on that somewhere...

 

I tried ADC with binos last night in the Tak. Two photos attached, the first one where the diagonal remained as is, GPC inserted into 1.25 nose of the ADC (it won't go into ZWO ADC nose, had to swap it with the Baader one), then ADC and Bino mounted on top of ADC EP holder via quick coulpling (top is T2 threaded). This adds around 50mm of distance between GPC and bino and ups the magnification factor SIGNIFICANTLY. Not sure how much it was but surely way over 3x. I am not sure what is the exact figure.

Second picture is threading GPC on the T2 diagonal, then threading directly ADC on the diagonal, the rest like the first scenario (bino threaded on that EP holder), This merely reduces lever but the magnification remains the same. I did not have to remove one of the extensions on my scope. With GPC ZWO threads almost perpendicular and adjusting it to the horizon requires slight slanting. I had ample space tonight but that might be uncomfy during balcony operations...

I am waiting for a 2mm male-to-male T2 ring to arrive from FLO which will dispense with that long EP holder on ADC and reduce GPC magnification factor by a long margin.

Finally, another possibility (which I might try) is Powermate 2.5, T-Ring adapter, ADC then 1.25 GPC threaded into bino...Powermate would give about 2x at this distance from the focal plane and together with 1.25 GPC would come close to 2.5x magnification overall with good color correction and also (because of the PM) possibility to rotate ZWO in the clicklock 1.25 holder of the diagonal.

As for the visuals...it is better with the ADC. Requires only a slight correction (you can see that the levers are fairly close) but that is all it takes. I understand that the correction is dependant of the focal length and elevation, Jupiter was at 25 degrees for me here and the F/L was bumped to over 2000mm due to placement of the GPC. That is the same correction I normally use in C8 (similar focal length).

photo_2020-07-22_22-50-01.jpg

photo_2020-07-22_22-22-15.jpg

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9 minutes ago, BGazing said:

Yes, you can do it. I use ADC in mono on my SCT without any barlowing. I will use binos after ADC in SCT, but will insert 1.25 gpc in bino body for reducing focal length and possible aperture loss.

Once you hit f/10 with our run of the mill ADCs I think you're OK, you are trading one aberration for another at equal exchange rate. There's a good primer on that somewhere...

 

I tried ADC with binos last night in the Tak. Two photos attached, the first one where the diagonal remained as is, GPC inserted into 1.25 nose of the ADC (it won't go into ZWO ADC nose, had to swap it with the Baader one), then ADC and Bino mounted on top of ADC EP holder via quick coulpling (top is T2 threaded). This adds around 50mm of distance between GPC and bino and ups the magnification factor SIGNIFICANTLY. Not sure how much it was but surely way over 3x. I am not sure what is the exact figure.

Second picture is threading GPC on the T2 diagonal, then threading directly ADC on the diagonal, the rest like the first scenario (bino threaded on that EP holder), This merely reduces lever but the magnification remains the same. I did not have to remove one of the extensions on my scope. With GPC ZWO threads almost perpendicular and adjusting it to the horizon requires slight slanting. I had ample space tonight but that might be uncomfy during balcony operations...

I am waiting for a 2mm male-to-male T2 ring to arrive from FLO which will dispense with that long EP holder on ADC and reduce GPC magnification factor by a long margin.

Finally, another possibility (which I might try) is Powermate 2.5, T-Ring adapter, ADC then 1.25 GPC threaded into bino...Powermate would give about 2x at this distance from the focal plane and together with 1.25 GPC would come close to 2.5x magnification overall with good color correction and also (because of the PM) possibility to rotate ZWO in the clicklock 1.25 holder of the diagonal.

As for the visuals...it is better with the ADC. Requires only a slight correction (you can see that the levers are fairly close) but that is all it takes. I understand that the correction is dependant of the focal length and elevation, Jupiter was at 25 degrees for me here and the F/L was bumped to over 2000mm due to placement of the GPC. That is the same correction I normally use in C8 (similar focal length).

 

Thanks for the reply, it was more or less as I expected.

I think the thing here is with barlow, powermates and the focal train overall is to experiment and see which gives you the best outcome in terms of what I as an individual like. Things like vignetting are unlikely to be a concern for visual planetary but might be if I decide to stick a ZWO camera in for a few planetary shots.

Being f10 and above does help me here as I have a little more flexibility and I have a box full of extension tubes so we shall see how I get on.

Thanks.

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Having trawled some threads for refractor measurement it appears that 2.6 GPC is around 2.46x when mounted on the diagonal and bino threaded directly on it and that the values are growing in a linear fashion with additional optical path, see here https://www.cloudynights.com/topic/397010-glasspath-magnification-factors-including-the-26/

For every 100mm of additional optical length between bino and GPC there appears to be 1.6 increase in magnification, approximately.

Mounting in front of BBHS T2 would add 48mm optical path, so 0.77 in plus, for a total of  3.23x.

Mounting in front of T2 zeiss prism would add 38mm optical path so 0.6 mag more, total 3.06x.

ZWO ADC body alone is 29mm, so 0.46 mag. If GPC is screwed into the diagonal, the magnification is 2.92x. Mounting bino on that ADC EP holder is probably around 17-18 additional millimetres, so around 0.28 more mag, altogether 3.2x. That's how it felt last night. :)  So mounting it in front of BBHS and in the default position with the ZWO brings to similar magnitude. If 2mm optical path male to male T2 ring is used instead of the EP holder this reduces magnitude to around 2.95x.

I do not know whether mounting via Zeiss bayonette adds anything in comparison with the T2 nut ring. This combination  https://www.teleskop-express.de/shop/product_info.php/language/en/info/p7744_Baader-2456322---Schwerlast-T2-Wechselsystem.html is listed as 15mm optical path, but it is difficult to know how much it adds to the default option and is in any event a different construction of bayonette than the one used in MBII. But if one wants to use it to connect ADC to diagonal and allow for rotation it would apparently add 0.24x.

Hope my math is correct, apologies if it is not. :)

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12 minutes ago, BGazing said:

Having trawled some threads for refractor measurement it appears that 2.6 GPC is around 2.46x when mounted on the diagonal and bino threaded directly on it and that the values are growing in a linear fashion with additional optical path, see here https://www.cloudynights.com/topic/397010-glasspath-magnification-factors-including-the-26/

For every 100mm of additional optical length between bino and GPC there appears to be 1.6 increase in magnification, approximately.

Mounting in front of BBHS T2 would add 48mm optical path, so 0.77 in plus, for a total of  3.23x.

Mounting in front of T2 zeiss prism would add 38mm optical path so 0.6 mag more, total 3.06x.

ZWO ADC body alone is 29mm, so 0.46 mag. If GPC is screwed into the diagonal, the magnification is 2.92x. Mounting bino on that ADC EP holder is probably around 17-18 additional millimetres, so around 0.28 more mag, altogether 3.2x. That's how it felt last night. :)  So mounting it in front of BBHS and in the default position with the ZWO brings to similar magnitude. If 2mm optical path male to male T2 ring is used instead of the EP holder this reduces magnitude to around 2.95x.

I do not know whether mounting via Zeiss bayonette adds anything in comparison with the T2 nut ring. This combination  https://www.teleskop-express.de/shop/product_info.php/language/en/info/p7744_Baader-2456322---Schwerlast-T2-Wechselsystem.html is listed as 15mm optical path, but it is difficult to know how much it adds to the default option and is in any event a different construction of bayonette than the one used in MBII. But if one wants to use it to connect ADC to diagonal and allow for rotation it would apparently add 0.24x.

Hope my math is correct, apologies if it is not. :)

This is excellent info - thank you!

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Totally off topic but I just noticed your avatar and loved Blakes 7 when I was a kid. In fact I was at an event in Manchester for the opening of a sci-fi themed night club called Fab Cafe  http://www.fabcafe.co.uk/  and Gareth Thomas was there as the VIP.

 

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Posted (edited)
On 12/07/2020 at 15:17, John said:

I don't use one and my views of the planets over the past few nights have been pretty good with my ED120 and a small mak last night. Plenty of detail and no AD effects that I could see. I could see the Cassini Division and the main equatorial cloud belt with the 90mm mak last night plus 4 belts on Jupiter and festoons coming from the S side of the NEB. The ED120 showed quite a bit of detail on Mars and a nicely defined south polar cap. I had no issues with CA around Venus when it was well placed a little while back.

If I could borrow one I might give an ADC a go but I'm not exactly unhappy with the planetary views as things are :dontknow:

Maybe an ADC addresses more localised observing issues ?

 

 

 

Thanks John.  I've only just come across this thread.  I came in on page 6, and to be honest I was quite shocked  with some comments about how poor the views some people were currently getting of Saturn, Jupiter and even Mars.  Even to the extent of indicating it wasn't worth observing planets at all below certain altitudes. I was pleased to see your post.

My latest observations of the above planets were made on the night of July 20th/21st and were very much like your own observing experiences.  In fact they were so good, despite not getting into bed until 4am, I couldn't sleep for a while as I was thinking about how great the night had been!, including nice views of the GRS transit, and alovely wiew of Mars with Syrtis Major well placed as well as other features, Saturn was just fabulous.

As you suggested all sorts of things could account for peoples viewing experiences.  Local seeing conditions, using too large apertures for the conditions, the observers experience, the type and quality of the optics used, etc etc.

I've never used an ADC, - from what people are saying it seems rather a hassle to me.  I think I'd rather use the time observing and making the most of any periods of good seeing.

For the record, I was also using a SW 120ED as well, but other telescopes are available 😀.

 

Edited by paulastro
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