ADC- essential for planetary?

[BGazing]

6 minutes ago, Moonshane said:

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.

 

That was one of the first sci-fi shows shown in Yugoslavia, I think it was running on Monday nights. It was both great and awful. Used to make command screens out of plywood and take it to bushes to play. Bushes were starships, you know.

Yugoslav TV stations imported English shows in bulk, American imports were mostly reserved for the movies. Ask any Belgrade resident what his or her fav TV shows are and chances are half will say Monthy Python and the other half Only Fools and Horses.

[johnturley]

46 minutes ago, paulastro said:

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 😀.

 

I think the benefits of ADC's show up mainly in apertures greater than 6 in, as I stated in my previous post, on the night of 20/21 July my ZWO ADC significantly improved the view through my 14 in Newtonian (as I stated I can't previously recall having seen so much detail on Jupiter when it was so low down), whereas the improvement through my Esprit  150 was only marginal, hence I would not expect an ADC to give a big improvement with a SW 120 ED.

Local seeing conditions were also good for me on 20/21 July, ADC's will not do much to improve the view when seeing conditions are poor, which is probably another reason why some observers say they have found little benefit from using an ADC.

As I also stated, I don't faff about for a long time trying to align the ADC with the horizontal horizon, it would be too much of a pain in the neck doing this every observing session. 

John 

Edited July 23, 2020 by johnturley

[fate187]

My experience comes from a ZWO ADC, which I sold because it introduced astigmatism. The view in focus was sharper compared to without the device, but overall color rendition was quite pale. Nowadays I don't observe without an ADC anymore. Even for altitudes > 30° AD will get apparent with higher magnification.

Regarding experimenting around with GPC/Barlow/Bino/diagonal/worm hole generators: I think its part of todays possibilities to add refined equipment to get the best views. Granted, one should never forget to look up (or through the scope). Ultimately, the skies in middle/northern Europe are probably the most prohibitive feature we have to deal with

best regards

 

[fate187]

1 hour 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.

The bayonette system adds flexibility. I use it to quickly change between bino and mono, or other visual equipment parts, if necessary.

Picture of my visual back: 

 

[markse68]

3 minutes ago, fate187 said:

My experience comes from a ZWO ADC, which I sold because it introduced astigmatism. The view in focus was sharper compared to without the device, but overall color rendition was quite pale. Nowadays I don't observe without an ADC anymore.

Hi fate187, which adc are you using now?

At what focal ratio were you getting astigmatism? Did it affect planetary views?

Mark

[BGazing]

36 minutes ago, fate187 said:

The bayonette system adds flexibility. I use it to quickly change between bino and mono, or other visual equipment parts, if necessary.

 

I know. I was wondering whether the 'default' bayonette system of Baader binos adds optical path in comparison with the 'default' T2 coupling nut solution.

The bayonette system I linked is 15mm optical path, that is for sure.

[CraigT82]

5 hours ago, Moonshane said:

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.

You might find that you don't have enough inward focus travel if not using a barlow with the newt (common issue). Perhaps a barlow cell screwed directly onto the nose of the ADC and giving 1.5x ish may push the focus point out just enough and not amplify too much? 

[Moonshane]

You may be right Craig but it's the OOUK one and it usually has a 2" extension on it which I can remove. I can just reach focus with binos and a 1.7x GPC.My 12" and 16" are the same. I'll be doing a bit of trial and error.

[John]

Saturn and Jupiter are just to low for my 12 inch dob to get onto due to "clutter" around that horizon from my back yard where I do 99% of my observing. So while they are down there I'm using my refractors of 100mm - 130mm which seem to be doing rather well when the seeing is good - an ADC can't help with poor seeing as has been mentioned before in this thread.

Mars will be within reach my my 12 inch dob but may be high enough from here that an ADC is limited in what it can achieve.

If these devices are helping improve the views for others, that's good and it is interesting reading about their exploits with them

 

[mikeDnight]

I've not yet had chance to use a ADC, and if I'm being honest I'm not that desperate to try one. Adding another device to the light path that is demanding my attention isn't something I'd thrill about, and having to check a spirit level in the dark??  Atmospheric dispersion has never been an overwhelming issue with any scope I've ever used, but I dare say that some scope designs can be troublesome if they lose heat slowly, causing the dispersion effect to smear the view.  Presently the planet's are low, yet despite this they reveal significant detail in moments of steady seeing. It does seem though that some scopes struggle to show even generally easy to see detail such as Cassini's division. Perhapse the ADC may help with these scopes, but I'm not convinced theyed be worth the trouble or the cost in my case. 

I made a doodle of Saturn a couple of nights ago (No ADC) while it was quite low. Can't remember seeing any AD despite the planet being far from its best due to the atmosphere. Cassini's division was so so easy, as it generally is. Jupiter revealed festoons and garlands on the southern edge of the NEB and the GRS was visible in the SEB despite the view being softer than it would be when high in the sky. 

[JeremyS]

@John and @mikeDnight make important points. My experience of Jupiter and Saturn at the mo is that visually they are limited by unsteady seeing generally rather that AD (tho I can see role of ADC in imaging).

the other night my Tak 120 was besting the C9.25 on the two gas giants.

And it really is a case of grabbing those exquisite moments of good seeing, which an ADC won’t help with.

 

[Peter Drew]

Our local seeing has been ruined by the proximity of wind turbines, it's like having an extra jetstream!  On the same night as Mike H has described there was only a hint of the Cassini Division and only a couple of vague cloud belts on Jupiter despite using a SW 150ED, a good C8 and a 16" SCT.     ☹️

[JeremyS]

6 minutes ago, Peter Drew said:

Our local seeing has been ruined by the proximity of wind turbines, it's like having an extra jetstream!  On the same night as Mike H has described there was only a hint of the Cassini Division and only a couple of vague cloud belts on Jupiter despite using a SW 150ED, a good C8 and a 16" SCT.     ☹️

Maybe you can attach a motor to an ADC to rotate it in synch with the turbines, Peter?

[Peter Drew]

We're working on an anti wind device.    😀

[andrew s]

22 minutes ago, JeremyS said:

 

And it really is a case of grabbing those exquisite moments of good seeing, which an ADC won’t help with.

 

Is that really true @JeremyS.? In a moment of exquisite seeing the atmospheric dispersion should, if you have sufficient resolution and magnification, be most obvious. The visual equivalent to lucky imaging.

I grant that adjusting an ADC in poor seeing would be problematic if not impossible.  However, I can't escape  the idea (pedudice) that small scope preference in poor condition is due to the observer preferring an unresolved smaller shifting  image to a resolved larger dynamically blurring one. (Cell size above or below instrument aperture) Much as one pulls away from a pixelated image to see the whole.

Regards Andrew 

 

Edited July 23, 2020 by andrew s

[andrew s]

6 minutes ago, Peter Drew said:

We're working on an anti wind device.    😀

Don't tempt me.....

Regards Andrew 

[JeremyS]

12 minutes ago, andrew s said:

Is that really true @JeremyS.? In a moment of exquisite seeing the atmospheric dispersion should, if you have sufficient resolution and magnification, be most obvious. The visual equivalent to lucky imaging.

I grant that adjusting an ADC in poor seeing would be problematic if not impossible.  However, I can't escape  the idea (pedudice) that small scope preference in poor condition is due to the observer preferring an unresolved smaller shifting  image to a resolved larger dynamically blurring one. (Cell size above or below instrument aperture) Much as one pulls away from a pixelated image to see the whole.

Regards Andrew 

 

Visually, AD is a second order effect (In degrading detail) compared to seeing, in my experience. Whilst it might theoretically help to use an ADC I think the practicalities would be problematic for the reasons you state.

Might be worth an experiment of course. 

[johninderby]

Why did the wind turbine problem make me think of the interupters used on machine guns to fire through a spinning propellor. 😁😁😁

[JeremyS]

Talking of experiments, I’ve ordered this book to see if I can help @Peter Drew with his wind problem (I was tempted @andrew s)

[paulastro]

1 hour ago, Peter Drew said:

Our local seeing has been ruined by the proximity of wind turbines, it's like having an extra jetstream!  On the same night as Mike H has described there was only a hint of the Cassini Division and only a couple of vague cloud belts on Jupiter despite using a SW 150ED, a good C8 and a 16" SCT.     ☹️

Peter, I was going to suggest a course of action regarding the turbines, but I wont!!  The last time I made a joke about what to do about intruding street lights, I was reprimanded by a moderator.  Personally, I thought it was a good suggestion of mine - to write to the council's lighting dept and ask if they could kindly look into the matter.  🙂

[paulastro]

27 minutes ago, JeremyS said:

Talking of experiments, I’ve ordered this book to see if I can help @Peter Drew with his wind problem (I was tempted @andrew s)

Jeremy, dont tell my wife about this book or she'll be buying me a copy for Chistmas along with the usual socks.  🤒

[fate187]

5 hours ago, markse68 said:

Hi fate187, which adc are you using now?

At what focal ratio were you getting astigmatism? Did it affect planetary views?

Mark

I use the Gutekunst adc. See CN for some reports: https://www.cloudynights.com/topic/695135-gutekunst-adc/?view=findpost&p=10335854&hl=%2Bgutekunst

The astigmatism was seen with all my scopes I had at that time: SW120 equinox, LZOS 123 f/6 and I think the CFF185 f/6.8. Maybe the LZOS 130 f/9, I don't remember if I had this scope back then :D. Those are all but one not ideally slow scopes (frac wise), but the adc added little quality to the view. As others don't have this problem here, maybe I had a defective device?

4 hours ago, BGazing said:

I know. I was wondering whether the 'default' bayonette system of Baader binos adds optical path in comparison with the 'default' T2 coupling nut solution.

The bayonette system I linked is 15mm optical path, that is for sure.

You are probably right with the 15mm optical path (thats what Baader specified?!). Point is the easy way to connect the bino to another part via the T2 threaded bayonette system. In case of my set up I would need a 1.25" adapter on the diagonal, followed by the bino with 1.25" nosepiece. I regard this as less stable and probably also longer, especially the 1.25" adapter on the diagonal. Could be wrong though :).

[mikeDnight]

5 hours ago, andrew s said:

Is that really true @JeremyS.? In a moment of exquisite seeing the atmospheric dispersion should, if you have sufficient resolution and magnification, be most obvious. The visual equivalent to lucky imaging.

I grant that adjusting an ADC in poor seeing would be problematic if not impossible.  However, I can't escape  the idea (pedudice) that small scope preference in poor condition is due to the observer preferring an unresolved smaller shifting  image to a resolved larger dynamically blurring one. (Cell size above or below instrument aperture) Much as one pulls away from a pixelated image to see the whole.

Regards Andrew 

 

I can't help it - I have to bite!

Does anyone actually believe that atmospheric cell nonsense anymore?  For it to be at all feasible there would need to be just a single layer of atmospheric cells like a sheet of bubble wrap. In reality the cells overlap and are miles deep, so a small aperture would be just as equally hindered by them as a larger aperture. The argument often claims the larger aperture is hindered because it is looking through more cells. However, if you use two scopes of equal aperture (say 8"), one a reflector and one a refractor, the refractor will almost always give a better planetary image, discrediting the atmospheric cell argument.

Then as regards resolution, a small scope of good quality will resolve detail to its aperture limit. It doesn't present an unresolved image such as a pixelated view of a cooked image. So point source features that are be beyond the resolution limit of a small refractor for example, are easily detectablde if they are linear, despite being too fine to resolve, leaving many observers stunned in disbelief at the laser etched, highly detailed view. 

Edited July 23, 2020 by mikeDnight

[andrew s]

1 hour ago, mikeDnight said:

I can't help it - I have to bite!

Does anyone actually believe that atmospheric cell nonsense anymore?  For it to be at all feasible there would need to be just a single layer of atmospheric cells like a sheet of bubble wrap. In reality the cells overlap and are miles deep, so a small aperture would be just as equally hindered by them as a larger aperture. The argument often claims the larger aperture is hindered because it is looking through more cells. However, if you use two scopes of equal aperture (say 8"), one a reflector and one a refractor, the refractor will almost always give a better planetary image, discrediting the atmospheric cell argument.

Then as regards resolution, a small scope of good quality will resolve detail to its aperture limit. It doesn't present an unresolved image such as a pixelated view of a cooked image. So point source features that are be beyond the resolution limit of a small refractor for example, are easily detectable, leaving many observers stunned in disbelief at the laser etched, highly detailed view. 

I think it does hold up quite well . I will try to find the published research papers I read some years ago that supported this view. Do you know of any pubished evidence against it or have you perhaps studied it?

On comparing refractors and reflectors I think you need to look at why the best planetary images are from those terrible SCTs. Yes you need a larger reflector to give the same resolution as a refractor that's physics and well understood.  It is interesting aside to note P Lowell tended to stop down the 24" refractor for his observations.

On resolution, while the resolution limit is a convention it applies to reflectors and refractors alike. Physics limits what can be seen even if you don't  belive it. Small telescope have a more limited resolution than larger ones (assuming any central obstruction is accounted for correctly). There is no magic in optics.

I never claimed telescopes produced a pixelated image just used that as an example of where we tend to prefer small and sharp as to large and more blured. Just as you find a natural preferred magnification not too high and not too low.

So I have bitten back😜

Regards Andrew

PS I have tried to track down the papers I read years ago but it was in the age  of getting paper copies via the library! However, the Fried parameter is alive and well and the following might be worth a look.

https://www.telescope-optics.net/induced.htm

https://www.handprint.com/ASTRO/seeing1.html https://www.handprint.com/ASTRO/seeing2.html https://www.handprint.com/ASTRO/seeing3.html

and references their in.

Simple view here https://skyandtelescope.org/astronomy-equipment/beating-the-seeing/#:~:text=So will every other telescope,after bringing a telescope outdoors.

Most modern references concentrate on adaptive optics but the Fried parameter (https://en.wikipedia.org/wiki/Fried_parameter )  still persists.

Edited July 23, 2020 by andrew s

[BGazing]

1 hour ago, fate187 said:

I use the Gutekunst adc. See CN for some reports: https://www.cloudynights.com/topic/695135-gutekunst-adc/?view=findpost&p=10335854&hl=%2Bgutekunst

The astigmatism was seen with all my scopes I had at that time: SW120 equinox, LZOS 123 f/6 and I think the CFF185 f/6.8. Maybe the LZOS 130 f/9, I don't remember if I had this scope back then :D. Those are all but one not ideally slow scopes (frac wise), but the adc added little quality to the view. As others don't have this problem here, maybe I had a defective device?

You are probably right with the 15mm optical path (thats what Baader specified?!). Point is the easy way to connect the bino to another part via the T2 threaded bayonette system. In case of my set up I would need a 1.25" adapter on the diagonal, followed by the bino with 1.25" nosepiece. I regard this as less stable and probably also longer, especially the 1.25" adapter on the diagonal. Could be wrong though :).

Have you used barlow/powermate with your ZWO/ADC? I never used it with fracs without PM2.5?

I do not mind optical path and I love Zeiss/T2 system, it is just that Baader does not list if you are getting any additional optical path with it vis-a-vis the T2 coupling nut...  I am just curious...