Nepture and Uranus Magnifications

[Littleguy80]

Last night, I went hunting for the planets beyond Jupiter and Saturn in the solar system. First target was Neptune. I used the star Hydor as my starting point and moved slightly east and found Neptune in line with 81 and 82 Aqr. The pale blue colour was very subtle and I had to compare against the white stars next to it to really notice it. I used this same tactic with the Blue Snowball nebula recently. At 180x, it was still very small, barely larger than a star. I've read reports describing Neptune as a pale blue disc. My scope won't support much beyond 180x but I may go back and try pushing it up higher with my barlow.

Uranus was a little trickier to find at first. The star Kullat Nunu was my starting point this time and I had to use the SkySafari app to make a positive identification of Uranus. At 180x mag, Uranus was a bright white disc. I was pleased to see this showing as a disc and was more in line with what I was expecting to see based on the observing reports I've read.

I'd love to know what magnifications are being using to see Neptune as being a disc? I am making a bold assumption that I correctly identified Neptune  Can any details or moons be seen with these planets? I'm assuming that they both require a lot more magnification than 180x to see much beyond the shape and colour?

[billyharris72]

I've never had much luck with Neptune either. 180x should do it - Neptune is currently around 2'3" across, so the magnified disk will be about 6 arcminutes across, so pretty tiny (1 arcmin is about the limit of human vision). Provided the conditions are very still, and the scope is well collimated and perfectly focused, you should just about be able to make it out as a disc. I've seen it look like a fuzzy pinpoint (with fuzzy pinpoints for stars) at x300 before, and am 99% sure I was bang on - I located it manually and then used goto, and both time was on the same object. I reckon the seeing conditions are absolutely critical for Neptune - despite not being all that much smaller I find it a lot harder to tease anything from than Uranus, which is relatively easy.

[Stu]

Congrats on seeing these two. From memory Neptune was quite obviously blue but still tiny. Uranus appeared more of a greyish green and a little larger though still small.

I think John has had success with these moons but with his 12" dob, not sure about the smaller fracs though their contrast may allow it too at high mags, probably x300 when conditions are good.

[Littleguy80]

51 minutes ago, billyharris72 said:

I've never had much luck with Neptune either. 180x should do it - Neptune is currently around 2'3" across, so the magnified disk will be about 6 arcminutes across, so pretty tiny (1 arcmin is about the limit of human vision). Provided the conditions are very still, and the scope is well collimated and perfectly focused, you should just about be able to make it out as a disc. I've seen it look like a fuzzy pinpoint (with fuzzy pinpoints for stars) at x300 before, and am 99% sure I was bang on - I located it manually and then used goto, and both time was on the same object. I reckon the seeing conditions are absolutely critical for Neptune - despite not being all that much smaller I find it a lot harder to tease anything from than Uranus, which is relatively easy.

Thanks Billy. It did come across as being a bit fuzzy at 180x, plus conditions where a bit windy last night. I think you're right about conditions needing to be spot on for a really good view. Will certainly go back for another look. Uranus being closer and brighter was a much more obvious disc.

[Littleguy80]

54 minutes ago, Stu said:

Congrats on seeing these two. From memory Neptune was quite obviously blue but still tiny. Uranus appeared more of a greyish green and a little larger though still small.

I think John has had success with these moons but with his 12" dob, not sure about the smaller fracs though their contrast may allow it too at high mags, probably x300 when conditions are good.

Thanks Stu. I'll have to go back and see if I can pick up any colour on Uranus. My impression was that is was white. I wasn't using any filter so might be worth trying the Neodymium to see if that brings the colour out at all. I spotted John's post after I posted this. Based on that, the moons are probably out of reach for my scope. I'll still look for them though, you never know if you get lucky with good conditions!

[John]

I've used 300x or more on these planets with my 12" dob and 130mm apo refractor. I've not seen any detail on their disks but I was not expecting to really. You get a more apparent disk (rather than a star-like point) and I have found it possible to spot Neptunes moon Triton and the Uranian moons Titanian and Oberon. The moons are pretty faint - sometimes only visible using averted vision.

I've found that the planets remain quite well defined disks at high powers. They are recognisable as planets rather than stars even at 100x though. Uranus and Neptune can be seen with a 50mm finder relatively easily but definitely just star-like in that !

I find both planets look pale blue to my eye, perhaps more blue-grey for Neptune ?

[Littleguy80]

2 minutes ago, John said:

I've used 300x or more on these planets with my 12" dob and 130mm apo refractor. I've not seen any detail on their disks but I was not expecting to really. You get a more apparent disk (rather than a star-like point) and I have found it possible to spot Neptunes moon Triton and the Uranian moons Titanian and Oberon. The moons are pretty faint - sometimes only visible using averted vision.

I've found that the planets remain quite well defined disks at high powers. They are recognisable as planets rather than stars even at 100x though. Uranus and Neptune can be seen with a 50mm finder relatively easily but definitely just star-like in that !

I find both planets look pale blue to my eye, perhaps more blue-grey for Neptune ?

Thanks John. I'm confident I had Neptune based on it's position in SkySafari and the colour difference compared to the white stars. I jumped right in with 180x magnification once I found it. Next step time I'll start closer to 100x and work up. I suspect, as Billy said, conditions have a greater impact with Neptune being further out. Will take some revisits to confirm. 

[John]

The odd thing is that I feel that Uranus and Neptune only look "star like" in a finder or binoculars. In a scope, even at 50x, somehow they just look different to stars. Their apparent disks are very small though - Neptunes is just 2.5 arc seconds in apparent diameter at the moment which is a touch less than the gap between the wider pair of Epsilon Lyrae, the "double double" in Lyra, to put it in perpective.

 

[Littleguy80]

19 minutes ago, John said:

The odd thing is that I feel that Uranus and Neptune only look "star like" in a finder or binoculars. In a scope, even at 50x, somehow they just look different to stars. Their apparent disks are very small though - Neptunes is just 2.5 arc seconds in apparent diameter at the moment which is a touch less than the gap between the wider pair of Epsilon Lyrae, the "double double" in Lyra, to put it in perpective.

 

It's probably a case of the "less is more" rule. 180x may have been too much for the conditions last night unless I simply got it wrong and wasn't looking at Neptune at all. I don't currently have a magnifying finder, I'm getting by with just the Telrad so I'm starting with 38x view

[Littleguy80]

Went back for more last night  Reversed the order and started with Uranus first. Tried a number of different magnifications and added the Neodymium filter at 150x. There seemed to be a slight green tinge with the filter. That went away when I removed the filter at the same magnification. So either the filter was adding the colour or allowing it to come through. I've never noticed any green when using the Neodymium on Jupiter or Saturn so there's a good chance it was coming from the planet. 

Working up the magnifications with Neptune and the pale blue colour was noticeable all the way through. At 113x (8mm BST), the appearance of Neptune started to look different to the stars. Best description is that it appeared more solid than the stars.  This was more noticeable still at 150x and I felt it could be described as a tiny disc. I tried 180x again and things became fuzzier like last night. Could be conditions or collimation affecting the view. Uranus still showed well at 180x though. 

Thanks for all your comments yesterday, they definitely led to a better view of these planets second time around  In fact, on a more general note, I find that regularly on SGL. Comments of observing reports nearly always lead to revisits and seeing something I missed the first time around  

[John]

Good stuff Neil !

I had a look a Neptune myself last night with the ED120 refractor. Your description is pretty good !. I used up to 300x but no sign of Triton - too faint for that scope last night I reckon.

I feel it starts to look like a tiny pale blue bead - it's probably an illusion but it does look like a ball rather than a flat disk if observe carefully ?. Perhaps it shows limb darkening which enhances this 3D effect ?

[Littleguy80]

1 hour ago, John said:

Good stuff Neil !

I had a look a Neptune myself last night with the ED120 refractor. Your description is pretty good !. I used up to 300x but no sign of Triton - too faint for that scope last night I reckon.

I feel it starts to look like a tiny pale blue bead - it's probably an illusion but it does look like a ball rather than a flat disk if observe carefully ?. Perhaps it shows limb darkening which enhances this 3D effect ?

Thanks John. Glad you had a look at Neptune too and I like your blue bead description. It's interesting that you say about a 3D effect because that did cross my mind but I put it down to my imagination. I'd not heard of the limb darkening before but have educated myself through Google  It makes perfect sense that it would give a 3D effect. I wonder whether the effect is more pronounced on these planets as their light is more concentrated giving a sharper gradient across the disk. 

[Dave In Vermont]

Using a 12" Meade LX200GPS, I bagged Uranus. It was a distinctive pale-green color - and un-mistakable from anything else. Next-up was Neptune - which as a color I thought at the time - still do - it was best described as being 'icy-blue' and quite a different color than I've seen before out there. I'd have no problem picking it out from any surrounding denizens in my FOV. I was using about 260X and the atmosphere was clear as the proverbial-bell.

People's color-sense is the last of our senses to develop. We all perceive colors differently. I came out-of-the-egg with a very sharp colour-sense. My dad taught courses on color and perception and uses thereof as a professor at MIT. He ran me through a very thick deck-of-cards comprising the entire range of colours from the Munsell Color-System. I was able to tell all of them apart, which was & is a rarity. I have a friend who sees a red stop-sign as yellow, and many other variations from one person to the next. No one is better than anyone else (in my view), just a fasinating difference from one person to the next. In Homer's Odyssey, the ocean is referred to as being 'burgundy-colored.'

Fascinating!

Dave

 

Munsell Color-System

 

[Littleguy80]

Fascinating stuff, Dave. I'm always amazed at the way we perceive colour differently purely based upon the colours that are next to it. I like to compare objects when observing. I find it easier to pick out the colour in, say, Neptune or the Blue Snowball Nebula by comparing them to surrounding white stars. 

[John]

When I'm doing outreach sessions I generally find those with younger eyes seem to pick up colour in astro objects more distinctly.

[Littleguy80]

7 hours ago, John said:

When I'm doing outreach sessions I generally find those with younger eyes seem to pick up colour in astro objects more distinctly.

Makes sense. I plan on getting my kids out more with the telescope when it gets dark a bit earlier. I'm 37 so I'm somewhere in the middle ?

[MarsG76]

300-330X shows a small but definite disc on Neptune, and like you saw, blueish in color...

Uranus is a bit bigger and the color was a mare pale than Neptune.

I did read a observation report where people have claimed to see one or two moons around Uranus and Neptune, I unfortunately cannot claim to have seen any moons... yet

[niallk]

I was lucky twice last year to catch 4 moons of Uranus on nights of very good seeing from a decent but not uber dark site - using 330x.  I found Triton showing much clearer than the moons around Uranus - a couple of them took patience and averted vision to detect - and confirm positions against Sky Safari.

My first ever night seeing Uranus - with my 10" - was plagued by not great seeing ... barely distinguished a disc, no moons. Seeing Uranus and Neptune as sharp discs in the 15" was a real thrill

It pays off to keep on trying and hopefully catch a magical night with good conditions with a cooled, well collimated scope!

[harrym]

I agree that 300x is a good magnification for seeing the discs and the moons. I've seen Titania, Oberon and Triton with the 12" Northumberland refractor (which only needs a 20mm eyepiece to give 300x!), but the difficulty varies from night to night, even when the naked eye limiting magnitude is similar: you want the atmosphere to behave well. Uranus appears greenish-blue and Neptune pale blue.

If you want to see Uranus's moons with an 8" scope, just wait till Uranus's perihelion in 2050 when it and all its moons will be 0.4 magnitudes brighter

[MarsG76]

42 minutes ago, harrym said:

I agree that 300x is a good magnification for seeing the discs and the moons. I've seen Titania, Oberon and Triton with the 12" Northumberland refractor (which only needs a 20mm eyepiece to give 300x!), but the difficulty varies from night to night, even when the naked eye limiting magnitude is similar: you want the atmosphere to behave well. Uranus appears greenish-blue and Neptune pale blue.

If you want to see Uranus's moons with an 8" scope, just wait till Uranus's perihelion in 2050 when it and all its moons will be 0.4 magnitudes brighter

Marked in my calendar... took days off work and waiting. ;-)

[Littleguy80]

5 hours ago, harrym said:

I agree that 300x is a good magnification for seeing the discs and the moons. I've seen Titania, Oberon and Triton with the 12" Northumberland refractor (which only needs a 20mm eyepiece to give 300x!), but the difficulty varies from night to night, even when the naked eye limiting magnitude is similar: you want the atmosphere to behave well. Uranus appears greenish-blue and Neptune pale blue.

If you want to see Uranus's moons with an 8" scope, just wait till Uranus's perihelion in 2050 when it and all its moons will be 0.4 magnitudes brighter

Sounds like I'm going to need to save up for an upgraded scope. Maybe I'll get some money at my retirement party in 2045

[Pondus]

7 hours ago, Littleguy80 said:

Sounds like I'm going to need to save up for an upgraded scope. Maybe I'll get some money at my retirement party in 2045

Nah. I`ll bet you`ve upgraded to minimum 10" long time before New years eve