Neptune with 10cm

[John]

I've been having a nice session pottering around some doubles and brighter DSO's with my Tak 100 refractor this evening.

Managed to get my 1st view of Neptune this year as well. It's currently near Lambda Aquarii and at magnitude 7.8. I could just pick it out in my 6x30 RACI finder. It's funny how it just looks different from a star even at just 100x and though it's tiny pale blue disk has an apparent diameter of just 2.5 arc seconds. Boosting the magnification to 200-250x showed a larger and nicely defined pale blue disk now very clearly not stellar in appearance. No sign of Neptunes brightest moon Triton with this scope - at 14th mag and fainter due to atmospheric extinction even Tak 10cm optics could not conjour it up for me. I'll have get the 12" dob out another time for that little fella !

I guess it must be an optical illusion but when I applied 250x magnification to the planet it seemed more like looking at a pale blue marble than a flat disk - maybe there is a little limb darkening there to create that affect ?

Nice to see this massively distant world again. I believe it's a bit over 4 billion km from Earth.

 

 

 

[Size9Hex]

Nice one John. It's fantastic to see Neptune out in the icy depths. Interesting comment about it looking different from a star. I've had this impression too (and also with Jupiter's moons) but never but my finger on exactly what it is that makes them look different.

[John]

6 hours ago, Size9Hex said:

Nice one John. It's fantastic to see Neptune out in the icy depths. Interesting comment about it looking different from a star. I've had this impression too (and also with Jupiter's moons) but never but my finger on exactly what it is that makes them look different.

Jupiters 4 largest moons definitely appear as disks through a decent scope at 150x or so. With some careful observing you can work out which is which by comparing their apparent sizes although two are closer in size than the others so it's possible to mix those up occasionally !

 

[Piero]

I was also observing Neptune the other night but with twice the aperture. No additional detail, but still interesting to see this distant planet using an amateur telescope. I hope to spot Ariel moon in Uranus in the future. Last night, a small Mars, a lovely Saturn and overlapped Jupiter-Venus just above the western horizon were also nice too see!  

[John]

13 minutes ago, Piero said:

I was also observing Neptune the other night but with twice the aperture. No additional detail, but still interesting to see this distant planet using an amateur telescope. I hope to spot Ariel moon in Uranus in the future. Last night, a small Mars, a lovely Saturn and overlapped Jupiter-Venus just above the western horizon were also nice too see!  

I've managed to spot Titania and Oberon with my 12" dob a while back. I needed a lot of magnification (300x or more) to spot them twinkling shyly at around 13th magnitude. I've not managed Ariel yet.

 

[Piero]

1 hour ago, John said:

I've managed to spot Titania and Oberon with my 12" dob a while back. I needed a lot of magnification (300x or more) to spot them twinkling shyly at around 13th magnitude. I've not managed Ariel yet.

Interesting! I didn't know Ariel was dimmer than Titania and Oberon. I've been interested in Ariel for a while because of Shakespeare actually!  

[Paul73]

Teasing out moons is a strangely enjoyable pastime. To me, it seems to bring the host planet to life.

Don't worry Piero. Mr Shakespear didn't miss out Oberon and Titania. They were King and Queen of the fairies in A Midsummer Night's Dream. 

Paul

 

[Size9Hex]

29 minutes ago, Paul73 said:

Teasing out moons is a strangely enjoyable pastime. To me, it seems to bring the host planet to life.

Nicely put. When I caught a few of Saturn's moons scattered seemingly randomly around the planet for the first time, and then saw them scattered randomly elsewhere a few days later, it came to life. Nice contrast to the predictable straight line order of Jupiter, although seeing moons emerge from Jupiter's disk (and especially from its shadow) while you watch really does bring it to life.

I quite enjoy asteroid bagging for a similar reason (usually while my eyes are adapting early in the session). Seems there's always some new lump of rock in reach on any given night, and makes you realise just how much stuff is swirling around out there!

[John]

7 hours ago, Piero said:

Interesting! I didn't know Ariel was dimmer than Titania and Oberon. I've been interested in Ariel for a while because of Shakespeare actually!  

It might not be dimmer, it must just have been awkwardly placed for observation when I tried to see it. With spotting the fainter planetary moons, elongation from the host planet is a factor as the further away it is, the easier it is to see as it's out of the planets glare. Low scatter optics help with this task as well.

[Piero]

10 hours ago, John said:

It might not be dimmer, it must just have been awkwardly placed for observation when I tried to see it. With spotting the fainter planetary moons, elongation from the host planet is a factor as the further away it is, the easier it is to see as it's out of the planets glare. Low scatter optics help with this task as well.

Yes, that's can be the case. Regarding their brightness Wikipedia reports Ariel's magnitude is greater: Titania: 13.9mag, Oberon: 14.1 mag, Ariel: 14.4 mag.

Of course they could reflect light differently depending on the rock type they're formed. This could make a difference in the detection too. A nice job for a well corrected 12" like yours!  

Can you see Neptune's moon Triton with you 12"? 

 

On 27/8/2016 at 01:23, John said:

I guess it must be an optical illusion but when I applied 250x magnification to the planet it seemed more like looking at a pale blue marble than a flat disk - maybe there is a little limb darkening there to create that affect ?

Almost forgot to mention. I also thought something similar when I observed Neptune at 180x with my 60mm. While a disk shape was more obvious for Uranus, this was not clear for Neptune. My feeling was I was seeing the increase in the diffraction disk rather than the actual disk of the planet. Said this, your 100mm resolves much better and your exit pupil of 0.27mm (?) was more moderate than 0.2mm I was using.   

Still amazing that we can see a so distant planet with these small telescopes nowadays!  

[John]

5 hours ago, Piero said:

.....Can you see Neptune's moon Triton with you 12"? 

 

Yes. It's a little easier than the Uranian moons that I mentioned earlier. High magnification is still needed though.

[John]

Quick update - I've been viewing Neptune with my 130mm TMB refractor this evening and managed to pick out Triton. I used 324x to get it and checked the moons position with Cartes du Ciel and Stellarium. At mag 13.5 (I believe) the pinpoint of light was tough to hold with direct vision but popped clearly into view more readilly (though I'd not say easily !) with a little averted vision.

 

[Special K]

Good spot John. This is a good time for Neptune for sure. Just need the seeing. I see you are inching your way up in aperture!  

Tak sounds like it's doing a pretty darn good job.  

[John]

1 hour ago, Special K said:

Good spot John. This is a good time for Neptune for sure. Just need the seeing. I see you are inching your way up in aperture!  

Tak sounds like it's doing a pretty darn good job.  

I'll get the 12" dob on it in due course but I have already seen Triton with that one. Pleased to see it with the 130mm aperture frac though. I can see why it was just out of reach in the Tak 100 the other night but maybe an exceptional night will come along so that I can see this tiny, distant world with that one as well

[Special K]

I've been intending to get the 6" achromatic on Neptune. I'll keep an eye out for those moons!

[andrew63]

Thanks for the reminder on Neptune John. The last time i saw it was a year or so ago when it was close to Venus. How does it look in a 8cm ?  At 90x it was tough to know it was a planet, but compared to a slightly brighter star in the same field, there was a kind a dullness to the image.  A huge gas giant is out there !

 

andrew 

[nightfisher]

To say i am a solar system person i have only ever had one quick glimpse at neptune and must give it another go as its quite well placed from my garden, will set the Mak up on the driven mount soon as i get a good clear night 

[John]

6 hours ago, nightfisher said:

To say i am a solar system person i have only ever had one quick glimpse at neptune and must give it another go as its quite well placed from my garden, will set the Mak up on the driven mount soon as i get a good clear night 

Well worth it Jules and not too difficult to find ATM. I can see it with my 6x30 RACI finders. Using averted vision (plenty of it !) I just managed to see Triton with my 130mm frac the other night. A tiny 13th mag spark around 10 arc seconds from Neptune but quite a thrill to see it with this relatively small aperture

[Special K]

The clouds have been rambling across the sky but I managed to pin down the location tonight and get a wobbly look at 257x. I'd been itching to see Neptune again since reading this thread!  Hopefully seeing improves for the next run. I couldn't see any points of light nearby so no moons to report. I was struggling to get decent focus.