Neptune and Triton

[John]

I was testing out my upgraded focuser on my 12" dobsonian this evening and one of the targets I used was Neptune which is currently in Aquarius.

It was in the same high power field of view as a 6th magnitude star tonight and they made a nice close pair in my 50mm finder with Neptune being the fainter of the two at magnitude 7.8.

Neptune's planetary nature becomes obvious at around 150x and you can see that it is a disk rather than a point source. Neptune's disk is currently 2.5 arc seconds in apparent diameter. At lower powers it resembles a pale blue star. I was able to observe the planet at 318x, 454x and 530x and the definition of the planetary disk remained quite clear, despite the rather average overall seeing conditions.

Using averted vision at the higher of these magnifications, the tiny speck of light that is Neptune's moon, Triton, was clearly seen. It was very hard to hold with direct vision tonight though. Triton moves around Neptune quite rapidly and it's position changes markedly night to night. It's around 8-10 arc seconds from Neptune's disk and has a retrograde orbit, ie: it moves in the opposite direction to the rotation of Neptune. Triton's magnitude is around 13.5 so challenging given it's relatively low altitude (which dims things further) and the seeing conditions.

Triton is, so far, the most distant rocky world I've been able to see. It's diameter is 2,700 km and I believe it's currently around  2.8 billion km from the Earth. It's one of those "just a faint point of light but really quite interesting when you know a bit about what you are looking at" objects 

[steppenwolf]

That's quite some view, John!

[Owmuchonomy]

Excellent. I found the Neptune/star pairing last night valuable because it helped me see the definite blue colour of the planet. I did not catch Triton though. It's low for me. I used my 9.25" SCT and found the clearest view in the conditions was with my 2" 24mm EP.

[laudropb]

Very nice report. I must have a look for myself if the clouds ever clear here. Thanks for posting.

[triton1]

Nice report John that,s one planet I haven,t found yet.

[John]

Nice report John that,s one planet I haven,t found yet.

Given your username John, you had better get on the case !

[triton1]

It is abit embarrassing but your right I shall have to pull my finger out.

[John]

It is abit embarrassing but your right I shall have to pull my finger out.

I was pulling your leg of course !

Neptune is quite well placed to find at the moment in Aquarius, it's between Lambda and Sigma Aqr.

[Moonshane]

I have never managed Triton yet. Must try soon. Great report.