Saturn, Rhea transit 14th April

[chrisrnuttall]

Here is a sketch of saturn from the evening of the 14th April.

I have tried to see Dione in shadow transit before but failed to see even a hint of it, i gave it up as impossible since it is only 0.19", then i saw Paul Abels sketch of that very event also using an eight inch newtonian and decided to try again sometime since it must be possible.

I recently read in AN that rhea (which is 0.25") was going to shadow transit twice this month at reasonable times and that it and Titan were the only transits considered to be 'viable' for visual observers. So I got myself outside with a cooled and aligned scope when Rhea was at mid transit, it took half an hour of continuous observing to detect a definate glimpse of it but the seeing was improving all the time and once i had my eye in i got a few more very brief imressions that there was a grey blurry pinpoint on the disc of Saturn.

After a few of these 'sightings' i finally got a definate view of the shadow when one time the soft grey point resolved slightly further into a dark grey tiny dot. Great!

I tried a bit more and decided to go in for a nice cup of tea!

I came back out in time to see Rhea - tiny, dim and grey - emerge from its transit of Saturns disc, by now the seeing was a little better still and i was able to get two more good views of the shadow, having Rhea as a marker slightly helped me focus my attention on the exact spot where the shadow would be.

by the time i finished my eyes felt like this

This was an extremely difficult observation and after my failed efforts to see Dione i think i have been quite lucky with the still conditions of late giving great seeing despite the low altitude of the planet. It is definately one i will remember!

And after seeing me doing my sketch, my 6 year old son now wants to see Saturn too!

Chris

[chrisrnuttall]

just noticed that i have written 14th of march on my sketch, oops!

[Astorix]

A really lovely sketch! you must be well chuffed!

[dweller25]

Excellent observation and drawing.

[Doc]

That is an extremely hard observation, as you say titan is not to bad when the seeing is good , but it's other moons very hard. And of course backed up by a brilliant sketch.

[DarkerSky]

That is awesome Chris!! A really special observation and sketch. There can't be that many people around the world who can claim to have seen a Saturnian moon transit.

For me that is one of the most outstanding Saturn images I have seen so far this year. It has a special value all its own.

Very well done

[russ]

Superb drawing Chris and well done for perservering. Just shows how important it is to spend a prolonged period at the eyepiece for planetary observing.

I've not yet seen a shadow tranist on Saturn but hoping tonight will change that as Rhea is in transit again from 21.30.

[chrisrnuttall]

Russ

Yes it is transiting again tonight, not sure if there will be any more next month but at some point this year we will have the last one for a long time, so definately worth a go!

You will need good seeing to detect it, the seeing on my ob was good but not perfect and i struggled to confirm to myself that i had actually seen it for about half an hour. Most of the time there was not a trace of the shaddow at all, then sometimes i would detect a very pale grey cloudy area which seemed to come and go and i wondered if it was just my eyes playing tricks on me.

I started to think i was having myself on but then that pale grey whisp tightened up into a tiny little dot just for a second and i knew what i had seen was real. I noted the position and went inside to compare it to the view on starry night and it was in exactly the right place.

I carried on observing saturn, concentrating on the right area, and the indistinct fuzz i had seen earlier kept returning but somehow it seemed slightly tighter now, the seeing was getting better and i had seen it once so i knew what to look for, over the next twenty minutes or so i had a couple more definate glimpses of the shaddow, and then again once Rhea had left the disc, which is what i drew.

Good luck, i really hope you get to see it too it's nice to share it with someone, it's the kind of silly insignificant little dot only an astronomer would apreciate, especially when the best you can hope for is to glimpse it for a second at a time!

[DarkerSky]

Russ / Chris - I'm going for this tonight too. So it starts at 21.30 UT or BST?

[russ]

Chris, i've really built myself up for a difficult task. I just hope the seeing at 9.30 is better than last night. I couldn't get a steady view above 100x last night. Eventually it improved but that was by midnight. Will try my best and report back.

Seb, i'm not sure if the 9.30 is mid transit or transit starting. I can't find anymore info.

[chrisrnuttall]

just looking at starry night for you, hang on....

[chrisrnuttall]

ok

according to starry night (which was sopt on with my observations last week)

Rhea's shadow enters saturn's disc at 20:50 BST

mid shaddow transit is at about 22:20 BST

Rhea leaves Saturn's Disc at about 23:20 BST

The shaddow of Rhea leaves satrun's disc at about 23:50 BST

so saturn will be at its highest by the time it ends

which scope are you going to use Seb? I reckon a bigger aperture should help.

[chrisrnuttall]

jet stream looks calm for it;

Unisys Weather: 4 Panel (1-2day) GFS 300 mb Plot for Europe

and you lot down south look to have clear skies for it too if the bbc/weather is right.

have fun!!

[chrisrnuttall]

here are a couple of images from Starry night

22:20 bst

23:20 bst

[dobserver]

Wow your hard work really paid off, and thanks for an interesting report and great sketch. Very inspiring.....

[russ]

Hi Chris,

Well i was out from 20.30 - 23.30, desperate to see the shadow. But sadly the Metoffice/BBC forecast was way off and Metcheck (shock horror) got it right. Loads of high cloud, which isn't always a bad thing but it is when the seeing is also shockingly bad. I got some fleeting sharp views of Saturn but they were just that....fleeting as in no more than a second. It was impossible to get my eye in, really needed some more settled moments. Ho hum, that's all part'n'parcel of the hobby i suppose.

Hope some others had more luck.

[DarkerSky]

Hi Guys - I went with the 16" LB last night. Work commitments meant I wasnt able to get out until 22.00 BST. By the time the scope had cooled sufficiently I was hoping to catch the back end of the transit. Sadly, it wasnt to be. Plenty of high cloud and fairly rough seeing didn't help. Sounds similar to your seeing Russ. Was at x295 magnication. Could make out the equatorial bands and polar areas in brief moments, but it just wasnt steady enough for long enough for me to get a visual on the shadow.

Any luck for you Chris?

[chrisrnuttall]

completely cloudy here, I stayed inside and watched the Tele!

Tethys and Dione are both going to produce shaddow transits at the same time tonight, they are both a little smaller than Rhea (about 70% the diameter), and therefore that bit harder!

Tethys is from 22:20-01:05, and Dione from 22:40 - 01:40.

I have tried and failed with Dione before but i might have a go if i am not too knackered later

I reckon the next Rhea Shaddow transit is May 2nd-3rd, 21:45 - 00:45

Then there is a double shaddow transit of Rhea and Tethys on May 11th-12th

Tethys 22:10-01:00

Rhea 22:50-01:40

Enceladus' shaddow will also be there making a tripple but it is academic as it will definately be too small to see.

Actually these events will continue right through summer, I think i might have a go at one of the doubles, that would look great!

[DarkerSky]

Thanks for the heads up on all of that Chris. Making a note of all of those dates. Definately going to have a crack at these. Where are you getting the dates and timing details from?

[russ]

I was too knackered last night to do anything. But have made a note of those other dates...thanks Chris.

DS, be interesting to see how you get on with the 16" LB. You probably have a better chance than i do.

[chrisrnuttall]

i set the time on starry night pro to midnight, magnified saturn, and then advanced the date by one day at a time and watched the positions of the moons. If Rhea dione or tethys looked like transiting, then i revered and forwarded the time using the hour field, and then the minutes to get rough start and finish times for each event. Rhea seems to transit at midnight-ish every nine days currently.

Not sure about tethys or dione, but it shouldn't be too hard to work out, I havent bothered as i am not sure just how possible they are to observe, astronomy now didn't class anything smaller than Rhea as a 'viable target'. But i have seen Paul Abel draw a Dione shadow transit.

[Gill Rockwell]

beautiful sketch, Chris.

wonderful how you were able to get that amount of depth in there.

i'm just new to this but looking at the size of this i imagin this is impossible to catch on a photograph form earth.

correct or not, i don't think i ever had that thought before .)