Jupiter and twilight: prolonging the experience

[John]

Over the past few nights I've had some great views of Jupiter. The periods of best viewing however have often come when I've caught the giant planet with plenty of light still in the sky. The contrast of the features on the planet and the vibrancy of their colours seem to be really enhanced by that pale background sky.

As it's got darker I've still enjoyed the views but I've had to work harder (or so it seemed) to tease out the finer details, festoons, pale swirls and eddies etc, in the jovian atmosphere and the colours seem more muted.

I've found myself wondering if you could actually simulate twilight observing conditions by deliberately illuminating the background sky in some way, even once it's dark

I realise that this is precisely the opposite that we look for when observing other objects such as DSO's, where the blacker the background sky, the better, but for planetary observation I do find the slightly illuminated sky really helps

I guess I could move to Scotland or even further north  for the Summer months !

 

 

 

[David Levi]

I don't think that I'm going to experience that, as my neighbour's insecurity light comes on at twilight and goes off when it gets dark. The GRS is just disappearing at the moment.

[John]

8 minutes ago, David Levi said:

I don't think that I'm going to experience that, as my neighbour's insecurity light comes on at twilight and goes off when it gets dark. The GRS is just disappearing at the moment.

You might find that Jupiter can be observed pretty well despite the light. For seeing detail and contrast on the planets you don't necessarily need darkness. I think thats the point I was making

[Pondus]

A very interesting topic. I should imagine 'daytime' pupils is best for picking up planetary details? Planets themselves arent Bright enough through a telescope to ruin nightvision.

Some recommend looking at a streetlight before observing Jupiter, but we rarely do that, because we want to observe dso`s aswell during the same session.

I fully agree ; Jupiter With a blueish background seems like a good match.

[David Levi]

If it's not ruining my vision, and I'm not convinced that it isn't then it's certainly annoying. I know, I could chuck a blanket over my head and the eyepiece. Callisto and Io are in a nice configuration, one above the other, at the moment.

[Floater]

29 minutes ago, John said:

I guess I could move to Scotland or even further north  for the Summer months !

A 'gentleman' astronomer of days gone by might have described it as taking up residence for 'the season'. ?

[Pondus]

Kind of same topic was discussed in this recent thread :

https://stargazerslounge.com/topic/285256-observing-jupiter-in-twilightdaylight/

 

 

[John]

I've read that experienced planetary observers illuminate a white sheet of paper with a torch and look at it for a few minutes now and then during observing sessions.

I've tried filters (many different types) lots of times but I've found that you loose some of the finer detail with them although the principle features can have their contrast increased.

[David Levi]

I'm surprised. The neighbour's light has gone off, it's got darker (in general) and it seems to me that I am seeing better detail. Slightly more detail in the northern polar and tropical regions which seem to be quite faint anyway. Excellent seeing in Cardiff at the moment I would say. Viewing at 200x magnification with no problem. Some dark patches passing in the southern equatorial belt that I haven't noticed before in my limited experience of Jupiter which basically is this year.

[John]

The seeing is pretty good tonight. Now the Great Red Spot has moved off the visible disk, I've been following 4 large pale patches / spots in the South Equatorial Belt and a couple of nice dark festoons coming across the Equatorial Zone from the North Equatorial Belt. Hints of some white ovals in the South Temperate Belt.

Maybe my eyes have adjusted to the darker sky now

[Piero]

I was also observing Jupiter earlier this evening. The brighter sky helped reveal quite a lot of details. Overall the was more contrast and the colours were more saturated. The GRS was easier too.

[John]

53 minutes ago, Piero said:

I was also observing Jupiter earlier this evening. The brighter sky helped reveal quite a lot of details. Overall the was more contrast and the colours were more saturated. The GRS was easier too.

Thats what I found

[Paul73]

I'll have to give it a whirl. If I am doing a Jupiter session you'll see me flicking my phone on and staring at the screen for a moment every now and again, just to try and stimulate the colour receptors in the center of the eye. Night vision and averted vision are more of a hindrance than a help for this one.

It's just great to be getting out there. Even visited a few easy doubles this evening.

Paul

PS. I think that, on balance, I would head south for the "season". Propper dark and warm days.???

[kerrylewis]

Yes - one of the advantages of planetary observing (the bright ones at least) is that you can get started early. I had the Dob set up last night with my new 10mm Ethos and was rewarded with some cracking views of Jupiter- best for a while. The GRS was good until it departed. Unlike others I found it a bit pale in the twilight. Then lots of white areas in the SEB and a dark area in each EB. I tried a couple of filters but they didn't really improve things. I also had a quick go with a 2x Barlow for a really big disc which was great in moments of good seeing. A good session

I agree with the comments about dark adaptation and viewing Jupiter. I find that it helps to relax away from the eyepiece now and then and look at any light source (plenty around here!) . At the recent star party in the Peak District I was close to some other observers who were looking at DSOs while I was observing Jupiter. When I called them over to look at the planet they could hardly see a thing because it was far too bright! 

[chiltonstar]

I wonder, does lowering your dark adaptation by staring at a sheet of paper, or having a brighter sky, have the same effect as using a ND filter (or light cloud/haze) to reduce the brightness of Jupiter a bit?

Chris

[timwetherell]

11 hours ago, Pondus said:

A very interesting topic. I should imagine 'daytime' pupils is best for picking up planetary details?

Interesting point! Yes perhaps - especially if one has slightly wonky eyes, stopping them down may help?

[laudropb]

Very interesting post John. Thinking back to earlier in the week I noticed that when viewing the Moon then going on to Jupiter that I was seeing more of the finer detail .I must have subconsciously realised this because I kept going back and forwards between the two to get the best views of the planet.

[timwetherell]

11 hours ago, John said:

I've tried filters (many different types) lots of times but I've found that you loose some of the finer detail with them although the principle features can have their contrast increased.

That's been my experience with filters too. Although when the planet is very low and atmospheric dispersion is a problem, popping in a narrow band OIII or UHC can be very helpful. I've found that great when looking at Mercury a couple of degrees above the horizon

[John]

51 minutes ago, chiltonstar said:

I wonder, does lowering your dark adaptation by staring at a sheet of paper, or having a brighter sky, have the same effect as using a ND filter (or light cloud/haze) to reduce the brightness of Jupiter a bit?

Chris

I don't know the answer to that Chris.

I tried some filters on Jupiter last night, once the sky was dark. The ones I had to hand were a moon filter (don't know the %), a single polariser, a UHC (DGM NBP) and O-III (Lumicon) and I even tried an H-Beta (Astronomik).

While a number of the above increased the contrast between the primary equatorial belts and the paler surface, they also tended to make it more difficult to discern finer and more subtle fetures such as festoons, white ovals etc. I've found similar results in the past when I've used filters on the planets, including the Tele Vue Planetary Filter.

Last night I was mulling over whether there was any way to produce a lighter background sky in the field of view . Can't think of one offhand but I'd be interested in ideas

Incidentally, I was using my 130mm triplet refractor last night.

 

[John]

53 minutes ago, timwetherell said:

Interesting point! Yes perhaps - especially if one has slightly wonky eyes, stopping them down may help?

Not sure if I have wonky eyes or not. What do you think ?

 

[chiltonstar]

I certainly find that blue is good for Venus markings, and pale green/blue good for Mars, but I've never been convinced about coloured filters for Jupiter - maybe because the filters I have are not fully coated and produce visible reflections and some image degradation due to the quality. Maybe better filters would help more?

I have a Baader Nd filter, and again I am not convinced of its benefit....

Chris

[John]

The Tele Vue Planetary 1.25" cost me £85 I seem to recall so probably good quality. Didn't like the "bubble gum" pink tint though

 

[niallk]

Interesting comments about greater contrast in daylight!  I will try it when I get a chance

I don't know if this is somehow related, but 2 weeks ago I was startled by the views I had of Io as it transitioned across Jupiter's limb. It looked to me like a well defined 'ball'.  Against the blackness of space (eg 1/2 hr later), it was a fuzzy little bright 'star'.  But against the limb, it was just amazing: I saw it as a resolved body. I was using my 15" dob - I don't know if I'm overloaded with light and contrast is diminished when observing the moons against the backdrop of space.

Anyone find a similar effect? Do the moons look clearly as defined discs to you normally, or more a bit like bright stars if truth be told?  One reads of people able to visually discern albedo details on Ganymede... I would never have figured that feasible with my scope/my eyes, but Io that night was breathtaking ...

[Piero]

@niallk I will give a go at Jupiter Moons at 500x in June with my dobson + Vixen HR, if the seeing is good (and generally is).  

So far, I have only seen them as `bright stars`, but I never used more than 300x. 

Said this, I often recognise Ganymede from the other 3 with my 60mm + HR 2.4mm (150x). Of course it is not a disc! It is just slightly bigger. 

[Stu]

I generally would not say I see the moons as discs when against the sky background, but certainly do when they are over the limb of Jupiter. They are similar size to the shadows which have definite size to them.

I can well imagine that albedo effects may be visible from some of the high altitude dry desert locations where people observe at x500 plus!!