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Y shaped formation on Venus.


mikeDnight

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In April's Astronomy Now magazine on page 17 there is a short, interesting article discussing the Y shaped formation in Venus cloud tops. The image on that page is taken in UV light by Pioneer Venus Orbiter.

As I was scouting through some old observations of Venus that I made a few years ago I came across these sketches.

post-41880-0-05042700-1427197296_thumb.jpost-41880-0-70763200-1427197366_thumb.j

Its interesting that by playing with filters, not designed for observations of Venus, the Y shaped feature in the cloud tops of Venus became more easily discerned. This may simply be that the filters reduced the glare, or may be there was some real advantage to using the filters in question (OIII & Hb).

I'm uncertain as to the real reason, just that there was a noticeable difference in the detail seen.

I'm posting this to encourage other observers to play around with filters and not to simply presume they are only any good for X, when they could be useful for X, Y & Z.

Mike

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beautiful drawings Mike. along the 'why not try it' angle, after recommendations by another SGLer,  I use my Lunt Solar wedge (with no filters inserted) for Venus and it really creates a lovely sharp disc/phase. I must try this with my 12" f4 newt as this has a lot of available in focus and might just focus with the wedge.

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  • 4 weeks later...

Thanks so much for posting this.  For 25 years I had observed Venus with my 10" reflector, pretty much just observing its phases.  Several years ago I started doing most of my planetary observing with a 90mm f10 refractor and I noticed that occasionally, when I was observing Venus, I would notice some very, very, I mean very subtle dark shadings.  I didn't take them seriously, I just thought they were some kind of optical effect akin to C.A..  But, after looking at your drawings, it dawned on me that the the dark shadings that your drawings show was exactly what I was seeing, albeit, as stated above, they were much more subtle for me.  Since then I have been observing Venus just as soon as I can pick it out of the evening sky with a variety of different colored planetary filters, and I am willing to go out on a limb and claim that I am, in fact, observing subtle features in the cloud tops of Venus!  For me, the green filter seems to bring these features out best.  Once again, thanks for your post.  I now know that there is more to see with Venus than just its phases.

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When you look at images of Venus taken by space probes you can often see a sort of V or wedge shaped pattern to the clouds, eg: in the Pioneer Venus Orbiter image from 1979 below. I guess it's feasible that keen eyed observers could tease out indications of this sort of structure. Playing around with filters does seem a good idea - nothing to loose anyway !  :smiley:

post-118-0-01924100-1429647140.jpg

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UV-filters have been used for imaging Venus for awile now. Schuler and Baader being the two varieties available. Which is better? Well here's some testing:

http://www.astrosurf.com/pellier/comparuvfilters

As for what the 'Y' feature may indicate? My guess would be that it's corrosponds to the topography of some surface features under the clouds. But that's just a guess. Venus, due to it's constant shroud of clouds, begs for exploration.Which explains why I laid out some serious money and got a Schuler.

Clear Skies - But Never on Venus,

Dave

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The classic Y-shaped markings were just visible to me at times last evening with my 80mm frac and a deep blue filter, or with a ND filter. Not visible in my Mak though at the same time.

I've seen the markings more clearly in the past when the seeing was better and when there was less haze (102mm f13 frac at x240).

Chris

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In the past I've sort of mentaly filtered out any markings that I think I might have seen on Venus in the (mistaken obviously) belief that seeing such detail was beyond my scopes / eyes. I'll need to do some Venus observing with a more open mind I can see :smiley:

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In the past I've sort of mentaly filtered out any markings that I think I might have seen on Venus in the (mistaken obviously) belief that seeing such detail was beyond my scopes / eyes. I'll need to do some Venus observing with a more open mind I can see :smiley:

The 120ED should be about perfect for Venus's markings John!

Chris

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I'm glad others are able to see these differences in albedo. They are certainly very subtle and it would be easy to doubt their existence. I often find it helps if I begin by looking for the brighter areas, such as the cusps and the limb. Also there can be brighter areas along the terminator. Once these have been illustrated by dashed lines on the initial rough sketch, it becomes easier to see the shaded areas.

I was browsing Cloudy Nights a few days ago when I noticed an image of Venus taken by an amateur at roughly the same time as I'd sketched the planet. Comparing my sketch with his superb image, I was thrilled to find almost identical corresponding features, except I'd used a diagonal, and so my sketch was mirror reversed.

Mike

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The 120ED should be about perfect for Venus's markings John!

Chris

Thanks Chris.

I've just been using the ED120 on Venus and it does present a very crisp and largely colour free image of the "hell planet". It's pretty gusty here though this evening and while I did seem to see uneveness in the surface contrast I'm not confident enought of what I was seeing to say that they were cloudtop features rather than artifacts of some other kind.

Maybe we will get a still evening while Venus is well presented.

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As a number of you use SW 120 ED apos I thought I'd post the following sketches, all made while using a SW 120 FPL53 fluorite apo a few years ago. A truly superb telescope, it inspired me to sketch Venus throughout the entire apparition. Below are just four observations from 2009 which may give us all something to look forward to as Venus turns to a thin crescent in the coming weeks.

Mike :-)post-41880-0-71751300-1430388079_thumb.jpost-41880-0-33429900-1430388129_thumb.jpost-41880-0-92722900-1430388158_thumb.jpost-41880-0-60740200-1430388192_thumb.j

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  • 2 weeks later...

Hi folks,

Ive done quite a lot of Venus imaging recently. Cloud features are very contrasty in UV but are also quite strong in Violet (ie use a Wratten 47). Having imaged Venus in the W47 and seen where the bright areas were (ie poles, as stated above) I found I could just detect them with the Wratten 47 by eye.

However, Ive also found that cloud features are detectable in G and R, though at very low contrast and only by image processing.  However, they are extremely variable over hours and days so you might get lucky with a high contrast patch!

Here's Venus on 17th/March in IR (807nm longpass) and Wratten 47 (the image with higher contrast).

post-32337-0-80810900-1431522297.pngpost-32337-0-67212300-1431522355.png

N

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Hi folks,

Ive done quite a lot of Venus imaging recently. Cloud features are very contrasty in UV but are also quite strong in Violet (ie use a Wratten 47). Having imaged Venus in the W47 and seen where the bright areas were (ie poles, as stated above) I found I could just detect them with the Wratten 47 by eye.

However, Ive also found that cloud features are detectable in G and R, though at very low contrast and only by image processing.  However, they are extremely variable over hours and days so you might get lucky with a high contrast patch!

Here's Venus on 17th/March in IR (807nm longpass) and Wratten 47 (the image with higher contrast).

attachicon.gif807 2015-03-17T17_32_00vdub_AS_p20_g4_ap4regi.pngattachicon.gifw47 2015-03-17T17_29_44_AS_p20_g4_ap4regi.png

N

Happylimpet, your images of Venus are amazing. Thanks for sharing them.

I hadn't drawn Venus on the date of your images but I had drawn it a few days before using an Equinox 80, and again only a few days ago using a FC 100. The sketches tend not to image well as they either appear to faint or to dark, but the shadings and bright areas on the sketches correspond remarkably well with your superb images, though obviously not as acurate.

Mike. :-)post-41880-0-92035500-1431543436_thumb.j

post-41880-0-76601700-1431543486_thumb.j

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  • 3 weeks later...

Hi MikeDnight I didnt see yr reply until now....your sketch certainly looks typical of the sort of markings I would expect.  Dont forget that Venus' cloud tops rotate in only 4 days, so images even an hour apart show clear movement and images/sketches a day apart cant really be compared. But the structures you see look good.  If you can put up a list of dates you made sketches I can see if I have images from then.... would make an interesting cmparison!

Cheers

Nick

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Hi MikeDnight I didnt see yr reply until now....your sketch certainly looks typical of the sort of markings I would expect.  Dont forget that Venus' cloud tops rotate in only 4 days, so images even an hour apart show clear movement and images/sketches a day apart cant really be compared. But the structures you see look good.  If you can put up a list of dates you made sketches I can see if I have images from then.... would make an interesting cmparison!

Cheers

Nick

Hi Nick.

Here are my observations for this apperition including dates and times (UT).

5/4/15 @ 18.53

7/4/15 @ 19.04

17/4/15 @ 17.11

18/4/15 @ 18.09

20/4/15 @ 19.48

22/4/15 @ 18.00

7/5/15 @ 21.20

9/5/15 @ 21.13

11/5/15 @ 20.30

16/5/15 @ 20.16

23/5/15 @ 19.35

29/5/15 @ 20.55

31/5/15 @ 21.25

It would be interesting to see if there are any similarities between the sketches and your images. The only thing to remember when comparing, is that I now often use a diagonal and turn it to any old angle for comfort. It confuses me sometimes as to the correct orientation.

Thanks,

Mike

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Thats a good list of observations! As we're both in the UK chances are we took advantage of the same periods of clear skies so good chance there's a date in common.  WIll try to remember to look this eve.  I think I observed on the 29/5.

Cheers

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Hiya these are the images I have on dates you listed. Not my best! Some very quick processes too....bit of a backlog. Also I cant guarantee not mirror image - but pretty confident. Bit suspicious of 9/5, but not much visible then anyway.

Cheers

Nick

7th April: Wratten 47, 807nm longpass

post-32337-0-10067900-1433442096.pngpost-32337-0-88494400-1433442096.png

22/4 UV, and 807nm (worse seeing)

post-32337-0-98801700-1433442245.pngpost-32337-0-73633900-1433442307.png

9/5, just one rubbish 807

post-32337-0-96985100-1433442427.png

29/5: 807nm,  UV

post-32337-0-16003500-1433442487.pngpost-32337-0-40660900-1433443561.png

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I imagine youve realised that these wil be mirrored relative to yours (possibly excep[ting 9/5) as you use a diagonal...also note that clouds appear different in IR and UV. Not sure which Id expect to be closer to visual!

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  • 1 month later...

I will certainly dig out the sketches for comparison and will post them on this thread. It might be a few days away though, I've got man flu. (A real nasty one too)

Many thanks

Mike

Hi Mike! Hows the flu? Lets see those sketches!!!

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