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Venus Crescent Phase

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#1 chrisrnuttall

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Posted 12 April 2020 - 10:52 AM

Hi everyone

 

With Venus now past dichotomy and entering the crescent phase of the current apparition, I'll be observing in daylight from now on as I have houses to the west, so have no possibility to observe Venus much after sunset. One good thing about being home every day is that at least I can be there in the day to make these observations. You've got to keep busy!

 

Last week we had some nice sunny days here in York, so I made several observations of Venus experimenting with the best time of day and the best filters to get a really good sharp view. I hope to keep on observing and adding to this post as time goes on.

 

6th April

15:30ut with Venus directly due south. 

Altitude 60.5°, Dia 27.3", Ph44%, CM1 243°, CM2 143°.

Seeing Ant III. Extremely variable due to very warm sunshine with the sun high in the sky, gusty wind. Still several hours before sunset.

 

W47 Violet Filter: No good in the bright blue sky

Integrated Light: Venus has a distinctly cream hue. Cusps are bright, especially the North. Terminator shading appears to extend towards the limb more notably at the equator forming a triangular shape.

W25 Red: This filter gave me a much more steady view and the markings on the disc are confirmed using this filter.

 

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#2 chrisrnuttall

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Posted 12 April 2020 - 11:00 AM

7th April

13:40ut with Venus due south-east.

Altitude 56.5°, Dia 27.7", Ph43%, CM1 246°, CM2 226°.

Seeing Ant III. Extremely variable again, the sun even higher in the sky than the previous attempt. 

The sky was incredibly transparent today and with some effort to locate the planet I could see Venus with the naked eye right in the middle of the day. 

 

Baader Neodymium Filter: Darkens the bright blue sky and increases contrast on the disc nicely compared with the view in Integrated Light.

W25 Red: basically the same details visible as with the Neodymium, however the view is more stable and the markings on the disc are confirmed using this filter.

 

Very similar in appearance to the previous day except that could make out a little more faint banding running from the terminator towards the limb, converging with one another as they go.

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#3 chrisrnuttall

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Posted 12 April 2020 - 11:18 AM

8th April 17:30ut.

Venus due south-west.

Conditions during the day were not very favourable today with high thin cloud dominating for most of the afternoon, however as the day wore on the clouds disappeared leaving the sky clear although a little 'milky'.

 

Altitude (only!) 49°, Dia 28.1", Ph43%, CM1 248°, CM2 324°.

Seeing Ant II-I. Extremely good!

Not a breath of wind, very calm and still.

One hour before sunset, but with the sun well down behind the houses and not shining on me or my telescope.

 

Baader Neodymium Filter:

Very steady view with good contrast.

Both cusps bright, North more than the South.

Both cusps were fine and razor sharp and hooked, like a pair of brilliant white needles.

Northern cusp collar crisp and sharply defined, becoming more diffuse as it heads across the disc.

Southern collar much more diffuse.

 

W25 Red:

Again a very steady view, very similar details to the Neodymium

 

1000 Oaks LP2 Filter (this is a narrow band pass green filter).

Excellent view. Again very similar details to the Neodymium, BUT, the view was so good, and so steady, that after a few minutes I started to make out extremely fine whisps of subtle detail crossing the disc. These fine filamentous lines converged gently as they crossed the disc from the dusky terminator towards the bright limb, giving Venus a properly 3D appearance.

My sketch really doesn't capture just how smooth and fine and delicate these markings really are, I think I would need to work at a larger scale and maybe in a differnt medium to do it justice.

 

I think this might have been the best view I have even had of Venus in 20 years of observing.

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#4 AndyFarr

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Posted 12 April 2020 - 12:06 PM

Hi Chris,

I'm impressed with the sketches. I've never had chance to observe Venus in daylight due to work. The hospital where I work has altered  my shift patterns, so I now get some time off during the day for the next few months. Is there a "best" time during the day to observe Venus, or is it a case of catching it when it is as high as possible? If I leave it until twilight  I'm looking over a housing estate to my west, so there is a lot of turbulent air and its difficult to get a decent image.





#5 chrisrnuttall

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Posted 12 April 2020 - 12:50 PM

Hi Andy,

 

Honestly I think the best thing you can do is get out and observe as much as you can; if you can have your telescope set up within easy access then just go and have a quick look to see what the conditions are like. you can always come back to what you were doing and try again another time.

Some people say the best seeing is around sunrise and sunset, which has to do with the sun's heat causing turbulence in the atmosphere as it shines down on us, also the land warming through the day and causing convection currents as it gives its heat back up to the air above it. This is lessened by observing when the sun is very low in the sky.

Certainly last week i found that by observing in the warmth of the day when Venus was at its highest i was at a disadvantage due to poor seeing. Whereas just before sunset on the 8th I has excellent conditions even though Venus was 10 degrees lower. 

This is not always the case though as there are many more variables at play......

 

Venus in the day can be hard to find, but with setting circles, or goto etc it is easier. You are also not dazzled by its brightness against the daytime sky like you are in the evening where filters are essential.

 

In short, it's a bit random, but the more times you have a try the better your odds are of striking lucky.


Edited by chrisrnuttall, 12 April 2020 - 12:54 PM.


#6 niteskystargazer

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Posted 12 April 2020 - 04:07 PM

Chris,

 

Very good sketches of Venus Crescent Phase smile.gif .

 

CS,KLU,

 

thanx.gif ,

 

Tom



#7 chrisrnuttall

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Posted 29 April 2020 - 07:41 AM

The weather isn't quite so good at the moment, however I got a decent view of Venus on the 24th.

 

I thought to try during the afternoon when Venus would be riding very high in the sky, 63° at 1500ut, but hot sunshine and cold wind made for particularly poor seeing conditions then, and throughout the afternoon, until the sun eventually began to set and the sky calmed down. So at 1900ut I made this sketch, with the seeing having improved to Ant II despite the altitude now being only 37°.

 

Orion OD 300, Binoviewers, ADC, Apodizer, 12.5mm plossls x333.

Observed in Integrated Light, and LP2 'green' filter.

Dia 35", Ph 30%, CM1 284° CM2 272°

Ant II

 

 

 

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#8 chrisrnuttall

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Posted 20 May 2020 - 09:50 AM

Hello again.

 

After a lot of fine weather recently I am finally getting round to posting a few more Venus observations.

 

With the phase shrinking I am seeing fewer and fewer markings on the disc; banding in the cloud tops melted away soon after dichotomy, and the darker cusp bands have also now disappeared, leaving only the terminator shading and limb brightening to differentiate from the pale cloud tops.

 

Throughout the apparition I have found that the seeing is all over the place during the day when the sine is shining on my garden, but if I wait until the sun moves behind the house then the turbulence calms down.

 

As ever, filters are essential with Venus, W47 violet is great when there isn't a lot of sunlight in the sky, but no good when the sky is very bright. 

Through experimentation I have discovered that nebula filters seem to be excellent on Venus. I have tried a broad light pollution filter, and anarrwer OIII filter, both to good effect. Their narrow pass-band centred in the green part of the visible spectrum seems to show good contrast on the disc, whilst conveniently producing an image which is free from glare, but also not too dim in my 300mm scope. 

 

I've also been experimenting with using a few different types of paper because I didn't like how grainy the drawings were looking earlier on. I'm using normal cartridge paper now.

 

Only a few more days of this apparition left, I will try to get a couple of very thin crescent observations if possible.


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#9 chrisrnuttall

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Posted 20 May 2020 - 09:53 AM

4th May

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#10 chrisrnuttall

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Posted 20 May 2020 - 09:53 AM

6th May

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#11 chrisrnuttall

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Posted 20 May 2020 - 09:54 AM

11th May

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#12 chrisrnuttall

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Posted 20 May 2020 - 09:54 AM

15th May

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#13 frank5817

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Posted 20 May 2020 - 10:53 AM

Chris,

 

Nice post of these Venus sketches. The crescent continues to get thinner and is easily seen for now in the daytime as long as you can fully block the sun by positioning you scope properly.

 

Frank :)



#14 niteskystargazer

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Posted 20 May 2020 - 01:09 PM

Chris,

 

Nice sketches of Venus smile.gif .

 

CS,KLU,

 

thanx.gif ,

 

Tom



#15 chrisrnuttall

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Posted 25 May 2020 - 08:19 AM

Monday 25th, and the weather is lovely again here, hot and sunny!

The past few days however have seen strong wind and a lot of cloud cover which has hampered observing. 

 

On Friday 22nd the clouds cleared by the evening allowing me a late view of the Mercury-Venus conjunction.

By the time was I able to see the pairing, they had already moved behind the roof of my house as seen from my 300mm Newtonian in it's shed, so I grabbed my Skywatcher 127mm Maksutov and found a patch of lawn where I could view the two planets through the gap between my roof and the next door house.

 

It was still a bit windy, and the altitude of the planets was by now getting quite low, so I didn't have good enough seeing to push the magnification for a detailed observation of either planet. 

The separation of the pairing was a little too wide to fit into the field of view of any of my eyepieces (being a planetary observer I don't have anything 'wide field' except for binoculars),

 

Nonetheless, panning from one planet to the other provided a very pretty sight, Venus showing an obvious thin crescent, and mercury looking just about non-stellar at 60x with a 1° field of view.

 

Skywatcher 127mm Maksutov. 25mm Celestron Xcel = 60x, 1°fov

Venus Az 288°, Alt 18°

Venus Dia 54", Phase 5%

Mercury Dia 6", Phase 67%

Seeing Ant IV

Attached Thumbnails

  • Venus and Mercury Conjunction 2020-05-22_2000ut.jpg

Edited by chrisrnuttall, 25 May 2020 - 08:22 AM.

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#16 chrisrnuttall

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Posted 25 May 2020 - 08:32 AM

Yesterday was again windy and cloudy, clearing later on.

This observation of Venus was plucked from the sky just before the planet disappeared behind the rooftops.

 

The sky was milky in the vicinity of Venus and extremely bright.

I have a Wixey digital angle gauge permanently fixed to the tube of the 300mm which is calibrated to within 0.1°, and a setting circle for azimuth which is generally within a degree or two, even so locating the planet in my 50mm finder was very difficult as it presented an extremely thin curved slither of light against the bright sky.

 

Again the seeing wasn't great, Ant III this time, however the disc of Venus is really large now so high magnification isn't a priority.

 

The limb brightening appeared to be concentrated towards the equator, fading off the further round the limb you look.

It was so bright at the equator that it reminded me of the footage you see of the sun rising over the earth's limb from the ISS.

I've tried to show that effect in the image.

The cusps were thin and comparatively dim, but I suspect that they extended past 180°, maybe as par as 190°.

 

Orion OD 300. Binoviewer. ADC. Apodizer. 15mm Meade Japan Superplossls = x277.

Az 273°, Alt 29°, Dia 55", Ph 3.6%, CM1 311°, CM2 323°

Seeing Ant III.

Integrated light (per sketch)

Thousand Oak LP2 Green nebula filter, and W25 Red filters also used.

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#17 Quinnipiac Monster

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Posted 26 May 2020 - 10:04 PM

Amazing, I love you drawings.



#18 John Gauvreau

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Posted 26 May 2020 - 10:23 PM

Chris, it has been wonderful spending the last month and a half seeing Venus through your drawings.  Thank you for taking us on this trip with you.  Your drawings are lovely.



#19 chrisrnuttall

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Posted 27 May 2020 - 03:04 PM

What a nice comment John, thank you, I had been wondering if this thread had become a bit 'old' and not so many folks were looking at it any more, so it's nice to read some positive feedback.

 

I attempted an observation of the 1.9% illuminated crescent at lunch time today, but literally as soon as I started looking, the sky brewed up some whispy clouds which persisted until an hour ago when Venus had already sunk behind the house.

 

I will have another go tomorrow at 1.5%

and then again on Friday 1.1%

and over the weekend at under 1%, 

 

In these last days of the elongation I will be using the sun (with a filter) as a reference point, then offsetting the telescope from there to Venus.

 

Stay tuned!


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#20 Quinnipiac Monster

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Posted 28 May 2020 - 06:19 AM

The sky was milky in the vicinity of Venus and extremely bright.

I have a Wixey digital angle gauge permanently fixed to the tube of the 300mm which is calibrated to within 0.1°, and a setting circle for azimuth which is generally within a degree or two, even so locating the planet in my 50mm finder was very difficult as it presented an extremely thin curved slither of light against the bright sky.

 

I guess this was due to the milky sky. One day later Venus was easily visible in a 6x30 finder, including the phase! But yes, blue skies that day.

 

This digital angle gauge sounds like a great idea by the way! Do you observe with an alt/az mount? So far I've used my house as a Sun shade, and aimed at Venus by setting the correct altitude on the alt circle; then sweep until I get it in the viewfinder. It's been harder lately, and does not work well for Mercury because the finder is useless and the circles are not good enough to place it in the FOV of my lowest-magnification eypiece (70x, 45').


Edited by Quinnipiac Monster, 28 May 2020 - 06:25 AM.


#21 chrisrnuttall

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Posted 29 May 2020 - 04:29 AM

Hi Quinnipiac Monster!

e

Yes my telescope is a Dobsonian / Alt-Az mount, however I have made a motorised equatorial tracking platform for it to sit on which gives me just under 1 hour of continuous observing without having to push the telescope, great for high magnification visual observing and sketching at the eyepiece.

 

The digital angle gauge is very good, better than a setting circle for setting altitude. You set it to zero on a horizontal surface and fix it to the telescope and start observing. I found it was actually a little less that half a degree off at first when comparing the altitudes of objects in the sky, so I lowered the tube until the gauge was reading 0.5 degrees, then hit the zero button, and now it is perfect. I just wish my azimuth setting circle was so accurate.

 

The milky sky was definitely the problem on the 27th.

I had much more luck yesterday (28th) in a clear blue sky, and easily located Venus by offsetting from the Sun. In fact I observed for 2 hours and had to locate Venus three times as I eventually ran out of equatorial drive each time and had to reset the platform.

 

The seeing was poor and chaotic throughout the session due to the hot sunshine. Nevertheless, I had momentary good views of limb brightening and slightly extended cusps, these were very fleeting in amongst lengthy views of a flickering kaleidoscope of multiple crescents superimposed over one another, and plenty of times when I could have been fooled into thinking I had seen the whole disc of Venus, if I wasn't so cynical by nature!

Sketch to follow when I have the time.

 

I plan to try again later this evening when the Sun is lower in the sky and it's power is diminished somewhat, hoping for steadier air!



#22 chrisrnuttall

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Posted 30 May 2020 - 05:58 AM

Here is the sketch from Thursday the 28th May, it was a long session with a lot of filter swapping and focus knob twiddling!

Not sure how to combat the awful seeing when the sun is 60 degrees up....

 

Orion OD 300. Binoviewer. ADC. Apodizer. 25mm Celestron Xcels x166.

Az 1363°, Alt 55°, Dia 57", Ph 1.5%, CM1 335°, CM2 279°

Seeing Ant V to III, chaotic.

Integrated light (per sketch)

 

Filters;

Apodizer, dims the view a little, maybe helps with the awful seeing, but definitely makes the extremely thin cusps harder to see.

Dew shield as a sun-blocker, doesn't improve the view

W21, W25, W29, dims the sky, but also the planet, maybe helps a tiny bit with the seeing, overall, not a lot better

Baader Neodymuim, nice gentle darkening of the sky, helps with contrast a little.

W47, too aggressive on the thin cusps.

 

Best view was integrated light with no apodizer, and just wait for fleeting moments of better seeing.

Attached Thumbnails

  • Venus template 1.5pc.jpg

Edited by chrisrnuttall, 30 May 2020 - 06:06 AM.

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#23 chrisrnuttall

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Posted 30 May 2020 - 06:04 AM

Better conditions yesterday evening (Friday 29th May), 

I chose to observe between 15:30 and 16:20ut, when the sun was a little lower in the sky and it's power might be a little less. 

 

Orion OD 300. Binoviewer. ADC. Apodizer. 25mm Celestron Xcels x166.

Az 258°, Alt 38°, Dia 57", Ph 1%, CM1 336°, CM2 22°

 

Seeing Ant V to III / II, chaotic, but with slightly longer and slightly better good moments than last morning, usually when a stiff breeze blew and 'straightened out the air', that's my theory anyway.

Continually chasing the seeing by adjusting focus.

 

Integrated light (per sketch)

 

Crescent is bright for 160°, with dim faint cusps extending to around 220°, only visible in the best moments as they are so faint and such low contrast against the blue sky.

 

There isn't a lot of difference between this sketch and that from the day before, but if you compare carefully you can see the cusps extending further as well as the phase getting narrower....

 

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  • Venus template 1pc.jpg

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#24 flt158

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Posted 30 May 2020 - 03:24 PM

Wonderful sketch, Chris!

 

I observed it too on Friday evening. 

 

On my Guide 9.1 DVD it stated Venus had an illumination 0.94% crescent.

For a few seconds I saw the planet before it disappeared behind distant trees. 

She is gone now for me and my scope.

 

Clear skies from Aubrey.  



#25 chrisrnuttall

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Posted 31 May 2020 - 12:57 PM

An observation from this afternoon, Sunday 31st May.

 

I haven't bothered with colour filters at all today. But I have had a couple of other interesting observing aids at my disposal.

 

 

Off axis Mask.

Yesterday I noticed the off-axis light cone from the sun creating a long bright oval illuminated up the inside wall of the Newtonian telescope tube, I put my finger into the top end of this oval and felt pretty hot.

 

So today, because I was worried that this solar image would be nearer to the central axis of the telescope and might shine onto the secondary mirror, I made a simple 125mm off axis mask from cardboard to stop the telescope down, my theory being that if I oriented this correctly I could prevent the solar image reaching the secondary mirror by ensuring it shone onto the inside of the tube instead. It might even improve the tolerance of the telescope to the poor daytime seeing.

 

The mask excluded stray sunlight really nicely, but the resultant image of Venus was not particularly sharp, nor bright and honestly just looked pretty poor compared to the image I have been studying recently.

So I removed the off axis mask, and used a piece of paper to confirm that the cone of sunlight was exiting the front of the telescope between the secondary mirror and the outer tube wall.without intersecting either of them.

I think if I had held it there for just a few seconds this paper would have caught fire pretty quickly. The light was very intense and it really does illustrate just how damaging the sun can be through a telescope.

 

Anyway, as long as I didn't look down the front of the telescope, (or accidentally knock it towards the sun) I was safe to observe Venus like this. The image of Venus using the full 300mm aperture was much better than the image through the 125mm off axis mask, bright and sharp and clear. 

 

 

Cumulus clouds acting as sun shades.

I was reading a report about observing the full atmospheric ring of Venus at inferior conjunction, and it recommended constructing a sun shade to prevent sunlight entering the telescope. The author did warn that at very low elongation angles, the shade does need to be positioned a very long distance in front of the telescope. A quick bit of trigonometry later and I realised that mine would need to be several meters distant, as far as 8 meters away if I want to observe Venus at 2 degrees from the sun. This isnt really a practicable option.

However as luck would have it, the weather has changed a little today. The unbroken hot sunshine in clear blue skies has started to be punctuated with small cumulus clouds passing through on an easterly breeze.

This was actually pretty helpful because periodically a cloud would pass in front of Venus and then a few seconds later it would move away from Venus and pass in front of the Sun, giving me a darker sky to inspect those fine faint cusps against.

The seeing at the boundaries of these clouds was very poor, but once that cleared I would get up to twenty seconds of calm observing conditions with no sun shining into the front of the telescope before the sun shine returned. 

 

In these moments of near-optimum conditions I was afforded pretty good views of the cusps, elongated to a little way short of 270 degrees of the full ring. It's hard to be accurate about this because they fade out gradually at their tips, and, as the seeing and transparency vary, so does the apparent length of these faint extensions. 

In poo transparency, and/or poor seeing, the crescent only appears to extend 180 degrees, but when everything lines up, there was definitely something approaching three quarters of a full ring.

 

So I hope for more little white puffy clouds tomorrow, but I may have to use the 125mm off axis mask if the sun is striking the secondary mirror.

 

 

 

 

Orion OD 300. Binoviewer. ADC. Apodizer. 25mm Celestron Xcels x166.

Az 240°, Alt 48°, Dia 58", Ph 0.4%, CM1 338°, CM2 189°, Elongation 5°

Hot sunshine punctuated by passing cumulus clouds which could be used to block the sun.

Seeing Ant V to III. Poor immediately after the passage of a cloud, but settling thereafter.

 

Integrated light (per sketch)

 

Attached Thumbnails

  • Venus template 0.4pc.jpg

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