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Sol Robbins
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Posts: 1985
Re: 3 Venus Sketches 6.16.07 new [Re: Acheron]
      #1668259 - 06/17/07 09:32 PM

Acheron,

Excellent! Any details like scope size, magnification and filter?

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S.R.


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CarlosEH
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Re: 3 Venus Sketches 6.16.07 new [Re: Acheron]
      #1668593 - 06/18/07 01:46 AM

Vedran,

An excellent observation of Venus showing some albedo features over the disk. Thank you for sharing it with us all.

Carlos

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CarlosEH
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Re: 3 Venus Sketches 6.16.07 new [Re: Acheron]
      #1668660 - 06/18/07 04:04 AM

Percival Lowell may be better known for his Mars Canal Hypothesis (proposed in 1895 in Lowell's book "Mars" ( http://www.wanderer.org/references/lowell/Mars/ ) after observations made at the observatory using an 18-inch (46-cm) refractor), but he also explored the rest of the solar system, including our closest planetary neighbor Venus. Lowell, in August of 1896, turned the newly-erected 24-inch (60-cm) f/16 Refractor towards Venus while awaiting the planet Mars to aproach the Earth closer at opposition in December of the same year. Using such an aperture on the third brightest object in the heavens (-4.5m) it is understandable why Lowell was required to "stop down the aperture" (using an adjustable diaphragm at the 24" lens) to a diameter between 1.6 to 3 inches. At these small apertures the disk of Venus exhibited albedo features describes as "spokes of a wheel radiating from a central hub." Lowell believed these "spider-web features" to be permanent surface features comprised of "rock or sand weathered by aeons of exposure to the Sun" seen through the "diaphanous straw-colored veil" of a dense but strangely transparent atmosphere. With all our current knowledge of the dense atmosphere of Venus and spacecraft images it is difficult to understand why this Bostonian astronomer would believe in such a delusion. We must understand that what was known of the Moon and planets at the end of the nineteenth century was derived from visual observations (although photography was in it's nascency at this time). Spectroscopic observations made in the 1920's by Frank E. Ross provided the existence of a dense Venusian atmosphere.

Noted planetary historian William Sheehan and observer Thomas Dobbins upon researching the subject believe that Lowell may have been actually describing shadows cast by his retinal vessels by converting the stopped-down Lowell refractor into an opthalmoscope (an optical device used in the examination of the ocular fundus). It is interesting to compare the retina of the eye to the Venusian drawings made by Lowell. The similarity is very striking! This optical phenomena made possible by the Lowell refractor producing exit pupils between 0.29 to 0.54 millimeters at small apertures (1.6-3 inches (4-7.6 cm)).

Interesting links;
http://en.wikipedia.org/wiki/Martian_canal
http://www.lowell.edu/index.php
http://www.uapress.arizona.edu/onlinebks/mars/chap07.htm
http://en.wikipedia.org/wiki/Venus

Carlos

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Acheron
scholastic sledgehammer


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Re: 3 Venus Sketches 6.16.07 new [Re: Sol Robbins]
      #1668769 - 06/18/07 07:55 AM

Quote:

Acheron,

Excellent! Any details like scope size, magnification and filter?




Ups

8" F6 Dob, 6mm GSO SuperPlossl, W80A and ND06 filters. Seeing was good for that time of evening.

--------------------
I like sketching...

8" F6 Dob - "Betsy"
12" F5 Dob - "Tristac"


Messier Catalogue - done
Herschel 400 - 189 more to go
http://www.facebook.com/pages/Vizualno-promatranje-Svemira/236702789691880?sk...


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frank5817
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Re: 3 Venus Sketches 6.16.07 new [Re: Acheron]
      #1668840 - 06/18/07 09:19 AM

Vedran,

Nice Venus sketch as are the others at your web page. Cloud features look great.

Frank

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My Gallery


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Special Ed
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Reged: 05/18/03
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Re: 3 Venus Sketches 6.16.07 new [Re: frank5817]
      #1669426 - 06/18/07 03:05 PM

Vedran, nice job on your sketch--your filter combo allowed you a good view of the cloud shadings.

Carlos, thanks for the information on Lowell and the "spokes". The history and background of the great visual observers of the past is always fascinating and instructive.

--------------------

Michael Rosolina
Celestron CGE Pro 1400 f/11 SCT
1980 Orange Tube C8 f/10 SCT
4.25" f/4.2 Astroscan Reflector
50mm f/10 Galileoscope
40mm PST f/10
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Acheron
scholastic sledgehammer


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Re: 3 Venus Sketches 6.16.07 new [Re: Special Ed]
      #1669465 - 06/18/07 03:28 PM

Quote:

Vedran, nice job on your sketch--your filter combo allowed you a good view of the cloud shadings.




Thank you for comment, but...
Cloud features where much more subtle than this. I almost think that my imagination played tricks with me last night.
One second you see them and another second not.

--------------------
I like sketching...

8" F6 Dob - "Betsy"
12" F5 Dob - "Tristac"


Messier Catalogue - done
Herschel 400 - 189 more to go
http://www.facebook.com/pages/Vizualno-promatranje-Svemira/236702789691880?sk...


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Tommy5
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Reged: 03/28/04
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Re: 3 Venus Sketches 6.16.07 new [Re: Acheron]
      #1670421 - 06/19/07 12:31 AM

great sketch Acheron,other observors have also commented on the illusive nature of these features some were reluctant to draw or mention them thinking that they were not really there,but they are and now we all have observed similar albedo markings on venus, congrads again on your sketch.

Edited by Tommy5 (06/20/07 04:24 PM)


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Special Ed
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Re: Venus Sketch 6.19.07 new [Re: Tommy5]
      #1673317 - 06/20/07 02:11 PM Attachment (83 downloads)

Here's a sketch I did Monday evening just before local sunset (19 June UT). The dusky shadings appeared the same in the W23A and double stacked filter view. The cusp extensions were equal north and south but I messed up a little on the north cusp with ink and couldn't fix it. Also, the phase may be a little off--it's hard to draw accurately right now--those cusp extensions make it seem more pronounced than it really is, I think (the phase was 44%).

Sketch was done from an intensity diagram with an HB pencil and a stump loaded with graphite. Black ink for the phase.

Regards,

Attachment

--------------------

Michael Rosolina
Celestron CGE Pro 1400 f/11 SCT
1980 Orange Tube C8 f/10 SCT
4.25" f/4.2 Astroscan Reflector
50mm f/10 Galileoscope
40mm PST f/10
APM Germany HD 15x70 binoculars
Canon 12x36 IS II binoculars
Mark I Eyeball
My CN Gallery


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Sol Robbins
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Reged: 12/01/03
Posts: 1985
Re: Venus Sketch 6.19.07 new [Re: Special Ed]
      #1673942 - 06/20/07 07:04 PM

Excellent Michael. Last time the cusps you mention had a very defined edge w/red filter.

Lastly, did the brightening that appears inward from the limb, at about 10 o'clock in your sketch, pulse with varying brightness with changes in seeing? Though different, these "spots" looked very bright at times and similar to Martian limb brighteningThanks,

--------------------
S.R.


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frank5817
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Re: Venus Sketch 6.19.07 new [Re: Sol Robbins]
      #1674208 - 06/20/07 09:55 PM Attachment (78 downloads)

Michael,
Very nice observation of Venus and the albedo features. This has been a fun learning experience for me. I have done more Venus observing in the last month than in the previous 20 years. I have you and Sol to thank for this awakening.

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Sky transparency was average before sunset. Venus was easy to pick up visually at 7:50 pm local time. I attached a Wratten 47 violet filter to a 6mm ortho. eyepiece to view and sketch the albedo features of Venus.

Equipment: 10" f/5.7 Dobsonian, 6mm orthoscopic eyepiece (241X)
Wratten 47 filter
Seeing: Pickering 5
Transparency: below average 3/5
Time: 1:05-0:25 UT 6-21-2007
Sketching:
9"x12" black Strathmore Artagain paper background only
White sketching paper cut to shape of planet
2H, B and HB graphite pencils blended with a blending stump
brightness slightly adjusted using Imageenhance.

Frank McCabe

Attachment

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My Gallery


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Sol Robbins
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Re: Venus Sketch 6.19.07 new [Re: frank5817]
      #1674369 - 06/20/07 11:34 PM

Frank,

WOW!

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S.R.


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CarlosEH
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Re: Venus Sketch 6.19.07 new [Re: Sol Robbins]
      #1674720 - 06/21/07 07:49 AM

Frank and Michael,

Excellent observations of Venus showing albedo features over the disk. The Venus observations continue to be impressive. Thank you for sharing them with us all.

Carlos

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Special Ed
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Re: Venus Sketch 6.19.07 new [Re: Sol Robbins]
      #1674890 - 06/21/07 10:10 AM

Sol, Frank, Carlos,

Thank you all. Frank, terrific sketch--it seems that Venus continues to have a hold on us.


Quote:

Last time the cusps you mention had a very defined edge w/red filter...did the brightening that appears inward from the limb, at about 10 o'clock in your sketch, pulse with varying brightness with changes in seeing? Though different, these "spots" looked very bright at times and similar to Martian limb brighteningThanks,




Sol, I agree--the cusps were very well defined, I would even say prominent, in red light and with the stacked filters.

The bright area you refer to is a little more shaded than the scanner picked up. It did vary in intensity as you describe but as you know, Venus won't sit still for very long so it's hard to confirm anything.

One other thing I noticed that I didn't include in my brief report was that, while bright, the limb arc did not appear as bright as in past observations. In my diagram, I put it at 9.5 instead of 10.0 just to show a slight perceived change.

Susan Delaney on the Starrynights Yahoo group kindly provided this link to the book Celestial Objects for Common Telescopes by Rev. T.W. Webb published in 1859. It has some fascinating stuff in it about early Venus observations. More on Rev. Webb can be seen here.

Best to all,

--------------------

Michael Rosolina
Celestron CGE Pro 1400 f/11 SCT
1980 Orange Tube C8 f/10 SCT
4.25" f/4.2 Astroscan Reflector
50mm f/10 Galileoscope
40mm PST f/10
APM Germany HD 15x70 binoculars
Canon 12x36 IS II binoculars
Mark I Eyeball
My CN Gallery


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Tommy5
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Re: Venus Sketch 6.19.07 new [Re: Special Ed]
      #1676319 - 06/22/07 12:30 AM

frank and micheal, great sketches of venus we certainly have a lot of data on cloud patterns of venus.

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frank5817
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Re: Venus Sketch 6.19.07 new [Re: Tommy5]
      #1694596 - 07/01/07 11:09 PM Attachment (89 downloads)

Sky transparency was above average all day. I was able to pick Venus out with the telescope before it crossed the local meridian in the afternoon. From Venus I moved the scope to the position of Saturn, but could not pull it out of the blue background. So I have had better transparency in the past. Venus was easy to pick up visually by 4 pm local time. I attached a Wratten 47 violet filter to a 6mm ortho. eyepiece to view and sketch the albedo features of Venus.
About 3.5 hours after finishing the sketch I was able to see both Venus and Saturn in the same field of view using a 28 mm eyepiece. That doesn’t happen ever day.

Equipment: 10" f/5.7 Dobsonian, 6mm orthoscopic eyepiece (241X)
Wratten 47 filter
Seeing: Pickering 6
Transparency: above average 3.5/5
Time: 22:00-22:20 UT 7-1-2007
Sketching:
9"x12" black Strathmore Artagain paper background only
White sketching paper cut to shape of planet
2H, B and HB graphite pencils blended with a blending stump
brightness slightly darkened using Imageenhance.

Frank McCabe

Attachment

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My Gallery


Edited by frank5817 (07/01/07 11:12 PM)


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Special Ed
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Re: Venus Sketch 6.19.07 new [Re: frank5817]
      #1694664 - 07/01/07 11:35 PM

Nice sketch, Frank. The crescent phase is really taking hold now. Having Saturn nearby was a real bonus, wasn't it?

--------------------

Michael Rosolina
Celestron CGE Pro 1400 f/11 SCT
1980 Orange Tube C8 f/10 SCT
4.25" f/4.2 Astroscan Reflector
50mm f/10 Galileoscope
40mm PST f/10
APM Germany HD 15x70 binoculars
Canon 12x36 IS II binoculars
Mark I Eyeball
My CN Gallery


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frank5817
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Re: Venus Sketch 6.19.07 new [Re: Special Ed]
      #1694874 - 07/02/07 02:43 AM

Michael,
Thanks. You are right, the crescent phase and the decreasing distance between earth and Venus are now notable.
Seeing Saturn and Venus in the same field of view was very impressive.
Frank

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Erix
Toad Lily


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Re: Venus Sketch 6.19.07 new [Re: frank5817]
      #1695081 - 07/02/07 08:17 AM

This is really cool stuff! Great job to all of you!

--------------------
Erika
Automatic doors make me feel like a Jedi.

Zhumell 16", 10" LX200 Classic,Celestron 102 XLT, ETX70-AT, DS Maxscope 60mm, AT6RC
PCW Memorial Observatory


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Sol Robbins
Carpal Tunnel


Reged: 12/01/03
Posts: 1985
07.03.07 Venus Sketch new [Re: Erix]
      #1696996 - 07/03/07 07:22 AM Attachment (74 downloads)

This Venus observation was made during twilight with very good seeing conditions. Venus now sinks rapidly and there is not a lot of time to observe it as nearby trees get in the way.

The crescent phase is becoming more pronounced and Venus' apparent has increased.

Observation was made with my 9.75" @ 397x with a Wratten 25A red filter.

Sketch was done with 4H and HB pencils. Blending done with my fingers and whites were erased out.

Best.

Attachment

--------------------
S.R.


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