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Venus now in a 60 refractor

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#1 grif 678

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Posted 06 January 2020 - 06:07 PM

How much power should be required to see the phases of Venus in a 60mm refractor.



#2 Garyth64

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Posted 06 January 2020 - 07:15 PM

Just about any power the 60mm can make.  Just because it's small doesn't mean you can't see them.


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#3 Jdrasberry

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Posted 06 January 2020 - 08:07 PM

A moon filter or a variable polarizer filter will help you reduce its brightness so is not so intense. .

 

Joe


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#4 aa6ww

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Posted 06 January 2020 - 08:22 PM

60mm is an excellent size to observe Venus without brightness issues. Its perfect on the moon also.

 

...Ralph



#5 Jeff B

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Posted 06 January 2020 - 09:29 PM

How much power should be required to see the phases of Venus in a 60mm refractor.

Not much at all.  Even just 25X will show the phases clearly.  In fact, a good pair of 10x50 binoculars can do a good job too.


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#6 Jon Isaacs

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Posted 06 January 2020 - 09:51 PM

It depends on the current phase. Right now it's 80% illuminated, it takes some real magnification to clearly see the phase. Increasing the magnification also dims the view so that's a good thing.

 

Right now, Venus is 13 arc-seconds in diameter. The phase represents a difference of about 4 arc-seconds. That's not so easily seen. 

 

Right now I'd go 100x-200x. That's what I'm using with my 80 mm and under scopes. 

 

When Venus is a thin crescent nearly 60arcseconds in diameter, the phase is easily seen at rather low powers but currently, that's not the case.

 

Jon


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#7 grif 678

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Posted 06 January 2020 - 10:11 PM

I tried it tonight with an 18mm eyepiece, giving 50X, but it was so bright the crescent was just overwhelmed by the brightness. But if it is 80% illuminated, I guess that is why it was that way.



#8 Jon Isaacs

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Posted 08 January 2020 - 07:16 AM

I tried it tonight with an 18mm eyepiece, giving 50X, but it was so bright the crescent was just overwhelmed by the brightness. But if it is 80% illuminated, I guess that is why it was that way.

If you double the magnification to 100x, the intensity, surface brightness will be 1/4 of what it was. If you triple it to 150x, it will be 1/9th as bright as it was.

 

And the difference between the fully illuminated side and the other side is only about 4 arc-seconds so increasing the magnification helps.  For a comparison, Castor is about 5 arc-seconds, not much.

 

Jon


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#9 Uranotopia

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Posted 08 January 2020 - 07:55 AM

I tried it tonight with an 18mm eyepiece, giving 50X, but it was so bright the crescent was just overwhelmed by the brightness. But if it is 80% illuminated, I guess that is why it was that way.

I also would advice a higher magnification, and your 60mm refractor will be succesful showing the phase... or do you have very turbulent seeing? Then perhaps a orange or red filter could help a little. Another problem can be the atmospheric dispersion, there may also a filter be of little effect.

On the other hand, I can remember that in former years there were some advices to use a yellow filter for Venus.



#10 Jeff B

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Posted 08 January 2020 - 08:53 AM

And you can always use neutral density or variable polarizing filters to cut down the intensity and glare.


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#11 daquad

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Posted 08 January 2020 - 01:45 PM

I tried it tonight with an 18mm eyepiece, giving 50X, but it was so bright the crescent was just overwhelmed by the brightness. But if it is 80% illuminated, I guess that is why it was that way.

It won't be a crescent.  It will be gibbous.

 

Dom Q.


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#12 Sketcher

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Posted 08 January 2020 - 02:29 PM

I tried it tonight with an 18mm eyepiece, giving 50X, but it was so bright the crescent was just overwhelmed by the brightness. But if it is 80% illuminated, I guess that is why it was that way.

The overwhelming brightness can be tamed by making your Venus observations before the sky gets very dark.  I suggest gaining some familiarity with where to look for Venus (relative to landmarks, buildings, trees, etc.) along with noting how the planet's position appears to change with time.  Then on subsequent evenings start looking for the planet earlier, when the sky isn't as dark.  A brighter sky will make the planet appear to be less brilliant.

 

That's the "cheap" way of dealing with the situation.  A more expensive approach to accomplish the same thing would be to use filters to make the planet appear less brilliant.

 

I would not suggest reducing the scope's aperture.  With either of the two methods mentioned above you retain the full resolution of your telescope.

 

As for magnifications, I don't know what magnifications you have available -- other than 50x.  At the moment, Venus will appear to be quite small at 50x, but that "might" be enough magnification, especially if you take measures to reduce that overwhelming brilliance situation.  If you can increase your magnification to 100x or more, that ought to make a noticeable improvement.  If you can't, continue trying with 50x.  Galileo noted the phases of Venus (including the gibbous phase) with his primitive telescopes that reportedly went up to a maximum magnification of about 30x.

 

With time, your views will improve.  Besides your gaining more experience, Venus and Earth are currently moving closer to one another.  So Venus will be gradually increasing in its apparent size.  By March 26th Venus's phase will have changed from a nearly full (80% illuminated) gibbous to a half-full (50% illuminated) quarter.  Furthermore, the apparent size of the planet will be increasing from its current 13.5 arc-second diameter to a nearly twice as large 24 arc-second diameter.

 

So continue with your Venus observations.

 

One more suggestion:  By taking the time to at least "try" to sketch the planet during each observing session, you may discover that you've been missing some of what your telescope has been trying to reveal to you.


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#13 Jon Isaacs

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Posted 08 January 2020 - 02:40 PM

I would not suggest reducing the scope's aperture.  With either of the two methods mentioned above you retain the full resolution of your telescope.

 

 

In most situations, I would agree with you. However with fast achromats viewing a bright object like Venus where only the phase is of interest, the dramatic reduction in chromatic aberration possible with an aperture mask can be worthwhile. 

 

For some perspective, this is a Sky Safari simulation of the current phase of Venus. 

 

Venus Sky Safari 1.jpg

 

In the eyepiece, it will be smaller than this.

 

Jon


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#14 Garyth64

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Posted 08 January 2020 - 04:14 PM

I got a little 50mm x 600mm Tasco that I've been wanting to point at Venus, but the clouds haven't cooperated.  Maybe tonight and I'll add my results.


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#15 aa6ww

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Posted 08 January 2020 - 06:24 PM

It may be clear tomorrow based on the forecast to take a look at Venus for the first time this year. Looking forward to that!

 

...Ralph


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#16 Garyth64

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Posted 08 January 2020 - 07:34 PM

I got a little 50mm x 600mm Tasco that I've been wanting to point at Venus, but the clouds haven't cooperated.  Maybe tonight and I'll add my results.

Dang! It was in the neighbor's trees.  I'll have to plan much better in advance.  And it is nice and clear right now.


Edited by Garyth64, 08 January 2020 - 07:35 PM.

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#17 Tropobob

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Posted 09 January 2020 - 04:53 AM

I just had a look at Venus with a 4" refractor using 35x. I could easily see the phase.  35x does not stretch the capabilities of a 60mm, so it should be seen with that also. It was during the twilight and that does make the phase easier to see than against a dark sky.



#18 aa6ww

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Posted 12 January 2020 - 01:19 PM

Venus is pretty fun observing in the daytime, once it gets to crescent mode. If you have a scope that has difficultly providing sharp views, day time observing is pretty fun. Even Saturn and Jupiter are fun in the day time.

 

A few nights ago I was using my small FC-60 refractor to observe Venus. The scope requires almost no acclimation time so its very sharp right from the start. Small aperture refractors seem to do best on Venus when its chasing the sun because they tend to be low into the horizon where most of the atmospheric muck is at. 

I think the key to sharp views of Venus is to have your scope fully acclimated, even before you start setting it up. Since we are usually liimited to an hr or so before Venus dips into the dirty part of the sky, having everything ready before you start always helps.

 

I'm looking forward to Venus as a crescent. Makes for fun day time observing.

 

....Ralph



#19 Jeff B

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Posted 12 January 2020 - 01:56 PM

I was in southern Florida last week, on the gulf coast, mooching off of my brother and his wife at their time share there.  A large dry air mass had settled in we had some spectacular sunsets.  I loved going down to the beach about a half hour before sunset and pointing out Venus to folks who were also down there for the view.

 

They all loved it!  Though is was so amazing they could actually see the planet in broad daylight if you knew where to look.

 

Fun and easy astro-outreach.

 

Jeff


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#20 rkelley8493

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Posted 12 January 2020 - 03:07 PM

Here's a photo I took with my phone through my refractor a few days ago. Venus is really bright.. so bright it almost hurts. I used a 25% neutral density filter to help cut down on the glare. 

I think the magnification was around 130x, but you can still see the gibbous shape at lower power.

 

11venus.jpg


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#21 Uranotopia

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Posted 13 January 2020 - 04:23 AM

Here's a photo I took with my phone through my refractor a few days ago. Venus is really bright.. so bright it almost hurts. I used a 25% neutral density filter to help cut down on the glare. 

I think the magnification was around 130x, but you can still see the gibbous shape at lower power.

 

attachicon.gif11venus.jpg

Great snapshot!

Thx for showing this pic, that proves what you can see in small refractor.


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