Astronomy C

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Re: Astronomy C

Post by c0c05w311y » February 14th, 2019, 10:25 pm

idislikeboomi wrote:Anybody have the image set for the carnegie mellon test?
Sure. https://drive.google.com/file/d/12qdcF8 ... sp=sharing
I'm pretty sure this is the right version.
Let me know if you have any questions or comments about the exam!

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Re: Astronomy C

Post by Zxcvbnm123 » February 16th, 2019, 7:11 pm

Does anyone know where I can find the 2019 Golden Gate Invitational test?

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Re: Astronomy C

Post by EastStroudsburg13 » February 19th, 2019, 9:33 am

Golden Gate Invitational tests will be released publicly on their website on March 9.
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Re: Astronomy C

Post by Alke » February 20th, 2019, 4:51 pm

Hi everyone!

I did astronomy two seasons ago but I'm back! I'm a little rusty and I am always running out of time. Thus, do you all have tips for time management/splitting up the work with your partner?

I'm trying to think through some strategies like having one person do math and the other do mulitple choice. However, I don't know how well that'll work!

-Thanks

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Re: Astronomy C

Post by Name » February 20th, 2019, 5:27 pm

Alke wrote:Hi everyone!

I did astronomy two seasons ago but I'm back! I'm a little rusty and I am always running out of time. Thus, do you all have tips for time management/splitting up the work with your partner?

I'm trying to think through some strategies like having one person do math and the other do mulitple choice. However, I don't know how well that'll work!

-Thanks
I'd suggest splitting the test. I usually take the DSOs (or everything besides math), while my partner takes all the math (even though math is my favorite part of astro :cry: ). We're usually capable of finishing the test without too much of a problem. Near the end we usually look into the other person's section to help potentially solve questions that the other person didn't get/check over a bit, so i'd still recommend being knowledgable in your partner's section. Figure out which sections you and your partner would rather do, and then split the test accordingly.
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Re: Astronomy C

Post by PM2017 » February 20th, 2019, 6:30 pm

Alke wrote:Hi everyone!

I did astronomy two seasons ago but I'm back! I'm a little rusty and I am always running out of time. Thus, do you all have tips for time management/splitting up the work with your partner?

I'm trying to think through some strategies like having one person do math and the other do mulitple choice. However, I don't know how well that'll work!

-Thanks
We split the test right down the middle and take 30 seconds or so to scan our halves and see which pages we're most comfortable with/have the most points and get those done. I generally hand the in-depth DSO questions to my partner, while she gives me the majority of the calculations. We try to get our respective sections done by the 30-minute mark and then go onto finish the conceptual section, since that's the most luck-based. (unless I see HR diagrams or light curves or something else that's not really trivia).

Also, we circle the question numbers that we don't immediately get and move on. We come back after we finish everything we are comfortable with and then we discuss amongst each other.

Honestly, if you looked at us without realizing we were any good, you would probably laugh at "those two kids who were arguing with each other throughout the test," and wouldn't think we had any chemistry together. But, I would say our achievements say otherwise... :).

(sorry, I don't normally boast, but it's a somewhat funny story.)
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Re: Astronomy C

Post by ET2020 » February 26th, 2019, 11:59 am

I've noticed that there seem to be two different equations used to calculate recessional velocity from redshift. The more commonly used one, v = Z*c, works fine for relatively close objects, but creates a problem for objects with redshifts > 1. The equation is problematic because it implies that we should not be able to see things with z > 1, since they would be receding faster than light, and therefore the light would not be able to reach us. However, there have been many objects observed to have z >> 1. The correct equation, V = c*[(z^2+2z)/(z^2+2z+2)], gives accurate answers even for distant objects. Unfortunately, I've gotten a few practice questions wrong because the test writer used the simplified version of the equation. Which one should I use?
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Re: Astronomy C

Post by syo_astro » February 26th, 2019, 12:50 pm

ET2020 wrote:I've noticed that there seem to be two different equations used to calculate recessional velocity from redshift. The more commonly used one, v = Z*c, works fine for relatively close objects, but creates a problem for objects with redshifts > 1. The equation is problematic because it implies that we should not be able to see things with z > 1, since they would be receding faster than light, and therefore the light would not be able to reach us. However, there have been many objects observed to have z >> 1. The correct equation, V = c*[(z^2+2z)/(z^2+2z+2)], gives accurate answers even for distant objects. Unfortunately, I've gotten a few practice questions wrong because the test writer used the simplified version of the equation. Which one should I use?
This is always a great question! Similar issues come up for other equations too (like whether to assume circular orbits, etc). One way is to ask the proctor something like "there are two possible equations to use for this question, should we account for relativistic effects?" But I'm aware on the spot that can take away precious time and be cumbersome, especially if the proctor can't answer or doesn't know.

I would guess most test writers shoot for the simpler equations, but I know that's not a guarantee either. Thoughts from others?
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Re: Astronomy C

Post by Unome » February 26th, 2019, 1:11 pm

syo_astro wrote:
ET2020 wrote:I've noticed that there seem to be two different equations used to calculate recessional velocity from redshift. The more commonly used one, v = Z*c, works fine for relatively close objects, but creates a problem for objects with redshifts > 1. The equation is problematic because it implies that we should not be able to see things with z > 1, since they would be receding faster than light, and therefore the light would not be able to reach us. However, there have been many objects observed to have z >> 1. The correct equation, V = c*[(z^2+2z)/(z^2+2z+2)], gives accurate answers even for distant objects. Unfortunately, I've gotten a few practice questions wrong because the test writer used the simplified version of the equation. Which one should I use?
This is always a great question! Similar issues come up for other equations too (like whether to assume circular orbits, etc). One way is to ask the proctor something like "there are two possible equations to use for this question, should we account for relativistic effects?" But I'm aware on the spot that can take away precious time and be cumbersome, especially if the proctor can't answer or doesn't know.

I would guess most test writers shoot for the simpler equations, but I know that's not a guarantee either. Thoughts from others?
I've never seen a test writer use the relativistic version of the equation on a test, so I pretty much always use the non-relativistic equation. Although, at a particularly competitive tournament if the test doesn't specify, I'd probably ask.
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Re: Astronomy C

Post by Adi1008 » February 26th, 2019, 1:26 pm

Unome wrote:
syo_astro wrote:
ET2020 wrote:I've noticed that there seem to be two different equations used to calculate recessional velocity from redshift. The more commonly used one, v = Z*c, works fine for relatively close objects, but creates a problem for objects with redshifts > 1. The equation is problematic because it implies that we should not be able to see things with z > 1, since they would be receding faster than light, and therefore the light would not be able to reach us. However, there have been many objects observed to have z >> 1. The correct equation, V = c*[(z^2+2z)/(z^2+2z+2)], gives accurate answers even for distant objects. Unfortunately, I've gotten a few practice questions wrong because the test writer used the simplified version of the equation. Which one should I use?
This is always a great question! Similar issues come up for other equations too (like whether to assume circular orbits, etc). One way is to ask the proctor something like "there are two possible equations to use for this question, should we account for relativistic effects?" But I'm aware on the spot that can take away precious time and be cumbersome, especially if the proctor can't answer or doesn't know.

I would guess most test writers shoot for the simpler equations, but I know that's not a guarantee either. Thoughts from others?
I've never seen a test writer use the relativistic version of the equation on a test, so I pretty much always use the non-relativistic equation. Although, at a particularly competitive tournament if the test doesn't specify, I'd probably ask.
I'd say that there's a lot of variation and it'd hard to generalize in either direction. As a competitor, I only saw test writers use the relativistic form, which is the opposite of Unome's experience. I would recommend either asking (as syo_astro suggested) or calculating both and saying "this one is taking relativity into account, while this one does not" if the test doesn't specify.
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