Scrutable

This might be of interest to people here.
Astronomy with an online telescope
https://www.open.edu/openlearn/ocw/mod/ ... p?id=74591

Lots of others here.

Any take your fancy?

Some of them look interesting. I did explore the idea of another science degree with the OU, but I was put off by a course structure that gave no credit or leeway for previous experience, I would have basically have had to start by doing an A level style access course first and the expense made it untenable.

Boustrophedon wrote: ↑

Mon Feb 24, 2020 7:37 pm

Some of them look interesting. I did explore the idea of another science degree with the OU, but I was put off by a course structure that gave no credit or leeway for previous experience, I would have basically have had to start by doing an A level style access course first and the expense made it untenable.

I too was looking forward to using the OU to improve my education, but the course fees put the kibosh on that. I was looking forward to retiring somewhere warm and doing some serious study. Sigh.

Gfamily wrote: ↑

Mon Feb 24, 2020 7:06 pm

This might be of interest to people here.
Astronomy with an online telescope
https://www.open.edu/openlearn/ocw/mod/ ... p?id=74591

Been working my way through this. It's pretty good but the multi choice quizzes are annoying.
1. "Hamal is a magnitude 2.0 star and Al Dhanab has magnitude 3.0. Approximately how many times brighter is Hamal than Al Dhanab?"
My answer of 2.51 marked as wrong. The correct answer is 2.5.

2."In a reflecting telescope the primary element or objective is a X mirror."
Options for X included curved and convex. I answered convex as that was my vague recollection from O level physics but the correct answer is curved. Can anyone explain to me why convex is wrong?

Anyway only a minor irritation as the scores don't count towards anything. In the next lesson we get to play with the COAST telescope in Tenerife.

MartinDurkin wrote: ↑

Wed Mar 04, 2020 11:59 am

Gfamily wrote: ↑

Mon Feb 24, 2020 7:06 pm

This might be of interest to people here.
Astronomy with an online telescope
https://www.open.edu/openlearn/ocw/mod/ ... p?id=74591

Been working my way through this. It's pretty good but the multi choice quizzes are annoying.
1. "Hamal is a magnitude 2.0 star and Al Dhanab has magnitude 3.0. Approximately how many times brighter is Hamal than Al Dhanab?"
My answer of 2.51 marked as wrong. The correct answer is 2.5.

2."In a reflecting telescope the primary element or objective is a X mirror."
Options for X included curved and convex. I answered convex as that was my vague recollection from O level physics but the correct answer is curved. Can anyone explain to me why convex is wrong?

Convex means it's curved outwards, and causes incoming parallel rays to diverge. You need a concave mirror for the primary of an imaging optical telescope*.

*Other telescopes are available.

dyqik wrote: ↑

Wed Mar 04, 2020 1:31 pm

Convex means it's curved outwards, and causes incoming parallel rays to diverge. You need a concave mirror for the primary of an imaging optical telescope*.

*Other telescopes are available.

Haha f.cking hell I triple checked that I had got convex and concave the right way round and still got them confused. Thanks for not calling me a moron.

MartinDurkin wrote: ↑

Wed Mar 04, 2020 2:04 pm

dyqik wrote: ↑

Wed Mar 04, 2020 1:31 pm

Convex means it's curved outwards, and causes incoming parallel rays to diverge. You need a concave mirror for the primary of an imaging optical telescope*.

*Other telescopes are available.

Haha f.cking hell I triple checked that I had got convex and concave the right way round and still got them confused. Thanks for not calling me a moron.

concave is hollowed out...

dyqik wrote: ↑

Wed Mar 04, 2020 2:12 pm

MartinDurkin wrote: ↑

Wed Mar 04, 2020 2:04 pm

dyqik wrote: ↑

Wed Mar 04, 2020 1:31 pm

Convex means it's curved outwards, and causes incoming parallel rays to diverge. You need a concave mirror for the primary of an imaging optical telescope*.

*Other telescopes are available.

Haha f.cking hell I triple checked that I had got convex and concave the right way round and still got them confused. Thanks for not calling me a moron.

concave is hollowed out...

Yeah I used to know that, and I can picture the ray diagram clearly in my mind. My only excuse is that when I did check it the first google hit was this page, https://www.ducksters.com/science/physi ... scopes.php which says

Reflecting telescopes use mirrors instead of lenses to focus the light. A convex mirror is used to gather light and reflect it back to a focal point.

Getting old is no fun.

MartinDurkin wrote: ↑

Wed Mar 04, 2020 3:35 pm

Yeah I used to know that, and I can picture the ray diagram clearly in my mind. My only excuse is that when I did check it the first google hit was this page, https://www.ducksters.com/science/physi ... scopes.php which says

Reflecting telescopes use mirrors instead of lenses to focus the light. A convex mirror is used to gather light and reflect it back to a focal point.

Getting old is no fun.

I've just sent them a correction. From my work email address, with my full title in.

dyqik wrote: ↑

Wed Mar 04, 2020 4:42 pm

I've just sent them a correction. From my work email address, with my full title in.

Blackboard Monitor Dyqik; tell us you used your Blackboard Monitor Dyqik title

MartinDurkin wrote: ↑

Wed Mar 04, 2020 11:59 am

1. "Hamal is a magnitude 2.0 star and Al Dhanab has magnitude 3.0. Approximately how many times brighter is Hamal than Al Dhanab?"
My answer of 2.51 marked as wrong. The correct answer is 2.5.

I don't know if this is what they are thinking, but 2.51 is spurious precision given the magnitudes are only given to two sf. But that's picky.

dyqik wrote: ↑

Wed Mar 04, 2020 4:42 pm

MartinDurkin wrote: ↑

Wed Mar 04, 2020 3:35 pm

Yeah I used to know that, and I can picture the ray diagram clearly in my mind. My only excuse is that when I did check it the first google hit was this page, https://www.ducksters.com/science/physi ... scopes.php which says

Reflecting telescopes use mirrors instead of lenses to focus the light. A convex mirror is used to gather light and reflect it back to a focal point.

Getting old is no fun.

I've just sent them a correction. From my work email address, with my full title in.

It's fixed now.