Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

infinity focus


mindburner

Recommended Posts

I know I shouldn't feed online trolls, but I was having a discussion with someone and they came out with the startling claim that stellar distances were wrong and inaccurate and that m31 for example was much closed then the 2.5 million LY we all know it is. 

After laughing and going on about gravity etc I asked why!

One of their 'proof's was that they didn't have to adjust their scope from focusing on the moon to say a nearby star. I explained about infinity focus and lens range. But I was hoping for some more info on infinity focus and such.

City lights 20 miles away would also be in the same focusing  range as say the moon. By their logic then the moon must be 20 miles away. 

 

Daft I know but never ceases to amaze me the daft stuff on the internet.

Link to comment
Share on other sites

Tell them that you've worked out their problem. It's their brain..it appears to have developed a fault. Tell them to book it into a nearby approved service centre* for some warranty work** or a tuneup**. Otherwise it's a bit like a car that's showing the "Check Engine" warning lamp. It'll probably drive OKish for years but anyone that knows about these things will spot it and wonder how the heck that the owner has allowed it to continue like that for so long.

 

 

*School or Library

**Education or learning.

Link to comment
Share on other sites

Reminds of a futile argument I had with someone years ago when talking about space flight. It was on the lines of how can space be a vacuum as exhaust gases need something to push against to move forward. No amount of quoting Newton's laws of motion made the slightest bit of difference. He went on to become an insurance salesman, no great surprise.

Link to comment
Share on other sites

Not long ago I ran into a strange issue that is related to this thread ...

My friend has the exact same setup as mine (80ED with focal reducer and a Canon 1000D DSLR) As he was preparing for the night he tried to determine where is focus was so he could mark it on the drawtube to make it easier to fine tune the focus at night.

He had to pull the drawtube out to focus on mountains in the distance, even then he was still out of focus, he then had to pull away the DSLR an inch or so to get into focus... I was puzzled as to achieve focus I only have to move an inch or so from a fully retracted drawtube. My only guess was that focusing on mountains a few Km away was not the same as focusing on distant stars. My friend replied that it was the same as focusing to infinity so that should not make a difference...

We tested again at night on a star with a bahtinov mask and, as I expected, he was able to focus with the drawtube at half course.

I too have read that focusing on distant objects was the same as focusing to infinity but maybe this only applies to shorter FL ? Any thoughts on this ?

Link to comment
Share on other sites

On ‎8‎/‎18‎/‎2017 at 09:48, mindburner said:

thanks guys. I know I shouldn't have taken the bait but it was quite funny

 

thread here if anyone is very bored:)

(hope it's ok mods to post this link)

 

 

 

Well, you know how those Venusians can be, not having a Moon of their own to trash. Wouldn't surprise me at all for one of them on a picnic to Sea of Tranquility to throw their Moon Pie wrappers around, and maybe bend the flagpole a bit.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.