5
$\begingroup$

I'm curious for an estimate of how wide a field the Hubble space telescope has observed. Say, for example, how many times it has changed its pointing, and what fraction of that were revisiting the same field.

$\endgroup$
  • $\begingroup$ Are you talking about total area of sky observed by Hubble in its 25+ years? $\endgroup$ – Dean Jun 29 '17 at 16:38
  • $\begingroup$ @Dean Yes. How much has this pinhole view kind of telescope been able to view of the sky during its long lifetime? $\endgroup$ – LocalFluff Jun 29 '17 at 16:41
  • $\begingroup$ wow I wouldn't even want to guess, I know there are websites and archives for viewing all the images but I don't know any fact sheet that keeps track of number or size of fields viewed. $\endgroup$ – Dean Jun 29 '17 at 16:48
  • 1
    $\begingroup$ @zephyr I highly doubt it with a FOV of 162" !! That would take over 20million individual pointings. And the PHAT survey didn't even cover the whole galaxy because its so time consuming with such a small FOV, they decided to just do one half as its fairly symmetrical. $\endgroup$ – Dean Jun 29 '17 at 21:44
  • 1
    $\begingroup$ @Dean You're right. I guess I should've looked at the actual numbers first. It isn't really feasible for it to have covered the entire sky. Or even a large part of it. $\endgroup$ – zephyr Jun 30 '17 at 13:52
5
$\begingroup$

25 years of say 16 orbits/day is a (very over-estimated) maximum of 146,000 pointings.

The largest instrument is the various incarnations of the optical imager with a FOV of 6 (WFPC2) to 11 (ACS) square arcminutes. Thus the absolute maximum fraction of the sky (40,000 square degrees) that can have been covered is 1 per cent. And this is a big overestimate, since many parts of the sky have received many repeated pointings (e.g. the Hubble deep field).

$\endgroup$
  • $\begingroup$ Isn't the FOV set by the mirror shape? How could different instruments have different FOV? $\endgroup$ – LocalFluff Jul 1 '17 at 2:55
  • $\begingroup$ @LocalFluff The angular area on the sky covered by an instrument is what usually determines the field of view if, as in the HST, the focal plane is underfilled. What lies outside this is irrelevant, since no data are collected. Different detectors have different physical sizes and hence different fields of view. $\endgroup$ – Rob Jeffries Jul 1 '17 at 8:56
2
$\begingroup$

I found another discussion on the same topic here:

https://forum.cosmoquest.org/archive/index.php/t-18214.html

Which is pretty old, but at least some numbers. According to that I gues its far bellow 10% these days.

It is also interesting to search Hubble Legacy Archive for "footprints" - but this does not cover the whole sky at once, you need to search for an object and see if there are some footprints in its area on a flashplayer-powered map.

$\endgroup$
  • 1
    $\begingroup$ Imagine if a Hubble-like telescope tried to take deep sky images of the whole sky. It would probably take a millennium. I think astronomers are going to have plenty of work to do for a long time. $\endgroup$ – Jack R. Woods Jul 8 '17 at 14:58

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.