# Astronomers and stargazers, amateurs and pros, is the arrow in this image pointing to Perseus? **URL:** \ **Category:** Factual Questions\ **Created:** [February 15, 2018, 12:11am UTC](https://boards.straightdope.com/t/astronomers-and-stargazers-amateurs-and-pros-is-the-arrow-in-this-image-pointing-to-perseus/808849 "2018-02-15T00:11:48Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Spectre\_of\_Pithecanthropus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spectre_of_pithecanthropus/32/12343_2.png) [@Spectre\_of\_Pithecanthropus](https://boards.straightdope.com/u/Spectre_of_Pithecanthropus)\ **Post date:** [February 15, 2018, 12:11am UTC](https://boards.straightdope.com/t/astronomers-and-stargazers-amateurs-and-pros-is-the-arrow-in-this-image-pointing-to-perseus/808849/1 "2018-02-15T00:11:48Z")
As a follow on to my [recent post](https://boards.straightdope.com/sdmb/showthread.php?t=848826) about star photography, I now have a question with very specific answers, or as many answers as there are stars visible in the linked photo. As I said in the other thread, I made it out to a dark sky location near home, and among the photos I got was this one: [Link](https://www.flickr.com/photos/78538399@N00/40225527862/sizes/c/) (Unfortunately, the only simple way to eliminate the noise was to eliminate the colors, so all the stars are white here. I don’t know any complex or sophisticated ways to eliminate noise yet.) Anyway, with all that out of the way, is the arrow pointing to Perseus, specifically to the stars traditionally thought to represent his head? I believe it is, but I can’t be sure since there seem to be no other potential “landmarks” in the photo that I can use. It’s not like it includes Orion and then you can immediately map everything else based on that. I think my problem may be that I’m not used to dark skies yet, and it’s easy to be confused by all those fifth and sixth magnitude stars. Naturally I’ve tried using Celestia and Stellarium, but even with those apps it’s too easy to get lost unless there’s some familiar constellation in the picture. I’m fairly sure I was pointing the camera towards the circumpolar region, if only because the stars there tend to be on the faint side. Who can see Draco or Camelopardalis without getting away from the city? I doubt if even **Giraffe** can do it. I took the photo at around 9:30 PM on Februrary 8th, but unfortunately I don’t remember the altitude and azimuth. I didn’t have my tripod with me\*\*, so I had to make do by resting the camera against my windshields, or on the roof of my car. ---
**Author:** ![AHunter3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ahunter3/32/368_2.png) [@AHunter3](https://boards.straightdope.com/u/AHunter3)\ **Post date:** [February 15, 2018, 12:43am UTC](https://boards.straightdope.com/t/astronomers-and-stargazers-amateurs-and-pros-is-the-arrow-in-this-image-pointing-to-perseus/808849/2 "2018-02-15T00:43:36Z")
I don’t think so, mostly because I’m pretty sure the stars in the upper right of your photo are Scorpius. And Scorpius and Perseus aren’t anywhere close to each other. ---
**Author:** ![Spectre\_of\_Pithecanthropus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spectre_of_pithecanthropus/32/12343_2.png) [@Spectre\_of\_Pithecanthropus](https://boards.straightdope.com/u/Spectre_of_Pithecanthropus)\ **Post date:** [February 15, 2018, 4:04am UTC](https://boards.straightdope.com/t/astronomers-and-stargazers-amateurs-and-pros-is-the-arrow-in-this-image-pointing-to-perseus/808849/3 "2018-02-15T04:04:49Z")
> [@AHunter3](#): > > I don’t think so, mostly because I’m pretty sure the stars in the upper right of your photo are Scorpius. And Scorpius and Perseus aren’t anywhere close to each other. I see what you mean; it does look like the end of the tail, but it isn’t. I took the photo around 9:45PM when Scorpius is well below the horizon at this time of year. Sent from my SM-G950U using Tapatalk ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [February 15, 2018, 4:35am UTC](https://boards.straightdope.com/t/astronomers-and-stargazers-amateurs-and-pros-is-the-arrow-in-this-image-pointing-to-perseus/808849/4 "2018-02-15T04:35:57Z")
I don’t think so, because if that were Perseus’s head the easily-recognizable “Big W” of Casseopeia should also be visible. Also the bright star Algol in Perseus should be obvious. ---
**Author:** ![blue\_infinity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_infinity/32/2817_2.png) [@blue\_infinity](https://boards.straightdope.com/u/blue_infinity)\ **Post date:** [February 15, 2018, 5:15am UTC](https://boards.straightdope.com/t/astronomers-and-stargazers-amateurs-and-pros-is-the-arrow-in-this-image-pointing-to-perseus/808849/5 "2018-02-15T05:15:54Z")
That is Perseus, and your arrow is pointing to alpha Persei, which is more like his ribcage. His head is to the south-east in your pic, around the point of that right-hand triangle. [Imgur: The magic of the Internet](https://imgur.com/a/yrU2O) - pic of constellation rotated to match your photo ---
**Author:** ![Spectre\_of\_Pithecanthropus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spectre_of_pithecanthropus/32/12343_2.png) [@Spectre\_of\_Pithecanthropus](https://boards.straightdope.com/u/Spectre_of_Pithecanthropus)\ **Post date:** [February 15, 2018, 8:13am UTC](https://boards.straightdope.com/t/astronomers-and-stargazers-amateurs-and-pros-is-the-arrow-in-this-image-pointing-to-perseus/808849/6 "2018-02-15T08:13:18Z")
> [@blue\_infinity](#): > > That is Perseus, and your arrow is pointing to alpha Persei, which is more like his ribcage. > > His head is to the south-east in your pic, around the point of that right-hand triangle. > > [Imgur: The magic of the Internet](https://imgur.com/a/yrU2O) - pic of constellation rotated to match your photo Thanks for figuring this out! I see now that parts of both Dippers, as well as Polaris, are included in my original photo, but I guess I was just lost among the stars. I found an excellent website that can analyze uploaded photos of the night sky and identify the stars they contain: [http://nova.astrometry.net/](http://nova.astrometry.net/) However, it’s limited in terms of the “amount” of picture contents it can handle. It couldn’t handle the photo I linked to here, but when I tried it on a couple of small sections, it worked. This failure message on larger files indicates that an intended limit on CPU time has been reached. In fact, the site generally seems to have a very retro look-and-feel. Here’s a crop including the stars I was asking about: [Link](http://nova.astrometry.net/user_images/1981673#annotated) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 15, 2018, 1:41pm UTC](https://boards.straightdope.com/t/astronomers-and-stargazers-amateurs-and-pros-is-the-arrow-in-this-image-pointing-to-perseus/808849/7 "2018-02-15T13:41:47Z")
That’s a poor design on their part, then: If their algorithm can handle the cropped picture but not the whole one, then it should crop it on its own. ---
**Author:** ![Spectre\_of\_Pithecanthropus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spectre_of_pithecanthropus/32/12343_2.png) [@Spectre\_of\_Pithecanthropus](https://boards.straightdope.com/u/Spectre_of_Pithecanthropus)\ **Post date:** [February 16, 2018, 5:21am UTC](https://boards.straightdope.com/t/astronomers-and-stargazers-amateurs-and-pros-is-the-arrow-in-this-image-pointing-to-perseus/808849/8 "2018-02-16T05:21:47Z")
But then how would their system decide where to crop the image? I’d much rather have it error out the way it does.