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Finding Cetus

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#1 clastro8*

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Posted 22 October 2020 - 05:37 PM

I wanted to observe the star Mira because I read an article saying it is a variable star over a period of 332 days and becoming its brightest this October at magnitude 2.  Its dimmest is magnitude 10.

 

The constellation pictures a sea monster and, reportedly, the head of the monster is composed of 5 stars in the form of a pentagon.  

 

I'm new at this and after consulting charts, etc, it seemed to be fairly easy to begin observing around Taurus and work my way up to Mars's position looking somewhere in the expanse for a pentagon shape that I would readily recognize.

 

At magnitude 2, Mira should be I think visible to the naked eye but apparently my weaker eyesight combined with light-polluted skies, not to mention not knowing exactly what I was looking for, I confess I didn't see much other than Alderbaran and Mars even on clear nights.

 

Using my 15x70 binos I definitely enjoyed Taurus and Perseus and their surroundings, but just couldn't find a pentagon, no way.   The nearest I could observe to a 5-sided figure was a 4-sided figure which I surmised was probably it but just doesn't qualify as a pentagon.

 

And eventually it dawned on me, suppose the 5th star is very dim and just not visible even to 15x70's, that would be a pentagon, in effect, and that would be head of the constellation I am looking for.

 

I went back to the charts to learn the magnitudes of the stars in the object and, sure enough, the dimmest is magnitude 4.6 and, surprise to me, my binoculars just don't see it readily.

 

So, filling in the blank star, I now observe Cetus and Mira (now the brightest in the constellation), and feel like I've learned a lot by this experience.

 

And had a 'whale' of a good time!


Edited by clastro8*, 22 October 2020 - 07:09 PM.

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#2 Jim T

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Posted 22 October 2020 - 05:52 PM

Most of the stars in "the Celestial Sea" are dim, and that includes Cetus as well as the other fishy constellations.  They need to be viewed from a dark-sky site if at all possible.  Just below Diphda (Deneb Kaitos, or beta Ceti) is a magnificent galaxy visible in binos (NGC 253 - the Sculptor galaxy).



#3 clastro8*

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Posted 24 October 2020 - 12:59 PM

Thanks for the suggestion about NGC 253 but checking it out on line, I see it is magnitude 8, so if my 15 x 70's can't see magnitude 4.6, they won't see it.

 

BTW, freestarcharts.com says there are 6 stars in the pentagon shape mentioned earlier, the magnitudes are 2.5, 3.6, 2 @ 4.3, 4.7 and 4.9.  So, if my 15x70's see only 4 stars, the two missing would be the 4.7 and 4.9.  I also have some 10x50 binos, they only see 3 stars from the pentagon, so they must miss one of the 4.3's.

 

For some reason, I find it interesting reflecting on the fact that the ancients saw 6 stars in the form of a pentagon shape, but today without any hardware I see perhaps none of those stars, but with my best equipment, I can see 4 of them.

 

What is a good way to try to see the other 2 stars, obtain a pair of 20x80's, buy a small telescope, merely wait for cold winter weather when the air will be clearer? Would a large telescope, say 6 or 8 inch, pose the opposite problem, ie reveal so many stars in the area, it would be difficult to know which ones are the 2 I want to see?


Edited by clastro8*, 24 October 2020 - 01:00 PM.


#4 Mark9473

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Posted 24 October 2020 - 01:05 PM

There is just no way a 15x70 can fail to show a 4.6 magnitude star, unless it's cloudy or daylight. I think you were looking in the wrong spot.
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#5 clastro8*

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Posted 24 October 2020 - 05:55 PM

Could be, as I said I am new at this.   But I looked in the right place, as I explained above, and I also used Stellarium Web (I am new at that too), and tried over several nights with clear skies.

 

I just read a piece on the Bortle scale and entered my location in the input section, the result was showing red all around me, I think that is a bad sign for good star observing.  But I noticed there is some green a half hour away from me or so, I guess that could give me another option for seeing those two stars.


Edited by clastro8*, 24 October 2020 - 05:56 PM.


#6 sonny.barile

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Posted 24 October 2020 - 06:13 PM

At mag 2 you should be seeing it naked eye....you are looking in the wrong place. Use SkySafari or if you do don’t have that download the free Skyportal app fromCelestron to help locate it. 


Edited by sonny.barile, 24 October 2020 - 06:14 PM.


#7 PEterW

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Posted 25 October 2020 - 03:26 AM

Naked eye to 15x is a big jump. I have several lower power pairs, eg 2x, 7x, 10x. If you move up through them each shows more and so homing in is easier. I’m not suggesting buying lots of pairs, but something lower power, maybe 7x can help, also know the width of your field of view to help give you some scale, I’ve been tricked at times even in areas I thought I knew. Having an easy to find starting point (Mars) will help. Maybe try from another starting location and see if you get to the same location.

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#8 Tony Flanders

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Posted 25 October 2020 - 06:50 AM

There is just no way a 15x70 can fail to show a 4.6 magnitude star, unless it's cloudy or daylight. I think you were looking in the wrong spot.

I agree. 70-mm binoculars gather 100 times as much light as your unaided eyes -- that's 5 magnitudes. So a 4.6-magnitude star through 70-mm binoculars should look brighter than Vega does to your unaided eyes.

 

For what it's worth, I have never found the head of Cetus to be an especially eye-catching pattern -- nowhere near as neat and tidy as those connect-the-dots figures on the map hint that it ought to be.

 

And as others have said, 15x70 binoculars are not especially good tools for viewing the constellations, due to their relatively narrow field of view. They can barely fit any two stars out of the 5 together in a single field of view, which makes it exceedingly hard to figure out what's going on.

 

You would do much better with conventional binoculars in the 7x to 10x range. But like most major constellation features, the head of Cetus is too big to fit fully in the field of view of any conventional binoculars.



#9 clastro8*

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Posted 25 October 2020 - 04:52 PM

Thanks for your helpful comments.

 

To prove your point, I looked up the magnitudes of the Pleiades, which range from 3 to 6.  My 15x70 do a great view of that group, so I get the point the binos should do 4.7 magnitude with no problem.

 

Incidentally, to my unaided eye, I can't see individual stars of the Pleiades, which together appear as a gauzy fairly faint patch.  I do see unaided Polaris, magnitude 2, and I think also Mira, which is now about the same magnitude, but neither dazzles the eye.

 

I wanted to locate Mira using the star hopping technique in order to get the practice but also because when it dims down in the following weeks and months, it will be in a different position in the sky and I wanted to have a map, so to speak, to get to it from any position.

 

On this link (https://freestarchar...a_Peak_2011.pdf) it appears that the head of Cetus resembles a pentagon whose longest dimension is maybe 9 deg across and next longest is 6 degrees.  I have an old pair of 8x30 with fov of 393 feet at 1000 yards.  As I understand it, dividing 393 by 52.5 results in a fov of 7.5 degrees, so that should help me approach the scale, as PeterW pointed out.

 

If Tony Flanders could provide a linked discussion relating lens diameter, light gathering power, and magnitude, etc, I would really like to read up on it.  

 

For now, it's back to the drawing board, or should I say 'celestial dome'?, as soon as the rain stops and the clouds move on.


Edited by clastro8*, 25 October 2020 - 05:54 PM.


#10 PEterW

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Posted 26 October 2020 - 04:00 PM

Tried out some new cold weather clothes in the streetlig HR infested urban garden and a mostly full moon. I was using my Nikon 2x54 l; though they suffered from some off axis stray light. The pentagon of Cetus is an odd shape with “bits off it”, the bit that I found easiest was the triangle at the bottom (menkar is the left hand star). Mira was then just a little bit to the right... the only star I could see in the area. Once you think you have found the area, note a few extra stars and go back to confirm with the charts. I initially tried to come down from Mars, but couldn’t see anything (unless I blocked the lights with a tree - I said the light pollution was bad). I saw the triangle, guessed what it was, checked sky safari, was right and then onto Mira. I was surprised that Aries was so high up, I initially thought I was looking at the bottom of urea major. I ended up just looking at the star fields in Cassiopeia , Perseus and cygnus.

Good luck, keep at it.

PEter

#11 clastro8*

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Posted 27 October 2020 - 12:20 PM

There were too many clouds for me to see anything, so I spent some time reflecting on the fact that I thought I needed more magnification for the task at hand when the opposite is true, I needed less.  Thanks for helping me see it.



#12 PEterW

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Posted 27 October 2020 - 01:16 PM

Do tell us when you succeed, w it h light pollution to ere are less stars to confuse you...

Peter

#13 Waddensky

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Posted 27 October 2020 - 01:40 PM

Cetus is a faint constellation and the star hops are not easy over there, not many bright stars to use as a guide. Mira is currently mag 3.5-ish and already dimming (light curve), so the star might not be so prominent as you'd expect. The Moon is nearby too these days.

 

The best place to start may be Mars right now, you can cascade down Mu, Nu, Xi and Alpha Piscium - but they're all 4th or 5th magnitude so also not very eye-catching. Another option is to find the mag 2.5 star Menkar, the second-brightest star in Cetus. Mira is about 10 degrees west of Menkar.



#14 clastro8*

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Posted 30 October 2020 - 01:03 PM

Please explain the direction as 'west of Menkar.' 

 

I'm looking at Stellarium web set to this late this evening with the observer facing east.

 

Doing that, if Menkar is at the center of a clock face, then Mira I think is off to the right, let's say at about 2 oclock on the clock face.  Is it 'ok' to describe the direction this way?

 

If I am facing east and something is in the direction to my right, I would have said it is south of me, ie in the direction of my southern horizon.


Edited by clastro8*, 30 October 2020 - 01:23 PM.


#15 PEterW

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Posted 30 October 2020 - 02:04 PM

I would say left or right as it’s easier to be sure.

PEter

#16 clastro8*

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Posted 30 October 2020 - 06:55 PM

Since I am new in these discussions, I am wondering if there are assumed ways to thinking about directions.  

 

Wadddensky didn't say which direction the observer is facing but the reference to Pisces and cascading down seemed to suggest the observer is facing east.

That puts Mira to the right of Menkar, according to Stellarium.

 

Using the free star charts link I posted above, I see the cascading down stars Waddensky referred to, so I'm thinking using the Greek alphabeted references to the stars and a chart like that one, to the experienced observer, it doesn't matter too much which direction is mentioned or how the diagram is leaning, the experienced observer can find the way to the object.

 

Pretty neat and it seems I have some learning to do.



#17 Mark9473

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Posted 30 October 2020 - 07:03 PM

There are no assumptions at all about the cardinal directions in the sky.

East is where the Sun rises, West is where it sets, remember? Same at night.



#18 clastro8*

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Posted 31 October 2020 - 12:39 AM

Ok, I see what you are saying.

 

Let me ask you this. Stellarium, facing east, showed the Moon high in the sky overhead with Cetus near directly below it.

 

What cardinal direction was Cetus with respect to the Moon?  North, south, east, west?



#19 daniel_h

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Posted 31 October 2020 - 06:11 AM

for me in th sth’ erin hemisphere the moon is directly below cetus - closer to my northern horizon (mars just over from moon), therefore  the moon is Nth of cetus, cetus sth of the moon  above it - but in the direction of Sth



#20 Mark9473

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Posted 31 October 2020 - 05:15 PM

Let me ask you this. Stellarium, facing east, showed the Moon high in the sky overhead with Cetus near directly below it.

 

What cardinal direction was Cetus with respect to the Moon?  North, south, east, west?

That's a trick question.

The Moon would be high in the sky in the South, not the East.

Anyway, to answer your question, I need a location and a time.



#21 clastro8*

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Posted 31 October 2020 - 06:11 PM

No, not intended to be a trick question. 

 

I will describe a generic situation.

 

You are located in the Northern Hemisphere and are facing east after dark.

 

Celestial Object A has risen in the east and is now high in the eastern sky.

 

Celestial Object B has risen a bit later, it is also now high in the eastern sky but a bit lower than Object A.

 

With respect to Object A, what direction (north, south, east, west) is Object B?

 

Note, if you were giving a lecture to your astronomy club members using one of those laser lights to indicate the relative current location of the two objects, you would first point it to Object A and then point downward until pointing at Object B.

 

 



#22 KI5CAW

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Posted 31 October 2020 - 06:32 PM

I find the tail of Cetus to be a compact and distinctive pattern. From there you can work toward the head. And NGC 253 is spectacular, even in 15X70s.



#23 Mark9473

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Posted 31 October 2020 - 06:35 PM

Celestial Object A has risen in the east and is now high in the eastern sky.

 

Celestial Object B has risen a bit later, it is also now high in the eastern sky but a bit lower than Object A.

 

With respect to Object A, what direction (north, south, east, west) is Object B?

Object B is due East of Object A.

 

Are you familiar with the celestial coordinate system? Declination and right ascension?



#24 clastro8*

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Posted 31 October 2020 - 07:53 PM

Yes.

 

If B is due East of A, what is the direction of A with respect to B?



#25 clastro8*

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Posted 31 October 2020 - 09:14 PM

Actually, I didn't realize the RA/Dec system was being used here.

 

The answer to the direction of A with respect to B is ... west.

 

But it is overhead and, to some extent, that is counter-intuitive to the fact that the sun sets in the west, as you said.  I say this because, if I am facing east, then west is to the back of me.  So, how is it that if west is to the back of me, that something I'm seeing facing east is west of something else?  But of course, the 'assumption' is that the sky above is in effect a dome over the earth where I am standing.  So celestial objects rise in the east moving along the inside of the dome, pass over over the observer (or reach their highest point due north or south of the observer) then set in the west.

 

Of course, the sun actually rises in the east and sets in the west only on the equinoxes, ie twice per year.  On the other days, for example, in the western hemisphere, it rises either north of due east (spring, summer) or south of due east (autumn, winter).   

 

One other point I would make is that the article I read on Mira, said to find it starting at Taurus and moving southwest, which is not, as far as I know, an RA/Dec description.


Edited by clastro8*, 31 October 2020 - 10:13 PM.



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