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Ever seen a supernova? Give this one a go.

mdstuart

By mdstuart
in The Astro Lounge

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perrin6

perrin6

Posted
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could it be that the stars are not magnified (as I understand it you can never magnify a star (being a point of light) as it's too far away) and therefore the light is not spread over a larger area so remains as bright as before?

Sorry Shane - I missed this post of yours. I am basing my statement partly on experience but also from using an online 'limiting magnitude calculator'. I was just experimenting plugging in diff. magnifications for a 12 inch and the magnitude of faintest visible stars gets gradually better up to 1200X but above that gets worse. I don't know whether that is what actually happens. In response to your query; the star in an optical instrument appears as an 'airy disc' which is a tiny disc of light surrounded by diffraction rings. The size is defined by the aperture and the brighter the star is, the more concentric rings are visible which makes for a larger apparent image. The central disc also varies slightly with brightness.

I don't know what your highest magnification is but with my Uwan 4mm in my 13 inch (X443) as tiny discs with rings when the air is steady. I also see the same with this eyepiece in the Zenithstar 66 (X97) although the image is much steadier and tend to have less rings due to there being no central obstruction and because it has more accurate optics. I use the 4mm to view sub-arcsecond doubles eg Hip 13892 .6" sep. (nr epsilon Arietis) & hip 14481 Arietis .5"

BTW I have been reading 'Age of Wonder' which has a lot of fascinating stuff on William Herschel who apparently used magnifications of up to 6000X !;)

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Hypernova

Hypernova

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I tried myself but could not find the galaxy! my problem is that the stars from Polaris / Ursa minor are just about half visible - sometimes yes sometimes no. From Mark's comments I was maybe starting from the wrong spot.

that said, the LP is worst where UMa is although I did see M97 and NGC2841 last night for the first time.

I have managed to find the stars from Polaris fairly easily using the 9x50 finder that came with the 'scope. The Telrad has its times but looking for fainter guide stars in sparse bit of sky isn't one of them. The two 7th mag stars that are either side of the galaxy are easy to see in the finder and I just point it between the two.

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Moonshane

Moonshane

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Oh! - the problems with telrad/RDF etc (I think that's what you use isn't it) - no prob with my handy-dandy homemade 8 X 40 finder- 7 degree field and 8th mag stars easily visible ! (If only the clouds would buzz off for a few mins:icon_confused:)

cheers Alan

I do also use a 9x50 finder so there's no excuses - I obviously need more practice! ;) I need to prepare better I think I literally picked up a map and tried to find it at the end of the session - I'll plan better next time and have a go.

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Moonshane

Moonshane

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Sorry Shane - I missed this post of yours. I am basing my statement partly on experience but also from using an online 'limiting magnitude calculator'. I was just experimenting plugging in diff. magnifications for a 12 inch and the magnitude of faintest visible stars gets gradually better up to 1200X but above that gets worse. I don't know whether that is what actually happens. In response to your query; the star in an optical instrument appears as an 'airy disc' which is a tiny disc of light surrounded by diffraction rings. The size is defined by the aperture and the brighter the star is, the more concentric rings are visible which makes for a larger apparent image. The central disc also varies slightly with brightness.

I don't know what your highest magnification is but with my Uwan 4mm in my 13 inch (X443) as tiny discs with rings when the air is steady. I also see the same with this eyepiece in the Zenithstar 66 (X97) although the image is much steadier and tend to have less rings due to there being no central obstruction and because it has more accurate optics. I use the 4mm to view sub-arcsecond doubles eg Hip 13892 .6" sep. (nr epsilon Arietis) & hip 14481 Arietis .5"

BTW I have been reading 'Age of Wonder' which has a lot of fascinating stuff on William Herschel who apparently used magnifications of up to 6000X !;)

cheers Alan, this is all great stuff for me. I am still a genuine novice (despite my kitlist) and welcome any guidance like this. 6000x :p indeed!

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Moonshane

Moonshane

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I have managed to find the stars from Polaris fairly easily using the 9x50 finder that came with the 'scope. The Telrad has its times but looking for fainter guide stars in sparse bit of sky isn't one of them. The two 7th mag stars that are either side of the galaxy are easy to see in the finder and I just point it between the two.

cheers Tom

I think my problem is just inexperience on this sort of thing. I know most of the main constellations well enough now but as you say bits of sky which hold few main stars are still very tricky for me. I'll have another go at this next time and hopefully it will still be around. How long will this last on average?

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perrin6

perrin6

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cheers Tom

I think my problem is just inexperience on this sort of thing. I know most of the main constellations well enough now but as you say bits of sky which hold few main stars are still very tricky for me. I'll have another go at this next time and hopefully it will still be around. How long will this last on average?

My starhopping routine:-

(I dont expect you to read this as it is boring! and needs illustrations really, but it's handy practise for me to summarize the routine !;))

Basically the key info to get from maps are; what the view will look like in the finder and the low power eyepiece ie. Asterisms - simple shapes and orientation of the view because it might be eg 45 degrees from what it looked like on the map. Plus magnitudes of stars to hop from:-

1) Look on map for bright (>3rd mag) star nearest to object (obj)

2) Look for notable asterism that can be seen in finderscope between the bright star and object. This could be a trepezium but is usually a triangle (There are LOTS of triangles up there.

3) Find the bright star, then the asterism in finder and position scope on the star (of the asterism) that is nearest the obj. Look for this star in your low power view

4) Check map to see what fainter asterisms (that can be seen in the low power view) are between the star you are now centred on, and the obj.

5) Looking through the low power eyepiece, sweep the scope from the star in the direction the fainter asterism is and use that to locate obj position.

The tricks are-

When looking at the map try to imagine what the asterism will look like in the scope ie recall how wide the field of view is of your finder and your low power eyepiece. Orientation can be confusing so note what the asterism looks like with respect to East & West. Then when you look through the eyepiece you can get your bearings by watching which way the stars move because they always go West (young man).

Check magnitudes of stars you hop from so you know what they'll look like in the scope.

If you cant find an asterism, use two stars as pointers and note the rough bearing the object is from the line drawn between the two stars and how many line-distances it is.

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perrin6

perrin6

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I just saw it ! it's quite bright, possibly brighter than 13th mag, considerably brighter than 2 nearby stars of 14th mag, transparency looks quite good at present. I got the impression the supernova was bluish but this may be anomalous.

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mdstuart

mdstuart

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Alan

Good report. It is a special sight. Blue? Not sure on that one, my eyes only see colour in the brighter objects..

As I understand it this is a binary and it explodes when one star reaches a precise size and hence the explosion is always the same brightness. Thus the brighter the SN the closer it is!

Mark

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russ

russ

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I tried and i failed :)

Simply impossible from the backgarden. Can only see Polaris....just. No other stars visible for reference. Tried making shapes in the sky to workout where 2655 was but no joy. Limiting magnitude was +2.

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Moonshane

Moonshane

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hi Russ

I struggled a bit too the other night but found the galaxy at least last night with the following method (just before the clouds rolled in so no SN). I founf that in my 50mm finder the right area was relatively easy to locate. From memory, get Polaris in the finder and slew dead right. You'll see the pretty bright mag 4 star and then two fainter stars (maybe mag 6) off to the right of the mag 4. Just up and to the right of the pair of mag 6 is another of about the same magnitude and just above and left of these are two mag 7 stars one above the other. NGC2655 is just to the left of this pair and roughly half way between them.

Not sure if the attached helps?

ngc2655.pdf

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russ

russ

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Thanks Shane, that's a huge help. That description of how to find it will be great and the PDF as well. Will give that a try when we get the next clear night. Just not too sure when that will be.

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Moonshane

Moonshane

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no worries mate. the conditions were deteriorating when I looked but the galaxy was not visible in my 35mm Pan but quite obvious in the 13mm Ethos so about 120x max seems to be required to see it. hope you (we!) get it next time out. thankfully it is literally a right slew from Polaris to the mag 4 star so helps in the finder view.

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Moonshane

Moonshane

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yippee! just spotted it, helped by the excellent sketch here http://stargazerslounge.com/imaging-sketches-unconventional/127916-sn2011b-supernova-ngc-2655-a.html

this is a completely accurate representation of what I just saw.

it's not a jawdropper but very interesting, especially once you realise what's going on.

sitting here with my right eye shut (does this work??) to maintain my night vision to go out again shortly. my problem is, I'm putting the tea on now!

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Moonshane

Moonshane

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I've created a finder chart to find the galaxy. Polaris is the bright star on the right hand side of the chart.

The image is inverted ie. North at bottom, west at right.

spot on Alan, the orange blob (galaxy) is between two stars of similar magnitude.

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spaceboy

spaceboy

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yippee! just spotted it, helped by the excellent sketch here http://stargazerslounge.com/imaging-sketches-unconventional/127916-sn2011b-supernova-ngc-2655-a.html

this is a completely accurate representation of what I just saw.

it's not a jawdropper but very interesting, especially once you realise what's going on.

sitting here with my right eye shut (does this work??) to maintain my night vision to go out again shortly. my problem is, I'm putting the tea on now!

Only looking like a speck of light I was a bit reluctant to say I had seen it for sure but seeing the sketch it is an excellent representation of what I saw. I admit I cheated with the help of GOTO to find NGC2655 but coaxing the galaxy and SN out with averted vision was all my doing :) TBH it was good to see NGC2655 and to think what was going on at the little spot of light next to it was the icing on the cake.

I am only under 3-3.5 Mag stars at the best of times so IMHO anyone with a GT mount will have this nailed even with just an 8" and some dark adapted eyes and averted vision.

Thanks for the heads up on this one Mark :)

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