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N3ptune

Faint star hunting

41 posts in this topic

Posted (edited)

HQS9M2a.jpg?1

Hello again!

I have the AstroLeague Carbon star list here, 100 stars to locate and log and I wonder about the magnitudes of stars, most of them are variable between 6 and 13.5 magnitude and can be located with 8" aperture. I know the factors of: light pollution, transparency and seeing has well has the size of the telescope and probably collimation should dictate if I can see a magnitude 10, 11, 12 or even 13. 

My question is: With a similar aperture instrument has mine 8", in a suburban area with high level of light pollution, what is usually your breaking point? the faintest magnitude (star only) you willing to hunt on average? And at what point will you decide to drive to a dark spot.

Thanks.

Edited by N3ptune

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I have an 8" too, my NELM is about 4.5 and I reckon i can see down to 13 for stars.

not sure I'd drive to a dark site for some stars though. Maybe pick off a few of the faint ones when you are doing a dark site galaxy hunt :)

 

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I live in the suburbs of a city and from my back garden with my 8" reflector I can usually see down to magnitude 10 on a normal night and magnitude 11 on a good night, with suggestions of magnitude 12 stars on a good night using averted vision. I wouldn't drive to a dark sky site to see a star. At least I haven't come across one yet I'm willing to do that for. However, to see most nebulae and galaxies I have to get out of the city and get to a dark sky site for clear views.

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You might find this site useful

http://www.cruxis.com/scope/limitingmagnitude.htm

I observe under similar skies. It's not usually stars that I'm bothered about, but perhaps planetary moons, or say the supernova in M82 a while back or the asteroid which passed close by recently. Those are more likely to be the objects I'm interested in but if you are looking for Carbon stars, understanding their visibility will be very useful

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Posted (edited)

Thanks it gives me a better idea, I used the tool and I get results between 11.8 and 12.8, it's better then I thought. I would probably not drive to a dark spot either for stars only, but i could spend a block of time to search for a few faint carbon stars at a darker spot, could be interesting.

You guys are in the 11 to 13 in optimal conditions it's great, more then I thought again.

 

Edited by N3ptune

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6 minutes ago, N3ptune said:

Thanks it gives me a better idea, I used the tool and I get results between 11.8 and 12.8, it's better then I thought. I would probably not drive to a dark spot either for stars only, but i could spend a bloc of time to search for a few faint carbon stars at a darker spot, could be interesting.

You guys are in the 11 to 13 in optimal conditions it's great, more then I thought again.

 

Don't forget that with stars, adding more power generally allows you to see deeper because the sky background darkens but the star does not, being a point source. I'm sure it is not quite that simple but it is good enough for me :)

My biggest aperture currently is a C925 so I will have a play with than when we get darkness back and see how close to the theory it gets. Transparency and also seeing conditions are likely to play a part too.

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I noticed that too, more power will reveal faint stars especially using high power on faint star clusters. I'll have to locate the sector of the faint carbon star then raise the power until can spot it. (I used to search at low power only actually, maybe that's the reason for my low to moderate success yet)

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I've managed to get down to around mag 14 from my back garden with my 12" dob. I do find high magnifications help pick out the faintest point sources.

 

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@john magnitude 14 that's really faint! 12 inches seems more then capable for faint objects. That's 113 in² of mirror against 50 in² for a 8" , more then double the area. What is the condition of the sky pollution from your back garden?

Question: Stellarium is telling me the following information about R Lep, it's a variable brightness star and the magnitude (right now) is 8.05, is this reliable information? I guess the software will update the magnitude of this specific star following a time period and or other factors? The magnitude range is 5.50 ÷ 11.70 .. Ignoring the "÷" does it means it's between 5.50 and 11.70 variable, simply?

vHSZxIC.png?1

 

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Waoow! Lucky evening! While getting the trash out I noticed a beautiful sky with no moon and took the reflector out for a carbon star hunt. It was a short observation, about 1 hour but a memorable one, everything went well.

My targets were from Astro League's list:

VY Ursa Major: 5.95 magnitude, was an easy target to locate, an orange star with hints of red in the spikes, found at 40x

RY Dra: 6.6 Magnitude, easy to find again, a bit harder then VY, deep red color pulsation.

T Dra: 10 magnitude, that one I am proud ((: it took maybe 10 minutes to locate because it's really faint and inside a field of stars just outside the head of Draco. I looked at it maybe 10 minutes at 40x power, this star is a pulsating red laser pointer! Finally I examined the object with 4.7mm EP, 212x power now the red color pulsation is even more pronounced. Seeing was quite good, no scintillations, another rare event, star observation at 212x. 

I know now my scope can show me 10 magnitude stars (information from Sellarium) from home with not much difficulties, which is a very good news.

:icon_biggrin: I am going to bed happy.

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Posted (edited)

7 hours ago, N3ptune said:

@john magnitude 14 that's really faint! 12 inches seems more then capable for faint objects. That's 113 in² of mirror against 50 in² for a 8" , more then double the area. What is the condition of the sky pollution from your back garden?...

 

 

On a good night I can see down to around mag 5.5 naked eye with quite a band of Milky Way through Cygnus and beyond. M31 is just about a naked eye object when it's reasonably high in the sky. My limits are not as good near the horizons though due to light pollution from narby towns and cities.

Find the Ring Nebula (M57) and see if you can see the faint star next to it (see pic). This is mag 13 I believe:

 

Ring-Nebula-Telescope.jpg

Edited by John

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1 hour ago, John said:

On a good night I can see down to around mag 5.5 naked eye with quite a band of Milky Way through Cygnus and beyond. M31 is just about a naked eye object when it's reasonably high in the sky. My limits are not as good near the horizons though due to light pollution from narby towns and cities.

Find the Ring Nebula (M57) and see if you can see the faint star next to it (see pic). This is mag 13 I believe:

 

Ring-Nebula-Telescope.jpg

SkySafari gives for this star (GSC 2642-0433) a magnitude of 14.4, probably  too faint for an 8" under most observing conditions.

Stephan

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4 hours ago, Nyctimene said:

SkySafari gives for this star (GSC 2642-0433) a magnitude of 14.4, probably  too faint for an 8" under most observing conditions.

Stephan

Stellarium gives 12.95  ...

 

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Posted (edited)

4 hours ago, Nyctimene said:

SkySafari gives for this star (GSC 2642-0433) a magnitude of 14.4, probably  too faint for an 8" under most observing conditions.

Stephan

I have seen this star with my ED120 and 130mm refractors. A recently posted chart of the surrounding stars and their brightnesses:

 

 

m57stars.png

Edited by John
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1 hour ago, John said:

I have seen this star with my ED120 and 130mm refractors. A recently posted chart of the surrounding stars and their brightnesses:

 

 

m57stars.png

Very interesting and excellent deep sky map, thanks for posting, John! Can you link the source, please?

Of course, a 13 mag star can be made out with a good 5" frac. I'll give this star a try with my 5,1" and 8" dobs.

No explanation for the remarkably different magnitude figures. Moreover, I've just noticed, that SkySafari 5 Pro shows stars just down to 15 mag (when set to  faintest star mag 19.0) at the moment - has anybody else this problem? Playing with the Setting modes does not change anything up to now.

 

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To be honest Stephan, I don't know the source. I took the chart from this thread by mikeDnight because I thought it looked useful !:

 

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On 2017-07-17 at 08:23, John said:

I've managed to get down to around mag 14 from my back garden with my 12" dob. I do find high magnifications help pick out the faintest point sources.

 

 

2 hours ago, John said:

I have seen this star with my ED120 and 130mm refractors. A recently posted chart of the surrounding stars and their brightnesses:

 

 

m57stars.png

John do you find a limit on how high mag you can go on stars in general? This is a great map- are there other maps with easy to find fainter stars such as this? I'm wanting to practise this faint star stuff hoping to stand a better chance on the 2 chosen lensed objects...

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Posted (edited)

27 minutes ago, jetstream said:

 

John do you find a limit on how high mag you can go on stars in general? This is a great map- are there other maps with easy to find fainter stars such as this? I'm wanting to practise this faint star stuff hoping to stand a better chance on the 2 chosen lensed objects...

Hi Gerry,

What I'm generally trying to do is to spot something like a supernova, faint planetary moon, quasar or planetary nebula central star. The highest I've used is 795x (12" dob with 2-4mm Nagler zoom) but the tiny exit pupil, miniscule patch of sky and constant nudging tends to make this difficult to use for any length of time so I'd say that 350x - 500x is a more useful for the purposes of "going deep". 

I found 450x picked out a couple of Uranian moons for example. Uranus itself was a bit overpowered but the moons did "pop" on and off in the right places.

Neptune's moon Triton is another where high power works well.

I think I've caught the central star of M57 a couple of times using this technique as well. It's fairly surreal to have the planetary nebula occupying virtually the whole field of view but fun too :icon_biggrin:

The 3.5mm pentax XW is a good eyepiece for this sort of thing - 454x with my dob, decent wide field, sharp and good transmission as well.

Edited by John
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I must try what I have for eyepieces - most likely orthos- or the Docter barlowed and see what I can find. From what I hear the XW's are the best in the league and a 5mm or 7mm might put me in the strike zone , I'll try anything to see these two objects, lets hope I don't have to climb a mountain with many gallons of oxygen on my back :icon_biggrin:

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Really interesting this topic, thanks John for sharing the ring nebula image with it's surrounding stars. On my next observation I'll sketch the entire FOV, picking the faintest stars possible. Then I will compare with your image and Stellatium.

Great exercise!

Hello Gerry!

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Naked eye Messiers I've seen from home:

M31 (easy)

M13 (needs to be high up, but obvious when it is)

M35

M39

M34 (just)

Never managed M33 but keep trying. In 25x70 binoculars I've got M74, M97, M109, M76 and the very low M54 and M55 (M108 continues to elude me as do those two at the bottom of Hydra, M68 and 83 I think).

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On 7/17/2017 at 05:34, Stu said:

You might find this site useful

http://www.cruxis.com/scope/limitingmagnitude.htm

I observe under similar skies. It's not usually stars that I'm bothered about, but perhaps planetary moons, or say the supernova in M82 a while back or the asteroid which passed close by recently. Those are more likely to be the objects I'm interested in but if you are looking for Carbon stars, understanding their visibility will be very useful

Stu:

You may find this article from Sky & Telescope Magazine (USA) of interest regards asteroids & moons:

Amateur Observers Find an Asteroid’s Moon.pdf

I just got this today in my email from them, so - good timing!

From the 'Miles-O's-Files'-

Dave

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Thanks Dave, I'll have a read later :) 

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23 hours ago, Nyctimene said:

Of course, a 13 mag star can be made out with a good 5" frac. I'll give this star a try with my 5,1" and 8" dobs.

This morning from 02h - 03h CEST I was able to make out this star near M 57 under sub-average conditions (NELM 5,4 mag, SQM-L 20,92, Milky Way washed out, partially thin haze). With the 8" f/4 Hofheim traveldob, using 100x mag, the star could be held with averted vision almost constantly, with direct vision about 20-30% of the observing time. The star was in reach even for the 5,1" Heritage, at 80X-100x, but only with averted vision for guessed 20% of the observing time. So definitely about 13 mag brightness.

Stephan

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Posted (edited)

11 hours ago, Nyctimene said:

This morning from 02h - 03h CEST I was able to make out this star near M 57 under sub-average conditions (NELM 5,4 mag, SQM-L 20,92, Milky Way washed out, partially thin haze). With the 8" f/4 Hofheim traveldob, using 100x mag, the star could be held with averted vision almost constantly, with direct vision about 20-30% of the observing time. The star was in reach even for the 5,1" Heritage, at 80X-100x, but only with averted vision for guessed 20% of the observing time. So definitely about 13 mag brightness.

Stephan

Interesting report thanks for sharing it.

Has for me, my first stem was a semi-failure, this is my sketch of the stars surrounding the Ring Nebula, but my stars aren't at the same place has the existing recordings. Although, it could be a code 18.. these stars from my sketch were so faint, I could see them only with averted vision, invisible most of the time and maybe like you Nyctimene, visible 20% of the time. I used 80x magnification to produce my sketch xcel lx 25mm 60d AFOV.  Still an interesting exercise.

Update #3 - After a few rotation it makes more sense, some faint stars match the recordings. I don't have time to study the images further.. 

E4ZXFV3.png?1

 

Edited by N3ptune
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