Can't seem to see the nebula

bodoh · Post by **bodoh** » Tue Jul 13, 2004 4:25 pm

Skies nice and clear, so decided to do some work on Sagi (since it was nearer the zenith so less Light pollution. Started on the teapot, went to the top, moved to the star above that, found the 2 open clusters (M24 and something else) just below the omega nebula (M17 I think) but couldn't see the nebula, although I was pretty sure I was in the right place.

Is it possible to see the nebula with the ST80mm, do I need to get a LPR filter, what type is best?

The other thing is that as I move around the sky with the scope, after a few hours I get carsick.... is this normal?

Old birds please, need your advice...

gwenyi · Post by **gwenyi** » Tue Jul 13, 2004 5:14 pm

I don't think it will be a problem finding omega nebula through the 80mm refractor as it's visual brightness is magnitude 6.0.

UHC(narrowband) filters would be to enhance the nebulosity of the area, but be reminded that it will also block out normal light transmission from the stars. Thus resulting in a view that is filled with lesser stars.

cheers,
wenyi

harlequin2902 · Post by **harlequin2902** » Tue Jul 13, 2004 7:14 pm

Skies nice and clear, so decided to do some work on Sagi (since it was nearer the zenith so less Light pollution. Started on the teapot, went to the top, moved to the star above that, found the 2 open clusters (M24 and something else) just below the omega nebula (M17 I think) but couldn't see the nebula, although I was pretty sure I was in the right place.

For a small scope, the Swan Nebula (a.k.a Omega Nebula) is a pretty challenging object under our skies. Don't be fooled by it's seemingly 'bright' 6.0 visual magnitude. It's quite a diffuse object and mag 6.0 in it's case means the brightness of the nebula when condensed into a starlike point. When seen visually under truly dark skies, you'll be able to see it in full and make out the nice 'number 2' or swan-like shape. Anyway, of the 3 popular nebulae in that region (Lagoon M8, Trifid M20 and Swan/Omega M17), I've only managed to see just part of the Lagoon with my 70mm Refractor on a really good night here.

Nebula filters would help a little, but even if M17 is revealed to your eyes through a small scope here in Singapore, you will still only be able to see a wee-bit of it

.

Try the Lagoon [M8]. Less problem for that in small scopes at places like Dempsey Rd on a good night.

ariefm71 · Post by **ariefm71** » Tue Jul 13, 2004 11:03 pm

no problem on my 8"

chrisyeo · Post by **chrisyeo** » Wed Jul 14, 2004 1:05 am

I can see part of the Omega nebula on a clear night with a 90mm Maksutov, which means that you ST80 should be able to detect it as well.

I suspect however that last night's transparency was the factor in your not seeing the nebula. I was stargazing a bit and the nebulae were very faint due to high clouds or haze.

Next time, take a look at the background sky. If it seems a little pinkish and you can't see the nebula, it probably means that its washed out by skyglow. Try easier to find objects in the time being and try again on another night.

Clear skies,
Chris

Post by **Airconvent** » Wed Jul 14, 2004 2:28 am

chrisyeo wrote:I can see part of the Omega nebula on a clear night with a 90mm Maksutov, which means that you ST80 should be able to detect it as well.

I suspect however that last night's transparency was the factor in your not seeing the nebula. I was stargazing a bit and the nebulae were very faint due to high clouds or haze.

Next time, take a look at the background sky. If it seems a little pinkish and you can't see the nebula, it probably means that its washed out by skyglow. Try easier to find objects in the time being and try again on another night.

Clear skies,
Chris

Hi Chris & Chris,

Yes...have seen on my etx90 as well.
However, the swan is generally a fairly dim object (by my standards anyway) and with the current hazy conditions, the chances of spotting it is diminished. However, on a clear night, the shape of the swan is pretty obvious on my etx105 here in singapore.

as what sam is saying, I think you have a better chance looking for M8 instead...!

so far I have not had the chance to look for it on my 80mm refractor but perhaps in the future when the opportunity arises, maybe I'll try it...heh heh

rich

bodoh · Post by **bodoh** » Wed Jul 14, 2004 8:43 am

My replies will be slow for the next few days... computer decided to konk out and so have to do this from office.

Thanks for the advice. Will move on to M8 and start thinking about narrowband filters. Also probably start thinking of getting a good star atlas. Star hopping gets difficult once you have to hop from bright stars to a region with no bright stars (My Stars and planets only show the brightest in a constellation) it's like hantum the rough direction.

By the way what is the lowest star magnitude we are able to see in our skies with a telescope?

Post by **weixing** » Wed Jul 14, 2004 11:30 am

Hi,

Will move on to M8 and start thinking about narrowband filters

I think a narrowband filter may not be very useful for your 80mm scope... It may just cut-off too much light when use in Singapore sky.

By the way what is the lowest star magnitude we are able to see in our skies with a telescope?

This is very difficult to determine. Basically, it will depend on a lots of factor and most are depend on individual, such as the aperture of your telescope, your eyesight, your experience, your age, dark adaption, cloud, haze, light pollution and etc. So it is possible for someone who are experience and have good eyesight to see star fainter than the magnitude limit of his telescope under clear sky.

Anyway, in singapore, you should count yourself lucky if you can see stars as faint as your telescope magnitude limit.

Have a nice day.

MooEy · Post by **MooEy** » Wed Jul 14, 2004 8:31 pm

hmm.. i would say in sg, the limiting magitude for the eye would be around 2.5, for a 3" scope, maybe 5-6. 8" scopes may get luckier and see up to 7-8 mag. but when we go to really dark site(ubin), our eyes can easily see 4-5 mag(most M objects are naked eye), a 3" can see down to 7-8 mag easily.

~MooEy~

Post by **weixing** » Wed Jul 14, 2004 9:57 pm

Hi,

hmm.. i would say in sg, the limiting magitude for the eye would be around 2.5, for a 3" scope, maybe 5-6. 8" scopes may get luckier and see up to 7-8 mag. but when we go to really dark site(ubin), our eyes can easily see 4-5 mag(most M objects are naked eye), a 3" can see down to 7-8 mag easily.

Don't be so "stingy" lah...

I would say on average night, you can see stars up to magnitude 3.7 (M42) and up to around 4.5 on very clear night in Singapore using nake eye.

Also, my 6" scope can see the ring nebula(M57) easily in Singapore which got a total brightness of magnitude 8.8... the surface brightness will be even lower. So a 8" scope surely can do better than that... right.

Anyway, I think a 3" scope can see stars of at least magnitude 9 and a 8" scope can see stars of at least magnitude 11 in Singapore.

By the way, non-star object is a different story, as what harlequin2902 had mention above, the magnitude given on nebula/galaxy/cluster is the total brightness(as if coming from a point), not the surface brightness. So the surface brightness is actually a lots lower if the object is very large. For example, M17 is magnitude 6... which mean it is magnitude 6 if all the light of M17 was coming from a point. But M17 was quite large... around 40' x 30', this mean that the light is spread across this large area, so it will be a lots fainter than magnitude 6.

Have a nice day.