Crab nebula in the burbs?

[Rob_K]

At the other end of the scale, with a 4.5" reflector it's very dependendent on sky conditions. From my backyard in good skies it's easy to see as an oval glow, but very even and never a hint of structure. When the transparency goes off even a fraction it becomes quite difficult to see. With a tiny bit of skyglow, forget it - move on to M42, LOL!

Cheers -

[Rev (Greg)]

The Crab is underwhelming in good and poor seeing. Under my semi dark coastal skies it is a grey oval smudge in an 8"sct. I observed it on Feb 10 in my 14" and while showed some subtle texture but I must admit it's low surface brightness still leaves me underwhelmed. Perhaps it's fame as "the Crab Nebula" and Messiers 1st object builds my expectations too high.

[Vanda (Ian)]

Will try Mentals approach in finding it with my 150 Refractor next time - have not seen it yet - Perth's night glow is a problem though - will try a UHC filter as well.

[Lismore Bloke (Paul)]

While outside on Saturday night I spotted the Crab pretty easily as a faint grey oval in the 20x80 binos, along with NGC 5128 and lots of other DSO's.

[mental4astro (Alexander)]

Tough alright!

Had a go tonight with my 10" f/4.9. It lies directly over the city from my place. Only spotted with a 15mm EP and a nebula filter. Just. Not good seeing either. Even M42 was far below par.

Not a problem with my 17.5" from home. Too easy with such grunt.

Intrigueing to think that Messier spotted this one and missed much brighter objects in forming his first catalogue.

[ngcles]

Hi Alexander & All,

Originally Posted by mental4astro

Tough alright!

Had a go tonight with my 10" f/4.9. It lies directly over the city from my place. Only spotted with a 15mm EP and a nebula filter. Just. Not good seeing either. Even M42 was far below par.

Not a problem with my 17.5" from home. Too easy with such grunt.

Intrigueing to think that Messier spotted this one and missed much brighter objects in forming his first catalogue.

Yes I agree, it is not a particularly easy object from suburbia, though a UHC or OIII filter improves it somewhat and it is certainly visible from suburban Engadine in my old 25cm at low-moderate magnifications with a filter.

It is not really surprising that Messier saw it -- it was almost at Zenith in his sky which was somewhat darker overall that the suburban skies of today. He also saw it while observing a comet that passed almost straight over the nebula! Messier didn't discover it though -- it was found by Bevis about 25 years earlier.

We also have to remember that modern values show the whole nebula is now about 13ly across -- a size it has taken 1000-odd years to achieve. Back 250 years ago it was probably more like 8ly across and accordingly would have had higher surface-brightness than now (the integrated brightness is certainly no more than it was 250 years ago and is probably a bit less). In fact, the surface-brightness probably would have been about double then compared to now.

As for nowadays, the red-coloured tendrils that were once the outer envelope of the red-supergiant progenitor star (mainly ionised Hydrogen & Helium) are not really visually observable unless you have a giant telescope. They record well on film and CCD that is much more sensitive to H-Alpha emission.

The part that is more readily visible is the slightly smaller-sized, diffuse, blue emission which is by-and-large powered by synchrotron radiation. Synchrotron radiation is produced by electrons being accelerated within strong magnetic fields (pulsars have extreme magnetic fields) to velocities close to c.


Best,

Les D

P.S 990 -- nearly there!!

[Paddy (Patrick)]

Originally Posted by ngcles

As for nowadays, the red-coloured tendrils that were once the outer envelope of the red-supergiant (mainly ionised Hydrogen & Helium) are not really visually observable unless you have a giant telescope. They record very well on film and CCD that are much more sensitive to H-Alpha emission.

The part that is more readily visible is the slightly smaller-sized, diffuse, blue emission which is by and large powered by synchrotron radiation. Synchrotron radiation is produced by electrons being accellerated within the strong magnetic fields (pulsars have extreme magnetic fields) to velocities close to c.


Best,

Les D

P.S 990 -- nearly there!!

Very interesting - this explains a lot!

PS Looking forward to 1000+ of your posts - they are all gems.

[DavidU (Dave)]

I had a very quick look last night with the 12" and couldn't see a thing.
I will try again tonight.

[tonybarry (Tony)]

From Werrington, near Penrith (Sydney), I saw M1 just once, on the 18th January this year. LX90-8" GPS UHTC with a f/6.3 reducer. The object was at the limits of visibility, and if I did not have the Goto mount I would never have been able to locate it. Light pollution was mainly to the east, but was moderate to high.

I used a GStar-EX to acquire M1 - the low light ability of the camera was the difference between moving on to something else, and spending three nights capturing frames. Once the object was firmly in the centre of the screen, I whipped out the eyepiece (18mm Meade series 5000 UWA) and could ... just ... see it.

This was the second time I have seen M1 visually; the previous time was at Linden, the WSAAG's dark site. There it was quite visible.

Regards,
Tony Barry

[fragchamp]

Interesting Les.

I saw this target once and found it too uninteresting to return to. It's one for the photographers.

[RobF (Rob)]

Originally Posted by ngcles

Hi Alexander & All,



Yes I agree, it is not a particularly easy object from suburbia, though a UHC or OIII filter improves it somewhat and it is certainly visible from suburban Engadine in my old 25cm at low-moderate magnifications with a filter.

It is not really surprising that Messier saw it -- it was almost at Zenith in his sky which was somewhat darker overall that the suburban skies of today. He also saw it while observing a comet that passed almost straight over the nebula! Messier didn't discover it though -- it was found by Bevis about 25 years earlier.

We also have to remember that modern values show the whole nebula is now about 13ly across -- a size it has taken 1000-odd years to achieve. Back 250 years ago it was probably more like 8ly across and accordingly would have had higher surface-brightness than now (the integrated brightness is certainly no more than it was 250 years ago and is probably a bit less). In fact, the surface-brightness probably would have been about double then compared to now.

As for nowadays, the red-coloured tendrils that were once the outer envelope of the red-supergiant progenitor star (mainly ionised Hydrogen & Helium) are not really visually observable unless you have a giant telescope. They record well on film and CCD that is much more sensitive to H-Alpha emission.

The part that is more readily visible is the slightly smaller-sized, diffuse, blue emission which is by-and-large powered by synchrotron radiation. Synchrotron radiation is produced by electrons being accelerated within strong magnetic fields (pulsars have extreme magnetic fields) to velocities close to c.


Best,

Les D

P.S 990 -- nearly there!!

Fascinating too to read about objects that have changed over the last 100-200 years, especially "faint fuzzies" like the Crab neb. I enjoyed this info too thanks Les.

[seanliddelow (Sean)]

I have seen M1 in my 12" Dob from moderately light polluted skies.
It is a very boring shapeless smudge even in a 12" with no sign of structure. Sometimes I wonder how Messier even saw it at all. Its even harder to see then a galaxy cluster in Eridanus from my skies.