The Trapezium with the SW ED150

[Owmuchonomy]

The new SW Evostar ED150 is really getting some use here after my initial tests.  We are having a good run of clear skies.  This morning I got up at 3:30 am to do a lunar imaging run (see elsewhere). After that I quickly set up on M42 as it was near the local meridian.  Using my ES 4.7mm 82' EP (255x) I concentrated on the Trapezium first.  I was staggered by the view not only because of the detail under the Moon but because all 6 stars (A to F) were clearly visible immediately and pin sharp sitting in a greenish mist.  Here is my really quite poor chalk sketch of the approximate view hastily drawn on my obsy blackboard wall (ignore the screws in the ply):

Checking with the detailed Whitepeak Observatory graphic the stars I believe in clockwise order are from the top right: B, D, F, C, A, E.  I have often tried to view the 6 stars before with my SCT 9.25" but this scope revealed them with ease.

Star C (Theta-1 C Orionis) is described in the same graphic as an Extreme star: 40 Solar Masses; Surface temp 40,000K, the hottest known <6mag star; 210,000x sun's luminosity and an O6 spectral type.

I then swapped to my 2" 24mm ES 82' EP to view M42 but that view was swamped somewhat by moonlight so I will have to wait a while to try that.

 

[JohnSadlerAstro]

Hi,

This is probably a bit of a stupid question, but how apo is it? I've heard people suggesting it wouldn't be good on stars because of its large lens. Is this the case? ?

John

[Owmuchonomy]

Just now, JohnSadlerAstro said:

Hi,

This is probably a bit of a stupid question, but how apo is it? I've heard people suggesting it wouldn't be good on stars because of its large lens. Is this the case? ?

John

It's very well controlled. I haven't been able to detect any real chromatic aberration, perhaps a faint violet on the brightest stars.  its as good as my ED120 was.  A bright Moon limb didn't phase it either.

 

[John]

Good stuff Chris.

My ED120 shows E & F Trapezium but they are somewhat harder with my Tak 100. Doable on a good night though.

Although the 2 ED150's that I had were out of sorts optically I did notice that false colour was well controlled with them. If Skywatcher can sort out the packaging so that 100% of the scopes arrive in optically good shape I think it will be a winner

 

[Owmuchonomy]

I have been very lucky I think.  This is an excellent example of what the scope is capable of.  I noticed on screen when I had the ASI290MM camera on for the Click-Lock test that the airy disc was spot on.  I have some Moon images to sort out so that will be my next post.

[des anderson]

That`s a good result, I`ve struggled to observe the stars C, A, E. with my 9.25SCT. But B,D, and F visible in a Badder Hyperion 10mm at x235. Des

[John]

I'm rather surprised that C9.25's are struggling with E & F Trapezium

[Owmuchonomy]

C is the brightest of all 6, a variable with an average of 5.1 mag.

[Stu]

Just now, John said:

I'm rather surprised that C9.25's are struggling with E & F Trapezium

The joys of cooling and perhaps collimation John. I've always found SCTs struggle with these more than refractors, particularly F which requires good control of C to pull it out of the glare.

Best view I've had of these by far is through Gav's TEC160. No surprise I guess!

[Owmuchonomy]

2 minutes ago, John said:

I'm rather surprised that C9.25's are struggling with E & F Trapezium

I can mount the 9.25 next to the 150 on the AZ EQ 6 GT ?.  I have recently collimated the 9.25 too so I'll put it on the to do list.

[Stu]

5 minutes ago, des anderson said:

That`s a good result, I`ve struggled to observe the stars C, A, E. with my 9.25SCT. But B,D, and F visible in a Badder Hyperion 10mm at x235. Des

Des, A,B,C and D are trivial in just about any scope so I'm sure you must be seeing them? It is E and F that are the challenge, with E generally being easier than F in my view.

[des anderson]

These old eye`s ar`nt as good as they used to be, but winters coming and I`m up for a challange. Maybe the scope needs a tweak or I do......Des

[John]

My best views of E & F come with my 12" dob unsurprisingly. They are really "in your face" with that scope !

Regularly seen with the ED120 as well though. As with many of these targets, once you have seen them, you wonder how you missed them !

I agree with Stu - even my old Tasco 60mm would show A-D quite nicely.

 

[ollypenrice]

This observation is massively seeing-dependent and does require optics to be at ambient as well. I'm not surpized that the 6 inch apo handled itself so well.

Olly

[Peter Drew]

Very dependent on magnification as well, too much or too little and E & F seem to disappear.    ?

[John]

1 minute ago, Peter Drew said:

Very dependent on magnification as well, too much or too little and E & F seem to disappear.    ?

Too true. 8mm (199x) seems to be spot on for E & F with my 12" dob.

 

[F15Rules]

I find that c 140-160x is optimum for E&F with my FS128?

Dave

[NGC 1502]

On 01/10/2018 at 20:46, Stu said:

Des, A,B,C and D are trivial in just about any scope so I'm sure you must be seeing them? It is E and F that are the challenge, with E generally being easier than F in my view.

 

Fully agree, ABC&D easy at 19x with my Pronto.    OO 10” Dob E&F easy at 150-200x but only if seeing is ok.  

Always a treat, however many times I view them......?

Ed.

 

[John]

I often use Rigel as a guide to seeing. If I can split that easily and also see the 4th star of Sigma Orionis (just below the lowest of the 3 "belt" stars), E & F Trapezium are usually "on" that night

Can't wait for Orion to start showing properly - there is so much to see in that constellation !

[F15Rules]

1 hour ago, John said:

I often use Rigel as a guide to seeing. If I can split that easily and also see the 4th star of Sigma Orionis (just below the lowest of the 3 "belt" stars), E & F Trapezium are usually "on" that night

Can't wait for Orion to start showing properly - there is so much to see in that constellation !

i agree John, Orion has to be my favourite, and seeing the Pleiades starting to rise ahead of Orion always gives me a little tinge of excited anticipation..

Dave

[BGazing]

Good seeing tonight, not even fully dark, waiting for the Moon to clear building I was looking at Rigel, Sig Ori...and then Trapezium. 7mm T6...and saw E and F, caught me by complete surprise!

Bumping to 150x it was even more obvious. I am still stunned.

I guess it is seeing...and Tak fluorite magic.

[John]

Nice one !

I've just pointed my 12 dobsonian at it and E & F were surprisingly easy considering the twilight sky.