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Trapezium 6 Star Question

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#1 28gauge

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Posted 17 September 2022 - 03:42 PM

Frequent viewer of the Orion Nebula and its Trapezium. However, I can't ever see all 6 stars, only the 4 main stars. How seeing sensitive are they to resolve? I'm using a Stellarvue 4 inch refractor with various magnifications usually in the 150x to 200x range. 



#2 dave85374

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Posted 17 September 2022 - 03:49 PM

I can sometimes see 7 now, but only once have I seen (or thought I saw) all 8 and that was just after a collimation in the parking lot at Starizona from their old location approximately 20 years ago in an 8" original Nexstar.



#3 Ihtegla Sar

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Posted 17 September 2022 - 04:30 PM

I've seen 6 stars in my FC100DL but it sometimes takes averted vision and very good seeing. And E and F are not always visible. They pop in and out of view. Most of the time I can only see 4 or maybe 5 stars in a four inch scope. E and particularly F are challenging targets in a four inch scope.

F is more challenging than E since its next to C which is much brighter than A, which is next to E. I've seen E a bunch of times in a four inch scope but only seen F a couple times.

Larger scopes will pick up more stars easier. I can easily see 6 stars on an average night in my 140mm refractor.

Edited by Ihtegla Sar, 17 September 2022 - 04:34 PM.

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#4 28gauge

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Posted 17 September 2022 - 04:37 PM

Thanks. Seems like I need excellent seeing conditions with 4 inches of aperature.


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#5 spereira

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Posted 17 September 2022 - 04:42 PM

Moving to Deep Sky Observing.

 

smp



#6 Stellar1

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Posted 17 September 2022 - 04:49 PM

With my old 115 mm Eon I was able to catch E&F on the best of seeing conditions but they sort of come and go from view. With my 150mm Mak they were clear as day on many occasions, I haven’t tackled this with my 102 but I suspect I’m in for a challenge.



#7 BrentKnight

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Posted 17 September 2022 - 05:08 PM

I've only gotten all 6 on one occasion with my AT102ED.

 

If you're interested, here is my original post: Observation Log



#8 28gauge

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Posted 17 September 2022 - 05:55 PM

I've only gotten all 6 on one occasion with my AT102ED.

 

If you're interested, here is my original post: Observation Log

Thanks. I'm about 2 years with visual so I now understand those E and F stars are challenging and will keep at it. Read your original post and found it informative. I typically can get a good resolve on the Rigel pair, even with smaller aperatures. A tight double in Orion I always enjoy is Alnintak, in the belt. With about 180x I get that sharp black seperation.


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#9 Redbetter

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Posted 18 September 2022 - 03:04 AM

E & F require better seeing (stability of the air and therefore focus) for small apertures.  That has been my experience.  The seeing we have available to us varies based on region, local features, and season.  My dark site usually has decent but rarely truly great seeing, while my backyard usually has poor seeing and is rarely good. 

 

A large factor in observing dim unequal doubles (which is what E and F amount to) is the observer's eye.  For whatever reasons, some folks can pick out very dim stellar points next to bright objects that others struggle with even when the seeing is good.  It isn't just experience, or aperture, or technique; there are some fundamental differences in the way some are able to detect very dim (but not limiting magnitude threshold) adjacent to glare sources.  The point is that there is a range of physical ability to make this type of detection even in favorable circumstances; so while it is good to learn what you can and cannot do, it doesn't necessarily mean there is anything wrong with the observer or technique if they simply can't see it without more aperture.

 

The same is true with things like faint moons near bright planets, central stars in planetary nebulae, etc.  When the seeing is good enough I have been able to detect M57's central star with as little as 156x with the 20".  I normally detect it at 278x when visible.  Others will swear it takes much higher magnification to make the detection, and I accept that is true for them.


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#10 cuzimthedad

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Posted 18 September 2022 - 12:37 PM

Like Brent, I've only once seen 6 stars through my TV102 when the seeing was near perfect which doesn't happen often.



#11 payner

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Posted 18 September 2022 - 01:25 PM

The E and F stars are readily seen through a good 4", but as Redbetter stated, seeing needs to be stable.



#12 CowTipton

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Posted 19 September 2022 - 12:45 PM

Frequent viewer of the Orion Nebula and its Trapezium. However, I can't ever see all 6 stars, only the 4 main stars. How seeing sensitive are they to resolve? I'm using a Stellarvue 4 inch refractor with various magnifications usually in the 150x to 200x range. 

Very seeing sensitive in my limited experience.

With my previous 8"f6 dob I saw the E star only a few times, on the rare above average seeing nights.

 

With my 14" dob I see the E star almost all the time but have only seen the F star when conditions are above average (again, rare.)

 

I recently purchased an AT102ED so I'm hoping to give that a try soon when Orion comes overhead.  Most likely only 4 stars with the 4" refractor though.



#13 Chad7531

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Posted 20 September 2022 - 05:14 AM

I was just viewing m42 in my 6” reflector. Bortle 7, seeing 4/5, transparency 3/5. Only 4 stars visible, the nebulosity was amazing though, one of those wow moments. Hopefully I get some clear skies at the dark site this weekend to view it in the 10”.

Edited by Chad7531, 20 September 2022 - 05:23 AM.


#14 Bill Barlow

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Posted 22 September 2022 - 11:44 AM

I can see the E and F stars almost all the time in my 6”, 8” and 11” SCT’s from my Bortle 8 skies here.  But in smaller apertures, the F star is a tough call some nights.  To me it depends on the seeing and transparency while using magnifications of 100-200X.  

I have a TV 85 that I haven’t tried to view the Orion Nebula yet.  
 

Bill



#15 Chad7531

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Posted 22 September 2022 - 05:12 PM

I can see the E and F stars almost all the time in my 6”, 8” and 11” SCT’s from my Bortle 8 skies here. But in smaller apertures, the F star is a tough call some nights. To me it depends on the seeing and transparency while using magnifications of 100-200X.

I have a TV 85 that I haven’t tried to view the Orion Nebula yet.

Bill


Perhaps I’ll try some magnification next time instead of the nebula view.

#16 rgk901

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Posted 22 September 2022 - 06:53 PM

here from B8/9 using my 5" newt I was able to see the E many times when the seeing and transparency was good. Although that has been the past years of the pandemic so not sure if the skies where darker.

I don't do well without sleep so will have to wait till later in year before I try again.

Love the Orion nebula!

#17 Asbytec

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Posted 25 September 2022 - 05:23 AM

In my experience, yes, E and F can be difficult in a 4" class aperture. Sometimes one, but not the other. Sometimes both rolling in and out of view. One night, however, one magical night all 6 were steady bright pinpoints. Quite a stunning sight. Transparency and excellent seeing conditions. I say transparency because the winter Milky Way was brighter on that same evening. Magical...


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#18 jonbosley

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Posted 25 September 2022 - 05:31 PM

It is recommended a 6inch is needed for the six. I would expect you would need bortle 1 or 2 and seeing close to 1 arcsecond to pick them up in a 4”. So I wouldn’t worry to much that you have not managed to see them as yet. 

I can pick all out with the 18” at 250x 1.5 arcsec seeing bortle 3.9

 

Here is a good article on them https://skyandtelesc...ions-trapezium/


Edited by jonbosley, 25 September 2022 - 05:31 PM.

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#19 BrentKnight

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Posted 25 September 2022 - 09:10 PM

It is recommended a 6inch is needed for the six. I would expect you would need bortle 1 or 2 and seeing close to 1 arcsecond to pick them up in a 4”. So I wouldn’t worry to much that you have not managed to see them as yet. 

I can pick all out with the 18” at 250x 1.5 arcsec seeing bortle 3.9

 

Here is a good article on them https://skyandtelesc...ions-trapezium/

It does not require Bortle 1 or 2 skies.  I have seen all 6 from Bortle 4 with excellent seeing on the Gulf of Mexico.  It was a challenge, but it is possible with a good 4".


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#20 Redbetter

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Posted 26 September 2022 - 03:41 PM

It does not require Bortle 1 or 2 skies.  I have seen all 6 from Bortle 4 with excellent seeing on the Gulf of Mexico.  It was a challenge, but it is possible with a good 4".

This is especially true since the Orion nebula itself, in which these stars are embedded, is effectively heavily light polluted.  The same is true of the Ring nebula's central star. 

 

Seeing is the biggest factor, along with brute force aperture, and of course the individual observer's eye.  Some folks have much more trouble with close, high delta magnitude double stars--and E and F are examples of this.  


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#21 Bill Barlow

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Posted 30 September 2022 - 11:20 AM

I have seen all 6 in Bortle 8 skies it’s a Tak FC76 DCU but most of the time the F star wasn’t visible. But in my C6 and M8 I can see all six every time.  Need good transparency and good seeing conditions.  Going to see soon if all six can be seen in my TV 85.

 

Bill


Edited by Bill Barlow, 30 September 2022 - 11:21 AM.

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#22 Allan Wade

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Posted 01 October 2022 - 05:27 AM

Already mentioned, but the Trap stars are very seeing dependant. The other variable is optical quality. I had a brilliant TV76 that I could see 6 Trap stars with, but my ordinary TV85 could never see the F star.

 

Also, there is no such thing as seeing all 6 stars. I thought I had seen ‘all 10 stars’ until a friend observed 11 stars. So I’m not putting a limit on it anymore. But the Trap is certainly a favourite object I check in on almost every session. It wasn’t until I got the big dob I realised that E and F display a beautiful orange and green colour that I’ve not seen in smaller scopes.


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#23 dave253

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Posted 01 October 2022 - 06:03 AM

It wasn’t until I got the big dob I realised that E and F display a beautiful orange and green colour that I’ve not seen in smaller scopes.

That’s very interesting, Allan. It’s only late last summer that I finally got to see E+F.

Up here in north coast NSW we often have nice transparency and dark sky, but very rarely excellent seeing.

 

Since getting a CC and really nailing the collimation, I feel my 14” is delivering the best images possible so I’m looking forward to giving it another crack. 


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#24 Chad7531

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Posted 02 October 2022 - 04:13 AM

I was out again in average conditions in bortle 7 with my 6” reflector. Went over 500x and still just 4 stars. I guess I’ll have to wait for better conditions for that scope. My next attempt will probably be at a bortle 4 with the 10”.
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