Trapezium

[Andy67]

Apologies if this is a stupid question... I'm still  learning.

I have a  Orion XT8 and Starguider eyepieces (25mm, 18mm, 12mm and 5mm) and I live in a Bortle 4 area. I read  in BBC Sky at Night that with a scope of 6 inches and above I should be able to see the Trapezium  in the Orion nebula. Tonight seemed to be a nice clear night so around 10pm with Orion in the south east I tried to find the Trapezium but I couldn't see it. What am I doing wrong?

 

Edited December 10, 2021 by Andy67

[Stu]

Certainly not a stupid question @Andy67, there’s plenty to learn.

Basics to get right are ensuring your finderscope is aligned accurately, have you managed that? With the 25mm eyepiece in place and focused, you would then need to point at the middle star in Orion’s sword and you should be right on the Trapezium. Are you seeing stars as small pin points rather than larger bright circles? They are focused when at their smallest.

The most likely thing is that you just weren’t in the right place, possibly due to the finder being off. This is where you need to be pointing.

Keep at it and you’ll get there.

[Budgie1]

The only stupid question is the one you didn't ask!

I was basically going to say the same as Stu; use the 25mm eyepiece and get it focused on a star before looking for your target.

Because Trapezium is in the core of the Orion Nebula, which is quite a bright object, it may look more like a fuzzy blob than a pin-point star.

If you're not sure about aligning your finder scope then have a look at this short video for the basics.

 

[Andy67]

Thanks guys. I'm sure I've aligned correctly using my red dot finder. (Check out the screenshots) I'm using the 25mm to target and focus then I'm increasing the power and re-centering each time but I'm not seeing what I think I should be able to see?

[Stu]

@Andy67 I am struggling to make head or tail of the Sky at Night image, it doesn’t look like the Trapezium, where did you find it?

Your last image suggests you are looking in the right place, I’ve circled the Trapezium. With sufficient power you should see the four stars quite easily.

There are a few things which might prevent that. The most likely is that the seeing over most of the country was very poor last night due to the Jetstream being overhead. This made observing at anything other than lowish power quite challenging and this may have made it difficult to see the individual stars.

Other factors might be cooling and collimation, was your scope collimated and cooled properly?

I did see the Trap last night in a little 76mm refractor. Small scopes are often less affected by poor seeing but even so the view wasn’t that great.

I would just keep trying, doing the same things and you will catch good conditions sooner or later.

[Stu]

These are two smartphone images taken through scopes, one at medium power and the other much higher, just to give some more idea of what to look for. The nebulosity is likely to be more muted if your skies are light polluted.

[Andy67]

Thanks Stu.

I screenshot the images from Stelllatium and zoomed in to show what I was looking at. The impression I got from the article in BBC Sky at Night was that I should be able to see the E & F stars too. Am I just expecting  too much and I won't be able to split the stars as much as I thought I'd be able to?  Maybe like you said the seeing wasn't as good as I thought it was. It won't stop me trying though 😊

[Stu]

14 minutes ago, Andy67 said:

Thanks Stu.

I screenshot the images from Stelllatium and zoomed in to show what I was looking at. The impression I got from the article in BBC Sky at Night was that I should be able to see the E & F stars too. Am I just expecting  too much and I won't be able to split the stars as much as I thought I'd be able to?  Maybe like you said the seeing wasn't as good as I thought it was. It won't stop me trying though 😊

E & F are certainly doable but need good seeing conditions to see clearly, especially F in my experience. Get your collimation spot on, make sure the scope is cooled for an hour, and also make sure M42 is at its highest and then you will have more luck. Bear in mind that currently M42 transits the meridian (and so is at its highest) at about 12.30am. In Jan and Feb it will earlier and so at its best at a more sociable hour.

[Andy67]

Thanks for you help Stu. 😊

[Zermelo]

This link was recently posted by @John, showing the area of interest:

https://skyandtelescope.org/observing/star-trapping-in-orions-trapezium/

[John]

I agree with @Stu that the close up Sky & Night image does not look like the Trapezium at all

I was observing Messier 42 a few nights back with an 8 inch newtonian from a site  with some light pollution and slightly unstable seeing and this sketch by Michel Vlasov is a reasonably accurate representation of the view that I had at around 50x magnification and shows the 4 brightest members (A, B, C and D) of the Trapezium group clearly. The E & F stars are much fainter and need both more magnification and better observing conditions to see:

 

Edited December 11, 2021 by John

[Pixies]

Also, bear in mind that last night had very poor seeing conditions over the UK (judging by last night's comments), despite being clear.

Go with your lowest power to find the Orion nebula. Then close in on the "fish's mouth", as per the sketch in John's post. The 4 main stars look great as tiny pin-pricks when seeing conditions are good.  On very good nights, use higher power to try and see E and F stars. F is pretty tricky to see - it'll look like a faint blob, rather than a proper dot, and most of the time just popping in and out of view.

[Zermelo]

Last year on a good night, I saw A-E with a 150mm Newtonian under Bortle 4, and I'm 50% sure that I saw F.

[wookie1965]

In 10 years of using scopes 6&8 reflectors and 4&5" refractors I have only ever seen the e and f stars a handful of times once in the 6" once in the 8" and a couple each for my 4&6" refractors. 

They do need very good seeing conditions to see. 

[neil phillips]

Here is the trapezium last night under poor seeing with a stabilized live camera view 

 

Edited December 11, 2021 by neil phillips

[John]

I have managed to see E & F Trapezium with a 100mm refractor when the conditions are very favourable. The 120mm shows them more routinely and apertures above that, provided the conditions are steady, show them quite easily, when you know where to look for them. With my 12 inch they are really very prominent.

The E star shows itself more readily than F because F is close to the brightest of the main 4 stars.

I've found that I needed to work out the "goldilocks" magnification to tease out the E & F stars. There is some flexibility in what works on a particular evening but often I find that 150x or so works pretty well whatever scope I'm using.

Going back to the original question, yes, the Orion XT8 is certainly entirely capable of showing the Trapezium very nicely and the E & F stars should be attainable as your experience grows and under favorable conditions.

Many years ago I did this sketch of Messier 42 using my old 60mm refractor at 45x magnification. That scope was capable of showing the 4 brightest Trapezium stars quite clearly:

 

[Space Hopper]

I've never got close to seeing the F star, the E maybe once or twice over the last 10-15 years when those brief moments of better seeing come around.

Maybe i've taken my foot off the gas a bit observing wise, and don't get out with the scope often enough,

or, my 54 year old eyes aren't up to it, or i keep buying lemons for telescopes,

Most of the time its just grotty UK conditions that scupper our chances i think ?

 

[RT65CB-SWL]

Since my local authority [Wokingham] changed to LED streetlighting a few years ago, things are a little better. When they replaced the streetlights in my area, my first target was M42 and the Trapezium. Things certainly improved once I purchased an Explore Scientific UHC filter, though still hoping to see the E & F stars.

From my communal garden at the back of my property, I have to contend with this...

that damn streetlight illuminating the footpath!   

Edited December 12, 2021 by Philip R

[John]

19 hours ago, Space Hopper said:

I've never got close to seeing the F star, the E maybe once or twice over the last 10-15 years when those brief moments of better seeing come around.

Maybe i've taken my foot off the gas a bit observing wise, and don't get out with the scope often enough,

or, my 54 year old eyes aren't up to it, or i keep buying lemons for telescopes,

Most of the time its just grotty UK conditions that scupper our chances i think ?

 

I've managed to see E & F occasionally with my 100mm / 102mm refractors (needs very good conditions with those), quite often with my 120mm and 130mm refractors and they are pretty obvious all the time with my 12 inch dobsonian.

Getting the magnification right seems important to getting these stars - I find around 150x -200x to usually be the optimum. F is harder then E because it is close to the brightest of the 4 main Trapezium stars.

 

Edited December 12, 2021 by John

[chiltonstar]

49 minutes ago, John said:

I've managed to see E & F occasionally with my 100mm / 102mm refractors (needs very good conditions with those), quite often with my 120mm and 130mm refractors and they are pretty obvious all the time with my 12 inch dobsonian.

Getting the magnification right seems important to getting these stars - I find around 150x -200x to usually be the optimum. F is harder then E because it is close to the brightest of the 4 main Trapezium stars.

 

Agreed. I use a zoom ep most of the time now for doubles, which I find ideal for the Trapezium. Low mag shows the E star best, then winding up the mag splits the F star from its companion.

Chris

[Cosmic Geoff]

The four brighter stars of the Trapezium are easy to see, but the E and F are more difficult. AFAIK I have only seen the E and F stars by imaging the Trapezium with my 8" SCT.

[SuburbanMak]

I spent a long time on M42 late Friday night and from the South (Winchester) seeing was poor at first rising to average as the night wore on (until that bank of cloud arrived...) around 100x was the maximum magnification the air would support. 

With a 127 Mak & Baader Mk IV zoom I was getting the A, B, C & D stars consistently with direct vision.  At times I'd catch a glimpse of the E star for a second only for it to "swim" out of view as I tried to focus my eye on it. In those moments of clearer seeing I could pick up some elongation in the bright C-F pair but definitely not a clean split or even really resolved. Come to think of it I am not sure I have seen this pair really clearly demarcated with a black line between, although on decent nights I would routinely expect to see 5 stars in the Trap' with the nearly-five inch Mak.   

[John]

The separation of the E & F stars from A & C is around 4.5 arc seconds which is resolvable, in theory, by scopes from 50mm and upwards. What makes them a challenge is the brightness of A and C and also I think the nebulosity within which the group is embedded.

 

 

[Owmuchonomy]

Here's a complementary thread to this one from 2018: