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Piero

Testing 'E' and 'F' in trapezium - plus other targets

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Another clear night with little wind. :) 

Transparency was okay in the beginning, but gradually improved later on.


I would like to thank Gerry for intriguing me to look for the stars E and F in trapezium (Orion) :) Eventually I was not able to spot them, but it was an interesting test. Whether permitting, I will repeat it with a larger telescope later this month.


Cheers, 

Piero




Date 11/12/2015

Time 21:00-23:30

Location Cambridge, UK

Altitude 12m

Temperature 5C (WSW 12 km/h)

Seeing 2 - Slight undulations

Transparency 5 - Clear

Telescopes Tele Vue 60 F6

Eyepieces Panoptic 24, Nagler 13, Nagler 7, Nagler 3.5, PM2.5x

Filters Astronomik UHC


M42 Ori CL+Neb 51x, 69x, 103x, 129x

Trapezium visible. I searched for E and F for 40 minutes at different magnifications. None. There were times where C reminded me of the two stars forming the double double when seen at ~50x. In other words, there were times where C seemed a tight coupled double, but it could have just been an artefact of my eye to be honest! If visible, I reckon the exit pupil should be larger than 0.8-1.0mm otherwise the Airy discs tend to be too large and the brighter stars forming the trapezium might cause issues. The dimmer star was barely visible at 103x and 129x, whereas observable distinctly at lower magnifications. 


Lambda Ori Star 15x

Meissa. Nice chain of stars positioned on the top of Orion.


Cr65 Tau Opn CL 15x

Extended cluster above Meissa, but below M1. The field of view is about 3 degrees I think.


NGC2169 Ori Opn CL 15x, 38x

The 37 cluster. It is located between Lambda Ori (Meissa) and Gamma Gem (Alhena) on Orion's right arm. A chain formed by 8-10 stars is immediately detectable south of this open cluster. Following this chain to north, one reaches this little gem. I could see 9-10 stars, some of them really faint.


NGC2244 Mon Opn CL 15x, 38x

Satellite Cluster. Observed more in detail. Its shape reminds me of a broken domino piece. It is at the centre of the Rosette nebula. I didn't try the latter because the sky was not sufficiently transparent.


NGC2264 Mon CL+Neb 15x, 38x

Christmas tree. A nice open cluster formed by moderately bright stars. No trace of the Cone nebula surrounding the brightest star of this cluster.


M78 Ori Neb 15x, 38x +/- UHC

From Alnitak, I star hopped until I reached the pattern of stars nearby this nebula. It was very faint and I could spot it with difficulty at 38x without filters. With a filter I was no longer able to see it. At 15x, it was just invisible, possibly due to the insufficient sky transparency.


M31 And Galaxy 15x, 38x

Trapezium visible. I searched for E and F for 40 minutes at different magnifications. None. There were times where C reminded me of the two stars forming the double double when seen at ~50x. In other words, there were times where C seemed a tight coupled double, but it could have just been an artefact of my eye to be honest! If visible, I reckon the exit pupil should be larger that 0.8-1.0mm otherwise the Airy discs tend to be too large and the brighter stars forming the trapezium might cause issues. The dimmer star was barely visible at 103x and 129x, whereas observable distinctly at lower magnifications. 


M34 Per Opn CL 15x

A quick view to this beautiful open cluster between Andromeda and Perseus. 


NGC869/ 884 Per Opn CL 15x

Almost at the zenith. As usual, it was spectacular and very clear.


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Quite an evening you had Pierro. I hope you get out soon and do some observing. I 'll learn about that trapezium in Orion...

Cheers from Greece

Tzitzis

Edited by Tzitzis
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Nice session Piero. I often struggle with E and F in my Tak 4". E is normally possible but F is more difficult in my experience. They are sensitive to good seeing and the right magnification.

My best chances from home happen when M42 is over the gaps in between my house and the neighbours, the seeing is much better there.

By the way, I think your M31 report has got replaced by a duplicate of the M42 one?

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Good report Piero :smiley:

E & F can be challenging especially if the conditions are not too steady.

Like Stu, I have to wait for some targets to clear rooflines etc. No wonder I'm finding the Horsehead ellusive ! :rolleyes2:

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Very nice report. You had a very productive session. E and F are a real challenge at times. I have only found them when the seeing is really good and usually from a dark sky site.

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Good report Piero :smiley:

E & F can be challenging especially if the conditions are not too steady.

Like Stu, I have to wait for some targets to clear rooflines etc. No wonder I'm finding the Horsehead ellusive ! :rolleyes2:

I apologise for this in advance John, but do you need 'stable' conditions to see the Horsehead? [emoji12]

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Nice session Piero. I often struggle with E and F in my Tak 4". E is normally possible but F is more difficult in my experience. They are sensitive to good seeing and the right magnification.

My best chances from home happen when M42 is over the gaps in between my house and the neighbours, the seeing is much better there.

By the way, I think your M31 report has got replaced by a duplicate of the M42 one?

Thanks Stu  :smiley:

You are right it was a clear mistake. I wrongly copy and paste the description text for M42 in the text area for M31 in the spreadsheet before parsing it with AstroJournal. I apologise for this inconvenient.

The following description was more or less what I lost in that copy / paste. (Not much!)

M31 And Galaxy 15x, 38x
Andromeda Galaxy. It was beyond the Zenith in an area of sky affected by Cambridge sky glow from the position I observed. For this reason only the core was visible. M32 and M110 were invisible.
----- 
About E and F, what you said makes all sense to me. I think the seeing was good (although not great) yesterday. The problem with a 60mm is resolution or the fact that the Airy disc of stars become larger at what people normally consider medium / medium-low magnification (50x-100x). Therefore with a 60mm, one is right in a trade-off between needing more magnification for splitting and avoiding large Airy discs which my prevent from splitting or even detect E or F. The magnitude for E and F (~10.5) is also right at the very limit for a 60mm. 
TRAPDIAG.jpg
I guess for this telescope it is required the best conditions in terms of transparency, dark sky, seeing, good position in the sky, and no more than ~100x. 
It was fun to test this though! :rolleyes:
Have some of the DobMob tried G and H ??  :grin:
Edited by Piero

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...

Just saw your signature! :eek:  "Minimalist observing - a Tak and a TAL"? 

What happened to the "frac gang" and all the rest?? Is this change related to your post about light pollution? 

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Just saw your signature! :eek: "Minimalist observing - a Tak and a TAL"?

What happened to the "frac gang" and all the rest?? Is this change related to your post about light pollution?

[emoji12], no, I'm afraid I had an urgent requirement for cash and most of the scopes had to go. I'll re-invest when things level out a bit.

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nice report and some good targets...here's to clear dark skies for all!!

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I apologise for this in advance John, but do you need 'stable' conditions to see the Horsehead? [emoji12]

Ha, ha ! :grin::p

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[emoji12], no, I'm afraid I had an urgent requirement for cash and most of the scopes had to go. I'll re-invest when things level out a bit.

Sorry to hear this Stu! Hope all can be sorted soon

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[emoji12], no, I'm afraid I had an urgent requirement for cash and most of the scopes had to go. I'll re-invest when things level out a bit.

welcome to the 2 scope club Stu....

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seen the E AND F last night very obvious and the best i have ever seen it, even sirius was steady as a rock, should of seen m42 it looked like it was made of string. these targets were with the 8E

Edited by faulksy
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welcome to the 2 scope club Stu....

Hmmm, trouble is I've gone from 58" of available aperture to 8"! A lot simpler though.

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seen the E AND F last night very obvious and the best i have ever seen it, even sirius was steady as a rock, should of seen m42 it looked like it was made of string. these targets were with the 8E

Very often I find 8mm just the "right" focal length to get E & F even when using different focal length and aperture scopes !

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Hmmm, trouble is I've gone from 58" of available aperture to 8"! A lot simpler though.

your sig is missing another "T" scope :wink:

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your sig is missing another "T" scope :wink:

??

EDIT got it [emoji6]

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Very often I find 8mm just the "right" focal length to get E & F even when using different focal length and aperture scopes !

even more strange john, popped the 5mm pentax in and couldnt see them :eek: :eek: , swopped again, and they were there, 200x lovely

Edited by faulksy

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even more strange john, popped the 5mm pentax in and couldnt see them :eek: :eek: , swopped again, and they were there, 200x lovely

I've had the same experience Mike. With E & F Trap it seems there is a "goldilocks" eyepiece focal length. Maybe a certain exit pupil as well ?

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I've had the same experience Mike. With E & F Trap it seems there is a "goldilocks" eyepiece focal length. Maybe a certain exit pupil as well ?

Seems perhaps to be between 1mm and 1.5mm based on your scopes John?

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I have picked out E&F in an 80mm refractor with good seeing and transparency. I found x80 magnification offered the more obvious split at the time. Double stars always present them selves best in a refractor in my experience. I need the seeing to be perfect to get a similar view in my newts.

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I have picked out E&F in an 80mm refractor with good seeing and transparency. I found x80 magnification offered the more obvious split at the time. Double stars always present them selves best in a refractor in my experience. I need the seeing to be perfect to get a similar view in my newts.

That's very good going Nick, another vote for a 1mm exit pupil.

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Great report, you obviously had a great night of observing.... I looked out for extra star in the trapezium a few days ago and I definitely saw E, also F was coming and going out of the view, looking at the star map Piero posted, it was it the right place so from my location the 8SE did also reveal star F but just barely.

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