Well, what a difference seeing and altitude make! I looked outside the window at 2:00am and saw Orion so decided to try to capture a set of images of the Trapezium stars A B C D E F G H & I.
By 3:00am the ‘scope had cooled and I estimated the seeing to be around 8/10. Using the Mewlon 180 F12, TeleVue x2.5 PowerMate and DMK21AF04.AS CCD camera I tried various exposure settings to see which would be best.
Pane 1: Limiting the exposure to 1/30 got me stars A through F, even revealing the stellar diffraction rings around the brighter components.
Pane 2: Increasing the exposure to 1/15 sec made the stars more blobby although the separation between components A to F was clear and steady due to the very good seeing and the altitude of Orion.
Pane 3: Finally, I tried exposures of 1/3 sec to see if I could dig out the fainter components G H & I.
Pane 4: After stretching the data using the histogram, it became apparent that the seeing had supported the splitting of H1 and H2. I then overlaid this stretched image of a Hubble image and the components lined up precisely.
Data from SkyTools:
Theta 1 Ori, Multiple Star System, Magnitude: 5.13
AB: 5.13+6.35 mag, In 1991: PA 312° Sep 12.87"
AC: 5.13+7.2 mag, PA 56° Sep 13.12"
AD: 5.13+7.49 mag, PA 342° Sep 16.87"
AE: 5.13+6.4 mag, PA 134° Sep 135.30"
EF: 6.4+7.5 mag, PA 92° Sep 52.50"
EG: 6.4+9.1 mag, PA 97° Sep 128.70"
BH: 6.35+11.1 mag, Sep 4.10"
AI: 5.13+11.5 mag, PA 122° Sep 4.00"
Yep, gotta agree, a legend. One thing I really like is that they are all on the one page. So many IIS folk post comparisons but then require you to open one, close it then open another, by which time my pea sized brain has forgotten what choice # 1 looked like.
Stunning work Dennis, well done.
Dennis, and others, it is obvious that this is a very difficult image to achieve, and i ask this genuinely, as i know nothing about this object, and seeing that you have imaged all those stars mentioned, it must be a tricky one to get.
I also ask, is an image like the one you have captured, available to most optical systems, or is it necessary to have certain f ratio and/or magnification.
I would be very interested to know this, also is this image only available for imaging at certain times of the year.
Good seeing and a good optical system (smooth, collimated, etc.) can help stop the brighter stars bloating and drowning E & F. With poor seeing, E & F tend to get drowned by A & C.
My overall focal length was 2160mm x2.5 = 5400mm and that helps put distance between each stellar component.
Webcam = good as you can stack silly numbers of frames whilst keeping exposures short, to take advantage of moments of excellent seeing.
Precise focusing is important. I found that very short stabs on my (new) motorised Moonlite focuser button got me to best focus.
With good seeing (7/10 or better) you also benefit from having Orion over 50 degrees altitude. Oh, and a spot of luck is required too!
However, having said all of that, Ken with a much less sophisticated system, easily grabbed G & H, so it’s worth trying and modifying your approach based upon the results you get. I’m still blown away with what Ken achieved with the relatively lowly ToUcam and a non-tracking dob; the man’s a star!
Definitely have a go; it is a real challenge and enormous fun!
The trick, Leon, is that some of them are variables, and they are at their brightest at different times!
A & B are eclipsing binaries
'A' drops to mag 7.65 every 65 days
'B' drops to mag 8.65 every 6 days
G, H, and I are all variables.
I attempted for months to get all 9 stars, but as I saw 'I' appear, 'B' had slightly faded, and 'H' was completely gone and 'G' was very very faint.
Onya Dennis!!!!!!
