Star: Delta Orionis 
Date & Time: 12/25/98 9:57 pm CST using a micrometer reticle: 
Seeing: 7 <1-10 Seeing Scale (10 best)> 
Location of site: Killeen, TX (Lat 31 N, Elev 600 ft) 
Site classification: Suburban 
Sky darkness: 5 <Limiting magnitude> 
Telescope: Orion 6" Dob 
Magnification: 98x
 

Star: Delta Orionis 
Date & Time: December 4, 1999, 10:45 pm CST 
Seeing: 8  <1-10 Seeing Scale (10 best)>
Location of site: Killeen, TX, USA (suburban) 
Sky darkness: 4 <Limiting magnitude>
Telescope: Orion 6" dob 
Magnification: 48x, 72x, 98x 
 
 
 
 
 

Star: Delta Orionis 
Date & Time: 12/26/99 10:15 pm CST 
Seeing: 7 <1-10 Seeing Scale (10 best)>
Location of site: Killeen, TX (Lat 31 N, Elev 600 ft) 
Site classification: Suburban
Sky darkness: 4.5 <Limiting magnitude>
Telescope: Orion 6" dob 
Magnification: 32x, 48x, 72x, 98x, 144x 
 
 

Star: Delta Orionis 
Date & Time: 1/17/00, 7:38 pm CST 
Seeing: 7 <1-10 Seeing Scale (10 best)>
Location of site: Killeen, TX (Lat 31 N, Elev 600 ft) 
Site classification: Suburban
Sky darkness: 3 <Limiting magnitude>, Moon near full and near to object.
Telescope: Orion 6" dob with quickcam 
Magnification: --- 

First light for my new Celestron micrometer EP. Used it to measure the PA at 0 degrees and the separation at 51.57" for this pair. 
 
 
 
 
 
 
 

After several days of cloudy weather, this past weekend it cleared up and I had a chance to make some observations. However, on Saturday 
December 4, it was so windy that it was really hard to observe. I managed to get in one observation of delta Ori, the results of which 
are: 
Wide spaced but great magnitude difference makes this a tricky double. Primary is blue, secondary too faint to detect color. Separation 50", PA 
170d. 
 

Easily split at 32x. THe primary is a brilliant white, the much fainter secondary is blue. Wide spacing - the separation is 50" - make this an easy pair to split. PA 180 degrees. 

I agree with Penny, this is a pretty pair. 
 
 
 
 
 

Last night I went out to take some pictures of the moon with my "Astrocam" - a Connectix Quickcam modified as an inexpensive CCD device. (There was an article on this a couple of years ago in S&T, but the exact issue escapes me at the moment.) When through, Orion was up above the roof line and as an experiment, I turned my rig there. I first tried delta and was pleasantly surprised that the mag 6.3, wider spaced companion was visible in the image. I then took a pair of images without moving the scope to see if I could use these to measure separation and position angle. I also timed the transit of delta as it completely crossed the image window for calibration purposes. 

This evening I transferred the images from my laptop (Powerbook Duo 230) to my desktop (Performa 5200) and began working them up for analysis. First of all I opened the two images in Photoshop, and copied and pasted one into the other, setting the opacity to 50% so that the underlying image would show through. I saved this composite and then opened it with National Institute of Health Image. These images are 320 pixels wide and using this fact and my transit time I was able to determine a scale of pixels to arc seconds. NIH Image has a measuring tool I used to determine the number of pixels between the two star images. There is also an angel measuring tool that I used to determine the PA. This is were the composite "double exposure" came in. I measured the angle that the line connecting the two images as a calibration ( it was rotated just short of 5 degrees to the long axis of the image) and then then measured the PA of the pair itself, correcting this measure with the calibration figure determined as above. The results are as follows: 

Separation: 52.58", PA: 359d 54.2' 
These values compare quite well with published figures. 

This star was a beautiful double. The primary shone at about 2nd magnitude and was a brilliant bluish purple, with the secondary changing color from blue to 
lavender to red.  The com was many times fainter than the primary, 
and next to it, it looks "petite". 

I always like to use this star to "turn on" observers to star splitting. They will invariably look in the eyepiece, and I will ask them the color variation, and then 
they will start to describe it. I will then tell them they are looking at Mintaka, a belt star of Orion, and they will ALWAYS look up and say "Oh yea?" and look at 

the belt of Orion, to see if the double is visible naked eye.When see that it is not, and then they will look back at the eyepiece. Just a lesson, even for 
experienced observers, that the sky is not always what it seems. 
 

Other comments:  Very bright, wide pair.  No hint of the 14th magnitude C component. 

I set up my Pronto on an altaz mount, with a rifle-scope 6x40 as finder. The scope was fitted with a 2x TeleVue Barlow lens + Amici prism 90 degrees diagonal + TV Plossl 20 mm and 10.5 mm eyepiece. 

You know that the 2x power of the Barlow lens is an approximation, since it depends on the distance from the focal plane of the eyepiece and the optical center of the negative system. So the effective power depends on the mechanical construction of the eyepiece. 

If the distance of the eyepiece from the Barlow lens is increased (using a star diagonal between this two elements), so the amplification itself increase. By timing a star through a Micro-Guide eyepiece reticle, I have found that using star diagonal the amplification of the Barlow has a value near to 3.2x, so the focal lenght of the scope increase from 480 to 1530 mm. With the TV 10.5 Plossl I should get 146x, and with the TV Plossl 20 I should get almost 77x, so these are the values of the power I write in the report. 

The color of the second componend is difficult to say, but the contrast color is very clear. Obviously I didn't observe the 3rd component of mag. 14 

Observed coloration: main yellowish, second pale green or blue. 
 
 

Main component yellowish, second component green-bluish. 
 

In the image we can observe the main component, a blue giant, shining at magnitude 2.1-2.3 and the secondary, (also a blue star) of 6.3 magnitude located south from the main component. 

These stars are located 820 light years from us. Thir spectral class are O9-B0 and it’s an Algol type variable. 

This is a pretty and easy pair, with colors of White and bluish-white. 

Star A is an eclipsing binary with a 5.7324 day period. (The stars are at most only 5 million miles apart.) The AB pair is estimated to be 27,000 AU apart (almost half a light year). The primary is also an infra-red source. 

In 1904, at Potsdam Observatory, stationary spectral lines of calcium were detected, thus proving the existence of interstellar matter. There is also evidence of mass ejection at 1,800 km/sec. 

Measurements of 1984: 
2.3m (O9II) primary 
6.3m (B2V) companion at 52" in PA 359 
Both separation and PA appear to be diminishing. 
 

With this aperture, the two brightest components are child’s play to split. I remember I’ve split them in previous winters with a 10x50 pair of binoculars. The 14 magnitude component is left to considerable greater apertures. 
 

General Comment:This is a easy wide split between the primary and the secondary at low magnifications. I went up to 180X and 230X to see if I could find the third mag 14 component but no luck. Need dark skys and good seeing to get the mag 14 component. 

Star: Delta Orionis   
Date & Time: 1/29/00, 3:30 UT - 10:00 UT 
Seeing: ) 3 improving to 4 <1-10 Seeing Scale (10 best)>.
Location of site: Huntsburg, Ohio, USA
Site classification: Suburban 
Sky darkness: 4.5 (limiting magnitude)
Other observing conditions: 14 degrees F dropping to 6 degrees F, 92% humidity
Telescope: Meade 80mm/ f11
Magnification: 28x
 

could make out 6.3 mag star at 28x, didn't attempt 13.7 mag star 

d = 62.4-xxx; PA = 359-xxx 
Note: fainter third componente not observed.