Wednesday, July 15, 2015

performed full double star imaging run

Readied for my double star measurement imaging run.

Target: Rasalgethi.

SETUP

Ensured the Sony ICD SX 750 D audio recorder was running.

The ASUS netbook John Repeat Dance was connected to the external widescreen monitor. The Windows extended desktop was activated. SkyTools 3 Pro was running. The imaging Rasalgethi observing list was active. All the objects were selected together and then plotted on the Interactive Atlas.

Attached the Canon DSLR to the Celestron 14-inch f/11 telescope with t-ring and 2-inch nosepiece. Connected the camera to the netbook via the special USB extender kit. The endpoints were interconnected by a long ethernet cable passing through the port between the Warm Room and the observatory floor. I coiled a small piece of red film around the adapter to attenuate the bright blue LED. Then connected the adapter at the pier to a small DC power supply.

Started the Canon EOS Utility application and switched to Live View. Increased the exposure time. Set the ISO to 1000. Left the white balance in daylight.

Of course, the Paramount ME was connected to the Dell laptop and TheSky 6 was driving. Opened the motion controls dialog box.

Over the course of the run, moved the roof and adjusted the south walls to reduce the wind.

FOCUS

Slewed to Unukalhai aka α (alpha) Serpentis as a bright star to focus on. Centred the telescope on the star first using the Tele Vue 101. Used the mechanical focuser to coarsely reach focus. Slewed the Paramount ME slowly to centre the star in the camera field.

Grabbed the Optec TCF-S hand box to fine tune. Desperately wanted to focus electronically at a computer monitor. Alas, I put the flat screen on a box (the NOCO box!) and turned it toward the window. Using the keypad on the mount, I was able to focus while viewing the screen.

DECLINATION ALIGNMENT

Readied to square the camera body to the celestial declination axis.

Moved Unukalhai off the edge of the camera field, the left or east edge, turned off tracking, and gauged the angle of the path across the camera field. Turned the camera coarsely in the opposite direction.

The camera was upright. Therefore, in all photos north is up; east is left.

All photos are the same scale.

Moved α Ser off the field again and let it drift across to the right or west. Measured the duration for the star to run across the long edge of the field. Approximately 1 minute and 20 seconds.

Moved back to the starting point. Noted the point, where TheSky 6 thought it was pointing. RA 15 43 37.72 by Dec +06 28 33.37. I would use the Move To command to return to the spot again.

Programmed the EOS Utility for an 80 second exposure. Started shooting and turned off the tracking.


12:25 AM. 80 seconds, tracking off. Interesting the little bumps in the line. Flaws in the gears, wind, vibration through the ground? All of the above?

Carefully turned the camera about 1° in the opposite direction again.

Decided it would be easier to gauge the angle if it was not in the centre of the field.

Nudge up the time so I would not have to rush...


12:32. 85 seconds. Bingo. Looked nearly perfect in alignment.

EOS Utility requires that an imaging run have 2 shots, minimum. Initially, I didn't want it to proceed so I interrupted the software after each exposure was completed. Then I returned to the start point, using the coordinates, and then restarted everything. Too much manual effort. On the fly, I realised I could optimise the process by using a random start near the starting point. Programmed the imaging to shoot the remaining 8 exposures with a 35 second gap.

12:56. The imaging computer proceeded hands-free; I just reacquired the target star at the starting area on the mount control computer after the shutter closed.

Listened to the wind... And stared at the images. Nearly straight streaks of star light. With tiny bumps and waves. I thought of plots of music or sound. Sinusoidal waves. Suddenly, I realised it was! It was the same. I was seeing the oscillation of the 'scope, the silent vibration.


1:08. A particularly strong gust manifested itself in one frame. Noisy wind.

Now the camera was not touched. No changes in orientation.

CALIBRATION

Readied to capture a dozen fixed double stars to validate the image frame size.

All images, for display here in the blog, processed slightly in Canon Digital Photo Pro. 

Slewed to Marfik, the Marfik that is κ (kappa) Herculis. Centred. Shot exposures: 30, 15, 5 seconds, ½ second, 1/8th, 1/30, 1/60, 1/125 of a second.


1:16. Marfik A and B. 30 seconds. The C star is obvious to the south or below. Stars look the same colour to me; the Observer's Handbook describes them as yellow and red.

Imaged HD 151070. Exposures: 30, 4, 2, 1, and ½. Vibration or shake in all!


1:38. HD 151070 A and C. 30 seconds. B is extremely tight to A, not resolved.

Shot Sarin aka δ (delta) Herculis. Exposures: 15, 8, 4, 1, ½, and ¼.


2:01. Sarin A, B, C, and D. 8 seconds. Spectacular. A fascinating arrangement of stars.

HD 148979. Exposures: 15, 10, 5, 2.5, and 1.


2:06. HD 148979 A and B. 10 seconds.

HR 6169. Exposures: 1 and ¼.


2:14. HR 6169 A and B. 1 second.

HD 150933. Exposures: 10, 8, 4, 2, and 1.


2:19. HD 150933 A and B. 8 seconds.

HR 6341. Exposures: 10, 5, and 4.


2:29. HR 6341 A, B, C, P, and Q. 4 seconds. Very interesting!

It occurred to me there was no reason to shoot the target star at the very end. In fact, as SkyTools was guiding me, it was best to work from west to east. See below the TARGET section.

[ed: It also makes sense if conditions worsen. Get the moving object while you can. The static reference stars can be done later. Even another night.]

2:32. Started imaging Rasalgethi.

2:41. Finished.

HR 6594. Exposures: 1, ½, ¼, 1/8, and 1/15.


2:43. HR 6594 A and... 1 second. B is very close to A. C is very faint. Probably not a good choice... I also don't know I didn't shoot a longer exposure.

HD 157789. Exposures: 30, 10, and 5.


2:49. HD 157789 A and B. 10 seconds.

V451. Exposures: 10, 5, and 2.


2:54. V451 A and B. 10 seconds.

HD 159481. Exposures: 30 and 15.


3:04. HD 159481. Wow. A, B, C, E, G, H, I, and J. 30 seconds. Wow! I knew this would be a fun one! The F star, north-west of A, is visible if you zoom in.

HD 161164. Exposures: 30 and 15.


3:11. HD 161164 A and B. 15 seconds. B is the faint star very close to the blue-white, at the 10 o'clock position. The orange star is variable V964.

HR 6758. Exposures: 15, 8, and 4.


3:15. HR 6758 A, B, and C. 8 seconds. Moth eyes!

POU3251. Took 3 shots, all at 30 seconds. I had to shoot blind as I could not see the faint target stars on the monitor.


3:22. POU3251 A and B. Barely visible.

TARGET

As noted previously, it occurred to me to image the target star in sequence rather than waiting to the end. I changed the plans on the fly to capture it as it came up on the ST3P observing list.

Rasalgethi, aka α Her. Exposures: 15, 10, 1/8, 1/15, 1/20, and 1/30. The B star was visible at 1/8 and 1/15; C and D were nowhere to be seen. It looked like the seeing tanked...


Image above was shot fast. 1/15th of a second. A and B are visible. According to ST3P, magnitude 3.1 and 5.4. The Observer's Handbook describes these as red and green and very tight. Yes, no, yes.


Slow. 15 seconds. D is obvious at the 10 o'clock position. I believe C is just visible at the 2 o'clock, in the glare of the A and B stars. Certainly this star looks red, when blown out like this.

CLOSING

This was a very fun exercise! Gained lots of experience. Established a good workflow. Remote control focusing will improve things. I will hopefully gain insight as to when I should, or should not, use a doubler. I suspect this particular target is too tight to measure accurately. I need to learn the parameters of what I can do given the equipment I'll have access to. And there's a threshold for brightness too.

A fringe benefit that I was not expecting: rapidly adding to my double star life list.

I think it's fair to add these to my life list. My assessment of the stars, their colours and positions, is no different than if I was looking through an ocular. I had viewed Marfik, Sarin, and α Her before; that's 12 more systems observed!

LESSONS LEARNED

Use the doubler or 4X. Or at least be ready to. That will be a factor of the target and how tight the pair is. I think conditions will play into this too, that the predicted conditions will need to be very good or higher for extreme magnification. This also reminds me that I don't think I've ever had success with the Tele Vue 4x Power Mate. But that's probably because it is such a small field...

Plan B. This also suggested that I have a backup plan. Given that the C14 is not in my backyard, I have to take whatever the weather gods give me. So if I arrive the CAO and the seeing if spectacular, I could go with tight binaries. But if it is average, then should have a wide-pair as a backup. Ah. A rainy-day activity: build observing/imaging plans in advance.

Keep shooting until a clean shot is captured. Maybe I was tired or rushing but I could have used more frames for some of the calibration stars, not to mention the target itself. So, shoot more. Especially if it is windy (and vibrating the 'scope). And if the seeing is off.

Have a look! If it looks like the system might be interesting, have a look in the Tele Vue refractor. I saw many new doubles during this run but looked at them through the camera! Since the TV101 is pointing at the same spot, go have a visual look. I might find some good candidates for the certificate list.

Turn on the grid. Should turn on the grid in the camera software during the drift alignment. Moving the star near to the edge of the frame is good but the gridlines will help.

NEXT STEPS

Reduction of the data. That will start with confirming the frame orientation and image scale. And then, finally, measuring the position angle and separation.

§

Wikipedia links: kappa Herculis, delta HerculisHR 6594, and alpha Herculis.

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