Sunday, March 31, 2013

collected double star data (Toronto)

7:45 PM, March 30, 2013. Stepped out onto the porch. Hmm. High cloud... Everywhere. Wisps here and there. In the north. In the south. South-west. Might not be good tonight... Still, if it fair, or even improved, I'd be ready. Tonight I wanted to do some imaging.

Fixed the centre post under the black light blind. It had fallen over, again. Should figure out a way to Velcro it. Was happy to see I had not lost any clothes pegs. Moved the laptop outside.
Instrument: Celestron 8-inch SCT
Mount: Vixen Super Polaris
Method: slewing and tracking with IDEA GoToStar
9:18 PM. The camera was ready. Battery grip attached. Seemed heavy. AC adapter installed along with a battery (although I don't know if the battery works, or rather, can be used). Laptop John Kim Chi already outside. Not worried about dark adaptation. Back in the kitchen but without the netbook John Littlejohn. Reinstalled the CF memory card in the camera. Need to put some socks and shoes on, and a sweater. Planning an imaging run. Of a double star. In particular, Castor. I intend to take a bunch of pictures.

It is unclear from the JDSO articles on using a DSLR to image double stars the exact workflow. Both Michaud's and Berko's articles have left a lot of questions for me. But I think Berko shoots lots of still photos of the same star and then adds or averages the photos perhaps in REDUC. Which is not unlike capturing video and using the individual frames.

9:21. Skies looked OK. I realised the Moon would rise later tonight. About 45 minutes? More wiggling room. Maybe that would give me time to capture a second subject, maybe another faster mover, like Alula Australis? That said, I didn't want to go too crazy. This was all somewhat experimental.

It occurred to me now, tonight, in planning prime focusing imaging, that I'd need a decent polar alignment. Considering the challenges last night, I considered going "back to the basics." Align the mount the way I know how, using the polar axis scope.

9:23. Logged into Kim Chi. The air felt damp. I put a sweater and toque on immediately. Removed the bungee from the tarp.

9:25. Telescope uncloaked. Towel under computer to prevent sliding on deck box. Took the camera and camera power supply out.

Considered the quick review last night of the GoToStar system start up and alignment. After I found and copied the 4-page guide, I noted it referred to the park position. And that while parked, the 'scope would be pointing to NCP. So it looked like my assumption was correct. Counter weight shaft down and vertical. Eyeballing it. And I was setting the Dec axis to 90°. I had been doing this crudely or quickly last night but maybe I was off a bit. Or completely wrong. What did not make sense though was when I did my first full trial, I was getting very good goto pointing. Why did it not work well last night?! Every target was off. Everything was off by about a degree... Tonight I wanted to confirm where the park position is.

9:28. Eyeglasses on. Headed out to do the polar alignment. Old school. The Vixen way. For March 30 at 9:30 PM.

9:30. The SCT corrector cap fell off when I rotated the OTA quite far. And as it started to fall, I tried to catch it but missed, and proceed to touch two fingers to the glass. Damn it! Clearly, the little mod I made to the cap was not enough: in the cold the cap is still shrinking and there's not enough friction. I need to apply more layers. Or come up with a completely different approach...

9:33. Moved the voice recorder outside to the telescope tray. This time of year made for a very interesting orientation of the mount. I had to disconnect the power cord and watch the clearances. Very tight.

9:36. Used my red portal flashlight to illuminate the reticule. Yesterday I had put Polaris in the left side of the field of view. But tonight, the reticule was showing that it needed to be to the right. And, at the moment, nearly horizontal. I put it just outside the big circle, accommodating for recent precession. Put the Dec at 90 and the RA vertical.

9:40. Realised that if I could see Polaris in the telescope, I'd be near NCP. It was in the finder. I moved the telescope in RA and Dec. The RA axis looked like it was about 15° off, standing at the north, looking south, it was tilted to the right. The Dec was at 88. I set the moveable RA scale ring to zero. Thing was stiff. This would serve as the temporary park position indicator.

[ed: That was probably a mistake. Polaris should not be centred.]

Polaris was swimming. I wanted to have a look-see of the double. No way. Heat off the roof? Clouds I couldn't see?

Done with the eyeglasses.

9:45. Checked settings in the hand controller. The date and time: 3/30/2013, 21:45, Daylight Saving Time On. Site: west 79 28 50 by north 43 39 15, 300 minutes behind UT. Northern hemisphere.

Decided to do a one-star align. Using Aldebaran. It was way off! It was closer to Betelgeuse or Meissa. Crazy.

9:47. Got an idea. Figured out which button activated the RA motor and used only it to slew back to Aldebaran. Uh huh. This loose theory was confirmed. Aldebaran showed in the finder scope, very near the centre. There was a problem with the RA axis; the Dec was fine. I kept wondering if it was a time issue. Then I wondered if there was something wrong with the Daylight Saving Time calculation. Couldn't remember if my first full test was before or after the DST change... What if I turned off the DST option? I returned to the park position to begin the experiment.

9:51. Interesting. Polaris was back in the eyepiece. Turned off the DST option. Did not power off.

9:53. Began a one-star alignment again. Curiously, it did not give Aldebaran this time; so it was Betelgeuse for the test. And it was off target. It didn't seem as severe. But still...

New idea. Not a DST problem; it is a problem with the park position. I just had to find it...

Went back to the park position. Took a peek at Polaris. It looked better. Yeh.

Reinstated the Daylight Saving Time option. Repeated the one-star align. Once again, it offered Aldebaran. Accepted it.

9:56. Released the RA clutch and put the telescope on the star. Uh huh. Very close. Then I refined the position with the keypad. When I hit Enter on the keypad, it returned me to the main screen. Behavior I had not seen last night. No "error" report. Which leads me to believe if the altitude and azimuth error is large, one sees the error report. Getting somewhere!

Chose the park position command. I wanted to know what it thought the location was. The Dec was back at 88. And the RA was nearly vertical. I moved the RA ring to set zero at the new position.

[ed: But forgot to note the delta!]

9:59. Now I wondered what would happen with a full-test. Powered off. Requested a two-star alignment. Aldebaran was first. Discovered the battery dead on the ring light. Aldebaran was in the centre! For the second star I selected Pollux. It was behind the tree branch, damn it—I had to guess at the location. Thought I had it. Received an RA error report: altitude 11.9 higher and azimuth 28.8 east.

Stumbled across it before but deliberately accessed the help system, for the page keys. Unfortunately, they didn't work in the Named Star number list.

10:04. On Castor and tracking. Right on time! OK. Now it was time to prepare to image. Realised I didn't have the Bahtinov mask for the 8". Tried the mask and focused.

10:05. Bumped the computer power cord and it went down! Flaky cord. Crap. Twisted the end, right near the 3 prong plug and it came back. I looped it under the power bar and it looked stable.

10:09. It occurred to me, with my SCT, that I could use either the old Meade SCT t-adapter, bolted directly to the visual back of course, or the new 2" nose piece, shoved in the Tele Vue SCT adapter. I elected to use the nose piece. It would be faster to install. And it would allow faster camera rotation, if necessary.

Removed the eyepiece. The nose piece was a little finicky to install.

Huh. I noticed the 2" eyepiece and 2" mirror were heavy. The camera didn't seem so much compared to them.

10:12. While Kim Chi booted, I installed the data cable at the camera. Had to Shut down unnecessary apps, Evernote, Dropbox, Magic Disc. Flash tried to update. Received a "camera not recognised error."

10:21. Rerouted the cable, at the camera, to change the strain. Disconnected and reconnected. EOS Utility finally came up on the correctly. Put the camera into Manual mode. Returned to the computer. Set the white balance to daylight, set the format to Raw. Opened Live View. Couldn't see anything. Started playing with the exposure settings.

10:26. Took a 2 second shot. I could faintly see the out of focus Bahtinov mask. Continued toward focus taking shots until I could see it in the Live View.

10:37. Settled on ISO 1600. Tried a 15 second exposure. Unfortunately the A and B stars were very bloated. Tried 4 seconds. Very good. But decided 2 was best, to balance the A and B but still see the C and D. And I'd minimise tracking and vibration issues.

from IMG-2487, scaled, unprocessed, 4 seconds, ISO 1600, w/b daylight, N at top-right, E at top-left, C star south of AB, D star west of C

10:40. Panned slightly at 2x to better frame. Set up a timed run with a 30 second start delay, 15 shots every 60 seconds, using the current 2 second setting. Left the porch.

10:51. Checked on the rig. Everything was moving along. Wondered about tracking and drift or PEC issues given that I wasn't doing guiding. But I was taking very short exposures. And hopefully the software would help me correct things, if necessary.

Returned to the office. Checked the star fields in SkyTools. Which was good. I was getting mixed about all the neighbouring stars. While I was on Castor in Gemini, I kept thinking of Tegmen in Cancer, with "the house," with the E and G stars. And the potentially fast moving B star: that was 38 Gem (down by the foot).

Looked up the data for the 4-star system, α (alpha) Gem. The period of the A and B stars was 445 years. A reliable orbit. The current separation, as of February, was 4.88". It also showed that a = 6.59" but I had to look up in the help for the definition of a: semi-major axis.

10:58. The image run was complete. Readied to shoot 15 darks. The image run dialog showed the previous settings.

11:02. Looked up the weather info, back in the office. I heard it was going to rain... The Clear Sky Chart, as of 8:27, had improved. It showed good conditions through to 2 AM. Weird. Transparency goes worse at midnight, seeing stays level, Moon becomes a factor at 1. The Weather Network applet showed partly cloudy, 6°C. The quick EC RSS for PIA clear, 6.9°, increasing cloudiness, low plus 2. Sunday rain, high of 8. From the EC main page. Current conditions, 101.7 and falling, 5.5°, dewpoint -4.5, humidity 48%, wind light S at 9 km/h, as of 11 PM. Forecast issued at 3:30 PM, clear, increasing cloudiness overnight, low plus 2. Rain tomorrow. All this meant I'd have to do a tear down tonight. Checked NOAA. Ah ha! Hear it comes. In fact, it showed I would lose the skies sooner... Very soon. Fast clouds from due west.

It occurred to me the clouds were going to knock me out. I should change the imaging sequence: stop the darks right now and collect light frames on 38 Gem. Started to record the RA and Dec in Evernote but it pissed me off. Wrote down the J2000 coords for the star on paper. Headed to the porch.

11:07. The dark run was about half-way. Stopped it. Checked the OneWorld weather station: 1008, 29%, 5.4°. Fired up Live View again.

11:09. Slewed to the star. Spotted it in the finder, about a degree away. Fine tuned. Returned the computer and started trying different exposures. Panned slightly.

from IMG-2516, scaled, unprocessed, 4 seconds, ISO 1600, w/b daylight, N at top-right, E at top-left, A and B split

11:14. Returned from the office after verifying the target. Settled on 4 second exposures. Set up the imaging run. 15 lights at 1 minute intervals.

11:15. Received a CSAC email alert. It noted 10% cloud. Good for double stars. Considered emailing Berko for details of his imaging runs. Wondered if I should read more JDSO articles.

11:20. Played with SkyTools. Switched to the 40D field. Had to decrease the exposure value to decrease the stars.

Wondered if I have set up the telescope view settings incorrectly in SkyTools. I think it was a posting on the Yahoo!Group that started me thinking down this line. And I think it is only becoming apparent now that I'm adding camera choices in the software. I've specified the SCT telescope produces a laterally inverted field, when in fact it doesn't. Two reflections. It's the mirror diagonal that does the additional flip. I'll have to explore this a bit...

11:24. Checked for Nancy. Counted whiskers and claws. Checked the computer. Heard the camera shutter. 10 lights were done.

I considered doing more. But realised I really didn't know what I was doing. This would probably be enough data for testing.

Looking forward, if I want better results, I'll need to do more accurate polar alignment. And probably do drift alignment. And get, once and for all, Backyard EOS. Back in the office, I skimmed again at the (brief) user manual. The GoToStar has a PEC option, can display the polar axis error, etc. And I should look in the Yahoo!Group for the "advanced" options. Need to learn more about two- and three-star alignments.

11:32. Check Stellarium. Oh oh. Looked like I'd be in the trees. Sent a message to David about the comet. He hadn't seen it. But didn't indicate what he used... I reminded all it was around magnitude 4.5 now. Headed to the porch to shoot darks.

11:33. Run was done. Looked up: ooh, clouds! Probably the final frames were pooched... Started the darks run, 4 second exposures. While the telescope and computer worked, I started the tear down.

11:39. Started to remove the big light blind. Considering that light entering the back of the camera, I installed the ocular cover. It's still amazing to me how well the shield works.

11:48. Considered throw the long fabric over the edge of the porch... Instead, dragged it part-way into the kitchen.

11:54. Started the shortened final darks run. Considered removing the OTA but discovered the data cable was snaking through the mount.

11:57. Four to go.

12:00 AM, March 30, 2013. The last photo was captured. A photo of black.

12:02 AM. Gracefully closed down the software. And hibernated John Kim Chi before I bonked the cable again. I need to fix that cord...

12:04. Brought the camera in. It was cool. Stood it on the eyepiece tube to try to keep the moisture out of the guts. Positioned a prop so it wouldn't fall over.

12:08. Shut off the recorder.


Noticed the red incandescent bulb in the living was throwing a lot of yellow light to the ceiling... Red colouring faded. I wonder if they can be "painted..." Dipped?


An "unknown quantity" for me is knowing what Berko did to determine the angle of the image. Was I supposed to do some drift images?

Huh. Just thought of something. Be easy to do a "full" drift pattern. Shoot a super long exposure (at a low ISO) and let the stars drift across the whole field... Hmmm. And don't turn the camera, of course.

Huh. Wonder what you'd get if you did a medium ISO...


Overall, that was kind fun. Two back-to-back nights. Visual observing one night. Imaging the next. Learned lots about the GoToStar system. Hopefully got some usable data so to measure the double stars.

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