Friday, March 25, 2011

StellaCam testing (Toronto)

It was looking clear and the Moon was not rising until about 1 AM so I decided to set up to testing of the StellaCam3.
Instrument: Celestron 8-inch SCT
Mount: Vixen Super Polaris
Method: star hopping
I wanted to select stars at or near the zenith and see how sensitive the CCD camera was without the integration or accumulation settings enabled. This, so to explain why I had trouble seeing stars in the camera and video at the Long Sault Ludmilla occultation (of a mag 11.4 star)...

I also wanted to smooth out some other kinks with the rig.

5:00 PM, Thu 24 Mar 2011. Shovelled the porch of snow and erected the tripod. Put the table and observer's chair outside. Moved the Celestron 8" Schmidt Cassegrain telescope outside to the deck box to begin cooling. Began the assembly of an observing list in SkyTools3, including Polaris for alignment, and some galaxies in Ursa Major for fun. Then, prepped dinner.

9:00 PM. Whoa. It was a lot brighter out on the porch now that they fixed the street light across the road... Damn. I may need to implement my light shield barrier idea sooner...

It was getting cold. Put on my winter coat. Fortunately, there was no wind.

Aligned to NCP using SkyTools hints.

Phil and I talked on the phone. He wanted to know if I would join him at the Earth Hour star party on Saturday at the Ontario Science Centre. He was looking for someone to share a 'scope. It was what I needed to hear, to push me over the edge. We talked about which one to use, timing, etc. I told him I'd be there at 7:00 PM to help unload and set up!

10:17 PM. I chased down the star PPM 50856. It is classified as a "neglected" double star in the Washington Double Star catalog. Used the "SkyTools way" of "hopping" to a star. Wow. Fast. I found the little kite-shape with tail. The bottom star of the diamond was the target star. It was faint! Well, they were all faint. I had started with the baader planetarium Hyperion 36mm 2" eyepiece but then, after fitting the 1¼" adapter, I moved up to the Celestron Plössl 26mm and finally the Meade orthoscopic 18mm, yielding 111 power. I could not split with faint star. I headed inside to review my notes.

Oh... the companion is magnitude 12. The separation was doable at 5 seconds of arc but I didn't know if I'd be able to see the second star given its brightness.

I was buoyed in discovering that the final star in the kite's tail, TYC 03417-1368-1, was mag 11.9. I was seeing that without difficult. I thought that not bad from the porch, on a bright street, new light and all, car headlights, reflections everywhere, with my poor eye dark adaptation!

Checked my life lists for magnitude limits. Well, I didn't break records. It February two years ago I was getting the same number, from both High Park and from the backyard on Evelyn Crescent. Without all the lights around, I bet I could get deeper tonight... The sky was very good.

10:22. I noticed Manuel had popped into the RASC Toronto Centre chatroom and said hello. We chit-chatted for a little while. Told him what I was up to. He said he had obtained a new camera. Invited me over for imaging (tempting me with yummy coffee). I asked if he was going to OSC party. He said he was planning to. I gave him some pointers. As I headed back outside, I urged him to do some observing.

10:35. I bumped the power to 222x with the Tele Vue Nagler 9mm. Wow. I still could not see a split of two stars although the target star looked fuzzy... I dunno. I didn't think I was clearly seeing the companion. I think I will need to wait for dark skies, when I get down to mag 13.

11:40. Well, I solved some problems... Not able to split that star but I made some progress in other areas.

When I first powered Denis's occultation rig, I found the image on the little Oslon monitor was terrible. I couldn't see anything. It was flipping and jumping. I pressed the Menu button—no change. I pressed the AV button but that didn't work. Wondered if it was a loose wire. I had never seen it so bad. Unusable.

Frustrated, I went inside to fetch a deep discharge 12 volt gel battery.

The entire occultation rig is powered by a single cigarette lighter adapter (CLA) plug which is split, inside the carrying case, to three feeds, one for the CCD camera, one for the Kiwi time-inserter, and the other for the LCD monitor. I had (like the last time on the porch) plugged in the kit to my custom 120VAC-12VDC adapter. This triple-socket CLA receptacle was shared with the Kendrick dew heater controller and the Vixen motor drive. The power supply was plugged into an extension cord from the kitchen. I wondered if the combination of things—AC input, dew PWM controller, and motor-controller—was producing the tremendous interface.

When I had the kit at Long Sault, obviously, I was on battery power. But I deliberately put the motor and heaters on a battery separate from the occultation rig. No interference issues then (just other problems).

When I have tested the occultation equipment to learn it and when I had it at the CAO, it was on AC power. No major interference issues then.

Plugged the occultation rig-in-a-box to the heavy battery and powered up the monitor. Perfect! Nice clean image. Ah... It was a good, clean, stable picture! I could easily read the Kiwi time values. There was no stripping or banding.

Somehow, in my panicked poking at buttons, I had set the monitor to PAL format... I put it back to Auto.

The next thing I worked on was to get the 26mm ocular (in the long shaft of the Vixen flip mirror) to be parfocal with StellaCam camera (in short/straight-thru tube, of course). I recalled trying to move the eyepiece before and quickly observed that moving it out made it worse. So, I tried moving the camera.

It worked! As I slid the camera outwards, the focus began to match the eyepiece. I continued moving it out. Then I went beyond the detent position. Not ideal but hey... After a few attempts, I found that with the camera about 5 to 6mm beyond the detent groove offered a good solution. It was a compromise. Still not perfect but passable. At least I would have visible stars monitor based on a visual focus setting. No more hunting.

Finally, I started playing with, and paying more attention to, the integration and gamma settings on the AstroVid control pad.

With integration on setting 1, the "lowest," and gamma on medium, I could see mag 10 to 11 stars. If I went the gamma off, there were no stars. If I changed to the "high" setting, level 1, no stars. In all cases, I had the gain setting at maximum, or nearly so.

These target stars were at 71 degrees altitude. There was no moon.

This was a little disappointing. But at the same time illuminating. I had simply assumed that the StellaCam3 could punch into the sky deeper than I could visually. I actually wonder if I can see better than the camera...

I re-read the StellaCam documentation. It's not great, it's not really clear. I wanted to get a deeper understanding of the integration and exposure setting.

The 6-page manual says that one would set the frame dial to high speed shutter mode (labelled HIGH) for planetary, lunar and solar imaging. "The shutter speeds are labeled HIGH 1, 2, 3, 4, 5, 6. They correspond to shutter speeds of 1/60, 1/125, 1/250, 1/500, 1/1000, and 1/2000 second." That made sense.

And this corresponds to the label plate on the bottom or back of the control pad. The HIGH option shows parenthetically "SEC," presumably meaning seconds (or rather fractions of a second). Also, the 1 setting shows E: 1/60 and C: 1/50. I think the E is short for EIA (the North American NTSC standard) and C means CCIR (the PAL or overseas standard). And the numbers appear to refer to the number of fields per second. Not sure what that means in the broader context but I don't think it really concerns me...

OK. Next paragraph:

In accumulation mode, the SLOW settings are used. This setting is "used to integrate timed exposures within the camera. The box is labeled OFF (1/60 second mode), 1, 2, 4, 8, 16, 32, 64, 128, 256." Um, what box? I think this is referring to the freeze option.

Does that mean the freeze "off" setting is 1/60th of a second, unless you start pressing the Start/Stop button?

Back to the labelling: the face of the control pad, around the frame dial, opposite the HIGH settings, is simply marked SLOW 1, 2, 3 and so on up to 9. The numbers referred (128 or 256) to are not shown on the dial. On the back, yes, on the info plate, the values are shown:

1 1
2 2
3 4
4 8
5 16
6 32
7 64
8 128
9 256

"These (values) are equivalent to the number of frames that would accumulate for a corresponding exposure time." Right. So, set to 5 and 16 frames aggregate to produce the image. Effectively increasing the sensitivity 16 times.

But how long is each exposure? 1/60? Assuming that, then setting 7 or 64 frames, means the exposure is about 1 second long. Setting 8, approximately 2 seconds; setting 9, 4 seconds.

I found it curious that the setting HIGH 1 seemed to worse that setting SLOW 1. And the freeze option also seemed better than the HIGH 1.

And what exactly is happening at SLOW 1. Is that 1/60 or something else?

Is the documentation that I have for a different controller?!

In the end, I need a "live" setting for occultations. But I am not clear if I should use HIGH 1, the in-between setting, or SLOW 1. Looks like I'll need to do some more reading. Or maybe query the folk on the StellaCam Yahoo!Group.

11:56. I double-checked settings and configuration. I was pointing almost straight up. At the high speed shutter mode of 1/60 (setting 1), I seemed to be, from a city street, at the limit with this camera. I could detect mag 9 to 9.5. Only the mag 9.45 star HP 43545 aka SAO 42579 was visible.

Now I can choose occultations accordingly... Well, maybe I can help when (157070) 2003 SG307 occults TYC 0164-01394-1u!

Testing done! Let's image something. Oooh. Maybe Bode's or the Cigar!

12:06 AM, Fri 25 Mar 2011. Just imaged M81. Tried the SkyTools way of finding it but struggled with so few marker stars; switched to traditional methods. Took me a very long time to find it!

Fortunately, I remembered why. When moving the finder scope, twisting it, it goes out of alignment. That's what happened to me at Long Sault. So, when I recalled this, I realigned. Then I found the galaxy quickly.

Gain: fairly high, about 2/3rd. Integration: 9. Gamma: off. Recorder: Canon Alura 80. North is down; east is right.

The galaxy is huge. It should fill the whole frame. Maybe I'll try stacking some of the video frames.

1:12. I tried to locate M82. No luck. I was getting tired...

I briefly considered viewing and imaging Saturn. Checked the location in software. Well up. Eyeballed it from the porch, through a big tree. But suddenly didn't feel like doing any more. I especially didn't want to start facing into the street lights...

1:26. Done tear down. Experimented this time to wind down a bit faster. Left the observing chair and AV table outside. I also did the telescope tear down differently: I left the OTA attached to mount. It was quicker; but the entire assembly is quite heavy.


Alignment was very good for the evening. Seeing and transparency were rather good.


Wikipedia link: Messier 81.

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