Etalon Engineering Run 2014Jun

This CHARA run is for installing and testing the Etalon.

by John Monnier

I arrived on 2014Jun07 with the hardware. I discovered a small clearance issue -- the edge of the mount clipped V6. see image below

Media:etalon_clearance_problem.jpg

Laszlo kindly trimmed off the extra hardware and moved the mounting points over 3 inches. Now it is fine.

Keith Johnson joined me on Jun 11 (I had a Jun 9 keck run to attend to). We did a number of tests and discovered the chara beams were heading down at about 0.5 degree angle -- we had shim the mount to account for this so that the etalons were near-normal. All of the etalons are normal to beam within about 18" or so -- usually better. We measured by putting in a target with hole and looking for the spot upon reflection on a target. We used steel shims from Laszlo.

We did some tests in the lab to confirm that the system was working as expected. on UT2014Jun15 we aligned MIRC with the PRISM and used B1B2 with etalons 2.000 <-> 2.006 (see engineering logs) and the data seemed to show good correspondence with expectations. We also tried 2.000 <-> 2.012 for B1 and B2, but we did not have adequate spectral resolution to see the phase modulation.

Next on 2014Jun16 we aligned using the R150 GRISM. there was a clearance issue and so couldn't simply 'move' the spectrum into the correct quadrant. So we had to the 'flip quadrant function.' Our final setup was: 48 252 100 2 4 500 500 which gave frame times of 13ms (Ok). We repeated the same experiment as previous day using a dx=6mu and dx=12mu etalon along with calibrations. For fun we also found the secondary fringe packets -- by tuning the retro by 2mm X 1.46 we found fringes with extra dispersion .. also for 4mm X 1.46

I analyzed the 2014Jun16 data carefully and found good correspondence with theory.. see:

Media:Etalon_analysis1.pdf

Next we came up with an observing strategy for the run.

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mu boo (cal: gam her). mu boo was a target in PHASES with no astrometric motion. Good test target.

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v819 Her (cal: gam lyr). v819 her is a perfect test target from Mutterspaugh thesis. bright, up in june, 100mu-as motion with 4.4 day period, separation <~100mas.

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kap peg (cal: sig Cyg). kap peg is another great test from MUtterspaugh thesis. separation is larger 100-250mas (150mas for our current run). astrometric mtion of B is 1.0 mas motion over 6 day period.

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note that S1 is out of service with broken drive gear but we can use the others.

Beam order is W1-S2-S1-E1-E2-W2 (standard mirc beam order)

Original Plan

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mu boo. 8:30-9:30. POPs 31524 (all pops are ordered S2W1W2E1E2).

gam her . 9:30-10:15

gam her + etalon. 10:15-10:30

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v819 her. 10:30-12 POPs 21523.

gam lyr. 12:00-12:45.

gam lyr + etalon. 12:45-1:00

v819 her 1:00-2:30; (POP change 23513)

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kap peg. 2:30-3:30 (POPs 21523)

sig cyg. 3:30-4:15. (POPs 22513)

sig cyg+ etalon. 4:15-4:30.

kap peg. 4:30-5:30.

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sunrise

on 2102Jun15 we got our first fringes on sky and realized that our sensitivity was tough under seeing conditions of r0<15cm. We could detect all fringes for Kap Peg and v819 Her and gam lyr. However we could not track Gam Lyr with etalon in... we took data with etalon by taking advantage of the low piston and good baseline model. We would setup the fringes w/o etalon. then quickly remove etalon and take 30 files. we would then remove etalon, zero out the fringes, and repeat. We were able to take >100 files this way we hope can be used.

Because of the lower sensitivity we decided to explore the use of lab measurements to calibrate the wavelength. Each day starting on 2012Jul15 morning and the next 3, we took fringe data using white light source on all the neighboring pairs (b12,b23,b34,b45,b56), both w and w/o etalon including full shutter sets.

we decided to start each night with the full set of fringe data and in the morning afte robserving to just to 2 of them as a check for drifts (B12, B45).

Note after first night (2014Jun15) we changed etalon order from 0,6,12,18,24,30 micron to 6,30,0,18,24,12 micron. This former order was not optimal because all the alb fringes had the same delta etalon thickness of just 6 microns. In order to better sample the range of etalon thickness during lab measurements, we changed order to 6,30,0,18,24,12 micron which is the only solution that has each neighboring beam with a different thickness and also that maintains beams the etalons in beam4,5 (18,24 mu) to allow comparison with the data from 2014Jun15.

From 2014Jun16,17 we used the latter etalon setting.

We also updated our plan for the last 2 nights to remove mu boo and all cals except gam lyr. we adjusted POPs a bit to otimize time.

NewPlan

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white light lab fringes on all pairs, w/ and w/o etalon

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v819 her. 9:40-12:30 POPs 21523.

gam lyr. 12:45-01:2-. NO etalon

gam lyr + etalon. 01:20 to 2:00.

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kap peg. 2:30-5:15 (POPs 32523) (at beginning of this and end we lose a telescope).

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white light lab fringes on B12,B45 (w, and w/o etalon)

sunrise

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oh one more thing. before the last night UT2014Jun16, we purposefully changed the spectrograph alignment moving the imaging doublet lens. Then re-optimizing by hand. I hope/expect to see eidence of a wavelength shift in all different beam pair analysis based on the etalon white light lab data we took that night before observing.

Now one odd thing I noticed taking data, especially on Kappa Peg on last night. The MIRC GDT would, for some baselines, track on the weaker fringe packet of the wide binary. This is because the separation is so big taht is it bigger than the OPD capture range on the mirc GDT. I could see this because there would be one weak fringe with E1 (for instance), and then if I clicked over like 50 microns, all of sudden BOOM we'd get all th eother fringes very bright..This could be a serious systematic and need some thought how to deal with it.