Weather

Not totally clear – supposed to be “mostly clear” until about midnight, then clear.  Some lines of cirrus were visible across the sky near sunset and the entire western sky was “milky” white at sunset, so transparency not great.  Winds around 5mph or less, temps in the low 70s, fairly low humidity, decent to typical seeing (~2 arcsecs).

Rig #2:  V1101 Aquila

V1101 is definitely fainter tonight (not just because of the thin cirrus).  Running 60-second exposures.

9:40pm – definitely lots of cirrus across the sky.  Variable transparency made obvious by brighter background in some images

Well, it stayed mostly clear until about 12:50am – then lots of high cirrus.  Done at 1:00am.  Here’s the plot for the night – pretty ratty!

 

Weather

A second really nice night in a row!  And of course rig#1 is still down for repairs!  Lows tonight around 65F, clear (but not quite as clear as last night) calm winds – seeing even now is better than 2-arcsec.  Expecting dew tonight so DON’T FORGET TO KEEP DEW HEATERS ON!

Rig#2:  V1101 Aql & HT Cas

Another night on this object.  Meridian transit at about 11:05pm, will hit the trees around 1:00am.  So I’ll see what Joe Patterson is suggesting for late night targets.  30-second exposures, V1101 is bright, perhaps not as bright as last night.

V1101 got into the maple tree from hell at around 1:00am.  So I decided to give HT Cas a try.  Seems HT Cas is quite quiet these days!  After a few dozen 30-second exposures I decided to bag it – out at around 2:30am.

Data Reductions

Earlier today I got caught up with current projects – two nights of V1101 Aql reduced and sent to Joe Patterson – three nights of spectra of WR 134, 135, and 137 sent off to Noel Richardson.

Added August 25th:

I got the data reduced the following morning.  Here’s a plot.  Nice sinusoid!

 

Weather

Surprise!  At 4:00pm this afternoon it was raining.  Just before sunset it started clearing off, and just when the skies became dark enough the final clouds slipped past Altair.  Cool and very clear, seeing about average, lots of dew, not surprising considering it rained earlier today and the temperatures have fallen quite a bit.  Low tonight around 65F.  Calm winds.

Rig #2: V1101 Aql

V1101 is very bright tonight, so I set the cadence for 30-second exposures.   I managed to forget turning the dew controller back on – so the corrector plate became about 30% covered in dew by the time V1101 slipped behind the maple tree.  Shut it down at about 1:10am.  Really nice night but I’m tired.  Need to start looking for a late-night target.

Rig #1:

I got a call from George at Astro-Physics this afternoon.  Both the motor and encoder in the declination assembly for the AP1200 are being replaced, plus they’re adding a static discharge protection circuit to lessen the probability of damage in the case of nearby lightning and so on.  Another $500, but I should have it back by next week.  With the exception of the “Y” cable this mount has now had its entire electrical system replaced.

Rig #2:  V1101 Aql

The heat has returned – but despite a full moon this is quite a nice evening.  Warm, humid, calm, really good seeing (maybe 1.7 arcseconds).  Low temp tonight only about 75.  High tomorrow 90.  Meridian crossing at 11:22pm tonight – so only good until about 1:30 when V1101 will begin to pass behind the maple tree.  Need a late-night target….

Rig #1: Down for Repairs

The declination motor assembly has been returned to Astro-Physics for repairs.  It appears the encoder and perhaps motor need replacing.  Another $500 repair.  So that $6500 AP1200?

• Original cost of mount $6500
• Upgrade to CP3 electronics $1050
• New Piertop Plate from Dan’s $130
• Three counterweights $725
• Dovetail Clamp $165
• 1612FSA $140
• Replace RA motor and encoder: $600
• Replace Dec encoder ( &Motor?)  ???

So far, not including whatever the current repair bill will be, total is $9310.  And to be honest I think the had controller is going to need replacement as the buttons on that don’t seem to always work as they should.  Woof!  That’s a ton of money for an 11-year old mount.  Clearly it’s time in Florida was not kind to it.

CLOUDS!  10:50pm, re-acquired target on other side of meridian at around 11:40pm.

CLOUDS AGAIN!  12:10am.  I’m done!

Maxim DL Troubles

There is just no single thing more annoying with Maxim DL than it’s inability to find and guide on an obvious bright star in the guider.  Setting aside other issues such as Maxim’s utter ignorance of half of the numerical universe (it does not recognize and truncates to zero any negative number) it just befuddles me that the program cannot find an obviously bright star in the field and guide on it.  Tonight gave me a clue, however, as to why it has troubles.  Because it was a full moon night and because the guider is fairly far off the optical axis there was a fairly strong gradient to the background.  It appears that this fools the guider into thinking it is looking for a really big star just off the edge of the guide box.  So it looks like one solution might be to fully calibrate the autoguider camera so that a flat field image can take that gradient out.  Still, if there was some way to limit the size of object the guide program was looking for that might be a quicker solution.  Something along the lines of DAOPhot’s star finding algorithm, using a “lowered gaussian” idea.  But then that means the user has to know the fwhm of stars as seen in the guide camera.  Anyway!

 

Testing the “power” of LHiRes guider optics

Two nights ago I took spectra of each of the three WR stars (Wr134, 135, & 137) at different locations along the slit as seen in the guide camera.  Each star was consistently imaged at a particular location along the slit:

• wr134 at x=120
• wr135 at x=160
• wr137 at x=200

I was trying to see if location along the slit made any difference to the “shape” of the profile of spectral traces.  That is still under review, but on thing I could determine without any ambiguity is the “power” of the guider optics.  The shifts, above, resulted in the spectral traces falling along different rows in the imaging guider as follows:

• wr134 at y=184
• wr135 at y=217
• wr137 at y=250

Basically a shift of 40 pixels along the slit as imaged in the guider results in 33 pixels of shift in Y in the imaging camera.  The imaging camera’s pixels are binned 1×2 – so in y = are 18 microns.  The guide camera is being used in 2×2 binning mode, so each binned pixel is (7.4*2) = 14.8 microns.  The ratio of physical pixel size is 18/14.8 = 1.22 .  Also note that 40/33 = 1.22.

Said a different way; 40 pixels of shift along the slit as viewed in the guide camera = 40*14.8 = 592 microns, resulting in a shift of 33 * 18 = 594 microns in Y on the imaging chip.  So the relative power looks to be 1.0.

 Thoughts on the profile asymmetry

Last night one of the spectra of of Beta Aquarii was focused using the ghost image which appears below the actual stellar image in the guide camera.  Basically I focused to get that ghost as sharp as possible.  The resulting spectrum was a bit of a mess, as might be expected.  Here’s a trace in Y across that spectrum:

 

This is similar to what I’d expect of the telescope was badly out of collimation.  So one thing to try might be to rack the focus to either side of best focus to see if the shape inverts itself.  Since the slit is oriented essentially E-W, if the problem is collimation then I should be able to gently tweak the secondary collimation screw that is parallel to that axis (if there is one) to see if it improves.  Depending on how clear it is tonight I may just try both of these experiments.

Weather

Really clear and cool, very nice night.  Seeing better than 2 arcsec, low temp around 60F, some dew so fairly humid once temp gets down near 60, very little wind.  UPDATE:  This is just one spectacularly nice night!  Too damn bad the ‘f-ing’ AP1200 had to shit the bed.

Rig #1 – More troubles with AP1200 mount

It appears that the encoder in the declination assembly may be fried.  Just a guess but it exhibits a few familiar symptoms:  (taken from email sent to George at Astro-Physics)

1)      I turn on the mount.   The speed setting shown on the hand control is 64.  If I press N or S the declination motor runs very fast for a very short period of time and then stops.  The yellow light comes on.

2)     This occurs whether I am using the hand control or the computer/APV2 driver, and occurs whether I have both or just one of the computer and/or hand paddle connected.

3)     Anticipating one of the tests the AP guys might suggest I swapped the cables going to the RA and Dec motor assemblies.  Note that when I do that the RA cable being connected to the Dec motor, if tracking is on the Dec motor immediately goes to high speed as soon as the power is turned on.  So, turning the tracking off, if I press the N-S buttons the RA moves as expected.  Pressing E-W causes the Dec motor to run and stop.

4)     So I swapped the cables back to their normal positions.  Note I also tested all of the pin-outs on the “Y” cable with a continuity tester and it seems to be just fine.

5)     After swapping the cables back to their normal positions I noticed a strange behavior.  I had removed the declination motor assembly and was holding it in my hand.  I set the move speed to 0.5x sidereal and pressed N – the dec motor began running at a fairly slow speed (but much faster than sidereal – maybe 1 rpm).  It would not stop – lifting my finger from the N button did not cause it to stop running.  Pressing the N button again, however, caused the motor to run faster.  In fact with each press of the N button the motor ran faster and faster.  So I pressed the S button and, sure enough, the motor slowed with each additional press of the “S” button until I was able to get it to stop, then with the next press of the S button it began moving slowly in the opposite direction, again moving faster with each additional “S” button press.

6)     All of the above was true whether using the hand control or the move buttons on the AP v2 Ascom GUI.

7)     All the above was done using CP3 electronics (with firmware “S”).  I still have the CP2 electronics that the mount came with (firmware version “E”).  So I tried the same tests using that box and got largely the same results – though instead of the dec motor stopping almost instantly, with the CP2 electronics it would run for a second or two before suddenly stopping.

8)     I also notice that the encoder itself is noisy – that is, if I open up the spur gear box and remove one of the gears so that the motor is not turning the encoder it is much quieter.  The encoder makes a sound almost like the bearings were bad?  If that makes any sense!  It reminds me a bit of what the RA motor assembly sounded like before you guys worked on it, replacing motor and encoder back in May.

9)     Looking at the RA and Dec in the v2 Ascom interface on the computer I noticed that even when the declination motor is running there is no change being shown in the declination readout.  Moving the RA causes the RA readout to update as expected.

Of course this throws a huge monkey wrench into the WR program.

If getting this fixed costs as much as getting the RA assembly repaired I will have paid more for a used AP1200 CP2 than I would have paid for a new AP1200 CP3.

 

Rig #2:  V1101 Aql

Ironically the mount that the AP1200 is supposed to be replacing is working just fine.  Thank god!  Joe Patterson urged I try hard to get as many nights of data on this object as possible, so at least having one rig operating keeps me sane!  Anyway, Joe mentioned the need for good data from this longitude to fill the gap between Europe and the west US.  Anyway, 75-second exposures.   Got about 180 images.  Out at around 1:55am.

 Results from tonight’s data

Shown, below, is the light curve for V1101 from August 14/15.  Pretty decent signal-to-noise, but notice the jump in the comparison star’s light curve.  Two possible causes come to mind.  First, it could be due to poor flat-fields contaminated with scattered light.  The ~0.03 magnitude jump seems a bit much for that to be the case, especially since I can select a bunch of images from a few nights and combine them, filtering out the stars, and get a very flat background.  The biggest issue with scattered light in flat fields (from what I understand) comes from the fact that the color of the flat source (in this case twilight sky) and the actual night sky are different.  The reflectivity of the inner surface of the baffle tube is quite different at different wavelengths.  But if that were the case I’d expect that the combined science images described above would show some sort of gradient – and something changing a few percent over a small region would be VERY evident.  Which leads to the second possibility and that is variable PSF shape across the image.  The technique used to reduce the data is called “optimal extraction” and uses a model PSF derived from a bright star in the image as a weighting mask.  The technique is very sensitive to changes in PSF shape – so if there was, say, a lot of coma it might cause the effect seen.  Again, though, a 3% difference over a small difference in location on the chip seems large to me.  Perhaps a third explanation – bugs in my software?  More investigation needed!  Anyway, V1101 was a bit fainter tonight and that allowed the relative variability to be more obvious.

Weather

Clear and cool – unseasonaly cool – low expected to be around 62F, 74 at sunset, humidity 50%.  Some clouds are supposed to pass through early.  We’ll see.  Seeing is average to slightly above, maybe 1.8 arcsec.

UPDATE:  Clouds rolled in around 12:30am or so.  Got two full cycles of the WR stars before shutting it down.

Rig #1:  WR134,135,137

See if I can get three full cycles!

Rig #2:  V1101 Aql

This guy is much brighter tonight than the other two nights I’ve observed it.  Running 30-second integrations and still getting S/N well above 100.

 

Issues:

Had trouble getting rig#2 running.  Somehow everything lost communication with the mount, so I disconnected all software from the mount, exited NexRemote, turned mount power off then on, reconnected NexRemote and did a cold start (find switch, etc.)  First attempt failed, turned power off/on – second attempt succeeded, but in finding switch the mount ran a long way (20 degrees?) in declination past switch before stopping and returning.  Found position an all was well.  Hmmmmmm.

Weather

It was the very best night of the summer so far.  Virtually could-free, fairly haze-free, with steady seeing and light wind.  Temp was 72 > 65F,  humiditiy around 65%

Rig 1:  WR134,135, & 137

This was likely the last night I could get a full set of three spectra for each target.  Due to a screw-up I wasted about 30 minutes getting the third wr135 spectrum – so never did get the third WR137.  I still cannot figure out why spectral traces are skewed in one direction.  Tonight’s data and those from the most recent previous night both await new flat fields.  Not 100% sure they’re needed – but would not hurt.  I tried running the camera at -15C but it just would not go that low, so I ended up getting -14C bias and darks.  Not even sure the camera was at -14C throughout the night.

Rig #2: V1101 Aql

A newer target from Joe Patterson, did a sequence of 1-minute exposures.  Also got new flats – use them for tonight’s and the most recent previous evening’s images (also of V1101 Aql.

Weather

Shooting through haze and thin clouds for most of the evening.  Supposed to clear off for a couple of hours after midnight.  Desperate for a clear night!  75 > 70F, humidity 70%, light breeze.  Update – cleared off around midnight – middle of second wr135 spectrum.

Rig #1:  WR134, 135, 137

I spend some time last night dodging clouds and re-collimating the telescope to see if that is what is causing the asymmetrical spectral traces – to no avail.  Collimation seems not to be the problem.  Not sure the data tonight will be high enough S/N due to the thin clouds, but seeing is actually pretty good and I’ve managed to maintain pretty good focus.  Hopefully that can compensate a bit for the thin clouds.  11:52pm as I type this and the clouds do seem to be thinning somewhat.

Rig #2: V1101 Aqr

I’ll likely follow this object for the next few weeks.  Joe Patterson requesting long runs on this star, a “negative superhumper”.  Like with rig #1, not sure these data will end up being useful.

All in all a pretty good night – no major issues – set up darks for -10C on each camera.  Out at 3:12am

 

Weather

Three clear nights in a row?  Not until it’s over do I believe it – besides, both of the previous nights included cloudy periods.  Hot today – mid to upper 90s, tonight 86-80F, humidity 65-70%, calm winds.  Seeing looks t be a bit better than 2 arscec.

As per each “clear” night recently – some clouds did move through, this time just as I was beginning the third time through the sequence of WR stars.  So I quickly moved to Beta Apr and got a couple of spectra there (one poorly focused).  Waited out the clouds (45 min?) then resumed.

 

Rig #1:  Spectra of WR134, 135 and 137.

Three sets – 30 min each, plus a visit to Beta Aqr.

Rig #2:  J191502+071947

100 second integrations.  With the moon moving towards full not sure how many more nights of this object, which is beginning to flirt with 17th mag.

 Focus, asymmetrical profiles

So tonight I kept every spectrum at column 180 on the guide camera.  I tried to focus before each spectrum, by maximizing the peak pixel value.  Still, the traces were badly asymmetrical.  In fact, for the Beta Aquarii spectrum I tried focusing on the “ghost” image that appears just below bright stars (internal reflection in the glass slit).  Fail!  Not surprising – but the resulting cut through the spectrum clearly showed the image was out of focus – double peak which would indicate being far enough out of focus that the shadow of the secondary mirror is visible.  After that I changed tactics and tried focusing to achieve the smallest FWHM.  That seems to work pretty well, but still the profiles are asymmetrical.

One fairly interesting thing I’ve noticed is that as things cool off I have to “raise” the mirror – to push focus back farther.  Now with just a camera the opposite is true.  Makes sense since falling temperatures causes the aluminum tube to shrink – so to keep the focus at the same place I need to move the mirror back so that the focal plane moves toward the front of the telescope, compensating for the shrinking tube.  So why is the spectrograph different?  Perhaps it’s thermal expansion and contraction is larger than the telescope’s?  Not sure what the body of the instrument is made of but I’m guessing steel.  Wonder what it’s coefficient of thermal expansion is compared to Al.

Out at 3:45am – left darks running on Rig #1.