Regulusastro Blog

Getting ready for the trip to Boulder for the annual meeting of the Astronomical Society of the Pacific (ASP), the awards banquet and visiting a slew of friends out there. Many people from the astronomical community and some family friends are going to be in the area: here’s to meeting up with as many of you as possible!

We will be bringing our beloved penguin, Frigid, of course. Paws maybe coming as well. Either way, you can expect to see the posts come in as they visit such places as the Boulder campus, the various museums and planetariums, as well as Pikes Peak and some geocaches as well! I hope the penguin can handle the high altitude.   Those now quite sure they understand who (what?) Frigid and Paws are, please jump here and enjoy.

Fiddling around with the spectrograph again today… the goal: to install the software, drivers and hardware for the guiding camera. The unit is a little, tiny, compact (did I say small?) video camera made by Watek and a USB video grabber. The AudeLA software has a built in module which can see the video from the camera as a webcam device. It then can connect to and control the telescope as any autoguider can. I like the idea: live video with autoguiding built in! This reminds me a lot of the webcam used in the Coude Feed Spectrograph at Kitt Peak, though I think their guide camera is an older TV-style imager. The systems pretty much works the same way: the video camera is focused on a mirror in the guide/imaging head attached to the telescope using a small lens system. The mirror has a 50 micron hole it it. The idea is to place your target (to be spectra’ed –> I know, it’s not a real verb) on that hole. The mirror then feeds an image of that star/planet/whatever, the hole and the surrounding star field for the guide camera to see. It’s pretty slick. This allows real time focusing, real time pointing, and a secure knowledge that you are grabbing spectra of the target of interest. No more trying to get that star on the invisible slit!

While I was playing with all that, I wanted also to try attaching a camera to the spectrograph to see the spectra in color. Why not? The lens used to bring the spectra to a focus on the CCD is made by Canon, and is an EOS standard lens. Sure enough, the Canon camera was able to bring the images to a focus. Here is a colorful sample.

Above is an image of the flat field lamp used to generate flats for later calibration. Nice looking rainbow there. You now get the idea of an echelle spectrograph: the orders at the top are the long wavelengths while the shorter ones are at the bottom.

Still playing a bit, the above is a spectra of the basement lights where I have this all setup. You can see the tell tale emission lines from the fluorescent lights used down there.

The above is my favorite: this is the calibration lamp spectra of thorium-argon. All those little lines have very well known wavelengths and allow each order to be precisely calibrated. Such fun!

To calibrate a spectrograph in terms of wavelength is one thing: get a lamp with known emission line wavelengths and use it to calibrate on a pixel-by-pixel basis the wavelengths of light coming out of the instrument. Ok – done. Thorium has been a good help here.  How to get the instrument’s response in terms of sensitivity to different wavelengths is a whole different ballgame, one that has proven interesting for some not-so-expected reasons.

Generally, the process is to take spectra of some radiator (a lamp) that has a well known spectral output in terms of intensities across all the wavelengths the instrument is designed to handle. This usually means taking some incandescent lamp and getting spectra of it. This lamp must have a continuous spectrum and be as close to an ideal blackbody radiator as possible. Tungsten lamps work well for this, as do some halogen bulbs. The key to blackbody radiators is that one can tell you their theoretical spectral curve if you know their temperature…. Planck and Wien were helpful here.

Trip to the hardware and home supply store: Lightbulbs. Incan-what? Descent? Incan – descent? Wha…?? All these places have gone UBER-green making it darned near impossible to find a well documented incandescent light bulb! I bought several types from several makers in the hope that at least one major company would have an available spec sheet for me to get the color temperature information that I needed. Sure enough: SYLVANIA soft white halogen bulbs have a convenient spec sheet available if you call their tech support. 2850K color temperature for their 28 Watt model. Awesome. I was out to win the race after all.

I took the spectrum of this little glowing heat-maker and got the instrumental response to what should have been a perfect blackbody curve. Now, CCDs are not the nicest of instruments. They are quirky. Mine like blue and far red. Green… not so much.

1. Take spectrum of lamp with the CCD at a known temp (-10C in my case for now).
2. Take a bunch more.
3. Average them.
4. Divide that spectral curve across the whole wavelength domain by the expected Planck curve for a 2850K blackbody radiator.
5. Spline this result to smooth out the rough features of the spectrum. The result is the instrumental response for the spectrograph at that temp across those wavelengths.
6. Use this newly created response curve to correct the recorded spectra of astronomical objects.
7. DONE!

And you thought that using biases, darks, and flat fields was bad!  The file maintenance here is a real game. So here are a couple of spectra for you to enjoy…. and yes, that have been calibrated for wavelength and spectral response of the instrument. Joy! Mission complete.

The above is the Hydrogen-Alpha region. Below is the Sodium Doublet. Look! Lines between the doublet of sodium. Cool resolution!  I am liking this instrument a lot. Note the rough area below around 5760: instrumental noise caused by a not-so-perfect-fit in the modeling of the field curvature for that particular spectral order. Tuning time!

The eShel spectrograph from Shelyak Instruments in France has arrived, and with it a lot of excitement about all the possibilities of projects for the future! The unit came into the country and stopped for a brief stint at an airport customs office before making its way here to Exeter. The box was about 45 pounds in weight and had a ton of individually wrapped goodies inside, all in excellent condition. Packaging was perfect and survived the trip from France without any issues.

Unpacking the unit is best done with a checklist and table nearby in a clean area. I have a very clean basement, dry too. The job was carried out there. Some serious time was spent learning the proper id of all the connecting pieces, some of which are not all that obvious at first glance. The majority were easy to identify: CCD camera and power supply, the optical head which attaches to the telescope, the fiber optic and power cables, the spectrograph and its lens… all easy enough. How to connect them? That is the fun part!

Here is the system completely hooked up and ready to go… with everything but a telescope for the little optical head. If you get one of these: note the use of the correct fiber cables for the starlight going into the spectrograph and the feed for the calibration lamps. The calibration lamp cable is larger than the 50 micrometer diameter cable for the starlight. Also note that the AC power goes into the calibration light box first, then is jumpered to the power supply for the thorium lamp which feeds a 10mA supply back to the calibration box. It is a little confusing, but the insides of the calibration box need power to handle logical switching directions fed into it via a com port. This brings up some interesting points: you need a PC with com ports.

The supplied software is an extension of the AudeLA package. The whole systems runs on top of that. It will manage your CCD imager (power and temperature), a guiding video camera, telescope guide control, the automatic on/off of the calibration lamps (yes, two: one is thorium for wavelength calibration, the other a white LED for flat fields! Cool!), the flip mirror in the guide head which allows either object spectra or imaging the calibration lamps, and the processing of all the final images automatically. It is pretty amazing. The setup is a bit tricky, but not bad. Make note: the software initially expects you to have already taken and formed an instrumental response FITS file… but you can’t do that until you have taken spectra of some standard star or blackbody radiator with a known temperature like a tungsten lamp. There is a checkbox to turn that feature off until you are ready. None of your object spectra will be calibrated automatically until you take care of this.

The spectrograph uses a Canon EOS lens to focus unto a QSI CCD imager (blue above). Focus is achieved by focusing the lens as you would any camera. No, it does not autofocus! The beauty of this design is that the spectrograph can reside 20m away from the telescope in a vibration free temperature controlled environment which makes for very sharp spectra and excellent calibration. Finding exoplanets using radial velocity measurements will be pretty easy with this!

The system is an Echelle spectrograph using an Echelle grating to make a merged spectrum first then is spread out using a secondary prism to break the orders of spectra apart for imaging. The result is an interesting and complicated field of many curved spectral orders. All this must be sorted out! Here is the spectrum of the sun (blue clouds actually) for example.

How to make sense of that!? Well, the software can take the calibration lamp spectrum of thorium and use it to identify the field curvature, the angle of the curves, and the wavelengths across the field: automatically. It then provides both individual spectra for each order and for the whole spectra combined.

Above are the spectra of the sun near H-alpha and then the combined spectra of the orders from about 500nm to 670nm. Note that the true blackbody curve of the sun is not evident here, because the unit has not been calibrated (YET) for instrumental response. We’re almost there! Once that is done, the wavelengths AND the flux values will be calibrated and the curves shall be accurate.

I have been working hard this week to accomplish those goals that need doing while classes are out and time is somewhat abundant. One of my summer goals was to get the robotic observatory mount to accept autoguiding signals from the STL-6303 imager. The mount, a wonderful (and I can’t stress that enough) 2001 vintage Astro-Physics AP1200, can go for 10 minutes without guiding, but after that, a guidestar is needed to keep stars round.

Here’s the kicker. The STL-6303 will guide the mount with the regular cable and such, BUT the hand control unit must be plugged into the mount. The mount needs that control unit to remind it of the guide correction speed (0.25x siderial). That makes it interesting: autostarting and parking become, well a more difficult and not remotely doable task with that unit plugged in. I have no idea why. So I have been playing with that a lot, much to my skin’s dismay as even 100% DEET makes no dent in protecting me from the Exeter River Mosquito Ranch (ERMR).

Last night I went out again, soaked in DEET (and with 50+ bites on the back of my bod from the night before) to see if things had mysteriously changes or if I had missed something. Interestingly, Astro-Physics (did I tell you how good that mount is?) keeps all their legacy manuals online for astronomers to access. Thank you, Astro-Physics. There Astro-Physics Website should you want it. In the manual for our mount, there is mention of a cool feature that other mounts have: the ability to park, shut off completely, then at a later time, reboot and the mount remembers everything: site, time, position, current siderial position, etc, etc. Hmmm, is that turned on? No. NO! Wow – funny how that was missed. I turned it on. No more parking problems. That is one hurdle down.

Now the second hurdle and the final one: how to get the mount to remember its guide correction speed? Funny: it started working of its own accord without ever having worked before! Well, fine. No idea why. Fine. Maybe (and this is not in the manual) the mount remembers this stuff when the “remember everything else feature” is turned on. Well, lucky me either way.

Now, I walk in, turn the mount and everything else on, and away we go! Night time is a better place thanks to all this….. and all this just to allow longer than 10 minute integrations! Sometimes I wonder why we go through all the pains. Because we want to! 

Summer is here and with it the opportunity to catch you all up with a few topics that have been going on and off again throughout the blog.

Fish: The two tanks are doing well. The monster tank with the new hunk of mopani wood has really shown marked improvement this past week. The wood has lost 95% of the hazy gooey mold-like fuzz that I was apprehensive about earlier. The Synodontis has been eating it. I like it, if he likes it. The other tank occupants are happy, too. pH is at a nominal 7. I am running about 4tbl of peat pellets in the canister, so the system is pretty stable and has taken on a lovely dark tan color of black water Amazon. My favorite occupants now are the aggressive and lively black tetras which eat voraciously and like lightning.

The smaller tank with the angels is also fine. It’s a bit more acidic at 6.8 with a new piece of mopani and a lovely tan color as well. Plants in there are growing well, and the Amazon Sword has overstepped its bounds and is trying to do what it always does: leave. No way. I like that plant. It’s staying.

I have been making large progress on my astronomy text. Today I finished the section on spectroscopic parallax. I have been fining the largest difficulty to be the illustrations: I either have to find open source and uncopyrighted works, ask for permission to reprint with modifications and my own copyright, or make my own. I have been making a lot on my own and have become quite the whiz at technical drawing using Adobe Illustrator. This dog can and does learn new tricks.

Biking: Time to BBQ and relax a bit. I have been getting on the road bike between uber hot and wet days. My normal jaunts are about 15 miles, and I average that in about an hour or a little less. There is one good hilly section which keeps my breath going. I hope my heart keeps it up! The bike has been treating me well with the saddle change and stem change last summer. I do not feel all that cramped any more and the saddle is, well, a huge improvement. No more sore…. you get the picture.

Playing at the Domes: I am embarking on a journey into radio astronomy… again. I had initially gotten into this a long time ago (1988) with a friend, Steve Choate, while living in Amherst, MA. We built a simple tube type dipole for 10m with a chicken wire reflector. The project suffered in that we never had a sensitive enough (nor quiet enough) receiver. The antenna this time around is a full dipole for 10 and 20m with a simple yagi style reflector wire underneath for a beam aiming, simply enough, up. The receiver is a Yaesu FT1000mp from my shack. I figured I could put it to good use in radio astronomy while using my ic-756 pro III at home for ham play. Using a wide receive mode (AM), we should be able to get at least the Sun, the central Milky Way and interactions between Io and Jupiter. We’ll see! If all else fails, it makes a cool ham shack.

Painting and home ownership: We’ve almoist finished painting the interior in Northwood. The ceilings up the stairs and in the two bedrooms are the last to do. General touch ups will be needed, but the place is looking really good. We tore out the old now unused HO train table in the basement to make room and recycle the wood. The broken and messy parts? Into the burn pile. The mice in the observatory: dead thanks to poison. Trapping and being kind just did not work. Sorry guys. Some times a rodent just has to go, and they were making a big mess in the dome between leaving droppings and nut shells, and then wrecking the cables and fiber feeds. Bad mice. Gone now.

Oh – geocaching: We hid our first geocache this last week in the woods off of Drinkwater Road in Exeter: Astrocache1. Go seek it. A few people already have been by and signed the log. The trails there are well kept and can be walked or biked. Bugs: bring repellant. A link to the geocache entry for you here.

There: that should keep you all posted for a while.

Well, the washing and soaking of the famed mopani wood has gotten the tank to a point where nothing has changed!   It is what it is: a happy tank with a funny piece of wood with a slimy mold(?) coating its surface. I would say that about 75% of the wood’s surface has a 1/4” thick coating of this:

Well, whatever it is, all the main chemical features of the water are well within the norm: pH is 7.0, GH and KH are low, Nitrates and Nitrites are 0ppm, temp is 83F, and tannins are nice and even. The occupants are happy, with the exception of this guy:

This is such a lovely discus, but he has not eaten one scrap of food since he arrived. The LFS’s discus were also not all that healthy – We offered this guy a home, but it looks like he’ll not make it through the week. All the others are eating voraciously and like kings. We’re talking mid-tank food, flake foods, brine shrimp and blood worms. What more could a fish want? Well I even tried crushed lettuce, algae and peas. Nope. This guy is having none of it. Alas.  The good news is that all other fish and plants are just fine. The other tank is also at 100%. No issues. With time, this slime, too, will take care of itself and either vanish or be eaten by occupants.

I guess we’ll have to write a new tune called “The Mopani Wood Blues” given the trials and tribulations of this week’s focus on my larger aquarium. I got this wonderful (WONDERFUL!) piece of mopani for my black water Amazon tank. I like that tannin thing with all the dark brown colorations: it makes the tank look realistic and helps to keep the water soft and acidic the way the fish like it. Two days after installation, the tank took on a lovely dark tone:

This morning the mopani had a healthy coat of slime (clear gel) all over it. I suspect a fast growing fungus from the wood’s intention to rot, as good wood should. This piece is huge though. It’s not the size to fit in my 5 gallon pot, or a bucket…. I could not boil it like I normally would. This is the result: one dead fish, a slimy mess and a lot of cleanup work.

1. Wood removed and placed in bleach water solution in my bathtub. Yeah. Yuk.
2. 8 Gallons of water flushed out of the tank and dead fish removed. I got as much slime as I could out.
3. Drained the bathtub and replenished the water with fresh warm water and a mix of Stress Coat to reduce chlorine from the bleach and house water supply. Let it sit for two hours. Scrub, repeat, rinse, scrub, repeat.
4. Replace wood in tank.
5. Clean out the canister filter: added some carbon (I hate to use it) and some ammo-carb just in case things gets to cycling again.
6. Sit and wait.
7. I will let you know!

This is not for the faint of heart. You need to know how to use a CCD imager and your telescope. I write this here, because there are so many websites with INCORRECT information about this process. Some miss the point completely. All this does is mess with your head and mess with your gear. This method works. Trust me.

Polar Alignment with CCD

This is for permanent installations, as it can take up to 3 or 4 hours to complete the whole process to the point where your mount is perfectly polar aligned. The result is that you no longer have to worry about declination drift during imaging. You still have to worry about periodic error from your mount’s drive, but any good autoguider will take care of that. These instructions assume that you know how your CCD is aligned on the scope (which way is N, E, S, W on the images). In all cases, you will be monitoring North-South changes in a star’s position on your CCD images. IGNORE any east-west drift.

Polar Axis Altitude Alignment:

1. Manually polar align your mount to the best of your ability. Some mounts come with polar alignment scope in the polar axis shaft. Use it! This will actually get you close enough to take 5 to 10 minute integrations without doing the rest of this list! You will depend on your autoguider.

2. Aim your telescope at a star low on the eastern horizon and on the celestial equator (close is good). Faint stars are ok. You do not want them blooming.

3. Take 15 30-second long integrations of that star. Some people prefer to take one 5 minute long shot of the stars to see its path, but it works just as well to see the star’s position move due to drift via snapshots. DO NOT move the mount in any way during these shots. Just let the RA motor do its job.

4. Now to fix your drift! In this step you move the mount’s permanent polar axis depending on the way the star has drifted on your images.

a. If the star drifted north on your images, then move the mount’s polar axis down a tiny(!!) bit.

b. If the star drifted south on your images, then move the mount up a tiny(!!) bit.

5. Repeat steps 2 through 4 until you see NO DRIFT in 5 minutes. Want better? Go for longer. You will find that you can use the centroid tool in your image processing software and get excellent results in about 30-40 minutes.

Polar Axis Azimuth Alignment:

1. Aim your telescope at a star on the meridian and on the celestial equator.

2. Take 15 30-second long integrations of that star. Some people prefer to take one 5 minute long shot of the stars to see its path, but it works just as well to see the star’s position move due to drift via snapshots. DO NOT move the mount in any way during these shots. Just let the RA motor do its job.

3. Now it is time to fix your polar alignment’s altitude to perfection! Be sure to make VERY SMALL adjustments to the polar axis at this time.

a. If the star drifted to the north in your images, then slightly move the mount to the east.

b. If the star drifted to the south in your images, then move the mount to the west.

4. Repeat steps 2 and 3 above until there is NO DRIFT in your 5 minute series.

Congratulations! Your mount is polar aligned. You will likely not need to adjust this again until you swap out telescopes, have an earthquake (more common than you think!) or someone fiddles with a knob or two on your mount (also not all that uncommon as you think).

Happy Birthday Kate!