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Thanks Daniel!!!

Those answers are very encouraging....

Could you look over the last optical diagram and comment on the angles?
The angles are;
Parts laid out on 28 degrees.
Slit is 15 degrees.
Fold mirror is 60 degrees.

28 degrees is an OK value?

Thanks again for returning to this thread and commenting on previous ideas and questions. It has helped with this puzzle.
Steven

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Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven

The angles seems to be okay.
Can you reduce the 28° ?

_________________
Daniel P. Sablowski

https://www.kunstmann.de/buch/axel_hack ... 42000/t-2/
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Hi Daniel,
Looking at the Excel diagram it appears that I can change the parts angle to 26° but then the 40mm achro holder will need to be milled. The 200mmf3.5 has enough clear aperture to further distance it from the grating so the achro holder does not need milling but then camera the gets possibly too close to the telescope tube wall or the focuser as it will have the Nikon lens mount and therefore need room to rotate, and, possibly the 8-position filter wheel which permanently mounts to the ST-8300 body.

What benefits are there for a reduced angle 28° to 26°? I noticed the resolving power did not change significantly, but how does reduced angle help? Also, what angle does the grating sit at relative to the parts angle?

Thanks, Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven

A decreasing angle increases the efficiency but 3° are not much and 28° is ok, if the geometry prevents a significant reduction of the angle.

So, the layout should be ok.

_________________
Daniel P. Sablowski

https://www.kunstmann.de/buch/axel_hack ... 42000/t-2/
https://dpsablowski.wordpress.com
https://github.com/DPSablowski
https://www.aip.de/mitglieder/dsablowski/

Is it possible, for calibration light, to mount a fiber optic cable along a spider vane and at the location of the secondary mirror then point the fiber end towards the primary?

Thanks, Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

You will loose a lot of calibration light in this way (and you need a very strong lamp).
Think about a direct coupling of calibration lamp on the spec (mirror system) or about the mounting of the fiber on the spec over a suitable mirror system. For example see http://spektroskopieforum.vdsastro.de/v ... php?t=3369

_________________
Herzliche Grüße / best regards

Lothar

https://lotharschanne.wordpress.com/

Thanks Lothar, that's a very interesting way of introducing the calibration light. The link is appreciated!

So does anyone make, or can it be built, a 12VDC calibration light source? I've done some searching and I've found the Filly lamp articles, no Filly lamps for sale.... Even if it's a higher voltage, what cheap lamps are commonly used and still available? I do have a 120VAC EPROM Eraser mercury vapor lamp, if that's of use.... Would a Xenon vehicle headlight work?

On another note, does anyone have an extra 4-Position Slit (15/19/23/35 µm) with support from Shelyak? I figured I'd ask about this before the time comes for ordering it.

Thanks, Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven

A xenonlight will work for flatfielding, because you need a continuum. For wavelenght calibration you need a spectral lamp. Neon lamp fitts very well. This is included in socket splitters or these smal night orientation lamps.

http://www.technik-und-elektronik.de/mi ... 11825.html

_________________
Daniel P. Sablowski

https://www.kunstmann.de/buch/axel_hack ... 42000/t-2/
https://dpsablowski.wordpress.com
https://github.com/DPSablowski
https://www.aip.de/mitglieder/dsablowski/

Thanks Daniel,

I had seen the use of mixed emission calibration sources, presumably two or more lamps because of gaps in the range of usable lines, so could Neon be used alone? Is it advisable to also include an Argon light source?

Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven

Best wavelength calibration sources are hollow cathode lamps (HCLs). I have made a little catalog with spectra of different HCLs:

http://www.spektroskopie.fg-vds.de/pdf/ ... ki2011.pdf

Those lamps are sometimes sold by ebay.

Neon is only usable for the red end of the VIS.

Mixing calibrations sources is possible and a single argon lamp is better than a neon lamp.

Following link could be helpful:

http://bmauclaire.free.fr/astronomie/sp ... index2.htm

An spectra of such a smal neon lamp is attached.

_________________
Daniel P. Sablowski

https://www.kunstmann.de/buch/axel_hack ... 42000/t-2/
https://dpsablowski.wordpress.com
https://github.com/DPSablowski
https://www.aip.de/mitglieder/dsablowski/

Thanks, those will be helpful!

I had found Buil's callibration page on HeII 4685.7A for Delta Sco and it became apparent that many lines are needed on the chip for calibration. Neon is very well populated in the red and Argon in the blue, hence my original mention of Xenon since it's a literal forest of lines across the entire visible spectrum. I've not found a cheap Xenon discharge lamp yet.

Since the next campaign in 2013 is the HeII 5411A line in WR134 and the CIII 5696A line in WR135 (plus HeI 5876A in each star), with my estimated 560A of coverage on the ccd chip I plan on centering on 5661A. This gives me a range of ~5381A to ~5941A. Using Argon seems to have few bright lines to calibrate so Neon may be the better choice there, yes?

I'll probably build a dual lamp, Ar/Ne, combining them in some fashion and an achromat to feed the fiber optic cable that leads to the spectrograph. It seems I'd be set from blue to red you think, or will green still be an issue?

Thanks again,
Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven

As you can see in the picture neon2.gif (see above) neon has not enough lines in the spectralrange you has mentioned. I think you have to try both neon and argon. The "same" lamps (same element but different manufacturer) can differ a little from each other.

Good lamps are HCLs with argon filling but they are rare.

_________________
Daniel P. Sablowski

https://www.kunstmann.de/buch/axel_hack ... 42000/t-2/
https://dpsablowski.wordpress.com
https://github.com/DPSablowski
https://www.aip.de/mitglieder/dsablowski/

Hi Daniel, Steven
It is possible sometimes to find Argon lines even in Neon lamps (from contamination) but they can be weak so need longer exposures. There are also weak Neon lines that show up in long exposures. Here are some that I have found useful
http://www.threehillsobservatory.co.uk/ ... opy_12.htm

There are also decorative "filly" lights with various mixtures of Ne, Ar,Xe,Kr but they are difficult to find now.
http://astrosurf.com/buil/calibration/lamp1.htm
The filly "dot" lamp is particularly good for high resolution work as it contains all the gasses. See Thierry Garrel's spectrum here
http://gabalou.canalblog.com/archives/2 ... 13833.html
but if you use a lamp with multiple elements and many lines, take care that the line you are using is not a blend of more than one line at the resolution of your spectrograph.

Other possibilities are:

Use Tellurics where they are available and strong enough (good for H alpha and Na D regions for example)

Determine the dispersion equation of the spectrograph using a solar spectrum as a reference and use just one reference line (from a lamp or a telluric) at the at the time of aquisition of the target spectrum to define the offset

Cheers
Robin

Hi Robin, yes, they are rare, I searched and possibly found one Filly lamp, but as large as they are I decided to go with the GE AR-3 and NE-45 lamps, each in a reflector which then is collimated with an achro into the ends of a bifurcated fiber optic cable. The single end then will then feed the spectrograph. A small acromat just inside the spectrograph will focus it before the moveable fold mirror then folds it toward the slit.

Does the calibration light require the same f4.5 angle as target light when it hits the slit?

Thanks for the links to the calibration line pictures. It's nice when pieces of the puzzle come together....
Steven

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Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven,
I do not think it is that critical but you might get slightly more accurate result if you match the FR of the lamp beam to that of the telescope so any asymmetry in the spectral lines caused by limitations of the spectrograph optics are faithfully reproduced in both star and lamp spectra. I do know with the LHIRES (which has a simple neon indicator lamp which swings into position in front of the slit) that the exact positioning of the lamp over the slit can cause small shifts in calibration (I see only a small effect but Lothar Schanne has seen larger effects) so I think it is a good idea to try to keep the geometry of the calibration light as close to that of the star light as possible.

Cheers
Robin

Thanks Robin, that helps alot.

For the collimator lens...,
Currently it's designed using a coated 40mm diameter achro (39mm actual clear aperture) by 160mm focal length at f4.10. That lens costs $110.00USD.

Does anyone see an issue with swapping that one out with a coated 42mm diameter achro (possibly 41mm actual clear aperture) by 175mm focal length at f4.26, which costs only $7.00USD?

I'm still below the critical f-number of the scope, f4.5, and don't see an issue besides filling the 50mm grating to 94.4% (47.4mm) when the manufacturer states 90% clear aperture (45mm). With the $110 optic I stay less than the 90% but with the cost savings it's worth suggesting it. I don't see an issue, do any of you?

Thanks, Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven

Without knowing the specifications (index of refraction, curvature of the surfaces, thickness of the components) of the lens I can not say anything. Do you have a link to the two lenses? It´s a question of image quality. In my experience cheap lenses are generally not as good as lenses from "expensive" suppliers.

_________________
Daniel P. Sablowski

https://www.kunstmann.de/buch/axel_hack ... 42000/t-2/
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Hi Daniel, thanks.

The more expensive one is from Edmond Optics; http://www.edmundoptics.com/products/di ... c#products, but the other is from Surplus Shed, found during a sort of achro's within a range of diameters and FL's. No other details are known about it....


Just looking for whatever savings can be had....
Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Daniel, I'll get the EO 40mm lens since as I'll only be buying one and I want the best system I can. There are less critical lenses I'll get from Surplus Shed.

I've also purchased the Al plate material today. Time to start attaching the grating holder to the micrometer stage and finding the common denominator for the individual part heights! I have my neon and argon lamps now and reflectors. I'll need to order the SS lenses soon too, and the robotics USB motor driver board....

Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven
I think that´s the best way to go.

_________________
Daniel P. Sablowski

https://www.kunstmann.de/buch/axel_hack ... 42000/t-2/
https://dpsablowski.wordpress.com
https://github.com/DPSablowski
https://www.aip.de/mitglieder/dsablowski/

I know there's been a lull in any advancements of this Custom Spectrograph project but I've been installing the ServoCAT system on the 36" over the last several months, along with Argo Navis. Being a remote installation over Winter on a telescope size rarely encountered means the install is going slow but still going forward....

The pile of parts for Custom Spectrograph project accumulating on the plate pictured earlier with the optical clamps and linear bearings has nearly over-run the edges of that plate. I do have the aluminum plates for the base and walls/covers. I'll probably order the robot motor driver board to better understand the controls of the soon-to-be geared linear bearings that they'll control.

I see on my calendar, showing up next week, that there is a T-15 months notice.... By T-7 I hope to have construction of the spectrograph and lamp calibration units completed, and have 7 months remaining to understand how to functionally use, calibrate, and get First-Data.

Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

At T-13 months I've gotten many of the electronic components to motorize the various parts of the Custom Spectrograph; grating rotation, camera lens focus rotation, linear bearing stage that moves the slit/collimating lens, and, a servo that will flip the calibration light mirror in and out of position.

I'm working on the GUI computer interface in Visual Basic that will enable a mouse click to drive the various motors or turn on lamps, even indicate that the lamps actually turned on using photo-diodes.

I've already created the adhoc wireless network that from a warm-room I can remote desktop control the computer bolted to the telescope that has the GUI loaded.

The tracking on the 36" is still unknown.... The tracking system is completely installed but my new Argo Navis box had a problem and did not see the encoders turning, so without knowing AN can find objects ServoCAT can't operate. Within in a few weeks I'll have a good idea whether or not I need to upgrade the FRP/Teflon materials to Stainless Plate/Roller Bearings. I personally hope the FRP/Teflon works. The servo install has taken 5 months so far.

Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Steven,
Sounds like a major project!
Did you ever fully finalise the optical design?


On 25 April 2012 18:09, Steven Aggas <fg-spek-tech@vdsastro.de (fg-spek-tech@vdsastro.de)> wrote:
--

"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before....
http://tech.groups.yahoo.com/group/astr ... =322612425
"Astronomical Spectroscopy for Amateurs" - Springer

"Grating Spectroscopes - How to use them" - Springer

_________________
" Astronomical Spectroscopy for Amateurs" - Springer

Hi Steven,

do you use an Arduino for controlling the spectrograph? It looks like that.

regards

Juergen

_________________
Gruss Jürgen

Hi Ken, yes, I believe the optical design is done, and parts/prices determined. If there is something you think I missed then please email me, but I think there was agreement from some here that what I had come up with in actual parts would meet the needs as described in the spreadsheet and meet the requirements of The Convento Group and the campaign of WR 134 and WR 135. It is a major project, but it's really fun! I've got all the parts to lay out the calibration lamp box. It'll have both Argon and Neon lamps, controlled by Arduino, using a bifurcated fiberoptic cable that will feed the slit.

Hi Juergen, yes, after much searching I found the Arduino Uno and the Adafruit motor shield. It's capable of driving the needed number of motors and with the available I/O sockets I can activate relays and react to sensor inputs like photoresistors to sense that the right calibration lamp turned on. I'm nearly at an impass with the programming that's needed though (my programming skills are non-existent (I'm much better with mechanical, electronics and optics)), so I'm trying to enlist some help from programming friends, Cloudy Nights, and the Arduino Forum. I could really use some help there....

Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

If there is anyone with programming expertise, here's a picture of the GUI I hope to create, or have created....

Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven,
I have written (and/or copied together ) two little Visual Basic programs to control a spectrograph and a telescope. I use three Arduinios with ADAFruit MotorShields. They drive some steppers and DC Motors. Grating can be turned and collimator can be moved towards the optical axis via steppers. I use the ADAFruit Motorshield library and the Messenger library. Spectrograph and Telecope will/are be controlled by serial commands which are parsed by the Arduinos. All that is far away from being perfect but it starts working step by step.

_________________
Gruss Jürgen

Regarding the topic of guiding on the reflected slit image, with the dark band across the center, what are the software options for guiding on the remnents of the target star that didn't go through the slit? The autoguider camera I'll be using is an Orion Starshooter with its 1280x1024 array, with 5.2um pixels, that would give me a 4.5'x5.6' fov.

Thanks, Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Does anyone have an 1800lpm grating in a size larger than 65mm square, blazed to 500nm?

I could really use a grating that's 75mm or 100mm^2, 500nm and 1800lpm....

Thanks, Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Guys, it's been a while since the last picture update.... Here's the Ar/Ne Calibration Lamp box. On the small board are night-light fixtures on either side of a 5VDC circuit using the LM317T for 1.5 amps to support the relays for the lamps, and, the relays for the geared DC motors that'll drive the stage rotation, slit focusing, camera lens focusing, and, pick-off mirror that'll divert the calibration light into the slit or back out of the way. Not shown is the bifurcated fiber optic cable which will send either lamp's light to the pick-off mirror/slit. There are two light dependant resistors included to provide signal to the computer that one or the other lamp actually lit, as well as light pipe built into the lid so I can actually see a dot of orange or purple on the cover of the box.

The lamp box should be done by this weekend and be computer-controlled by next week using the Firmata software.

I have a 200mmf3 and 300mmf4.5 camera lens I'm deciding between, which, if combined with a >70mm^2, 1800lpm, 500nm grating will give me a system in excess of the Convento Requirements; R~7500+.

_________________
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http://darkskyobserving.com

Here's a picture of the calibration lamp box that looks a little more complete.... Just a few wires left to crimp connectors onto, solder to boards, or plug into the terminal block. Plus, I still have to route the light-pipe fiber optic from the lamps to the lid so I have a visual that they turned on just by looking at the box. The typical audio fiberoptic cable comes with clear cable tip protectors. Those tips will be mounted in the lid and the audio cable will plug into the tips from the inside of the box. The tape on the cover will be removed once those holes are drilled.

The lamp's main fiber optic cable routed to the slit is flex-steel coated. The box has a standard 2.1mmx5.5mm plug for 12vdc on a 5A circuit breaker, and, a 10-pin amphenol cable whose bulkhead socket will be bolted to the spectrograph itself to connect to the Arduino board.

Of course the box looks cooler because it has the caution stickers on it for UV exposure from the Argon lamp, since it has emission lines below 400nm, and, the High Voltage since there's a scavenged inverter board providing 120vac for the lamps with an available external socket with an indicator lamp showing the socket's hot....

_________________
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http://darkskyobserving.com

Success!

The lamp box is finished and is computer controlled! I celebrate the small things sometimes. I do need to find some software that remembers which pins are inputs or outputs once I've configured them but that's another day. For now, I can use the mouse to turn on the neon lamp or the argon and see the inputs go high detecting their light or low when they're off.

Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Well done!
Onwards and Upwards....


On 3 August 2012 01:29, Steven Aggas <fg-spek-tech@vdsastro.de (fg-spek-tech@vdsastro.de)> wrote:
--
"Astronomical Spectroscopy - The Final Frontier" - to boldly go where few amateurs have gone before....
http://tech.groups.yahoo.com/group/astr ... =322612425
"Astronomical Spectroscopy for Amateurs" - Springer
"Grating Spectroscopes - How to use them" - Springer

_________________
" Astronomical Spectroscopy for Amateurs" - Springer

Hi Guys, could anyone detail the standard freeware? I hope the Orion Starshooter with its 1280x1024 array with 5.2um pixels (that would give me a 4.5'x5.6' fov) will work. I'd need a reasonable sized fov to resolve the target star amoungst the rest.... While I'd prefer to use the Orion camera, because it can be the autoguider for photometry and other imaging, what video camera options are there and do they have the fov or bit sensitivity to be useful?

Thanks, Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven,

It all depends how bright the star is and how much halo there is, but you do not necessarily need to guide on the star in the slit.

You can pick any star on the autoguider image.

I do guide with PHD guiding and it works great. I am using a Lodestar guide camera from StarLight xpress

http://www.sxccd.com/

_________________
Grüsse Rainer www.rsfotografia.com

Thanks Rainer, I would have thought field rotation, due to the spectrograph being mounted on an Alt/Az scope, would require slit/star-halo guiding. There won't be a de-rotator in place, and it's not an equatorial mount, so the target star could move in an arc out of the slit entrance, less so with guiding on the remnants of the target star that didn't get through the slit....

Steven

_________________
Apache-Sitgreaves Center for Astrophysics
http://darkskyobserving.com

Hi Steven,

Well yes, I did not realize it is an Alt/Az mount and therefore you are right, you will need to guide on the star in the slit.

PHD is quite forgiving as long as it gets a center of something shiny as long as it is not the Sun.

Sorry

_________________
Grüsse Rainer www.rsfotografia.com

Well an update is long overdue....

With the mechanics of the spectrograph somewhat well understood, one huge hurdle almost brought the project to a halt. The programming code needed to forward or reverse motors, read photoresistors all through Arduino MEGA has been slow, since I can't program....

There are a couple people still working on a program for me that would enable me to, using a remote-desktop network between the computer bolted to the 36" and the one outside the turning radius, control the spectrograph in real time where ever the scope may be pointed.

Several months have been spent on this and it'll take several more to get the code complete, plus more months getting the pieces and parts, plus 8300-based CCD camera. I will probably miss this campaign but when another, in the visual range, occurs I hope to have a system!

_________________
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http://darkskyobserving.com

Hi Steven!

I was sure that you are hardly working on your project. So, I didn't ask again. In fact, I would have been VERY surprised if you could hold our dates knowing the difficulties one can meet. But considering your previous efforts and success I was hoping for that surprise. One never knows. Indeed, it would have been great to have you in the western US on board. We lack some stations there (the only temporal one is DAO on Vancouver Island). But don't worry, we will continue with other projects in the future. So, just proceed with your spectrograph project and jump on other campaigns.

Cheers, Thomas

While the construction of the spectrograph has not progressed, there was one big item needed from the telescope; autoguiding.
The ServoCAT servo motor system was installed, but then, as its deficiencies were found it pretty much meant every single piece of hardware that came in the box had to be rebuilt to make a 1700-pound telescope move well (so the ServoCAT install is coming up on two years now but it has worked for visual purposes). Then, all the gears in the gear box of Alt and Az were put on the drill press and pinned to their shafts when I was finding set screws coming loose (only one per gear is absurd). And, in addition to that, extra brackets were made to eliminate sources of mechanical backlash with using a spool and knurl to move Alt/Az so that the software backlash compensation would only have to take care of the expected gear mesh slop and nothing more. http://darkskyobserving.com/ServoCAT.html . StellarCAT offers a Jr. and Deluxe model. Starting with Deluxe, what I've created is now the Monster model.

As such, I'm happy to say that just two weeks ago, after all was completed and installed I set the speeds of the system software to 7.5-arcseconds per second, and, at 400x in a reticle eyepiece I did not see any noticeable delay when moving the scope or reversing the direction. My estimate is under 2-arcseconds of backlash. The software setting for backlash was set to zero.
Last night I battled the software drivers for Orion's Starshoot Autoguider and it's now working. Next time I go up to the property I'll be seeing for the first time if the autoguider placed in the guidescope, a C8 bolted to the side of the 36", autoguides and I can look into an eyepiece in the 36" and see it stand totally still.
I appear to have nailed the backlash, if the motor/gears system is robust, to enable the the spectrograph project to continue.

Now I will restart the conversation with the software designer that said he'd help with the code to control the spectrograph as I envision it....

_________________
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Hi Steve,

nice to hear from you!

There are always problems which are not planned. This is not limited to amateurs

But you stayed focused and had, apparently, ultimately success. Great!

I wish you the best for completing ServoCAT and installing the spectrograph.

regards,
DS

_________________
Daniel P. Sablowski

https://www.kunstmann.de/buch/axel_hack ... 42000/t-2/
https://dpsablowski.wordpress.com
https://github.com/DPSablowski
https://www.aip.de/mitglieder/dsablowski/

So another update on the project. It's been too long....

I've met an instructor at the local college who, upon hearing about the 36" and the R=7500 spectrograph, asked me to send him the computer GUI details as I envision them to operate the spectrograph using an Arduino Mega board and Arduino/Firmata/Visual Basic. He's thinking there might be a student who finds the project interesting to help me as I'm not a programmer.

As for the 36" telescope it can now do plate-solved slews, ending up perfectly centered on the object, which for the spectrograph requires not so precise centering but certainly is a pleasure to see. The spectrograph autoguider (Orion Starshoot) has a true field of view of 3.8'x4.8' at my focal length when used, so the plate-solved slew should have room for error. The image captured for plate-solving is generated from a Orion Starshoot mounted on a 60mmf5 refractor, optically coincident with the 36".

Also, the entire 1700-pound OTA/rocker box was lifted and stainless plates and roller bearing assemblies installed. Both Az and Alt now ride on bearings to ease the burden on the gear boxes. Wind may be a problem but we'll see.

I have to now set the ServoCAT programmed ratio values for tracking and hope to see usable, smooth tracking.

_________________
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http://darkskyobserving.com