Wow! L200!

sheeny (Al) · #1 25-09-2010, 11:31 AM

I just ran the laser collimator through my new L200 spectrograph, and then managed to set up a crude EP mount. I had a play with the spectrum of my fuoro desk lamp first and then took it outside and pointed it at the sun though clouds and all.

Wow! So many lines! I think seeing you first real time solar spectrum in such detail is right up there with your first view of Saturn!

I can't wait to get the fittings so I can set it up on the scope and camera.

Al.

DavidU (Dave) · #2 25-09-2010, 12:01 PM

Awesome news.

Terry B · #3 25-09-2010, 05:03 PM

Brilliant. Frustratingly I have too much cloud to do anything with mine.

sheeny (Al) · #4 28-09-2010, 06:55 PM

Attached are a couple of photos of my Spectra L200.

The first shows the initial attempt to fit it to the scope with the Vixen flip mirror. I need to do some thinking about this as its very tight for the ST8 this way (I have to turn the spectroscope a bit to keep the camera square to the spectrum and clear the mount!). Mounting it straight through puts the camera way out the back in space... just after an initial play, I think I'll have to look around for a 2" visual back with double screws at least. I don't like hanging it all of a single locking screw.

Still waiting on my Baader parts to mount the camera...

I should've taken some photos while I was building it

.

Al.

Merlin66 (Ken) · #5 28-09-2010, 07:26 PM

Al,
You can use the small O rings in the kit to give some additional "rotation" of the T thread adaptors/ spacers.
I use a similiar set up on the C9.25/ 12" Lx but the Vixen at 90 degrees to the Spectra-L200; this allows the guide camera to be positioned inline with the focuser, the imaging camera at the side and the micrometer at the other....
(I also fit a safety strap to make sure if ANYTHING comes loose, then the unit can't fall!!)
The attached illustration didn't make it to final copy but does show the set-up well!

sheeny (Al) · #6 28-09-2010, 07:56 PM

Thanks Ken. I'll have to experiment with that, but it might give me the clearance I need. If I can I'd like to keep the ST8 low and reasonably close to the RA axis as I think I'm probably pushing the EQ6 anyway with the ED80 and C11 side by side on it.

Al.

sheeny (Al) · #7 02-10-2010, 10:56 AM

I've done a bit more tinkering, and I think this will be the initial arrangement when I finally get my Baader fittings to connect and focus the camera. Its not a very good photo, I know... I overestimated the depth of field I could achieve at such close range

. I've just used the 1.25" adapter from the Vixen flip mirror to mock this up for the time being.

I know... the controls are facing the scope, but its a compromise

. The scope is going to be pointing up, so the controls will be pointing up too. It saves me from having to get down on the floor to read slit and micrometer scales as long as I'm prepared to move around the scope a bit to see them. At least that's the theory

.

This arrangement keeps the micrometer close under my ED80, and also keeps my ST8 low and close, making balancing easier, without being too likely to crash near zenith.

The proof will be in the pudding, of course

.

I have a velcro safety strap for the L200, but I need to make one for the ST8 itself as it may spent a reasonable amount of time upside down or close to it. I'll make a tab to fit the 1/4"-20 tripod mount with a thumb screw

.

I have also ordered a beam splitter plate to do Ken's mod on the Vixen flip mirror to turn it into a 70/30 beam splitter

.

I can't wait! ...but I have to!!!

Al.

sheeny (Al) · #8 04-10-2010, 03:47 PM

Since I sprained my knee on Saturday, I've had to take it easy to try to get it as good as I can before going to IISAC

, so I've had a bit of time on my hands...

Today, I bodgeyed up a camera in the Spectra L200!

Because all I have to attach the camera with is the EP holder off the Vixen flip mirror, and it won't let the camera reach focus, I resorted to putting a 2x barlow lens (only) on the camera nose piece to get it to focus.

These spectra are all of the four bright fluoro lines, but the yellow doublet allowed me to determine the dispersion

, and so calibrate the others. The main purpose of the exercise was to calibrate the micrometer for the fluoro lines, but hey... why not play?

Each of the lines are not flux calibrated to each other, and each spectrum was normalised. Slit was set to 20 microns.

The dispersion on the DMK is pretty impressive! The resolution though is still pretty rough (commensurate with the focussing method

). I'm not sure what's happening with the apparent absorption in the centre of the yellow doublet lines

- probably a stacking error as I don't remember seeing that in any frame up until I binned it in VSpec. I don't imagine the fluoro lamp is big enough for self absorption to be evident.

Al.

Merlin66 (Ken) · #9 04-10-2010, 06:31 PM

It's terrible what we get up to when it's cloudy!!
I've used reducers on the imaging side (to get smaller brighter images) but not a Barlow (yet).
The yellow doublet is at 5769.6/5789.66 (20A separation)
The dark core in the lines I assume is due to saturation inversion. What was the max ADU? The DMK is only 8bit....and conversion to a fits/pic file could be the issue.
A shorter exposure may be the answer.
All in all it looks like your off to a good start....

sheeny (Al) · #10 04-10-2010, 07:35 PM

Desperate times call for desperate measures, Ken

. It shouldn't be saturation inversion... I was careful to keep the histogram to about 225 or so.

I've had another play... when I reprocessed the yellow doublet, I found the image and spectrum was OK up until I normalised it in VSpec

... then the "absorption" artifact appeared.

Then I remembered that I wasn't converting from 2D to 1D in IRIS, so gave that a whirl and everything seems much better behaved. I'm still a bit suss about the red line though. As it was captured it appears very broad (broader than the others) and smooth like the original version and I'm not sure if I've created artifacts in the reprocess (or why I would have - I went through every frame manually to check the alignment

), but the other lines are better

.

Al.

Terry B · #11 05-10-2010, 04:26 PM

I have made a couple of spectra using the new L200
Atria and Achenar.
The Atria spectrum is 2 field combined from UV to about mid red. The Achenar spectrum is a single field from the UV to blue. The lines in the Achenar spectrum are H lines - gamma, delta, epsilon plus some He lines.
The Atria spectrum is full of lines but I'm not sure what is what. The calibration may be a bit out with the Atria spectrum but the Achenar one is pretty close.

sheeny (Al) · #12 05-10-2010, 05:41 PM

Looks really good Terry!

Lines everywhere!

Al.

Merlin66 (Ken) · #13 05-10-2010, 05:56 PM

Terry,
Well done! I'm impressed to see the results so far down in the UV.
The forest of lines in the K star will be a challenge...according to Kaler, the CaII and FeI should dominate
If you post the fits files on the Y! group we can assist with the line identification (I hope!)
Are you taking darks/ flats to match the images? What about a camera/ instrument response curve correction?
Onwards and upwards!
ken

sheeny (Al) · #14 05-10-2010, 07:14 PM

This may be a silly question Ken... but... how do take a flat through a spectroscope? I have seen mention of flats before and wondered how to go about it. Won't the flat just be a spectrum of the light source?

Al.

Merlin66 (Ken) · #15 05-10-2010, 07:35 PM

There's acouple of ways of doing it...
The important points are:
-Take the flat at the same grating setting as the target spectrum
-Don't change the optical train (ie slit, telescope focus, camera focus and position etc) between the target spectrum and the flat.
- Each position of the grating requires a new flat.

Yes you're right about the spectrum and lines....
The way around it is to use a diffuser and a Quartz Halogen lamp in front of the telescope objective - like a conventional flat screen. The Halogen lamp gives a pretty uniform flat spectrum with no lines, so can be used to give a good flat.
An alternative method is to make up a "tube" with a diffuser at the end and place it over the entrance slit. The diffuser should be sized and positioned to replicate the f ratio of the scope being used ie a 20mm aperture at 200mm distance will be seen as a f10 beam on the slit.
Hope that helps (It's all covered in the Book - p82-83 -If Springer ever get their act together!!)
Ken

sheeny (Al) · #16 05-10-2010, 09:15 PM

Thanks Ken.

Al.

Terry B · #17 07-10-2010, 10:12 PM

I had a rare clear night last night and was able to take a few spectra.
I have created a labelled spectra of Alp Pav. This one is cleaner than my last one as I am getting a bit better at processing them. It is a stack of 5 x 60 sec exposures at the blue end of the spectrum into the near UV.

Merlin66 (Ken) · #18 08-10-2010, 10:36 AM

Terry,
Notwithstanding the concerns re focusing; you're achieving some very good results...There are 10 Spectra-L200 Kits being assembled at the moment (with another 15 to ship soon) - I'm sure your images will encourage the others. As you know it's a steep learning curve with slit spectroscopy but certainly success is achievable.
Well done!