Fraunhofer Lines and the L200

sheeny (Al) · #1 18-03-2011, 06:59 PM

Here we go!

I got the opportunity to get back to sorting the L200 and ST8 today. Here's the first spectrum off the rank - Fraunhofer F. I've got C, D, E and G to process yet.

These were first light after focussing the ST8 on the slit. It was a cloudy day so the L200 was just pointing through the window - no scope. 3 x 30s images were stacked after dark subtraction only, preprocessed in IRIS (another learning curve

). Slit was roughly 20 um (I need to check it after having the pull the L200 apart to refit the shutter after I broke it fitting the neon reference lamp

). Dispersion is about 0.92A/pixel. No flats or bias, no instrument response correction.

Al.

Merlin66 (Ken) · #2 18-03-2011, 09:21 PM

Well done!
Good dispersion, good focus, good result

The BASS reference solar spectrum will help you identify the numerous lines.
The practise with IRIS and Vspec will help as you move up the learning curve...a bit steeper than with the Star Analyser!
Onwards and Upwards.
(BTW the latest neon blocks have a 3mm chamfer at the back edge to give better clearance on the shaft....superglue works

)

sheeny (Al) · #3 18-03-2011, 09:43 PM

Thanks Ken.

I'll check out the BASS spectrum.

Superglue is great stuff isn't it?

Al.

robz (Robert) · #4 19-03-2011, 11:08 AM

Hi Al, any chance of seeing some of the red end of the spectrum?

Looks fantastic so far.............congrats!

Rob.

[1ponders] (Paul) · #5 19-03-2011, 11:48 AM

Way to go Al. I'll echo Ken, onwards and upwards.

sheeny (Al) · #6 19-03-2011, 12:15 PM

Thanks Rob and Paul.

Here's the spectra around Fraunhofer C (Ha) and E as they are at present. I'm not so confident of the dispersion ATM. If its right the sodium doublet should be visible in the RHS of the Fraunhofer E spectrum

and while I was working on the Fraunhofer D spectrum last night 0.9214 A/pixel wasn't making much sense, so I tried calibrating off the two sodium lines... and that suggests a dispersion of about 0.5 A.pixel!

hmm... more work to do

.

Al.

[1ponders] (Paul) · #7 19-03-2011, 12:22 PM

Pretty piccies Al.

All the rest......

sheeny (Al) · #8 19-03-2011, 05:10 PM

Here's another one Paul.

Well, to resolve my dispersion confusion I made a mosaic of the Fraunhofer C, D, E and G captures (F wasn't needed - it was all overlap) in IRIS, and then processed the lot together in VSpec.

Turns out the dispersion is 0.72 A/pixel, and at the same time I made a response curve for the ST8I and corrected the whole thing.

Its a pity VSpec won't let me stretch the spectrum wider, but I can always produce larger scale spectra if required.

Al.

sheeny (Al) · #9 19-03-2011, 10:03 PM

Yeah, well its cloudy isn't it?

Al.

Merlin66 (Ken) · #10 20-03-2011, 01:42 AM

Lookin' good!
I think the focus is tighter in the red...you may have to tweek the focus for the green (outwards) and in the UV (Inwards) about 0.2mm each way.....
Just wait till we crack the non-rotating focuser for the Spectra-L200 you're going to love it.
Well done - you should re-post them on the group as encouragement to others!

sheeny (Al) · #11 20-03-2011, 09:18 AM

Thanks Ken.

I've already posted them in "Al's Album" but I notice that reduces the size of them making them hard to read. Maybe I should put them in the files section?

Well, if I'm gonna have to adjust focus by 0.2mm on a regular basis the helical focusser will be a must! It's all guess work with the Baader telescopic focusser

. It'd be OK if I could set and forget...

Al.

Quote:

Originally Posted by Merlin66

Lookin' good!
I think the focus is tighter in the red...you may have to tweek the focus for the green (outwards) and in the UV (Inwards) about 0.2mm each way.....
Just wait till we crack the non-rotating focuser for the Spectra-L200 you're going to love it.
Well done - you should re-post them on the group as encouragement to others!

robz (Robert) · #12 21-03-2011, 03:06 PM

Nice stuff Al!!!!!!!...............I'd be very happy with those results!

sheeny (Al) · #13 21-03-2011, 04:54 PM

Thanks Rob.

Al.

Merlin66 (Ken) · #14 21-03-2011, 05:29 PM

Al,
if space allows that TSTRVv and the narrow Baader 360 degree rotator appear to give a more robust and controllable focus. 0.2mm would represent about a 1/3 of a turn....
I seem to be able to use it on everything other than DSLR...

sheeny (Al) · #15 21-03-2011, 06:54 PM

How long is it, Ken? I think the CCD is something like about 23mm inside the ST8 so I've got about 38mm to play with.

Al.

Merlin66 (Ken) · #16 21-03-2011, 07:10 PM

The TSTRVvar is 20.75 to 31.75 adjustable.
That's the distance from the front edge to the T thread shoulder.
If used with a male/male on the Spectra-L200 that would add about 2.5mm, then the 360 rotator is 5.5mm wide.
So when stacked: m/m>TSTR>360rot ; min: 28.75 and Max 39.75mm
HTH