Back to It

[theodog]

Hi All,
Re-motivated throughout last month.
Worked on attaching the spectroscope to a 10" f4.5 permanently.
The 'scope is an old DS10 reincarnate several times, now two high school science stools welded.
Progress so far.
:)

Does this go here or another forum now:shrug:

[Heian]

Jeff,
that looks like it will end up a sweet system. Are you using a pair of 135mm lenses for the collimator and focus?
What type of mount are you looking at for the scope? Based on what I can see in the images it will need to be as solidly built as the scope!
:)


cheers
Mark

[theodog]

Close, I have a 300mm collimating and a 135mm focus lens. One camera will be the guide camera, the other imaging spectra.



It should be held by the G11, it has been used to image with a 12".

Tonight I set up to do some bench tests using a ES globe back at the house. I found that the guide camera will need a lot more relief to be parfocal with the spec image and a lot more alignment needed. No images, I just used white card.
:D

[theodog]

From tonight.
B&W is through the spec attached to the 10". Not yet focused and the slit fairly wide open. Imaged by a ST2000xm.
It seems to match fairly closely to an earlier spec taken of a similar light.
I'm not sure of the black lines but I think they have to do with over-exposure.
:D

[Merlin66]

Jeff,
Glad to see it coming together!
A permanently mounted spectroscope...now that's dedication;)
I've got no idea what's happening in the top B&W image...
Assuming a wide slit it appears like a series of - something???
Is the camera aligned to the optical axis? Should the spectra be centred rather than from the edge (or has this been cropped?)
A series of shorter exposures and a gradually narrower slit might make things clearer..
(The bottom coloured spectrum shows the "ripple" in the absorption lines usually associated with the slit being misaligned to the grating)
Now the book is finished I hope to get back to observing myself ( if the clouds over here ever go away!!)

Ken

[theodog]

Thanks Ken.
It has only just been thrown together. I'm slowly working through each of the variables and improving them.
The large black lines do seem to be from overexposure on the chip.
Collimation is sort of close, if you know what I mean, and needs more work.
The colour image is an oldie with the BAA in its early days, just used to see if I could find some lines for callibration of the optical train.

Now the long, slow, serious allignment and focus begins.
:D

[theodog]

Slow progress.
This is where I got to tonight.
Each image is the sum of 30x0.11sec exp. ES light globe at ~30m.
The image plane does not seem to be flat, ie, different focus across the spectrum.
Any answers?
:)

[Merlin66]

Looks like you're getting there!
The focus problem I think will be the chromatic aberration in the imaging lens; I have to re-focus between blue/ green and red...
Unless we use mirrors in the design this is what happens....
Run the spectra through Vspec and see what the differences in resolution (FWHM) are between the images; do a second set with a re-focus and compare....

Ken

[theodog]

Thanks Ken
I had to download the 07' version of Vspec -works well. I have to learn it again, its been so long.
I have loaded an image of a composite from Vspec and the .dat file.
:)

[Merlin66]

The profile clearly shows the Hg lines at:
4358.33, 5460.74, 5769.6, 5789.66 and the usual collection of Fluoro bumps...
Haven't check the FWHM yet, but the spectrum looks very good!
Well done.

Ken

[theodog]

I've hit the first major hurdle.
The image of the guide camera lines up on the slit:D, but.....
The guide camera doesn't have enough in-travel to come to parfocus with the slit.:sadeyes:
I will have to move the slit (and collimating lens) towards the primary by ~1/2". I have the room to do this but its a complete stripdown of the spectroscope. Bugger:mad2:.

[renormalised]

A "MOAS" (Mother Of All Spectroscopes) !!! :)

Great bit of gear!!!. Hope you can iron out the bugs and get it running sweetly. That will be a great addition to your equipment list :)

[theodog]

Thanks Carl,
Have solved the parfocal problem and narrowed the alignment of the guide camera and slit. Still prob's with the ST2000 overexposing the spec image, so plenty of trials ahead for correct exposure times.

:)