Spectroscope built by my niece

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Montana
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Spectroscope built by my niece

Post by Montana »

My niece and nephew came round for tea last night and my niece brought round her spectroscope she has built to show me. She wanted me to share it with you all so I took some photographs for you to see. She was given a grating by a chap at the local astro society so she designed how she wanted to fix it to her telescope




Then she built it out of bits of wood




and managed to take a spectrum of some reflected sunlight from the moon with her DSLR







I am very proud of her achievement.
The only problem she was saying was that the lines are not very focused and I said her slit was too wide. The problem is that she said if the slit was narrower then the amount of light coming through is too dim to take a photograph. Any suggestions to get over this would be welcome?

Kind regards
Alexandra and Emily


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Re: Spectroscope built by my niece

Post by marktownley »

Woohoo! That's great stuff Alexandra and Emily. I'm not sure what to suggest to answer your question, but i'm sure there are people here who do know and will be able to help.

Mark


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Re: Spectroscope built by my niece

Post by highfnum »

do I see absorption lines in there?
cool


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Re: Spectroscope built by my niece

Post by swisswalter »

Hi Emily


congratulations. What a mod. Me too I can see absorption lines.


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Re: Spectroscope built by my niece

Post by robert »

do I see absorption lines in there?
cool

:thumbsup:
Robert


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Re: Spectroscope built by my niece

Post by Carbon60 »

Nice work, Emily.

I'm sure someone from this forum will be able to advise.

Looking good though.

Stu.


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Re: Spectroscope built by my niece

Post by p_zetner »

Hi Alexandra and Emily.

Nice job!

I do have a couple of suggestions, though. It looks to me like the eyepiece is backwards. The goal is to put the slit at the eyepiece focus (not the observing end).

Also, you don't have a collimating lens in this arrangement (between slit and grating) so, a longer focal length eyepiece would give a better approximation to the required parallel beam at the grating. At the moment, because of the short eyepiece focal length, you're probably throwing much of the incident light around the grating (severe vignetting). Also, as an added benefit, a longer focal length eyepiece would have larger aperture lenses and collect more intensity.

If you wanted to do a bit of a re-design, a collimating lens would probably improve your results significantly.

Cheers.
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Re: Spectroscope built by my niece

Post by Merlin66 »

Well done to your niece for attempting this project!!
As Peter says, the slit (there seems to be a series of holes??- maybe just the image?)should be as narrow as possible and positioned at the focus of a very low powered eyepiece - an achromat (surplus shed?) would be better.
Then the parallel, collimated beam is directed to the grating and the diffracted spectrum to the camera lens.
The grating (if blazed, for maximum efficiency)will be seen to produce a series of spectra on both sides of the "normal" axis - look for the brightest (1st Order) and direct this to the camera.
Onwards and upwards.


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Re: Spectroscope built by my niece

Post by Montana »

Thanks guys :thanx:

In lay mans speak do you mean that the slit needs to be before the eyepiece? if that is the case does that mean you have to try and make a round one and slot it in the hole before the eyepiece goes into the telescope?

Also, what do you use for a collimating lens? and where does that go?

Many thanks
Alexandra


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Re: Spectroscope built by my niece

Post by Derek Klepp »

This is really great stuff Alexandra and I would think one of the reasons Stephen created this forum, to get younger people involved in science.And at the same time have the benefits of those such as Ken and Peter to help out.


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Re: Spectroscope built by my niece

Post by Merlin66 »

Alexandra,
The slit should be positioned at the focus of the telescope. A lens (the collimator)or very low power eyepiece is then focused on this slit.
If you use a collimating lens, this can be a simple x0.5 eyepiece reducer (like they use for imaging a webcam) These small (28mm diameter) lenses are usually about 80mm focal length.
The emerging beam from this lens is parallel and should be directed at the grating. The spectrum formed by reflection from the grating is then imaged with a camera lens.
That's the basics.
The attached sketch should help. I obviously could go into much more detail. let me know if I can assist further.



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Re: Spectroscope built by my niece

Post by Montana »

Thanks Ken :)

I'll chat to her on Christmas day and show her all the info :thanx:

Alexandra


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