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Thalestris24

The Lowspec spectrometer

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21 hours ago, Thalestris24 said:

Hi Jim

I've currently fitted a 121mm fl, 26mm dia doublet from surplus shed for the collimator and a 100mm fl, 31mm dia doublet for the camera lens (think it must have come from my 2" ep but not sure... Still not put the Ovio slit in - will aim to do that tomorrow :) I don't think I'll worry about IR passing through for now. If there seems to be a problem I have some blackboard black spray paint - might be worth trying, though I don't have any infra red data on it. Oh, I never got my slit holder locking ring to screw in but I can push/click it in, so think that will do :). Did you get the 600 lpm grating? You have to be careful with Thorlabs ordering - first time round I inadvertently ordered an IR version - tut! But they kindly sent me a replacement visible light one together with another box of lab snacks!

No rush - we can take our time. The stars will still be there :)

Louise

Thanks Louise.  My doublets from Surplus shed weren't cemented together - two separate lenses. I'm assuming I just place them together and maybe tape the rims together. Or have I got that completely wrong - I wouldn't be surprised :)  I went for the 1800 lines per mm grating, maybe without any great thought actually as to how to match that to the cameras I have.  I was keen on the idea of seeing if I can make use of the device in the classroom as well - we cover spectra and emission lines in the syllabus generally using 1800 transmission gratings and I've always wanted to show them via a camera set up. Off to Paris tomorrow on a school trip so progress with be put on hold until "le weekend" - assuming we get back what with the strikes :(  Good progress Louise I think you are right about the emergence of a spectra in you last post. I'm really impressed by this, it's a nice fun project with really good application as shows the potential of the 3d printers well. 

Jim 

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Jim,

The separate lenses of the doublets..... you'll need to space them. Three small strips of sellotape equally spaced around the circumference would work.

The SimSpec spreadsheet with give you a good approximation of wavelength coverage with your camera, as well as the resolution.

 

 

SimSpec V4.3_Paul3D.xls

Edited by Merlin66
wrong spreadsheet

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2 minutes ago, saac said:

Thanks Louise.  My doublets from Surplus shed weren't cemented together - two separate lenses. I'm assuming I just place them together and maybe tape the rims together. Or have I got that completely wrong - I wouldn't be surprised :)  I went for the 1800 lines per mm grating, maybe without any great thought actually as to how to match that to the cameras I have.  I was keen on the idea of seeing if I can make use of the device in the classroom as well - we cover spectra and emission lines in the syllabus generally using 1800 transmission gratings and I've always wanted to show them via a camera set up. Off to Paris tomorrow on a school trip so progress with be put on hold until "le weekend" - assuming we get back what with the strikes :(  Good progress Louise I think you are right about the emergence of a spectra in you last post. I'm really impressed by this, it's a nice fun project with really good application as shows the potential of the 3d printers well. 

Jim 

Enjoy your trip! I thought 1800 lines/mm might be a bit ambitious so settled on the 600 line one. Can always upgrade... I should be able to cover the visible spectrum with the Atik but will have to see how it all works in practice. Of course, I need to fit the proper grating. I'm using the streetlights (about 100m distance) because they are bright and don't move! I think it will be quite hard to locate a particular star on the slit. I'm using a 500mm mirror lens at the moment rather than a longer focus length scope.  It makes the whole setup quite compact. It wasn't my original intention but I had a moment and it seemed a good idea. The achromatic doublets should be cemented together. Not sure how you ended up with separate lenses - were they wrapped separately? Are you sure you ordered coated doublets? I would check their focal lengths.

Louise

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Louise,

Seriously, get the testing completed on the bench with a fluoro lamp before worrying about star testing.

Much easier, repeatable and satisfying.

 

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5 minutes ago, Merlin66 said:

Louise,

Seriously, get the testing completed on the bench with a fluoro lamp before worrying about star testing.

Much easier, repeatable and satisfying.

 

I'm not star testing really. I don't have a bench... The streetlights don't move and I have the setup temporarily mounted on a Star Adventurer dovetail :) I can always change things to run without a lens. It probably would be easier if I had a table lamp and if I had a cfl bulb. Maybe I could get a table lamp in Tesco. I have a halogen lamp that I maybe could use. Anyway,  I'm not in any hurry - will just see how it goes.

Cheers

Louise

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Have been fiddling around today... But here's an image I got from my bright room light via a mirror (no lens). It's a halogen bulb so continuous spectrum and a wide beam from the mirror. I set the slit to 50um. I still haven't put the proper grating in - will definitely try and do that tomorrow :) I don't understand why I have two 'stripes'. I'm not certain whether the camera is in focus (one of the things I've been fiddling about with today). The image looks a bit blurry but can make out some features 😉 It's reduced to 40pc of it's actual size. Anybody know if this is approaching what I'd expect to see?

 

HalogenRoomLight_50um_bin1_00003_40pc.thumb.jpg.ec93402f6a84a0e6e19a30e0481a5d8f.jpg

Oh, not sure about how well it's collimated either. One step at a time!

Thanks

Louise

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Louise,

I think the top section is probably a reflection from something...wait until you use the proper grating.

Ideally, the spectral image should be centred across the camera chip, looks close. Improve the focus and you should get close to a recognisable spectrum with a fluoro lamp.

 

 

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7 minutes ago, Merlin66 said:

Louise,

I think the top section is probably a reflection from something...wait until you use the proper grating.

Ideally, the spectral image should be centred across the camera chip, looks close. Improve the focus and you should get close to a recognisable spectrum with a fluoro lamp.

 

 

Oh ok. If the rain stops for long enough tomorrow I'll see if anyone nearby has a cfl in stock. Focus is proving difficult - I couldn't discern any difference between one end of the range and the other. I hope I'm right in assuming you measure the focal length from the mid-point of the doublet?

Thanks

Louise

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Louise,

A halogen lamp doesn't show any spectral detail - that's why they are commonly used to prepare imaging flats.

The back focus of the lens would be measured from rear surface of the lens (not 100% correct, but near enough)

Ken

 

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1 minute ago, Merlin66 said:

Louise,

A halogen lamp doesn't show any spectral detail - that's why they are commonly used to prepare imaging flats.

The back focus of the lens would be measured from rear surface of the lens (not 100% correct, but near enough)

Ken

 

Yeah, thought halogen wouldn't be very useful but it's all I have apart from a LED bulb. I have some neon bulbs though obviously they are just in the red end. If back focus of a doublet is measured from the rear then I might need a 5mm spacer....

Thanks

Louise

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