The Lowspec spectrometer

[Thalestris24]

Happy New Year, Ken! @Merlin66

Louise

ps I expect you've gone to bed by now! 

[Merlin66]

Louise,

Thanks for that!

I hope you had a good Hogmanay.

Wishing you a safe and happy New Year.

 

 

[Thalestris24]

14 minutes ago, Merlin66 said:

Louise,

Thanks for that!

I hope you had a good Hogmanay.

Wishing you a safe and happy New Year.

 

 

I'm always home alone so these things pass me by!

All the best

Louise

[Thalestris24]

Happy New Decade Everyone!!!

Edited January 1, 2020 by Thalestris24

[Thalestris24]

Finished off the starter bulb holder today. It's just a push fid into a hole in the lid which now also has a matching hole cap

You can't see it here but there is some aluminium foil wrapped around to make a reflector. I got an ok exposure with 30s compared to 2mins before:

Not sure why it appears a bit blurry at the flipped bottom. I'll have to check the slit holder assembly is seated ok. Probably still needs longer for the blue end (my Atik 383l+ isn't the fastest of cameras...). I'm going to investigate different bulbs - I've seen a 'Sylvania' brand 70W bulb on YouTube which appears to glow blue-violet so might be worth a try. My local Screwfix sells them so might pop up there soon, now that the shops are open again up here from tomorrow (still a bank holiday today!). Also, when I get the cheap, Chinese inverter, if it works and I can locate a 110V AC tapping I should be able to run from that, and also without a resistor.

Louise

 

[Paul Gerlach]

Louise,

I think the light source should be straight above the slit and aligned in the direction of the slit. Most commercial spectrometers use a reflective surface that is placed above the slit which reflects the light in a diffuse manner.

Paul

[Thalestris24]

2 minutes ago, Paul Gerlach said:

Louise,

I think the light source should be straight above the slit and aligned in the direction of the slit. Most commercial spectrometers use a reflective surface that is placed above the slit which reflects the light in a diffuse manner.

Paul

The lit part is just opposite the slit - if that's what you mean?

Louise

[Paul Gerlach]

Okay, quick drawing then...

 

[Thalestris24]

3 minutes ago, Paul Gerlach said:

Okay, quick drawing then...

 

Ok - that's what I have, and with a foil reflector. I thought I'd explained what I'd done clearly before...

Louise

[Paul Gerlach]

Ah, sorry for the misunderstanding then.
I remember that the version of your LOWSPEC has an slit holder with round holes underneath the OVIO slits. This masks on end of the slit. This design error was pointed out to me by someone and is corrected in the newest version of the LOWSPEC which I'm about to upload to Thingiverse. That new slit holder will allow you to use the full length of the slit.

Paul

[Thalestris24]

4 minutes ago, Paul Gerlach said:

Ah, sorry for the misunderstanding then.
I remember that the version of your LOWSPEC has an slit holder with round holes underneath the OVIO slits. This masks on end of the slit. This design error was pointed out to me by someone and is corrected in the newest version of the LOWSPEC which I'm about to upload to Thingiverse. That new slit holder will allow you to use the full length of the slit.

Paul

Yes, it does. Hope I can upgrade to the new version, then! By the way, there has been some discussion about which way round the Ovio slit should be. I did have it as shown in your assembly guide but was then advised to change it to have the 'right way round' numerals facing the telescope. Maybe you could clarify?

Thanks

[ejp1684]

On 01/01/2020 at 00:37, Thalestris24 said:

Happy New Decade Everyone!!!

And to you, Louise!

4 hours ago, Thalestris24 said:

Not sure why it appears a bit blurry at the flipped bottom. I'll have to check the slit holder assembly is seated ok.

I had this but not quite as emphasised as your example. I did wonder if my grating wasn't exactly vertical in its holder, and it did look as though it was pointing down slightly, so I packed it out at the top with a couple of slivers of paper and it seems better. Probably doesn't matter too much, as only a very small section will be used for calibration.

Eric.

[Thalestris24]

1 minute ago, ejp1684 said:

And to you, Louise!

I had this but not quite as emphasised as your example. I did wonder if my grating wasn't exactly vertical in its holder, and it did look as though it was pointing down slightly, so I packed it out at the top with a couple of slivers of paper and it seems better. Probably doesn't matter too much, as only a very small section will be used for calibration.

Eric.

Hiya - it was just that I'd had the assembly out to help mark where to drill a hole for the bulb holder. I'll have a fiddle with it tomorrow.

Louise

[Merlin66]

Louise,

A wrap of translucent paper around the bulb then the partial aluminium foil reflector would help.

Bulbs generally need a diffuser to suppress the actual bright filaments.

 

Edited January 3, 2020 by Merlin66

[Thalestris24]

11 hours ago, Merlin66 said:

Louise,

A wrap of translucent paper around the bulb then the partial aluminium foil reflector would help.

Bulbs generally need a diffuser to suppress the actual bright filaments.

 

Oh ok - I might try that then - I suppose some tracing-type paper is the nearest thing I (may) have. However, the starters aren't that bright to start off with so minimum of 30 sec exposure needed without diffusing. 45sec better, I expect. I'll have a fiddle in the morning . I think the shiny side of the foil helps reflect quite a bit of light back towards the slit.

I'm intrigued by Paul's upgraded slit holder design he mentioned above. Having more of the slit available would be good. I did wonder why he only had relatively small round holes over the slits. An oblong hole would likely be better. If I'd had the original design file for the holder I might have had a go at changing it myself but it's properly Paul's design, of course!

Cheers

Louise

 

Edited January 3, 2020 by Thalestris24

[Merlin66]

Louise,

On my Custom OVIO slitplate I had 6mm holes behind the slits (6mm long) to prevent any unwanted light getting through.

[Thalestris24]

3 minutes ago, Merlin66 said:

Louise,

On my Custom OVIO slitplate I had 6mm holes behind the slits (6mm long) to prevent any unwanted light getting through.

On the current Lowspec, as I'm using, the holes are only about 4mm dia...

[Paul Gerlach]

Louise,

Download the new Slit holder disk from Thingiverse (16_ovio_holder_slit_disc.stl) and use that. It has larger openings.

[Thalestris24]

55 minutes ago, Paul Gerlach said:

Louise,

Download the new Slit holder disk from Thingiverse (16_ovio_holder_slit_disc.stl) and use that. It has larger openings.

Thanks - I just notice you posted the Lowspec 3.0. I'll have a look? Also should I have the Ovio radial slit the way you've shown it in the 2.0 assembly guide?

Thanks!

Louise

[Paul Gerlach]

Well, the reflective surface should face inwards. To the optics of the spectrometer. That will give you a ghost image of  the star on you guide camera due to the thickness of the glass plate, but will avoid strange reflections and refractions in the spectrum.
In the versions I bought that means that if you look onto the slit holder assembly (where the light of the telescope falls onto the slit plate) the numbers should be mirrored.

[Thalestris24]

43 minutes ago, Paul Gerlach said:

Well, the reflective surface should face inwards. To the optics of the spectrometer. That will give you a ghost image of  the star on you guide camera due to the thickness of the glass plate, but will avoid strange reflections and refractions in the spectrum.
In the versions I bought that means that if you look onto the slit holder assembly (where the light of the telescope falls onto the slit plate) the numbers should be mirrored.

Yeah, that's how I had it originally. TBH I couldn't really tell the difference between the two sides. Never mind, I'll try printing out the new holder and swap it round again when I exchange the original one. I take it it's otherwise exactly the same size. Is the white slit illuminator part still the same?

Oh, I had loads of trouble getting the lock ring to engage the thread on the holder (printed in PLA). In the end I printed it a little small so that it more or less snapped in instead!

Thanks

Louise

[Paul Gerlach]

Well, stand by a window and look at the surface of the slit plate at an angle. If you look closely at the reflection at the edge, you will probably be able to tell which side is which.

 

[Thalestris24]

1 minute ago, Paul Gerlach said:

Well, stand by a window and look at the surface of the slit plate at an angle. If you look closely at the reflection at the edge, you will probably be able to tell which side is which.

 

Both sides look the same to me! But I have poor eyesight (cataracts). As I say, I'll put it back the 'right' way when I change the holder. The new version is printing now

Louise

[Paul Gerlach]

About that printing. More specific printing threads. Is the extruder of your printer calibrated? Meaning that if you meant to print 10 mm of filament than it will actually print that amount. Printing items with small tolerances like threads is challenging and you do not want to print to much plastic (over extrusion) or to little (under extrusion).
There are some good instructions on the internet how to do that. Like this one.

Paul

[Thalestris24]

12 minutes ago, Paul Gerlach said:

About that printing. More specific printing threads. Is the extruder of your printer calibrated? Meaning that if you meant to print 10 mm of filament than it will actually print that amount. Printing items with small tolerances like threads is challenging and you do not want to print to much plastic (over extrusion) or to little (under extrusion).
There are some good instructions on the internet how to do that. Like this one.

Paul

Hi

I didn't know there was such a thing as calibrating the extruder! I'm a 3d printing noob - the lowspec has been my first go at printing anything. I had a look at your link but didn't really understand it... I have an Ender 3 Pro and use Cura to do the slicing. Mostly I've been printing parts in 'super quality' i.e.  0.12mm. I'd noticed that some circular parts had a diameter of about 4% different from expected. I'd assumed that was just due to shrinkage. But perhaps it's a 'calibration issue' then. I'll look deeper into it should I do any more printing!

Thanks

Louise