The Lowspec spectrometer

[saac]

My new lens has arrived together with some more Thor Lab snacks   Hopefully I will find some time today to get it installed and try it out.   

Jim 

[saac]

New lens now fitted and after a very quick play against a bright sky I managed to refine the focus. Still not perfect and not focused over the entire field but I feel I'm getting there. I'll hopefully have more time to play around with it this coming weekend. Any tips on refining the focus would be greatly appreciated; the exposures are approximately 40 s. 

Jim 

 

 

[Merlin66]

Jim,

Promising start....

I'm a little surprised it was a 40 sec exposure, I would have though much less.....

What slit gap were you using? Around 20 micron would be a good start......

Have you checked the focus of the collimator to slit plate?

With a large chip (DSLR?) concentrate on the centre of the FOV, don't worry about the edges (yet!)

Softly, softly....I'm sure you'll have success.

Ken

 

[saac]

On 23/04/2020 at 23:34, Merlin66 said:

Jim,

Promising start....

I'm a little surprised it was a 40 sec exposure, I would have though much less.....

What slit gap were you using? Around 20 micron would be a good start......

Have you checked the focus of the collimator to slit plate?

With a large chip (DSLR?) concentrate on the centre of the FOV, don't worry about the edges (yet!)

Softly, softly....I'm sure you'll have success.

Ken

 

Thanks for the suggestion to recheck the collimator position Ken, I'll have a go at that. Yes I was a bit surprised by the exposure times as well - I was using the narrowest slit position.  I've installed my new lens (fl 100mm) so focus should now be achievable with the spacers I have.  I've also swapped out the focusing screw for a micrometer head - it's a lot smother and in theory will provide better control. Silly question, when attached to the telescope does position of the draw-tube have a role to play on providing focus. I'm guessing it should be set to focus at infinity would that be correct?  From playing around with it today I have a feeling that my focus position is on a knife edge  - quite tricky finding it!

Jim 

Edited April 28, 2020 by saac

[Merlin66]

Jim,

OK. Focusing the spectrograph on the telescope is a three stage process.

1. Set the guider to focus on the slit gap. This can be done in subdued lighting and should ensure the telescope is focused on the front of the slit gap (see #2)

2. Adjust the telescope focuser to bring the target star (or any star really) onto the slit in tight focus, as viewed from the guider. This should give you the thinnest spectral line only a few pixels in height.

3. Focus the imaging camera on a reference line close to your target wavelength. Aim for a minimum FWHM, around 3 pixel would be good. This means the imaging camera is well focused on the rear of the slit plate gap. Depending where you're targetting within the spectrum, you'll find you need to re-focus the imaging camera to account for chromatic/ field curvature. I always take a reference image immediately prior to taking a target image and measure the reference line (Bass Project/ Measurements) to determine the resolution R value. You'll need this reference image for wavelength calibration.

The telescope (hopefully) should maintain focus onto the slit gap, so moving to different targets just means checking the imaging camera focus.

Standardise on a sub exposure length, to suit your mount's capabilities (and your guider accuracy -PHD etc.) I generally use 240 sec subs. The total exposure will depend on the target magnitude, look at the sub's profile (I use AstroArt) to check the max ADU - shouldn't be saturated....go for as many subs as you can to improve SNR. I usually aim for 10 subs - total exposure 2400 sec ( 40 min)

Any questions just ask.......

 

[Paul Gerlach]

Jim,

Would this not create a lot of force on the micrometer head? Considering you are using two springs. How do you keep the micrometer head in place?
I see you had a lot of warping issues during printing. What material did you use?

Paul

[Merlin66]

Any updates?

I would be nice to see some results from the work and effort being expended on this great project.

Ken

 

[Paul Gerlach]

Well I'm still thinking about how to tackle the design of the calibration unit. But it still has not resulted in any concrete designs.  It will be a ALPY-like design that can also be used with other possible future spectroscope projects.

First I had the idea to use a small solenoid to place the reflector into position. But then I abandoned it because I think it will not put the reflector in the correct position repeatedly. So I'm back with a micro servo which I didn't want to use in the first place because I didn't want to introduce a Arduino board just to control it. But yesterday I discovered the Sparkfun Servo Trigger. This will simply control the micro servo and rotate the reflector in the correct position.

Now the idea is to create a calibration unit that can be controlled via simple tumble switches or via an external relays switch board. I'm a electronic noob so I hope to get some help on this and other fora.
Okay, so the main power supply is at 12 volt. Now the Sparkfun servo trigger and the micro servo operate at 5 volt so I have to bring it down from 12 to 5 volt... uhhh. Well I did some googling and after a few iterations in search description came at a 7805 voltage regulator which is a small electronic component. Now small is good. I don't want to end up with a bulky contraption.

But is it a good choice? I don't know. Hopefully someone with more knowledge can help.
The 5 volt can than be used to power the Sparkfun servo trigger and micro servo. The 12 volt will power a cheap Chinese DC-AC inverter that will produce the required voltage for the RELCO and/or neon bulb.
I accidentally ordered 15 (!!) of them so I committed to use them 😉

Ken wrote that he would like to see an option of incorporating a RELCO and neon bulb so you can choose (RELCO for low resolution 4000 - 7000 Angstroms and neon for high resolution H-alpha work). And do we need a halogen bulb for flat field?
Can this be controlled with a simple three position tumble switch? So center position = off and the other positions for neon and RELCO? But wait! It's also nice to have the reflector in position and all the bulbs off to easily create dark frames. You see my predicament.... HELP!

 

Paul

[Gregj888]

Though I have visited often over the years, just joined and my first post here in the Lounge. 

First, Paul.  the 7805 acts like a variable resistor to cut the voltage.  that means it's a bit of a power hog.  Fine if plugged into the mains not so good on batteries.  EBAY has a number of small DC to DC high efficiency converters that are cheap.  I did a review on one a while back and can find a link if you need it.

Forgot to add, if you use a 7805, make sure to put a capacitor on the input and output pins to ground ( 10 to 20 mfd say 25v, Tantalum would be preferred but not required, actual value is that critical) to keep it from oscillating.

Posting here because I started a LowSpec print.  New to 3D printing and my first ASA print (slider block) took a few tries.  Bumped up the top and bottom thicknesses.  Finished the bottom then warped and popped off.  Printing the turret and lens holders now.

Ender 3 Pro in a DIY (PVC pip enclosure.

Great thread, thanks all...

 

 

Edited May 8, 2020 by Gregj888

[Thalestris24]

1 minute ago, Gregj888 said:

Though I have visited often over the years, just joined and my first post here in the Lounge. 

First, Paul.  the 7805 acts like a variable resistor to cut the voltage.  that means it's a bit of a power hog.  Fine if plugged into the mains not so good on batteries.  EBAY has a number of small DC to DC high efficiency converters that are cheap.  I did a review on one a while back and can find a link if you need it.

Posting here because I started a LowSpec print.  New to 3D printing and my first ASA print (slider block) took a few tries.  Bumped up the top and bottom thicknesses.  Finished the bottom then warped and popped off.  Printing the turret and lens holders now.

Ender 3 Pro in a DIY (PVC pip enclosure.

Great thread, thanks all...

Good luck with your build!

Louise

[Gregj888]

Louise, thank you and great work on your build.

 

[Thalestris24]

2 minutes ago, Gregj888 said:

Louise, thank you and great work on your build.

 

It's still a work in progress and put to one side for now

[Paul Gerlach]

10 hours ago, Gregj888 said:

Though I have visited often over the years, just joined and my first post here in the Lounge. 

First, Paul.  the 7805 acts like a variable resistor to cut the voltage.  that means it's a bit of a power hog.  Fine if plugged into the mains not so good on batteries.  EBAY has a number of small DC to DC high efficiency converters that are cheap.  I did a review on one a while back and can find a link if you need it.

Forgot to add, if you use a 7805, make sure to put a capacitor on the input and output pins to ground ( 10 to 20 mfd say 25v, Tantalum would be preferred but not required, actual value is that critical) to keep it from oscillating.

Posting here because I started a LowSpec print.  New to 3D printing and my first ASA print (slider block) took a few tries.  Bumped up the top and bottom thicknesses.  Finished the bottom then warped and popped off.  Printing the turret and lens holders now.

Ender 3 Pro in a DIY (PVC pip enclosure.

Great thread, thanks all...

 

 

Thanks for your comments and advice. A DC to DC converter will mean an additional board. I already have two (DC to AC and the Servo trigger) and want to keep things compact. But I'll have a look. The 12 volt power supply will come from a adapter plugged into the mains.
I've seen some schematics with the 7805 and some capacitors on Google.

Printing with ASA can be a bit challenging. An enclosure is a good start. Bed temperature 80 - 90 degrees Celcius, First two layer at 250 degrees then gradually drop it to 235 - 240 degrees and small amount of fan (15-20%) just to mix the warm air a bit. With large objects I sometimes use a raft. It lifts the object from the hot bed so there is less temperature difference between to and bottom. I print on a flex bed with a scuffed sheet of PEI.

[Thalestris24]

1 minute ago, Paul Gerlach said:

Thanks for your comments and advice. A DC to DC converter will mean an additional board. I already have two (DC to AC and the Servo trigger) and want to keep things compact. But I'll have a look. The 12 volt power supply will come from a adapter plugged into the mains.
I've seen some schematics with the 7805 and some capacitors on Google.

Printing with ASA can be a bit challenging. An enclosure is a good start. Bed temperature 80 - 90 degrees Celcius, First two layer at 250 degrees then gradually drop it to 235 - 240 degrees and small amount of fan (15-20%) just to mix the warm air a bit. With large objects I sometimes use a raft. It lifts the object from the hot bed so there is less temperature difference between to and bottom. I print on a flex bed with a scuffed sheet of PEI.

Hi Paul, if you don't need much current (<=100mA) then the little 78L05 will do There may be other alternatives if you need higher current.
https://components101.com/78l05-pinout-equivalent-datasheet

Louise
 

[saac]

On 29/04/2020 at 11:04, Paul Gerlach said:

Jim,

Would this not create a lot of force on the micrometer head? Considering you are using two springs. How do you keep the micrometer head in place?
I see you had a lot of warping issues during printing. What material did you use?

Paul

Hi Paul, the spring strength of the springs is not so high as to cause any problem with the micrometer and it does return the lens assembly nicely when backward focusing.  At the moment the barrel of the micrometer is in an interference fit with the hole in rail-holder block. I had to ream out the hole in the rail-holder a little to accept the larger diameter of the micrometer barrel. What I would like to do is re print the rail holder block to accept and secure the micrometer properly, perhaps including a grub screw to secure the micrometer in the block.  The measuring face of the micrometer then simply pushes against the threaded insert inside the other rail-holder block; It all seems to work quite smoothly.  I wonder, and I hope I'm not being too cheeky here but would you be able to provide a copy of the stl file for the rail holder blocks - that would be an easier starting point for me. I understand if your not happy to do this though. 

Yes the base and lid of my print show signs of warping. This was the first long print run I had undertaken and after an initial hiccup on the first run I decided to print it continuously over night - I can't remember exactly how long but it was the best part of 24 hours. I think I the base took too much heat , perhaps I should have broken it down into shorter print runs (my printer allows for interrupts).  The filament I used as PLA; once I have this once shaken down I'm going to print your Low spec 3 version. 

Jim 

[Paul Gerlach]

Jim,

Source files of the LOWSPEC 2 and 3 can be found on Thingiverse:

https://www.thingiverse.com/thing:2455390/files

Paul

[Jagho]

On 16/03/2020 at 19:58, saac said:

Thanks very much Paul, I've downloaded the T2 thread plugin that you made for Fusion 360

Jim or @Paul Gerlach, could you show the link I can download this plugin from, please?

 

Edit: OK. I've found it. 

Edited May 22, 2020 by Jagho

[saac]

On 22/05/2020 at 11:06, Jagho said:

Jim or @Paul Gerlach, could you show the link I can download this plugin from, please?

 

Edit: OK. I've found it. 

Hi Jagho, here's the instructions Paul posted - it was either on this thread or the 3D printer , I tried finding the original post but I couldn't locate it. Anyway  I copied the original instructions onto a word document.  It worked a treat when I installed it but some reason Fusion is no longer accessing it for me so I'll have to go through it again. 

 

ps - and here's Paul's original thread  - I think you need it for the file instructions ,     

 

Read Me - Fusion Autocad Threads.docx

Edited May 24, 2020 by saac

[Thalestris24]

Just now, saac said:

Hi Jagho, here's the instructions Paul posted - it was either on this thread or the 3D printer , I tried finding the original post but I couldn't locate it. Anyway  I copied the original instructions onto a word document.  It worked a treat when I installed it but some reason Fusion is no longer accessing it for me so I'll have to go through it again. 

Read Me - Fusion Autocad Threads.docx 1.37 MB · 0 downloads

I think you have to reinstall it every time Autocad does an update...

Louise

[saac]

On 09/05/2020 at 20:58, Paul Gerlach said:

Jim,

Source files of the LOWSPEC 2 and 3 can be found on Thingiverse:

https://www.thingiverse.com/thing:2455390/files

Paul

Paul, sorry I should have looked there first, I forgot you had already provided the source files, thanks.  I made an extension block to the focuser railholder (b block) to give the micrometer a little more support, again held by an interference fit.  In truth my micrometer head is perhaps a little too big,  a smaller one similar may have been more suitable.  I'll post a photograph up later.  

[saac]

11 minutes ago, Thalestris24 said:

I think you have to reinstall it every time Autocad does an update...

Louise

That would make sense Louise , it went through an update for me last month - ouch that's a wee bit annoying then but it is worth it. 

Jim 

[Paul Gerlach]

50 minutes ago, saac said:

That would make sense Louise , it went through an update for me last month - ouch that's a wee bit annoying then but it is worth it. 

Jim 

Yes, it's very annoying. Every time Fusion 360 is updated, it gets a new 'profile folder' in this location

C:\Users\username\AppData\Local\Autodesk\webdeploy\production

Within the profile folder the threads are located at:

..\Fusion\Server\Fusion\Configuration\ThreadData

The standard threads are copied to the new location except for any custom thread files. You'll have to copy them yourself.

 

[Thalestris24]

1 minute ago, Paul Gerlach said:

Yes, it's very annoying. Every time Fusion 360 is updated, it gets a new 'profile folder' in this location

C:\Users\username\AppData\Local\Autodesk\webdeploy\production

Within the profile folder the threads are located at:

..\Fusion\Server\Fusion\Configuration\ThreadData

The standard threads are copied to the new location except for any custom thread files. You'll have to copy them yourself.

 

Even more annoying, perhaps, is that you have to remember to copy any custom threads. As it happens I've not needed to print any T2 threads in a long time so haven't bothered to add any custom threads. But who knows what the future holds? 😄 

Louise

[Paul Gerlach]

I've made some small changes to the lid. Removed the logo and changed the beginning of the thread. Now it's possible to print the lid face down so it's much easier to print. I also made the grating holders somewhat higher and put more thread on the grating holder caps (already on Thingiverse).
With these changes and by simply adding a metal washer (see picture) you can now fixate the grating position by tightening the grating holder cap and screwing the micrometer a bit back. The idea is that spectral drift due to thermal expansion or contraction of the micrometer is eliminated.

 

[Gregj888]

After a delay to figure out how to print ASA on an Ender2 Pro, did some printing over the last few days.  Not perfect but not bad.

Still playing with the setting.  Polymaker Polylite ASA, hot end 142c, Build plate glass at 110.  The two big changes were the glass build plate so I could go to 110c and ASA Juice (same as ABS Juice but with ASA scrap).   Note I did print the older file face down with Tree support in Cura. 

Wish me luck.  I'm starting the 2.5 day print of the body in the morning.