Rolling my own HSG thanks to santa :)

I LOVE finding out about different ways to appreciate the Sun and light in general. Use this forum to post your info or questions about various outside the mainstream ways to appreciate our life giving star!
Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Hi Walter - my pleasure ;) it's arrived this morning.

Here's the layout with the pieces in place for the basic design:


Scope: VIxen A80Mf - a 80mm 910mm fl f/11.3 achro
Thorlabs adjustable slit with micrometer (10um fixed slit next it it)
Small black lens: Cannon 300mm f/5.6 prime as collimator
Grating 50x50mm 1200lpmm 500nm blaze reflective
Larger black lens: Cannon 300mm f/4 prime as focusing lens
Cameras
* Red square - ATIK 383L mono
* Red circular - ATIK 4000 mono
* Blue circular - ATIK Titan

Here's the optics side by side..

Left to right - 300mm 5.6, Vixen A80mf, 300mm f4

Both cannon lenses have retractable shields and the f/4 has a built in tripod grip and teleconverter slit (there's a lens that pops out). I'm impressed … when not on solar duties.. the F4 may be piggybacking the Pentax 105SDP!

For a close up - here's the adjustable slit:


It's a phenomenal piece of engineering in micro size!


Those keen photographers will note that the lenses are Cannon FD fittings (not the modern EOS) and are manual focus. There are FD to EOS and EOS to T-thread fittings around. This isn't a problem for me - the only thing I need todo is retract the iris (this occurs when the connection ring is rotated on attaching to the camera).
Costs for the lenses from cameraworld.co.uk:
£25 for the 300mm f5.6
£125 for the 300mm f4
Next day delivery - fast and great service so I'm recommending them as a good source of lenses!


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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick

thank you very much. Impressive, impressive


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

No problem :)

There's a few little improvements I could make along the way foliowing phase 1.. in my design I'm attempting to stay well over 10K resolving power and below 0.65A spectral resolution to see some surface details.

a) I'll start with 300mm collimator then I'll find a Cannon 2X-A teleconverter that will bring the collimating lens up to 600mm.
This will upgrade the spectral resolution from 0.64A with 10197 resolving power (38x38mm image on grating) to 0.48A with 13741 resolving power (53x53 image in grating - hence the far batter spectra).

b) switching to 1800 l/mm also increases the performance - the number of lines simply adds more oomph to the spectra:
If I put the 2x in there from step (a) this will now take it to 0.28A and 23480 resolving power.
If I miss out (a) and still use 300mm collimator then this will be 0.38A and 17423 resolving power.

The final iteration of the two improvements above and replacing the Vixen with the Pentax 106 SDP and the TV 2x giving a 105mm aperture APO with 1340mm focal length (f/12.76) doesn't improve the resolution - remains 0.28A at 23360 resolving power - but does boost the resolution in terms of the image itself (based on white lighting and general DSO work). However although I use the Pentax for whitelight, I'm still very reserved about using it direct in this fashion. Going off topic - here she is doing some solar whitelight:



I've written the ATIK drivers for the mac (not the day job but my past I was a ye-olde software developer) and as part of an example application done FFT based alignment and realtime stacking. So I will be interested to see what I can get put together to support it on the software side.


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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick

what a fine gear


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

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Re: Rolling my own HSG thanks to santa :)

Post by marktownley »

Lots of nice toys! 8)


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Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Just tried the f/5.6 on the titan pointed at the curtains in the other room. No solid connection just sat behind the lens.



Can't wait to get everything assembled but today was 13+ hours of DIY.. and tomorrow is going to be something similar! If all goes well I may get a basic spectra test with the F4 pointing at the grating.


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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick

a fine result from the first test


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Re: Rolling my own HSG thanks to santa :)

Post by marktownley »

Good luck with the DIY, let us know how you get on :)


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Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Managed to have a play this evening. I picked up some aluminium pieces and sheeting to make the body, grating holder etc, so I thought I would get something going by setting everything up on the floor and get a feeling for the alignment and what needs to be alterable.

I have managed to get a lovely rainbow from an LED lamp but.. the light is so broad spectrum I can't see any lines! So one option is to try an old chilli grow lamp I have - I have two 400W bulbs: high pressure sodium (that street lamp orange) and Metal Halide (a stark cold light that is rich in blue) that may be better in giving me some lines.. but I need to find the bits in the garage first!

Next is the alterability of the focusing lens or the rotation of the grating - I think this would be better with a rotation of the grating with the only slight side effect on the cross section area of the grating exposed to the collimating lens.



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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick

that looks very wild at the moment ;)


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Hehe - I know but this is part of the measure twice to validate the ideas before starting cutting. The obvious difference here is the object focal point. I have also found old dead hard disks have some great bearings that hold the HD data read/write arm steady (made from alu alloy) that should work nicely for the grating holder. I'll also need to make a separate box for the scope->slit->collimating lens portion.

Plan is to use alu rivets and metal epoxy rather than welding. I'll then cover internally with flocking material. I've selected square section U shape to give rigidity to the main axis support and I may add a second section in to supplement the rigidity at a later date.

So far the scope, two lenses, camera, plus all the alu in it's raw form comes to about 5-6Kg so I figure by the time it's done it's going to be about <10Kg which is perfect for the EQ6 I'll mount it on.

Now to finalise the design and make the first cuts :)


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Re: Rolling my own HSG thanks to santa :)

Post by Wah »

Bearing from old HDD seems to be a good idea, how to fine tune the grating angle for band pass selection?


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

I managed to get some additional work done on the casing:

Phase 1 layout with some foam (~2"x2") as the grating:


Phase 2 layout with the foam being the two mirror scanner and


Riveting stuff!




So this is what it will look like with the lid on:


I still have more riveting todo but the general form is there - total weight so far with lenses, camera, scope and the lid is 7kg so that's on track.


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Re: Rolling my own HSG thanks to santa :)

Post by marktownley »

Impressive stuff!


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Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Bearing from old HDD seems to be a good idea, how to fine tune the grating angle for band pass selection?

That's the idea.

I'll also have to make a mechanism to be able to fine tune the alignment too - probably using plastic thumb screws like reflector collimation screws.


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Impressive stuff!

Hehe the cutting would have been more impressive if I had a proper cutting bench - instead I used a metal bit in a jigsaw and cut by hand. There's a few gaps etc but those will be covered when I get some flocking in place.

I have enough metal left over to create some internal bits so those smaller bits will be next after I have all rivets put in place - that's why the sides are slightly bowed as they need a few more.


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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick


great, you have jumped a big step forward


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

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Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Looking at Peter's spectroscope internals got me thinking about the cage to hold the grating that allows both pitch and yaw rotation - so here's my thinking:



Top view is looking down with the HD bearing that allows the tuning to select the wavelength.

Middle - looking at the side with the HD bearings at the top and bottom, you see the triangle pivot for vertical alignment. This is held in by pressure from two screws at the back of the cage and so it's possible to adjust the vertical alignment using the screws to vary the pressure. The grating (rainbow block) is backed by a alu backing for the screws to push against and the top+ bottom points for the triangle to hold in place. The top part of the frame isn't shown here but the bottom is.

Bottom shows the top view is without the top of the cage and HD baring showing the how the top & bottom of the cage press against the triangle pieces so that any alignment is as close to the face of the grating as possible (to keep as close as possible anyway!).


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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick


very neat


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Hi, I'm looking for a bit of advise in terms of effect of positioning of the focusing lens and grating.



I've used the sim v4 xls to provide alpha and beta angles for a set of reference wavelength for Order 1 (spectra range in brackets):
3000 (509A)
3938 - Ca K
6563 - H alpha (476A)
8972 (436A)

I've also included a reference for Order 2 Ha (159A range!).

Now the question - how much difference does an optimal Ha positioning have on a CaK rotation? I know that the grating area facing the incoming incident beam will not be optimal but is it worth


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Think I've answered my own question by trying it with the grating - rotating it will work however I'd suspect the down side is it's not 100% optimal… but hey :)


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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick

now that gets complex.


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Re: Rolling my own HSG thanks to santa :)

Post by marktownley »

No idea about offering advice but it sure is fun to watch this develop!


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Re: Rolling my own HSG thanks to santa :)

Post by Nick »

I noted that the SIM V4 xls sheet indicated angles a = angle b - on further inspection row G18 "Collimator/Camera -Total angle" was set to 0. As this is isn't a lithgow configuration then I I'm suspecting this should be the blaze angle for highest efficiency at the the blaze frequency (i.e. for my grating 5000A blaze (ref A) at 17.45 degrees, this gives a=26.44, b=8.90 rather than a lithgow a=17.46 & b=17.46).


Hmm… before using the xls, I calculated non-simetrical values.. going to calculate/measure again before making any heavy changes! My original manual calculations for 500nm gave a=+26.36 and b=-8.96, so a+b= 17.4.

Infact if order 0 is a=b .. so I definitely know that the xls for order 1 should have non-simetrical values..


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Re: Rolling my own HSG thanks to santa :)

Post by Merlin66 »

For the classical design, the size of the lenses dictate the lowest possible angle between them - the lower the angle the less anamorphic distortion.
It's usual to see angles around 35-40 degrees between lenses.
The rotation of the grating, to bring the various wavelengths to the centre of the imaging camera FOV, is standard - I use a 25mm micrometer head to control this movement.


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Re: Rolling my own HSG thanks to santa :)

Post by Merlin66 »

Nick,
The attached SimSpecV4 shows your arrangement:
I've assumed a slit gap of 20micron, a total angle of 38 deg and pixel size of 8.3 (you can change this to suit your camera)
It shows the grating sits at 43.6 deg to the optical axis and for an f10 beam requires a 30mm x 50mm grating size - this is non standard so a 50 x 50 would be needed.
HTH

Nik_SimSpecV4_1c.zip


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Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Thanks Merlin :) The grating is a 2"x2" .. when I played with the figures it works out as 58mm but considering the edges of the vixen aren't going to be stunning I figured that even with tilt that this grating would be a good all rounder.

I was playing with the 36degree angle to check it before doing anything with a rivet gun and jigsaw I would later come to regret. The alu bar is marked out with the final locations of the grating, slit and lens so this is looking good.

Once I got beyond the fact that this was lithgow by default things started to make sense (and some coffee).

I took an photo using the DSLR - but at the moment I'm hand holding the grating until I have made the cage hence the image is difficult to see (and I don't think the Mrs would really like me attempting to align the FD onto the EOS body in the dark with the FD aperture lugs pointing dangerously at the EOS!)



The top and bottom bright spectra is because the light can get past the slit (see the last picture). The dimmer spectra is the slit :D

For those that may have seen the v2 (second time the upgrade has munched it :)).. it's the new proposed (green) camera location.

So I'm happy with the calculations.. next up is to get the components bolted onto the optic axis (the box is also bolted on but not there to provide the rigidity.

Here's the test setup



I forgot to say that I will be adding a 2x to the 300mm f5.6 so this will make it 600mm f/11.2 which matches the Vixen (f/11.3) and a reasonable match to the Pentax with the 2x on (1340mm f/12.6). However for now. it's good.


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

I also managed to get to the bearing of the HD read/write heads:



These are extreme precision and very very light!


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Still got a little way to go but here's a zero order image from the test set up using the 383L.



Get a spectrum, however the camera isn't picking up any lines.. but I think this may be down to focus.



Also have the final bits of alu.. next up I'll sort out some of the mountings.. The good thing this has shown the need of both accuracy and the ability to tinker with the distances.


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Re: Rolling my own HSG thanks to santa :)

Post by Merlin66 »

Nick,
That slit image looks about 3metre wide!!!!
Ideally it should only cover 2-4pixel on your camera....
Reset the slit gap and try again.


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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick

congratulations on the first light, even if it is not what you expected. It is still a first light. I can see it :-)


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

After a hectic weekend.. however the garage is clear.. so that gave me the opportunity to try out my light sources :D

High Pressure Sodium 400W bulb at full tilt:


Metal Halide 400W bulb at full tilt:


I also had a thought about the phase two - adapting the scanner - it's possible to fit it (mirror rotated 180) to a modified Lithgow design with a single collimating/focusing lens.. hmm interesting options for phase two..



I still to think more but I think this will work.

Attached files


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

I've been holding up making the next step of securing the components because I've been thinking of the best way todo it. In short I wanted to add some ability to allow adjustment.

I'm going to use a frame of 4 alu rods and clamps, for example:


For some components, the adjustment can be done by rotating a screw with a spring applying opposite force:


The frame will then be clamped to the rails though the side of the spectrometer - thus making a rigid axis on which to mount components.


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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick


what a light power.


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Hi Merlin - I may need to pick your brains..

The attached image is a Thorlabs fixed width 10um slit with a torch on the other side, going through a f5.6 300mm lens, then being reflected off the grating at order 0 before being focused by the f4 300mm and finally imaged by the 383L with bin 1x1 (5.4um pixels). I get the same with the variable slit.. just continuous spectra without hints of lines.



I'm not getting much luck with binning 2x2 or switching cameras with 7.4um pixels :/

I would have expected to see some variation in brightness.. could the collimator be too far from the grating? (in theory this shouldn't matter because the light should be parallel.. unless both lenses are compensating by being focused for non-collimated light).

I may try running with a 2x power mate to make the collimator 600mm, however surely this would simply increase the wise of the slit?


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Re: Rolling my own HSG thanks to santa :)

Post by Merlin66 »

A couple of things
1. A halogen lamp has no spectral detail - it basically a "flat" Black body continuum....what you need to use is an energy saving fluoro.....
2. The zero image is well over exposed - that's why I think it's looking sooooo wide.
3. The tapered slit gap shows the optics are mis-aligned.
4. Providing the grating is set correctly with the top edge blaze arrow pointing in the direction of the imaging lens, you should obtain a spectrum. As I said the fluoro lamp is the easiest to use and has some good emission lines in the blue yellow and red.

Hope this helps.


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Re: Rolling my own HSG thanks to santa :)

Post by Wah »

Have you tried other light source? I know tungsten/led torch won't give you any spectral lines.


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Thanks you both! I forgot to say that the image was auto stretched in PI so you could see the focus is good and the slit size easily - but looking at the area of light compared to the slit size itself.. it still looks overexposed on the non-stretched - perhaps order 2 will work because if it!

The 383L is a kodak full frame sensor so has a mechanical shutter which, from experience, needs about 3 seconds to not make any shadow in the corner of the image. At 0.01 etc it's looking like there's still too much light. I was using this camera because it's square and sat on the desk nicely :D (optimistic!)

I tried the little titan - it is my usual solar camera as it's sony chip gives fast exposure and frame rate without the need for a mechanical shutter. The slit was large but I found a long exposure bug in my own drivers - nothing like dog fooding! The disadvantage for desk use is it's cylindrical. Next to try is the 4000 - an electronic shutter, but the frame rate is slower - cylindrical again.

Once I have an observable spectra I'll start making the final holders for the components - but for now it's all bench setup so all the off centre optics etc are a given! It was a howling gale so I couldn't setup in the garage with the two large lights.. so I'll get myself a energy saving bulb as the house friendly option!


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Ok, I've fixed the issue in the titan (and improved image quality for it).. but here's the zero order without stretching:





I found a CFL bulb but I don't have a lamp that will take it grr..

Sooo close lol.


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Re: Rolling my own HSG thanks to santa :)

Post by Merlin66 »

That looks better!
You just need to ensure the alignment of the slit to the grating direction and rotate the slit image to the vertical.
(The tapering off of the light at the top may be due to the misalignment of the slit to the light source ( a diffuser over the end - greaseproof paper? would assist at this stage)or vignetting in the optics.....
Onwards and Upwards


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Re: Rolling my own HSG thanks to santa :)

Post by Nick »

I see the thread made it across (almost intact - some images are a bit confused lol).

I have just ordered a drill mill .. attempting to drill accurate holes by hand held bosh really wasn't cutting it. The project is getting there - I spent an afternoon evaluating how to create the design - hence the experience leading to a drill mill. I figure I am now into negative brownie points with the mrs.. today of all days..

The idea is to have this complete by end of march for the SGL star party :)


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

I've spent some time today getting some of the internal cage progressed.

Now this is just a simple mock up - no solid revetting and just bolts on the side.
IMG_1774.JPG
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The idea is to get a skeleton done - there's some filing todo as the cut has one side slightly too large. The final version will have additional plating to add structural integrity.
IMG_1775.JPG
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Now I did say it needed some final filing.. you can see here it's not quite fitting :)
IMG_1776.jpg
IMG_1776.jpg (2.86 MiB) Viewed 4578 times
But this is the main structure. The final version will be wider.


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swisswalter
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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick

that looks great :bow


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

I've decided to go for a skeleton to start with - it allows easy access to adjust things.. after which I can then mount in the box I've created earlier.

So this weekend saw a rather large amount of progress..

The adjustable grating cage
IMG_1777.JPG
IMG_1777.JPG (549.17 KiB) Viewed 4550 times
Fully adjustable lens mount to allow collimation:
IMG_1778.JPG
IMG_1778.JPG (445.53 KiB) Viewed 4550 times
Front:
IMG_1779.JPG
IMG_1779.JPG (492 KiB) Viewed 4550 times
Current simple screw held slit - this is pending more work. The single piece of aluminium will be doubled up on the top.

I've fabricated two more adjustable lens holders for the focusing lens and I'll make a camera clamp to hold securely.

I think an afternoon at some point and this will be ready for first light..
Attachments
IMG_1780.JPG
IMG_1780.JPG (437.42 KiB) Viewed 4550 times


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Ok, attempted a pseudo first light with the cannon Ixus80 just to see what the current form will give.

Firstly - the slight is orientated 90 deg out.. stupidly this occurred to me as I was building it.. no biggie so I rotated the grating 90deg (just for now) and pointed it at the ceiling light.. which just so happens to be a energy saving FL..

Got spectrum! WIth the above noted - hence the non-straight nature:
IMG_1787_Preview01_firstlight.jpg
IMG_1787_Preview01_firstlight.jpg (878.5 KiB) Viewed 4545 times
Looking at it visually - there's more lines in there.. so the better resolution cameras will be better :D
Last edited by Nick on Sun Feb 23, 2014 9:22 pm, edited 1 time in total.


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Re: Rolling my own HSG thanks to santa :)

Post by swisswalter »

Hi Nick

good Progress. Good luck on the finish


Only stardust in the wind, some fine and some less fine scopes, filters and adapters as well. Switzerland 47 N, 9 E, in the heart of EUROPE :)

from 7 am - 7 pm http://www.nanosys.ch

from 7.01 pm - 6.59 am http://www.wastronomiko.com some times vice versa ;)
Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

swisswalter wrote:Hi Nick

good Progress. Good luck on the finish
Thanks :)

Ixus only takes jpegs but.. looking good
IMG_1790.jpg
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Re: Rolling my own HSG thanks to santa :)

Post by Wah »

You may need to rotate your slit to let the spectral lines perpendicular to the spectrum.


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Wah wrote:You may need to rotate your slit to let the spectral lines perpendicular to the spectrum.
Yup - the slit needs 90 degree rotation and I need to add the final imaging lens+camera support. These shots were just to verify it was working - but it's looking good.


Nick

Re: Rolling my own HSG thanks to santa :)

Post by Nick »

Here's the grating in the holder:
IMG_1791.JPG
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Now tonight, as I worked from home and looked after a sick mrs.. it meant that I could get down to the task at 1830.. I look at my watch and it's 2200!!

I have now made a basic modification for the slit, rotating by 90 deg as required and providing some adjustment. I'll sort out something a bit more secure and adjustable later.. but for now an L piece of wood will suffice:
IMG_1794.jpg
IMG_1794.jpg (592.56 KiB) Viewed 4517 times
Now the lower components were assembled, with two holders for the cameras - one for the larger diameter 383L & 4000, the other for the smaller Titan and 16IC:
IMG_1796.JPG
IMG_1796.JPG (510.28 KiB) Viewed 4517 times
Not the bottom isn't in it's final position but simply resting against the upper section to give a indication of how it will fit together :)

I still need to make a couple of holder pieces etc but for tonight that will do!

I've also managed to (a) get a bulb holder for a CF so I can put in on the desk .. but (b) managed to find a electrician's screw driver.. with a neon bulb in it.. I hope to have everything put together and aligned for a proper first light tomorrow.


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