Thalestris24

Well, I've reversed the slit but I don't think it's made much/any difference. It's hardly exposed on the grating side anyway. With the slit illuminator part in place there is only a large slit-sized aperture visible from the grating side. Also, the edge slit size markings now no longer make any sense... I've taken a sequence of images whilst turning the micrometer. From 0 deg i.e. plane to the camera lens (from the first sight of spectral features) up to what seems to be the max - about 20 deg. (a to k): First (a) Last (k) The spectrum obviously shifts to the left with the clockwise micrometer rotation. I can't see a zeroth order? a-f seems to cover the first order? It's still slanted - I've no idea why! Louise

Tut!

Hi again Yes the shinier side is towards the collimator. The other side with the reverse numerals is also very shiny though. Obviously the lasers and the 75W cfl are very bright and there is the problem I mentioned with the light catching and scattering from the tip of the guide mirror older. I'll have a look at that tomorrow and try and get a better alignment of the slit on the guide mirror + guide cam. Cheers Louise

Haven't found the green laser pointer but found my Kensington wireless presenter with red laser pointer. I don't have any spec for the wavelength but it's pretty bright so I think it's 635nm. Here's a messy spectrum - I think you can tell pretty much where the line is. Again it's slanted a bit - weird! I've noticed the lasers catch on the tip of the guide mirror holder. I'll have to try and do something about that. Off to bed now! Louise

Very kind of you It picks up the broad spectrum of my nominal 365nm UV torch as a bright, wide, well, sort of a rectangle! I think that it is brightest between 360 and 375nm. I'll have a search for my green laser tomorrow. It's here somewhere... I could also try one of the neon bulbs I bought - needs a little soldering to put a resistor in series . Not particularly bright but I think they have a characteristic spectrum at the red end. Louise

Oh ok - Was just about to send... Let me know if image is good enough Thanks Louise

Got it, thanks Give me a few mins - it's on another PC

That was a full size image - must have got altered by the upload... Yeah not sure why the laser line is a little slanted. Maybe because I had to point it at angle. I did the shortest exposure possible - 250ms and that was with the 10nm slit. I can email the image but don't have your address? Louise

I'm a bit in the dark about finding where I am but I'll have a go tomorrow. Meanwhile, here is a full size CPL image together with a 405nm laser line I just did. Maybe adding that point helps make sense of it? Hope uploading to SGL doesn't mess the image up! Louise

Hi Ken Thanks! Yeah, I realise it was saturating at one end but I'd lose the fainter lines with shorter exposures? I'm not sure which way round it should be - it's as it came out of the Atik/SharpCap. Maybe it's the wrong way round? For display purposes it's reduced to 40% of it's original size (and cropped) so that will have affected the number of pixels. I have a 405nm laser so can see where that shows up. Also have a green laser somewhere, probably a red one too! I'll have a play with them tomorrow. I don't want to handle the grating unnecessarily - I'm clumsy and have little grip so keep dropping things... I'll have to get to grips with BASS now that I'm partially up and running . Also I didn't really try adjusting the micrometer so that's another variable. Thanks again Louise

Took the plunge and put the Thorlabs grating in! Unsurprisingly - much better results! Also went back to the 87mm lens - after all that fiddling and getting the spacing right with the 125mm lens, tut! Oh well. It was a bit confusing because the grating had the arrow on its bottom edge rather than the top edge as depicted in the assembly guide. Seems to work ok . I'm not sure how much of the spectrum I actually have in a single frame. According to Simspec (v4.3), with the Atik383l+ at 87mm and using the 20um slit, I should be picking up 3785 to 7215A i.e. 343nm and from near UV to near IR. Also, with a spectral resolution of just under 3A. Here are some results with the 20um slit. First just with slit directly illuminated by the CFL. Second using a 500mm lens and focusing on the CFL placed in another room - about 6m distant. Have converted to jpg and reduced to 40pc size: Just CFL, 8s exposure: CFL + 500mm Mirror Lens (F6.3), 10s exposure: Not sure if the lens focus was a bit off or if it's something to do with it being a distributed source. I didn't change the Lowspec camera focus between the two setups. I had noticed in testing with the CFL that differences in the position of the bulb appears to affect the focus. Maybe the source brightness is also causing the 'ghosting'? Later, I'll try with the yellow street lamps again (about 150m distant). Louise

Hiya "I must say I'm a little surprised that your "DIY grating" is giving you a result....." - I know, the transmission grating is just taped to the front of one of the craft mirrors which are no way 'optical' quality. Still, would be ok for testing, I thought. I'm still fiddling - trying to get the guide scope + mirror focused and oriented has been a bit of a mare. Still not right. Plus I really need a t2 rotator for the camera. Probably not going to be able to get one before Christmas so I'll have to make do for now. Is 20/30um that much better than 40um? I'll try the 20 and 30 out. The now longer focal length of the camera lens cuts the wavelength range down considerably. Maybe I should go back to a shorter focal length lens... Oh well, making some progress, at least Louise

T2 extensions came today! I seem to be able to get in focus with a 5mm T2 though a 10mm one might give me more range - focus is focus, of course. Have also now put the proper Thorlabs mirrors in place of the craft ones. I now have a CPL (2700K, 20/75W) and table lamp for testing with . So here's a first go with it. Can indeed see some features - yay! But I'm not getting all in focus. Neither am I able to see the whole of the spectrum in a single frame. I'm still only using my diy reflection grating and maybe it will be better with the proper blazed reflection grating although the grating dimensions will be the same. Anyway, this is an image obtained at full resolution using a 40um slit: Looking at the image, I'm not convinced I'll be able to get the whole of the above section of spectrum in focus at once. On the other hand, my first go seems to compare reasonably well with one I found online: Perhaps some focus tweaks needed and I'll see how it goes with the Thorlabs grating. I'd put off installing it because I appreciate how delicate they are and I didn't want to handle it, especially not whilst I'm still fiddling around. I'll have to readjust the guide cam, having put the proper mirror in place. Will do that now Louise

Hi It was this one which is now 'unavailable'? Similar ones are linked to it. I've no idea how many (Chinese) Lumens it really is. As I said, I got it cheap (£142) - not sure I'd pay the full list price for it. It's quite big and heavy and either needs something tall to place it on else a ceiling attachment. Also, I don't know what it's power consumption is. Louise

Oh ok - you can tell I'm a spectrometer noob ha ha. Learning all the time. Once I get the T2 extenders I should be ok to put everything together properly. Hopefully... Thanks Louise

Hi Ken You'll be pleased to know that I ordered some cfl bulbs and a table lamp off Ebay today . Have also been fiddling with the camera focus today. If you remember, I'd said it was 100mm fl before. Turns out I was being a numpty. I don't know where I got the 100mm from. I checked it again today and found it was actually 125mm, and must have been one of the lenses from the 6x30 finders. D'uh. Obviously my camera was not focusable... I found by checking it that the quoted focal length appears to be measured from the front of the lens. I've still had to order some extra T2 extension tubes. I changed around the extension tubes I have and can almost get it to focus but really need another 5mm, or possibly even 10mm to give a range. Now this was with no slit - just using a mirror in place of the grating and focusing on a distant object, and with no collimator lens i.e. basic camera mode. If I then just put the collimator in, I get nothing but I think that's because it expects a virtual image from a slit? I've assumed the collimator converges the light from the slit + mirror so that it's rays are parallel i.e. appear to come from infinity. With the slit and my diy grating I can still get a sort of spectrum, as before. So am I right that if the camera is itself focussed on infinity / a distant object, then that should be good for the spectrometer? I saw Rockmover's video where he used a finder but I'm still not sure how to adjust the collimator - any help / suggestions on that gratefully received! Cheers Louise

Great for EQ goto mounts but how can you do that with no DEC motor?

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

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

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

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

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

Here's one of the Streetlight images from earlier. They are yellow but I don't think they are sodium since viewing them through a SA100 shows a rainbow spectrum though mostly yellow and red. (reminder: it's a non-blazed 500l/mm holographic transmission grating taped to a mirror ). Taken through a closed window, with blinding floodlights and under the Moon! You can see a spectrum by this means but can't expect it to be clear and sharp! When the floodlights opposite go out (usually around 10:00 - 10:30pm) I'll try again. Louise ps Above was done using the widest slit - 700um, as that was easy to see! I couldn't see a slit at all when one of the small ones was selected.

Picked up some street lamps via the guide cam - quite bright and fairly well focused! Also got something spectroscopic-looking via the Atik too . A bit blurry but that's not surprising. I'm not sure how well focused the Atik and collimator are. I'll obviously have to try using the proper grating. I'll post some pics of what I did get later. Louise

Oh well, I've got it in as best I can... Of course, it's in the opposite position to what it's supposed to be, tut! (the 20um slit is numbered 150 ha ha) but I've had enough of it now so it can stay like that! I'll give it a try out when I can. Louise