Thalestris24

Yeah, I found out late last night, after I'd posted, that the xenon part of the bulbs' description is a bit of a misnomer as it's only used to start things off and the discharge is really from metal halides. Pity, really. Thanks Louise

He he - I'm overthinking it, I know! Still... hid xenon headlights might be good, though not especially cheap. Xenon has so many lines right across the spectrum - maybe too many! Louise

Yeah, I found that now. I've come across some old adverts for some of the blue ones but nothing current, unfortunately

Hi I was wondering what sort of lamp/bulb they used - maybe can still get something similar? I presume they were some sort of fluorescent or other kind of discharge tube/bulb? Thanks Louise ps Ok - I've some references to it. Doesn't sound like anything similar will be easy to find

Hi Ken Sorry, only just picked up your reply. Well, having ordered the starters off Ebay, I'll see what they are like when I get them. I keep meaning to browse the spectroscopy groups... What sort of lamp/bulb is the Habitat one you mention? Did you have spectral data for it? What about using a cfl - I presume they are not good enough for calibration? Not sure what you mean by "ProAm requests" but any spectra I may acquire are not likely to go further than the spectroscopy forum on here and then only if I think they're good enough (which they probably won't be!). For me, it's all about the journey! Louise

Hi Ken Well I have some basic neon bulbs but they are only good for the red end of the spectrum. I did some research and found postings about using a glow starter like you mention. TBH I'd never heard of them before! Of course, I know about fluorescent tube starters - but 'glow starters', um, no! The original RELCO ones that people mention don't seem to be available any longer. There are other makes of 'glow starters'. They are very cheap so I ordered a pack. Will have to wait and see if they operate the same as the RELCO one. Fingers crossed! I'd thought about a high pressure sodium bulb. You can get clear SON bulbs quite cheap but they run at around 90V and I think they need a ballast to operate. Still might be a possible if the glow starters are a, er, non-starter! I also thought about laser pens but I gather their nominal wavelengths are +/- 100A but could possibly be themselves calibrated against a cfl. One can go round and round in circles when it comes to calibrating anything... Louise

If you're interested the Lowspec 3d files are here with the assembly guide pdf at the bottom of the file list. My old eyes find it hard to judge focus - I must see if I can get my cataracts done. I'll ask my GP to refer me but I expect waiting times are long. I was thinking about incorporating a calibration light source(s) - worth it? I'm always complaining about the cold here this time of the year - there was a hard frost this morning. It never gets very hot in the summer - mid to high 20's at best, on a few days of the summer. I couldn't cope with Oz high temperatures! Thanks Louise

Hi Ken Hope you're keeping cool down there! The temperatures in some parts are dreadful! 😮 Yeah, the micrometer only extends out to 13mm. Also, looking down, the collimated incident beam comes in from the right. Diagrams always show it coming in from the left of the normal. The camera isn't rotatable at the moment as it's supported, and sits on, a flat aluminium bar. The Atik 383l+ is quite heavy.... I might have to try and rearrange things or sort out a different way to support it. Yeah, focusing is difficult and varies a lot. Certainly varies with wavelength - maybe also a positional effect? Yep, will try out BASS next! Thanks Louise

Hi Jim Oh dear, sorry about that - things always go wrong when you need them, don't they. Hope you can get up and running again soon! Yeah, Ken has indeed been brilliant! I really appreciate his help, support - and patience! Eric has been very helpful too. Also all the other guys on here who helped me get to grips with 3d printing. Well, at least the Surplus Shed lenses are cheap! Hopefully they will have the type, diameter and focal length you need. Just take your time checking everything matches before you order. I think I used their lens finder. They are quite helpful if you need to ask anything. I didn't quite appreciate how closely the diameters and focal lengths need to match the design. My 121 mm focal length collimating lens seems to be ok but there isn't much room to play with the 125 mm design. Diameters can't be too big either otherwise the two main lenses will crash together! This was a problem I had trying to use the 125 mm finder lens which is 31.2 mm dia - too big! The focal length of the camera lens should match your camera properties. My Atik has a spacing of 20 mm for the sensor - t2 flange distance. So, in the end, a 89 mm focal length proved a comfortable distance to the sensor plane. I've ordered a T2 360 deg rotator. A bit pricey but I think it will be useful. It takes up 5.5mm optical length so fitting it in the camera optical train shouldn't be a problem. Hope you can have a relaxing Christmas Louise

Hi Ken I have done the theory (covered it in physics at uni ) but it's just been the practicalities I've had trouble getting my head around. It hasn't helped that everything is right to left on the screen and need to go anticlockwise from a starting position as well as it being a blazed grating. I think I've got there now - tbh, I wasn't expecting the zero order to be quite so far away from the 1st order spectrum. When you mentioned it would be, a light began to glow in my head! I don't think I can actually get the whole of the recordable spectrum on one screen but can think I can get the major features ok. Anyway, this must definitely be the zero order: Turning anticlockwise, and shifting right, I eventually get to the start of the first spectrum - rightmost faint line (spectral lines shift right): a less bright 0.5s exposure: Then, shifting further right, I get to the end of the first spectrum (broad faint line on the left): After that faint line on the left in the last image, there is nothing else close, as far as I could see. The apparent zero order was at 1.76mm on the micrometer. The start of the spectrum was first just visible on the left at 2.08mm - more than a whole screen away. The start shifted to the right (2nd image) at 4.41mm with the third image on 5.11mm. So the spectrum seems to cover 5.11-1.76 = 3.35mm of the 13mm micrometer i.e. just over a quarter of the total micrometer range. There are fainter spectra in an anticlockwise direction. Of course, I've been used to using the SA100 where you can easily get the zero order plus the whole spectrum on one screen - easy processing! Louise

Ok - will try that! Thanks Louise

It's 11\:30pm on Tuesday here I'm still a bit confused. The clockwise rotation only goes so far. I went as far as possible above then turned the micrometer anti-clockwise until I ncountered a spectrum. I've seen some examples which suggest that a second or third order spectrum can be brighter than the first. I'll keep at it and try and find my way. Thanks Louise

I'm confused - didn't you say previously that the spectrum image only calibrated when flipped? I'll have another quick look at what's visible tomorrow. There may have been an odd line outside of the saved fov. My ecg appt. is Thursday - it's Wednesday tomorrow! Thanks Louise

"A star spectrum will only be a few pixel in height, depending on the size of the star disk at focus. " Of course - silly me! I'm losing my marbles I think in mono, it's hard to tell whether a particular line might be the zero order. I'm not sure how far away from the rest of the spectrum it might be? But if it's the first spectrum encountered from the max clockwise position, then that must be the first order spectrum? According to Thorlabs the blaze angle is about 8-9 deg and I'd estimate that's the angle of incidence at the max clockwise position. Could it be that I should have the grating arrow on top and pointing in the opposite direction to the Lowspec build guide? I need someone with a Lowspec and 600 line grating to concur... (Hurry up, Jim!) I've been using APT for image capture which lets me horizontally flip the image on screen - SharpCap doesn't have that facility. If I then flip the saved image it then matches the screen and is the 'right way round'? I'll resume testing on Friday - have my ecg appt on Thursday. Hope I don't find I need a heart transplant! Thanks Louise

I've had another go this evening. I rotated the grating clockwise as far as it would go. I think I hit the blaze angle as there was no spectrum but just light on the screen. I turned the micrometer anticlockwise from this position until I got to the first spectrum. I got this (flipped) CFL one: Must be the first order? I also did one with the 500mm lens on and of a high pressure sodium lamp about 150m away. This is a screen clip of the guide cam screen (EZPlanetary): Pretty bright, huh? But I had trouble acquiring a spectrum. It's straddling the slit - it's very hard to position targets manually (I have the Lowspec mounted on a Star Adventure / Manfrotto 055. It's my 'bench' for now.). Anyway - this was the best I could get: I don't understand why the height of the spectrum seems to collapse sometimes? There is a HP sodium lamp reference spectrum here Mine seems similar-ish . I found out what causes horizontal black lines - dust across the slit! Unavoidable here... Louise

Yeah, I've used RSpec too - trial period long run out now! It did allow rotation of the whole spectrum to compensate for the SA100 not being horizontal. It won't let me fix the slant of the spectral lines, afaik - I don't think anything will. BASS is very similar, I believe, and basically does the same things as RSpec - but for free! I'm currently not very optimistic about getting any spectra from stars. I estimate that exposures will need to be quite long and my guiding from indoors isn't that good... I will give it a try though. Louise ps where have you got to now?

After struggling with using a lens and guide cam last night I went back to the cfl today. Even though I had a bright source which covered the slit I had trouble acquiring a decent image. Heaven knows how you do it with just a star - a particular star, at that! Just did another of the CFL. I can't seem to do anything about the sloping spectral lines. It seems to be linked to the way the holder sits and I can't see what I could do about that other than maybe reprinting it all. But maybe that wouldn't make any difference. It could be something to do with the spring affecting it - I'm not sure. I've also developed several horizontal black lines... I don't know what would cause them other than the camera sensor which is a bit worrying. Not sure if the slant and, particularly the black lines, will affect the processing?? If so, it could be end of project If it's still ok to process I'll have to get to grips with BASS. Louise

I've calmed down a bit now - just a bit! Had to walk away from it last night. Louise

Hi Jim Yeah, you have to be careful what you order... I got the mirrors from Thorlabs - I only fitted them the other day! I got some round and square 1" craft mirrors of Ebay - very cheap! I used them in place of the proper ones until I was ready. The Thorlabs ones are a little expensive for what they are but not that much in absolute terms - plus they fit perfectly. I've got so far but am struggling a bit with the finer points. I don't think mine will be stable enough for astro-spectrometry. Getting and maintaining focus is proving very difficult. I'm sometimes getting some odd results but don't understand why. Here's one I just did of the CFL bulb: I think that's the zeroth order on the left and I've flipped it so it should fit Ken's calibration ok. It's all on a slant - not sure why. The spectral lines are slanted too - presumably to do with the seating of the grating. I've tried to adjust it but to no avail. I'm getting old and tired and impatient! I'm losing my grip - keep dropping things, and my cataracts make it hard to see what I'm doing! My back's been killing me too. I think 2020 will be my last year of doing astro things . Louise

I got mine from Surplus Shed too - they are fine! I wasn't going to pay Thorlabs prices! Louise

I feel like I'm working in the dark - metaphorically speaking. For some reason my spectrum height seems to have suddenly collapsed to only about 10 or 20 pixels high... No idea why that is... It is getting very frustrating! Thanks Louise

Yes, I did say it could be 'the wrong way around' - it's just as it comes out of SharpCap so could be flipped. I'm waiting for a T2 360 rotator so that I can adjust the camera easily. So, my image 'd' is correct but flipped? Thanks Louise

Hi Ken I can't see anything as big as the numbers in the guide cam - the fov is very small, can only see just either side of the slit. I've lined up the slit in the guide cam so it runs diagonally. I've not been able to see anything I could identify as a zero order - just what is in the sequence above. Could it be the design doesn't allow for it? I'll have another look when I can. Louise ps I just watched the grating whilst I turned the micrometer anti-clockwise and noticed that it may be that the grating isn't going back far enough because the spring is a little big and stops pulling the grating back

No worries - this is an oldish thread now Louise

Yeah, I was thinking it must be to do with the grating itself. I've tried reseating it and held it tight to the holder whilst tightening the grub screws. Will see if that helps - fingers crossed! Cheers Louise