SteveBz

It may well be a hierarchical binary with one or both of the stars having a dimmer or closer companion. Just to be clear, 6 & 7 Lyr are the stars that I'm speculating are close enough to be a binary pair. It may be that 6 Lyr also has a further close companion a few AU from it that don't appear in Gaia and that is what is showing in the 6Lyr spectrum. Gaia DR2 policy at the time was anyway not to provide radial velocities for spectroscopic binaries because the velocities would be unreliable, ie +/- the orbital velocity around the other star. So this may be why I can't find one for it. Regarding the spectrum you directed me to: Is that not just noise? Or is that some sort of complex metalicity? Kind regards Steve.

That's sad to hear. In fact I'm doing a project with a researcher from a Mexican university on the orbits of binary stars. As an amateur astronomer, I wanted to see if I could follow up any of it with my scope. Actually, I find the shots of the binary stars through an amateur scope are every bit as aesthetically attractive as the professional ones in Aladin etc, although distant stars are more visible and more point-like in the professional ones. I don't think I can hold a torch to the professional spectra though. I do have a 3d printer, which I'm about to dust off, but it maybe easier to go down the Alpy route. I'm just having difficulty justifying the extra costs involved 😅 Thanks for your comments. Kind regards Steve.

Yes, that's what I though it was.

This is also a good point. However, it seems likely to me that they are indeed a bound pair. On the positive side they are at about the same distance with a parallax of about 20 mas or about 50 pc. They also have similar proper motions in the place of the sky of about 32 mas/yr. Sadly the Gaia DR3 radial velocities have not yet been published and they don't have a DR2 radial velocity (actually, I think they're both on Hipparcos at about -25 km/s). Here are the details: Lyr 7: magnitude 5.6, Px 20.66, PM 33.5 Lyr 6: magnitude 4.3, Px 20.64, PM 32.2 As I'm sure you've seen, you can find these details easily on the Aladin website at: Aladin Lite (u-strasbg.fr) Where did you get this from? As I don't imagine it was my spectrum 😢 I'm going to run longer exposures next time to see if I can get the companion star's spectrum more clearly.

Hi Robin, This is very nice. It seems to have the classification. Does Vizier also have the actual spectra? Kind regards Steve.

So this is the second, dimmer star, 7 Lyr using the same response calibration as before. I've tried to show it on the same chart as the previous star (6 Lyr). I've scaled as per Merlin66's suggestion for 370-750, but I think I'll go with nm - in case I want to get published 😄: The stars themselves don't look so different, but the spectrum for 7 Lyr is very much dimmer than 6 Lyr as you can see. I think the spectra are probably not high enough quality to make any determination about how similar the stars were or were not. Do you think I should have (or could have) taken a second longer exposer to make 7 Lyr more readable and let 6 Lyr saturate? Maybe I'll try next clear night. What do you think? Kind regards Steve.

I did, and it was sort of close but not perfect.

So do you still do this each night for each target, or set of targets? And manually draw the response correction line?

My issue, really, is that it's very manual and, for me at least, very error-prone. I was wondering how I could use the effect of averages to reduce the error.

My issue, really, is that it's very manual and, for me at least, very error-prone. I was wondering how I could use the effect of averages to reduce the error.

My issue, really, is that it's very manual and, for me at least, very error-prone. I was wondering how I could use the effect of averages to reduce the error.

Hi Robin, I was just being lazy with my vocabulary. I meant all the stuff (and I hope that is what I did - I followed your instructions to the letter). But I think the answer to your question, is - like building up a dark library - that you need a set of compensating corrections for each physical situation eg one for every 10 degrees of Az, maybe. Steve.

Yes, I did see that and there have even been (quite intemperate) arguments on SGL regarding it. Why do we do that since I haven't even got the A-circle-thingy on my keyboard? It's not as much hassle as the Light-year vs parsec argument, since it's still metric and it just needs an extra x10 or /10, which we can all probably live with 😄 Good point. I tried to do that on the second version. Should I have cropped it further? Finally, do you build lot's of instrument response files over time and then 'stack' them to get a more accurate response curve?

Hi People, That was quite hard and probably a bit wobbly. Here is what I hope is a response curve produced from 2 Lyr applied to the 6 Lyr A (if that's the proper nomenclature - ie the main star of 6 Lyr): I've had to save the response file as a dat file and then loaded it using 'Add/Image', then divided. I'm sure there is an easier way! Kind regards Steve. PS Maybe this is it. There is a chart edit option and you can enter the instrument response file. Looks a bit better, but obviously the same graph.

Well spotted. Sorry about that typo. I'll fix it now.

Why is Eps Lyr, the double-double, so called? I was looking at it the other day and it seems to be an ordinary binary star. I can't see what else there is to 'double'. Even in Stellarium there nothing more to see. Here is a short snap of it: Kind regards, Steve.

Hi People, So here's P Cygni. 15 sec x 40 stacked, tilted and croped. And what I hope is the sensor corrected spectrum: Do I have it the right way round? I feel the little Bresser 114mm and the 178mm mini are working well together. I put a helical focuser on the Bresser for fine focal adjustments really because it was very light. Tx Steve.

I'm trying to produce a spectrum corrected for instrument response. I've followed the instructions and this is what I get. Seems a bit noisy. Do I need to produce lots of correction profiles and stack them? Is it possible to find standard profiles for individual cameras, eg QHY5iii178mm? Kind regards Steve.

So you were right. When I cropped it more tightly some of the peaks disappeared. (That one at about 250 is a little stubborn). The H-alpha line seems very faint, as do the telluric lines. When I look at the unstacked lines, they do indeed look a little intense at the bright points.. Next clear night I'll play some more with the exposure and the focus, and also more tightly cropping the area of interest frame on the sensor to avoid background stars. The image is about 1 degree away from horizontal. Should I fiddle or leave it?

OK, thanks for that, I wondered what they were.

So it was quite clear tonight until about 11pm. In fact just as I was about to try P Cygni, as you suggested. Then it clouded over. But I did get another go at 2Lyr, which came up 2 hours earlier. Here's the image, cropped at source and then stacked with Bass (about 20 images of 30 secs each): And here's the spectrum, calibrated. As you can see I've calibrated it to the the H-Beta line and the star (@ 0 nm). Given that messing with the camera is sort of outside my comfort zone at this stage, I'm going to look for a pair of binaries separated E-W, not N-S, so I can use the same technique to take a spectrum of both stars. In spite of all my earlier experiments, this feels like the first real one. Any suggestions welcome, as always. Kind regards Steve.

So 2 test objectives for the next night. P Cygni and plain scope. (I attached the manual for other readers). Tx. StarAnalyser100manual.pdf

No I haven't. Scary thought. I'll have a think about how to test it.

Beautiful spectra. I hope I can emulate them.

I'll try P Cygni on the next clear night.