[Magnus Larsson]

Hi again again 🙂

Just for fun, I compared my N Vul spectrum to your, Robin. It was not a good match. Then I remade the processing with another flat, with more signal in the blue. And now, lo and behold, I think it is a qulte nice match. See the attached. The lower green is my previous version, the nice one is yours and the more noisy is my new one.

Might we call that progress?

Magnus

Attachments:

1. 

   n_vul_2024_ccomparison.png
   

[Magnus Larsson]

Hi again!

Robin, regarding the binning and skyglow: I’ve been a bit worried about the width of the bin I am using. I see you set a bin on your image there that I would call quite generous. I was afraid that if I allow too much of the skyglow in, so to speak, it would possibly taint the result. On the other hand, I risk losing some photons… With inspiration from the screenshot you share here, maybe I should not worry so much about a too wide bin zone, trusting that ISIS can handle it? And actually, in the resulting images I get, the sky is fairly black within the sky zones…

Magnus

[Magnus Larsson]

Hi!

Thanks, Robin, that is a very good idea.

I’ve been experimenting as much as I can, trying to make sense of this. Last night, I captured spectra of 4 stars w Miles spectra – I found them via ReferenceStarFinder and checked in the Paolo Berardi excel-file and in VSX. It looks like it is a bit hard to find a good ref-star close to SS Cyg – or …? 🙂 Stars are:
HD169027: this was the only one of the 4 that was NOT in VSX, not identified as variable. It is in Dra, and a little bit of distance from SS Cyg – however, at similar altitude last night when I captured them.
HD198478: Blue giant, slightly variable
HD199878: similar, blue giant, slightly variable
HD207330: spectroscopic binary.
The last three are close in Cygnus.

I then tried producing response profiles from all and cross-process them. I did the whole process both with bin 1×1 (raw) files and no flat, and with the CMED process, so they are bin 2×2 and there is a flat involved. Interestingly, these two ways produce somewhat different results.

Attached are two comparisons betwen the 4 reference profiles, one with profiles produced in bin1x1-noflat-mode, the other in bin2x2-withflat-mode. Interestingly, there is significantly more difference between them in the bin2x2-withflat-mode! Moreover, in both, HD169027 stands out. Possibly the distance leads to different profile….?

Processing the stars: I can get good alignment between the two giants – see attached screenshot. Again, clearly better in bin1x1-noflat mode.

So, how can I make sense of this? Is it my flat with very weak signal in the blue (I use a halogen lamp) that plays games with me? Am I doing something wrong? I must admit that this is quite frustrating…. Any ideas very welcome. And I’d be happy to share any of these files….

Magnus

• This reply was modified 15 hours, 59 minutes ago by Magnus Larsson.

Attachments:

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   response_compare_2.png
   

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   response_compare_3_bin1_noflat.png
   

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   HD199478_w_response_HD198478_bin1_noflat.png
   

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   HD199478_w_response_HD198478.png
   

[Magnus Larsson]

Thanks, Gary!

Well, I did not handle the companion 🙁 But checking it in Phoranso, that I use for measurement, it is clearly outside of the aperture. So should not be confounding the measurement.

I can not go deeper from my back yard, but if it is of interest, I could try capture a series with our remote telescope in Spain..?

Magnus

[Magnus Larsson]

Hi again!

Looking more into this now in daylight. Robin, how do you determine that HD207673 is reddened`? By comparing with an artificial Pickles spectrum? Or with Paolo Berardi’s spreadsheet and functions?

And: how would I find good ref stars to check and validate my process? And for taking good spectra moving forward – let’s say SS Cyg: I found HD207673 through the ReferenceStarFinder_V3 excel file. As I understand it, I would need to check the ref stars more thoroughly. But how? Any advice is warmly welcome.

Magnus

[Magnus Larsson]

Hi!

Yes, same air mass. They were identified as ref stars for SS Cyg, or rather HD207673 was and the others as supplement stars for checking precisely the instrumental response. They were observed at roughly the same air mass.

Very helpful indeed, with your analysis. May I ask: how do you determine the extinction and reddening? Very good to know.

Also: I came upon another hypothesis tonight: My profiles might be tainted by skyglow. I tend to take the ref star first, and in the bright summer nights here in Sweden, the sky is not fully dark (I have relied on ISIS being capable of handling that….). So it might be that the different profiles are captured at times when the skyglow was significantly different. I need to check this more. If it makes sense.

Magnus

[Magnus Larsson]

Hi Robin!

Yes, I am doing the Response and Continuum processes in ISIS. Exactly.

Best,

Magnus

[Magnus Larsson]

Hi!

Here’s another sequence from last night, from Malmö, Sweden. It was fainter than I expected (thus lower SNR).

Observations uploaded to databases (in a few minutes).

Magnus

Attachments:

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   UV_Per.png
   

[Magnus Larsson]

Hi!

So I managed to capture some 180 60 sec exposures with a clear filter on our CDK17 in southern Spain. The series shows bumps that looks lite superhumps to me, see the attached screenshot from Peranso. The measured period is 0.072982 days or 1.751 hours. THe amplitude is about 0.165 mag.

Magnus

Attachments:

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   AT2024lwu_20240702.png
   

[Magnus Larsson]

Hi!

I managed to take a short time series last night, unfortunately interrupted by clouds. Uploaded the observations with the name TCP J20023703+3947002, which is what VSX gives for this object.

The observations shows the beginning of something that *could* be a superhump. But far from sure. I’ll return to it the next few nights.

Attached is a screenshot of the lightcurve from Peranso.

Magnus

Attachments:

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   AT2024lwu.png
   

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