new questions on referrence star and instrument response

[Firefly]

Hi, dear Francois:
Recently I have been playing with my LHIRES3 2400 for some time, so in practice I find some new questions that I can not understand well,I'd like ask your help again.
I ONLY HAVE LHIRES3, NOT LISA.

1. what kind of star is suitable to be selected as a reference star for different targets?

Type AV.

Is AV universal for all different targets from O--M? Every spectral type has 0--9; luminosity class has I--V. Then if: my target is F8III, can I select A0V as ref. star? or A8III, F0V? Must both type and class of ref. star match that of target? What is the allowable difference? AND if both type & class match with target, but they have large magnitude difference, i.e. target=6; ref.=3, then can I take it as a ref. star? I want to know besides spectral type and luminosity class, if magnitude will affect the selection of a ref. star???

2.I begin to understand that it is best to find a reference star that is located at the same Alt as that of the target. Then if it has large effect on the result that 2 reference stars at the same Alt, but they are at east and west meridian, respectively.

Depends of the atmosphere homogeneity. In practice target and ref are in the same zone, so no problem

Please look at the picture I attached. Sometimes although Dec+/-5 degree is matched for selecting a ref. star, but the ref. star does not sit near target on RA, on the other hand, I have to find a suitable ref.star far away on the left or right of target on RA. direction. What is the limitation on RA.?

3. ....Reference stars are bright enough that you acquire a spectrum un 10 minutes of less.

If a ref. star is fainter, I have to acquire its spectrum for 20 or 30 minutes??? Could you tell me some experience, i.e.: usually
magnitude 4-----acquire time=?
magnitude 5-----acquire time=?
so on.....


Best regards

Dong .Li

[Olivier Thizy]

Dong,


With Lhires III high resolution, one reference per night is enough and you can select Altair in the summer and Regulus in the winter for exemple. In low resolution, a reference closer to each of your target is better. We have inserted in the LISA Pack user manual a list of reference star sorted by Right Ascension and Declination for this purpose.

This manual is available here: http://www.shelyak.com/dossier.php?id_dossier=40&lang=2



Cordialement,
Olivier Thizy
Vous ne verrez plus des étoiles comme avant !
http://www.shelyak.com/en/

[Firefly]

Mr. Thizy:

Thank you very much gor the information. I am to study it carefully, and if I encounter new questions, I will ask for your more advice.

Dong Li