spectro-aras.com

James, Thanks for that....
I was thinking from you comments it was a change of processing software which caused the"suspect" rather than the lack of data..

I've looked at raw image (VV CepCaH-001.fit) James has just sent me, it has a signal level of only 400 ADU (at 330-360 ADU bias not removed), bin2x2.
That means it has almost no signal.
My similar chip (smaller version) reaches ADU of 2000 good times (1000 bad times) in the raw (incl. bias) per 10-minute exposure.
Spectrum FHWM is similar.

In principle, with this camera @ 2x2 bin I always try to avoid getting too far below 2000 ADU - then the final sum will always be poor. (Especially true when targeting absorptions.)

This must be the mentioned easy guiding fault (most certainly taken up the bright star's ghost image), worth to test different positions with getting rid of the ghost image (either shorten exposure, or reduce search area).
It is enough to mistake 1 pixel of 8.3 micron to have a similar problem (own experience).

Peter

To: Peter,

As I mentioned in our email thanks!
I will await my new LihresIII that I ordered today, before taking these comparisons up again in CaK.

The L-200 will go into semi-retirement for awhile as I "train" on the LihesIII and process my
LISA spectra taken over the last couple of weeks.

Hope to start-up the CaK observations by the end of July....besides VV Cep I have numerous solar
analogs I need to shoot in the Cak and Hy regions. After this week i will be going to my high altitude site
from 20-29Jul17 for LISA, photometry and "pretty picture" imaging. By the time I get back, I should have
the new LihesIII with the 1800 l/mm grating to start afresh. Thanks again for the support!

James

p.s. Yes I would like to make flats in this region that is non-parasitic....I have some bright White/UV LEDs
I may wire-up and make a light box to test on.

Hi Peter, James

I have also just started covering VV Cep in this region using the LHIRES and 1200l/mm grating. What reference star are you using? (I used Vega last night but I have not yet found a reliable high resolution reference spectrum for Vega covering this far down in wavelength)

Cheers
Robin

Hello Robin,

Welcome on the experimental board
I've been only using low resolution ref.star: always a 7 cep before+after (averaging), + low order spline fit ("Automatic 1" in ISIS, after removing wide CaII regions manually, which are quite shifted and wide..).
Though, used to shoot Vega too (= easy to focus on - why not take 1-2 spectra?) but couldn't find any reliable hires spectra to fix any ripples (would be also too messy around wide CaII and Balmer absoprions - those high gradients won't do any good, and this area is changeable...).

I've been rather trying to fix any med/hires ripples by flat, not by ref.star (the ATIK 414 was smooth here, the ATIK 428 is the critical - homebuilt "BLB" flat was really necessary).

Cheers,
Peter

Thanks Peter,

I just checked back to see what I used for AZ Cas in 2012/13. (A similar system but much fainter)
http://www.threehillsobservatory.co.uk/ ... tra_43.htm
I used Altair and Castor and the UVES spectra as reference then. It seemed to work ok though the air mass match would not always have been very good, but perhaps it does not matter too much over the limited wavelength range.

Cheers
Robin

RE:"What reference star are you using?"

I used Miles star HD164136 because it was high at +30 declination and bright (MAGv: 4.4). There are numerous stars closer to VV Cep than this star, at better declination (+66),
but their dimness would make exposures in the CaK region prohibitively long.

James

Hi James,

I find MILES stars are not ideal for high resolution work though as the resolution difference makes the division tricky and you can potentially lose subtle features in the response in the smoothing/filtering needed. There must be some good high resolution spectrophotometric quality data for Vega somewhere. Otherwise I will probably stick with my usual Altair/Castor/Regulus high resolution UVES spectra standard spectra which I can record without taking up too much observing time.

Cheers
Robin

Robin this any good? Andrew
https://academic.oup.com/pasj/article/5 ... m-Atlas-of#

Files here http://pasj.asj.or.jp/v59/n1/590122/590122-frame.html

Regards Andrew

Thanks Andrew. That certainly qualifies as high resolution At first glance though I think they may have been rectified.
There are spectra of Vega in ELODIE 3.1 but comparing with the CALSPEC spectrum of Vega for example shows that the continuum is unreliable below ~4000A
(Perhaps it might be possible correct the ELODIE 3.1 Vega continuum using the CALSPEC spectrum)

Cheers
Robin