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I'm posting this Be star's H-Alpha spectrum to show results after I had an issue with my LhresIII.
I noticed my BD Cam data h-alpha spectra's main absorption line was deviating from the laboratory reference of 6562.85A as time went by btw January and March 2018. Weather was bad (even light clouds, 2-3 magnitude limit) So I planned to swap the LhiresIII for the LISA and take my time to see what was wrong with it. When I placed
it on my desk and started to check the "tightness" of the bolts I found some that were fairly loose. As well as these I had to tighten the robofocus support bracket
that held the stepper motor that connects to the micrometer; see http://spectro-aras.com/forum/viewtopic.php?f=8&t=1932.

After tightening every blot on the LhiresIII I could I took it back out and got this spectrum (best 8 out of 13 X 300sec exposures):



Conditions were very badon the night I took these spectra, but I wanted to see if my work made a difference and it seems like all the Ha/H2O line corresponds
perfectly with the Be star's absorption.

I knew my BD Cam spetra were off when I compared the 1st and last calibration frames (before and after spectra exposure) and they where displaced 2-3 more on 28Feb18 than the 1st and last line calibration (neon) for 05Feb18. I'll post an animation of these displacements latter if desired.

James

Here is another spectra of a reference star I use alot these days (HD085235):

Processed in Is 1.92 and instrument response corrected. No velocity correction was made and the objects was imaged just before hitting the meridian.
H-alpha and the H2O line are lining up where expected.


James

Hi James

Yes the stability of the LHIRES is well known for not being the best. Other places to check are that the clamping screws on the collimator are tight and the spring on the grating holder has plenty of tension.

A good test for any spectrograph is to point it NSEW Zenith taking lamp spectra at each orientation

Cheers
Robin

To: Robin,

Thanks for the constructive feedback!
Here is a comparison of my BD Cam 05Feb18 and 28Feb18:

It should be noted that i took the LhiresIII off the scope btw these times and that probably exacerbated the "loosening" of the
LhiresIII bolts. I knew something was wrong when i compared the Ne calibration lines (before & after) on these dates with one another; see:
BD Cam-05Feb18
http://www.astroimage.info/spectra/05Feb18.mp4
BD Cam-28Feb18
http://www.astroimage.info/spectra/28Feb18.mp4
The displacement of the H-Alpha region's Ne lines are clearly much larger on the 28Feb18 date (comparing the 1st Ne calib with the last Ne calib).

Finally, here is the BD Cam I did last night on 07Mar18, which shows much closer coherence btw the H-Alpha absorption with the H-Alpha laboratory line:


James

Here's a follow-up spectra of 5 Cnc taken on 18Mar18 btw SoCal storms:

I went longer on each sub-image (7min vs 5 min), removed some H2O and did a low pass Gaussian. The left-hand peak of
Ha emission looks a little more prominent to the right-hand peak as seen from the earlier (06Mar18) spectrum.

James