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Here is my first try at using the LhiresIII with the 2400 m/ln grating on Vega around Halpha (micrometer reading 19,72mm):

I processed these 9x25 sec exposures with the CDK17 telescope of Vega using Isis V 5.90 and used the 23 micron slit, removed the telluric lines and used Vega's ELODIE 3.1 data base spectrum to create a IR file and reprocessed with the IR and removed the tellurics again. I'm not sure if my flat came out correctly.....illumination looks like a side long peanut (result of 10 images with 16sec exposures ea. with ADU of 58.3K each):


Right after finishing this spectra set of Vega, coastal clouds came in...........Will get the locations of Hb, Hy, and CaK when the weather gets better.

James

Perfect James, 16000 in résolution id good.

To: Etienne

Re:"Perfect James, 16000 in résolution id good."

Thanks! After using Isis with the old L-200 spectroscope, using the LhiresIII was a snap!

I tried going to the CaK (near UV) but the internal halogen lamp for flats was too weak to show any illumination above 0.1K adu after 300 sec exposure at 3x3 bin.
I'm working on a high illumination UV/white LET flat field box I can mount over the baffle of my telescope for getting data in the CaK region. For this 3900A region,
the Alpy calibration module had a much brighter lamp for flat fielding; i.e. I could get near 58K adu after 6x10 minute exposures!

James

Hello James,

For normal flats, above > 4500A, it is enough to use the LHires III internal lamp (except some projects that require higher flat accuracy, typically at wider coverage at lower resolution).
For the UV, you will find LEDs have very short FHWM (of like 30-40A ?), producing high gradient flat with suspicious reflections at one side, moving away 150A having just reflections. You would certainly need more type of UV leds. I am still using the "black light", it is giving much wider coverage exactly where needed, just special treatment needed to remove a few emissions from the flat. I will also have to try a higher temperature halogen lamp, though having doubts due to internal reflections are always a problem with the LHires.
As for LED as a normal flat, yes I have similar solution, not using since internal flat with the ATIK 428 working well enough.

To test your setup in the UV to see whether you reached an optimal throughput of your setup, I'd have comparison exposures for '7 cep' as a test star, that's what I'm shooting every week (like 1-3 minutes exposure).
At high resolution when you have flat, you don't need high quality IR star like Vega. Of course, you can check it rarely for ripples or flat correctness, but for a longterm in blue end, the placement of a nearby star will be more important than having high SNR. Of course, for the red part (H-alpha) it is much less relevant to have a nearby ref. star than in the UV.
My experience after trying gratings 150/600/2400 with the LHires, it is working at far the best quality with the highest resolution only (2400/mm is my case), hence I'm sticking to it. I'd be also curious how an UV-optimized grating would behave... however, I don't know which grating to try for that.

Cheers,
Peter