eShel calibration set-up

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James Foster
Posts: 454
Joined: Sun Jan 24, 2016 7:14 am

Re: eShel calibration set-up

Post by James Foster »

Its almost 9 months latter and I've made much progress on getting my eShel functional.
The problem noted in the beginning:"...I should proceed further seeing that the right-side of the frame has such badly trailed Th-Ar light on these orders."

I determined that the eshel's fiber optic collimator on the unit itself was "lose" so I tightened its 4-bolts and all the system's small hexbolts around the spectroscope and my ThAr order lines got much better; the ThAr light on the right hand side were still worse than the left-hand side.

As Joan mentioned in another post, my Vega specto in LA was 240 sec, much too long! This was due to the fact that my fiber light output in the FIGU wasn't aligned with the light cone. I aligned this "fiber-shadow" with the light cone and got a usable Vega spectrum down to 2-sec with the CDK17!

After much adjustment, I got (more of less) the 3 ThAr spots to align as seen in check3 below:

Image

I was able to get orders from 28-58 without any ThAr\zone errors. I took the following spectra of the image response star alpha Del and variable stars R Aqr and WR140 with the CDK17:
Image

Image

Image
These spectra seem radiometrically correct, with typical errors of 0.1-0.3A around Ha and 0.6-1.4A around Hb and bluewards.
The resolution btw orders 28-58 vary btw R 9.5k-10.5k. My usable spectro range seems to be 3850-7995A. While the check3 isn't as good as what I achieved in LA, I think I can proceed with science on this.

Before I place the eShel2 into the "wine-cooler" and arrange the fiber optic agitators, I will do a more exhaustive test on the camera and (x-y)shifts to see if I can get better check3 results, but looks like there is "light at the end of this tunnel."

James
Last edited by James Foster on Fri Aug 22, 2025 9:35 am, edited 1 time in total.
James Foster
eShel2-Zwo ASI2600MM Pro
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope
LISA IR/Visual Spectroscope (IR Configured)
Alpy 200/600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
Joan Guarro Flo
Posts: 697
Joined: Thu Nov 03, 2011 8:50 pm

Re: eShel calibration set-up

Post by Joan Guarro Flo »

Hi James,

Something hasn't worked, but your writing doesn't show the images, please could you try to mend it.

Many thanks, Joan.
James Foster
Posts: 454
Joined: Sun Jan 24, 2016 7:14 am

Re: eShel calibration set-up

Post by James Foster »

To: Joan,

See end of posts on previous page, esp Robin's:
"...I have seen this kind of problem before. I think it is a browser security setting that prevents displaying images hosted elsewhere on a non secure (ie not https) site. For example this is the address of one of the images
http://astroimage.info/files/Vega_thor_bin-2.jpg
Can you see the image if you click on this? If so try right clicking where the blank space where the image is and go to the image address direct

Cheers
Robin
LHIRES III #29 ATIK314 ALPY 600/200 ATIK428 Star Analyser 100/200 C11 EQ6
http://www.threehillsobservatory.co.uk"

Unfortunately, I have no where else to post these but my webhost service provider, so these are not "https:" but "http:" Here are direct links(your security settings may still prevent display, however):
http://astroimage.info/files/3-alignmentPTS21Aug25A.jpg
http://astroimage.info/files/alphadelph ... Foster.png
http://astroimage.info/files/raqr_20250 ... Foster.png
http://astroimage.info/files/wr140_2025 ... Foster.png

James
James Foster
eShel2-Zwo ASI2600MM Pro
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope
LISA IR/Visual Spectroscope (IR Configured)
Alpy 200/600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
Joan Guarro Flo
Posts: 697
Joined: Thu Nov 03, 2011 8:50 pm

Re: eShel calibration set-up

Post by Joan Guarro Flo »

Hello James,

Without any doubt, that is a great step, so you can observe a lot of targets with very high resolution now.

In this way, I would say to you some little suggestions about your eShel; if I were you, I would try to improve the three points centered as your Check2 image shows. You can gain more precision if they were well centered.

Also, you can notice that in the violet region of your R Aqr graphics, the signal is mixed with noise until more than 4500 Angs, - please, see François' observations of this star -, mend it only requires more integration time, fortunately, the ASI2600MM permits 1800 sec. exposures. Noise + Resolution = Noise.

One thing that strikes me is that your echelle can arrive at the 9000 Angstroms, sometimes it is very useful, as you can see in my X Per observation. The question is, could you defocus a bit the central orders in the aim of gaining range on the infrared region? Minimum until Calcium Triplet; of course, you lose a bit of R, but you could gain in detection range...

I hope that you enjoy this extraordinary device.

Cheers, Joan.
James Foster
Posts: 454
Joined: Sun Jan 24, 2016 7:14 am

Re: eShel calibration set-up

Post by James Foster »

To: Joan

Thanks for your useful feedback all these years! Yes, I'm not at "prime" exposure due to keeping the eshel out of the
"wine-cooler." The coolest I can go is -5 on the ASI2600mm with a fan running close by, because my garage is almost 27C now.

I do not want to place the eshel in the cooler until its fully optimized, but I though I'd share my preliminary results.

I manually construct def_order.lst and def_ypos.lst files everytime I change rot/shift on the colliminator.

I agree, if I get check3 perfectly aligned, I'll get more resolution and better radiometic accuracy from short end to long end of my spectrum. In my old 2022 LA set-up (with almost perfect check3) my resolution was 9.9K to 12k so I've definitely try more 135mm canon lens collminator shifts/rotations to get there. I'm pretty sure I can get to order 60, but anything above order 28 is very hard because almost no Th-Ar points show.

James
James Foster
eShel2-Zwo ASI2600MM Pro
Lhires III (2400/1800/600 ln/mm Grat) Spectroscope
LISA IR/Visual Spectroscope (IR Configured)
Alpy 200/600 with Guide/Calibration modules and Photometric slit
Star Analyzer 200
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