eShel optim. + ASI6200MM CMOS camera

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James Foster
Posts: 439
Joined: Sun Jan 24, 2016 7:14 am

Re: eShel optim. + ASI6200MM CMOS camera

Post by James Foster »

To: Christian,

Excellent advice on the CDK telescope and thanks for clarifying the optical plug type!

James
James Foster
eShel2-Zwo ASI6200MM 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
Peter Velez
Posts: 146
Joined: Tue May 12, 2020 7:36 am

Re: eShel optim. + ASI6200MM CMOS camera

Post by Peter Velez »

Christian

thanks for the very detailed and instructive paper. I confess to reading it several times now. I had been considering the eShel and you have given me so much food for thought that I have indigestion.

You discuss 2 issues which has some relevance to my current set up with the LISA - telescope optics and CCD sensitivity. It would be great to have some feedback on these:

1. Optics - you discuss the challenges arising from using a telescope with correctors/reducers etc. I am presently using a Planewave CDK 12.5. As this is a native f/8, I am using the PW 0.66 reducer to step it down. I have the necessary adapters to remove the reducer but it will impact on my ability to image fainter targets. I'm also unsure whether the Atik 460EX is large enough to capture the full spectrum. Recognising that the LISA has issues above 4000 A anyway, would removing the reducer make that much of a difference?

2. CCD response - I have managed to track down the replacement window from Thorlabs (thanks James!) which will assist in transmission of shorter wavelengths. Do you see this making a material improvement in responsiveness? I see that for the 460EX the step down in QE from 4000 A to 3800 A is huge - 20% from 59% to 39%.

James,

you have replaced the window in the Atik 414 for your Alpy. Did you see a significant improvement in performance?

A final point Christian - I love your integration of domestic hardware in your set up. The wine fridge is a great idea - but using a couple of fans as a fibre optic scrambler is priceless!

Pete
Christian Buil
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Joined: Mon Sep 26, 2011 6:59 pm
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Re: eShel optim. + ASI6200MM CMOS camera

Post by Christian Buil »

Peter,

Using the LISA spectrograph becomes problematic at 3900 A because of the internal chromatism and difficult at 3800 A (chromatisme + internal absortoion). The relative impact of your focal reducer is probably quite low.

My recommendation is that you form an opinion by yourself. The idea is to observe the same star (and the same night) at the zenith (to eliminate atmospheric refraction) by making one spectrum with the reducer and another without the reducer, then calculate the ratio of the two. I's also the occasion to measure the impact of seeing vs. the slit width adopted for the two focal lengths for the telescope.

Here is the optical transmission of an Atik window and for a silica window (Chinese origin, not absolutely sure about characteristics). The gain is zero at 4000 A and low at 3900 A :

Image

Image

This work on ultraviolet was carried out mainly in the context of the UVEX development, which can observe down to 3300-3400 A, then the eShel(2). It's very specific. Do not panic with spectrographs like Alpy or LISA the gains are quite low, you can see it.

Christian
Peter Velez
Posts: 146
Joined: Tue May 12, 2020 7:36 am

Re: eShel optim. + ASI6200MM CMOS camera

Post by Peter Velez »

Thanks Christian

this is precisely what I was looking for.

In a perfect world, I'd test the system with and without the reducer - however, its a 6 hour drive to the observatory which is an interesting proposition at the moment. Its also a challenge to work at night at the observatory as there are about 15 other scopes running at the same time and quite easy to ruin someone else's work with any stray light.

I had a suspicion that changing the window would not make a huge difference. If I make the leap to the UVEX (or win the lottery and change to an eShell(2)) then it may be worth the investment.

Pete
James Foster
Posts: 439
Joined: Sun Jan 24, 2016 7:14 am

Re: eShel optim. + ASI6200MM CMOS camera

Post by James Foster »

To: Pete,

RE:"James,

you have replaced the window in the Atik 414 for your Alpy. Did you see a significant improvement in performance?"

I posted the specifications for the glass here: http://spectro-aras.com/forum/viewtopic.php?f=45&t=2461

Its hard to tell the difference, though with the Atik460 and Alpy600 I usually only get to about 3750A limit. With the Atik414 and the new glass cover,
I can get to almost 3560 before the continuum breaks down. The limit is mostly because due to the Alpy600 grism design.....UVEX is a much more
elegant solution....although I might not be trying it til next year as I'm putting together a eShel system per Christian's great optimizations!


James
James Foster
eShel2-Zwo ASI6200MM 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
James Foster
Posts: 439
Joined: Sun Jan 24, 2016 7:14 am

Re: eShel optim. + ASI6200MM CMOS camera

Post by James Foster »

I wonder if this would be a good sensor for the eShel:
https://optcorp.com/products/atik-16200 ... gKHyfD_BwE
I think I can buy this for considerably less that the ASI6200MM Cmos.

James
James Foster
eShel2-Zwo ASI6200MM 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
Tom Love
Posts: 64
Joined: Sun Apr 21, 2019 5:57 am

Re: eShel optim. + ASI6200MM CMOS camera

Post by Tom Love »

James, it looks as if OPT sell the ASI 6200MM for only $250 more than the Atik.

Also, I have recently discovered that you can buy direct from ZWO more cheaply than from some of the retail outlets (at least the Australasian ones. Something I wish I'd discovered a while ago...), though in this case the ZWO price is the same as OPT.

https://astronomy-imaging-camera.com/pr ... m-pro-mono
-------------------------------------------------
Martinborough, New Zealand. Alpy, Lhires RC12
James Foster
Posts: 439
Joined: Sun Jan 24, 2016 7:14 am

Re: eShel optim. + ASI6200MM CMOS camera

Post by James Foster »

To: Tom

RE:"James, it looks as if OPT sell the ASI 6200MM for only $250 more than the Atik."

I have a friend who can sell me his used atik-16200 for almost 1/2 that price so I'm VERY interested to know
if it a suitable replacement. If I cant answer him in the next few days the deal is off.

Also note that almost every ASI6200MM is on back order, so even if I had the cash now, I'd be lucky to get it by Oct20!

James
James Foster
eShel2-Zwo ASI6200MM 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
James Foster
Posts: 439
Joined: Sun Jan 24, 2016 7:14 am

Re: eShel optim. + ASI6200MM CMOS camera

Post by James Foster »

RE: Atik-16200

I re-read the specs (its not full-frame, diagonal is 35mm, not 42mm) and according to Francois at Shelyak, its older CCD technology which
is inferior to what Christian tested for the ASI6200MM CMOS camera.

Guess I'll acquire the ASI6200MM at some point, but putting the rest of the eShel components is not a trivial financial task!
I will post on a separate thread what my results are using my old SBIG STL-11K full frame camera in place of the ASI6200MM while
using everything else Christian tested.....may need a portable wine cellar if I ever use this at Mt. Pinos, CA!

James
James Foster
eShel2-Zwo ASI6200MM 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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