eShel + IMX455 Sony

Design, construction, tuning of spectroscopes
Information and discussion about softwares (telescope remote, autoguiding, acquisition, spectral processing ...)
Bernard Heathcote
Posts: 84
Joined: Mon Sep 26, 2011 10:09 am

Re: eShel + IMX455 Sony

Post by Bernard Heathcote »

Thanks to the continued efforts of Christian and Shelyak's support it is great that my 10 year old eShel can still have its performance improved!

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

Re: eShel + IMX455 Sony

Post by James Foster »

To: Bernard,

Here is the adapter (red outline) Francois provided for my eShel-to-Canon 135mm:
Image
Note the eShel was in the "wine-cellar" (small liquor refrigerator) kept at 50 deg F while taking this picture.
Also note that this adapter has 3 small hex bolts (120deg apart) to facilitate rotation of the lens/sensor on the eShel.

When I get my ASI6200MM Pro, I'll have to get a bayonet adapter to interface the Canon lens to itself.

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
Bernard Heathcote
Posts: 84
Joined: Mon Sep 26, 2011 10:09 am

Re: eShel + IMX455 Sony

Post by Bernard Heathcote »

James,

The current severe coronavirus travel restrictions in Australia means that postage from overseas can take two to three months to arrive so I will, at least initially, have to 3D print my Canon adapter (I did this when I had the Samyang 135mm).

The lower ring with the three locking screws is actually part of the main eShel body and not part of the adapter supplied by Shelyak.

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

Re: eShel + IMX455 Sony

Post by James Foster »

Yes its the part above the eShel rotational adjustment ring(red outline).......I think Francois has this part it in stock.....got it from Fr to Us in about 8 days!

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
Christian Buil
Posts: 1431
Joined: Mon Sep 26, 2011 6:59 pm
Contact:

Re: eShel + IMX455 Sony

Post by Christian Buil »

Une mise à jour assez complète de ma page sur l'optimisation de eShel :

http://www.astrosurf.com/buil/asi6200mm/

(but still in French for the moment, really sorry).


Christian
Bernard Heathcote
Posts: 84
Joined: Mon Sep 26, 2011 10:09 am

Re: eShel + IMX455 Sony

Post by Bernard Heathcote »

Christian,

Thanks for the October update to your original July paper on eShel optimisation ... an outstandingly detailed and valuable document on how to improve the 'blue' performance!

I now have the Canon 135 f/5L lens, new collimator, 50 micron OH fibre and have just added a 200mm f/5 Newt to my collection. I now appreciate that I also need to get the 200 micron OH fibre for calibration, as even the 4700 K halogen lamp isn't strong enough with the original fibre. I am using a ZWO ASI1600MM until I can convince myself that a better camera can be justified to my spouse.

We are all in your debt for your many many freely given contributions to amateur spectroscopy over the past 25 to 30 years!

Bernard
Tom Love
Posts: 64
Joined: Sun Apr 21, 2019 5:57 am

Re: eShel + IMX455 Sony

Post by Tom Love »

Out of interest, the standard focal ratio advertised for the eShel guiding module is 6. But how low can you realistically go with this instrument? Is it possible to go down to f/4?
-------------------------------------------------
Martinborough, New Zealand. Alpy, Lhires RC12
Bernard Heathcote
Posts: 84
Joined: Mon Sep 26, 2011 10:09 am

Re: eShel + IMX455 Sony

Post by Bernard Heathcote »

Tom,

According to Christian's research, reported in his recent excellent paper on optimising the eShel, he advocates using a scope between f/3.5 to f/4 for optimal fibre performance and shows excellent results with 200mm f/5 and 250mm f/4 Newtonians.

Bernard
Christian Buil
Posts: 1431
Joined: Mon Sep 26, 2011 6:59 pm
Contact:

Re: eShel + IMX455 Sony

Post by Christian Buil »

Tom,


The optimization of eShel for very fast optical beams is another area of ​​work that I analyze.

There are a lot of things:

(1) the characteristic aperture of the current guidance module is near f/5, and clearly a fast telescope from f/3.5 to f/4.5 is poorly exploited at the present time (it is a little more complicated, because the beam distribution at the output of the fiber is more Gaussian than uniform, which is rather favorable).

(2) The current guidance system is not perfectly achromatic, which causes flux losses in the UV (and IR). I have defined a new optical system for very fast beam and almost completely achromatic telescopes, but unfortunately I am not sure that Shelyak will realize it in the near future...

(3) I also study the possibility of increasing the internal aperture of eShel, it is surely the most complicated.

(4) I also have in mind a new calibration box: hotter tungsten lamp, wider choice of spectral lamp, lower price ...

(5) ...

The work is not finished !

Christian
Tom Love
Posts: 64
Joined: Sun Apr 21, 2019 5:57 am

Re: eShel + IMX455 Sony

Post by Tom Love »

Dear Christian - these are all very interesting developments indeed. I look forward, yet again, to the results of your astonishing work!

I had been wondering whether there was any point in using a simple image slicer, like the CAOS one, to try and squeeze some additional resolution out of an eShel. But I suspect that it probably introduces more complexity for too little gain.

The more I think about it, the more it seems to me that a fast f/4 Newtonian is a very good telescope for spectroscopy with Shelyak spectrographs. You can use it natively at f/4 for an Alpy or eShel, without any refracting optics messing up the spectral transmission. And you can use a barlow or other high quality extender (like a televue) to go to f/8 for a Lhires, when a narrow view of the spectrum means that transmission curves are less of a problem. This seems to me a better setup than using an f/8 GSO RC for the Lhires, and using a reducer to bring it down to f/6 for an Alpy, as I am currently doing.

Is this a reasonable understanding?

Best,

Tom
-------------------------------------------------
Martinborough, New Zealand. Alpy, Lhires RC12
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