Request for SHG owners

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ChrisHalpha2017
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Request for SHG owners

Post by ChrisHalpha2017 »

Hello guys...
I need help from those you have a SHG :

My experiments with wide slit observations of prominences show that the 600 lpm grating gives the best definition of the images.

Could it be possible for those who have a 1200 or 600 lpmm grating to image the sun with it ? I would like to see what the proms will look like with such gratings ( even if the sun's disk details wont be visible).
Im interested to see the effect of the grating on the prominence image quality with a thin narrow slit in SHG mode.

Thank you in advance.

CHRIS


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Re: Request for SHG owners

Post by highfnum »

i have 1200 only no 600 yet
ill try 10u slit


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Re: Request for SHG owners

Post by ChrisHalpha2017 »

Thank you ;)


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Re: Request for SHG owners

Post by fulvio.mete »

Hi, Chris:
Unfortunately I own only 2400 and 1800 g/mm gratings spectrographs, .Anyway, in my opinion, the higher is the grating resolution, the better could be the spectral image and spectroheliograms quality in digital SHG .

Cheers

Fulvio


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Re: Request for SHG owners

Post by p_zetner »

Hi Chris.

This thread shows my recent study of a prominence in H alpha and CaK using a spectroheliograph.
viewtopic.php?t=28630

For this particular imaging session, I was using a 1800 l/mm grating but, generally, I use a 2400 l/mm grating.
If you read through the thread you can see that I generated some dopplergrams and also examined spectra at various locations inside this prominence.

Some earlier (2015) work on a CaK prominence is presented here:
viewtopic.php?t=17102
Still learning my SHG craft at this point so the images were a little crude.

Cheers.
Peter


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Re: Request for SHG owners

Post by ChrisHalpha2017 »

@fulvio

Hmmmm..
I'm not conviced as my trials shows the opposite. The more dispersive grating and the more the image is squashed through anamorphosis. I tried with gratings from 600 to 2400 lpmm .Thats why i needed to check with people who are used to Digital SHG.

The more dispersive the grating is and the higher the spectral resolution will be but not necessarily the spatial resolution. Look at my posts with different gratings and you can see it.

I'll will try in SHG mode as soon as the sun comes back...


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Re: Request for SHG owners

Post by fulvio.mete »

Chris, both me and C.Buil, that isn't surely a newby of spectroscopy and a precursor of digital SHG, use in general 2400 g/mm grating for SHG.The higher the spectral dispersion and resolution, the higher the definition of spectroheliograms.In my case , with my VHIRSS (for example) with a 2400 g/mm, H Alpha line is 60 pixel wide, and this permits to go deeper in the line with only one pixel image, or make the stacking of 60 one pixel images with good results.Anyway, if you are not convinced, could just give a try with two difefrent grating, a 600 and a 2400 g/mm.


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Re: Request for SHG owners

Post by ChrisHalpha2017 »

Hello,

I dont know ; i've been using the wide slit method for 24 years so far and i'm still experimenting :)


with my spectro and 2400tmm the H alpha line is 20 pixel wide but i'm not talking about spectral dispersion nor spectral resolution. I'm considering spatial resolution and so far my results are that with the 600lpmm the image of the prominence is better. That hold to the fact that i'm not using a thin band 1pixel wide to form an image but i use the whole H alpha line itself!! So the wider it is because of dispersion the more blurry my image will be. If selected a 1 pixel line that would be a completely different matter i guess but I have to try to see what the result will be. I'm not looking for the suns disk features for the moment but mainly the prominence image . I dont know If i express my thoughts acuretely as English isnt my first language ;)
But soon I will see ...i mean as soon as i will understand how to use virtual dub to make the SHG .


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Re: Request for SHG owners

Post by highfnum »

weather has been a pain but i tried 1200 today
2400 lpmm opens emission line
this shot is with 50X300 scope in front and 50X300 camera scope
F6g2400.JPG
F6g2400.JPG (11.18 KiB) Viewed 1001 times


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Re: Request for SHG owners

Post by highfnum »

this is 60X900 scope and 50X300 camera scope
it much thinner and brighter
f11g1200.JPG
f11g1200.JPG (13.27 KiB) Viewed 1000 times


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Re: Request for SHG owners

Post by highfnum »

tried partial
of course clouds rolled in (grey streaks)
but edge is sharp
and surface mottling is there
fc2_save_2022-06-13-183152-0000ha1200b_00010u.jpg
fc2_save_2022-06-13-183152-0000ha1200b_00010u.jpg (65.46 KiB) Viewed 999 times


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Re: Request for SHG owners

Post by highfnum »

ok much better sky today
got a good half sun scan
10 micron slit
1200lpmm grating
60 f11 scope
nice
im happy
fc2_save_2022-06-14-174047-0000ha120010u_000u10v1200.jpg
fc2_save_2022-06-14-174047-0000ha120010u_000u10v1200.jpg (129.23 KiB) Viewed 971 times
fc2_save_2022-06-14-174047-0000ha120010u_000u10v1200c.jpg
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Re: Request for SHG owners

Post by highfnum »

this maybe cleaner
i think wind gust hit middle of previous shot
fc2_save_2022-06-14-175800-0000hau10v1200_000c.jpg
fc2_save_2022-06-14-175800-0000hau10v1200_000c.jpg (248.5 KiB) Viewed 967 times
fc2_save_2022-06-14-175800-0000hau10v1200_000b.jpg
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Re: Request for SHG owners

Post by highfnum »

redo with skip 1 line
fc2_save_2022-06-14-175800-0000hau10v1200_000l1s.jpg
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Re: Request for SHG owners

Post by highfnum »

tried cak
1200lpmm
fc2_save_2022-06-15-113253-0000cakcah1200v10u_000k.jpg
fc2_save_2022-06-15-113253-0000cakcah1200v10u_000k.jpg (135.11 KiB) Viewed 930 times


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Re: Request for SHG owners

Post by ChrisHalpha2017 »

very nice :) What fo you think about the prominence image ? can you scan with the 2400lpmm in the same session to compare?


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Re: Request for SHG owners

Post by ChrisHalpha2017 »

Here is proof that with the wide slit method the less dispersive grating gives the best image definition :


600 lines/mm gives that :
600 tmm classic  stacked 2 ++++++++  PHOTO 2.jpg
600 tmm classic stacked 2 ++++++++ PHOTO 2.jpg (513.58 KiB) Viewed 896 times

and the 1200 lines/mm

13_43_35_Soleil  H alpha_16_06_22_F2213-2749   STACKED  PHOTO 5 b.jpg
13_43_35_Soleil H alpha_16_06_22_F2213-2749 STACKED PHOTO 5 b.jpg (317.32 KiB) Viewed 896 times
.


we can see the effect of anamorphosis : the image is squashed and the loss of resolution is due to the fact that each point of the image est dispersed and becomes a elipse or a line depending on how strong the dispersion.

Of course in the case of a SHG this doesnt apply as only a thin line of pixel is selected.

to be continued..

Chris


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