Improved SHG H-alpha imaging at 700mm FL

I LOVE finding out about different ways to appreciate the Sun and light in general. Use this forum to post your info or questions about various outside the mainstream ways to appreciate our life giving star!
Post Reply
thesmiths
Almost There...
Almost There...
Posts: 1053
Joined: Mon Jun 04, 2012 8:13 pm
Location: London, England
Has thanked: 42 times
Been thanked: 1485 times

Improved SHG H-alpha imaging at 700mm FL

Post by thesmiths »

We decided to get a new diffraction grating for our "foam board" spectroheliograph. The new one is a 30mmx30mm 2400 l/mm holographic grating from Edmund Optics. The old one (which we had had around for many years) was a 50mmx50mm 1800 l/mm ruled grating from Thorlabs. The new grating, because of the increased dispersion, should give increased contrast of surface features (and it does seem to deliver on the promise). Here is a composite of two images, East and West, taken with two scans. Our SHG software is able to generate the protuberance images simultaneously and we could assemble this mosaic fairly effortlessly.

SHG H-alpha, 700mm FL, 106mm APO, 2400 l/mm grating
SHG H-alpha, 700mm FL, 106mm APO, 2400 l/mm grating
141958_141214.jpg (325.93 KiB) Viewed 849 times

The average FPS was 432 and the ROI was 2000x120. The exposure was 2.1 ms and the scan was 16x sidereal rate (approximately 8 seconds per scan). The camera was a ZWO 178MM at a gain of 190.

The SHG image compares favourably with a full disk image using an etalon: viewtopic.php?f=4&t=33121 taken on the same day.

Next improvement needs to be the slit, which is too short (only 3mm long, hence not being able to cover the full disk even with two scans). Our old 10 micron wide Thorlabs slit has also suffered wear and tear over the years which results in the vertical lines (and that is difficult for the automated software to entirely remove).
Last edited by thesmiths on Wed Aug 25, 2021 9:16 am, edited 1 time in total.


User avatar
Montana
Librarian
Librarian
Posts: 34526
Joined: Mon Oct 17, 2011 5:25 pm
Location: Cheshire, UK
Has thanked: 17521 times
Been thanked: 8763 times

Re: Improved SHG H-alpha imaging at 700mm FL

Post by Montana »

WOW!! absolutely magnificent! they just get better and better :hamster:

:bow :bow :bow
Alexandra


User avatar
marktownley
Librarian
Librarian
Posts: 42120
Joined: Tue Oct 18, 2011 5:27 pm
Location: Brierley Hills, UK
Has thanked: 20229 times
Been thanked: 10111 times
Contact:

Re: Improved SHG H-alpha imaging at 700mm FL

Post by marktownley »

Very good indeed, really impressive results!


Image
http://brierleyhillsolar.blogspot.co.uk/
Solar images, a collection of all the most up to date live solar data on the web, imaging & processing tutorials - please take a look!
User avatar
DeepSolar64
Way More Fun to Share It!!
Way More Fun to Share It!!
Posts: 18717
Joined: Thu Sep 05, 2019 12:19 am
Location: Lowndesville S.C.
Has thanked: 17449 times
Been thanked: 16548 times

Re: Improved SHG H-alpha imaging at 700mm FL

Post by DeepSolar64 »

It certainly has nice contrast!!


Lunt 8x32 SUNoculars
Orion 70mm Solar Telescope
Celestron AstroMaster Alt/Az Mount
Meade Coronado SolarMax II 60 DS
Meade Coronado SolarMax II 90 DS
Meade Coronado AZS Alt/Az Mount
Astro-Tech AT72EDII with Altair solar wedge
Celestron NexStar 102GT with Altair solar wedge
Losmandy AZ8 Alt/Az Mount
Sky-Watcher AZGTI Alt-Az GoTo mount
Cameras: ZWO ASI178MM, PGR Grasshopper, PGR Flea
Lunt, Coronado, TeleVue, Orion and Meade eyepieces

Image Visual Observer
" Way more fun to see it! "
Post Reply