H-alpha SHG, Oct 6 -- good seeing

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H-alpha SHG, Oct 6 -- good seeing

Post by thesmiths »

It is quite a challenge to get any imaging done this time of year as I have to catch the Sun as it passes between rooftops. This is the problem doing astronomy in central London. On the positive side, the cool autumn air appears to have much less turbulence. During the summer, I could only image for a short period very early in the morning before things heated up too much. I did three sets of scans (consuming 300GB of disc space) between 07:59 UTC and 09:59. The last set was the best, as it turned out.

The 1st image below (the full disc) is best looked at by opening the image in a new tab. The 2nd one (inverted) is best seen by clicking on the image.

H-alpha SHG: 106mm / 720mm APO refractor. 2400 l/mm grating. 9 micron wide chrome on fused quartz slit. ZWO 183MM camera. Stack of 14 of 27 frames. AS!3, ImPPG, Photoshop Elements. October 6, 09:50 UTC to 09:59 UTC.
H-alpha SHG: 106mm / 720mm APO refractor. 2400 l/mm grating. 9 micron wide chrome on fused quartz slit. ZWO 183MM camera. Stack of 14 of 27 frames. AS!3, ImPPG, Photoshop Elements. October 6, 09:50 UTC to 09:59 UTC.
061022-Ha-3-720mm-2400g-stack-14.jpg (1.09 MiB) Viewed 1255 times
H-alpha SHG: inverted and cropped
H-alpha SHG: inverted and cropped
061022-Ha-3-720mm-2400g-stack-14-invert-crop-b.jpg (1.22 MiB) Viewed 1255 times
H-alpha SHG: inverted and cropped
H-alpha SHG: inverted and cropped
061022-Ha-3-720mm-2400g-stack-14-inverted-small-crop.jpg (360.02 KiB) Viewed 1249 times

Using Ken Harrison's SimSpec SHG spreadsheet, the resolving power is 56,300, the spectral resolution is 0.12 angstrom, and the best spatial resolution is 1.4 arcsec. I think due to the cool weather conditions, the spatial resolution was amongst the best I have so far achieved with the SHG technique.

Instrument update: I finally received the ZWO electronic focuser (ordered directly from the company) and found it to be very useful to get the telescope focus just right. I allows making very small back and forth focus adjustments without causing telescope vibration. I used ASCOM via FireCapture and the software allows for backlash compensation, which also helps considerably. I had also intended to use the electronic focuser to do remote focusing while indoors, but the shortness of this imaging session meant I had no time to even go indoors.

Spectrohelioscope with electronic focuser installed.
Spectrohelioscope with electronic focuser installed.
1557.jpg (488.74 KiB) Viewed 1255 times
Last edited by thesmiths on Fri Oct 07, 2022 9:31 am, edited 2 times in total.


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Re: H-alpha SHG, Oct 6 -- good seeing

Post by DeepSolar64 »

300GB of disk space. WoW...

These look like standard Ha images through an etalon. VERY nice!!

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Re: H-alpha SHG, Oct 6 -- good seeing

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DeepSolar64 wrote: Fri Oct 07, 2022 4:46 am 300GB of disk space. WoW...
I've gone through 7 TB of archival hard disk storage in 2022 (this was really the first year I've done SHG work seriously). The sum total of all astronomy in 2021 that was around 2TB. At some point, I guess I will go delete some of the old SER files.


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Re: H-alpha SHG, Oct 6 -- good seeing

Post by DeepSolar64 »

It’s data intensive that’s for sure. You need BIG hard drives!!

Are they any way to configure an SHG for visual use? I bet not.

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Re: H-alpha SHG, Oct 6 -- good seeing

Post by Montana »

Wow!! just WOW!! you set the bar so high :bow :bow :bow :hamster:

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Re: H-alpha SHG, Oct 6 -- good seeing

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DeepSolar64 wrote: Fri Oct 07, 2022 2:09 pm Is they any way to configure an SHG for visual use?
I don't think there is. If you work with a fairly short focal length (like with a 72mm f6), the scan will finish in about 5 or 6 seconds and will take a comparable amount of time to generate an image.


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Re: H-alpha SHG, Oct 6 -- good seeing

Post by DeepSolar64 »

Yes. The scanning process makes it unstable for visual use. Does anyone make an SHG, professional or amateur that will do visual or do they all use the same scanning process? I am ignorant on such matters.


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Re: H-alpha SHG, Oct 6 -- good seeing

Post by marktownley »

Your SHG images are the gold star reference Douglas!


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Re: H-alpha SHG, Oct 6 -- good seeing

Post by torsinadoc »

Incredible :bow


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