SharpCap Forums

It's about time to bid farewell to the winter nebulae this year. I enjoyed their beautiful one last time through EAA.
Here's the live-stacked image from that session.

-Capture data
C50：15s × 80 (Total 20min) Gain=500
NGC2024,IC434：15s × 80 (Total 20min) Gain=500
M42,M43 : 4s × 225 (Total 15min) Gain=500
No Dark, No Flat, Aply "Hot and Cold Pixel Removal"

Equipment: Celestron AVX, SkyWatcher EvoGuide50EDⅡx flattener, SV605CC cam, Sightron DBP / SVBONY UHC filter, SV165 guider, SV905C guide cam
Software: SharpCap, PHD2, GIMP

-All opinions are welcome
The second image, Horsehead and Flame, but there’s a odd spike around Alnitak (& other bright stars as well). What do you think this might be?
There didn’t seem to be any issues with the guiding graph, so I suspect that the short settling time setting caused the shooting to begin before the mount stabilized after dithering. However, to be honest, I don't fully understand it in reality.
I’d greatly appreciate any insights or opinions from experienced individuals regarding the cause.

And this is my first sharing images. I would greatly appreciate your feedback, including any suggestions for improvement.

Regards,
Takuya

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Hi,

nice images - all three of them - thanks for sharing

Looking at the spikes on the star in the horsehead/flame image, if you zoom in a bit you can see that they are there on the fainter stars too. It's *not* in the RA direction, so it's unlikely to be an issue with tracking or something like jumps in the RA direction. Given that, I'd be wondering about something that was affecting the image in the way that the newtonian spider vanes add spikes to images. Anything that disturbs the perfect circularity of the aperture of the telescope can give noticeable diffraction patterns - I have a Vixen ED81S, and the lens is held with 3 tabs that protrude about 1.5mm into the circularity of the aperture and they give noticeable diffraction effects, especially after stretching the image.

cheers,

Robin

Hi Robin,

Thank you very much for your sensible advice.
Indeed, when looking closely at the faint stars, I notice some of them have small spikes in different directions. I had never been bothered by such spikes with this telescope before, and since the first and third images and as well as others taken on the same day, didn't show any noticeable spikes, I suspected an issue with the mount's movement during the Horsehead session.
However, since there are bright stars with and without spikes, it doesn't make sense as a mount issue. Upon closer inspection, there are faint stars with spikes in other images as well. While I'm not entirely certain, it seems that some spikes appear in the same locations.
I will check the OTA.

Regards,
Takuya

Hi Robin,

I found the cause. The screw (silver: not in use) on the flattener was slightly protruding into the tube.
This is most likely the cause. It was a easy mistake…
Thank you very much for your advice.

Regards,
Takuya

Hi,

glad you found it - time for some black paint, or just remove it or back it out a bit

cheers,

Robin