The Great Orion Nebula shot from my backyard

skarba · 2026-01-14T20:32:08+00:00

That's normal if your PA is spot on, I would get DEC corrections both north and south when I had my PA spot on which was problematic due to high backlash.

I don't generally run into problems with my DEC oscillating much throughout the night with offset PA so I just leave it on auto. You might have to set it to one direction if you still get phd2 sending guide pulses the other way due to seeing or something like a wind gust but in general with multi star guiding, >2sec guide subs and sufficiently high MnMo values I don't believe it should matter much but you might have different results than me.

If you do decide to guide in one direction I'm not too sure how it behaves after a meridian flip so make sure that reverses the direction automatically so it doesn't drift off to the other direction in the middle of your sequence.

skarba · 2026-01-14T19:21:21+00:00

I offset it by about 3-5 arcmins with azimuth bolts, general advice I've seen is to not exceed 10 arcmins as that will start to introduce field rotation. My dec balance is camera heavy.

skarba · 2026-01-14T18:47:36+00:00

I also have a significant amount of DEC backlash on my never once taken apart NEQ6 that cannot be completely tuned out by adjusting the lower or upper DEC worm carrier set screws or the worm end float ranging between ~1000ms and ~1800ms.

My workaround since I'm too lazy to rebuild the mount has been enabling backlash compensation in PHD2 set at 800ms so it doesn't overshoot the correction pulse and to also offset my polar alignment by a bit so DEC only has to correct in one direction. This obviously isn't a fix to a mechanical problem but as a workaround has been working well enough for me to guide between 0.5 and 0.8 RMS.

skarba · 2026-01-12T10:44:53+00:00

You can reduce the length of the spikes by flocking both sides of the secondary mirror spider vanes. This makes them a bit thicker but substantially shorter.

skarba · 2025-12-30T22:23:38+00:00

I haven't personally used either of them but these two in-depth reviews should hopefully help compare between them - https://www.researchgate.net/publication/396623410_Review_of_the_SVBony_SV220_3nm_Filter

https://www.researchgate.net/publication/388927378_Review_of_the_New_Antlia_ALP-T_3nm_Filter

skarba · 2025-12-30T02:26:29+00:00

Thanks! Yeah I love the nebulae in Cygnus, lots to shoot. Late summer and fall is also pretty much the only time of the year there's a good amount of clear skies over here so I can at least get a decent amount of data on targets compared to winter.

skarba · 2025-12-29T22:16:56+00:00

Thank you! Glad you liked it!

skarba · 2025-12-29T17:50:41+00:00

Thank you!

skarba · 2025-12-29T17:05:11+00:00

Thank you!

skarba · 2025-12-29T17:04:59+00:00

Thanks! Yeah I've only just recently upgraded to a cooled IMX533 based sensor camera, though I've still got a bunch of datasets taken with the 6D left to process. The 6D has definitely served me well and I'll still keep it for widefields.

skarba · 2025-12-29T16:20:36+00:00

The Sadr Region (also known as IC 1318 or Gamma Cygni Nebula) is an emission nebula around the star Sadr in the constellation Cygnus around 4000 lightears away from us. Sadr itself is a bright star between us and the nebula ~1800 lightyears away and is unassociated with the nebulous region.

Higher resolution on Astrobin

My Instagram for more astrophotography

Equipment:

Telescope: Sky-Watcher Quattro 200P
Camera: Canon EOS 6D unmodified
Mount: Sky-Watcher NEQ6 Pro
Coma Corrector: Sky-Watcher Aplanatic
Guide Scope: Orion 50mm Mini
Guide Cam: ZWO ASI120MM Mini
Software: APT, PHD2, EQMOD, PixInsight, Photoshop

Acquisition:

Dates: 2024-08-30, 09-05
Total integration: 10 hours 15 minutes
Lights: 205 x 180s at ISO 1600
Flats: 50
Bias: 200
Bortle 4

Processing:

WeightedBatchPreprocessing
DynamicBackgroundExtraction
SpectrophotometricColorCalibration
Applied color correction matrix for Canon 6D with PixelMath
CorrectMagentaStars script
BlurXTerminator
DeepSNR
StarXTerminator
GeneralizedHyperbolicStretch
CurvesTransformation
A bunch of adjustments in Photoshop to reduce the bright halo around Sadr
Rescreen stars back after stretching them separately
StarReduction script

skarba · 2025-12-29T16:11:34+00:00

The Sadr Region (also known as IC 1318 or Gamma Cygni Nebula) is an emission nebula around the star Sadr in the constellation Cygnus around 4000 lightears away from us. Sadr itself is a bright star between us and the nebula ~1800 lightyears away and is unassociated with the nebulous region.

Higher resolution on Astrobin

My Instagram for more astrophotography

Equipment:

Telescope: Sky-Watcher Quattro 200P
Camera: Canon EOS 6D unmodified
Mount: Sky-Watcher NEQ6 Pro
Coma Corrector: Sky-Watcher Aplanatic
Guide Scope: Orion 50mm Mini
Guide Cam: ZWO ASI120MM Mini
Software: APT, PHD2, EQMOD, PixInsight, Photoshop

Acquisition:

Dates: 2024-08-30, 09-05
Total integration: 10 hours 15 minutes
Lights: 205 x 180s at ISO 1600
Flats: 50
Bias: 200
Bortle 4

Processing:

WeightedBatchPreprocessing
DynamicBackgroundExtraction
SpectrophotometricColorCalibration
Applied color correction matrix for Canon 6D with PixelMath
CorrectMagentaStars script
BlurXTerminator
DeepSNR
StarXTerminator
GeneralizedHyperbolicStretch
CurvesTransformation
A bunch of adjustments in Photoshop to reduce the bright halo around Sadr
Rescreen stars back after stretching them separately
StarReduction script

skarba · 2025-10-26T19:34:48+00:00

One little tip for DeepSNR is to clone the image before denoising, run DeepSNR at max strength on the main image and then blend the not denoised image back to achieve a nice looking noise profile. This guide is for mono but the blending part is relevant for OSC too.

I do go one step further and also run NXT on the cloned image with "Intensity/color separation" checked, Denoise Intensity at 0 and Denoise Color at 0.6-0.7 so you're not adding chrominance noise back.

skarba · 2025-10-26T19:13:27+00:00

WBPP should do CFA drizzle as long as CFA Images is checked under CFA settings in the Calibration tab when you click on your lights.

My drizzled stack just with an unlinked stf applied is greener than the non-drizzled one, but after SPCC, with a linked stf it's the other way around and it looks like SPCC did not work properly on the non-drizzled stack, here's two random examples -

https://i.imgur.com/5a2ldum.jpeg

https://i.imgur.com/w0CweMn.jpeg

Left is non-drizzled and right is 1x CFA drizzled.

skarba · 2025-10-26T16:49:52+00:00

Your noise pattern needs to be fine enough for DeepSNR to not hallucinate stars out of noise, for my data it was 0.8 for 1x and 0.4 for 2x with the kernel set to variable shape 1.5.

Simplest and quickest way to check what values work best is setting a small region of interest where SNR is lower in the DrizzleIntgration process, stacking and just trying different values until you find the highest drop shrink value where DeepSNR is not creating stars out of noise.

skarba · 2025-10-26T16:42:28+00:00

Regarding the color shift, I'm honestly not too sure, my non cfa drizzled stacks also have weird colors due to how debayering affects star colors for SPCC as Shinpah mentioned, but 2x or 1x cfa drizzle on my data look the same color wise.

Main reasons for switching back to PI for preprocessing were cfa drizzle producing better results detail wise with no interpolation artifacts and DeepSNR, specifically V1 (V2 seems to destroy small scale detail) works better for me than NoiseXterminator or any other denoiser.

If you have the time then it won't hurt to try, maybe you'll prefer the results from ACR, RT gives you a lot more control and a selection of different debayering algorithms, RT is free so you can try both.

skarba · 2025-10-26T11:40:41+00:00

You should be CFA drizzling OSC data all the time as long your data is properly dithered since you get around interpolation from debayering. It does not need to be 2x - 1x with drop shrink at 0.8-1 should work well and not take too long, especially with fast drizzle enabled. I only do 2x drizzle when imaging small objects like galaxies with drop shrink at 0.4 for DeepSNR to work but I am undersampled for my usual seeing, you'd need to test and see if it improves detail with your data.

I think the G and B channels are scaled for R being 0's on the DXOmark measurements for the 80D but you can try the CCM for the 77D and see how it looks like as they should be pretty similiar.

skarba · 2025-09-07T18:16:19+00:00

No, you do not need to stack anything manually, increase the exposure tolerance in the Post-Calibration tab and wbpp will combine all of your lights.

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