2022 Astrophotography photos

[wols...@gmail.com]

Hi Everyone,I just finished polishing up my astrophotos from 2022 and posted them to my website. I think some of them are pretty darn good. If you get a chance...have a look. Of course, all of the LIGHT frames were calibrated using CaLIGHTs.

Peter

https://astrohobby.ca/astrophotography-2022/

[Craig Richardson]

Gorgeous work, really top notch compositions  - and realistic!  Your C8 Edge is Really flat = WoW!  I've been trying to get a really good rendering of Crescent ngc6888 and not used to working with a new to me Triad Tri-band and see you take reasonably long exposures it may be my "missing part" to get really good faint detail and also learning how to use and Ioptron ieq45 (class 6) mount and will put more effort into getting longer exposures on those rare windless nights - also could/will set up better "wind blocks"

This ngc6888 is from comparatively short 80 second exposures with mostly mediocre seeing using a 6" ES mak Newt, my first reasonable results using narowband OSC on a faint target. I hope someday soon to approach the quality and detail you are producing!

https://www.cloudynights.com/gallery/image/219149-crescent-nebulea-ngc-6888-1h39m403kappaclip2xdrizzlesuper-siril-stoolsshrink-triadcore2h15m-dnzpybkgrnd-ooh-coreentropy-14h51m33s-661frmsgimp-1600px-crop/

Craig

https://www.cloudynights.com/user/374165-craigar/

[wols...@gmail.com]

Craig,

Thanks for your generous comments. I am pretty happy with how my 8" EdgeHD performs at F10. When I use the 0.7 reducer I see issues with star colors at the edges of my images. The RGB colors don't align. This issue only happens when I am using my LeNhance NB filter. DSS does a good job of catching and correcting this by make sure the "Align RGB Channels in final image" box is checked. I also think I have fewer issues to deal with because I use a QHY294C with it's smaller imaging chip and an OAG. 

Long exposure imaging demands an OAG with an SCT. The differential flexure can be quite significant. I find that long exposures have much better SNR and it doesn't burn up disk space with short exposures. Star saturation is important to avoid...but there always is a compromise between faint details and colorful stars. Light pollution is always a problem...I am lucky to have access to a dark sky site. I use the CaLIGHTs StarSatGuard combined with the Multiplier to boost the nebulosity while also dimming bright stars. Be sure to read my posts regarding CaLIGHTs especially this one. https://astrohobby.ca/2023/04/26/calights-dynamic-range-compression/

Your ngc6888 image is the kind of image that inspires astrophotographers to keep going, learn more, and hone their skills. Very nice pic.

Thanks for posting

Peter

[Craig Richardson]

Thank you for the detailed response with good tips!.. with the C9.25 and a wide thick dovetail and a beefy saddle on the ieq45 I don't notice a flexure blur using a 50mm guide scope (with a 3.75um mono guide camera) mounted on the OTA's stock V clamp ( on top at about 135 degree angle relative to the Vixen dovetail) and seem to be getting good results so far  - but I believe it is highly possible that I may get better results with this guide camera and an OAG (especially for SCT's) , but I'm not really that sure cause I seem to do best with 1.5 second guide frames, but maybe could use quicker exposures with an OAG BUT with this .33reducer the stars out side the "good focus" circle are pretty bad).  I'm experimenting imaging with a 2.9um imx485 OSC camera (and using a generic .33 reducer with it to get a better "pixel to F/ ratio") - if it could do Bin2 properly with SharpCap in still mode for automated dithering (the problem is most likely from bad Bin2 code in QHY's driver, it produces grey scale frames..), I'd get 4x the amount of light  (at 1/2 the potential resolution BUT my seeing is usually only mediocre so it would probably be no worse) - and I could also try bin3 , hoping it may be OK with the QHY's driver ) and a much more forgiving generic .63 reducer.   This is what I've got so far with 55second exposures, about 5hrs stacked and only stretched and color balanced with with Siril - no sharpening or AI.

Also looking forward to trying your suggestion "I use the CaLIGHTs StarSatGuard combined with the Multiplier to boost the nebulosity while also dimming bright stars."

[wols...@gmail.com]

Craig,

Differential flexure in my 8" SCT is roughly 30 to 40 arc-seconds per hour. I believe the lion's share of this flexure is caused by the big SCT mirror shifting due to gravity and the mount slowly rotates. I use the mirror clutches but they don't help  very much. You will not  see this kind of differential flexure until your exposures are several minutes or more and the pixel scale of your imaging camera is 1"/px or less. 40 arc-seconds per hour is equivalent to 0.67 arc-seconds per minute. I use QHY cameras and my experience has been that the camera driver 2x2 bin for color cameras yields greyscale images with a checkerboard pattern down at the pixel level. I did some experimenting with my QHY294C camera and I can reduce the checkerboard pattern if I adjust the color balance ratios for the camera to R2.0 B1.5 and G1.0. You need to first know what the unity whitebalance values are for your camera. A value of 16 is the equivalent whitebalance of one. So to set the whitebalance to R2.0 B1.5 and G1.0 I would set the Red whitebalance to 32, Blue whitebalance to 24 and green whitebalance to 16. I have written a lot of software for my set-up and I autofocus my QHY294C at 2:2 binning with this whitebalance scheme. Despite the grey image...It seems to yield tightly focused images when I image at 1:1 binning.

Peter

BTW...an OAG completely eliminates differential flexure.

[wols...@gmail.com]

Craig,

My bad...I didn't understand your comments regarding your imx485 OSC camera. Let me try again. I would suggest that you don't bother with 2:2 binning via the driver and, instead, use 2x2 color binning in CaLIGHT. It separates the RGGB color channels  into four separate images and then 2:2 bins each image. I then recombines the four separate images into a RGGB color image. The downside is that you much acquire your images at full resolution. The very much upside of CaLIGHT 2:2 color RAW (i.e.RGGB before debayering is applied)binning is a 50% reduction in color noise. Binning the image after debayering (i.e. RGB) yields roughly 50% for the green channel but only 20 to 30% for the red and blue channels. So you end up with a color image that has the maximum possible noise reduction. 

Regardless of which way you 2:2 bin there is a 16 bit limit that you can't get around. I don't remember what the driver does but I think it adds the four pixel values together and the sum is clamped at 65,535. The imx485 has a 12 bit sensor so this can be done without clamping...but the resulting image is greyscale. In CaLIGHTs, the pixel values have already been right shifted so they typically range from 0 to 65535. In order to avoid clamping at 16 bit, CaLIGHTs divides the summed value by 4. The net result is a smaller color image with very good noise reduction.

I wrote my own focusing routine for my QHY camera which uses the camera's 8 bit video mode. If I 2:2 bin I get a nice greyscale image with small stars. I wanted to focus using the RGGB raw pixels at full resolution but I found that the bayer matrix on the imaging chip results in a checkboard pattern when you zoom in. My solution was to convert the RGGB values into pseudo luminance values using the whitebalance parameters for the camera. I multiplied the Red pixel values by 2.0 by changing the red parameter from 16 to 32. I multiplied the blue pixel values by 1.5 by changing the blue parameter from 16 to 24. The end result was that the checkboard pattern was highly attenuated and the stars were twice as large. I think this improves my focusing.

Peter