The Question Mark Nebula

Here’s my latest image of the region near NGC7822. This was a longer than normal mosaic project that took me quite a bit longer to process due to having to relearn how to do mosaics in Pixinsight, and the large file sizes of the ASI6200 - about 12GB total of subframes. These large sizes caused PI to crash a few times and even required me to restart the computer due to a memory issue. I think all the trouble to get this image was worth it in the end though.

Framing the mosaic was super easy with Voyager’s dashboard :tada: . It ran the show for four nights, happily capturing all the subframes I needed.

Because this is a mosaic, the final image is pretty big, at around 8100x11000, so there’s a lot of extra detail to be seen by zooming in. Be sure to check out the astrobin link below where I show various crops of this region.


This region near the border of Cassiopeia and Cepheus begs a question. What it is, I’m not sure, but thought it was an interesting combination of nebulosity. At its core is NGC7822, a young star forming region that lies some 2900 light years away. This region has one of the hottest known close stars with a surface temperature of 45000K and luminosity at around 100000 times that of our Sun.

Near the bottom, punctuating this region, is Sh2-170, a small emission nebula often labeled as the Little Rosette Nebula. It lies some 7500 light years away, more distant than the foreground star forming region of NGC7822.

Scope: Astro-Physics 92mm Stowaway @f/5.3
Reducer: Astro-Physics 0.8x telecompressor
Camera: ASI6200MM Pro
Guide Camera: ASI174MM Mini
Mount: Mach1 GTO

SII: 29x15min
Ha: 27x15min
OIII: 36x5min total
Software: Voyager, PHD2, APCC, Pixinsight
23 hrs total exposure

Astrobin for more details:


Fantastic Gabe! I had never seen these objects framed in this way. Great result :+1:


Wondeful result. Congratulations Gabe.

All the best

Really well done, Gabe. How are you liking that camera? I was tempted to get one but have been holding out for an APS-C camera. The larger sensor and file size of the 6200 seem to come with so many challenges/inconveniences (need for wide image circle, big filters, supercharged processing computer, etc), I just don’t know if I am up for them.

Keep up the great work!



Thanks all for the compliments!

@Starship, I really like this camera. The pixel scale is good enough (with this scope, it’s 1.53"/px), that you can crop out the edges of the field if you don’t like the starshapes. Aside from the full frame sensor and good scale, the noise is very small. Here’s a comparison I made of it vs. the QHY16200A, which I had previously used.

Thanks for the video. The difference is pretty remarkable. To what do you attribute the difference: high sensitivity, low noise, or both?

Sorry, I don’t mean to take away from your thread. I can PM you, if you prefer.


No worries. I think it’s a combination of both. This sensor is a BSI sensor, which improves sensitivity, and has inherently lower read noise and dark current. You don’t have to cool it down as much as the CCDs I’ve had in the past. I’m quite happy at -10C cooling.

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What a beauty!
I really like your HSO combination technique, great work with a big ammount of good quality data!

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Beautiful shot of NGC 7822. I also have been impressed by the sensitivity of the IMX455 chip. I am at 1.28"/px 2x2 with a 6" refractor. I have been wary about shooting at 1x1 for the reasons you listed. Congratulations on a awesome shot.


Really nice Gabe! Beutiful render of this particular nebula.

I am scared of the IMX455, I think the optics that I own won’t use the full potential of the huge FOV and pixel size. I also think my processing computer is not up to the task of dealing with this amount of information… Nice to see that you are taking advantage of this fantastic combo, big FOV and great resolution. Congrats.