M 42

[Stefan B]

We got one more clear night here. And which winter target can be finished in one night? Right, the Orion Nebula:

See https://www.astrobin.com/qe320u/ for technical details.

Actually I collected some 10 sec shots for the core but didn't notice the thin clouds while imaging. But it worked surprisingly well with the 3 min subs only. Amazing how long you can expose with the 571 sensor and what ST's HDR module can do... And cool to see all that dust already after 5 hrs.

With regard to the ringed stars I noticed here that SVD together with my pretty strong usage of Shrink is the reason. If there are slight dark rings around stars after SVD it gets worse with the Tighten preset. Adjusting the Color tame and the Halo extend parameter helps.

Regards
Stefan

[Mike in Rancho]

Wow Stefan, that's awfully nice.

That's really showing off what 5 hours in B4 can do, so glad you got your one clear night! Very rich with the brown dust. Here, I believe I am still on the edge of the jet stream, causing passing clouds, poor seeing, and cool temps, plus an arctic blast for the middle of the country. Friday night I thought I could add to my Horsehead, but it double tricked me!

I was watching the satellite loop and it appeared things were clearing out for the night, with the clouds all starting to pass to my north, heading southeast. That opens up Orion just fine. I took the mount outside and plopped it down on its marks, but looked up and saw clouds to my northwest. Rats! Picked it up and brought the mount back inside. Later I went outside and saw that those clouds never actually came over me and just stayed up on the mountain ridge, so I could have captured more HH just fine.

Now, I do see the little tiny star ringing, but wonder how much is from Shrink. In fact if included in the mask, and a bit of deringing is added, that actually ought to repair anything coming out of SVD.

I like what's going on with the Running Man, though perhaps overall red saturation strikes me as just a bit too high. Not that I don't think the colors look great, they do, but are maybe on the edge of bleeding away detail.

And again overall, I'm wondering if perhaps structural detail should be a little sharper than what is showing.

You are right that your HDR did a great job on the trap. 180s still strikes me as long, but who knows I don't have F5 or B4, so no experience there.

I am seeing a slight split on the diffraction spikes, so as I just did, a recentering of the secondary vanes might sharpen those up. I'm curious too that I am not seeing much of the rainbow coloration along the spikes.

But this is quite inspiring. I am overdue for a newer and cleaner M42 myself.

[Stefan B]

Thanks, Mike!

I was watching the satellite loop and it appeared things were clearing out for the night, with the clouds all starting to pass to my north, heading southeast. That opens up Orion just fine. I took the mount outside and plopped it down on its marks, but looked up and saw clouds to my northwest. Rats! Picked it up and brought the mount back inside. Later I went outside and saw that those clouds never actually came over me and just stayed up on the mountain ridge, so I could have captured more HH just fine.

Oh, I had this situation several times when I was still driving to my imaging spot. Massively frustrating.

Now, I do see the little tiny star ringing, but wonder how much is from Shrink. In fact if included in the mask, and a bit of deringing is added, that actually ought to repair anything coming out of SVD.

The dark rings/halos around some of the smaller stars? Next time I will try to cure that with deringing in Shrink.

I like what's going on with the Running Man, though perhaps overall red saturation strikes me as just a bit too high. Not that I don't think the colors look great, they do, but are maybe on the edge of bleeding away detail.

Yes, maybe. But increasing red saturation helped so much with the look of M 42 itself I was going that route anyway

And again overall, I'm wondering if perhaps structural detail should be a little sharper than what is showing.

Yeah, I have a guess. The scope had been outside for days with freezing temperatures. Basically no problem but before the M 42 session it got very humid and cloudy during the day. So ice crystals were building up on the primary which weren't going anywhere... I only noticed during imaging and didn't want to heat it with a fan since it was already temperature equilibrated. And since my HFR was just fine... but maybe it took away some sharpness and contrast.

In addition the 5 hrs contain quite some time with M 42 being below 25° AND somehow NINA didn't dither for the first three hrs. Only noticed after three hours and had to restart NINA. The other measures like restarting the session or adjusting the dither parameters didn't helped... So not a really smooth session

I am seeing a slight split on the diffraction spikes, so as I just did, a recentering of the secondary vanes might sharpen those up. I'm curious too that I am not seeing much of the rainbow coloration along the spikes.

That had already been better. Maybe a good idea to adjust that. Although I hate fiddling with the scope since I always fear that I make things worse. On the other hand I adjusted the tilt and the friction of my focuser and that went fine... Did you use a tutorial or just adjust the screws and measure the length of each vane?

With the coloration of spikes...I only see that very rarely in my images And if so, usually only with the brightest stars and mostly with rather yellowish or whitish stars. No idea why.

But this is quite inspiring. I am overdue for a newer and cleaner M42 myself.

Would love to see that. With F4 you're probably done faster

Regards
Stefan

[Stefan B]

*Addendum* Regarding star shape / diffraction patterns: In some stars one can also see chromatic aberration. I am pretty sure that's also caused be the low alt. M 42 doesn't rise higher than 35° for me... So maybe not the best data set to judge the optics.

Regards
Stefan

[Mike in Rancho]

Hi Stefan,

Yes you are probably right on all of those factors, and then maybe seeing too, who knows? I do recall having my refractor start to fog over on humid nights if I forgot the dew heater, and subs still came in with results. Just they weren't very good and lacked clarity, and as if there were extra LP.

Well don't go messing with the scope if you don't want to.

The spike split is very slight, and probably only reveals on super bright stars where the spike gets so much longer. Mine finally got pretty annoying though as it was affecting even medium stars and was obvious. I first removed the secondary and rebuilt the spider after straightening all the vanes out with a vise, and used perpendicular lines drawn on some paper to check things. But after reinstallation I still had the same issue.

I'm guessing it was just how I had the vane knobs adjusted for centering the mirror under the focuser. So I decided to throw that out the window, temporarily. It only affect field illumination, and what I really need to do is shim the focuser. Something I have been putting off.

So I just moved the mount by hand to situated the OTA horizontally, and adjusted the knobs while eyeballing the vanes and using a short straight-edge. For one vane that still had some bend in it, I carefully and gently used a needle nose vise grips in just the right places to straighten it. The result wasn't totally perfect, but still significantly better. And Alnitak made for a pretty bright star test.

[dx_ron]

Thanks to the M106 thread, I now have 3(!) followers on astrobin. More importantly, I learned from Stefan's abin profile that we are both biologists in our non-astronomy time. Though I hope to retire soonish to become a full-time cloud-complainer.

[Stefan B]

Mmhh...retirement? For me maybe in 30 years from now

[dx_ron]

If I work another 30 years I could stop with the whole "retirement savings" thing all together and just blow it all on astro gear! Brilliant!