[Theme] Night sky shots

[Øivind Tøien]

I am glad if this can be of use to someone.
MFloyd, that is a very nice animation showing  how the mask works in the link you posted.
Let me add to that, how to make the mask: http://www.deepskywatch.com/Articles/make-bahtinov-mask.html

[Akira]

Christian and Øivind, thanks for the additional info!

[armando_m]

Thanks Amando and Akira for the the kind comments.
Actually earth cannot cast a shade on Venus if that is what you mean as it is always closer to the sun.    The shape is rather caused by some degree of backlighting, just as with crescent moon. On Venus that seems to be reflected more than when light is reflected back at a 90° angle, opposed what is the case with the moon. I was surprised reading about this recently.
 Yes this is mostly done for own satisfaction. Planetary imaging is a specialty by itself. A more professional approach would be to use a high magnification refractor on a small sensor, and use video to capture as many frames as possible. Then one would use a program like Registax to automatically select the best frames and perform resolution stacking.

oops! An incorrect comment from the beginning
Backlight indeed, I guess from out point of view we are seeing the divide from night and day on the planet

[Øivind Tøien]

Nice illustration of the geometry.

[Øivind Tøien]

Yesterday night was likely optimal for a conjunction between comet 41P/Tuttle-Giacobini-Kresak, the Owl Nebua (M97) and the Cigar Nebula (M108), which also is close to Merak, one of the corner stars in the Big Dipper/Carl's Wagon. It looked really good here in Fairbanks to begin with, nice and clear, the  conjunction close to perfect, although with some suspicious lingering purple sky glow. I got in a little over 1/2 hour before a solar storm kicked in and prevented further efficient captures. (I should have started earlier, but setup took quite some time at -25°C and deep snow near my cabin.)

Here is the result of stacking 98% of the frames in Deep Sky Stacker (DSS) on the stars after removing the frames with aurora manually. Tracking was excellent on my Skytracker with my Nikon 300mm f/4 PF wide open and going down to only 30 sec exposure per frame for a total exposure of 30.5 min. The comet is the diffuse blue-green object; no tail visible at this time. The elongated shape of the core is due to its movement relative to the stars during the time of the exposures. Thus it would need separate registering from the stars :
#1


Nikon D7100 with 300mm f/4 PF on Skytracker at f/4, ISO 1600, ca. 61 frames at 30 sec.

(It is interesting that I captured another comet,  C/2014 S2, at almost the same position last spring - page 4 in this thread with my browser.)
....

Then the aurora showed up...
#2

(All of these Nikon D5100 with 12-24 mm at f/4.5 25 sec ISO 800, daylight WB.)


No chance for comet captures even in the target area that was straight above:
#3



Blasted by the aurora again...
#4



#5

[BW]

Good captures Øyvind! Keep them coming and be sure to explain the procedure the way you do now. Then I could use this thread as reference, if I against all odds should take my skytracker out of the cupboard

[Øivind Tøien]

Thanks Børge for the kind words. I wrote an explanation of the procedure on the second page in this thread. I do not think too much has changed since then except for addition of a red dot sight for finding my target and the Bahtinov mask. I have still much to learn with respect to the processing - alternative methods for stacking and stretching the tones; there are some new free tools out that I have not got around to fully test yet. The Astro forum at DPreview is pretty good for learning and with much lower noise levels than some other forums there.

[BW]

Thanks for the tip Øyvind!

[Øivind Tøien]

There was a rift in time and space last night, or at least in earth's magnetic field:
#1


NIKON D7100, f/3.2 @ 10.5 mm - it was pretty intense, only 4s exposure at ISO 1600.


This was supposed to be yet another comet attempt... Two nights before I managed to capture  comet 41P/Tuttle-Giacobini-Kresak again and do a separate registering on the stars and the comet. This comet is going to get brighter in the coming weeks, and it will be interesting to see what happens to it as it approaches the sun. Currently it does not have a tail.  I thought I had gotten in a total 3 hours of exposure with very calm aurora free sky just to find that the last 1.5 hours was with the Bahtinov mask attached   after my midway focus check. 
#2


Nikon D7100 with 300mm f/4 PF on Skytracker at f/4, ISO 1600, ca. 80 frames at 60 sec, two separate sigma clipped stacks combined, one on stars and one on the bright core of the comet.


In the remaining time before daylight started showing up I made a new attempt at tracking with the 300 mm f/4 PF + TC-14E, using the Whirlpool Galaxy (M51) as a target, and got reasonably good tracking - out of 50 60 sec. exposures I got about 33 (70%) usable frames. Results were not any better than than previous attempt without TC, but the time was too short and background light pollution about 1 EV higher. Considering that this tracker is not designed for use with lenses longer than about 100mm this is not bad at all:
#3


Nikon D7100 with 300mm f/4 PF and TC-14E (420mm) on Skytracker at f/6.3, ISO 1600, ca. 33 frames at 60 sec, stacked in DSS with 2x drizzle.

[Akira]

To me, the beautiful turquoise/emerald green color of the comet has the stronger magnetism than that inducing aurora!

[Øivind Tøien]

I tend to agree, now if we could just get a nice bluish-white tail attached to it!

[armando_m]

Wonderful images Oivind

I have missed your latest update, I'm planning to go shooting  tonight, and will try m51, will see how it goes

[Jakov Minić]

Extraordinary skills, Øivind! I admire your images!

[BW]

Spectacular shots Eivind! I took a liking to the emerald comet too. I also notice that spring has arrived I see now that it was an older posting

[armando_m]

Last night I tried M101 , obviously beyond my current abilities, at least I was able to locate it

Disappointing that I got 6 good frames out of 64   

2nd image
85mm f2.5 30 frames 30" each ISO 1600
Saturn, lagoon nebula among the most noticeable objects in this immensity of stellar objects