I tried long exposures with no gain and no darks using the Rising Tech Sony IMX224 eyepiece/guider cam to image the Owl Nebula, recently. I was using it like I would one of my Canon DSLR cameras with long exposures at low ISO when shooting in bad LP conditions.
Hot pixels were worse than I thought, so I had to do some aggressive noise reduction. Next time, I will definitely use darks based on this experience. The camera has low read noise, but not low hot pixels with exposures this long.
The Crab with an 85mm objective. Scopes of this size are not normally known to produce good images of M1, the Crab. But, I tried anyway since I am still learning the ropes with the IMX224.
Taken from the middle of a metro area in a Bortle Red zone. 8 sec seems to give good results with the LP levels at this location. More exposure just gets more LP and very little more, if any, faint target material.
Above is the gussied-up and gaudy version. Below is the not-so-gaudy version with less saturation and curves boost.
I also left more green behind, since the Crab has some green parts. It shows that better but also shows more of the LP that I had to cut through to get the shot.
Here is a roundup of objects I was able to see during my most recent Electronically Assisted Astronomy (EAA) observing session. These were taken in a Bortle Red zone and under a nearly full moon on Dec 1, 2017.
Who knew just a few years ago that I would be shooting 8 second sub-images and building up images that rival my best efforts with a DSLR camera and 180 second sub-images. Now, all I have to do is save up for one of these new breed of Sony CMOS cameras with lots more mega-pixels that can match the resolutions I get with my Canon cameras. They are not too costly anymore and the results speak for themselves.
BTW, this was shot with the bright moon nearby. I got him, too, though! 🙂
By luck I framed this one with M31 and the Cassiopeia region and got all the good nebulae that were in the area to boot. You can see the Heart and Soul Nebulae, the PacMan Nebula, emission nebula NGC 7822, and other smaller nebulae like the one near Gamma Cass. The Double Cluster is there along with lots of other open clusters.
It is not the best lens and I did do some distortion correction in PS. It was a little difficult to process since this was the first time I used the Astronomik CLS filter. Before, I had one light pollution filter and two cameras, so I finally got another one so they both have one. All I need now is a small mount for light loads like the setup I used here and I could get two cameras going at the same time. Yeah, buddy! 🙂
I salvaged what I could of this one. I had problems with the acquisition of the sub-images and it was mainly caused by dew. I had to wipe the lens down several times and every time I did, the focus or focal length changed. I was able to fix it by installing a dew heater strip on the lens, but that was not until the next set.
I gave up on these after an hour of fighting it. I should have installed the heater before shooting, but I was in a rush to get data and there was not any dew problems in the beginning.
But, at least I got something out of it. Anyway, here’s a portrait orientation version of the data with North at the top:
And here is a close crop of the central region:
Instead of my usual dead-end road site, I drove a few more miles west of there to a new site I’ve been wanting to try out. It is only 50 minutes total trip time and you get a borderline Bortle 3/4 site with a really dark southern and southwestern horizon.
The west is pretty dark, too, but there are various small light domes from the west-northwest to the north. The northeast has a larger light dome from a metro area in that direction and the east has some smaller ones here and there. There is a line of trees from the southeast to the northeast which blocks the LP from those areas, which is good. But, it would not be the best place to shoot early morning comets, for instance, since you can’t see the eastern horizon very well because of those trees.
It is definitely dark there. Rated a 0.22 radiance level on a light pollution map. At one point, I might have glimpsed M33 naked eye, but I was not sure. If it would have been more towards the west I’m pretty sure I could have seen it. Moonrise was at midnight, so I quit early and did not get a chance to try for M33 when it was in that area of the sky. Maybe next time! 😉
Here is a one exposure image taken in the middle of a Bortle Red Zone with 2 light pollution filters in place to help with all the LP. I managed to get quite a bit of nebulosity with 5 minute sub-images at F/2.8 and ISO 200 on my older, modified Canon XS camera.
What helped was the sky conditions, which were very transparent and clear. I am glad I did not waste one of the few great nights of the year.
The above image is just a tease, btw. I have a number of these subs just waiting to get calibrated, stacked and processed. I will probably just tack the finished product onto this thread when I am done.
Edit: Done!
There you go. Tacked on as promised. lol I accumulated almost 2 hours worth of data and considering the location, it did not come out too bad.
Here’s one I haven’t shot in a while. I was using it as a test to see how bad the LP would be. Not long after this was taken, Comet Lovejoy was in the same general area LP-wise, so I had a pretty good idea how much comet I might get.
On the night following the encounter between M108, Comet 41P and the Owl Nebula, the comet was still in the field of view of my setup, so I went back for seconds. I just couldn’t pass up the opportunity to shoot a comet conjunction again!
I went with 3 minutes sub-images at ISO 200, since the 1 minute ISO 800 subs were too cooked by the LP for my taste. Unfortunately, the sky was not as transparent as the previous night and that half-stop of underexposure was needed to get around that. The trade-off was I didn’t get as much of the comet’s coma. Oh, well.
Also, at that exposure length, the comet’s pseudo-nucleus trailed a bit, since it is moving with respect to the Earth and stars and slowly picking up speed as time goes on, to boot. It was not enough to notice if I carefully over-exposed it a bit in processing to make it fatter, luckily. Check the star streaks version, which I did not overexpose, and you can see how far the comet moved in 3 minutes:
A Televue TV-85 w/0.8x focal reducer/field flattener, a Canon T3, my laptop running EQMOD, driving my Atlas EQ-G mount and PHD2 Guiding with an Orion StarShoot guider/Orion Ultra-Mini guidescope was some of the equipment used.