Thursday, August 27, 2015

#13 - Thursday, August 27, 2015 - Don't image with the moon out

I decided to shelf Andromeda for now and try the Whirlpool Galaxy instead.  At first I wasn’t sure it was on the right spot, which it really needed to be because I could barely see it through the telescope, but sure enough, it showed up in a 30 second exposure!  Super exciting to see it. I played around with the telescope settings a bit, and decided to try much higher anti-backlash values.  At normal speeds, this causes a massive jump when I move the telescope, but at tracking speed, I thought this wouldn’t happen.  I think I got more of the stable pictures, but it wasn’t by much.  I took about 110 before the telescope got too dewy, which was early that night, only about 11:30 PM as opposed to the usual 1:30 AM or so.  I can’t remember how many DSS took, but not enough apparently, because I couldn’t even see it in the stacked image, even though I could just barely see it in the individual images.  This is because the moon was pretty full, bright, and high in the southern sky (which is what drove me to do the Whirlpool Galaxy in the first place, since it was one of the few objects in the northern sky).  Better luck next time.  I’ll just have to add the Moon as another discriminator against photo trips.  It’s fine for visual observing trips with my friends, since it looks so fantastic in the telescope view.

Single frame of M51 Whirlpool Galaxy taken on a moonlit night.
Tracking errors cause the stars to streak.
Nikon D3100 on my C8, 30s, ISO-12800

Monday, August 24, 2015

#12 - Monday, August 24, 2015 - Terrible Tracking

I messed around with different anti-backlash settings, but still couldn’t quite find any that worked well.  [Anti-backlash takes up the slack in the gears whenever they have to change direction by quickly spinning them at the end of a movement.]  I did also try moving the telescope in the same direction it was tracking after getting Andromeda aligned in the center and syncing on it in order to pick up the slack in the gears.  It didn’t seem to help, though. I think this is a real issue, though, but only for the first few photos – when I’m taking the test photos after moving it, the first two or three are really bad, but then it settles, so I think that’s how long it takes to pick up the play in the gears at tracking speed, about a minute.  Of some 217 photos I took, I accepted 102, and then DSS only accepted 62 of them.  Also, they were all accidentally taken in JPEG.  I went ahead and took darks and biases in JPEG too, but the dark subtraction doesn’t really work for compressed files, it needs to be pixel-by-pixel.  

[Author's Note: Don't ever take astro images in JPEG format! You literally lose data.  And then you can't stack them.  (Well, technically you can, but it turns out awful.)]

Saturday, August 22, 2015

#11 - Saturday, August 22, 2015

This was exclusively a photo trip.  I even left the camera on the telescope for alignment, so that GoTo would be programmed with the extra weight of the camera affecting how it moves.  (I can see quite well through the viewfinder, actually.)  I took about 150 photos of Andromeda.  For the first 75 or so, it slowly drifted up the frame, so I re-synced it after re-aligning it.  It didn’t rise as much this time.  
M31 Andromeda Galaxy
Nikon D3100 on my C8, 31x30s, ISO-12800

[Mo' data is mo' betta!  Except that M31 is far too large to fit the field-of-view (FOV) of my 8-inch.  But check out those dust lanes!  Also, I didn't know at the time that you had to move the Saturation slider up to 20-25% in DeepSkyStacker in order to get the color back.]

Friday, August 21, 2015

#10 - Friday, August 21, 2015 - Andromeda Woes

I brought two of my other friends along, Jessica and Ethan.  This was their first time stargazing, and they were amazed!  We looked at Saturn first of course, and then the Moon (1/2 waxing gibbous), as well as Neptune, the Butterfly Cluster, the Double Cluster,  the Andromeda Galaxy (which was particularly bright that evening), double star Mizar & Alcor, Arcturus, and M3, a globular cluster that appeared as a smudge.  They took off about midnight, and then Anton and I set to work on imaging Andromeda.
I took some 100 pictures (can’t remember the exact number), and 53 were stable enough to use.  DeepSkyStacker (DSS) accepted only 29 of those.  And the stacked image isn’t much to look at.
M31 Andromeda Galaxy
Nikon D3100, 29x30s, ISO-12800

More light-information is required, so more pictures.  [And for goodness sake, a lower ISO!] 

Tuesday, August 18, 2015

#9 - Tuesday, August 18, 2015

Anton & I looked at Saturn – it’s tilted 24 degrees towards us at the moment, so we should be able to see the Cassini division. With the high humidity and a low score on the “seeing” conditions rating on ClearDarkSky, there was a lot of shimmer, even under moderate power. But I think I could just make out the division.

M9 – neat-looking globular cluster. Didn’t photograph well for 30-second exposures, but you can see it. I tried stacking, and I took raw format photos, but these images turned out so dim and noisy that I aborted the operation.

M13 Hercules Cluster – Also a great-looking globular cluster. Still pretty dim under 30-second exposure, so I took a series of 30-second exposures, ISO 1600, in the raw format. However, either I need more photos to stack, or I’m not doing something right in DeepSkyStacker, because the stacked photo is very dark and I can barely see anything. It is even darker than the individual images, which leads me to believe I’m doing something wrong. Time to consult some YouTube tutorials.

Anton tried to find an asteroid based on its astronomical coordinates he found online, asteroid (15) Eunomia, in the eastern sky around 12:30 AM. We saw a dot of light, like a dim star, and there wasn’t anything in the telescope’s catalog that was nearby, so it may very well have been an asteroid. Cool!

Thursday, August 13, 2015

#8 - Thursday, August 13, 2015 - First stacked image

I moved the telescope from the asphalt to the grass – we originally moved it to the asphalt to reduce dew, but the grass helped reduce vibration during long exposures. I even waited until I sat down to hit the shutter. Thank goodness for the remote shutter! It’s the only way to take long exposures.

I tried the Lagoon Nebula again, and after trying different exposure times and ISOs, I decided on 30-second exposures and ISO-3200, and took 10 of them to try a post-processing technique called stacking using a software called DeepSkyStacker. Of the 10, only 8 were jitter-free, so this made for a 4-minute total exposure time. The resulting photo didn’t turn out much better than the individual ones, although I didn’t mess with the color or luminance settings. [About a week later, I did; below is the result. Much improved!] Also, my camera automatically subtracts a dark frame from photos with exposures longer than 6 seconds, so I didn’t use any dark frames in the software.
My log entry seems to disagree with the files I have; I count 12 images.
Nikon D3100 on my C8, 12x30s, ISO-3200

The sky rotation is evident in the stacked pictures – you can see the turning in the edges of the photo (before I cropped it). The DeepSkyStacker software is very good at aligning the points of light. Since the light pollution is too bright around here to do longer than 30-second exposures, an equatorial wedge isn’t necessary just yet. At some point though, when I live somewhere darker, I’ll shell out the money for one. [I later corrected this little problem with a light pollution reduction filter.]

Next, I tried the Eagle Nebula. While I can see the stars, I can’t see any gas, or maybe it is just barely visible in the image. Perhaps stacking several images for a 10 or 20 minute total exposure time will reveal it (thought later). Images I see online contain a lot of red, though, which may not show up well on my camera, since I don’t want to have the IR filter removed.

Next, I tried Messier 101, a spiral galaxy in the northern sky. You can just make it out in the image – you can see the core, and just barely see the arms. This one may also be a good candidate for stacking.

Next, I tried M17, the Swan/Omega/Checkmark Nebula. It showed up well on the camera screen, but turned out to be darker when I looked at it on a larger screen. Will need to try this one again as well. Also a good candidate for stacking.
Single frame on M17, using my Nikon D3100 on the C8.
30s, ISO-3200.

I figured out that if I sync the scope to a nearby star, it is more accurate at finding the object – M17 was nearly in the center of the view on goto.

I tried the Eagle Nebula again, a couple 20-seconds and a 1-minute, but no go.

I tried the ET Cluster, NGC 457, and it is a very nice cluster of stars. Will need to try again to try and get a shot without jitter.

Helix Nebula – used Deneb Algedi to sync. Couldn’t find it, or was very dim.

Wild Duck Cluster – synced to Altair. Couple bright stars, lots of noise though. Not much to see in the shots.

Not many meteors tonight. It was supposed to be the peak of the Perseids!

Wednesday, August 12, 2015

#7 - Wednesday, August 12, 2015 - First deep sky object image!

I attached my camera to the telescope and tried getting a photo of my first deep-sky object.  I focused the telescope with the camera attached using a nearby star, and then slewed to where the telescope thought the Lagoon Nebula was, and took a 1-minute exposure using the remote shutter, which worked like a charm.  I got a great photo on the first try! 
My first deep-sky object! (I'm not counting the one of M7). 
Single frame with my Nikon D3100 on the C8, 60s, ISO-3200.

A little bit of jitter, but not bad, and you can see a decent amount of red light, despite the IR filter built into the camera.
[A note here: Modern consumer cameras are built to have as similar of a spectrum to the human eye as they can.  This means that green dominates, and transmission in the red and infrared wavelengths is severely limited, since we can't see IR and are not very sensitive to red.  This is a bane for astrophotography, since many things in the sky glow a brilliant, deep red!]

 I tried taking some longer exposures, but there was too much noise.  I tried Andromeda next, but I couldn’t get a still one in the few tries I made, and all you could see was the bright center, no detail on the arms.  I also tried Bode’s nebula, but it wasn’t where the telescope slewed to.  I also tried the Eagle Nebula, but couldn’t get anything with that either.  Then I tried the Cat’s Eye nebula, and I didn’t think at first that it was in the frame, but later I looked at its apparent size – 0.4 x 0.3 arcmin – and realized that the large blue dot in the photo I took of that area was, in fact, the nebula.
The Cat's Eye Nebula is the blue circle to the left of center.
Nikon D3100 on my C8, 60s, ISO-3200.

Last, I tried the Dumbbell Nebula, and was pleasantly surprised!  It is very dim in the 30-second exposure (the 1-min exposure had some jitter), but you can just make out its pretty blues and greens!
That thing you can juuuuust barely see to the left of center is the Dumbbell Nebula (M27). 
Nikon D3100 on my C8, 30s, ISO-3200

On top of the excitement of getting some images of deep-sky objects, the Perseids were exciting as well.  While we weren’t able to see nearly as many as predicted (40-60 per hour; we saw maybe 5 per hour), it was still really neat to see them, and some long-exposure shots of the sky revealed several more.  I learned from my friend Emily, whom I also brought along that night, that having a slower f/stop allowed me to take longer exposures without star trails, as long as 30 seconds with f/5.6.  This did require a higher ISO, though; I took some with 6400.  This made for some noisy pictures, especially with all the glow from the city.
The Milky Way with a foreground of meteors.
Nikon D3100, 18mm @ f/5, 30s, ISO-6400

Friday, August 7, 2015

#6 - Friday, August 7, 2015

It was relatively cloudy until about midnight, but then all the clouds cleared, and the moon didn’t rise until 1 AM, so we had pretty good darkness.  We went hunting for some deep-sky objects, but could only see dim smudges.  We looked at Bode’s Nebula (well, it's actually a galaxy), the Whirlpool Galaxy, globular cluster M3, and the Andromeda Galaxy.  We looked at the Whirlpool Galaxy and Andromeda with binoculars as well.  We also looked at Neptune, which did have a bluish color to it, but couldn’t quite find Pluto.   We forgot to put the dew shield on, so that ended our night early, plus I really need to clean the corrector plate, both from drying dew spots and my attempt at an isopropyl alcohol solution that I made my own distilled water for that I suspect wasn’t distilled enough. [For all of you who just cringed at the thought of me using semi-distilled water with isopropyl alcohol to clean a multi-coated optic, do not fret - the corrector plate suffered no permanent damage!]  

Next week is the Perseids meteor shower!!  And it will be a moonless night, so I’m going to set up the camera to try and take some long-exposure pictures of some deep-sky objects.  I’m going to order a remote shutter button for my camera when I order the cleaning fluid so I can take more than 30-second exposures on Bulb mode.