Prime Focus Crescent Moon Frustration

I made another moon attempt at prime focus last week and the results are frustrating. I just can't seem to get the entire disk in focus at the same time, and although the moon is much higher resolution at prime focus, my best clarity still came from digiscoping with my iPhone through the eyepiece.

So I either need a camera with live view so I can focus on a larger display (or a laptop) rather than through the tiny viewfinder, or an iPhone mount / adapter for the eyepiece. Or maybe video is just the way to go, and stacking 20 frames won't cut it at higher resolutions. Since my DSLR doesn't do video, this is still a problem.

Canon Rebel XT (350D) at prime focus on Meade 285

Crescent moon at prime focus, 20 frames stacked in Registax

Comet ISON with Beta Virginis November 7, 2013

I've been reading a lot about Comet ISON (C/2012 S1) already visible to amateur astronomers in the early morning sky over the Eastern horizon. At magnitude 7.50 on the morning of November 7, 2013 I figured I could try to pick it up with the DSLR and 300mm lens. After all, I've picked up magnitude 9 or 10 stars through stacking in DeepSkyStacker (DSS), and since a comet is more compact than a galaxy (whose visual magnitude is spread out over a greater area) I knew I could grab it.

11/7/2013 at 6:00am ET Stack of 62 subs, 32 darks, 0 bias, ISO 1600, 300mm, f/5.6, 1.3 sec

It was very easy to find Comet ISON in the sky, below Mars and right on top of Beta Virginis (β Vir), one of the brighter stars in Virgo. They were actually about 24 arcminutes apart (less than 1°), and both easily fit into my field of view - which was good because I couldn't even see ISON in my view finder. ISON was relatively high in the sky, about 28° alt, which was different for me because the only two comets I've photographed previously have been about 10° above the horizon at twilight.

Stack of 62 subs, 32 darks, 0 bias, ISO 1600, 300mm, f/5.6, 1.3 sec

While I was stacking these, I had something happen that's never happened before. I got an error in DSS that said "only one frame (out of 62) will be stacked. You should check/change the star detection threshold to detect more stars and help DeepSkyStacker find a transformation between the reference frame and the others."

I had the star detection threshold on the lowest setting (2%) which tells DSS to treat anything that looks like a star as a tracking/alignment option. In photos of the Milky Way, having DSS on 2% would produce tens of thousands of traceable stars (and take forever to stack). However, in my light frames, DSS was only picking up 6-9 stars.

To solve this problem, I went back to my RAW files in Adobe Camera RAW, and lightened the frames up so the stars that were in the frame would be brighter and easier for DSS to pick up. I saved them as TIF files and loaded them into DSS. Then I got an error saying my light and dark frames were different file types, so I had to go back and save my dark RAW files as TIF files just to make them match.

In the end it worked, and I'm pleased I was able to troubleshoot this little issue on my own while still producing an image of Comet ISON.

Warp Speed or Star Smoke Trails

Warp speed! This is a 6 second exposure of the Hyades cluster. During the exposure I zoomed in from 75mm to 300mm, making it look like we're flying toward the stars at high speed, or maybe they're flying with little smoke trails behind them.

Hyades cluster from 75mm to 300mm in single exposure

Orion's belt from 75mm to 300mm in single exposure

Color Comparison: Betelgeuse, Aldebaran, and Rigel

I took blurry photos of some popular stars to spread their light over more pixels to give a better representation of their color. Hotter stars are white and blue, while cooler stars are red, orange, and yellow. I looked up the surface temperatures of each on Wikipedia. Obviously the image is a composite since these stars aren't right next to each other in the sky. I used the same camera settings for each, so Aldebaran is slightly dimmer.

300mm, intentionally out of focus, enlarged in Photoshop

Rigel is my favorite star by the way! Comparing the color of Betelgeuse and Rigel was the subject of one of my very first blog posts: Orion constellation with star labels with my point and shoot camera back in 2012.

November Morning Sky ft. Orion and the Seven Sisters

I woke up to take the dog out at 5:00am this morning, and saw that the sky was clear. Sirius and Jupiter were blazing in the crisp, alarmingly cool air. It's been raining for the past few days, so I was super excited to get outside and get some photos.

I started on the balcony with a wide angle shot of the Orion neighborhood (from Sirius to the Pleiades). I tried a bunch of different settings to see if I could stumble upon something cool, or find a way to increase the number of stars without adding to the light pollution. Here's the final result...

Final result with adjustments in Adobe Camera RAW

Below is the same photo pre-adjustments in Adobe Camera RAW. Notice the prevalence of sky glow and washed out stars. At least the stars were sharp, unlike the shot I took with the aperture wide open.Check out the results from a variety of settings...

Same photo as above, f/4.5, 15 sec, ISO 800, 18mm unprocessed

Screen shot of Adobe Camera RAW (check the settings on the right if you want to do something similar)

Trying the same scene with different settings, f/3.5, 15 sec, ISO 800, 18mm (wide open aperture isn't as sharp)

Trying the same scene with different settings, f/11, 15 sec, ISO 1600, 18mm (very sharp but not much light coming in)