Sunday, December 27, 2015

A new DSLR. Now what?

I received a DSLR for Christmas. This is a place to express my ignorance on how to use it for astrophotography! If you have answers, please comment!

The Camera
I have a Canon EOS Rebel T5i (also known as the 700D). This is a crop-frame 18MP camera that came with an 18-55 mm zoom lens. It currently has an 8GB SD card.

There's targets which I photographed adequately and others that I attempted to photograph poorly with the iPhone that should be within reach of this camera: 1) Moon, 2) Messier objects, 3) Planets, 4) Milky Way, 5) Constellations, 6) Star Trails, 7) ISS/Satellites/Flares

1) The Moon
With the current lens fully zoomed, you can make out general surface features. This wide field of view should allow capture of halos and the glow of a moon peeking through clouds.
  • Do the higher-quality capture options actually mean more MP saved and more detail? or is it more a factor of compression ratio?  Just how much more hand-held detail will I see with a "raw" photo versus "L1"
  • How do I "flatten" the exposure so that I don't have to choose between clouds and surface features? Can the T5i do HDR?
For a full lunar disk, I'll need a T-Ring and T-Adapter to attach the T5i to my NexStar 8" SCT for prime-focus photography. I've located the Celestron OEM pieces to purchase.
  • How do I calculate the field of view I'll get? I suspect that the full lunar disc will exceed the crop-frame size of the camera.
    • Update: A link from David Blanchflower (@DavidBflower) and some basic trig helped me calculate field of view for my sensor attached to my Celestron 8" SCT with 2036 mm focal length at 0.63°x0.42°, enough for quarter moon but not full. 
  • Will my current focal reducer do the trick? Is the T-adapter even threaded to accommodate a focal reducer (or other filters)?
For lunar close-ups, I could crop photos, or figure how to magnify. This requires another adapter, the "Tele-extender". I know little about this, other than it should allow an eyepiece between the T-adapter and the telescope.
  • Will any of my eyepieces work in this configuration?
  • Is there a better way to magnify?
With the brightness of the full moon, very short exposure times should be possible, so tracking should not be needed.

2) Messier Objects/Deep Sky
To capture star clusters and galaxies, I need more magnification than my current zoom lens, but I think many popular targets require larger field of view than the full moon. This list tells me (?) that the Andromeda Galaxy, M31, is about 1 x 3 degrees, which is 2 x 6 full moons. The Great Orion Nebula shows at about 1 x 1.5 degrees, or 2 x 3 full moons.
  • How do I expand the field of view of my telescope/prime focus combination further?
For dim objects such as these, gathering lots of light will be necessary. The rough "rule of 500" implies that with the 2032 mm focal length of my 8" SCT, I should only be able to capture about 1/4 second exposure before drifting stars become evident. Clearly this won't provide the rich colors and clear images I'm looking for. So I guess I'll have to finally figure out if the old telescope can be properly aligned for tracking!
  • Will stacking a large number of 1/4 second exposures still give me a reasonable result as compared to stacking less, longer exposures?
I also need to learn about "dark frames", how to take them and how to use them. And, will Registax be sufficient software for me, or is there other free/paid software I need to look into.

3) Planets
My results with the iPhone were okay for an iPhone. I could recognize that Jupiter had bands and the red spot was vaguely discernible, but no shadows from Jupiter's moons were visible. Saturn definitely had rings, but no ring divisions were to be seen.

With prime focus, without a focal reducer, I'll definitely have more pixels to play with. A 2x barlow should (?) increase the image size even more. At this point, I suspect that taking video of these bright objects should yield lots of clear, stackable frames.
  • How do I increase magnification even more with prime-focus photography?
  • Is video the best bet? Or should I be taking individual frames?
    • Update: Video from the camera will be taken at lower-than-full resolution, so still images are better. Using an intervalometer to capture many short exposures will provide raw material for stacking.
4) Milky Way
Using a tripod and the current lens zoomed out to 18mm, I should be able to expose for up to 30 seconds before significant star trails form. For long exposures on the iPhone, I use the NightCap Pro app, which combined many shorter exposures into one long exposure. Now I've got to figure out the proper ISO and aperture to set in order to not over or under-expose in these long exposure pictures.
  • How do I figure out the proper settings to use for a Milky Way exposure?
    • Update: This tutorial gives some great detail on tools and techniques.
  • How much do I reduce the exposure to compensate for light pollution in my cul-de-sac?
  • Is a light pollution filter necessary, or can I wipe most of it out in post-processing?
    • Update: Light pollution can be handled with a special filter that selectively removes sodium and mercury spectra. Also can be minimized in post-processing with some artistic adjustment.
  • How do I take a dark frame for noise reduction?
    • Update: Lens cap and same exposure settings!
  • When stacking multiple frames, how do you align both a fixed horizon and a moving milky way in multiple exposures?
  • What should I look for in a wider-field lens?
    • Update: I calculated the field of view of the 18-55mm lens. At 18mm, I see 63.5°x45.0° while zoomed to 55mm gives 22.9°x15.4°.
5) Constellations
Tripod-mounted shorter exposures should expose larger constellations. I think this will be a more straight-forward trial-and-error process, and one in which I can achieve quick success.

6) Star Trails
As near as I can figure, the camera can be set up to take up to 10 consecutive exposures at a maximum 30-second exposure each. That's only 5 minutes.
  • How do I keep the shutter open longer in "bulb" mode? What accessory do I need to hold the button down?
    • Update: An intervalometer is the tool I need now have!
  • Will a very long single exposure flood the frame with noise?
  • When stacking multiple exposures, will there be a "pause" in between exposures with a break in each star trail?
    • Update: Yes, there will be a pause. Not sure how to get rid of it.
7) ISS/Satellite Flares
I've been quite successful taking long exposures of the ISS and satellite flares with the iPhone. I'm debating any advantages of DSLR images instead. I'll be facing some of the same challenges with the Star Trails images: how to set exposure, keep the shutter open long enough, and stack multiple frames for one continuous trail.

Also, the field of view of the iPhone is wider than I'll get with this lens.
  • Any recommendations on wide-angle or fish-eye lens specs?
I have a lot to learn, and am looking forward to successes, and dreading the stupid mistakes I'm sure I'll make. But I love to learn, and this will present some interesting challenges.

Please comment below, or tweet at @BeckePhysics with any suggestions or recommendations! I appreciate your help.

Saturday, June 27, 2015

Getting to the Space Station

NASA provides several opportunities for educator professional development. I had the opportunity in June of 2015 to attend the WRATS workshop, Wallops Rocket Academy for Teachers and Students, at NASA Wallops Flight Facility on the eastern shore of Virginia.

On the last day of the program, we got a tour of the Horizontal Assembly Building , where the Antares rocket is assembled and prepared for flight. This rocket was developed by Orbital/ATK, one of the private corporations that has contracted to supply the International Space Station.

The main building is a single hangar big enough to simultaneously prepare two Antares for launch. At the time of my visit, they were preparing for a March launch, the first since the mishap on 10/28/2014. 

A tour from top to bottom:

The Payload Fairings come together to enclose the Cygnus supply vehicle. They are constructed of a thin carbon fiber honeycomb. As soon as the vehicle escapes the atmosphere, charges are fired to split the fairings and levers at the bottom work to wedge the fairings apart, exposing Cygnus.

 The Cygnus sits atop a second stage, which is fueled with solid propellant, similar to the Space Shuttle's boosters. The second stage is bolted to the first stage, but is released when a ring of explosives is fired to cut the two apart. This ring is seen in gold at the base of the black cone to the right in the second picture below.

The second stage attaches with a connecting ring (center, below the American flag) to the first stage.

 The first stage, also known as the "core" contains two large tanks, one for liquid oxygen and the other for kerosene. The core remains empty until the assembly reaches the launch pad, where it is filled and pressurized.


The engines (not yet at the assembly building) are attached to the bottom of the core within this final cylinder. The diagram below shows a cut-away view of the assembled Antares.

Once assembled, the Antares launch vehicle is lifted onto this structure and wheeled out to the launch pad, by a driver walking by its side steering with a joystick, where it is raised to a vertical position.

It was a once in a lifetime opportunity to get a private tour of this operation with the fellow members of the WRATS 2015 workshop.

Incidentally, the Antares launch pad is marked with an "International Space Station on-ramp" sign.

Tuesday, March 10, 2015

iPhone Astrophotography - Why the iPhone needs a users manual

So, (and forgive me for starting my sentence with "so") imaging Jupiter last night was a bust.

I did manage to get the electronic controls working on my telescope, which was a good thing.  Although wobbly in the mount, there is an electronic altitude-azimuth remote control with several different speeds at the push of a button.  I managed to tighten the mount the other day and get the controls working for the most part.

When I went to image Jupiter, I got a nice view of the moons, but a very over-exposed disc of Jupiter itself. Here's a single image taken with the iPhone:

I've been encouraged to use a stacking program to combine images for a better view of the disc, so I captured some iPhone video.

I downloaded RegiStax (a very quick and easy download), and went to upload the iPhone video, but RegiStax only accepts .avi, .mpg and .mp4. The iPhone records in .mov.

I went to to convert the videos to .avi and then uploaded to RegiStax.  Without looking at a users manual, I stepped through the program, but just wound up with an overexposed single image of Jupiter and the moons:

 It's been very frustrating.  I've been trying to find a way to trick the iPhone to have less exposure. I've tried pointing it at the moon and locking the focus/brightness, then swinging over to Jupiter, but last night the moon was not to rise till much later.

Gee.  If only there was a way.

Then, I thought that there may be a way to control the brightness. I played around this afternoon and stumbled on the following:

If you lock the exposure/focus, you will notice a sun icon to the right. Simply sliding your finger vertically on the screen will incrementally brighten and dim the exposure!

Now why didn't anybody tell me that?!

So next time I have clear skies (which doesn't look like it'll be for a few days), I'll try "dialing down" the brightness on Jupiter before taking video and then stack that. Wish me luck!

(Oh, and if anyone can tell me if it's possible to record in .avi instead of .mov, that'll help a lot!)

Clear skies!

Sunday, March 8, 2015

iPhone Astrophotography - Background

I've begun dabbling in astrophotography using the iPhone.

Inspired by the work of Andrew Symes (@FailedProtostar on Twitter), who has achieved awesome results and whose work has been featured recently in The Atlantic, I have taken my old telescope out of storage and have started to play around.


My equipment consists of the following:

  • An iPhone 5. The only camera I own.
  • A Meade Telescopes DS-127, which I bought nearly 15 years ago and which has spent most of its life in storage. The telescope mount is wobbly and difficult to aim consistently, so I need lots of patience. There is no automatic tracking, so I have to point manually and hope for the best.

  • A Celestron FirstScope ($50) that I bought for my dautghters (but really for me). It is easily portable for travelling and use in Camping. Fits in a small shoulder bag.

  • A Vista Explorer Tripod ($35). I bought this and a "Charger City" smartphone adapter to allow for long exposures on the iPhone. This works well when shooting ISS passes or Iridium Flares. This is also how I'd take some steady pictures through the telescope eyepiece, but I'd have to adjust the tripod each time I adjusted the telescope.  Not an optimal solution.  Note: I also use a portable battery pack since the battery on my iPhone quickly discharges in cold weather. The battery pack minimizes that.

  •  Orion SteadyPix Pro. This adapter holds the iPhone (in the case) and aligns the camera with the telescope eyepiece. Unfortunately, it needs a long eyepiece to grab on to, so it only work with my lowest magnification lens.  Great for taking pictures of the moon, but not enough magnification for imaging Jupiter.
  • Celestron Astromaster Accessory Kit. ($46) This provided a moon filter and a Barlow Lens, among other things. The Barlow lens provides enough hardware for the SteadyPix to latch onto, so I should, theoretically, be able to get higher-magnification images of Jupiter.

Results so far:

I've had mixed results ... but I'm working on it!

To capture passes of the International Space Station and Iridium Flares, I use the Sputnik! app on the iPhone to tell me when and where to look.  Then I put the iPhone on the tripod and use the NightCapPro app with the night, light boost and light trails settings to get a long exposure.
Iridium Flare and Orion 2/15/15
International Space Station and Cassiopea over Williamsburg 2/22/15

Initially, I was capturing the moon by holding the iPhone up to the eyepiece of both telescopes. I've since begun using the SteadyPix to attach the iPhone and align the camera for more consistent results.

Taken 1/30/15 Handheld through Celestron FirstScope

Taken 1/24 Handheld through Celestron FirstScope
4:30 a.m. 2/11/15 using SteadyPix Pro and Meade DS-127
Capturing Jupiter is my next challenge.  I've found that taking video and capturing single images has given me my best results so far.  Interestingly, the bands of Jupiter's clouds are most pronounced right at the moment that the disc is about to pass out of the field of view of the telescope. When it is centered, it is generally over-exposed.  I'm working on getting the right exposure and magnification, using filters and different eyepieces.
Single frame from iPhone video 2/2/15. Jupiter just about to pass out of field of view

3/2/15 zoomed and cropped screengrab from video
So that's where I'm starting. I'll continue future posts in this blog with the results of continued viewing sessions.  If you want to get a first look at my latest sightings, follow me on Twitter at @BeckePhysics.

Clear skies!