Sunday, September 14, 2014

Rain Soaked Hummingbirds Guarding Feeder

It is definitely the season for Ruby Throated Hummingbirds. While the migration is in full swing along the coast, we are getting progressively more of them in our yard, judging by the number of aerial combats. I watched this resident male perched on the tree about 10 ft from the feeder. Every five minutes or so he would make a pass down to the feeder for a quick sip or simply sit and defend his territory. He always flew back up to this same perch where he would look around for trespassers and flash his colors from a higher vantage. Fluffed up to keep warm in the cool drizzle, he looks very different than usual.

Canon EF 100-400mm f/4.5-5.6L IS - ISO-800, 400mm, f/8, 1/160s, +0.3
Canon EF 100-400mm f/4.5-5.6L IS - ISO-800, 400mm, f/8, 1/160s, +0.3

Several branches up, this female, possibly the mate, remained perched seeming to sleep with her eyes closed most of the time. She neither guarded the feeder nor flew down to feed as frequently.

Canon EF 100-400mm f/4.5-5.6L IS - ISO-800, 400mm, f/8, 1/320s, +0.3
I took these shots with a tripod setup in the living room, pointed out through the open back door, from about 20ft away. The poor lighting made it hard to get images with crisp details due to slow shutter speed. My attempts at using a flash caused unnatural iridescent sheen on patches of body feathers.




Saturday, September 13, 2014

Carolina Wren in the Rain

Today was a welcome day of drizzle in Georgetown.  This little Carolina Wren was not daunted by the weather and hopped around peering under all of the flower pots looking for bugs. Not sure if this is one of the season's juveniles.  The rain makes it look cute and scruffy ... or maybe just a bad hair day.

Canon EF 100-400mm f/4.5-5.6 IS - 365mm,  ISO-800, f/8, 1/160s, +0.3

Saturday, September 6, 2014

Ruby Throated Hummingbird Flash

More Ruby Throated Hummingbirds have shown up at the feeders this last week. Unlike the scenes from Rockport, TX, we are only getting one bird at a time at the feeder.  I found this nice article on hummingbird behavior giving me insight into just how territorial they can be. I suppose that along the migration flyway, any resident males guarding the feeders are getting overrun by the migratory swarms.

With the late morning sun to my back, the gorget feathers flashed like signal beacons, the iridescence looking more golden than ruby colored. Definitely worth trying to capture in a photo. After some patient waiting, I caught some images of a male showing a nice "flash" in the gorget. Note the black chin under the bill that distinguishes this common species from the Broad Tailed Hummingbird which is rare here in Georgetown.





I positioned myself about 9 ft from the feeder. The birds are still shy enough that they fly away if I move the camera so I used a monopod to hold the camera in position without tiring my arms while I waited. Rather then blocking select holes in the feeder, I opted to wait for one to land in the right spot.

I used a Canon 60Da camera and a Canon EF 100-400mm f/4.5-5.6L IS lens. With the lens fully extended and the camera set to ISO-400, I adjusted the aperture to f/7.1 giving me enough depth-of-field to focus the full bird but keep the rock wall, about 3 ft behind the feeder, out of focus. In this light, the shutter speed of 1/1600s was adequate for perched poses. I set the camera to high-speed burst imaging to assist in getting some shots that had interesting poses. I decided not to use a flash to keep from creating either "steel eye" or "feather sheen". Like some earlier pictures, I can see details of the yard behind me reflected in the the bird's eyes! However, not using the flash required some post-processing work to raise the brightness of the head shadows and reduce the noise in those dim parts of the image.

Tuesday, September 2, 2014

QSI with 35mm Lens

Continuing my experiments with using the QSI-540ws and camera lenses, last night I tested my Canon EF-S 18-55mm f/3.5-5.6 IS lens which came as the stock lens with our Canon 450D. Small lenses such as this do not have a tripod collar. Fortunately, the QSI has 1/4"-20 threads on the main body. I attached a Manfrotto RC2 quick release plate to the camera and a Manfrotto 323 RC2 quick release head onto the short Vixen dovetail. I mounted the assembly to the new imaging deck:


Focusing this proved much more challenging than the larger lens. The main reason is, at this combination of pixel size and focal length, the stars are very under-sampled. As such, it proved impossible to use a Bahtinov mask to focus. Even adjusting based on a star profile was challenging.

To capture the images during focusing, I centered a bright star and used LiveView to repeatedly capture a sequence of 5sec frames with 1x1 binning and 1/8 region of interest. To maximize image detail, I focused using a luminance filter which is par-focal to the H-alpha filter eventually used to capture the light frames.

To analyze the focus quality, I alternated between these two tools in Astro Photography Tool:
  • Focusing Aid - The focusing aid computes star-profile metrics which are shown both numerically and graphically. I used this to get an objective confirmation of minimal star size. 
  • Magnifier - Shows a highly zoomed-in view of the selected star. I used this as a sanity check for way-out-of-focus stars that showed up as doughnuts. Only a little tweak of the focusing ring can send things way out of wack when focusing manually. 
I wish these could be used simultaneously or that the Focusing Aid could also show magnified views.

Update 2014-09-08 - After sharing this difficulty with the author, looks like the next version of APT will allow the Magnifier view to track the active region of the Focusing Aid.

The tests I performed were at 35mm. I had planned on trying 18mm but, since I was imaging from the observatory, most of the field-of-view was obscured by the dome slit! The following image represents 7 frames of H-alpha data, each 900 seconds. The star quality on the edges of this lens are very elongated, but this is what I expected from previous uses.

QSI-540ws, Canon EF-S 18-55mm IS - 7x900s, Halpha

Sunday, August 31, 2014

Tiger Swallowtail on Milkweed

Today, we saw our first Tiger Swallowtail on the tropical milkweed. This one is a male as recognized by the smaller amount of iridescent blue.

Canon 60Da, EF 100-400mm f/4.5-5.6L IS, ISO-400, f/7.1, 1/640 +1.3

Canon 60Da, EF 100-400mm f/4.5-5.6L IS, ISO-400, f/7.1, 1/360 +1.3




Thursday, August 28, 2014

Star Test of Canon 100-400mm f/4.5-5.6L IS Lens

Last year, I tested my Canon EF 70-200mm f/4L lens for astronomical imaging. Those results showed very good performance at 200mm and adequate performance at 70mm. This has been borne out by actual imaging sessions with the lens. This evening, I repeated a similar test with my Canon EF 100-400mm f/4.5-5.6L IS lens which I have been using for birding. My previous tests on test pattern charts showed promise that this lens might be comparable to the fixed Canon EF 400mm f/5.6L lens that my wife uses for imaging. Here is the MTF chart for the Canon EF 70-200mm f/4L lens:


Test Setup

My hope is to use this lens with the QSI-540ws for wide-field imaging. Since I cannot electronically stop the lens without a DSLR, I decided only to test the performance of the lens with the aperture wide open. In order to more easily capture color images to test for chromatic issues, I used the Canon 60Da instead of the QSI to gather the test images. I found that 300s exposures at ISO-400 gave a suitable histogram shape. I auto-guided during the tests to minimize tracking issues.

The DSLR and QSI have different fields of view. To show "corner performance" for both of these cameras, I am reporting the detailed star images for several regions of the images as shown below. The blue frame is the field of view of the DSLR. The smaller green frame represents the cropped region I would have obtained using the QSI.  The four yellow circles are the regions detailed herein. These show the center of the frame, the corner for both of the cameras, and the mid frame region.


I performed the imaging tests at four focal lengths: 100mm, 200mm, 300mm, and 400mm. I had intended to test each of these focal length with the aperture wide open. Unfortunately, I inadvertently left the aperture stopped down to f/5.6 on the 200mm test somewhat negating the value of this test for me.

Test at 100mm @ f/4.5

The following image shows the field of view at 100mm.  The bright star is Deneb.


Details in each of the four regions are shown below:





Test at 200mm @ f/5.6

The following image shows the field of view at 200mm. Note that the lens was unintentionally stopped down from f/5 to f/5.6 in this image. Introduction of the octagonal edges of the iris into the light path causes some strong diffraction patterns on the stars. I recall that for the Canon 70-200mm f/4L lens this occurred without significantly improving the shape of the dimmer stars. Personally, I prefer round stars.


Details in each of the four regions are shown below:





Test at 300mm @ f/5.6

The following image shows the field of view at 300mm.


Details in each of the four regions are shown below:





Test at 400mm @ f/5.6

The following image shows the field of view at 400mm.


Details in each of the four regions are shown below:





Observations

At the shorter focal lengths, this lens performed very well. The slightly stopped down image at 200mm was excellent though I will not be able to stop down the lens when using the CCD camera. I would say that this lens is close in performance to the EF 70-200mm f/4L at 200mm and significantly better at 100mm.

Whereas the EF 70-200mm f/4L performed better at longer focal lengths, this lens seems to perform better at the shorter focal lengths. I qualify this conclusion somewhat because of the fact that the elliptical distortions are oriented the same way across the full frame rather than being radially symmetrical. It may be that I am seeing a tracking issue rather than a lens issue. At 400mm, I also notice more pronounced asymmetry in the diffraction spikes and halo around Deneb.

Another interesting difference between the two lenses was "image shift". As I used the electronic focusing controls in Astro-Photography Tool, the image would shift slightly as the focusing motor changed direction. Fortunately, the amount of shift was just small enough that the star stayed within the view port of the Focusing Aid feature in APT. I assumed that this motion was related to the image stabilization mechanics of the lens though it was turned off for these tests. I recall that when I focus on birds with IS enabled, there is a noticeable image shift in the view finder. Coincidentally, the orientation of this shift happens to matches that of the distortion visible in the 400m images.

Th EF 100-400mm f/4.5-5.6L lens has a full-time manual focusing ring similar to that of the EF 70-200mm f/4L. However, I did not have the time to test the ease of focusing manually.

I think my next step is to retest explicitly on the QSI, test the manual focus, and verify more carefully tracking quality.

Update 2014-08-31

Based on a post on Cloudy Nights, it turns out that I can use the following trick to stop down the lens and still use the QSI:
  • Attach the Canon 60Da to the lens
  • Dial AV mode and set desired f-ratio
  • Press the DoF preview button to force the iris to close
  • Detach lens while holding the DoF button pressed
Looking through the lens, I can see that the iris remains despite being unpowered. Assuming this does not damage the camera or lens, this gives me one option for stopping down the lens.

Another suggestion was to use camera filter step down rings as an external stop. This is a bit challenging because the "a little bit of stop" translates to a wide range of aperture sizes across the zoom range. By way of calculating what I might expect, I used the imaged star fields to estimate the actual focal length of the lens at the four marked positions on the lens barrel that I used to perform the above tests. This calculation gives me: 102mm, 197mm, 293mm, 380mm. Yes, this lens is not really 400mm.

Checking one of my 77mm filters for this lens, the measurement refers to the outer diameter of the threads. The filter itself has a clear aperture of 70mm which is still wider than what can be seen through the fully open iris, 68mm. The clear aperture of a step ring should be close to the inner thread size.

The table below shows the necessary inner ring size to match wide open aperature and aperture reduced by 1/3 stop.

MarkingFocal Lengthf-ratioAperture Open-1/3 StopNearest Ringf-ratio
400380 mmf/5.667.9 mm60.3 mm77-62 mmf/6.1
300293 mmf/5.652.3 mm45.5 mm62-49 mmf/6.0
200197 mmf/5.039.4 mm35.2 mm49-35.5 mmf/5.5
100102 mmf/4.522.7 mm20.4 mm-f/4.5

As selected, I would be able to sequentially nest the rings. Another option would be to use a 77mm to 67mm step-down ring as a "holder" for circular cut-outs of the right diameter and construct my own set of external stops. I am not sure what matte material to use to minimize reflection glare artifacts.

Update 2014-09-01

I purchased a simple Pro-Master 77mm to 62mm step-down ring and did some more testing last night. This time, I used the QSI-540ws camera and performed focusing manually. The ease of focusing was about the same as with the EF 70-200mm f/4L. That is to say, challenging but doable. Again, I guided the mount and imaged the star field around Deneb for 300 seconds with a Luminance filter. I performed the test only at the longest focal length (380mm), first wide open at f/5.6 and then with the step-down ring attached.

Test at 400mm @ f/5.6

This first imaging test is performed wide open. Same frame regions reported as above.




Test at 400mm @ f/5.6 with 62mm Ring

The second imaging test repeats the test above but with the 62mm step-down ring attached to the front of the lens.




Observations

Either the tracking was better tonight, or the consistent stretching of the stars is somehow related to the DSLR. The stars are much rounder throughout the frame. In the corners there is evident "shuttlecock-shaped" coma but it is not too bad.

The usefulness of the step-down ring seems to minimal at only 1/3 of a stop. The symmetry and intensity of the diffraction spikes on the central star are improved. The halo size and intensity seems to be unchanged. The mild coma on the corner stars remains unchanged.

After performing these comparative test, I left the 62mm ring on and took calibration frames. The flat image field for this configuration looks like:


and has this profile along a centered horizontal slice:



For a real imaging test, I captured eight 15 min frames of the Pelican Nebula with a 12nm H-alpha filter, calibrated and stacked in DeepSkyStacker, then performed some basic stretching, noise reduction, and sharpening in Photoshop as well as reduction of halos on the two brightest stars.

QSI-540ws, Canon EF 100-400mm f/4.5-5.6L, 8x 900s, H-alpha

Saturday, August 23, 2014

Pipe Nebula from Canyon of Eagles

I tried out the CCD/Lens combination this evening at Canyon of Eagles. I spent quite some time trying to image Rho Ophiuchi again with this equipment combination. That was a mistake as the target was too low to get good data.  I then picked up a few frames of data on the Pipe Nebula with better results.

This image is taken with Canon EF 70-200mm f/4L lens at about 100mm. I cooled the CCD to -5C with ambient temperature around 32C. I collected 2x900s Luminance frames at 1x1 binning and 2x300s RGB frames at 2x2 binning. Calibration performed with matching dark and bias frames, 10 each.


I did not collect nearly enough color data - only the stars picked up much saturation. However, even with only two stacked frames in each color, the noise level is considerably less that the DSLR.  Focusing without the EOS electronics is still challenging but possible. At 100mm focal length, the peripheral stars are showing some radial elongation, similar to field curvature issues.

I was also able to get a single set of LRGB frames of a field containing the Eagle Nebula and Omega Nebula.