Tonight I tried my hand at photographing a few Deep Sky Objects. The Hartman mask was extremely useful for focusing, but after tonight it’s clear that I’m going to need to control the D50 by tethering it to the laptop to get best results. Manipulating the zoom controls for the LCD is awkward at best. I may need to spend some time just practicing focusing on a few different stars.

Saturn was actually the first target before the DSOs. I captured a couple of images at ISO 800 and 4 sec exposure that included the moons Titan, Tethys, Dione, and Iapetus (Rhea was transiting and lost in Saturn’s glare). I reduced the exposure time several steps, but it was hard to see much detail in the LCD (another argument for tethered control), so I moved on.

Next I tried M13, the globular cluster in Hercules. This actually turned out to be the best subject of the night. One of the photos had some jitter from the wind shaking the telescope (did I mention it was occasionally quite breezy?). Most were fairly good, however, with nearly round stars — limited by the sharpness of the focus, most likely. Click the image to see a very large full-sized photograph. If you look closely you can see stars of several different colors in the cluster. M13: FL 2032mm, ISO 800, 30sec exposure, f/10.

M13

Next came M57, the Ring Nebula in Lyra. I captured several images, but they all showed noticeable wind jitter. I’m certain this is telescope vibration and not tracking error because the motion vector varies from one photograph to the next. I merged the four best frames in Registax, stretched to compensate for the motion vector, applied a gamma correction to increase the brightness, then reduced the image size to improve the apparent sharpness of the focus. M57: FL 2032mm, ISO 800, 30 sec exposure, f/10.

M57 - The Ring Nebula

The next target I tried was M27, the Dumbbell nebula. However, even with a 30 sec exposure at ISO 800 there was almost no trace of any nebulosity in the photo, so I moved on.

I decided to re-balance the telescope forward to compensate for the extra weight of the camera on the back. This, of course completed wrecked the scopes alignment so I had to restart. After alignment I focused the camera on Mizar (ζ UMa). It’s a nice blue double, but it’s included here for more than aesthetic reasons. According to SNP, the separation between Mizar A and B is 14 arc-seconds. In the unprocessed photo, the distance between the centers of the stars is approximately 19.3 pixels (along a diagonal). This puts the resolution for the camera at about 0.725 arc-seconds per pixel. By comparing similar measurements of other doubles I should be able to calculate the actual resolution more accurately. Mizar: FL 2032mm, ISO 800, 1/2 sec exposure, f/10.

Mizar A and B

After rebalancing I Attempted several images of the Whirlpool galaxy M51. The cores of M51 and its companion galaxy both appeared tiny and featureless over several photographic attempts.

I attached the Nikon D50 to the C8 SCT last night for the first time. Of course I was excited to see what kind of pictures I could take with it, but I also had concerns about how I was going to focus the camera. The view port on a SLR is pretty small, which is challenging on its own. Add the fact that the camera will be attached to the bottom of a telescope pointing nearly straight up, and seemingly simple procedure like focusing becomes a significant challenge. So I did a little research and I found an interesting page on Arcturus Observatory / Comet Man web site that discussed using a Hartman mask to focus. Then I wondered: could I make a Hartman mask? Would it work?

Following that idea, I found a sheet of heavy weight art paper, set the C8’s lens cover on it, and traced a circle of the inner diameter of the OTA. Using a standard Swiss Army pocket knife I made three cutouts: two circles and a triangle. It was quick, cheap, and amazingly useful. Here’s the mask and the pad or art paper from which it was made:

Hartman Mask

My wife said it looks scary. Maybe that’s because I was holding the mask over my face saying, “ooooo,” but I don’t see how that could have any effect. Besides, the circles are much farther apart than my eyes, so I couldn’t see a thing.

Anyway, the real fun began when I set up the C8 and used the mask to focus on a star. I got distracted for a while just watching the pattern coalesce and split as I turned the knob. Of course the real test was whether it would work with the camera attached. I wanted to try getting a picture of Saturn and its moons. First I aligned the scope and slewed to Regulus, which was the nearest bright star to Saturn. Then I removed the eyepiece and the star diagonal and attached the camera to the visual back using the T-ring and T-adapter. Then I started capturing images.

The following focus trial images were taken at ISO 400 with a 2 second exposure time. It took several trials for me to establish a procedure and I won’t include the first six or seven photos for that process. Let’s just say there was not a lot of instant gratification here. In any case, I was still exciting to see if I could make the mask work.

Like many digital cameras, the Nikon D50 allows you to “zoom in” on a portion of an image during playback. After each image I magnified the diffraction pattern as much as possible to gauge the focus.

Hartman Focus - 1

As you can see, the pattern is pretty distinct. This means the image is not in focus. I turned the knob about 20°-30° and took another picture.

Hartman Focus - 2

The pattern is smaller and brighter. That’s good because it means I’m turning the knob in the right direction. After a little more knob action I took this one:

Hartman Focus - 3

Now the diffraction pattern has mostly disappeared (no rings or dark centers), but the spots are still distinctly separate. Notice the triangle shape of the bottom left spot.:

Hartman Focus - 4

In this image the star appears pretty well focused. Keep im mind I was looking at this outside, bent at the waist, squinting at a little LCD screen smaller than the image you see here. I gave the knob a little more twist and took another picture to see if the image could get any sharper.

Hartman Focus - 5

Oops! Too far! Notice how the triangle has inverted from the earlier images. I turned the knob back 3/4 of the way to its previous position.

Hartman Focus - 6

Now that looked like pretty good focus. Also, it was getting late and the mosquitoes were starting to gather in larger numbers. I was anxious to move on to imaging Saturn.

After slewing to the ringed planet I captured 17 images at different ISO settings and shutter speeds. The best picture of Saturn was taken at ISO 400 with the shutter speed 1/4 second.

Saturn Solo

The best picture of Saturn’s moons was taken at ISO 400 with the shutter speed 5 seconds.

Saturn's Moons

By this time it was getting late and the mosquitoes were driving me crazy. I disassembled everything and finished for the night.

The human eye seems to have a better dynamic range than the D50. I combined the two previous images as a composite that represents how Saturn appeared when observing visually. The picture is rotated 90° and made extra-wide to show the faint moon Iapetus on the left. The image size is reduced on this page, but you can click on it to see the full-sized composite image.

Saturn (composite image)

Location: at home in Tomball, TX
Cloud cover: 0%
Transparency: above average (4/5)
Seeing: est. avg (3/5)
Darkness: no moon, city glow
Wind: light, less than 5 mph
Temperature: 65º+
Humidity: 45%-60%
Dew Point: 45º-55º
Time: 9:00 pm – 10:15 pm CDT
OTA: 8″ SC

Started by observing M13. Some faint individual stars appeared in averted vision. Seemed larger apparent diameter than other GCs I recall.

Next stopped at Saturn. Rhea and Titan were easily visible. Two stars (mag 10 and mag 12-13) also in the field that I mistook for Iapetus and Dione (respectively).

I wanted to spend some time observing an airy disk to estimate seeing conditions. I started with Arcturus. Very bright center, yellow-orange color. Ring pattern was usually discernible. Focusing was somewhat challenging due to variations in distortion. Radial streaks or spikes also visible. Needed 7.9mm ep to observe diffraction rings.

Also noticed there was a diffraction line across the entire FOV when using the 45º erecting prism diagonal. Line appeared with different EPs, did not appear with 90º reverse-image prism diagonal.

Finally tried observing airy disk for Spica. Blue color was striking contrast to Arcturus’ yellow-orange. Observed similar variations and distortions of airy disk as observed with Arcturus. Also noticed that the tips of the radial spikes in one direction had an orange tint. I moved the star across the FOV to see if the effect was an off-axis abberation, but the orange tips retained their orientation independent of Spica’s position in the field. Spica was about 45º altitude, so it didn’t seem like it would be an atmospheric effect. My other guess was that Spica might be a double star and that the secondary might be spectral type G or K. A quick google search shows Spica is indeed a binary double, but I haven’t yet found any info on the separation or the spectral class of the companion.

I’d say the seeing was about 4/10 on the Pickering scale, often varying between 3 and 5.

Location: at home in Tomball, TX
Cloud cover: 0%Transparency: average (3/5)
Seeing: poor (2/5)
Darkness: no moon, city glow
Wind: breezy 10-15 mph
Temperature: 70-75
Humidity: 52% up to 64%
Dew Point: 50-60
Time: 8:30 pm – 10:30 pm CDT
OTA: 8″ SC

Used Live cam to image Cor Caroli (DBL) and Saturn. Live cam does not appear to have as much clarity as the NexImage; images are fuzzier. Still post-processing image data for publishing.

Cor Caroli taken with Creative Live Cam through Celstron 8" SCT under poor seeing conditions. 91 total frames aligned and stacked.

Also observed Saturn visually. Titan, Rhea, and Dione formed a nearly equilateral triangle off one limb of the rings, Tethys orbited outside the other limb. Iapetus still at relatively small separation from Saturn.

Saturn and five of its moons taken with Creative Live Cam through Celstron 8" SCT under poor seeing conditions. Two separate exposure settings for Saturn and for its moons. 253 total frames, aligned, stacked, and heavily processed.

M40 DBL in UMa faint and unremarkable, approximately equal magnitudes.

M85 GAL in Com appeared as a very faint fuzzy.

Algorab DBL in Cor – easy split, guessed delta mag 4 or 5. SNP lists Algorab as 2.9, doesn’t show companion or even indicate Algorab is a double.

24 Com – yellow primary, blue secondary. Guessed magnitudes 4 and 5, SNP lists them as 5.0 and 6.6, but online reference listed them as 5.2 and 6.5. In fact, I’ve noticed that researching star magnitudes online there is a lot of variability inthe magnitudes reported for most stars. Not sure what to make of that yet.

Location: at home in Tomball, TX
Cloud cover: none
Transparency: above average (4/5)
Seeing: average (3/5)
Darkness: no moon, city glow
Wind: none
Humidity: 50%-75%
Temperature: low 60’s
Start Time: 8:20 pm CDT
End Time: 10:30 pm CDT
OTA: 8″ SC

Saturn alternately fuzzy & clear; Iapetus “close” to planet, Titan and Rhea distinct, Dione & Tethys occasionally lost in glare and turbulence.

M35 OC was amazing, brought Amanda outside to see. Many, many stars (guide info said 70+) over a narrow magnitude range within 1/2 degree region.

38 Gem DBL, could not see color difference. Guessed delta mag between 3 and 4; SNP lists them as 4.7 and 7.8.

β Mon TRIPLE, split with 12.5mm Plossl, appeared DBL in 25mm.

NGC 2392 (eskimo nebula) appeared as a fuzzy disk with a distinct central star. No detail visible.

ζ Can DBL/QUAD (tegmen); ζ1 and ζ2 easily split, close binaries beyond ability of 8″ SCT.

ι Can DBL; blue and yellow easy split. estimated yellow about 1.5 mag brighter than blue. SNP actually lists them as 4.0 and 6.6, so more like 2.6…

NGC 3242 PNEB, also called “Ghost of Jupiter”. Appeared as a fuzzy disk with no detail and no central star. Seems smaller than Jupiter (in arcsec).

location: Tomball, TX
time: 800pm-930pm
cloud cover: 0%, gradually increasing
transparency: 100%
seeing: poor (2/5)
darkness: city sky glow, just past quarter moon
wind: gusty 10mph+
temperature: low 60’s
humitidy: 35%
dewpoint: 31F

barely able to discern tiny black gap between rings and planet. Titan, Dione, and Tethys formed a nearly equilateral triangle to the left of the rings. Rhea about 2 ring diameters to the right.

54 leonis, double star. I guessed difference of 1 mag, SNP lists them as 4.3 and 6.3. primary appeared white with blueish fringe, secondary subtle light blue. close pair but definitely not a hard split.

location: Tomball, TX
time: 730pm-900pm
cloud cover: 0%
transparency: 100%
seeing: average (3/5)
darkness: city sky glow, 1st quarter moon
wind: 5-10mph

lunar terminator crossed montes apenninus, mountain peaks were outstanding. high contrast thin fissures in SE mare vaporum: rima hyginus and rima ariadaeus. long parallel hills near rima hyginus seem un-crater-like, perhaps formed by tectonic activity?

rings of Saturn appeared as a line segment through the planet’s disc. Rhea and Dione out to the left of the rings. Tethys beyond the right edge of the rings, sometimes swallowed by bad seeing. Titan bright about 4x ring diameters from Saturn, Iapetus approx, 4x farther than Titan and surprisingly off the “line” of Saturn’s rings, probably due to orbital inclination.

location: Tomball, TX
time: 830pm-1130pm
cloud cover: 0%
transparency: 100%
seeing: poor (2/5)
darkness: city sky glow, 1st quarter moon
wind: 2-5mph n
humidity: 40% up to 60%
temperature: 65F-52F
dewpoint: 40F-43F

ξ UMaj – slightly yellow, could not split with 7.9mm

ν UMaj – golden primary, could not split, used SNP to verify that nearby star was not secondary

Mizar – nearly identical, bright pair with a touch of blue hue, close but easily split

Englemann 43 – easily split even with 25mm. SNP lists these stars as HIP50505 (primary) and TYC3007-899-1 (secondary). I can’t find a reference to this star anywhere except the Sky & Telescope article.

Saturn – seeing varied from 3/5 to 1/5, usually 2/5. ring shadow inside ring edge; south equatorial belt occasionally visible. Titan clear but could not discern color. Rhea mostly visible but occasionally obscured. Tethys near rings faint and rarely visible. several stars visible nearby, including mag 7 HIP50473.

M3 – faint but unmistakable. in good seeing individual stars visible both fringe and interior.

Measured true field width of 25mm using dec readout. Star at left edge (58′ 38″) and right edge (22′ 54″) indicates true field with is 35′ 44″. SNP calculated the field at 37′, so I feel confident that the view in SNP matches the actual field during observation.

location: Tomball, TX
time: 830pm-1030pm
cloud cover: 0%
transparency: 100%
seeing: avg (3/5) to poor (2/5)
darkness: city sky glow, full moon
wind: 5-10mph nnw
humidity: 30% up to 50%
temperature: 59F-53F
dewpoint: 31F-39F

M42 in 25mm. Less nebulosity discernible than normal presumably due to full moon.

Observed iota cancri; color of primary (reddish) not as distinct as nights past.

No detail visible in Mars.

Saturn’s moons best in 25mm. Titan and Rhea clear, Tethys and Dione occasionally obscured by bad seeing, Iapetus a challenge, often obscured.

Waxing full moon very bright. First time to attempt identification of features. ID’d Tycho, Copernicus, Kepler, Aristarchus, and Mare Crisium.

Location: Tomball
Temperature: upper 40’s
Clouds: none
Seeing: average (3/5)
Transparency: good (4/5)
Instrument: 8″ SCT

First night to observe from Zeke’s place. The sky is slightly darker than home and the area has wider overhead field of view than home.

Observed Saturn in 25mm, several moons visible. Titan, Rhea, and Iapetus were clear. Dione sometimes faded out with bad seeing. Tethys was occasionally visible but quite faint just above and to the left of the rings. Both Dione and Tethys were easier in the 15mm, which developed a smudge.

Also visited a few double stars. Iota cancri was splendid contrast of red and blue.

We observed m42 and discussed the process of star formation within nebulae.

Zeke wanted to see Mars. The “dark” patch of Syrtis Major was visible — an area of just slightly diminished brightness compared with the rest of the planet.