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.

Location: at home in Tomball, TX
Cloud cover: 0%
Transparency: n/r, est. average (3/5)
Seeing: n/r, est. poor (2/5)
Darkness: no moon, city glow
Wind: light, less than 5 mph
Temperature: 75º+
Humidity: n/r
Dew Point: 45º-55º
Time: 8:45 pm – 10:00 pm CDT
OTA: 8″ SC

ε Boötis DBL very close pair, cannot split in 12.5mm except in rare moments of good seeing (poor seeing generally), appeared as oval with red and blue sides. completely blurred in bad seeing.

M81 GAL UMa very faint fuzzy with no detail.

ξ Boötis DBL est. mag 4 white and mag 5 orange, close pair easily split in 12.5mm. Wikipedia lists ξ Boötis A as 4.5-4.7 G8 variable and 7.0 K4.

κ Boötis DBL est. mag 4 blue and mag 5 /yellow, close pair easily split in 12.5mm. Wikipedia lists them as 4.5 A8 and 6.6 F1.

M3 GC west of M13 (which was behind the house in the NE ) – wide fuzzy, no individual stars visible.

Mizar DBL est. mag 2 blue and 2.5 white. close pair easily split in 12.5mm. Wikipedia lists them asmag 2.2 A1 and mag 4 A7.

Cor Caroli DBL est mag 2 blue/white and mag 3.5 yellow/green, another easy split. Wikipedia lists them as mag 2.8-3.0 variable A0 and mag 5.5 F0.

My estimates were much worse tonight than last night, especially the secondaries.

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.