Sky-Watcher Star Adventurer Mount Testing
Wharton State Forest, New Jersey
Joe Stieber, August 2-3, 2022

  

I arrived at the field about 11:40 pm EDT and left about 1:25 am. The sky was cloud-free, but transparency was perhaps 3 to 4 on a scale of 1 to 5. It was warm and somewhat muggy (humid) although there only the slightest dew formation by time I left. Mosquitoes were a mild nuisance.

All pictures here were captured with a Canon EOS RP DSLM (digital single lens mirrorless) "full frame" camera and a Canon 200 mm F/2.8L EF lens (via a Canon EF to RF lens mount adapter) tracking on a Star Adventurer motor-driven equatorial mount (no guiding). The camera was connected via a ball head. Earlier that day, I had re-adjusted the reticle in the mount's polar alignment scope to match the relative positions of the North Celestial Pole and Polaris as shown by SkyTools and SkySafari. The manual for the mount was unclear about the relative position (see excerpt at the bottom of the page), so I wanted to test my settings in the field. Visually as I set up, the SkyTools and SkySafari positions of Polaris and the Little Dipper (and hence the invisible pole) matched the actual sky (no surprise there).

I used the same exposure time for all the pictures here, a not-too-demanding 8 seconds. On a fixed tripod, my experience with this camera and lens combination has shown that 2 seconds is a safe maximum, perhaps 4 seconds depending on the sky location and the degree of subsequent cropping to be used. All were shot with the lens wide open at f/2.8 while focusing was accomplished using 10x live view. Color temperature was set to 4200K for the JPEG capture, but as seen here, all were single RAW frames concurrently captured, subsequently applying minimal processing to them with Canon's Digital Photo Professional 4. The ISO setting varied from 3200 to 6400 and they were each cropped to different degrees, both of these settings are noted in the captions.

I also took ten (10) frames of each at the indicated settings using the camera's built-in intervalometer. At some point, I may try stacking the images to improve their quality, but that's a bridge I haven't crossed yet. I also intend to try longer exposures and/or longer focal lengths to determine the points at which the mount becomes unsuitable. Keep in mind that I'm not an astro-photographer, I just take celestial snapshots.

The images are nominally north up and east to the left. Mouseover for Labels.

  

  

Saturn at the Tail of Capricornus

Taken at 12:58 am EDT on August 3, 2022, ISO 3200. Saturn, Deneb Agedi and Nashira in Capricornus now form a compact, nearly equilateral triangle to unaided eyes. They, along with 42, 44 and 45 Capricorni are all easily visible in the same field of most binoculars, and its a lovely sight. Saturn will continue to move westward in retrograde motion (to the right in this north-up image) until it's stationary on October 23 (almost 4 west of Nashira) when direct (eastward) motion resumes. This image was cropped to 38% of the width x 58% of the height of the original linear dimensions to a 4.0 square. A couple of satellite trails are visible too. The parenthetical value after the objet designation on mouseover is the magnitude for the object (decimal points omitted for stars).

 

  

Asteroid (4) Vesta

Taken at 1:01 am EDT on August 3, 2022, ISO 3200. The asteroid/minor planet (4) Vesta was in the constellation Aquarius and was easily seen in binoculars at magnitude 6.2, slightly dimmer than the nominal magnitude 6 threshold for unaided eyes. It will reach opposition on August 22 at magnitude 5.9, just visible with keen eyes from a dark site. It will be in retrograde motion until October 7. This image was cropped to 72% of the original linear dimensions (with no change to the native 3:2 aspect ratio) for a field 7.4 wide x 5.0 high,

  

  

The Helix Nebula

Taken at 1:10 am EDT on August 3, 2022. The Helix Nebula, NGC 7293, is in Aquarius and was just 3 southwest of (4) Vesta at the time. Although its magnitude is relatively bright at 7.3, the large size of this planetary nebula results in a low surface brightness (magnitude per square arc second), so it can be difficult to see even with a largish amateur telescope unless a narrowband filter is used. Seemingly contradictory, it's not a difficult target for large binoculars (objectives from 50 mm upwards) at a dark site.

This image was cropped to 29% of the original linear dimensions (with no change to the native 3:2 aspect ratio) for a field 3.0 wide x 2.0 high, the most "magnification" of any image in this series, so the star dots are the largest, but still no trailing is evident. Granted, the nebula is dim here, but surprisingly distinct for the "snapshot" exposure. Of all the subjects in this series, the Helix Nebula would probably benefit most from stacking the ten frames captured.

  

  

Neptune and the Hockey Stick

Taken at 12:34 am EDT on August 3, 2022. The distant planet Neptune is currently in Pisces, but will cross the border into Aquarius on August 19 as retrograde motion takes it westward to opposition on September 16. It will be stationary on December 4, when it resume direct (eastward) motion. At magnitude 7.8, Neptune can be see in binoculars, but it looks like a star in binoculars, so one must match patterns to pinpoint it. It also helps to have impromptu asterisms to establish a path to it. Last year, I found it by starting at the compact arc of Psi 1,2,3 Aqr, shifting up to Phi Aqr, then sliding east toan elongated diamond asterism (shown on mouseover). Neptune was seen moving from the left end of the diamond through it past the right and then back to the diamond again beofre solar conjunction.

This year, it's well left (east) of the diamond, but not so far that it couldn't be used for finding Neptune. Alternatively, one could start at bright Jupiter to the east, slide west (to the right) and pick up a "hockey stick" stick asterism (also shown on mouseover). Neptune has been at the upper vertex of a small triangle just west of the top of the hockey stick's handle since the beginning of June (it was stationary on June 28). It's now moving westward enough that the small triangle is breaking up, but still not difficult to follow if one takes a look on a regular basis (and it's fun to track it's motion against the background sky; ditto for Uranus and Vesta).

This image was cropped to 82% of the original linear dimensions (with no change to then native 3:2 ratio) for a field 8.4 wide x 5.6 high. As indicated by the time, Neptune was my first target of the night. Being the most eastward of the targets, it should have been last when it was a bit higher in the sky. At the time, it was at 28 altitude.

 

 

Polaris and the Reticle in the Sky-Watcher Manual

This item from the instruction manual showing the alignment of Polaris in the reticle (yellow emphasis mine) seems to ignore that the polar scope is a straight-through refractor, and therefore, the apparent sky through it is rotated 180 from a direct view (i.e., it's upside down and backwards). This was confirmed by literally looking through the polar scope. So, it seems to me that Polaris should actually be at the 5 o'clock position if Kochab is at 11 o'clock from Polaris in the sky. Note that the star symbol sort of missed the 11 o'clock marker. Anyway, for wider-field shots, would the 1.3 diameter of Polaris' circular path around the pole make a noticeable difference for shorter exposures? Polaris is currently at an apparent declination of 89 21′ 03″ North, so it's 38 53″ or 0.65 from the pole.

 

 

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