Comparison of C14 (on AP Mach1 mount) to Skywatcher 12 goto
Thursday, May 13, 2021 22:30
Seeing: 4/5, Transparency: 4/5, SQM: 21.11 at zenith (according to dark sky meter app for iphone; but I think it’s brighter than this as the phone was well shielded from surrounding light on the horizon; normally cannot see the Milky Way except very faintly when it’s at zenith in the summer)
Location: Rosh Pina, Israel
Target: M3 nearly at zenith
Goto: both scopes located the target easily, tracking was excellent over a period of 2 hours
About the scopes:
• SW12 was purchased new about 5-6 years ago. The focuser was upgraded to a Moonlite focuser, the tube was flocked and a fan was added.
• C14 was purchased used. Seems to be vintage 1991 or so, with Starbright coatings; in excellent shape, well collimated, insulated with reflective bubble material, with a home-made dewcap.
Eyepieces used for comparison:
• 12mm ES92 degree on SW12 at 125x FOV=0.74 degree, exit pupil = 2.4mm
• 31mm Nagler on C14 at 126x FOV = 0.65 degree, exit pupil = 2.8mm
• Wider field of view in SW12 with slightly enhanced contrast
• Note: the 31mm Nagler, which I used on the C14, is well known for reduced contrast (grayer background) in light polluted skies; the 35mm Orion Ultrascopic looked more contrasty with blacker background.
• Fainter stars more easily seen in C14
M3 is centered in a neat triangle of stars. The star in the triangle closest to the cluster (SAO 82950, mag 9) is accompanied by two faint 12 mag stars and one 13 mag star that arc towards the center of the cluster. All three stars were visible with slight concentration in direct vision in the C14 at 125x. Only two, the two 12 mag stars were easily seen in the SW, the third 13 mag was elusive (GAIA 1454797442834962176; remember, these are light polluted skies, but by midnight with the 6mm Ethos in the SW12 at 250x all were visible, though still not as bright, clear as in C14). The overall contrast in the SW12 seemed marginally better, since the cluster and its faint companion stars seemed to stand out a bit more. The view was very slightly more pleasing in the SW – I had been expecting it to be visibly sharper, but the difference was rather slight. Both scopes served up a detailed view of the dense cluster, with well-defined stars in the cluster and lovely gradations in brightness from the core to the periphery. The 14” mirror, as would be expected, delivered a bit more than the 12”.
• Views are very similar in both scopes when viewing at same magnification.
• SW12 has slight edge in contrast & sharpness
o Flocking inside of C14 tube might improve contrast, but I’m not eager to disassemble this scope and risk damage
• SW12 has crisper focusing and better focuser: you know when you are there! Though C14 is not as crisp to focus, there is only minor difference in sharpness between the scopes; SW12 has very slight edge.
• SW12 easily delivers very pleasing wider fields (up to 1.69 degree with 31 Nagler; as opposed to 0.74 degrees in C14 with same eyepiece)
• C14 has slight edge in visibility of faint objects
• C14 can easily deliver higher magnifications under ideal conditions (I used it yesterday to view Blinking Planetary Nebula at 832x with APM 5mm (really 4.7); maximum magnification in SW12 with 4.7mm is 319x).
• C14: Setup and viewing are easier (eyepiece more accessible and it is permanently mounted in an observatory, setup is 5 minutes to open the roof). Better access to entire sky, fewer obstructions.
• Maximum pleasing magnification achieved this night was 250x in the SW12 with Ethos 6mm. I didn’t attempt to push the C14 to its limits tonight: I know that when viewing is excellent, the limit is incredible (I have used it up to 832x).
So I will use the C14 for ease of setup and use at home and when I want high magnification on planetary nebula, globulars and open clusters. Galaxies would be good, but there is too much light pollution to make that enjoyable. Whenever possible, I will take my 10" out to dark skies.
When I also want wider, crisper views I'll use the Skywatcher 12. I love to see clusters in a larger field, or multiple objects together.