Mars at Opposition - Day 2

Goal: Capture Mars near the Oct. 13, 2020 date of closest approach (Opposition).

Left tripod vibration pads in the lawn from the Mars imaging session on the 15/16th. In the early afternoon of the 17th, brought the tripod back out & set back on vibration pads in the lawn.  Mount was found to be level... no need to re-level (time & effort saved) by keeping the pads in the lawn.  

Installed counterweights & the Celestron CN-10.  Rebalanced the mount... determined a working arrangement of counter weights... and worked out optics configuration for the CN-10 with the Zwo ASI120MC-S as the primary imaging camera with and without the 3X Barlow.   Was not able to use the M60 -> T-thread adapter with the eyepiece projection cell to the Zwo and reach infinity focus.  Instead, used the 2" eyepiece adapter -> 1.25" eyepiece adapter -> Zwo (with eyepiece adapter installed) for prime focus and inserted the Celestron X-Cel LX 3x Barlow (with eyepiece holder) into the optical train for very high magnification collection.  

Examined tree tops down Metropolitan Avenue as the best available target to examine initial focus settings at both prime and with the Barlow installed.

 

Attempted to set up the NexImage 5 as a guide scope.   Results (with earlier firmware update) inside Indi/Ekos using the v4l2 driver were poor.  Extremely slow transfers and inconsistent operation. Gave up on the camera after limited success testing indoors earlier in the day.

With night came polar alignment with the polar scope.  Found the initial alignment to be very close... with only very slight azimuth adjustment required.

After focus adjustment (shooting numerous star fields at prime focus near zenith), ended up using astrometry (frame solving) within Indi/Ekos across a range of dense star target areas with the Zwo ASI120MC-S  to produce a working mount model. This indicated a total angular extent at prime focus with this camera of 13.7' (which allowed the effective focal length to be calculated as 1202.92mm @ F4.73 based on 1280 pixels across the sensor @ 3.75 um per pixel).  This also resulted in getting Mars centered at prime focus.  Adjusted frame rate and lowered gain (down to 10) on the ASI until contrast indicated clear features on the planet.  Collected several SER files with framerates of around 7.8 frames/sec to obtain a total of 1616 frames across 8 total SER files.  Had the video window in Indi/Ekos set for 30 second captures.  Transferred examples and examined quickly in AutoStakkert to ensure usable frames.

Results from imaging at prime after reducing the total number of frames using PIPP from 1706 total frames collected to 148 selected based on quality and stacking with AutoStakkert showed the start of some usable contrast.

Used the Indi/Ekos telescope mount controls to put Mars near the center of the frame and inserted the 3X Barlow ... but found the resulting image had nothing.  Started capturing frames with the goal of plate solving with astrometry package, but found enormous glare from the planet using 25 second captures.  Adjusted with mount controls to once again center the planet... and then refocus.  Began collecting an additional set of SER video files to obtain a total of 1706 frames (keeping 148 for use in AutoStakkert).

  

A result on Astrobin from 10/17 with an 8" Celestron SCT offers inspiration on the potential for improvement.

Lessons learned:

1) Needed to have collected tens of thousands of frames.  Collected at 30 second intervals with a hundred frames per file... but really should have collected for several minutes at a time. 

2) Focusing was a chore on the CN-10... and results uncertain.  A two-speed focuser would be a big help (as would a motorized focuser).  But more time spent focusing (on stars, etc) may have helped.  This was done at prime focus, but with the 3X Barlow, Mars itself was the target of the focusing effort (starting with airy disk and moving to gaining contrast on planet features).

3) Working guide camera is even more important if the small planetary camera (Zwo ASI120) is to be used for capturing video through the telescope.  The number of stars available (even with 60 second integration times) is simply insufficient for plate solving (only the online version of astrometry was able to produce an occasional result).  Plate solving consistently failed in the neighborhood around Mars...which was particularly frustrating.