Mak Project notes from May 6 2021
Over the last several months I've been playing with the Mak project.
The overall goal was to try to repurpose the Mak into something more than a planet/lunar scope. It's the highest magnification scope that I have at F12/1500mm. This would be a good device for bright planetaries and bright galaxies once a few hurdles had been cleared.
Last time I tried, I ran into these problems:
Reducing these two problems featured the deep dive into the workings of the mount, scope, software, and hardware. This investigation has lasted for months and is finally coming to yield useful data.
First, I tackled tracking.
Part of the problem that I've had over the past is getting good tracking. I've always had some amount of drift and oblong stars in long exposures.
One of the solutions was to change the exposure length to be shorter than the problem times. This option was only availabile for digital work but was the easiest to resolve as dropping the duration of exposures to no more than 10 minutes.
Next, I addressed mechanical. During the latter part of 2019 and into early 2020, I gathered the hardware and knowledge to replace the plastic gear boxes to McLellan metal gear boxes as detailed on the Losmandy groups. This was a known upgrade that helps with smoothness of tracking and resists the higher torques generated by the newer motors.
I followed this guide from the groups.io threads.
Once I finished, I aligned the worms, removed the problematic belleville washers, and upgraded the bearings on the G11 and GM8 mounts. I did this for all the mounts in my posession at the time. This included changing on the older G11 that I'd rented from Anthoy DLC.
This "renting" was realized in mid 2020 when I finally let go of the medium format film hardware by giving it to Isabel DLC and returning the G11 mount that I'd purchased from them a few years back. The idea was to pass along the film gear that had been giving me so many frustrations. I did not see myself getting back out to the field again due to the covid pandemic and was "giving up."
At that point, the mounts were stored while I cleaned up the shed and removed a lot of clutter.
The Mars opposition came and went and I did a little observing.
Playing with the Mars opposition got me thinking again about the Mak.
Looking at last night's imaging run, I'm not 100% sure the 200 step offset is needed - maybe drop it to 150 steps? Still, worth checking.
Also, I see that there's consistent RA wobble. I checked the logs and the Y axis corrections were high. This was the axis that was set to 70% response.
I've now put that back up to 100% - will see if it starts bouncing around.
The graph looks oblong when it was guiding.
I do wonder if this is something that could be fixed with PEC.
The other possibility is that I offset the RA a bit more in the expectation to have more bias to settle the RA a bit more.
Another lesson learned:
The QSI camera has a minimum exposure that the @focus3 will trigger when looking at bright stars. Anything brighter than mag 5 will hit this limit. The shortest exposure will be .015 seconds and will wallow in bias noise rather than showing any actual light.
This is an important thought when considering a target star for focusing.
Also, @F3 can do its magic with the bahtinov mask in place. This gives an instant confirmation of the accuracy of focus.
The Light pollution filter is off by 200 steps or a little more. Pretty easy to manage.