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Latest eFinder Lite tweak

Having a camera based device with no image display is an interesting challenge.  My latest extension seems to solve most issues.

It displays a patch of 32x32 pixels around the brightest star in the image, its max value, the number of stars found, and the current exposure value, plus a PSF of the star as a plot.

As long as you arent too far away from focus, this works really well in tweaking focus and adjusting exposure to get a reliable capture of stars (as determined by the Tetra3 centroid extraction)

The OLED has no greyscale so the star image is very crude, but does help. The PSF and star count are key.

I want to add it to my standard eFinder, but I have to send the frame down the USB from Pi5 to the handbox Pico. More learning required!

New eFinder ‘Lite'

Having developed and improved the eFinder, it had reached a good point to leave it as is. Quite a few people around the world have or are building their own, and it seems to be a stable design now. So what next!

I had previosuly tinkered with the Raspberry PI HQ camera (cheap and small) but left it in favour of the ASI 120 and its very good sensitivity and low noise. But others have had success (eg PiFinder) so time to have another look. Also, the Pi Zero 2 W was worth a look as an alternative to the Raspberry Pi4 or 5. It has a quad core processor, GPIO pins camera interface and can run Debian 12 which I use in eFinder. Drawbacks are slower clock speed, very low RAM size (512MB) and one only USB port.

Along with the change in camera and processor, I decided to look at Tetra3 as an alternative to as the plate-solver.

A fuller description of the build and how to copy it is here. But here are some ‘highlights’ …

  • With a faster lens (25mm f1.2) the Pi HQ camera can produce acceptable images with 1 second exposures.
  • The Pi Zero 2W will run my eFinder code, after a bit of slimming down. It's slow to boot and load, but once done it is OK.
  • Tetra3 is amazingly fast. It does need care in generating its search database and setting its solve parameters but once that is worked out, I can get solves in 100ms!
  • The power consumption of the eFinder LIte is so low it can be powered via the USB cable connected to the Nexus DSC port.
  • A really simple solution. One assembly and just a single cable to the Nexus DSC.

A busy Spring

As the nights get shorter up here at 51deg N Latitude, the observing season finishes. Two good star parties (Kelling Heath & Haw Wood Farm) allowed me to test some new ideas.

Quite a few others are building eFinders and ScopeDogs, and so quite a lot of time has gone into supporting their builds and commissioning. Much of this is helping people up the learning curve, but also a lot is overcoming faulty hardware - buck converters and ttl-2-usb adapter cables have been amongst the worst offenders. The moral is dont buy cheap, or you may well have to buy twice (at least!) and spend a lot of time fault finding.

I’ve finally produced a ScopeDog that doesn’t use encoders (or a DSC at all). I’m calling it 'ScopeDog Lite’. I was not optimistic at first as to how it would work in practice, but with the stunning fast solve time of the Pi5, its actually rather effective.  Basically the ScopeDog uses motor steps to keep tabs on where it is pointing, with a plate-solve every so often to keep it accurate. Sounds easy, but it wasn’t and providing a stable wifi link to SkySafari was the most challenging.

I succumbed to the Seestar S50 temptation. I’m not getting into astrophotography but it great for using short gaps in the clouds. When I’m using my 18” it sits on the ground nearby as my little observing companion. I’ve been impressed for what you get and can achieve for the price.

Last month saw the 60th anniversary of Mustang production. Our club organised a massive meet at Brooklands Museum, about 800 amercian cars!

3D Printer Arrives

I finished my last blog with a comment that I might consider getting a 3D printer. Consider I did and gave myself a Christmas present!

After some research I went for a QIDI X-MAX3. It has good reviews and is near the top end of home machines (Qidi describe it as commercial even).  Cheaper machines are OK printing with PLA but this isn’t very durable outside. The X-MAX3 is capable of printing almost any material it seems. Its also big, with a printing volume of over 300mm cubed. 

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Now I have to learn how to use it (The manual isnt very detailed) and learn to design in 3D. First efforts are OK. The eFinder display box I described in my last blog cost £18 and 4 hours to modify. Now I have designed a printed version, each copy costs about a £1 and requires none of my own time.

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