I’ve been working a lot on the Drifter, but have not been posting updates.
Goodbye 6″, Hello 8″
After a lot of deliberation, I’ve bumped up the mirror size to 8″ (200mm). 6″ mirrors + 2″ optics would have presented a stunningly wide true field of view (TFOV), but at the cost of too much light loss. 8″ mirrors will still provide 2.2 degree TFOV with the 34mm Siebert eyepieces, but substantially more light. 8″ * 1.4 binocular summation factor means equivalent light gathering of an 11″ mirror. (Some estimates put BSF as high as 1.7, equivalent to almost a 14″ mirror.) We trade the full view of the East and West Veil Nebula for significantly more brightness and detail on all objects. I think it will be a good trade.
In order to keep the form factor small, the primary mirrors have been moved closer together. This increases the angle of the tertiary assemblies, reducing the amount they have to turn for IPD adjustment. The secondary cages have been reduced to the bare minimum as arcs rather than full circles. Mel Bartels recommends tightening secondary cage diameter, so this has been done as well. The result is a width of 20″ and depth around 17″. It will still fit neatly in a car seat, and even with the increased mirror weight, it will still come in under 40 lbs. fully loaded with mount and eyepieces.
Electronics – Augment Platform
Visual astronomy for me is a chance to unplug from electronics altogether and enjoy the sky, the cool night air and being outdoors. So to this point I’ve avoided electronics aside from laser collimators and illuminators. But I have to concede the utility of certain things that require juice and buttons.
For instance, now that the weather is cooler, I’ve been effectively prevented from observation by dew. After cruising the market for dew controllers, I’ve come to the realization that many features useful for basic visual astronomy 365 are add-ons, each of which creates another tangle of cables and battery requirements. They’re also either manual-control with buttons/knobs you have to use in the dark, or use a laptop interface, which means dragging along a laptop and dealing with a huge, bright screen for the privilege of using a Byzantine interface.
I’m an impatient, unmethodical person by nature so my cables are always loose/tangled, my batteries are never full. The thought of adding a bunch more stuff to yet another bag to remember, more batteries to remember charging (or lugging around a 50 lb car battery), increasing setup/breakdown time and resulting in a telescope that looks like a Borg on a bad hair day (the Borg aliens, not the telescopes)… none of that appeals. I see people’s astrophotography rigs and the cringe is intense. (Love the photos though, keep those coming please!)
No, things should be built-in, and use a standardized interface. Things that are a pleasure to use get used more, and they make the experience itself more pleasurable.
The Drifter would benefit from a few devices, especially with thicker, larger-aperture mirrors.
Dew heaters allow you to observe in cold weather. A binoscope has up to six optical surfaces that need heating (eyepiece, tertiary, secondary x2).
Primary fans cool down the full-thickness mirror quickly in the warmer months so those quick peeks at Jupiter with the kids aren’t a wobbly, blurry mess. Front-mounted fans also will prevent dew on the primary mirrors during cold weather.
Push-to is a nice compromise for those who don’t want to use GOTO. Just as Google Maps prevents me from ever learning how to get around Portland when I visit, GOTO would prevent me from ever learning the sky. Learning the celestial map that has existed above every human ancestor’s head to me is as important as actually seeing the stuff up there. But I have to admit, sometimes it would be nice when I have a passing curiosity about an object to be able to find it in a few moments. These days, the sensors for determining orientation can be purchased together on a single breakout board that fuses the input from three sensors into one vector for about $25. This replaces the need for cumbersome ALT and AZ encoders. A phone can already do this via Skeye but I avoid my phone at all costs when at a dark site.
Equatorial table provides tracking to Dobsonian mounts without requiring any alignment procedure beyond pointing it very roughly toward Polaris when you start. Computer control would allow an automated audio/visual alert when the table was approaching the end of its track as well as a safety cut-off.
Sky quality meter lets you know what you can expect to see. Even the most casual visual observer who keeps no notes whatsoever can benefit from knowing sky quality. With the other hardware already in place to handle the other features above, adding a light sensor is a trivial expense.
All of this can be controlled with a $35 Raspberry Pi computer connected to various sensors and outputs, all encased in one box, connected to one 12V LiFePO4 battery. A small dimmable screen provides plenty of info, a touchless gesture tracker lets you control the interface without ever touching the telescope. A couple hundred bucks worth of parts should do it (though the battery itself won’t be cheap).
Development on this platform–I’ll call it Augment for now–will begin once I’m done with the Drifter. Though the Drifter will be built with Augment in mind.
If someone would like to beat me to this, please do. I think it would be marketable for just about any scope by offering a few different form factors and software configurations. If someone is interested in working on this with me, get in touch. I know nothing yet about electronics or Pi (or Py), but bring 20 years of UI design, plus advertising and marketing experience.