Holoholo – A 10.1” f/4.5 Travel Telescope

Living in the islands provides excellent observing for an amateur astronomer such as myself, but there are drawbacks. I do miss the large star parties, getting together with hundreds of other observers to see other telescope setups, to learn, and to share the sky.

The 10" f/4.5 travel scope Holoholo
The 10″ f/4.5 travel scope Holoholo

Thus I have made a habit of traveling to the mainland once in a while to attend one of the larger star parties. This year I will again attend Oregon Star Party. It has been a while, the last time was 2017, the year of the total solar eclipse.

Traveling from the islands to a star party makes it a challenge to bring a large telescope. Last time I borrowed an 11”, not a bad solution, it worked, but it was not my ‘scope. This time I was determined to realize a long considered idea, to build a substantially sized travel telescope. Thus Holoholo was designed and built, a 10.1” f/4.5 travel ‘scope.

Continue reading “Holoholo – A 10.1” f/4.5 Travel Telescope”

Oregon Star Party 2023

A large star party is an experience worth seeking out… Hundreds of people, hundreds of telescopes, all under a dark sky.

A large dobsonian set up at Oregon Star Party 2023
A large dobsonian set up at Oregon Star Party 2023

A star party is a meeting of geeks. Technical talk of optics, electronics, and fabrication techniques like 3D printing abounds. In the afternoon and evening you will find small conversations in the shade, pull up a chair and join the discussion.

The plan was something I had executed successfully before… Fly into Portland, spend some time with my folks, then borrow the family camper for the trip out to the Ochoco Mountains for the star party.

Continue reading “Oregon Star Party 2023”

Using the ZWO ASI2600MC Camera

Due to a plan that failed I ended up with a borrowed astro camera for a couple weeks. Since I have it I may as well play with it a bit.

The Orion Nebula M42
The Orion Nebula M42

The camera is the ZWO ASI2600MC Pro, a one-shot color camera specificaly for astrophotography. I have the ASI1600MM Pro a monochrome camera set up with a filter wheel, but have never really had a chance to use one of the modern one shot color cameras.

Continue reading “Using the ZWO ASI2600MC Camera”

A Bahtinov Mask for the TeleVue 76

For some reason I have gotten along without a focus mask for the TV-76. Need to fix that… Done.

A 3D printed Bahtinov focusing mask for a Televue 76mm telescope
A 3D printed Bahtinov focusing mask for a Televue 76mm telescope

Just a quick project, about half an hour to design and four hours printing. First print a pleasing success, a completely functional part.

A Bahtinov Mask is used to get a precise focus, something I wrote about a few years back.

A 3D printed Bahtinov focusing mask for a Televue 76mm telescope
A 3D printed Bahtinov focusing mask for a Televue 76mm telescope

For this mask I used a public bit of OpenSCAD code from Jens Scheidtmann to generate the mask pattern, just tuning it for the correct sizing and performance with the TV-76. I added my own version of the support collar, making it a bit neater with fillets and properly sized to slip over the TV-76 glare shield.

You can download the SLT file for the mask from Cults3D if you need to print your own.

The part is one of a half dozen parts I have designed and printed over the last few weeks to reassemble the photo rig. A new guide camera mount, a mount for the ASI Air computer, a new glare shield for the guider, etc., etc… The utility of 3D printing a game changer for me.

A Simple Helical Crayford Focuser

How simple can a focuser be?

This has been a bit of a design challence for me… Just how small, how simple, can I make a focuser and yet still provide excellent usability. My latest Helix 1-14 design is my best yet.

A simple helical crayford telescope focuser
A simple helical crayford focuser

As my 3D printer design skills improve I applied lessons learned and the unique capabilities of an FDM printer to the problem of a focuser. After a bit of a journey I have arrived at a design I can consider finished. Is it the final design? I may tinker some more, but I am satified for the moment.

The design is based on a few ideas from here and there, products I have seen or used, internet postings from others faced with the same challenge. I am not one for just printing someone else’s design, I rarely do that, I want to do my own, and maybe make it better.

Continue reading “A Simple Helical Crayford Focuser”

Testing a Mirror

As I have observed lately, most of the small telescope mirrors available right now are out of China, most of those produced by one company, Guan Sheng Optical or GSO. If you want a small mirror, say a 6″ or 8″ mirror, there is not a lot of choice, the mirror makers in the US generally do not do anything smaller than 10″.

Foucault knife edge test
A textbook Foucault knife edge test image on a 6″ f/4 mirror

The GSO mirrors range from decent to pretty bad, with no way of knowing what you will get when you order, just luck of the draw.

But how do you tell?

Continue reading “Testing a Mirror”

A Universal Afocal Adapter

A couple weeks ago at the volcano I let quite a few folks take imagery of the lava using the afocal technique, simply holding the phone up to the eyepiece. This works rather well as the phone uses a lens much like the human eye, about the same aperture.

Shooting afocal with an iPhone and the TV-76mm 'scope
Shooting afocal with an iPhone and the TV-76mm ‘scope

The only real issue is holding a phone in just the right spot. Folks wanted video, but holding the phone steady is a real challenge. I had thought of making something to do this many times, last weekend I did it.

A session of playing around in 3D CAD resulting in a couple bits of clever plastic printed with the 3D printer… Done.

There are commercial solutions for this available, quite a few actually. But most of these are intended to adapt to a single phone, using some sort of clamping arrangement that you have to setup for a particular phone. I envisioned something that was more universal, quickly adapting to any phone.

The method I chose was a sliding magnetic platform that holds the phone. Just a simple shelf actually, set the phone on it and slide until you get it lined up. The base piece is printed with a recess into which a steel plate is set. The slider has three 8mm x 2mm neodymium magnets to securely grab the steel plate.

It took a bit of work to cut and file the steel plate to neatly fit the base, a bit of inlay work. Otherwise making the piece is quite easy. The only design issue is that this adapter is setup to fit a single eyepiece, a Televue Panoptic 27mm, and cannot be easily adapted to others.

The 3D CAD files are linked below. I have included the SCAD source file to allow tinkering with the design, possibly adapting to a different eyepiece. Both parts should be printed with support on, the pockets for the glued bits will have to be cleaned out, the resulting rough surfaces just right to recieve epoxy.

Afocal adapter 3D CAD files

At the Keanakakoʻi Overlook I was able to test the adapter with a variety of different phones, both iPhone and Android, graciously lent to me for my experimentation. OK, the owners may have wanted a few lava photos. There was no difficulty using the adapter other than a moment or two needed to line up the camera with the exit pupil of the eyepiece. The result was more than a few smiles.

A 3D Printed Finder ‘Scope

I wanted a smaller, lighter finder ‘scope for the Astrola, and I wanted right angle to stop straining my neck!

3D model of the 40mm finder ready for printing
3D model of the 40mm finder designed in OpenSCAD

I have been using a big Orion 9x60mm finder on the Astrola, the only telescopic finder ‘scope I have among the Telrads. It is nice, with a bright image that shows many faint fuzzies. It is also huge, and very heavy, it is also straight through, requiring one to crane your neck around to view through it on the Newtonian ‘scope.

A small, lightweight finder was in order, a perfect project for a newly arrived 3D printer.

Continue reading “A 3D Printed Finder ‘Scope”