Homemade Filar Micrometer for Double Star Observations !

[Shazzanne1963]

Hi Just wondering if any of you  DIY Astronomers has ever made a Filar Micrometer for measuring double star angular separation 

Or know off any Posts or Articles, in how to construct one !! long shot I know but a Girl has to try 🙂

Edited September 12, 2023 by Shazzanne1963

[Mr Spock]

I wish... I'd love to be able to measure doubles.

[Tomatobro]

There is a paper on 3D printing one see  https://digitalcommons.olivet.edu/cgi/viewcontent.cgi?article=1086&context=honr_proj

Also on Cloudy nights a post on how to adapt a Unitron microscope filar (one on Ebay in the USA)

[Tomatobro]

I guess you were looking for a at the eyepiece solution but I see that the measurement can be made using plate solving and a bit of maths. 

[Stu]

Welcome to the forum. Not sure if these are any used but here goes:

https://sab-astro.org.br/wp-content/uploads/2023/04/EvaldoBezerra.pdf

https://journals.co.za/doi/pdf/10.10520/AJA00248266_4332

 

 

[Shazzanne1963]

Many Thanks to all who responded to my question,  I have some good idea's  now how to proceed Thanks 

[Stu]

24 minutes ago, Shazzanne1963 said:

Many Thanks to all who responded to my question,  I have some good idea's  now how to proceed Thanks 

Do let us know how you get on. There are plenty of double star fans on here who would be interested I’m sure, myself included 👍

[quesne]

I just came across your thread, and I thought I would chime in since I'm in the process of adapting a microscopy filar micrometer for use on my ETX-125.  Here is one of my posts in a recent thread on Cloudy Nights that discusses that project (hope it's OK to post that here :-)  And this is an article from December of 1999 by a South African astronomer that may be interesting to you.  It is about his/her project to design a filar micrometer for double star observation.  I look forward to read any updates on your efforts! 🙂

[quesne]

Just a quick note as I noticed the post by Tomatobro earlier in this thread which mentions the Unitron filar micrometer.  I have three flawlessly operating filar micrometer eyepieces: Unitron (Japan), Bausch and Lomb (U.S.) and Bleeker (Netherlands).  In this post on Cloudy Nights, I review the issues with the Unitron filar and scale setup for astronomy.  In short, the reticle orientation and optics are excellent for microscopy, but the unit is severely handicapped for astrometric measurements.  The Unitron has an "X" shaped moving reticle set at 45 degrees to the horizontal scale, and a 0 to 8 scale toward the top of the FOV (diagram below and a detailed explanation here).  The 45 degree orientation makes it pretty useless for aligning a telescope with the NCP, and exceedingly inconvenient (being kind here) for double star measurements.  The 0-to-8 scale does not help either way.  The only application for which I would consider it adequate is lunar geological measurement.  An Olympus micrometer that I found on-line but did not ultimately buy has the same problem, and Zeiss also produces filar micrometers with the same or similar scale setups.

 

So....what's my point?  (I frequently have none....that's part of my charm :-)  Actually, I am just trying to add to the body of knowledge and help my fellow DIY astronomers.  To summarize: Unitron, Olympus and Zeiss filar micrometers are not well suited for conversion for taking astrometric measurements (please see my clarification notes below).  The Bausch and Lomb and Bleeker micrometers are much better, providing a 0-to-10 scale at the center of the FOV, and a filum set at 90 degrees to the horizontal.  BTW - I have also run into problems that have nothing to do with the above filum "orientation" issue.  Two of the micrometers I have are unusable in spite of being perfectly capable optically.  Those problems range from cockeyed scales to out-of-calibration dial gauges to other vintage hardware related issues.

Edit: 24 Feb, 2024 - Since I originally posted this, I have acquired a Unitron W10 micrometer as well as a Zeiss K15.  I also tested a Nikon 10x micrometer.  The filum and scale setup on the Unitron W10 is absolutely perfect for astrometry.  It has an intuitive scale along the midline (horizontal) axis of the FOV, including a long vertical line at the center.  The filum is an identical long vertical line that can move from one horizontal extreme to the other (this setup is almost identical to many astrometric filar micrometers).  The Nikon reticle setup is exactly the same as the Olympus.  Both are very poor choices IMO.  The Zeiss reticle is interesting, to say the least.  It is far too complicated to describe here in words (I'll provide photos one of these days).  I believe, however, that it may be a good choice.  I will continue to star-test it, and post my results here in the near future. 

Edited February 25 by quesne
Added notes regarding the Unitron W10 and Zeiss K15 micrometers

[Tomatobro]

I raised this subject on the Sharpcap forum as a possible feature for the future. Robin was quite interested in the subject and would look into it.

[quesne]

31 minutes ago, Tomatobro said:

I raised this subject on the Sharpcap forum as a possible feature for the future. Robin was quite interested in the subject and would look into it.

Thanks very much, Tomatobro.  Please forgive a newbie question, but what is the Sharpcap forum?

Edit: Never mind....I just did a search and I found it!  https://forums.sharpcap.co.uk/

Edited January 24 by quesne
Added comment regarding SharpCap forums

[quesne]

Hi Folks: The filar micrometer adaptation project I have been working on is coming along pretty well.  I just thought I would provide a link to my recent post on CN.  Several of my CN colleagues also have updates in the thread that may be of interest.  Clear skies 🙂

[quesne]

Hello All:  

I just wanted to follow up with an update on my project status by way of some recent posts that I made on CN.  If you’ve read my previous posts, you know that my initial desire was to develop a “dark-field” solution (i.e. delivering illumination in a perpendicular direction to the long axis of the telescope so as to minimize longitudinal scatter from the light source).  A quick review of my posts reveal that my dark-field experiments were not very successful.  Planting micro-sized LEDs in the body of a micrometer was not terribly difficult.  However, the optical geometry of the components – and the room available and obstructions within the micrometer bodies themselves – made it very difficult to “light up” the slides etched with the filum and reticle scale.  I have not given up totally on a dark-field solution, but I realize that it likely requires drilling small holes in the micrometer body and placing LEDs at optically strategic locations.  For the moment, I’ve moved on to a "bright-field" model that works reasonably well.  I would like to play it out through some live star-testing and ultimately (I hope) real-world astrometric measurements.  Instinct tells me, however, that very dim DSOs and double-star pairs may get washed out by even the dimmest of bright-field illumination.  When (or even "if") I get to that point, a dark-field solution may be the way to go. 

My methodology for adapting a microscope filar micrometer for astrometry is pretty straightforward.  There were four overarching goals/requirements, namely that the adapter will:

1.  Function independently of the choice of telescope.  By that I mean that it should be easily portable from my 70 mm refractor, to my 90 mm MCT, to my 125 mm MCT, to my 200 mm Dobsonian.  This requirement more-or-less dictates a focuser-based solution, and excludes a pre-objective solution (such as an LED attached to the dew shield or spider vanes, etc.)

2.  Include an integrated 360-degree protractor to allow position angle measurements of double stars, comet trajectories and magnetic field orientations of sun spots and solar prominences.

3.  Function with any one of a number of micrometers in my library.  Some of them have differences that need serious design considerations, such as novel barrel attachment configurations, differing nosepiece length, etc.  Some of the differences are quite minor but may still need attention (the microscope barrel set-screw locations and clearances come to mind here).

4.  Work equally well with my homemade 1.25” astrometric reticle eyepiece or any other micrometer microscope eyepiece that I want to use.

The current working model that I have for an illuminator is based on an inexpensive ($5 USD) Barlow body from SurplusShed.com.  It works quite well.  Though I may well upgrade the Barlow platform once my design has been perfected 🙂  Building it required relatively inexpensive hardware easily found on eBay, Amazon and/or the local hardware store (micro-LEDs, a small potentiometer, resistors, cyanoacrylate tape, soldering tools, etc.)  For anyone interested, please have a look at my detailed posts (links below) and provide comments here.  I would also be very interested to learn about the direction you chose to go in, Shazzanne1963, and any progress you’ve made.

Clear skies 🙂

Protractor Models (very preliminary)

Illuminator - Version 1

Illuminator - Version 2 (to address a few design flaws)

Edited March 6 by quesne

[quesne]

Just wanted to post a couple of star test updates for my illuminator.  Here are some photos and comments from my first field test.   And this was just last night at Valley Forge National Park.