DFTFringe quick start guide version 2 (measuring telescope mirror with Bath Interferometer) Bath Interferometers 2019-06-11 | First video in a series of how to use DFTFringe. This goes over the minimum features you need to measure a mirror.Information on how to make or buy a Bath Interferometer here: gr5.org/bath
How to setup and calibrate this super cheap spectrometer Bath Interferometers 2024-10-11 | I am delighted with this cheap spectrometer from China. It's very impressive and useful for me. LInks discussed in video:where to buy:aliexpress.us/item/3256807055520087.htmlreview of the spectrometer: youtube.com/watch?v=9XIhMJAFPd4software downloadtheremino.com/en/downloads/automation#spectrometertypical modern flourescent emission linesen.wikipedia.org/wiki/File:Fluorescent_lighting_spectrum_peaks_labelled.gifSun absorption lines:en.wikipedia.org/wiki/Fraunhofer_lines
Do you have this issue with your camera? Moiré patterns. Bath Interferometers 2024-07-02 | The interferogram may look fine on this camera display but if I zoom in, things are not well as I actually have 309 very thin fringes. It's caused by the camera's firmware and hopefully not all cameras do this.
DFTFringe Annulus Feature Bath Interferometers 2024-04-22 | Click on a section below or on the timeline to jump to that section00:00 start00:18 Do I need the feature?01:14 Why is it needed?05:58 How to use it?
Unpolished video about the engineering behind choosing a camera lens for your bath Bath Interferometers 2024-02-19 | This crappy vid was done in one take. I hope to do a MUCH better version in the next few weeks. Hopefully.If you are going to use a DSLR I have a great guide at gr5.org/bath but if you want a ras pi camera or some custom camera solution then you need to understand about what is important when choosing a camera lens for a bath.
quickly thrown together DFTF PSI demonstration Bath Interferometers 2024-02-19 | Did this in one take. Don't expect much.
Setting up and using a Bath Interferometer (to test telescope mirrors) Bath Interferometers 2022-08-18 | This video is many months in the making!Once you have your Bath interferometer, here is how to use it. How to get everything aligned, common mistakes, and how to get good interferograms.+Xtilt means right side of mirror is closer+Ytilt means top side of mirror is closer+Defocus means outside of focusHelpful information at http://gr5.org/bath
How to get super clean interferograms from your Bath Interferometer Bath Interferometers 2022-03-05 | all about Bath Interferometers: http://gr5.org/bathstore: thegr5store.com/wpIndex0:00 Introduction1:07 Locating Dust7:56 Cleaning Dust16:27 Other Tricks04:21 in videorotate splitter CW as seen from above, projecting test beam onto paper close to the bath.spots on front of splitter (side closest to mirror) move not at all or move the leastspots on diverger move to the rightspots on laser move to the leftspots on left side of splitter (side of splitter closest to laser) move to the left faster than laser spots7:19 in videowith diverger now on the right beamrotate splitter CW as seen from abovespots on laser move to the rightspots on left side of splitter move leftspots on right side of splitter move right - slightly faster than the laser spotsspots on flat don't movespots on diverger don't move (so distinguish by moving the diverger and those spots won't move - remember - this is counterintuitive)I did some more experiments and learned more about those permanently bad diverging lenses that I said had a "bad coating". I was able to remove the coating. I kept mixing stronger and stronger alkalai (aka base) solutions of Potasium Hydroxide (KOH) and eventually at 10 Molar and soaking for 24 hours (20 minutes did nothing), the coating dissolved. The difference was clear (bright white reflections of lights instead of darker bluer reflections on the coated lenses). But the defects were still there. Not in the coating. Note that 10 Molar concentration is DANGEROUS. So all those lenses that are bad seem to be unusable (about 95% of the lenses). Anyone know a good source for 10mm FL BCX lenses? At under $15 each in quantities of 10.
Fun new tools Bath Interferometers 2022-01-18 | I demonstrate 2 interferometry related interactive web apps that I wrote in the last couple of months. Free. Open source.Links to each web page:http://gr5.org/bath/diagrammer.htmlhttp://gr5.org/bath/fringes.html
ATMoB Clubhouse Bath Training Video Bath Interferometers 2020-01-15 | For members of the Amateur Telescope Makers of Boston club - a tutorial for using the clubhouse bath to test one's mirror.There is a massive amount of duplication of information between thisvideo and the video called "Setting up and using a Bath Interferometer (to test telescope mirrors)". Watching both would be mostly a waste of your time.
Zernike Terms Explained for Telescope Makers Bath Interferometers 2019-09-26 | Zernike terms explained especially as they relate to lenses and mirrors and interferometry and DFTFringe software.Special thanks to Paul Valleli who helped write the text for this video. All mistakes are mine, not his.Chapters00:00 Intro and advertisement00:34 Overall explanation (zernike description, wavefront versus surface error, orthogonality, wavelength, similarity to Fourier Transform)07:39 Spherical Aberration - what is it, parabolic mirror versus spherical mirror10:42 Null feature in DFTFringe - what it does, how it works13:10 Astigmatism - x astig, oblique astig, how to remove it16:10 Wavefront Inversion - when to invert the wavefront17:54 Defocus18:13 Coma
What does an Interferogram represent? A 3D visualization Bath Interferometers 2019-07-27 | I found this great way to visualize an Interferogram so that with practice one can glance at an igram and "see" it in 3D.To create these same visualizations or to alter them (e.g. just change the xtilt or z8 terms and re-run), paste the below code into left window of openSCAD (free and light weight open source software for PC,Mac,Linux), then hit F5 key and wait 3 to 10 seconds. Then you can drag the resulting model around with your mouse.The code to copy into openSCAD is here: http://gr5.org/3digrams.txt
Bath Interferometer Astigmatism Calculator Bath Interferometers 2019-06-05 | DFTFringe has a handy calculator that can tell you how much your Bath beam separation creates astigmatism. This whole topic is kind of moot as if you use DFTFringe properly where you image the mirror in one position and then rotate the mirror 90 degrees and get more igrams in this second rotation, then you can eliminate many sources of astigmatism. Still it's an interesting topic and highlights simulated igrams feature in DFTFringe.
(OLD VERSION) Setting up and using a Bath Interferometer Bath Interferometers 2019-05-15 | Please watch the new version of this video in my channel instead of this older version.
