Making a solar filter

With a solar eclipse coming up on 20th March 2015 I’ve finally got round to making a solar filter for my 72mm refractor. I’d looked at purchasing one but one of the right size was never in stock.  I wanted something sturdy rather than made of card and I hit upon the idea of using a CD/DVD “cake” as the main body (with a large enough hole cut in the top) and sandwiching some solar film between two rings cut from the protective discs you get at the bottom of the “cake”.  I also made a pair of filters for my binoculars out of cardboard (cereal carton).  This first image shows the body of the “cake” with a hole already cut into it, and the two protective discs. Also seen are a 12″ steel ruler, radius cutter, pair of compasses, caliper, solar film (in envelope under ruler) and “invisible” photograph mounts (which are used to attach the rings to the film)

A 15mm diameter hole (the size of the central hole in the discs) was drawn on an off-cut of fibreboard (ply would have been better) and one of the discs positioned over it and fixed in place with screws. The radius cutter was set to a radius 10mm less than that of the discs and its pinpoint located in the same hole created by the compasses

Here we see both rings completed:

Photo mounts are attached around each ring:

A square of solar film is cut just larger than the rings and, having removed the backing paper from the adhesive mounts, the film is carefully sandwiched between the rings:

The rings are then fixed in place inside the modified cake, and here’s the finished article after the main body has been painted (prior to the filter being added!):

Filter attached to telescope ready to image the eclipse:

A cropped image taken using the above:

DTB or not DTB… Part II

Well it’s taken me a lot longer to post this than I’d originally intended. Partly because of time (or, rather, lack of it) and partly because since my last posting on this topic I’ve re-installed Linux on the laptop and had forgotten most of what I did previously! Fortunately I’d taken a backup of things!

(edit 2 may 2014: Even longer than when I first started writing this part as I’ve been through a number of changes in Linux since!)

In part 1 I said how the files for a recording are held in a directory (“folder” in Windows parlance) such as

~dvr2010090102353301.rec

Within this directory are a number of files with the suffix .trp These files need to be combined.  To do this I use a piece of software called ProjectX available from Sourceforge here:

http://project-x.sourceforge.net/

Though ProjectX can combine the files into a single video file, I found that the audio and video were out of sync.  The solution I found was to select and option in ProjectX to aplit the audio and video components then use the mplex command in Linux to re-multiplex them into a single file. For Ubuntu/Mint (and probably Debian) mplex is part of the mjpegtools package which is installed with the command

sudo apt-get install mjpegtools

Stage I – ProjectX

After the ProjectX ZIP file has been downloaded, unzip it then cd into the directory:

cd Project-X_0.91.0

Then start the program with the following command:

java -jar ProjectX.jar

You then need to load all the .trp files.  The following image shows the icon to select (arrowed). A file picker pops up from where you select the required files.

ProjectX file picker

 

 

 

 

 

 

 

 

Once the files have been selected, make sure you specify a suitable location for Output directory then click on prepare >> and select de-mux:

ProjectX Process window

 

 

 

 

 

 

 

 

Finally, click on the green arrow to start the process.  You may get some warnings appear but I’ve found they can usually be ignored.

In the output directory you will find a number of files, for example:

dvr2010111020022501.rec00_log.txt
dvr2010111020022501.rec00.sup
dvr2010111020022501.rec00.sup.IFO
dvr2010111020022501.rec00.mp2

The next task is to use mplex to create a .MPG file which will have the video and audio in synch:

mplex -f 8 dvr2010111020022501.rec00.mp2 dvr2010111020022501.rec00.m2v -o MyProg.mpg

The resultant .MPG file can then be played or, if desired, written to DVD using DVDStyler but that, as they say, is another story!

 

 

 

 

The value of preparation (and what happens when there’s a lack of it!)

A tale of expectation, apparent disaster, elation, more expectation, annoyance, disappointment…

Saturday

(expectation)

Evening was looking promising for so astronomy/astrophotography, so once it was dark enough for me to see Vega, Deneb, Altair and Polaris with the naked eye I started setting up.  I spent about 30 mins getting the tripod level and pointing North then attached EQ5 mount and got that polar aligned.  For some bizarre reason I’d decided not to extend the tripod legs, so kneeling down to peer through the polarscope made the old knees creak a bit. Anyway, I digress. Once the mount was aligned, I hooked up the controls and connected to my 88Ah leisure battery.  I then attached the telescope to the mount, fitted a 20mm eyepiece, removed the end cap from the ‘scope and was ready to go…or so I thought!

(apparent disaster)

I switched on and went through the setup procedure then decided to use Caph (for those of you who don’t know, Caph is the top right hand star in the W of Cassiopeia) hit Enter and…horrible screeching sound accompanied by the scope moving in the wrong direction!  Pressed ESC to stop the movement and checked that I hadn’t got cables mixed up (unlikely as I normally leave them connected when the mount’s not in use).  Nope, cables OK so try moving the mount with the direction keys. Movement OK in Right Ascention (RA) but attempts to move in Declination (DEC) produce the screeching noise.   Time to do a bit of fault finding…

• Removed cover from DEC motor and tried movement…SCREECH
• Remove motor from mount and try movement…SCREECH
• Remove transfer gears and try…no SCREECH but motor shaft oscillating back and forth.
• As RA movement was OK I then connected the cable from the motor control box (which normally connects to RA IN on the mount) to the motor and tried the RA keys….Motor works fine!
• Reconnect the cables in their normal positions and try DEC movement…oscillating motor.

Time to think… What was different compared to when the mount was last used about 10 days previously?  The only difference I could think of was that I hadn’t put the MC box and Hand Controller back in the large plastic box they’re usually kept in with a bag of silica gel.  Could a bit of dampness have crept in and affected the circuitry (it having been quite humid)?  Possibly.  Anyway, nothing for it but to pack up for the night and take a look on Sunday..

Sunday (afternoon)

(elation)

Got the MC box and Hand Controller out of their box and connected everything up.  Applied power, went through setup and tried movement….

and…..

IT WORKED!

Huge sigh of relief as I’d had visions of going through a process of elimination and possibly having to return the mount to retailer.  I can only assume that damp had somehow played a part.  My elation was tempered somewhat when I checked the weather app on my phone and it indicated it’d be a cloudy night 😦

(more expectation)

Kept a watchful eye on the sky and by 9pm it was looking good, so off I go again…

I double check that mount is working OK before taking it outside…Yes, so set up everything as before.  Apply power and go through setup no problem.  Select Caph as alignment star and the mount slews in the right direction. Now, I normally expect the first alignment to be off-target unless I’ve got very good polar alignment.  The trouble is, although Caph is a bright enough star, when looking through the telescope with the 20mm eyepiece I don’t have a wide field of view, so the alignment doesn’t have to be off by much for the target star to not be in view.  After I spent a few minutes trying to find Caph I decided to try for Vega on account of it being so bright and easier to find.  Finally got Vega in the centre of view then went back to Caph, which appeared almost dead centre in the field of view.  A few minor adjustments then time to get everything else set up: finder/guider (a webcam attached to a finderscope), DSLR and laptop.

(annoyance)

This was the first time I’d used the laptop with mount etc. since re-configuring it earlier in the week.  I thought I’d re-installed all drivers and software but it turned out I hadn’t.  First off the webcam wasn’t recognised so I ended up installing the driver for the camera again (on reflection I may have tried installing the wrong driver previously).  Loaded up PHD (guiding software available from  http://www.stark-labs.com/phdguiding.html) and selected the camera. No error this time and I could see some stars in the image.  I then tried getting PHD to select “EQMOD ASCOM EQ5/6” from the ASCOM telescope chooser but whenever I did so, the OK button was greyed out.  Re-installed ASCOM and tried again.  Eventually got it to work.  Next up the DSLR.  Connected the USB cable and tried opening EOS Utility – camera not found.  Try Backyard EOS – same result.  Change cable to the one supplied with the camera , SUCCESS!  I’m sure I’ve  used the other cable before now without a problem but it did only cost £1 so I shouldn’t expect too much!  Finally I’m ready to go…

Webcam working?  Check
DSLR switched on?  Check
Software running? Check

Right, just need to get focus sorted out…

(disappointment)

Put bahtinov mask on front of scope and looked at Backyard EOS.  Select Frame & Focus…nothing on screen.  “That’s odd.  I should at least see something” Then I look up….complete cloud cover!  I’d spent so much time resolving issues with software/hardware setup I hadn’t paid attention to the sky which obviously had other ideas!  So that was a second night ruined.  Time to pack up and wait for the next clear night (whenever that might be).

Epilogue

All of the above just goes to show how important preparation can be.  Having re-installed the laptop I should’ve taken time (in daylight) to check out all the components.  That way I’d have been able to at least get some images.  The events of Saturday night have shown me (assuming that damp/moisture/humidity was the cause) the importance of taking care of the equipment.  There’s still room for improvement and there are probably ways I can make things easier by adopting a set routine.  Though not mentioned above, my initial photographic target was the ISS as that was due over at 22:09, so once the mount was set up I attached a Vanguard ball head to a small dovetail bar and attached it to the mount then attached the DSLR.  Unfortunately, next door’s conservatory was lit up and causing me problems so I spent time positioning the camera to minimise the effects of light cast.  Time of ISS pass was fast approaching so I set the camera to continuous mode shooting, ISO1600, wide aperture, 10s and waited.  Checked app on phone which showed the pass had started, so I went down the garden to look out for it (garden faces roughly ENE).  Eventually it appeared.  Unfortunately, had I checked the path the ISS was going to take I would’ve found out that, from where I was set up, the pass would be completely obscured by my house and next door’s house.  Had I noticed that I’d have set the camera up on my camera tripod further down the garden – preparation again!