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:

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!

Weathering the weather

Astronomy can be a frustrating pastime at times.  The typical British weather we’ve been having lately has been a PITA!  It’s either clear early evening when I’ve just got home from work and winding down with a spot of food, only to cloud over later at around the time I’d think of setting up, or it’s so cloudy at first I abandon any idea of setting up, only to find that by 10PM the sky’s crystal clear!

All the time that Orion’s been in a favourable position for me to image I’ve been unable to get everything sorted out.  I did manage to get a half-decent image of the nebula back in November but any plans of doing a mosaic of the region have been thwarted.  Maybe I’m being a little ambitious.

I may turn my attention over the coming months to more northerly targets (unless I can get some quality imaging time in at the dark site) though some may require considerable numbers of subs to create a decent image.

Today was looking promising, but the clouds have rolled in again, so I shall return to familiarising myself with EQMOD etc.

Accurately setting the “Home” or “Park” position on a Skywatcher EQ5 Pro Mount

Update 18 Jun 2011:

Since I originally prepared this article I’ve found that the steps set out in the Starting from a known position section aren’t necessary.  When the mount is powered on, regardless of whether you choose to start from parked position or not, and irrespective of what position the axes are in,  the positions of AX1 and AX2 shown in UTILITY → SHOW POSITION will be the same.  I’ve therefore removed the steps that are no longer required

It’s been quite a while since my last posting.  In the intervening period I finally got round to acquiring a decent mount, the SkyWatcher EQ5 Pro. The only trouble is the weather’s not been too good andit’s way past 10pm before it gets dark enough for observing!

One element of setting up an equatorial mount is the establishment of the “Home” position. This is where the mount is “parked” at the end of a session. It is sometimes described as “weights down, scope up” and is often the position displayed in adverts. There’s an excellent video tutorial on YouTube accessible via http://www.astronomyshed.co.uk/ (“Complete Setup From A to Z Part 1”) which shows how to establish this position using an HEQ6 mount.

In essence, the procedure uses a spirit level to “level” an axis then rotate the axis by 90^o so that it is then perpendicular. When both the RA and DEC axes have been set this way, the mount is in the correct Home position.

As owners of Skywatcher EQ5 mounts have long accepted, the setting circles leave a lot to be desired, and while it’s possible to use the technique in the tutorial on an EQ5, the inaccuracy of the setting circles means it’s a bit of a hit and miss affair.

The following procedure builds on the technique, using the Show Postition function of the SynScan controller to accurately determine when an axis has rotated through 90^o. Though described for an EQ5 mount, this procedure can be used with any equatorial mount with SynScan, whether factory-fitted or upgraded.

On the EQ5 tripod, one leg is marked N. This is the leg which is pointed North. For the purpose of this procedure this will be regarded as the front of the mount.

It is assumed that the user is familiar with the operation of the SynScan controller and its menus. Navigation to a sub-menu will be described thus:

UTILITY → SHOW POSITION

( Starting from a known position section removed)

Setting the RA axis

1. Stand behind the mount, release the RA clutch and rotate the RA axis until the weight bar is horizontal and to the left. Use a spirit level to check then lock the RA clutch.
2. Switch ON
3. Step through the setup procedure. Note: Setting date/time/location correctly is not required at this, or any other stage of the process, nor is 1,2 or 3-star alignment.
4. Show the position of the axes.     UTILITY → SHOW POSITION
5. Use the scroll keys to change the display so that the axis positions are shown in degrees, minutes, seconds:

AX1=+090^o 00′ 00”

AX2=+000^o 00′ 00”

(AX1 is the DEC axis, AX2 is the RA axis)

6. Set a fairly high slew rate (RATE 8 for example) then use the RA directional key to slew the mount until AX2 is close to reading 90^o. Select a slower rate and carefully slew until the display reads

AX1=+090^o 00′ 00”

AX2=+090^o 00′ 00”

7. Using a fine marker and straight edge, make a mark to enable you to manually return the RA axis to its parked position.

Setting the DEC Axis

1. If you have one, fit a dovetail bar to the puck. This will provide a straight edge to rest the spirit level on.
2. Release the DEC clutch and rotate the DEC axis until the dovetail is horizontal, using the spirit level to check.
3. Again, start off with a high slew rate and rotate the DEC axis until the display indicates the AX1 axis is 90 degrees different to what it was. If your preference is to have the DEC motor to the left, then the display should read

AX1=+180^o 00′ 00”

AX2=+090^o 00′ 00”

If, however, you prefer to have the DEC motor on the right, the display will read

AX1=+000^o 00′ 00”

AX2=+090^o 00′ 00”

8. Using the marker and straight edge make a mark so the DEC axis can be returned to this position manually
9. Switch OFF
10. Switch back on again and step through setup.
11. Choose UTILITY → PARK SCOPE then switch off when prompted

The mount now has its axes accurately positioned and parked.

Yet another missed eclipse

I had such high hopes.  I’d imagined being able to see part of the Lunar eclipse of 21st Dec 2010 from my office window which looks in a westerly direction.  I even took my DSLR in to work just in case. Result? Total cloud cover!

I then heard of the partial Solar eclipse of 4th Jan 2011, so I thought I might stand a chance of seeing (if not imaging – I didn’t want to ruin the sensor!) the eclipse at sunrise.  I should’ve known better!  Whilst there was a gorgeous red sky over to the east there was also an inconvenient bank of cloud that refused to move! *sigh*

Moon and Jupiter

Beautiful though the moon is, it makes imaging a nearby planet rather awkward.  If you set exposure to cut down the Moon’s brightness, you lose the planet.  If you set exposure for the planet, you over-expose the Moon!.  The following image is a bit of a fudge, really.  I took the exposure up as high as I could without washing out the Moon then generated two images from the original, one with exposure increased further to show up Jupiter, the other with it reduced, to show the Moon better.  The two images were then overlayed in GIMP.

Luna Oh Luna!

Well here we are, one of my first lunar images. Not bad considering it was taken from indoors!

moon 24 Jul 2010 00:54

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Canon EOS1000

75-300mm lens at 300mm

1/100s @ f/13.0

ISO1600

Getting to grips with image processing

First past the post (processing)

Above is a slightly processed version of an image I took on 17th April 2010.  I’m quite pleased with it though it’s not as sharp as I’d like.  I have tried using DeepSkyStacker to process and, while the image in the DSS interface shows quite a few stars (see below) I seem to “lose” them somewhere when using Gimp.  Tweaking some settings when loading the original RAW file into Gimp seems to help, but Ideally I’d like DSS to save a nice sharp JPG image for me to share.

Screenshot of DeepSkyStacker

UPDATE (8th July)

I’ve since found RawStudio for Linux with which I can adjust exposure, contrast, sharpness etc and then export the image as a JPEG or TIFF.  Not only that, I’ve also (via Star Gazers Lounge and Sky At Night Forums) been made aware of a piece of software called UniMap. So far I’ve only scratched the surface but all I can say is WOW!  One of the features of this software is its ability to scan an image and annotate it using information from chosen star catalogs.  As an example, I took the image of the plough shown above and passed it through.  The image is best seen full size to see the labels but I think you’ll find it impressive:

Amazing what Open Source Software can do!