Starry Dave's Window Sill Observatory

When Galaxies Collide

Uncategorized Comments Off

Mar 072017

I made this simulation a few years ago in my StarryOrbits gravity laboratory app. It uses a simplified model of the galaxies with the core stars in red or blue and the halo stars in yellow or green. Newton’s laws of motion are then used to predict what will happen in the future. The simulation repeats a few times so you can watch it properly. What is interesting is that the 2 galaxy cores stay mostly intact even after they have passed thru each other a few times. It is actually better to watch it in StarryOrbits because it has a 3D viewer that lets you rotate, pan and zoom while the animation is playing. Great to have a couple of galaxies on your PC to play with.

Unfortunately, changes to Java security policy means I can no longer distribute the original StarryOrbits. However, I am looking at rewriting it to take advantage of modern multicore CPUs and GPUs.

M42 Guided by DSSR

Deep Sky Comments Off

Feb 282017

Here is my latest M42 captured with my Canon 1100D thru my Nexstar 4SE at prime. I used an old 3″ Mak to guide but found the usual star guiding apps could not lock on the stars. I then switched on DSSR and used it to guide right thru the 3 hour session. Stacked in SkippyStak and processed in StarTools.

Click for full size image

M42 using Nexstar 4SE

Deep Sky Comments Off

Feb 112017

This was shot with my Canon 1100D looking thru my Nexstar 4SE at prime. Stacked in SkippyStak and processed in StarTools.

99 Tile Lunar Mosaic

Moon Comments Off

Feb 112017

Just shot this on the 10th February with my 1/4″ DMK camera and DSSR’s automatic mosaic module. Stacked in Avistack, stitched in ICE and post processed in Krita. Click to see the full size image.

Below is the DSSR mosaic preview window that lets you monitor mosaic progress. The blue tiles were sky which DSSR automatically skipped to save time – total time taken was 45 minutes. The Moon is egg shaped here because I used a vertical overlap of 50% and a horizontal overlap of 30% to ensure a good stitch in ICE.

Email Scam / E-Mail-Betrug

Uncategorized Comments Off

Aug 112016

I have just received a bunch of email bounce notices which seen to come from German speaking accounts.

I can assure you that I had nothing to do with these emails and you should treat them as fraudulent.

Ich habe gerade eine Reihe von E-Mail-Bounce-Hinweise, die aus dem deutschsprachigen Raum Konten zu kommen gesehen.

Ich kann Ihnen versichern, dass ich nichts mit dieser E-Mails zu tun hatte, und Sie sollten sie als betrügerisch zu behandeln.

Mercury Transit 2016

Planets, Solar HA Comments Off

May 122016

I was very lucky during the transit because an early morning haar burned off just before the transit and we had mostly clear blue skies above Inverness, Scotland for the rest of the day. This let me capture most of the transit until the Sun sunk below my roofline. Here is the animation I produced from the results (some jerkiness is caused by occasional clouds).

You can see the transit near the end of this compilation video.

Equipment and Software Used

Coronado PST solar scope
HEQ5 Pro mount
PowerMate 2.5x barlow
TIS DMK21 camera
EQMOD for mount control
DSSR for autoguiding and video capture
AviStack for video stacking
DVS for animation
Pipo X7 PC for mount control, video stacking and animation

Technique

I had intended to use my PST at prime focus to capture the transit but I changed my mind just after the start and zoomed in with my barlow. Mercury made a perfect autoguide target for DSSR and I only had to guide manually when a telephone cable went in front of the Sun. DSSR automatically recorded 669 consecutive videos, each 30 seconds long which were batch stacked and processed in AviStack.

I used DVS to stabilise and animate the AviStack images and add the clock, text and scale Earth. The scale Earth threw me for a while because Mercury is only 38% the size of the Earth and it looked far too big when I added my standard scale Earth. It took me a while to realise that Mercury and the Sun are at different distances from Inverness so I added 2 scale Earths.

I love pushing the limits of low cost astro equipment so I am delighted that my £70 Pipo X7 PC was able to act as my observatory workhorse.

Easy Peasy Horizon to Horizon Milky Way Mosaic

Deep Sky, Tutorials Comments Off

Oct 092015

I have always admired the fantastic Milky Way mosaics that you see on the web and here is how to try it for yourself.

Click for HD version. Original mosaic was 11,440 x 2,800 pixels.

Field Work

I shot this in Scotland in October using only a fixed tripod and a Canon 1100D with the stock 18-55mm lens. At this time of year, the Milky Way passes close to the zenith which makes this method easy to use. You could adapt it for other dates by tilting your tripod head so that it follows the Milky Way as you tilt the camera.

First, get to a dark site with clear views of the Milky Way from horizon to horizon. Set your tripod level and take some test shots to test focus and exposure. I set the lens to 18mm, wide open aperture, ISO 6400 and exposure to manual at 30sec.

Now aim at where the Milky Way crosses one horizon and take your first shot. Tilt the camera up about 15 degrees and take another shot. Repeat until the camera is pointing straight up which should give you a series of 7 shots or thereabouts. (The angle is not too important – you just need a good overlap between shots. Now turn your camera round to the other horizon and repeat for a second series.

Shooting all the images took me about 10 minutes.

Create the Mosaic

I used the amazing and free Microsoft Image Composite Editor (ICE) to stitch the mosaic. Start by loading the first series of images (I used the raw .cr2 files). Then click Stitch and select the Transverse Mercator projection when it has finished stitching. Click Crop and then No crop and then click Export and select the .PNG image file option. Click Export to disk and select where to save your first half of the Milky Way. Repeat for the second series of images which will give you 2 mosaic halves like these.

IMG_5498_stitch no crop

IMG_5491_stitch no crop

You can now use ICE to join these 2 halves to make a complete mosaic. Load them in ICE and Clicking Stitch will give you a result like this.

We need to rotate this a little to bring the Milky Way vertical so insert a value of 10 for Roll to give this.

You can now click the Crop button and adjust the crop window to suit like this.

You can now export this image and edit it in your favorite image editor.

You can also load both sets of original images in and let ICE stitch them all together. Below is how this looks using the Fisheye projection and colors tweaked in Gimp.

Not bad for 10 minutes of field work?

DSSR5 Scan Stacking Challenge

Solar HA, Tutorials Comments Off

Jul 082015

I have been working with Sylvain Weiller to implement his drift method of video capture into DSSR5 beta. This method moves your scope around a target feature while recording video. Stacking apps can integrate this video to produce an image of the whole scanned area. This effectively quadruples the area of your imaging sensor and also removes the dreaded Newton’s rings.

DSSR5 allows you to scan along single axes (right ascension or declination) or dual axes with the option of backlash take up. The dual axes mode moves around a rectangle 1>2>3>4>1 with a sawtooth edge profile (to eliminate stacking artefacts) like so:

Dual Axes Scan Path

We are still working out the best processing workflow to handle these scans so I have uploaded a full disk and detail scan (zipped AVI in Y800 codec) so others can experiment. Please let me know thru my user group or other groups I posted this link to on how you get on and what worked for you. The files are here:

Full disk scan (1.57Gb)

Detail scan (1.37Gb)

Sylvain managed to process these files in Registax 5 before he went on holiday and his results are below. Notice the extra imaging area compared with the normal 1/4″ ccd field of view and the total absence of the Newton’s rings which were very obvious in the detail video.

Click for full size image.

Update July 13th

I had a go myself using AviStack and here are my uncropped results. Very close to a good result but I need to close up the missing pixels.

Click for full size image

Andrew Cool of SkippySky noticed an interesting result from the AviStack processing results. The Frame Shift graph actually captures the scanning path with sawteeth very well. It also reveals that my mount needs to be more accurately aligned because the red and blue lines should end on zero.

disk dual_as2_diagaligns

Charting DSSR Autoguider History

Tutorials, Uncategorized Comments Off

Jun 202015

SmarTrak is DSSR’s helper that steps in to guide your scope when the guide taget is lost due to cloud or other obstructions. I seem to have broken it in DSSR5 and I have added some logging features to help me fix it. These can also give you an insight into how DSSR is controlling your scope.

When DSSR loses the guide target it logs the guiding history like so:

08:22:17.838 Target lost – SmartTracking
08:22:17.839 SmartTrak totalTms:4638563 ppmsH:-0.01001258 intH:-49937.2 pH:-500.0 ppmsV:-0.03671094 intV:-13619.9 pV:-500.0
08:22:17.839 ,0001,6834,0,0
08:22:17.839 ,0002,7170,51,305
08:22:17.839 ,0003,7668,103,508
08:22:17.839 ,0004,8266,155,711
08:22:17.839 ,0005,8662,-310,-1322
08:22:17.839 ,0006,65300,-310,-1220….. etc for all stored guide history points.

Each red line contains the log time, point index, time in milliseconds since the last guide pulse and the pulse times in milliseconds for the RA and declination axes. You can copy and paste these points into a spreadsheet and chart the guide pulses in each axis against time. Below is the RA chart for one of my sessions.

Click for full image

This shows the plus or minus RA guide pulses have a recurring period of about 10 minutes. I don’t use periodic error correction on my HEQ5 Pro but this chart shows that I probably should. When I play back my session videos I can clearly see the target moving back and forward in RA around a mean position during SmartTraking.

SmartTrak applies the mean pulse (-50ms red dotted line) but you can see that the polynomial trend line runs from -20ms at 78 minutes ago to -70ms when SmartTrak kicked in at right on the chart. This suggests that I need to cut my number of history points down to cover say just 2 cycles or 20 minutes. This will give a better mean pulse time for SmartTrak to use.

The fact that the mean line is not at 0ms suggests that my mount still has an alignment error. You can see a similar alignment error in the declination chart below.

Click for full image

This shows that all the guide pulses are negative and there seems to be a much shorter periodic error. The mean pulse is -175ms but the polynomial trend is at -150ms when SmarTrak kicks in at right. Again this suggests that fewer history points are needed to give a more accurate mean value.

The above charts have been very useful to help me see what DSSR is doing during autoguiding and I hope to have SmartTrak fully operational soon.

You can try this out for yourself by changing your screenshot interval to 5 seconds, turning on logging, checking the SmartTrak box and then guiding for an hour say. Then raise the minimum guide similarity to 999 to force SmartTrak to kick in and leave it running until the target leaves the field of view. Make a session video as per Appendix E of the manual and scrub it back and forward in VirtualDub to see how SmartTrak is faring.

You can then use a spreadsheet to construct the charts above. I used the free LibreOffice Calc spreadsheet for mine.

Earth Overlay Size in DVS

Solar HA, Tutorials Comments Off

Jun 202015

The graphic below shows how to calculate the size of the scale Earth to use as an overlay in DVS animations.

Click on image for full size.

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