Tutorials » Starry Dave's Window Sill Observatory

PC Control of Orion AccuFocus

Jan 092021

FOLLOW THIS TUTORIAL AT YOUR OWN RISK!!!!!

My astro mount is beside my garage with a PC just inside to control it. I can control the mount and cameras remotely from my home study using Google Remote Desktop – but not my Orion AccuFocus focusers.

I read a forum post (that I can’t now find) which explained how to control the focuser over USB. I adapted it slightly to avoid the need for stripping one end of the focuser cable by adding an RJ10 socket.

Component links: USB Relay – RJ10 Socket

The wiring diagram I used is here. Note that the wires to the socket are soldered to the left and right pair of pins respectively.

To control it, I modded an app I found on the net to give me a selection of timed pulses in both directions. This gives fantastic control for fine focussing.

The whole thing cost less than £10 but means I can now control everything from the comfort of home – or even further afield.

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

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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.

My Garden Observatory

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Feb 282015

Here are some pics of my second observatory which is an HEQ5 Pro mounted on a small table outside my garage. The control cables run into the office in the garage corner and are stored coiled in the empty gas meter cabinet on the wall. The hardest part of making this was drilling a 55mm hole thru the wall for the cables. It only takes a minute to remove the cover bag, install the scope and connect the wires. The mount is on the south-east corner of the garage so it can cover the whole sky except the north-west quadrant. Perfect for solar, lunar and planetary work.

DSSR Error Debugging

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Feb 282015

DSSR started displaying error messages and even refusing to load on some PCs in December 2014. Even my garden observatory PC was affected even though no code had changed. I can only surmise that some Windows update had upset DSSR. Most errors were easy to fix and DSSR 4.10 now has a debug mode and improved error logging that help me fix any future errors.

First off, check that your Windows text size in your Windows display settings is set to the default 100%. DSSR may not start and will certainly not autoguide if it is not 100%.

Next, start DSSR and click the I Agree (debug) button. You will then see a series of boxes with a letter code like A, B etc. Click on the OK buttons and remember the last code displayed before DSSR crashed. If you get as far as the main DSSR window make sure logging is running and then write down exactly what you are trying when you see the error. Close DSSR.

You can then use my software support group to post your results together with the relevant log which should be in your capture folder. I will get back to you in a matter of minutes (or days) with a fix.

DSSR and Windows Text Size

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Feb 272015

We just had some problems with new users which was tracked down to the Windows text size which can be altered in Control Panel>Appearance and Personalization>Display.

Any setting other that 100% may prevent DSSR from starting and will certainly prevent it from autoguiding.

Apparently, a lot of laptops are now shipped with 125% text size out of the box and these need to be changed to 100% before running DSSR. This will also solve problems in other software with text not displaying correctly.

If you have trouble reading text at 100% then use a lower screen resolution which will not affect DSSR.

New Version of MS ICE Mosaic Stitcher Released

Moon, News, Tutorials Comments Off

Feb 072015

Microsoft have just released an update to their Image Composite Editor (ICE). I gave it a quick try on my last set of lunar mosaic tiles and it looks like a much nicer package. In particular, the export to disk is now almost instantaneous. Download the 64bit version here.