Joined Jan 12 2010
General Info

62 years old
Kirk Ella
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Brough Astronomy [BLAS]

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About Me

Took up astronomy as a hobby in August 2009.  Started with a SkyMax 127 Maksutov Cassegrain on EQ3-2 mount - with hindsight I should have done a bit more research and taken some advice - the mount has been excellent but the scope has been mostly used for measuring periodic error - long focal length and high f ratio.  Motorised the mount with my own electronics and software to enable tracking in RA.  Have bought a Canon 450D specifically for dabbling in astrophotography, initially with the kit lens (and later the 50mm F1.8, and Sigma 70-300mm F4-5.6 zoom) on the EQ3, and then through a more recent purchase of a William Optics Megrez 72 FD.    Next acquisition was an EQ6 PRO Syncscan mount (Jan 2010).

18th February 2010 added an EQ1 Table Top mount & RA Motor drive, which came complete with a Sky-Watcher Sky Travel 80 achromatic reflector.  Surprisingly pleased with results though, once alignment and sagging sorted out.  Took to South Africa for use with my EOS - worked a treat although polar alignment was trial, error and adjustment.

31st March 2010 - To complete my range of instruments (well not quite) I now have a Sky-Watcher Explorer 190MN (1000mm f/5.2) Astrograph + 2" (x2) Barlow - which I have to confess was a little bit bigger than I had imagined when I sent off for it.  Spent about 10hours making a good solid carrying case for it - see Astro DIY photos.   The MN190 has excellent optics, although it pushes the limits of practicallity with an unguided mount.

Applied to join BLAS at end of March.

17/07/2010 For quick look-see scope I have just got an SW Equinox 80 Pro ED to use with the EQ3-2 now that I have mastered the use of setting circles to sufficient accuracy to place objects in the FoV of the scope.  This means I can, with a bit of discipline and a stopwatch, use the EQ3-2 as a manual goto mount.  The three holes I have made in the grass assist enormously with the speed of accurate polar alignment.

Nov 2010 - Invested (my wife has other views) in the Atik 320e, filter wheel and LRGB filters.  Took some mastering of the technique to combine into a final image using Paintshop Pro X3.  Bit of a palava setting up now, but I can at least see some significant red in Ha intense objects which is not the case with the unmodified EOS.

Feb 2011 - Bought an SBIG SG-4 standalone autoguider - was originally going for the Sky Watcher unit - but was offered a price I found hard to turn turn down. Use with the ST80 achro, although the narrow field does mean that it needs to be moved off-axis to find a suitable guidestar sometimes.  This has been significantly improved by attaching a x0.6 focal reducer which speeds the scope up and increases the effective field of view.  I can well recommend.

Mar 2011 - Bought a Sky-Watcher Equinox 120ED Pro and matching focal reducer/flattener.  Getting some good results out if guided.  A bit slow for using un-guided I suspect.  I have made up some objective lens protection cells out of Baader Turbofilm - seems to work pretty well as bonfire ash seems to be coming an increasing problem.

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Reply Allan
11:45 AM on December 24, 2011 
Hi Doug,
Thanks for the offer of the dew heater. I'm definitely interested.
My contact details are email
Tel: 01482 840467
Address: 348 Bricknell Ave, Hull.
I am also willing to pop round to your place to have a look at your other goodies. Thanks again.
Reply Allan
5:35 PM on June 18, 2011 
The book you want is " Photoshop Astronomy" by R. Scott Ireland. ISBN 0-943396-85-9. You can pick one up on Amazon for about 45 to 50. It is the Holy Grail of digital processing.
Cheers Allan
Reply Flamencopaul
8:53 AM on August 20, 2010 
Hi Doug, I've been doing a little more thinking re. your PE issues.
As well as the PE in the worm drive that you have measured and corrected for, there may also be additional errors caused by imperfections in the main RA gear teeth themselves. This would add an additional error that would still be periodic, but have different amplitude.
Also the balance of the scope and it's pointing position in the sky determine which side of the worm acts on the main gears. These may provide differently phased modes within the overall PE, which may explain the different results from your two session - did your spreadsheet analysis give any suggestion of multi-modal PE?
If your video capture card outputs AVI files you could use IRIS to help your analysis. Apply a constant translation to each sucessive frame in a direction perpendicular to the PE movement, then stack the frames - this would give you a time -based graph of the amplitude and period of any error, as well as identifying multi-modal error. An alternative would be to animate the AVI sequence at a slow enough frame-rate to be able to click the star centre in each frame. Iris provides the x and y coordinate of each clickpoint in the info box where you could copy them for use in a spreadsheet.
Most PEC software works by recording the corrections made by an observer during a full worm gear cycle, whilst keeping a star centred in the crosshairs of a high mag reticle eyepiece plus barlow. They recommend doing this using a star close to the meridian and on the celestial equator. If you can rig a data recorder to your encoders you will have a record of the corrections you need to apply to compensate for the PE however it occurs, then use this data to program your motor controller.
I also reviewed some of the Meade message boards re. PE. Figures of ~50 arcsecs peak to peak were common in uncorrected mounts, with PEC reducing the error to ~10 arcsecs peak to peak.
Hope this is useful to you.


Reply Flamencopaul
7:32 PM on August 19, 2010 
Hi Doug,

I can't see anything obviously wrong with your calculations, but periodic error is a strange beast! It's possible that the error has more than one mode and you missed something in your 15sec sample rate with the DSLR. The LX200 at Brough suffers so badly from PE that we turned to autoguideing! If you have access to a cheap webcam such as a toucam pro, there is free software called Metaguide, which has amongst it's functions, the ability to log periodic error. You can get it at

Even if you never use it to autoguide, it is very good for collimating as well as logging all sorts of data.


Reply Flamencopaul
7:23 AM on May 6, 2010 
Hi Doug,

Email me at and I'll send you some of the IRIS tutorials that I've collected over the years.

Reply Flamencopaul
7:00 AM on May 5, 2010 
Hi Doug,

As far as I know, we've still got a pile of these batteries at the BLAS dome. I'll ask George where he's hidden them!

Reply steve ( BLAS secretary)
4:10 AM on April 1, 2010 
Great Doug, thanks for that, I'll let George Know.
Maybe see you on Friday night ! Regards

Steve .