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Posted by Denis Buczynski at 11:50 on 2012 Oct 09
Hi Paul,The displa y started around 22:00UT and was still active with rays at 04:00UT. I have seen some phenomena in this display which I have not seen before even though I have been lucky to see many. The heights which some of the arcs and rays reached must have meant that it could have been seen further south. I tried to laod an image from last night onto this forum but without sucess, I will try again with this.Denis
Posted by Paul A Brierley at 06:43 on 2012 Oct 09
You have been busy Denis.I have just opened my e-mail folder, to find I had an alert from Aurora Watch UK.I wonder how wide spread this display was?
Posted by Denis Buczynski at 02:02 on 2012 Oct 09
here is the image I intended to post with my message
Posted by D A Dunn at 14:05 on 2012 Sep 30
Graham,Thanks for the link to your presentation. Just got back from 2 weeks in Provence with very dark skies, looking forward to seeing what the images are like that I took.RegardsDavid
Posted by Andrea Tasselli at 08:04 on 2012 Sep 24
Very well done indeed! I find it with far too much blue in it, to the point of being essentially monochrome. Colours other than blue seem also too saturated.Andrea T.
Posted by Nick James at 23:27 on 2012 Sep 23
Glad it went so well. I was going to come along but, typically, left it late so there were no places. I don’t recall many BAA meetings that have sold out so it shows how much demand there is in this area.
Posted by Nick James at 23:25 on 2012 Sep 23
Indeed. I’ll second Jeremy’s comments. Fantastic stuff.
Posted by Roy Hughes at 17:06 on 2012 Sep 23
Graham,thanks for the PP presentation, I wasnt there so it has been a very good read. It prompted me to revisit posts earlier in this thread about 32 bit floating point TIFF files.In an earlier life (pre-retirement) I worked in the city writing back office systems where microscopic rates of interest were applied to astronomical sums of money (not mine!) and spent a lot of time investigating the accuracy (or otherwise) of floating point numbers.Floating point numbers are always saved Normalised (i.e. no leading zeroes) so any any loss of accuracy is at the low end of the number. The normal IEEE representation as used in the math co-processor in your PC has the general format [8 bit unsigned exponent, sign bit, 23 bit mantissa]. The exponent is implicitly scaled giving a range -127 to +127. The first binary digit of the mantissa is omitted (as by definition it will always be 1) and the next 23 bits stored. The 32 bit floating point TIFF format follows this standard (if the document issued by Adobe in 1992 is to be believed) and therefore the accuracy is 24 rather than 23 bits (7.225 decimal places).The final precision when holding integer numbers in floating point would vary according to the size of the number being represented, a fully saturated pixel would lose accuracy (but only at the 1 part in 16 million odd end, where it really would not matter) but not magnitude. At the other end of the scale a single 1 bit value would have 23 spurious binary places of accuracy.I can see that the software manipulating the numbers could need 32 bit integer working registers but 32 bit TIFF files should work quite acceptably for storing images.Have I missed something here?. Over to you.Roy
Posted by Jeremy at 14:23 on 2012 Sep 23
That’s another cracking image, Bob. An amazing amount of fine detail. Well done!Jeremy
Posted by Graham Relf at 09:13 on 2012 Sep 23
A zip of the PowerPoint file from my talk yesterday (DSLR Observers Workshop) can be downloaded from britastro.org/computing/gr/WhyStack.zip.It’s about 17 Mbytes.
Posted by R J Andersson at 17:31 on 2012 Sep 16
Hi folks,I reprocessed, starting from the original stacks. Here’s the result and you can view the 4096 x 4096 pixel version here.
Bob.
Posted by Anthony Stone at 14:44 on 2012 Sep 13
One just just like it widescreen centre London £99.99
Posted by Callum Potter at 16:57 on 2012 Sep 10
Hi Andrea,thanks for clarifying – my memory does not seem to be what it used to be!Callum
Posted by Andrea Tasselli at 14:40 on 2012 Sep 10
Just to clarify further; IRIS does NOT use in any form or fashion 32-bit deep images nor it is capable to read them. It only recognizes 8 and 16-bit deep images and uses 16-bit *signed* FITS files (or PIC) up to 3 planes per image.IRIS (and all the software I know of) will happily align and stack calibrated and UN-calibrated frames, so it is up to the user decide what to do.As long as there are 3 stars shared between all the frames IRIS is more than capable to align and stack them. In fact they do not have to have been taken with the same hardware *at all*, as long as there are enough stars to perform trasformation (to a common scale), alignment (with possible morphing) and stacking.Andrea T.
Posted by M C Butcher at 10:52 on 2012 Sep 10
Alex,Many thanks. I have downloaded the Paul Maxson tutorial so now I’ll get down to swotting up!Martin
Posted by Richard Miles at 19:40 on 2012 Sep 09
I would like to inform members that the subject of ‘JBAA Papers’ was raised at the Council Meeting held on the afternoon of Wednesday 5th September at Burlington House. In due course, a working group will be set up to look at various aspects of the Journal and other publications. Clearly, the matters raised by Steve Holmes and discussed by six other BAA members on this forum will be valuable input to such a working group. In the meantime, I shall prepare a short document to capture the various points raised in the course of the recent online discussions for due consideration by the working group.I must point out that activities of any working group set up by Council are of a confidential nature such that details can only be shared with members of Council and other trustees of the Association. If any members would like to become actively involved in the running of the Association then all they need to do is to find two other members who are prepared to nominate them for election to the Council (an annual event, the result of which is announced at the AGM in late October). The annual deadline for nominations is noon on the first Friday in May. For more information see:/images_old/stories/misc/pdf/BAA_memorandum_articles_bylaws.pdfand especially Pages 6-7 (Clauses 23-31) and Pages 9-11 (Clauses 8-16).Sorry if this all sounds a bit formal, it’s not meant to be.Richard Miles
Posted by Callum Potter at 17:45 on 2012 Sep 09
Sorry if its stating the obvious, but you should be stacking calibrated frames – ie, frames corrected with darks, flats and biases (from the night the images were made).Then there should be no problem stacking from different nights.Good stacking software should align even if there is some misaligment of frames.I have tended to use IRIS which also works with 32 bit integer data – a point Graham makes well.Callum
Posted by Graham Relf at 15:59 on 2012 Sep 09
There should be no difficulty, provided that there is a significant overlap between the frames, so that most of the brightest stars in one frame are also visible in the others. The scale needs to be similar too – ie, the same focal length lens or optical set-up in the telescope for all frames.My own software works by looking at the patterns of connecting lines between the brightest stars (the 24 brightest, unless the user changes that number). They do not all have to match.Stacking is done into an accumulator image having 32 bits per channel, so that adding up brightnesses does not cause them all to saturate (reach the 16-bit limit, which is the depth of the original images). For deep sky work it is important to keep the 32-bit depth for subsequent processing, otherwise you are throwing away the possibility of pulling out the faintest detail from the background. So if the stacking software can take as input files having 32 bits per channel, you will not lose anything by stacking two or more already stacked results. That necessarily means saving the results as FITS files because 32-bit TIFF files (aimed for importing into Photoshop) use 32-bit floating point rather than integer values and so really have only 23 bits per channel resolution (allowing for wasted sign bit).If you cannot use 32-bit FITS files as input to the stacker you would be better off stacking all of the original 16-bit frames in one sequence, even if from different nights.
Posted by Paul Abel at 23:46 on 2012 Sep 07
Excellent, I’m glad a few more people are interested. I have used my 203mm Newtonian in good conditions, at at x350-x400 faint banding is sometimes apparent. I also use the University of Leicester’s 20" Planewave DK. That certainly has a lot of light grasp. I think a long period of coverage (i.e. the way we cover the main planets) would be more helpful that just a couple of pictures around opposition.Best wishes,-Paul.
