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Thank you both. I have not been clear, sorry, I’d had two glasses of vino! I agree, a flat field calibration frame is definitely helpful for lunar imaging.
I meant should I use a field flattener, to project a flatter image on the chip when taking video for stacking of the Moon? Or again does the stacking process negate the need?
James
Ian,
I’ve looked at this and it seems the max file size limit has reverted to 2MB for the time being. I’ll let the web ops team know as something needs tweaking in PHP behind the scenes.
If you reduce the size of your images to less than 2MB, it will upload.
James
Thanks all. I had done extensive reading but with my limited knowledge and comprehension of such matters it was impossible to just get an answer in kg. I’m grateful to Nick for coming up with 750kg, which puts my mind at ease, especially as there are four bolts, and as pointed out the aluminium of the dovetail would likely fail first. Paul, I was worried more about shearing across the bolt than longitudinal force and stripping the threads. It was interesting reading about it all though, and I had no idea it was so involved and different thread counts present different shearing capabilities.
Thanks all!
James
Brendan,
That is really helpful, and gives me hope!
I already screw the camera directly onto the diagonal, but like you the 1.25″ nose piece on the diagonal needs to be pulled out of the focuser to achieve focus, and I wonder if that is where some tilt is being introduced. I will explore, and I have a much longer 1.25″ nose which may help.
All good advice, I am very grateful.
James
All online sources point to Borthwick and over 1m3 of material. It may be worth a trip to inspect it all.
Have you seen this: https://archive.org/details/in.ernet.dli.2015.165833/page/n57/mode/1up
Several entries in the British Library Catalogue and in Kew’s National Archives so worth looking there if you’ve not already.
And lots of items listed on WorldCat.
And this item in York Archives: https://catalogue.exploreyork.org.uk/client/en_GB/default/search/detailnonmodal/ent:$002f$002fSD_ILS$002f0$002fSD_ILS:781724/one?qu=Cooke%2C+Troughton+and+Simms+Ltd.&dt=list&h=0
And this in the RAS Library: https://royast.cirqahosting.com/HeritageScripts/Hapi.dll/retrieve2?SetID=3548FC96-A89E-472D-B5C3-A99C93BF2149&searchterm=Troughton&Fields=%40&Media=&SearchPrecision=20&SortOrder=0&Offset=3&Direction=%2E&Dispfmt=F&Dispfmt_b=B27&Dispfmt_f=F00&DataSetName=LIVEDATA
Good luck finding what you are after.
I had a hunt online to try and work out what the sensor was in the camera, but to no avail. Hopefully someone else will be able to track down the sensor then it should be easier to find the QE… maybe.
James
Gary, I think you’ve nailed it. With the eye of faith I can see an inner circular halo in Sue’s photo. Looking in Stellarium the Sun would have been 52.5 degrees above the horizon. I’ve made an animated gif to show roughly where I think the true solar halo is:
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Chris Hooker emailed about something else and mentioned this. He strongly suggest I try some flats. I’ve found this video so will try some form of cereal bag flats later in the week; I probably won’t use a cereal bag, but something along those lines.
https://youtu.be/M7rSOXWQDZM?si=A6BESGiqf-UoXE5V
Thanks for the replies. I am feeling hopeful again.
James
Paul, I’m pleased I’m not the only nutter who likes collections like this 🙂 Are there any editions you are missing as I will rummage through the piles of books I have in my garage.
James
Grant, thanks. It may be that tilt here is reducing evenness of focus, but no end of playing with tilt does nothing to the unevenness of illumination. It isn’t even as though there is predictable gradient across the FoV, it seems there are areas of the FoV which have minimal gradient but these areas are not big enough to take the whole disc of the Sun and I’m not using a Barlow. I’ve just been looking and the B1200 is over £1000. Looking at Chris Hookers images in Ha with his newly acquired Acuter Pheonic 40 solarscope (https://britastro.org/observations/observation.php?id=20250509_220342_3acfea1c341b631f) he has no gradient, and I’d suggest potentially even better contrast than I can achieve. I am having to stop myself just clicking buy now Rother Valley Optic’s website (£999).
James
This is from today. The gradient in brightness is not a natural feature, it is artefact.
I’ve not. Invariably this scope is set up outside so tracking is usually awful. I just feel there is somethign fundamentally wrong and I’d like to resolve it one way or another.
Thanks.
James
Yes an absolutely brilliant weekend. I was exhausted when I got home last night. I’ve come away with lots of ideas of things to do to improve my own observing techniques and new things to have a go at. Also great to speak to people who I only ever encounter online. The BAA at its finest. Thanks for all who organised and ran the show, especially Tony, Ann and Alan, but also the helpers on the BAA stand, registration desk etc. Brilliant.
I got up early yesterday (9.4.25) before work and managed to get the attached. Pretty disappointing, and the tail very faint compared to other observations I’d seen online. Askkar 120 with 0.8x reducer and Canon 6D, this is about 12 minutes in total of the best subs captured between 03:17 (UT) and 03:54 (UT); there were lots of bad subs. 30 seconds each, ISO 400. Desaturated and inverted to allow me to see the tail.
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