[Dawson]

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

[Dawson]

This is from today. The gradient in brightness is not a natural feature, it is artefact.

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   2025-05-10-1636_6-U-G-Sun_Halpha_AS_P5_lapl3_ap77_WS.png
   

[Dawson]

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

[Dawson]

Thanks Bill.

[Dawson]

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.

[Dawson]

Thanks Gary.

[Dawson]

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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   25Fcropped.png
   

[Dawson]

Well spotted with the relative QE. I’d missed that.

James

[Dawson]

Thanks both. Helpful comments and insight.

James

[Dawson]

Martin, thanks for that link. It is interesting, depending where you look, the transmission data varies… Surely the colour IMX585 should have a near identical transmission profile whatever camera it is in? Here are three plots, one from your link, one from the ZWO website (https://www.zwoastro.com/product/asi585mc-mm-pro/) and one from the PlayerOne website (https://player-one-astronomy.com/product/uranus-c-usb3-0-color-camera-imx585/).

James

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   585MC-1.png
   

[Dawson]

Martin, thank you.

Yes, poor Chris Hooker has been helping me, dragging me along really as I’m not that bright when it comes to solar physics, magnetospheres, energy states, wavelengths etc…! But good fun for me anyway. I’ve just seen there is a 585 mono camera which appears to have a QE of just under 90% at 589nm. I may have to do some overtime. The binning is an interesting idea I’d not thought of.

Regards

James

[Dawson]

Thanks David.

James

[Dawson]

Thanks David. Do you know when Martin gave this talk?

Regards

James

[Dawson]

We are going to try and live stream from Nottingham too in white light, and Ha if the clouds permit. Live stream should go live just before 10am.

https://youtube.com/@nottinghamastronomicalsociety?si=niCKwEgSv8w_qnWi

James Dawson
Nottingham Astronomical Society

[Dawson]

We got it in Nottingham too on the all sky camera and both meteor cameras:

https://youtu.be/Pm4pqW7jNaY?si=zqSEIPv6M1a9R0kZ

[Dawson]

I’ve just seen your image and am REALLY impressed. Looking forward to seeing what else you achieve with it. Congrats too.

[Dawson]

Looking forward to it. I am bringing a load of second-hand books to try and sell on behalf of the Society for the History of Astronomy.

See you in a few weeks.

James

[Dawson]

It is dust and dirt in the optical path somewhere. Things directly on the sensor can appear nearly focussed, things on the lens of a refractor can appear grossly out of focus. These things look to be between the two. Are you using any filters near the sensor?

[Dawson]

Thanks to Denis I now have a complete set of these. The numbering is odd (and incorrect) and is as follows:

Spring 1994, Vol 1, number 1 (“Premier issue”)
Summer 1994, 1, 2
Fall 1994, 1, 3
Winter 1995, 2, 1
Spring 1995, 2, 1 (it should be 2, 2 but presumably misprinted)
Summer 1995, 2, 3
Fall 1995, 2, 4
Winter 1996, 3, 1
Spring 1996, 3, 2
Summer 1996, 3, 3
Fall 1996, 3, 4
Winter 1997, 4, 1 (final edition)

Thanks also to Jeremy Shears for giving me the original copies a few years ago.

James

[Dawson]

Yes, the Mayor emailed me to see if she could come to the observatory tonight for the spectacle.

[Author]

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