[Mr Ian David Sharp]

Lars Lindhard wrote:

Any explanation for the drop in blue magnitude?

Yes, as Andy has explained – cooling.
Ian.

[Mr Ian David Sharp]

Here’s my latest graph including last night’s results (31st May). I make B-V = +0.24.
Ian.

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   SN2023ixf_31st_May_ids.jpg
   

[Mr Ian David Sharp]

Hi Grant,

I own 3 of those SX Midi wheels and also a larger one for 2″ filters and I have only had the droop issue when I was connecting one to a small WO71 APO with a fairly heavy ATIK CCD. I think it was the CCD that did most of the drooping in that case!

The other scopes I use have much more robust focusers such as Moonlite on my C9.25, and the Tak focuser on my Tak 85. These focusers are designed to carry much heavier loads.

I don’t think that the SX Midi FW is a particularly heavy example of a filter wheel, so I don’t think I can say anything that will help with your current setup. I think I would have to fall in the ‘buy another focuser’ camp!

Cheers
Ian.

• This reply was modified 1 year, 1 month ago by Mr Ian David Sharp.
• This reply was modified 1 year, 1 month ago by Mr Ian David Sharp.

[Mr Ian David Sharp]

Good morning all,

See the attached for the graph of my continuing nightly R, V and B measurements. The continuing drop in blue magnitude is fascinating. B-V was +0.18 last night.

Cheers
Ian.

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   SN2023ixf_29th_May_ids.jpg
   

[Mr Ian David Sharp]

Today’s update attached.
Cheers
Ian.

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   SN2023ixf_28th_May_ids.jpg
   

[Mr Ian David Sharp]

Robin Leadbeater wrote:

Yes my spectrum from last night shows it cooling further to a black body temperature of ~12000K and a fit to an A3v star continuum with a B-V = +0.1

Here’s today’s RVB magnitude plot. The cooling clearly visible with the latest point B-V = +0.12.

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   SN2023ixf_27th_May_ids.jpg
   

[Mr Ian David Sharp]

Robin Leadbeater wrote:

That’s useful. The continuum in my spectrum from last night does indeed match an A0v star which by definition has B=V=R

Thanks for the info Robin, most interesting. I’ve attached my graph again – updated with last night’s points. It seems that the R and B are slowly swapping dominance! Also note the very slight dimming.

Ian.

• This reply was modified 1 year, 1 month ago by Mr Ian David Sharp.

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   SN2023ixf_25th_ids.jpg
   

[Mr Ian David Sharp]

It’s definitely plateaued

Here are my mags from last night (24th May around 22:30)

V = 11.03
B = 11.04
R = 10.99

Cheers
Ian.

• This reply was modified 1 year, 1 month ago by Mr Ian David Sharp.

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   Screenshot-2023-05-25-120100.jpg
   

[Mr Ian David Sharp]

Kwong Man wrote:

How do you calculate its magnitude please ?

This is not an easy question to answer! I would recommend reading the AAVSO photometry guide which is kept well up to date:

https://www.aavso.org/sites/default/files/publications_files/ccd_photometry_guide/CCDPhotometryGuide.pdf

As to the choice of software, I can personally recommend the Tycho Tracker software. The Pro version is well worth the $50 for the licence and is very easy to get going with. There are plenty of YouTube videos to get you started. Many will say to use AstroImageJ (which is free) but I think this is hard to get going with. I also use the amazing (and underrated) AstroArt8 software which is easily scriptable.

https://www.tycho-tracker.com/

Hope that helps.
Ian

[Mr Ian David Sharp]

Kwong Man wrote:

What is the V filter I read on earlier?
I want to do photometry on this. Do you need a really high focal length telescope e.g. C11 or can you do it with smaller lower focal length refractors?
Can you use a h-alpha filter 7nm bandwidth and do useful photometry ? as I am in a light pollution area.

You can use smaller telescopes – I regularly use a 100mm refractor to measure stars down to 13th magnitude.

The V filter is a Johnson/Cousins V Filter. These are standard photometric filters. You can still work unfiltered or use a colour R, G or B filter as long as you specify which was used.

I don’t believe you would have much success with a narrowband filter.

Hope that helps
Ian

[Mr Ian David Sharp]

Hi all,

Very fractionally brighter again last night but looks to be flattening off. These from 22:30 UTC last night:

V = 11.04
B = 11.00
R = 11.02

Cheers
Ian.

[Mr Ian David Sharp]

Hi all,

Here are my magnitudes from 23:00 UTC (center) last night. Averaged from 10 measurements with each filter using 120s exposures:

V = 11.09
B = 11.06
R = 11.11

So a full magnitude brighter than 2 nights ago. Attached is the current light-curve from the BAA photometry database.

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   SN-2023ixf-2023-05-23-085715.jpg
   

[Mr Ian David Sharp]

Here’s my LRVB colour version from last night. I’ve uploaded R, V and B mags to the Photometry Database.

Best Regards
Ian.

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   SN2023ixf_2023-05-20_23-00_LRGB_ids.jpg
   

[Mr Ian David Sharp]

Here’s a quick stack of 12 x 180s Luminance from last night (around 22:00 on 20th May). I have R, V and B too.

I measured the mag. from the V images as 12.11 (average of 6 images)

C9.27 @ f/7, SX694.

Cheers
Ian.

• This reply was modified 1 year, 1 month ago by Mr Ian David Sharp.

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   SN2023ixf_2023-05-20_23-00_L_ids.jpg
   

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   Tycho_Graph.jpg
   

[Mr Ian David Sharp]

Robin Leadbeater wrote:

Kiochi Itagaki has discovered tonight a type II supernova SN 2023ixf in M101 currently at mag 14.9

Thanks for the heads-up Robin. I wish I’d seen that last night as I was imaging for photometry from 10:30 until 03:00 here with lovely skies! Looks clear again tonight…

Cheers
Ian.

• This reply was modified 1 year, 1 month ago by Mr Ian David Sharp.
• This reply was modified 1 year, 1 month ago by Mr Ian David Sharp.

[Mr Ian David Sharp]

Dr Paul Leyland wrote:

Can your driver be used under EKOS?

Perhaps we could discuss this in greater detail by email rather than clogging up the BAA fora.

I know nothing of this EKOS of which you speak! Yes, let’s talk offline…

ian.sharp@astro-sharp.com

Cheers
Ian.

[Mr Ian David Sharp]

Dr Paul Leyland wrote:

At the moment domes with a Velleman controller, mine included, can use only the LesveDome ASCOM controller. The problems with LesveDome is that the source code is unavailable, it is Windows only, and is ASCOM instead of the much more portable INDI.

I’ve written my own Dome controller using the ASCOM Alpaca standard. My code runs on a Raspberry Pi. The Alpaca initiative is fully portable as it uses a JSON/REST API and therefore is no longer Windows COM specific.

[Mr Ian David Sharp]

Dr Paul Leyland wrote:

Ah.

When I add a new star to my program…

Thanks Paul,

I call the AAVSO API to get me the VS data and the candidate comparison stars in a requested mag. range and chart width. I use the B-V from SIMBAD to give me a guide to any major differences that there might be in the B-V values of the comparison stars. It’s more of a sanity check – sometime there aren’t enough good choices to throw any out! My code then builds this info into my master variable star csv file which is read by my automated photometry routines (Python and AstroArt8). The API also returns a URI with the chart which I stream down and save as an image file. The BAA and AAVSO upload files are automatically generated.

Cheers
Ian.

[Mr Ian David Sharp]

Dr Paul Leyland wrote:

Out of interest, what SIMBAD/VIZIER data do you use? For my purposes all that is required is the magnitudes and the coordinates, all of which is provided in a single download from AAVSO.

I use it to get the B-V of the target star. I couldn’t find that in the AAVSO data.
Cheers
Ian.

[Mr Ian David Sharp]

Personally I like the AAVSO charts and lists of comparison stars because it’s easy to query via my Python code via the AAVSO API. I combine that with SIMBAD/VIZIER data to get other parameters of the target star and I can then create a good list comparison stars for ensemble photometry. I just live with the chart ID warning when I upload to the BAA database.
Cheers
Ian.

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