Mr Andrew Jonathan Wilson

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  • in reply to: Finderscope Webcam #584219

    There are also the Celestron Starsense and Meade Starlock. The drawback is that I think these only work with their products, but sound a lot like what you describe.

    https://www.celestron.com/pages/starsense-technology

    https://www.meade.com/starlock/

    in reply to: Finderscope Webcam #584217

    A few years ago I got the equivalent 50mm guide scope and camera, currently selling for £235 on this page. I think it was more expensive when I bought it and prices have come down. They do various options, including the telescope guider body with a non-rotating helical focuser on which you could put your own camera of choice for £109.

    https://www.altairastro.com/guide-scopes-97-c.asp

    Of course the main purpose of this setup is as a guide camera rather than a digital finder, but I found it worked perfectly for my purpose. A GoTo mount that wasn’t quite good enough to always put the target in the small field of view of the guide camera on a spectrograph.

    Best wishes,

    Andy

    in reply to: Nova Cas 2021 #584142

    I’ve now merged V1405 Cas and Nova Cas 2021 into a single object. Either id can be used to upload data, and they will both show in the V1405 Cas light curve.

    Cheers,

    Andy (BAA Photometry Database Manager)

    in reply to: Aberrations in astronomy #584015

    Another couple of thoughts. Fundamentally, even with a “perfect” telescope a star is a disc due to diffraction in the optics, and you rarely see performance at the diffraction limit as atmospheric turbulence blurs this disc.

    Cheers,

    Andy

    in reply to: MASTER OT J172758.09+380021.5 #583971

    Hi Lars,

    I’m afraid there is nothing in the BAA Spectroscopy Database. It is on the faint side for most spectroscopists at around 14th magnitude, but there are some who can go that faint.

    Best wishes,

    Andy

    in reply to: Advice Required #583948

    Hi Mike,

    Hopefully one of our current AIP4Win users will jump in. If not then I can offer you some help by reviewing your spreadsheet results. I have a little knowledge of AIP4in though I’ve not used it in many years. I manage the BAA VSS/Photometry database and did a lot of the work to create the spreadsheet. I’ll also be the person to set you up with a login.

    You can contact me via my official BAA email address photdbm@britastro.org.

    As you’ve already got AIP4Win and the spreadsheet working, you are well on the way to submitting observations!

    Best wishes,

    Andy

    in reply to: Rspec or Bass or… #583936

    Hi Lars,

    Rspec is designed to be easy to use but has limited functionality.

    BASS is the next level up. It has a lot more functionality and is a lot easier to use than say ISIS. ISIS is pretty much the gold standard in spectral processing, but is the hardest to use.

    I suggest starting out with BASS as it is free, and see how you get on.

    I also suggest starting simple. The A-type star is used to response correct the spectrum. This is to remove the bulk effect of the Earth’s atmosphere, and to adjust the bulk profile of the spectrum for the telescope and camera sensitivity. Note this doesn’t remove any spectral lines, just large scale features that affect the shape of the continuum. While this is important for getting a correct continuum, I wouldn’t bother with your first few spectra unless you really want to. I took spectra for 3 to 6 months before attempting a response correction.

    When you are ready to do a response correction, then you will need to choose an A-type star at about the same altitude and on the night of your observation. The altitude of the star will affect the response correction as when you look lower down you are looking through more atmosphere. Also, atmospheric conditions can affect the response, so a response taken on one night may not work on another night.

    Most important of all is to keep it fun! Don’t worry about getting things exactly right at the start.

    Best wishes,

    Andy

    in reply to: PHD Study Opportunity #583849

    If anyone is interested then I would not let age hold you back.

    I am fortunate enough to have returned to university in my late forties to do a PhD in astronomy. While I have seen more years than most of my fellow PhD students, I’ve met plenty older than me who only started once they retired.

    Andy

    in reply to: Feb JBAA #583834

    I’ve been in contact with the BAA Office and they have confirmed there has been a bit of a delay to the Journal this month. They should be arriving with people any day now, noting the BAA Office haven’t yet received their box of copies, to their home addresses as they are of course working from home at present.

    Paul & David, I was sorry to hear you had problems with your Journal deliveries. I’ve done a little investigation with the BAA Office to check there is no ongoing problem.

    David’s appeared to be some kind of delivery problem. He’s had no changes to his address and his address was in the list sent to the printers in August.

    There was a minor problem with Paul’s address that we didn’t spot. Basically an issue around the country not matching a known Royal Mail Zone causing it to fail. We discovered this after the December Journal print run and have implemented some changes to avoid this problem in future. The Office are now able to produce a list of any problem addresses before doing the Journal run, so they can fix them prior to generating the mailing list to the Journal printers. It only affected a handful of members, I think less than 6, who were sent their Journals separately by the Office. We should have spotted and fixed this sooner, so our apologies.

    Best wishes

    Andy (with my BAA Systems Administrator hat on)

    in reply to: 23rd January meeting #583678

    Hi Daryl,

    Thanks for pointing that out. It was a mistake I made when updating the meetings/webinars for the first half of this year earlier today. I accidentally unticked a settings that promotes meetings from the events page onto the front page.

    Best wishes,

    Andy (with my Web Content Editor hat on)

    in reply to: CALSPEC reference spectra #583518

    Hi Andrew,

    In that case it would be best to create a zip containing everything, or a choice of zip and another compression format.

    It is easy to add one or two files, but each file requires its own download page, hence it makes sense to have a single file with everything. It will also be easier for people to download a single file.

    Best wishes,

    Andy

    in reply to: CALSPEC reference spectra #583515

    Hi Andrew,

    I agree this sounds useful, thank you.

    I may be the person who helps to get these onto the website, so my initial thoughts are about what the files are like. Are there one or many, and what file type are they?

    The E&T pages sound like a useful place to put these, although the Drupal software on which the website is based can sometimes make things like this a little tricky. They might need to go in the Publications->Downloads->Sections->E&T area of the website. A backup plan would be to put them on the BAA Spectroscopy Database pages, though the main website would be better as long as it doesn’t get too messy.

    Best wishes,

    Andy

    in reply to: New Gaia data release #583482

    It is worth noting that while the G magnitudes are excellent, there are known small issues for bright blue stars and faint red stars. Details can be found in Riello et al 2020.

    The bright blue stars are G<13 and BP-RP<0.1, appear to have an ‘anomaly’ of up to a few mmags.

    The Gaia web pages provide Python to correct the systematic in fainter G magnitudes, G>13. This is not a major problem and in most cases will be very small except for redder stars. For example it can reach about the 1% level for about BP-RP>2, though at the extreme red end can reach 2.5%. I’m using a few million Gaia sources, and in my sample the official correction adjusted 1% of the stars by 1% in G. There is mention in the paper of a separate table in the Gaia archive for corrected G-band photometry, though I’ve not seen that yet and I wonder if it will appear in the coming days.

    There also appears to be parallax zero point bias by magnitude, colour and position (Lindegren et al 2020). Again a Python script is provided to calculate this bias.

    If anyone is interested in the Python corrections, then the source code can be found on the Gaia webpages here: https://www.cosmos.esa.int/web/gaia/edr3-code

    This is not intended to take away anything from the Gaia results, which are amazing. It is usual for a major survey to have some small issues to be aware of, especially noting this is just an interim data release.

    Andy

    in reply to: Arecibo collaspes. #583434

    I am glad to see no one was hurt. As sad as it is to loose Arecibo there are huge new projects in radio astronomy. The one that springs to mind is the Square Kilometre Array. I am sure there is a trade off between building and operating new observatories, versus keeping old ones operational.

    Andy

    Hi Peter,

    Many thanks for pointing this out. I did a quick search of recent images and found an idential image by Peter Goodhew FRAS. I have corrected the page as I am sure this was an innocent mistake, possibly even a browser autocomplete when this was promoted to picture of the week.

    Our apologies to you and Peter Goodhew FRAS.

    Andy

    in reply to: New Starlight Xpress spectrometer #582907

    Thanks for sharing this Callum. I heard of this spectrograph a few years ago but didn’t know they were adding automation.

    It is great that SX are entering this field though I didn’t see anything that tells me how well the spectrograph performs. The idea looks great, but they really need it in the hands of someone who knows how to produce good quality spectra to see how well it performs in the real world. It could be fantastic but they only showed the most simple of results, a bit like demonstrating a new telescope by taking single images of the Moon without proper processing.

    I would want to know how stable is it on the back of a telescope in an imaging run. It appears the design should be very stable but theory and practice don’t always match. I also want to know what the resolution is as that defines what you could use it for, along with how that matches to CCD pixel size. Interesting that the camera can be shifted across the spectrum though I’d want to know how much of a spectrum you can fit in a single exposure, and how stable that movement is. It has to be absolutely rock solid, otherwise things like wavelength calibration and response correction needed to create good quality spectra would fail. If someone could obtain spectra of more challenging targets and do the full end to end process including response correction that would go a long way to demonstrating they have a high quality product.

    I do not agree that they are coming in cheaper than their competitors. There are only a couple of modular spectrographs I can think of, most come as complete units. Of the modular spectrographs one is cheaper and the more expensive one is a top end spectrograph designed for large research telescopes. They appear to be coming it at about the same price or possibly more expensive than complete unit spectrographs. That is not to put their spectrograph down, just I did not agree with their comments on the price. This might not be a negative as they have automation, though they are not the only spectrograph with automation capability.

    I don’t mean to be too negative as I think SX produce great CCDs and accessories, and I want this to be a great spectrograph. I am just hesitant as this is their first foray into spectroscopy and I’ve not seen any results that demonstrate the quality of the spectra it produces.

    Cheers,

    Andy

    in reply to: C14 mirror flop #582707

    Hi Jack,

    I hope you don’t mind but I thought I’d ask what problem it is you are trying to solve.

    I remember you were having issues with wavelength shift in your spectrograph. If this is the problem then I don’t think mirror flop in the telescope is likely to be the cause.

    Of course if you are having trouble with shifting position of the star when you cross the meridian then that would be fixed by solving mirror flop.

    Cheers,

    Andy

    in reply to: To do or not ? #582688

    Hi Jack,

    You don’t need high end equipment to do photometry so that should be fine.

    What really matters is making sure you do flat fields, and that is the same whatever equipment you use.

    Cheers,

    Andy

    in reply to: CMOS v CCD for photometry? #582607

    We might be talking about the same thing, but in case not.

    You would expect the graph to change once you are outside the linearly region and then into saturation. Once a star becomes saturated you are not detecting all the photons that land on the chip.

    Cheers,

    Andy

    in reply to: CMOS v CCD for photometry? #582600

    Hi Simon,

    The important point is once a pixel is saturated it won’t count any more photons. It is possible that if a tiny number pixels are just above saturation or in the non-linear region then that non-linearity won’t be obvious. There will be lots of pixels contributing. However, it is a risk and you would not be able to justify your result if you were trying to extract a reliable magnitude.

    Looking at your graphs, they show a slightly different behaviour in the linear region. It appears to be a steeper slop, followed by a little bit of a wiggle.

    If saturation is a problem as you want longer exposures then you can slightly defocus the star. This will spread the photons over more pixels while keeping them within the linear region.

    Cheers,

    Andy

Viewing 20 posts - 41 through 60 (of 332 total)