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Pete Presland

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Posts posted by Pete Presland

  1. Nice images again Luke, I don't think they are much different to what i am getting to be honest. I would not expect super sharp detailed UV images, i think your images have plenty of detail while retaining a very natural appearance.

    I have posted a response to you question RE difference in exp length, in the thread.


  2. 7 minutes ago, mikeDnight said:

    Many years ago there was serious debate about the visibility of cloud detail on Venus. Patrick Moore was definitely among the doubters, at least initially, as he saw nothing but a silver/white surface. Richard Baum on the other hand, a very experienced planetary observer and author, saw detail will little trouble. The two were on opposing sides of the debate until Patrick, Richard and a third member of the party who worked at a laboratory somewhere near Chester, organized an experiment to test the visual sensitivity of the three in relation to UV light. It turned out Patrick was not sensitive to UV, Richard was much more sensitive and the third member had sensitivity somewhere between the two extremes. At the end of it Patrick became a believer even though he still couldn't detect detail on Venus cloud tops. 

    Here's a pic of Richard taken at his home in Chester when I and Paulastro visited him in February 2017. He sadly passed away later that year, but was always a great inspiration to me as his planetary sketches are unsurpassed IMHO.


    A couple of Richard's sketches below show the famous Y pattern often depicted by visual observers, and the sometimes streaky nature of the clouds.


    Loving this! How very interesting, especially the different sensitivity of each of the individuals. Thanks for sharing this.

    • Like 1

  3. On 07/02/2020 at 07:51, lukebl said:

    Thanks Pete. It's a complete mystery to me how you can capture it at 14ms and I can only manage 250. I'd welcome any suggestions! I didn't  think my camera was that unsuitable for the job. I note that you use Firecapture. Perhaps you can crank up the gain better in Fircapture than Sharpcap? Perhaps the filters are different?

    I have been thinking about why your exposure is so different from mine. 

    Looking at the QE graphs for both cameras and reading about it, i think mine might be a little more sensitive at the UV end of the spectrum.

    I copied this off their website, it mentions a UV-IR blocking filter?

    ALTAIRGP130M-FULL Package:

    • CS-Mount adapter with built-in Clear Optical Window, AR coatings. (Attached at factory but removable).
    • CS-Mount adapter with built-in UV-IR Blocking Filter, AR coated. (Removable)

    I also wonder whether your scope has some sort coating on the mirror perhaps, not been able to find any info despite a long look online. 

    Not sure i have helped, but i was interesting reading about the subject anyway.





  4. Some very nice detail visible there. My exposure with my C9.25 and the same filter are around 14ms.  

    This is the Firecapture log details for my latest image.

    Camera=ZWO ASI290MM
    Frames captured=26328
    File type=SER
    FPS (avg.)=67
    SoftwareGain=10 (off)
    Sensor temperature=15.5 °C

  5. 1 hour ago, lukebl said:

    Pete, what exposure times are you managing with Venus and the Baader filter?

    As I've mentioned in my post here, this filter lets through so little light that I can't capture anything with an exposure faster than 1/4 second. So I can't manage to freeze the seeing. I managed a reasonable effort with that image last night, but this evening I couldn't capture it anywhere near as sharp. I noticed someone on Cloudy Nights had managed to capture it at 1/100 sec. I wonder what I'm doing wrong?

    Its around 14ms. The image from the 18th was 13.25ms at 3.30 in the afternoon (daylight), the image on the 28th was captured later, but still only 14.84ms. 

    • Thanks 1

  6. 11 hours ago, NenoVento said:

    Excellent image @Pete Presland!. The filter may be the trick but it also takes to really master the scope just to make focus with Venus. At what time did you make the capture, please?.

    Yesterday I got the chance to try my wratten #47 plus the UV/IR cut filters and the captures I made at about 16:30 came out pretty bad, probably due to too much daylight, maybe... That is why I'm asking. I also made a few more at about 18:00, right before I had to finish my session, but I haven't got the time to preocess them yet.



    This particular image was at around 4:50pm, so still light. My best images have nearly all been in daylight, one of them was the middle of summer in the afternoon.

    • Thanks 1

  7. 23 hours ago, JamesF said:

    I think that's sorted the weather forecast for 21/12/2020 then :)

    I shall also put it in my diary, as I'd not want to miss not being able to see it.


    The "gallows" humour of an astronomer 🙂 essential when based in the UK especially!

    • Like 1

  8. 30 minutes ago, NenoVento said:

    Thanks @Pete Presland, the reason for using the UV/IR is because I read somewhere (probably in CN) that the wartten #47 filters have a window in the IR zone. Anyhow, when I get the chance I will try imiging with and without it.

    That's definitely correct, also the older UV filters used to leak IR as well. That's why a IR cut filter is recommended. 

    But for cloud detail you need to capture the UVsignal, not block it.

    I tried the wratten 47 and an IR cut filter before I owned a Baader UV filter. I never had any luck capturing any detail though. Looking forward to seeing your results, I have seen details captured on Venus images with other filters when I have researching online in the past.

    • Thanks 1

  9. 23 hours ago, NenoVento said:

    Hi @Barry-W-Fenner,

    I've tried a couple of times but had no much luck. Hopefully from now to March I'll get more opportunities but, to be honest, in my next try I'm thinking on using a #47 violet filter together with an UV/IR cut filter (since I haven't been able to find an only IR-cut filter so far).



    Not sure you want to use a UV/IR cut filter with the #47 filter. you need the UV part of the spectrum to pass through the filter not be blocked by it.

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