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andrew s

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Posts posted by andrew s

    Remote imaging M16 - My first attempt

    in Imaging - Discussion

    Posted

    I am about to ship my kit to a hosting service in Spain. Expensive but I will get more data in the next few years than I could possibly get here however dedicated I might be.

    Last year I only got 5 decent sessions. I want to do studies that require considerable cloud free periods which just don't  happen in Cheshire, very often.

    It is up to individuals how they enjoy out hobby, visual, own kit, hosted or service.

    Maybe, Olly could provide a processing service as well as astro holidays?

    Regards Andrew 

    • Like 2

    gas giant question

    in The Astro Lounge

    Posted

    15 hours ago, Alien 13 said:

    From memory one of the talking points from the impact was that the damage was far far larger that had been predicted, which makes me wonder if Jupiter could survive an object the size of a rocky planet.

    Alan

    It probably already has during its formation. While the damage to various cloud layers was extensive the planet never blinked in its orbit or as far as I know its basic shape.

    However, it would depend on the details of the collision but my money would be on it surviving maybe with a new satellite or two from the splash. 

    Regards Andrew 

    • Thanks 1

    gas giant question

    in The Astro Lounge

    Posted · Edited by andrew s

    Friction heated up the comet fragments until they exploded. Just as a large meteors do in our atmosphere.  As you go deeper into Jupiter's atmosphere it gets dense quite quickly.

    Google "Atmosphere of Jupiter wiki" 

    Regards Andrew 

    • Like 1

    I'm confused! Do expensive eyepieces tease out more contrast?

    in Getting Started With Observing

    Posted

    The more expensive complex eyepieces work well with fast optics as the are designed to manage the steeply angled light rays over a wide field. With a reasonably slow Newtonian and possibly a Barlow or Powermate it will be less challenging for the eyepiece.

    There are some types of expensive eyepieces specifically designed for the planets e.g. monocentric e.g. http://astrograph.net/TMB-Supermonocentric-Eyepiece-10mm .

    Regards Andrew

    Large mass found on Moon

    in The Astro Lounge

    Posted · Edited by andrew s

    I went to see 2001 A Space Odyssey with Miss Ely at what was then the  Cambridge  College of Arts and Technology while doing my A levels .

    At about the same time the young Jupiter was rampaging through the inner solar system. I know an exaggeration but not by much.

    Regards Andrew 

    • Haha 1

    The Planets with Brian Cox

    in The Astro Lounge

    Posted

    13 minutes ago, Craney said:

    " First, I believe that this nation should commit itself to achieving the goal, before this decade is out,

    of landing that man, Brian Cox on the Moon and returning him safely to the Earth" 

    Go on,   its worth the increase in the license fee......

    Fully support getting him there not sure about the return. (Only kidding)

    13 minutes ago, Alien 13 said:

    I like the padding, the staring into the distance and most of all the soundtrack although that seemed a bit toned down this week, its called engaging with the masses who dont yet realize they have an interest in science...

    Alan

     But it is not science it's just posing and being a celebrity. I know I am being a science snob!

    Regards Andrew 

    • Like 1

    New Mono CMOS camera from Starlight Xpress based on IMX304

    in Discussions - Cameras

    Posted

    18 hours ago, andrew s said:

    While I agree it has long been the case that CCD gain ( actually inverse gain) has been given in e per adu. This is the term used by James R Janesick who pioneered CCD use in astronomy.  See "Scientific Charged Coupled Devices" by JRJ.

    Regards Andrew 

    I put this to SX and here is the reply from Terry

    "Yes, electrons per ADU is universally used to define the output of a CCD after A-D conversion, but it’s an ‘after the process’ gain, not the gain of the variable amplifier that CMOS chips include. In CMOS, there is a ‘gain factor’ applied before A-D conversion and this is defined in terms of 0 – N decibels (typically 0 – 40dB). This amplifier gain can be set in software, so we define its gain as unity when giving the base value of readout noise. It isn’t the same thing as the electrons per ADU that is often quoted in specifications. However, I agree that we need to be a bit more specific in our data sheet.

     

    Regards,

    Terry"

    Regards Andrew

    New Mono CMOS camera from Starlight Xpress based on IMX304

    in Discussions - Cameras

    Posted

    3 minutes ago, fireballxl5 said:

    It seems to me that SX are just using correct engineering definition of "unity" gain, i.e. a gain of 1 is 0dB. The others need to correctly define the units being used in their data sheets. 

    It reminds me of amusing anecdote from work, when a report was issued with the data presented in linear form. The results were deemed unacceptable (signal levels too high) to someone on the distribution and so the author simply re-presented the data in dBs, making the values lower. There was no further comment 😏

    While I agree it has long been the case that CCD gain ( actually inverse gain) has been given in e per adu. This is the term used by James R Janesick who pioneered CCD use in astronomy.  See "Scientific Charged Coupled Devices" by JRJ.

    Regards Andrew 

    New Mono CMOS camera from Starlight Xpress based on IMX304

    in Discussions - Cameras

    Posted

    Here is the reply from Terry Platt of SX a direct cut and past. It is a closed Yahoo group so you would have to join to see it.

    "Hi Andrew,

    I’m not sure where they get their numbers from, but they are clearly incorrect. The first fact to note is that Sony do not list the read noise for any of their sensors, so the chip manufacturer isn’t a source. The second fact is that we measured the noise at around 2.9 and 3.1 electrons on two cameras. The third fact is that even ZWO list this chip as giving 3.2 at unity gain (unity gain is at 0dB) – here is their graph:

    I think that your correspondents are assuming that unity gain means maximum gain, where the read noise does fall to near 1 electron – but that isn’t what we are quoting in the specification. Max gain greatly reduces the full well depth and is not desirable for many purposes.

    All the best,
    Terry"

    The link to the graph was missing so I have asked Terry to post it again.


     

    • Thanks 2

    New Mono CMOS camera from Starlight Xpress based on IMX304

    in Discussions - Cameras

    Posted

    10 minutes ago, Adam J said:

    I said no such thing. I just note it's inconsistent with other manufacturers measurements of the same chip. At any rate the important thing is how it performs in the real world. 

    Then I see no point in your reply as you just repeated what has been said before.

    I was pointing  out SX seemed to be giving a real world figure and speculating why it  might be different to others. You never commented on this just repeated the "fact" that the chip did not have 3e read noise, maybe it does with the different clocking? Who knows. That's why I have asked SX.

    Regards Andrew 

    • Like 1
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