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Jessun

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Posts posted by Jessun

  1. APM LSOZ 105/650 kit with FT3.5" focuser, Focus Boss II and motor, and a RiRed of your choice. (M81 or M63 plus adapter ring for the FT. Either reducer sits inside the focuser tube).

    Rings and dust cover are included as well of course. Comes with test report from May 2015 and some paper in Russian ūüėĄ¬†...

    These sell new for around 3700 euros with a 2.5" APM focuser. The parts included in this sale amounts to around 2500 euros.

    The scope has sadly only ever taken one image, so the hours spent outside are minimal. It is truly as good as new. (The alu dust cover has some scratches - see pic).

    It has no transportation box.

    I send by DHL and I reckon 200 euros covers most of Europe including insurance.

    More pics available on request of course.

    I'm asking 3800 euros plus shipping.

    /Jesper

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  2. I agree with what is said above by other members.  It's been some time since I used my Canon DSLR so my advice about stacking was not clear. I assumed a run with the filter and another without it.

    Sorry for the confusion.

    As to the rain effect, I'm sure you can search for 'rain' or something and find some threads on the topic.

    /Jessun

  3. I'd say that is a 'normal' result looking at the time and number of subs. DSLRs often produce these rain like streaks and I never found a good way around it in processing. I had some software that had an anti-streak routine but can't remember which one it was. 

    For stacking, you are limited by your data. With that I mean that after stacking you will be able to pull out whatever it is you are looking for. But for this target, very Ha rich, I see no reason why you couldn't stack the whole lot AND separately stack the red channel to have a look at what's in there. You can use this as a separate layer, if layers are something you are familiar with.

    /Jessun

    • Like 1
  4. APM Mini Guiding Scope 60mm Deluxe Finder Scope/ Lodestar combo for grabs.

    From the scope manufacturer:

    "The focuser is a precise helical type with a millimeter scale and 8 mm focusing travel. The backfocus is 20 mm max.
    Precise helical focuser
    T2 thread
    Locking screw at focuser
    Guiding cradle rings with dovetail
    For all 1.25" eyepieces (straight)

    Specifications:

    Type of telescope:

    Achromat Refractor

    Lens:

    Achromat

    Color:

    black / white

    Tube material:

    Aluminium

    Aperture:

    60 mm

    Focal ratio:

    f/4

    Focal length:

    240 mm

    Coating:

    Multicoated

    Backfokus:

    20 mm

    Focuser:

    Helical Focuser with 8 mm Travel

    Connection to eyepiece:

    1.25"

    Tube diameter:

    63 mm

    Length during observing:

    252 mm

    Dewcap diameter:

    72 mm"

    Included accessories:

    Tuberings and Dovetail Rail"

    Thrown in is a Starlight Xpress Lodestar guide camera, mini usb and guide cable plus a cable retention piece. 

    I'm asking 280 euros / 260 GBP, shipping excluded

    /Jessun

     

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  5. Yes of course. I 'downgraded' from three Atik 460s, running a successful triple rig and bought this kit instead to run a single scope but with a single larger CCD. During this period we had a baby and I stopped doing AP. I needed the sleep. We then moved to a different place with more bedrooms but with no place to set up a rig... 

    I sold my Astro-Physics mount some hours ago and it's all going. More to come.

    As I write the kit advertised is pending payment.

    Thanks for looking

    /Jesper

    • Like 2
  6. vlaiv, I think it's easy to do away with numbers and pixels to grasp the basic concept of F ratio. The number is a fraction with no end to the decimal places, and it has no unit. 

    Then we put something tricky to observe in front of the lens and something even trickier (a sensor) at the focal plane and practical matters kick in in abundance.

    I enjoy these discussions but I don't want to be the broken record on the subject...

    It's often the case that your OTA slips, the sensor ices over, the laptop crashes or clouds gathering above etc, way before you really have to lose sleep over the F ratio of the rig...

    /Jessun

  7. I agree vlaiv. It's just optics and the 'sensor' should be though of as a white postage stamp rather than something that is segmented.

    Well done on the train question. It's just one of those riddles that only has a ratio at heart. 4 people ever solved it during the day I flew with them. One guy put in the speed of sound in a series of equations and came up with a number of miles. The simple ratio never clicked.

    /Jessun

  8. You are right vlaiv as far as I'm educated. All practical considerations when it comes to taking an actual image are as we all know making it an almost impossible task.

    It is just so fundamental to understand F ratio at its core. Noise, pixel size, well depth etc are merely the constraints we have to deal with and don't quite play a part in understanding F ratio. There is for instance no F ratio myth as often proposed. 

    As a side note I have attached an pic that I have drawn for most of the pilots I ever flew with. Some 3000 to date.

    Riddle:

    A man is fishing on a bridge. He is positioned one third in on the bridge. When he detects a train approaching he knows he has to vacate the bridge. He can either go to the left and Juuuuust miss being hit by the train or he can go to the right and Juuuuuust miss being hit.
    The man will walk at a pace of 6km per hour as he departs.
    Question, what is the speed of the train and how far away is it when he starts walking? You can answer in a unit of your choice if you don't like the metric system.

    /Jessun

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    • Like 1
  9. vlaiv, I really like your thinking and you have the skill to formulate a model that works very well for you.

    I gathered that the OP wanted to go down to the logical basics, and for a more logical approach I think it's important to just accept it for what it is. A simple ratio between two measurements. The only other ratio I deal with daily is Mach number. It also has no unit. Mach is not a unit, although Americans often say something like "2 Mach". Don't ask me why this is. It's Mach 2. Ratio 2. Mach 2 is the same for a Lockheed aircraft or a Northrop aircraft. It's an absolute. Just like all F x telescopes are all equal.

    F ratio is just the same. It does away with any maths anyone cares to throw at it. 80/10=8. No number is more important than the other. 80 is no more magic than 10 etc. The troubles only begin when we put a finite pixel at the business end and start drawing conclusions, or go down the route that astrophotography is somehow different from normal photography just because we have some very bright, small stars in the mix.

    /Jessun

     

     

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