Aluma 47-10 Body Thread

Discussion in 'Aluma Series' started by RussD, Jul 3, 2019.

  1. RussD

    RussD Standard User

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    Hi,
    I am investigating the Aluma 47-10. But I want to see if it can be mounted properly to my current filter wheel. I want to see if I have the correct adapter. In the images it looks like there is a female thread on the camera body. What size thread is that?

    Thank you!

    Russ
     
  2. Colin Haig

    Colin Haig Staff Member

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    Thread size is a T-thread (M42 x 0.75)
    The bolt holes are 4-40 in a 1.600 inch square pattern
     
  3. RussD

    RussD Standard User

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    Hi Colin,
    Thanks!
    So if I want to connect an Aluma camera to a the Aluma FW8s with the least amount of backfocus possible, what adapters would I need? I would like to have a female T-thread on the scope side of the filterwheel.

    Thanks
    Russ
     
  4. Colin Haig

    Colin Haig Staff Member

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    Instead of using your existing FW, and you want to use an Aluma filter whel, the the filter wheel replaces the front of the camera.
    If you download the manual:
    http://diffractionlimited.com/downloads/AlumaUsersManual.pdf
    Look at page 9 and 11.

    The scope facing side of the filter wheel will take an adapter. See top picture on Page 10.
    For example:
    http://diffractionlimited.com/product/adapter-plate-t-thread/
    or
    http://diffractionlimited.com/product/adapter-plate-2-156-x-24-thread/

    What's the scope? e.g 12 inch f/10 ?
     
  5. RussD

    RussD Standard User

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    Hi Colin,
    Excellent. I see now. The scope is a 20" Planewave CDK operating with the 0.66 focal reducer. So that ends up being about f 4.5.

    I have been using a ST10XE with a 8 position Xagyl filter wheel now. It has been a workhorse camera but I need the added cooling ability in the updated Aluma. The scope has pretty limited backfocus, but I have a T thread adapter that attaches to the focal reducer and that keeps everything pretty tight. The backfocus of the filter wheel is just less than an inch, the ST10 is about the same.

    What is the backfocus of the Aluma with the FW8s with the T thread adapter on the FW?

    Thanks

    Russ
     
  6. Colin Haig

    Colin Haig Staff Member

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    Standard filter wheel (FW8S-Aluma) or self-guiding filter wheel (FW8G-Aluma) ?
    What filters (ours or yours?) eg 2mm thick or 3mm thick, as we have to allow about -0.6 to -1.0mm for the refraction.
    The Teledyne sensors are a little bit different in height and are windowless.
    I have a number, but want to double check when I get your info and run it past a colleague.
     
  7. RussD

    RussD Standard User

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    Hi Colin,
    The Standard filter wheel. The photometric filters I have are 3mm thick typically.

    Russ
     
  8. Colin Haig

    Colin Haig Staff Member

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    Hi Russ,
    An estimate would be around 40-44mm, but I want to get you precise information.
    My colleague has to get back to me, and I'm afraid it will be Monday our time before we can get back to you.
     
  9. RussD

    RussD Standard User

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    Hi Colin,
    Thank you. That should be fine.

    One more somewhat different question....

    I do photometry imaging 100% of the time. So all sources of noise need to be minimized. On my ST10XE I usually go for -15 to -20c cooling for best results. This time of the year I struggle for -15c.

    Another and a lot less expensive option would be to purchase an Aluma 3200 and bin it 2x2. This is essentially the same configuration I use now.

    Can you assist me in comparing the Aluma 47-10 and the Aluma 3200?

    It appears the 47-10 has significantly greater dark current. I see older graphs from SBIG online that show dark current vs temp for the Marconi 47-10 and the KAF-3200 which show that at -20c the the KAF-3200 outperforms the 47-10 at that temperature even when the 3200 chip is binned 2x2. (http://www.company7.com/library/sbig/sbwgifs/3200ME_marconi_dark_chart.gif) Is this still the case with the current 47-10 compared to the current chips in the 3200?

    But the read noise of the 47-10 is about half of the 3200. So I am not completely sure how to compare the two cameras.

    In terms of QE, the 47-10 seems to come out on top but it seems not by much.

    Can you assist me in quantifying the difference?

    Thanks

    Russ
     
  10. Colin Haig

    Colin Haig Staff Member

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    Russ,
    Short version: e2v outperforms KAF-3200 at low temps. Aluma 47-10 definitely outperforms your current camera. Aluma design makes it possible.
    Long version: read on.
    What's your nighttime ambient temperature like? (20C?)
    The ST-10 family can cool (at best) to delta T of -35C with air. So if it's 20C out, then -15C is the maximum you'd get. So you may not be getting the best dark current out of the old camera's sensor anyway.

    You are correct, the Teledyne e2v CCD47-10 AIMO read noise is very low (really excellent),
    Yes the QE is better - I think in the CCD47-10 is a back-illuminated sensor, and the 3200 is old-school front illuminated.
    This is in part why the 47-10 performs so well in QE, and in my opinion the 3200 is probably the best chip from the Kodak heritage.
    The 47-10 electron well depth is a huge 100,000e- vs the ~55,000e- for the 3200. Pixel size strongly influences this. With your scope, the bigger deeper pixels would be an advantage I think.

    Dark current - the data sheets can be confusing.

    Cooling is critical for sensors like the Teledyne e2v CCD47-10 AIMO device.
    The dark current drops off rapidly for this chip once it gets cold.

    The Teledyne e2v data sheet specs are at 293K (which is 20C room temp, instead of 25C or 0C used by ON Semi - two values in same data sheet). So the numbers look scary at those temps.
    To calc the dark current, they provide an equation in Note 2.
    I've done the math:
    273K (0c), it is down to 20 e-/p/s, instead of 250.
    253K (-20C), it is about 1.19 e-/p/s;
    243K (-30C ) it is about 0.24 e-/p/s which is excellent. I tried to use the ON Semi guidelines for your old camera, and get 0.21, so it's a dead heat so to speak.
    I tried to do the Kodak dark doubling extrapolation down to the same -30C, but the math doesnt seem right - eg to do the calculation for the Aluma 3200, I get a number of less than .1, so not sure how accurate ON-semi's "guesswork" 6C doubling temp is (I don't think it is linear, and can't find any supporting data. The e2v isn't linear, as expected). So even with an Aluma 3200 dark current being a touch lower at the same temp, the read noise kills it. Winner: e2v CCD47-10.

    The ON Semi chip data sheet is spec'd at 0C, (a lot cooler than the data sheet chart for the e2v), with a 6C dark doubling temperature.
    Just looking at the data sheet isn't entirely fair unless you understand how the dark current falls off and follow both data sheets info in their notes.

    A bit of history and data:
    Teledyne bought eev, makers of the CCD 47-10, and there have been refinements. The new company is Teledyne e2v.
    ON Semiconductor bought Truesense/Kodak, makers of the KAF-3200 series.
    The KAF-3200 is probably the best of what ON Semiconductor makes, of Kodak/Truesense heritage. The chip can be cooled to a maximum of -30C.

    Manufacturer Data Sheets:
    https://www.e2v.com/resources/account/download-datasheet/1256
    https://www.onsemi.com/pub/Collateral/KAF-3200-D.PDF

    On the basis of the analysis above, the Aluma U47-10 is the performance winner. I see that reflected in the buying behaviour - the professional astronomers and advanced non-professional (skilled amateurs) are buying the 47-10.
    If it were a bang-for-the-buck challenge, it is a tight race. The 3200 chip is pricy, but not as much as the 47-10.
    For what you're trying to do, especially after investing in a high-caliber instrument like that 20inch Planewave, I'd go Aluma 47-10.
    If you really are on a tight budget, and you are purely looking to replace the ST-10, the Aluma U3200 will perform better than your current camera

    I hope that helps.
    Colin
     
  11. RussD

    RussD Standard User

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    Hi Colin,
    Thanks. Cooling is the kicker for this. My location is in Texas. For four months out of the year night time temps start near 30 to 35C and dipping to 20c or so for a low.

    Your estimates are correct for the ST series. Lately I have been getting down to about -10 to -15C when starting at about 25-30C. If the delta on the Aluma cameras is 50c, I think for those four hot months, I can assume getting to -20c is reasonable.

    During the winter, I can easily get to -20c or cooler on occasion. Budgeting is still in process, but my main goal is to get the best camera for the purpose of quality photometry.

    Thanks.

    Russ
     

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