[Aavso-photometry] binning considerations

Tue Jun 12 01:14:51 EDT 2007

For those not familiar with Lumogen, it is a UV fluorescent dye. Painted in 
a thin film over the chip, it absorbs UV photons and re-emits them at a 
longer wavelength where the chip can detect them with higher QE. The only 
problem with Lumogen is that is decays with time. It is good for at least a 
few years. I have heard stories about it showing noticable loss in 
effectiveness not long after that.

Michael Newberry

----- Original Message ----- 
From: "Wolfgang Renz" <w_renz at onlinehome.de>
To: "David Trowbridge" <David at tinyblue.com>
Cc: "AAVSO-PHOTOMETRY" <aavso-photometry at mira.aavso.org>
Sent: Monday, June 11, 2007 9:57 PM
Subject: Re: [Aavso-photometry] binning considerations

> Hi David
>
> If you really consider serious U Band photometry a mirror-only
> scope will be the best choice as any glas (if its not quarz or
> fused silica will absorb 100% somewhere in the range of
> 300-400nm) and its coating (usually optimized for the visual
> range and reflecting more than uncoated glas in the NUV
> and NIR) will absorb most of the far NUV light in the U band
> (e.g. Jeff Hopkins gets about twice as many photons in the U
> band with his good old orange C8 than with his new M8 with
> UHTC).
> But some "advanced" (for the visual range) mirror coatings
> have also a worse reflection in the NUV. So its always a
> good idea to ask the vendor for details before buying some-
> thing.
>
> The SBIG CCD chamber entrance window (should be MgF2
> coated BK7) is not as limiting as the Kodak chip sealed MAR
> cover glass (Multi AR coated). For U band photometry one
> without a cover glass would be advisable.
> Other CCD camera vendors than SBIG (like FLI) also sell
> Kodak chips without cover slip and lets one the choice
> between different materials for the CCD chamber entrance
> window.
>
> The Kodak ME chips have a higher QE in the NUV than is
> explainable by the microlenses. So there must going on
> something like fluorisence and/or a much better UR AV
> coating. They ME chip are already nearly sufficient for U
> band photometry. Better would be of course an UV AR
> coated or Lumogen coated chip (like e2V chips available
> via Apogee) but these are not common with amateurs.
>
> Clear skies
> Wolfgang
>
> -- 
> Wolfgang Renz, Karlsruhe, Germany
> Rz.BAV = WRe.vsnet = RWG.AAVSO
>
>
>
> ----- Original Message ----- 
> From: "David Trowbridge" <David at tinyblue.com>
> To: "AAVSO Photometry" <aavso-photometry at mira.aavso.org>
> Sent: Monday, June 11, 2007 8:14 PM
> Subject: Re: [Aavso-photometry] binning considerations
>
>
>> Thank you Gary and Arne for your very helpful comments.
>>
>> Mike, yes actually I had been looking at the Meade LX200R
>> series. I could get a bigger aperture for the same money with
>> the Meade. But I thought maybe I could do better CCD photo-
>> metry (presently BVR, but extending to U and I filters) and
>> possibly infrared photometry (Optek's SSP-4) or spectroscopy
>> over a wider range of wavelengths, on a system like the 10"
>> Tak Mewlon which has no glass secondary (Only two mirrors
>> in the Dall-Kirkham Cassegrain). Do you know anyone with
>> experience using the LX200R for photometry?
>>
>> By the way, I'll be mounting the new OTA on my new Paramount
>> ME, in parallel with my Tak FSQ. What a treat that mount has
>> been! With my old mount, I had to discard maybe 30% of my
>> images because of jiggles and shakes, now I can keep nearly
>> all the images I take! And no tangled cables anymore. Wow!
>>
>> David
>>
>>
>>
>> -----Original Message-----
>> From: mlfleenor at charter.net [mailto:mlfleenor at charter.net]
>> Sent: Monday, June 11, 2007 7:28 AM
>> To: David Trowbridge
>> Subject: Re: [Aavso-photometry] binning considerations
>>
>> Hi David,
>>
>> Sold on those Taks are we?.. I have an FSQ and love it for pretty
>> picture imaging but for photometry I have to say that an SCT serves
>> the need admirably. Especially considering the new corrected
>> LX200R series from Meade I'd be hard pressed to recommend
>> anything else-except maybe a large newt.
>>
>> You'll probably discover that your seeing numbers will likely improve
>> with a bigger scope. Smaller pixels will also let you take advantage
>> of good nights. They will not seriously degrade photometry on poor
>> nights either. Binning 2x2 works  really well but I'd be cautious of
>> 3x3 as a saturated pixel or two can really throw your precision off.
>>
>> I use a Meade 14 gps ota with an ST10XME and 2x2 binning running
>> with a telescompressor and achieve excellent photometric results.  ( I
>> often achieve 1mmag precision working with exoplanet candidates.)
>> I highly recommend this camera for photometry although you won't go
>> wrong with the ST8 either. You will need to watch for saturation when
>> binned.
>>
>> The ST-9 depsite it's hype is better suited for astrometry and SN
>> patrols. The fov, lower noise and spectral response make the ST8
>> a better choice  for photometry imo.
>>
>> Mike
>>
>> --
>> Mike Fleenor
>> Volunteer Observatory
>> Knoxville, TN
>> www.mikefleenor.com
>>
>>
>>
>> ---- David Trowbridge <David at tinyblue.com> wrote:
>>> When doing photometry, is it okay to freely use 2x2 or 3x3 binning to
>>> achieve the desired image scale?
>>> Where I live, the seeing is generally not better than 2 arcseconds I 
>>> don't
>>> think.
>>> The photometry I've been doing so far has been with an SBIG ST-7E
>>> camera on a Takahashi FSQ-106 4" refractor which has been giving
>>> me 3.5 arcseconds/pixel at f/5 or 2.2 arcseconds/pixel at f/8.
>>> Now I plan to upgrade to a larger scope for greater light grasp and a
>>> new camera for faster download times. I'm considering the Takahashi
>>> Mewlon 250 and an ST-8XME camera. Using 1x1 binning this scope
>>> would give only 0.62 arcsconds/pixel at f/12 and 0.80 at f/9.2. I think 
>>> I'll
>>> need bigger pixels.
>>> Will it work just fine to use 2x2 or 3x3 binning? Or should I consider 
>>> an
>>> ST-9 instead?
>>> Also, will going to a camera with microlensing have any detrimental
>>> effects on photometry measurements?
>>> Are there any other issues I should be aware of?
>>>
>>> David Trowbridge
>>> Tinyblue Observatory
>>> Whidbey Island, WA
>
>
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