RASC Hamilton Getting a DSLR modified...

[Andy Blanchard]

Roger please tell us more about you lens modification?

Andy Blanchard
905-465-2031H
905-847-7777B

On 2012-07-01, at 5:15 PM, "Roger Hill" <Roger.Hill at hiteach.net> wrote:

> Hi, Mark...
> 
> The factory default filter that Canon uses for it's regular cameras results in a spectral response that is an odd shape.  The filter is veryu good at blocking out UV, but letting blue through.  It has a very sharp dividing line betrween them.  The other end of the spectrum is not as good.
> 
> At the red end, the response gradually tails off, which results in only a 20% respose at the Hydrogen Alpha line.  This is not good!
> 
> The Astrodon filter is a visible light only filter (until about 1200 nanometers, but by then, the CMOS chip is extremely insensitive, so it dowsn't matter).  This filter has a very sharp cut off not only at the UV end, but also at the IR end, as well.
> 
> At 390nm, the filter is essentially opaque, rising to 99% passthrough at 400nm.  It remains at 98-99% transparency until 700nm and is back to opaque at about 710nm.
> 
> I certainly hope it works with lenses...I have a 300mm f/4 SMC Takumar I recently took apart and put back together to allow it to focus at, and beyond, infinity. 
> 
> Roger
> 
> 
> -----Original Message-----
> From: astronomers-bounces at hamiltonrasc.ca on behalf of Mark Kaye
> Sent: Fri 29/06/2012 9:36 AM
> To: astronomers at hamiltonrasc.ca
> Subject: Re: RASC Hamilton Getting a DSLR modified...
> 
> At 22:35 6/28/2012, you wrote:
> 
>> He also offers a choice of two different replacement filters.  One is
>> made by Baader and the other by Astrodon.  These filters allow you to
>> use the camera for normal daytime use, as long as you use a custom white
>> balance.  The Astrodon filter is $30 more expensive, but Astrodon has a
>> superb reputation for producing the highest quality filters for
>> astronomical use.  So, despite my predilection for choosing the less
>> expensive items, I went with the Astrodon filter.
> 
>    I own a Baader IR/UV blocking filter.  It is completely clear to 
> the unaided eye, but I know it blocks IR as I have a web cam that is 
> not chip filtered for IR and with some lenses, it washes out 
> completely due to IR, but when I put the Baader filter in front, it 
> works normally.  Some webcams filter the chip and let the lens be 
> unfiltered, while others filter the lens and leave the chip 
> unfiltered.  That makes some cameras unsuitable for using with IR 
> illumination, if the chip is filtered.
>    Does the Astrodon filter IR?  I cannot use my refractor for CCD 
> work unless I filter out IR and UV.  While the scope is beauty 
> focusing visible light, it quickly goes into out of focus once you 
> get outside of the visible range, especially at the red end and makes 
> the scope very hard to focus.  I suspect that unless IR is filtered, 
> most lens systems will not give sharp images.  Of course, mirrors are 
> not affected by this, but Schmidts and Maks are.
> 
>> After two days of no updates, and with visions of modified cameras being
>> lost, this evening, it showed up in Miami!  Apparently, though, it's
>> normal for the US Postal Service to send things hundreds of miles out of
>> the way.
> 
>    You have to love express service.  I bought a base for my C11 and 
> had it shipped express because I wanted it by the end of the week 
> when I was travelling down here to install it.  It did not arrive in 
> the "guaranteed" delivery time or two days later, for that 
> matter.  It arrived sometime during the week I was away and because I 
> was not at home to get the package, I then had to go to the post 
> office to get it.  The express mailing rate was more expensive than 
> the part and while they guarantee delivery, it is an empty 
> guarantee.  They only guarantee that I will get it, on what ever time 
> frame they wish, despite the huge extra bucks they charge.  I got the 
> parcel, so what do they care?  The one advantage of the postal 
> service is that there is not a bondage fee to pay for storing the 
> item at the border while they delay your shipment.
>    Good luck with your package.  Since the company that shall not be 
> named believes Canada is in the southern hemisphere, maybe it is a 
> myth for all of California and your package is in Miami because that 
> is about as far south as you can get before shipping it to the nether 
> regions.  Just what you wanted to hear...
> 
>    Clear skies!
>                MK
> 
> The Observatory by the Lake
> http://www3.sympatico.ca/mark.kaye/index.htm  
> 
> <winmail.dat>
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