Re: [APML] Strange Star Artifacts in Takahashi FSQ-106N Image

["D. Kodama" <kodama@alumni.caltech.edu>]

Michael,

That was a film shot.  Medium format Kodak E200, 20 minutes with a Pentax
67 body.  The scope was an AP155 with older 2.7" flattener.  I understand
the newer flatteners do not have the reflection problem.

Dave



> Dave,
> Yours looks more like a internal reflection with a CCD rather than the
> diffraction effect.  Is it CCD?
>
> Michael Cole
> UrbanImager Astrophotography website
> http://home.earthlink.net/~urbanimager/index.htm
>
>
>
> D. Kodama wrote:
>
>>Chris,
>>
>>It may not be due to spacers, but here's a shot from an AP155 that shows
>>the same effect (plus an internal reflection from the flattener):
>>
>>  http://www.eanet.com/kodama/astro/misc/apvega2.jpg
>>
>>I do find it interesting that the orientation of the artifacts in Wade's
>>shot depend on the position in the FOV.  It's not what I would expect
>> from
>>a diffraction effect.
>>
>>Dave
>>
>>
>>
>>
>>
>>
>>>Hello Wade -
>>>
>>>I have a FS102 and get the same artifact on bright stars.  I posted the
>>>same
>>>type of question here on the APML about a year ago and the consensus
>>>(although not a 100% sure answer) was that the three silver objective
>>>spacers on Tak refractors, they are in the light path, are creating this
>>>artifact.
>>>
>>>Here is a shot of Jupiter & M44.  Note the effect on Jupiter.
>>>
>>>http://www.abmedia.com/astro/dsc2/m44-jupiter.html
>>>
>>>This seems to only happen on Tak refractors.  A-P scopes do not use
>>> these
>>>spacers.
>>>
>>>Chris
>>>
>>>-----------------------------
>>>Chris Cook Photography
>>>www.cookphoto.com
>>>
>>>
>>>----- Original Message -----
>>>From: "Thomas W. Earle" <twade@bmi.net>
>>>To: <astro-photo@seds.org>
>>>Sent: Saturday, February 19, 2005 5:27 PM
>>>Subject: [APML] Strange Star Artifacts in Takahashi FSQ-106N Image
>>>
>>>
>>>
>>>
>>>>I recently got all my Comet Machholz images back from development.
>>>>They turned out really well.  I'll have them scanned probably in the
>>>>next month or so.  In the interim, I discovered that my Takahashi
>>>>FSQ-106N has a problem with bright stars.  I have included the
>>>>following link for people to look over.
>>>>
>>>>http://www.northwest-landscapes.com/html/StrangeStars.html
>>>>
>>>>Does anyone have any idea what could be causing this strange
>>>>phenomenon?  The "radial shadows" appear to "rotate" with the field
>>>>of view.  For example, the shadow in the lower left star of Orion's
>>>>belt is oriented southwest to northeast, the middle star's "shadow"
>>>>is oriented west to east, and finally the upper right star is
>>>>generally northwest to southeast.  It is very strange indeed.  Could
>>>>I have a bad field flattener?  Has anyone else experienced this
>>>>strange behavior with bright stars?
>>>>
>>>>Thanks in advance,
>>>>
>>>>Wade
>>>>
>>>>
>>
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>
> --
>
>
>

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