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

["Don Westergren" <westergren@nethere.com>]

Jim and all,

My FSQ-106 is an early model before the 106N came out.  It doesn't have any 
tabs near the objective.  But I do get the bifurcated bright stars when the 
stars are near the edge of the FOV (of a 35mm camera).  I have accepted them 
rather than try to "fix" them.  I have shot the Flame/Horsehead using the 
FSQ with a Canon 10D and Alnitak is bright and round, without bifurcation, 
near the center of FOV.

Obviously this is common to many refractors and does not indicate problem 
with any one scope.

Don

----- Original Message ----- 
From: "Jim Janusz" <jjanusz@dc.rr.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Saturday, February 19, 2005 3:53 PM
Subject: Re: [APML] Strange Star Artifacts in Takahashi FSQ-106N Image


> Hi Wade,
>
> I pretty sure I know the cause of this problem.  It's caused by the small 
> metal tabs on the front of the objective.  They are in the light path and 
> very bright stars will show this.  It has been reported on other Tak 
> scopes. I can't understand why they don't get them out of the light path 
> as a refractor should not do this.
>
> If I remember right this was discussed either on the Astro Physics list or 
> another list I belong to.
>
> I know this doesn't make you feel better but at least you know.
>
> Jim
>
> ----- Original Message ----- 
> From: "Thomas W. Earle" <twade@bmi.net>
> To: <astro-photo@seds.org>
> Sent: Saturday, February 19, 2005 2:27 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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