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Astrophotography and Sketching >> Beginning and Intermediate Imaging

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David Ault
sage


Reged: 09/25/10

Loc: Georgetown, TX
Re: AT65EDQ and triangle stars new [Re: gapalp]
      #5030587 - 01/21/12 02:27 PM

Thanks Guys!

Regards,
David


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BKBrown
Post Laureate
*****

Reged: 08/23/09

Loc: Northern Virginia, USA
Re: AT65EDQ and triangle stars new [Re: gapalp]
      #5614317 - 01/09/13 07:14 PM Attachment (16 downloads)

I recently started imaging with an AT65EDQ I acquired some time ago. It is a sweet scope and provides simple and superb wide field imaging...but I have a problem. The image below is clipped from a series I shot of the Double Cluster last night and it appears to have the dreaded triangular stars that I had not noticed before. Now I am a newbie DSO imager, but it sure looks to me like the issue discussed in this thread. What do folks here think? If it could be something else, I would definitely like to know, if it is the retaining ring thing I am not shy about fixing stuff. Thanks for any thoughts or suggestions!

Clear Skies,
Brian


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David Ault
sage


Reged: 09/25/10

Loc: Georgetown, TX
Re: AT65EDQ and triangle stars new [Re: BKBrown]
      #5614418 - 01/09/13 08:01 PM

Brian,

It's hard to say if this is the same problem. It looks out of focus, was that intentional to highlight the issue? How long is this exposure? I used very short exposures to rule out tracking (5 seconds if I remember correctly).

Once everyone helped me diagnose the issue with mine the fix was quite simple. I had to remove the focuser, then remove the flattener assembly from the back of the OTA (the focuser screws into the flattener assembly which screws into the OTA). Once the flattener assembly is out you can get to the retaining ring on the flattener lens. I loosened mine in very small increments and tested between each change. It took a lot of assembly / disassembly of my rig, but was obviously worth it. I did think it was odd that that it was the flattener lens that was 'pinched' as it is a single lens and not a compound doublet/triplet arrangement, but it did work.

Regards,
David


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BKBrown
Post Laureate
*****

Reged: 08/23/09

Loc: Northern Virginia, USA
Re: AT65EDQ and triangle stars [Re: David Ault]
      #5614490 - 01/09/13 08:57 PM Attachment (14 downloads)

Thanks David, your info is quite useful. The exposure is 120 seconds at ISO 1600, so it is a long run...and yes it is highly enlarged. Below is the normal version for my reference file.

Clear Skies,
Brian

Edited by BKBrown (01/09/13 09:02 PM)


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Orion58
scholastic sledgehammer


Reged: 10/28/11

Loc: Southern Wisconsin
Re: AT65EDQ and triangle stars new [Re: BKBrown]
      #5615704 - 01/10/13 03:09 PM

As David mentioned, loosen the retaining ring on the flattener and that will probably do it - however, also be very careful not to tighten the actual mounting rings too much when putting the scope back on the mount. The rear ring is directly over the flattener.

The mounting rings fit like a glove but can exert a lot of force on the tube if tightened too much. Once I made both of these adjustments the triangular stars basically disappeared.

Hope this helps.


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