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Review: William Optics Star 71

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#51 nodalpoint

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Posted 05 September 2014 - 02:15 PM

There's a cut-away diagram from the Agena Astro site:

 

wo-star71-6s_1.jpg


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#52 zsb04

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Posted 05 September 2014 - 07:46 PM

first light with the scope. m31 andromeda galaxy 18x 120seconds unguided at iso 800 using a cannon eos t3i. I only managed 5 darks at the end, then the camera battery died :(  4th ever attempt at astrophotography and my best one yet, Only issue i have with the scope is the tube rotates pretty easily within the rings, even when clamped down, i am thinking some extra felt will help? any ideas?

Attached Files


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#53 zsb04

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Posted 05 September 2014 - 07:49 PM

also, is it just me or are the stars on the left of the image blue and as it transitions to the right they are red?  that can't be right lol



#54 Denimsky

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Posted 05 September 2014 - 08:31 PM

Thank you for the information Timm and nodalpoint.

 

Is there anyone using this scope with a full frame 35mm size camera?



#55 Orion58

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Posted 14 September 2014 - 08:57 AM

 Only issue i have with the scope is the tube rotates pretty easily within the rings, even when clamped down, i am thinking some extra felt will help? any ideas?

 

Yes, that's all you need.



#56 xb39

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Posted 06 October 2014 - 07:49 AM

Hi,

as I'm still collecting photons for my first light with the WO Star-71 it was a welcome relief to make some picture of the moon and the sun in white light. This was also my first light at sun and moon.

 

I started with my full frame DSLR Canon EOS 6D (ISO 100, 1/2000s / stacked 15 out of 25 ):

 

get.jpg

 

Taking into account that the FOV of the scope attached to my Alccd5L-IIm is ideal for imaging the whole sun (or moon). Here are some pictures (1280x960):

 

get.jpg (600 out 1000 frames stacked)

 

get.jpg (Area of 320x240)

 

And here is a lucky shot of a plane (animated gif):

 

get.jpg

 

After this imho very promising first sun light I did some improvements (use of green filter and UV/IR cut filter, flat and dark substraction). Here are the results:

 

get.jpg (1280*960, 1400 frames stacked)

 

get.jpg (320x240)

 

 

And here is a picture of the moon:

 

get.jpg (1280*960, 600 frames stacked

 

The details for a scope with 348 mm focal length are not that bad taking into account that the Alccd5L-IIm works not at its optimum regarding f-stop (undersampled).

 

O.K., this is really not the scope was made for but if you have only cloudy nights during deep sky imaging you can try something fully different ;)

 

Best regards

Stefan

 



#57 OrionSword

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Posted 18 October 2014 - 10:46 AM

I was able to recently get first light in Ha with 4x10minute frames before clouds became attracted to the scope.  This is the area around M52 with the Bubble nebula.--Added 7 more subs to it last night, now 11x10min.

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Edited by OrionSword, 20 October 2014 - 05:13 PM.

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#58 lakeorion

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Posted 21 October 2014 - 02:23 PM

Owners - If one were to fit a film solar filter on the front, what diameter would one choose?  Or, what is the OD of the dew shield?



#59 OrionSword

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Posted 21 October 2014 - 05:14 PM

Owners - If one were to fit a film solar filter on the front, what diameter would one choose?  Or, what is the OD of the dew shield?

 

93mm OD.



#60 OrionSword

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Posted 22 October 2014 - 06:24 AM

Here are the curvature and tilt measurements.  Slight tilt favors the bottom at 180deg.  The two brass screws on the top of the focuser are set soft, so they still have some tweak room in my case.  I have about a 4# load on my focuser with a ST8300m and  Starlight Express 5x2" filter wheel.

 

 

Attached Files



#61 OrionSword

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Posted 22 October 2014 - 06:28 AM

Here is the flat analysis.  Light fall off fairly slight and at most 6% in corners of the KAF8300 chip with 2" filters in service.

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Edited by OrionSword, 23 October 2014 - 06:11 AM.

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#62 bjgiii

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Posted 22 October 2014 - 05:57 PM

I'm using a dslr with my scope. Are these scopes limited to a clip in filter like the ones manufactured by Astronomik for a dslr? Or are there other mounting options for a filter?



#63 gatsbyiv

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Posted 22 October 2014 - 06:24 PM

I'm using a dslr with my scope. Are these scopes limited to a clip in filter like the ones manufactured by Astronomik for a dslr? Or are there other mounting options for a filter?

 

There is internal threading for a 48 mm filter.  timmbottoni posted some images of this on the second page of this thread.  



#64 zsb04

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Posted 22 October 2014 - 09:48 PM

here is my second try at m31 using star71, much more detail and much more integration time

http://www.astrobin.com/122697/



#65 N1ghtSc0p3

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Posted 27 October 2014 - 07:42 PM

 

Hi - see this post where I commented on how to adjust the focuser to get rid of any sag due to the rotation mechanism - http://www.cloudynig...6621825/page...

Timm


The same treatment to the focuser's rotator may need to be applied to some Star 71s. I got sharp images the first time I took one of mine out. The second night, the top 30% of the field was out of focus. I had loosened the rotator to turn the camera 90 degrees, then re-tightened it.

There is about a millimeter of play in the ring that facilitates rotation when the screw is loosened. This can allow the camera to "sag" or hang at a very slight angle. This put the top of the sensor about a millimeter further back than the bottom. At f/4.9, the zone of critical focus is narrow.

You have to be careful that when you re-tighten, you don't lock in that small amount of sag. I found that when adjusting rotation, I can simply push inward on the camera while re-tightening the rotator screw to prevent sag, but your solution sounds more permanent.

 

 

So I have a question.  I'm using a Hap Griffin modded Canon XSi (Astrodon UV/IR cut filter), and I was imaging NGC7000 a couple weeks ago.  Stars at the center of the FOV are nice, but if there are bright stars near the edges I get reflections.  I emailed the following pic to Hap, and he suggested I try taking some shots of something like M45, with the camera in different orientations (say at 0, 90, 180 and 270 degrees from level when parked) to see if the reflections follow the orientation.  I'm planning on doing that tonite, but was wondering if anyone else thought the above procedure would help?  (BTW - This image was taken with the camera "level" when the scope is parked and looking at Polaris....if that helps.)

 

Attached File  Screen Shot 2014-10-22 at 11.13.30 PM copy.png   448.15KB   2 downloads

 

Thanks!!



#66 N1ghtSc0p3

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Posted 28 October 2014 - 08:32 PM

Also, has anyone ever seen a manual for this scope?  Mine didn't come with one, and I figured WO would have one on their website....but no joy there, either. 



#67 gatsbyiv

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Posted 28 October 2014 - 09:25 PM

 

 

Hi - see this post where I commented on how to adjust the focuser to get rid of any sag due to the rotation mechanism - http://www.cloudynig...6621825/page...

Timm


The same treatment to the focuser's rotator may need to be applied to some Star 71s. I got sharp images the first time I took one of mine out. The second night, the top 30% of the field was out of focus. I had loosened the rotator to turn the camera 90 degrees, then re-tightened it.

There is about a millimeter of play in the ring that facilitates rotation when the screw is loosened. This can allow the camera to "sag" or hang at a very slight angle. This put the top of the sensor about a millimeter further back than the bottom. At f/4.9, the zone of critical focus is narrow.

You have to be careful that when you re-tighten, you don't lock in that small amount of sag. I found that when adjusting rotation, I can simply push inward on the camera while re-tightening the rotator screw to prevent sag, but your solution sounds more permanent.

 

 

So I have a question.  I'm using a Hap Griffin modded Canon XSi (Astrodon UV/IR cut filter), and I was imaging NGC7000 a couple weeks ago.  Stars at the center of the FOV are nice, but if there are bright stars near the edges I get reflections.  I emailed the following pic to Hap, and he suggested I try taking some shots of something like M45, with the camera in different orientations (say at 0, 90, 180 and 270 degrees from level when parked) to see if the reflections follow the orientation.  I'm planning on doing that tonite, but was wondering if anyone else thought the above procedure would help?  (BTW - This image was taken with the camera "level" when the scope is parked and looking at Polaris....if that helps.)

 

attachicon.gifScreen Shot 2014-10-22 at 11.13.30 PM copy.png

 

Thanks!!

 

The size of the halo is determined by the distance between the surfaces on which the light is reflecting.  Starizona has a page that shows you how to calculate the distance based on the size of the halo.  This looks like reflection between two fairly close surfaces.  Usually, it's between the filter and the sensor, but perhaps this is between two other elements?  The off-center nature of the reflections is odd, supporting a potential reflection between two elements further away from the sensor.  And is that a double reflection on the top of the image?



#68 N1ghtSc0p3

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Posted 28 October 2014 - 10:47 PM

Hi Charlie,

 

Yes, that is a double reflection at the top of the image (on the orange star.)  I've emailed my updated photos to Hap, still waiting to hear back from him.  I'm wondering if it might also be something in the unit that rotates the camera and is supposed to keep the focus and alignment the same? 



#69 N1ghtSc0p3

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Posted Yesterday, 11:05 PM

Also, something else I noticed today with the included Canon adapter...

 

if you hold the adapter up and look along the flat faces (i.e. not the side that connects to the camera, but the side that screws on to the M48 threads), there's an inner ring and an outer ring.  These are not (as far as I can tell) screwed together, but rather held together (and thence aligned) with set screws.  I noticed that on mine, one side of the inner ring is ever so slightly above the outer ring (its impossible to measure, but I can catch my fingernail on it), while the other side, 180 degrees opposite the 'high' side, is ever so slightly below the outer ring (again, I can't measure, but I can feel it with my fingernail.  

 

I'm wondering if this is *just* enough out of square to cause the reflections in the photos above?  I'm going to have a go at loosening the setscrews and seeing if I can realign the inner ring so that its face is flush with the outer ring. 

 

Short of that being the issue, I'm also going to look at the rotator setup and see if those set screws are causing some misalignment or tilt.    Hopefully the next clear night I'll also try mounting my camera on my AT72ED to see if I can replicate the reflections. 








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