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Hyperstar v4 issue

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#1 bhawks99

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Posted 02 March 2021 - 11:54 AM

Hi all,

  I hope I have the correct forum for this question. Last night I connected my Canon T5i to my Hyperstar v4 lense and connected the lense to my Celestron EdgeHD 11" scope with a CGX mount. I was taking a practice sub of the Orion Nebula but kept getting what you see in the attachment. I used the Hyperstar lense last week and it worked fine so I am kind of stumped as to what could be causing this. Any help would be greatly appreciated. 

Thanks,

DaveSingle__0001_ISO800_3s2s__NA(1).png



#2 Tapio

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Posted 02 March 2021 - 12:02 PM

I see camera shadow and out of focus image.

At least it needs focusing.


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#3 bhawks99

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Posted 02 March 2021 - 01:06 PM

Soyuz,

   Thanks for your response. Are you saying the out of focus could be causing the camera shadow? I am just stumped because I used this lense last week and didn't encounter any kind of issue like this. Thanks.



#4 WadeH237

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Posted 02 March 2021 - 02:53 PM

Are you asking about the shape of the shadow in the center?

 

If so, that is the shadow of the camera, and is completely normal for Hyperstar.  As you focus the scope, both the stars and the central shadows will get smaller.  At focus, there won't be a central shadow.  Instead, there will be some diffraction effects from the shape of the camera.  That is also normal, and not something to worry about.

 

I'm a bit perplexed that you say that you didn't encounter this last week.  It will always be this way.


Edited by WadeH237, 02 March 2021 - 02:53 PM.


#5 bhawks99

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Posted 02 March 2021 - 03:23 PM

No I can see the shape is of the camera. I was wondering why I see 3 reflections of it but it sounds like the consensus is the focus is honked up. I will perform some focus adjustments tonight and let everyone know how it goes. Thanks for the help!



#6 WadeH237

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Posted 02 March 2021 - 03:29 PM

Is it possible that there are three stars, of different brightness, in the field?



#7 bhawks99

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Posted 02 March 2021 - 03:48 PM

I hadn't thought of that and it does make sense especially if the focus is off. Hopefully tonight will tell more. Thanks.



#8 gcardona

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Posted 02 March 2021 - 04:13 PM

That's what the Orion nebula looks like when its WAY out of focus. On the left is the Running Man, in the middle the actual Orion Nebula, and on the right NGC1980. What you are seeing is the bright stars that make up these regions.



#9 Noah4x4

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Posted 02 March 2021 - 04:27 PM

Hyperstar backfocus is incredibly sensitive and if you change camera you will see this effect. I have to use a completely different spacer when switching from Atik Horizon camera to ASI294, albeit we are only talking about 4mm difference. Might you have added a filter and a couple of mmm??

However, if using the same camera, same spacing this will simply be lack of focus.

Edited by Noah4x4, 02 March 2021 - 04:30 PM.


#10 Peterson Engineering

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Posted 04 March 2021 - 10:05 AM

Talk about a timely set of posts.  I too am struggling with Hyperstar backfocus.

 

After 10 years of limiting my imaging to astrometry I'm once again doing "aesthetic imaging."  Got a new ASI2600MC-P for use with a 2004 Meade 14" XL200GPS.  And resurrected my2007 Hyperstar M14 for wide field applications.  Been working on proper mounting and the backfocus issue since Jan 2nd and will fabricate a custom adapter as soon as the backfocus issue is addressed.

 

Starizona literature emphasizes that backfocus is critical to ±0.5mm.  And Scott at Starizona tells me that the M14 backfocus should be either 67.4mm or 70.5mm.  He also explained "If the spacing is wrong you get spherical aberration which shows up as what we call "space bubbles," sort of halos around bright stars.  Even though you can makes the stars small, they have these artifacts at best focus.

 

I've now run with both settings and don't know how to evaluate the results.  Focusing is weird as normal criterion such as brightest level or minimal FWHM don't work.  I get initial focus on a bright alignment star and then must perform a refined focus on a dim star within the target FOV, doing a visual adjustment at 400X.  At the 70.5 distance I've got a pinpoint star with a small halo filled with outburst rays.  At the 67.4 distance the star is about 2/3 the size of the 70.5mm halo but it's solid and has no halo. 

 

There are a lot of factors involved and it's difficult to provide accurate comparative images. Has anyone got any observations regarding which backfocus would be optimum?  At the moment I'm considering playing with some intermediate distance just to see if there's a happy medium.



#11 bhawks99

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Posted 04 March 2021 - 10:36 AM

All, I feel a bit foolish, it was the focus that was the issue. Once I got that straightened out everything worked fine. Thanks for helping a newbie!



#12 Peterson Engineering

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Posted 04 March 2021 - 10:55 AM

All, please don't close the topic yet as I'm stymied regarding Hyperstar backfocus optimization.



#13 Noah4x4

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Posted 05 March 2021 - 02:02 AM

As I said before, different cameras require different spacer rings with Hyperstar. These are supplied with Hyperstar and are not your usual multi-pack. Hence when you buy Hyperstar you need to state your specific camera. If you speak with Dean or Scott about you new camera, they will advise back-focus and spacer requirements.
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