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Starizona “Night Owl” for EdgeHD SCT’s : Prototype initial test

astrophotography
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#51 Churmey

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Posted 19 August 2019 - 09:39 PM


 

For example if you look at your images with the f7 reducer and look at stars on the edges, you clearly see that some sides have a thad different colors than other sides.

 

I do not have any published images using a F7 reducer. 

 

As for my 183 mono, I typically only use it for Lum and/or HA data. I do not use it for RGB work. 



#52 Benni123456

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Posted 20 August 2019 - 04:36 AM

Oh sorry, i somehow clicked on the wrong link and mistook an image from someone else with an image of yours.



#53 OleCuss

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Posted 20 August 2019 - 05:06 AM

Here is what my MasterFlat (low quality for CN upload) looks like:

That actually looks better than I expected!


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#54 Sarkikos

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Posted 22 August 2019 - 07:15 AM

Would the Starizona "Night Owl" reducer have any advantage for visual astronomy?  I already have the Celestron 0.7x Reducer, which brings the EdgeHD 8" down to f/7 with 105mm back focus.  The Starizona would reduce down to f/4 with 34mm back focus.

 

Mike



#55 OleCuss

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Posted 23 August 2019 - 04:54 AM

Would the Starizona "Night Owl" reducer have any advantage for visual astronomy?  I already have the Celestron 0.7x Reducer, which brings the EdgeHD 8" down to f/7 with 105mm back focus.  The Starizona would reduce down to f/4 with 34mm back focus.

 

Mike

I'm really not sure but I think it would depend on the eyepiece and your preference.

 

If your eyepiece's field stop is larger than the image circle provided by your 0.7x reducer then I don't think you would find that your FOV would be improved by using the 0.4x reducer.  If your image circle is larger than is the field stop of that eyepiece, then if you can get things in focus I'd expect the 0.4x reducer to increase your FOV.

 

I don't think there is any significant benefit for which one could hope other than a bigger FOV.  You might get some correction of the "coma" but it may not be enough to change your viewing pleasure.

 

So while I think you might like it, I'd point out that Starizona doesn't market it for use with an eyepiece.  It was really designed for AP.



#56 Sarkikos

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Posted 23 August 2019 - 05:54 AM

The EdgeHD 8" is already corrected for coma.  The only benefit from the Starizona f/4 reducer would be the wider field.

 

A possible bottleneck is the clear aperture of the rear port.  IIRC, this is 42mm.  

 

Mike



#57 WadeH237

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Posted 23 August 2019 - 07:06 AM

Would the Starizona "Night Owl" reducer have any advantage for visual astronomy?  I already have the Celestron 0.7x Reducer, which brings the EdgeHD 8" down to f/7 with 105mm back focus.  The Starizona would reduce down to f/4 with 34mm back focus.

 

Mike

There is a limit to the width of the field that an SCT can provide.

 

A while ago, I exchanged email with Dean at Starizona regarding their large format SCT corrector for visual use with my C14.  He was adamant that it was not appropriate for visual use.  In particular, with a wide field eyepiece, it would make the shadow of the secondary mirror visible.  He must have felt pretty strongly about it, because when I told him that I was also considering it for imaging and asked a few more questions, he never responded.

 

I will note that I have used a Celestron F/6.3 reducer corrector with my C14 and a Panoptic 41.  It clearly shows both of the issues that he was describing.  I have to imagine that an F/4 reducer would make all of this even more obvious.

 

My thoughts on this for visual is that you might get some benefit from the correction, but for increasing the field of view, you are better off at the telescope's native focal length with a long focal length eyepiece.

 

If you really want an F/4 visual instrument, my suggestion would be to look at a Newt.



#58 Sarkikos

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Posted 23 August 2019 - 07:26 AM

Again, there would be no benefit for correction in an EdgeHD 8", because it already contains a lens assembly which corrects for coma and flattens the field.  That's why it's called an "EdgeHD." 

 

The Celestron 0.7 Reducer especially designed for the EdgeHD 8" works fine for visual.  If the Starizona f/4 Reducer for the EdgeHD 8" provides no advantage for visual use, I have no use for it.  YMMV

 

I have an 8"  f/3.9 Newt.  I took a chance on it because it was advertised for AP, and I'm visual only.  It was on sale. :shrug:  It works for visual, but I have to put an extension tube in the focuser for eyepieces to come to focus.  Lesson learned:  avoid instruments and accessories designed for AP, if you don't do AP.

 

Mike


Edited by Sarkikos, 23 August 2019 - 07:30 AM.


#59 Astrojedi

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Posted 23 August 2019 - 09:35 AM

Would the Starizona "Night Owl" reducer have any advantage for visual astronomy?  I already have the Celestron 0.7x Reducer, which brings the EdgeHD 8" down to f/7 with 105mm back focus.  The Starizona would reduce down to f/4 with 34mm back focus.

 

Mike

I doubt that it will work for visual. These reducers are designed for imaging. Given the short backfocus you will need a diagonal with an extremely short light path (like the redcat diagonal). Even then the correction will likely vary a bit by EP as the precise distance will be harder to maintain vs the 0.7x reducer or at native F10. I generally don’t use any reducers with the EdgeHD 8 as I can achieve the maximum possible field using the 30mm 82deg but it is a heavy and bulky EP.


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#60 Sarkikos

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Posted 23 August 2019 - 12:04 PM

Here is a list of eyepieces for the EdgeHD 8", with and without 0.7x reducer:

 

Mike

Attached Files



#61 Sarkikos

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Posted 23 August 2019 - 12:05 PM

EdgeHD 8" eyepiece list with and without 0.7x reducer

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  • EdgeHD 800 Eyepiece List.jpg

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#62 bwayne

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Posted 25 August 2019 - 08:27 PM

.... I am using a C5 as a guidescope so I have greatly minimized my drift ....



Hi, very interesting stuff! Could you please share how you’ve mounted this combination and what are the approximate weights? What is your guide camera? Thanks! Brett

#63 mclewis1

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Posted 26 August 2019 - 07:38 AM

Using a small SCT as a guidescope gives you lots of focal length in a small light package but if you are also imaging at long focal lengths an SCT guidescope can sometimes introduce small errors from mirror flop that can be really difficult to troubleshoot.



#64 bwayne

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Posted 26 August 2019 - 11:51 AM

Using a small SCT as a guidescope gives you lots of focal length in a small light package but if you are also imaging at long focal lengths an SCT guidescope can sometimes introduce small errors from mirror flop that can be really difficult to troubleshoot.


Thanks. Yes his imagery clearly exhibits floppiness, that’s precisely what I want to emulate -:)

#65 Churmey

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Posted 26 August 2019 - 01:34 PM

Hi, very interesting stuff! Could you please share how you’ve mounted this combination and what are the approximate weights? What is your guide camera? Thanks! Brett

I estimate total wight on the DEC to be approx 30lbs. As you can see, I set some threads and attached a ADM V saddle directly to a ADM V bar designed for the EdgeHD8.  Naked, the C5 weighs approx 6 lbs. Dressed out as shown, probably closer to 9-10lbs.  I'm using another ASI183 as a guide camera.  I'm experimenting with the guide system, so hopefully will be able to make improvements as I go.

Attached Thumbnails

  • C5-ON-EDGE8.jpg


#66 Astrojedi

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Posted 26 August 2019 - 02:56 PM

Given that most guiding programs can achieve centroid detection accuracy of 1/10 - 1/15 of a pixel you don’t really need such a long focal length guidescope. 

 

Assuming the primary imaging camera and the guide camera have the same pixel size a 100mm FL guidescope is sufficient for the EdgeHD 8 @ F4.

 

The larger and heavier the guidescope more the opportunity for differential flexure. The C5 also introduces mirror flop into the equation. 

 

Nevertheless this is is a unique setup. I don’t think I have seen a C5 used as a guidescope on the EdgeHD 8.



#67 Churmey

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Posted 26 August 2019 - 03:20 PM

Given that most guiding programs can achieve centroid detection accuracy of 1/10 - 1/15 of a pixel you don’t really need such a long focal length guidescope. 

 

Assuming the primary imaging camera and the guide camera have the same pixel size a 100mm FL guidescope is sufficient for the EdgeHD 8 @ F4.

 

The larger and heavier the guidescope more the opportunity for differential flexure. The C5 also introduces mirror flop into the equation. 

 

Nevertheless this is is a unique setup. I don’t think I have seen a C5 used as a guidescope on the EdgeHD 8.

Thanks Astrojedi. This is an area that I'm unsure of, as I've always used a OAG.  I have a rigid 400mm/F5.6 lens that I've adapted to be a guidescope. It's only about 4.5 lbs total (with rings / camera attached).  I may give it a try. To be honest, I have never been able to totally eliminate drift with using a guidescope. The C5 did seem to improve it a little but, there were some that remained.  When I use a OAG, I have no drift.



#68 bwayne

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Posted 26 August 2019 - 03:25 PM

I estimate total wight on the DEC to be approx 30lbs. As you can see, I set some threads and attached a ADM V saddle directly to a ADM V bar designed for the EdgeHD8. Naked, the C5 weighs approx 6 lbs. Dressed out as shown, probably closer to 9-10lbs. I'm using another ASI183 as a guide camera. I'm experimenting with the guide system, so hopefully will be able to make improvements as I go.


Thanks for sharing. This would be a really versatile setup to leverage my C5 with. Since it’s always present it reduces travel load. Looking forward to more updates!

#69 Astrojedi

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Posted 26 August 2019 - 03:35 PM

Thanks Astrojedi. This is an area that I'm unsure of, as I've always used a OAG.  I have a rigid 400mm/F5.6 lens that I've adapted to be a guidescope. It's only about 4.5 lbs total (with rings / camera attached).  I may give it a try. To be honest, I have never been able to totally eliminate drift with using a guidescope. The C5 did seem to improve it a little but, there were some that remained.  When I use a OAG, I have no drift.

If you are getting drift it is unlikely due to the focal length of the guider. More likely due to differential flexure or mirror flop. Make sure you lock down the primary mirror on the EdgeHD 8.

 

Here is a guided 120s exposure with my EdgeHD 8 @ F7. This was with the 183 x2 binned which gives a sampling of 0.70”. The guidescope used was the ZWO miniguider (120mm FL) and guide camera was ASI120 mono.

 

The mount was the RST-135 which has pretty high periodic error so needs to be very tightly guided. I focused and locked down the primary mirror.

 

A7069AEC-FE0A-4F56-81E0-D5371E579B69.jpeg


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