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

astrophotography
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#26 WadeH237

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Posted 17 August 2019 - 08:46 AM

And while I've never used an OAG, what little I know would suggest that if you use a smaller ROI for the ASI1600?  I'd think you could still use the OAG.

The position of the pick-off on an OAG is a physical thing that is in front of the sensor.  Changing the ROI will not affect the light that reaches it.

 

Based on everything that I've read here, this is a solution for a small sensor, one shot color camera.  For most people, I maintain that the Celestron F7 reducer is a much better option.

 

That said, I am waiting until Starizona releases this before I reach my final conclusion.  It's possible that I'm not understanding something correctly.



#27 Astrojedi

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Posted 17 August 2019 - 09:49 AM

In my experience OAGs don’t work very well at such fast focal ratios due to the steeper light cone.

 

I really don’t think this reducer is targeted at imaging with 4/3rd sensor size or larger.


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#28 OleCuss

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Posted 17 August 2019 - 09:59 AM

The position of the pick-off on an OAG is a physical thing that is in front of the sensor.  Changing the ROI will not affect the light that reaches it.

 

Based on everything that I've read here, this is a solution for a small sensor, one shot color camera.  For most people, I maintain that the Celestron F7 reducer is a much better option.

 

That said, I am waiting until Starizona releases this before I reach my final conclusion.  It's possible that I'm not understanding something correctly.

I'd happily agree that effective use of the OAG with the Night Owl/ASI1600 combo would mean that the pick-off would be in front of the sensor.  But if you have chosen a Region Of Interest about the same size as that of the ASI183, then if the pick-off is not all that large then this should not be a problem.

 

But I'd really pay attention to Astrojedi's suggestion that the OAGs don't work well with the steeper light-cone you will have with the Night Owl.  This would not be different whether using the ASI1600 with a small ROI or the ASI183.



#29 OleCuss

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Posted 17 August 2019 - 10:21 AM

.

.

.

I really don’t think this reducer is targeted at imaging with 4/3rd sensor size or larger.

I'd happily agree with this.

 

However, if I had an ASI1600 already and also had a nice SCT and the Night Owl, I'd actually expect the combination to work fairly well if one defined a smaller ROI and kept the sub-exposures rather short.

 

My biggest concern with that combination is that lots of aperture (which we tend to have with some of our SCTs) along with light concentrated into a small image circle along with the lack of anti-reflection coating in the MN34230 sensor which the ASI1600 uses - could result in bothersome reflection problems.

 

Some day I might try the combination with my C11 and I'm betting that modestly long sub-exposures on only modestly bright stars will give me the halo/reflection problem.  It might be hard to justify trying that when I actually do have the ASI183. . .



#30 WadeH237

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Posted 17 August 2019 - 10:37 AM

But I'd really pay attention to Astrojedi's suggestion that the OAGs don't work well with the steeper light-cone you will have with the Night Owl.  This would not be different whether using the ASI1600 with a small ROI or the ASI183.

I use my OAG with my refractor in an F/4.8 configuration, and this is not a problem.  It does change the shape of the stars, but the guiding software can deal with this fine.

 

But seriously, by the time you throw out a signficant portion of your sensor, and make a mechanical adjustment to the OAG so that it doesn't work on other scopes with an appropriately sized image circle, you would have been much better off just getting the Celestron F/7 reducer (or get a different camera with a smaller sensor).  Yes, your integration time will be longer, but I would much prefer longer integration time with well matched components, than hacking stuff together that don't work well that way.

 

Keep in mind, that this whole part of the conversation revolves around making existing equipment work in a new configuration.  By its nature, that suggests that you already have a functioning imaging system.  I would suggest that in that case, this reducer might not be the best choice (even if it could be kludged to work).

 

If you are starting from scratch, or are building a new system, then there is a definite attraction to an F/4 scope with 200mm of aperture.  There would be two rather unusual limitations, though.  The first is that you have a much shorter than typical back focus, which limits camera selection.  And second, you would expect such a system to be a wide field instrument, but the small imaging circle would put constraints on the size of that field.  Again, you would want a camera matched to this.



#31 WadeH237

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Posted 17 August 2019 - 10:40 AM

My biggest concern with that combination is that lots of aperture (which we tend to have with some of our SCTs) along with light concentrated into a small image circle along with the lack of anti-reflection coating in the MN34230 sensor which the ASI1600 uses - could result in bothersome reflection problems.

This artifact is always present.

 

It becomes visible when you stretch enough to see it.  This happens easily with bright stars, but it's dim enough with smaller stars that it's below the noise floor.  The thing is, that once you collect enough data to present the dim areas well, it will be there.  It doesn't matter if you get that data through big aperture, or through longer exposures.

 

If you have that sensor, it's just a fact of life, regardless of optics.



#32 Astrojedi

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Posted 17 August 2019 - 10:56 AM

While they are always present, the sensor diffraction artifacts are only obvious on very bright stars. Also keep in mind that the brightness of the star is only dependent on the aperture as it is a point source and independent of the f ratio. So that is not a consideration here.



#33 WadeH237

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Posted 17 August 2019 - 11:27 AM

Also keep in mind that the brightness of the star is only dependent on the aperture as it is a point source and independent of the f ratio. So that is not a consideration here.

The brightness of the star does not matter.  What matters is whether you stretch it enough to see the artifacts.  And whether you can do this or not is dependent on the SNR of the area around the star.  You can reach that SNR with time on target, or with aperture.  The effect is the same.

 

Seriously.  I get that artifact with big and small aperture, and with fast and slow focal ratio.  It is actually pretty dim, which is why you only see it around bright stars in the images we typically take.  I've not tried, but I suppose that if you picked a dim star, and then collected hours and hours of data on it, you could see it around dim stars, too.

 

Anyway, my point is that you will get this artifact with an 8" at F/4, just as you will with an 8" at F/7 or F/10.  You can get it with a smaller scope, too.

 

But it's really off topic from this thread, so if we want to continue this angle, we should start a new thread.



#34 Churmey

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Posted 17 August 2019 - 12:36 PM

Test 2 : 08/16/19

NGC7380 under 99% full moon and redzone

EdgeHD 8", Starizona Night Owl HD Prototype, ASI183MC-C, L-Enhance filter

90 - 120s subs, Unity Gain @ -10C

 

Note: This prototype has 3D printed plastic internal components. I am expecting to receive a better calibrated, machined version, later this week.

 

 

32bit stack, and single original .fit file, can be downloaded here for review :

 

https://1drv.ms/u/s!...LUT7EQ?e=7N8K2R

 

 

Great discussion around the usability of this reducer. I do want to point out that, per the first sentence of this thread, this reducer is designed for sensors up to a 16mm diagonal.  If you use a larger sensor, you will need to crop to a 16mm diagonal. It's that simple. It will not be a significant crop for the 1600/294, or any MFT type sensor, but for a APS-C or Full Frame sensor, the Celestron F7 will more than likely be a better fit. Again, it's a perfect match for the 183.  Look at it like this.....as an example, with a full frame sensor attached to a EdgeHD 8, your focal length is 2032mm.  Even with a Full Frame sensor attached to the EdgeHD 8, there are some areas around the edges that are not correctable with flats. It's slight, very slight, but it's there. With a Full Frame sensor, and F7 reducer, there is a significant amount of non correctable area. I've found the maximum usable space is just over the APS-C coverage area, when the F7 reducer is used.  My point is this.....the F4 Night Owl HD extends the image circle, for a 16mm diagnal sensor, almost to that of the native coverage area that is equal to a  Full frame sensor at F10.  I estimate the FOV being roughly 2400mm FL equivalent - so although not all the way to the native 2032, it's very close.  This is why I'm so interested in the F4 Night Owl HD -  it gets you back to a very usable scale / FOV when using an excellent, economical cooled sensor, such as the 183 or MFT sensors.  Lastly, due to the 35mm (with filter) backfocus limitation, along with the steep light angle, I doubt a OAG is possible.  However, at the F4 scale, the good news is that a guidescope now is possible.

 

NGC7380 STARIZONA NIGHT OWL TEST 2 CN Gallery
 
AB Link:
 
get.jpg?insecure

Edited by Churmey, 17 August 2019 - 12:41 PM.

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#35 Astrojedi

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Posted 17 August 2019 - 02:18 PM

Excellent result. Looking good.


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#36 dmdouglass

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Posted 17 August 2019 - 04:48 PM

Now, with this image (NGC 7380 above), i can relate somewhat to what is happening.

I have this target, captured using an Edge 8", with a standard SBig4x3 large area chip, which seems to be a reference used in this discussion.

 

Granted, not the SBig, but the ASi1600 is a 4x3 chip to, so a good "look".

I have the ASI183, and i know the "normal" FOV when used with the Edge.

The result above is impressive. Especially, when compared to my SBig image..

 

.

NGC-7380-OC-20161009-C.jpg

 

I grabbed  a copy of the OP's image, and ran it through Astrometry.net.  Measures 51x34 ArcMin.

My Big (4x3) image measures 32x24.  So the reducer is working, and definately giving "big chip" performance to the 183 camera. Important here that the OP says the target camera here is the 183.  

 

Anyway...  impressive.


Edited by dmdouglass, 17 August 2019 - 04:48 PM.

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#37 Jeffmar

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Posted 17 August 2019 - 07:44 PM

I am very interested in this focal reducer but it makes sense it wouldn't work quite as well for a larger sensor. Even at f/10 my full frame cameras get vignetting. With .7 focal reducer it is worse. The up side to using my full frame cameras is significantly lower noise at higher ISO's. I have been experimenting with ISO's of 6400 and a bit higher and it does as well as some other cameras I have had at 1600 ISO. So if I get vignetting I just have to keep to target in the center. I don't have any dedicated astronomy cameras so I am not sure if there is a big difference, but maybe the .4 reducer is worth the keyhole effect larger sensors bring. 



#38 Ladyhawke

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Posted 18 August 2019 - 04:35 AM

Maybe I am not understanding the discussion around this reducer and a large sensor. What do you mean by large sensor, a full frame? I am using an ASI 1600 with a Hyperstar and filter wheel at F/2 and I get some vignetting but it is totally correctable with flats so why would that be an issue at F/4? The image below was taken using the Hyperstar configuration mentioned above, the only cropping done was to remove the misaligned edges due to dithering. So I assume this would work just well with the Night Owl?

 

get.jpg?insecure

 



#39 WadeH237

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Posted 18 August 2019 - 06:26 AM

Hyperstar is a different beast altogether, because it's at the primary mirror's focal plane.

 

Anything that you mount on the back of the scope is going to be constrained by having to pass through the baffle tube.


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#40 Churmey

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Posted 18 August 2019 - 08:56 AM

Maybe I am not understanding the discussion around this reducer and a large sensor. What do you mean by large sensor, a full frame? I am using an ASI 1600 with a Hyperstar and filter wheel at F/2 and I get some vignetting but it is totally correctable with flats so why would that be an issue at F/4? The image below was taken using the Hyperstar configuration mentioned above, the only cropping done was to remove the misaligned edges due to dithering. So I assume this would work just well with the Night Owl?

 

 

Hi Ladyhawke. Unlike the Hyperstar's front mounted design, the Night Owl HD is a back mounted reducer.  It will give you a F4 FOV within a 16mm (1") diagonal sensor. When you think about it, it requires a 16mm diagonal sensor to reduce it to F4 from the back (see above comment as it relates to this) as it almost gets you back to a full frame (36mm sensor) equivalent FOV at F10 (example: A Canon 6D attached to a EdgeHD without a reducer.....or in other words, the black 36mm FOV shown below crammed into the green 1" area FOV shown below). Anything larger would extend the image circle beyond the capabilities of the Edge's native coverage area. Here is a visual  representation of the corrected area, and the sensor size, that the Night Owl HD F4 reducer is designed for. You can see that, If a 4/3 sensor is used, such as the 1600/294, it will need to be cropped down to the area of the 1" sensor (such as the 183) area shown. The green circle represents the Edge image circle with the Night Owl HD F4.  I don't consider this a large crop, but some may.

Attached Thumbnails

  • SENSOR SIZE - C.jpg

Edited by Churmey, 18 August 2019 - 09:00 AM.


#41 Churmey

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Posted 18 August 2019 - 09:14 AM

Test 3 : 08/17/19

NGC7822 under 96% moon and redzone

EdgeHD 8", Starizona Night Owl HD Prototype, ASI183MC-C, Optolong L-Enhance filter

100 - 120s subs (3 hrs total), Gain 270 @ -10C

 

Note: This prototype has 3D printed plastic internal components. I am expecting to receive a better calibrated, machined version, later this week

 

32bit stack, and single original .fit file, can be downloaded here for review :

 

https://1drv.ms/u/s!...oK2BEg?e=BTskYL

 

AB Link:

 

get.jpg?insecure

 

 

Test 4 : 08/17/19

NGC6946 under 96% moon and redzone
EdgeHD 8", Starizona Night Owl HD Prototype, ASI183MC-C, Optolong L-Pro

45- 120s (1.5 hrs total) subs, Gain 111 @ -10C

 

32bit stack, and single original .fit file, can be downloaded here for review :

 

https://1drv.ms/u/s!...uFv4cQ?e=8aFwcD

 

AB Link:

 

get.jpg?insecure

 

 

I took the liberty to apply an aggressive stretch to these test sessions, as the 96% moon sky conditions weren't that great. Be sure to download and view the original edits and / or apply a more moderate stretch.


Edited by Churmey, 18 August 2019 - 10:57 AM.

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#42 OleCuss

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Posted 18 August 2019 - 09:30 AM

Nice work indeed!

 

I'm looking forward to seeing what the system can do with the style more typical on this forum (short exposures with relatively high gain and rather short total integration time).  But then, we've seen good work with the non-HD version so I'm betting OAP will be very nice with the HD version.


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#43 Stargazer3236

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Posted 18 August 2019 - 10:54 AM

Test 3 : 08/17/19

NGC7822 under 96% moon and redzone

EdgeHD 8", Starizona Night Owl HD Prototype, ASI183MC-C, Optolong L-Enhance filter

100 - 120s subs (3 hrs total), Gain 270 @ -10C

 

Note: This prototype has 3D printed plastic internal components. I am expecting to receive a better calibrated, machined version, later this week

 

32bit stack, and single original .fit file, can be downloaded here for review :

 

https://1drv.ms/u/s!...oK2BEg?e=BTskYL

 

AB Link:

 

get.jpg?insecure

 

 

Test 4 : 08/17/19

NGC9646 under 96% moon and redzone
EdgeHD 8", Starizona Night Owl HD Prototype, ASI183MC-C, Optolong L-Pro

45- 120s (1.5 hrs total) subs, Gain 111 @ -10C

 

32bit stack, and single original .fit file, can be downloaded here for review :

 

https://1drv.ms/u/s!...uFv4cQ?e=8aFwcD

 

AB Link:

 

get.jpg?insecure

 

 

I took the liberty to apply an aggressive stretch to these test sessions, as the 96% moon sky conditions weren't that great. Be sure to download and view the original edits and / or apply a more moderate stretch.

That should be 6946, instead of 9646.


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#44 Churmey

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Posted 18 August 2019 - 11:00 AM

That should be 6946, instead of 9646.

Thank you Stargazer for pointing that out. I had it named incorrectly in SGP and carried that error all the way through. I corrected it above but I'll have to keep the onedrive links/file names as an error....too much work to correct it there smile.gif


Edited by Churmey, 18 August 2019 - 11:03 AM.


#45 Astrojedi

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Posted 19 August 2019 - 12:20 PM

The brightness of the star does not matter.  What matters is whether you stretch it enough to see the artifacts.  And whether you can do this or not is dependent on the SNR of the area around the star.  You can reach that SNR with time on target, or with aperture.  The effect is the same.

 

Seriously.  I get that artifact with big and small aperture, and with fast and slow focal ratio.  It is actually pretty dim, which is why you only see it around bright stars in the images we typically take.  I've not tried, but I suppose that if you picked a dim star, and then collected hours and hours of data on it, you could see it around dim stars, too.

 

Anyway, my point is that you will get this artifact with an 8" at F/4, just as you will with an 8" at F/7 or F/10.  You can get it with a smaller scope, too.

 

But it's really off topic from this thread, so if we want to continue this angle, we should start a new thread.

Please read my post. This is not what I am saying. While the diffraction is present all the time the brightness of the star makes the artifacts more noticeable. Also this effect is independent of focal ratio as the brightness of a star depends solely on aperture. There are actually many stars which will not produce a noticeable pattern in say a 60mm but will produce it in a 11". Sure it will always be there and if you stretch aggressively enough you will see it (you will see a lot of other stuff as well) but I am talking about seeing these artifacts in the final post processed image.



#46 Astrojedi

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Posted 19 August 2019 - 12:23 PM

Test 3 : 08/17/19

NGC7822 under 96% moon and redzone

EdgeHD 8", Starizona Night Owl HD Prototype, ASI183MC-C, Optolong L-Enhance filter

100 - 120s subs (3 hrs total), Gain 270 @ -10C

 

Note: This prototype has 3D printed plastic internal components. I am expecting to receive a better calibrated, machined version, later this week

 

32bit stack, and single original .fit file, can be downloaded here for review :

 

https://1drv.ms/u/s!...oK2BEg?e=BTskYL

 

AB Link:

 

get.jpg?insecure

 

 

Test 4 : 08/17/19

NGC6946 under 96% moon and redzone
EdgeHD 8", Starizona Night Owl HD Prototype, ASI183MC-C, Optolong L-Pro

45- 120s (1.5 hrs total) subs, Gain 111 @ -10C

 

32bit stack, and single original .fit file, can be downloaded here for review :

 

https://1drv.ms/u/s!...uFv4cQ?e=8aFwcD

 

AB Link:

 

get.jpg?insecure

 

 

I took the liberty to apply an aggressive stretch to these test sessions, as the 96% moon sky conditions weren't that great. Be sure to download and view the original edits and / or apply a more moderate stretch.

 

Thanks. These look very good. How much vignetting are you seeing with this reducer and the ASI183? Can you provide a flat frame if possible. 



#47 Churmey

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Posted 19 August 2019 - 02:09 PM

Thanks. These look very good. How much vignetting are you seeing with this reducer and the ASI183? Can you provide a flat frame if possible. 

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

Attached Thumbnails

  • MasterFlat.jpg

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#48 Benni123456

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Posted 19 August 2019 - 04:01 PM

Hi churmey, can you test this reducer with an asi 183 mm-c?

 

The asi 183 has an 1'' sensor and 20.18 megapixels.

 

With that one should see what the reducer is capable of...

 

Interesting would then be how star shapes look for different filters at the edges.

 

It is interesting that this f4 reducer now can deliver round stars at the edges.

 

If they can make an f7 reducer which can guarantee round stars for full frame or at least aps-c when a camera with high megapixel count is used, it would be interesting.

 

Because the Celestron f7 reducer has problems with this. The Celestron f7 reducer for the edge 8 produces comet shaped stars at the edges which look different at different colors. In my case, green is round, blue and red not.


Edited by Benni123456, 19 August 2019 - 04:04 PM.


#49 Churmey

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Posted 19 August 2019 - 04:30 PM

Benni123456  "Hi churmey, can you test this reducer with an asi 183 mm-c?"

 

All of the test 1-4 images, posted here, were all shot with the ASI183. You can see further tech details on the provided Astrobin links. In addition, you can download original stacks and original single files from the provided links, for review.

 

As for the Celstron F7 Edge8 reducer - I personally, along with many others, have had great results with it. I would suggest that you make sure your back focus is accurate. It should be 105mm from reducer flange to sensor. Otherwise, you will indeed see the effects of improper flange to sensor spacing. 


Edited by Churmey, 19 August 2019 - 04:32 PM.

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#50 Benni123456

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Posted 19 August 2019 - 07:46 PM

Hi, i asked for the monochrome camera. 

 

In the monochrome camera, you cam see exactly whether the star shapes are the same for every color.

 

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.

 

if one makes these images with the monochrome camera, one immediately sees that the starshape is a bit different for each color.....

 

these things can not really be seen in a color camera but the monochrome version shows this crisp and clear.


Edited by Benni123456, 19 August 2019 - 07:47 PM.



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