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New F/4 focal reducer from Starizona

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#51 OleCuss

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Posted 29 May 2019 - 08:32 AM

Starizona specifies that this particular version does not work properly with EdgeHD or ACF Corrected SCTs (CSCTs).


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#52 Stargazer3236

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Posted 31 May 2019 - 08:32 AM

Has anyone bought this yet? Is this only good for sub 16mmm sensors?

 

I will be picking

  This up in a few weeks.


Edited by Stargazer3236, 31 May 2019 - 08:34 AM.


#53 OleCuss

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Posted 31 May 2019 - 08:58 AM

You should be able to use it with many sensors.  But there is a good chance that you could even have significant vignetting with a sensor with a diagonal measurement of less than 16mm (I've seen nothing to indicate how significant this is - or isn't).

 

With a diagonal measurement of the sensor greater than 16mm I would at least expect heavy vignetting.

 

But this may all be of little bother even with your ASI294.  If you are bothered by the heavy vignetting (esthetically or computationally) then you can simply define a smaller ROI and use a much smaller portion of your sensor to avoid that vignetting.

 

But if I might point out?  With a bigger sensor for which you are defining a smaller ROI, you can technically capture a much larger portion of the image circle.  You should be able to define a square of your sensor which is within the image circle or define a square which takes in the entirety of the image circle for a sort of porthole effect.

 

The sensor which is "too large" may really not be so much "too large" but a sensor which gives you more options.


Edited by OleCuss, 31 May 2019 - 08:59 AM.

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#54 HappySkies

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Posted 31 May 2019 - 03:14 PM

On the product page there are pictures taken with the 294 (23mm diagonal sensor) that are cropped down to a 16mm image circle. The reducer is corrected for 16mm, so anything outside of the 16mm image circle isn’t going to be realistically usable due to vignette or irregular star shape. 


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#55 OleCuss

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Posted 31 May 2019 - 09:47 PM

I'd note, however, that while there is an image taken using an IMX294 camera posted on their site, I'm curious as to how much vignetting was corrected for using calibration frames.

 

There are at least a few of us who are doing our OAP without calibration frames.  While I'm not actually recommending skipping the calibration frames, if you choose to do your observing that way then vignetting which is pretty acceptable when doing conventional AP might be quite unacceptable when doing OAP without calibration.

 

I'm hoping some of the early adopters of this Night Owl will post up some flats or at least some lights which are uncorrected with calibration.

 

Do note that I have a lot of hope for this item but I want to see more information before I consider the thing.



#56 Lorenz0x7BC

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Posted 08 June 2019 - 01:53 AM

The fine gentlemen from Starizona delivered the Night Owl by express courier, so I could test it yesterday when the clouds finally lifted (first light with the new reducer!).

Taking into account that I am a total EAA beginner, I am very pleased with the optical and overall quality of this product and the resulting images (way better than my previous attempts with DIY stacked reducers, perhaps others with more experience in this field would differ). In my opinion well worth the higher cost.

I don't have any flats, but the image below has only a master dark applied (to overcome hot pixels and amp glow), so perhaps it can serve as passable field test.

Stack_15frames_60s_WithDisplayStretch.jpg
M27
15x4s (60s total), 350 gain, RAW16
(Evo8 Alt-Az ASI 224MC @F4)

Interestingly when running this image through astrometry.net it gives me F4.1 as focal ratio, although I had the spacing exactly like in the instructions stated: 26mm t-thread spacer plus 12.5mm asi224 backfocus (38.5mm in total), the reducer inserted as far down as possible inside the 2" visual back...

Edited by Lorenz0x7BC, 08 June 2019 - 04:18 AM.

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#57 einarin

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Posted 08 June 2019 - 07:18 AM

Looks good.

Now if only someone could test with a bigger chip...



#58 cshine

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Posted 12 June 2019 - 05:56 PM

Looks good.

Now if only someone could test with a bigger chip...

Curiosity was killing me too so I have ordered one and plan on testing with the C11 / 294 combination.. will post some results here .. including uncropped full sensor images


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#59 roelb

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Posted 12 June 2019 - 07:24 PM

The fine gentlemen from Starizona delivered the Night Owl by express courier, so I could test it yesterday when the clouds finally lifted (first light with the new reducer!).

Taking into account that I am a total EAA beginner, I am very pleased with the optical and overall quality of this product and the resulting images (way better than my previous attempts with DIY stacked reducers, perhaps others with more experience in this field would differ). In my opinion well worth the higher cost.

I don't have any flats, but the image below has only a master dark applied (to overcome hot pixels and amp glow), so perhaps it can serve as passable field test.

attachicon.gif Stack_15frames_60s_WithDisplayStretch.jpg
M27
15x4s (60s total), 350 gain, RAW16
(Evo8 Alt-Az ASI 224MC @F4)

Interestingly when running this image through astrometry.net it gives me F4.1 as focal ratio, although I had the spacing exactly like in the instructions stated: 26mm t-thread spacer plus 12.5mm asi224 backfocus (38.5mm in total), the reducer inserted as far down as possible inside the 2" visual back...

see: http://www.wilmslowa...rmulae.htm#FR_b

<Moving mirror SCTs require special treatment because their focal length changes (lengthens) as you adjust focus to compensate for the in-focus required from inserting the focal reducer in the optical path.>


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#60 Lorenz0x7BC

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Posted 12 June 2019 - 11:34 PM

see: http://www.wilmslowa...rmulae.htm#FR_b
<Moving mirror SCTs require special treatment because their focal length changes (lengthens) as you adjust focus to compensate for the in-focus required from inserting the focal reducer in the optical path.>


That must be it! Thanks for clarifying why my measurement was off, Roel.

#61 HappySkies

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Posted 19 June 2019 - 04:10 PM

I was doing some testing with my new L-eNhance filter using the night owl reducer over the full moon. I figured I'd post a single image from what I got. Single 60s image. No flats, darks, or bias frames. Just debayer, white balance, and auto histogram stretch in PI. My collimation was out a little bit but I didn't have a good screw driver handy to do anything about it. No guiding because I have a friend borrowing my guider. I was probably pushing my luck with the exposure times. I think that's it. Let me know if I missed something.

 

Equipment

  • C8
  • AXV
  • ZWO ASI183MC Pro
  • Optolong L-eNhance Filter
  • AstroZap bahtinov mask
  • PoleMaster
  • Coffee

 

Link to original fits file: https://drive.google...N-L5nF743N/view

 

Larger jpg image: https://drive.google...nIBYzVMmwO/view

 

 

 

Attached Thumbnails

  • nightowl-enhance_crescent-60s.jpg

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#62 DonBoy

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Posted 19 June 2019 - 04:32 PM

Thanks for the post.  I notice distinct vignetting and wondering if anything in the optical chain is causing this or if it is due to illumination falloff of the image circle.  The stars look good to the edge and that part seems to be working with the 183 camera with it's 16mm diagonal sensor.   I suspect that if the Night Owl was made in a larger size 2.5" to 3" that one would see less illumination vignetting.


Edited by DonBoy, 19 June 2019 - 04:47 PM.


#63 Owk

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Posted 20 June 2019 - 04:19 AM

I’m very intrigued by this reducer. I currently use the standard Meade 0.67 with a asi 294. On a c925.

 

will the best use case for me be to use the night owl with a ROI on the 294. The 183 seems to be the perfect sensor size (16mm) but with such small pixels, will that negate the benefit of the f4 in terms of light collection.

 

hope that’s not a silly question

 

hemi



#64 OleCuss

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Posted 20 June 2019 - 05:15 AM

I’m very intrigued by this reducer. I currently use the standard Meade 0.67 with a asi 294. On a c925.

 

will the best use case for me be to use the night owl with a ROI on the 294. The 183 seems to be the perfect sensor size (16mm) but with such small pixels, will that negate the benefit of the f4 in terms of light collection.

 

hope that’s not a silly question

 

hemi

It's not a silly question.

 

The answer should be more complex than what I will give, but suffice to say that (as I'm sure you know) for a low-noise (and quite good QE) sensor like the IMX294 or the IMX183 the Night Owl doesn't really convey all that much benefit in rapidly acquiring an image with good SNR.  I think Starizona would disagree with me but I will certainly disagree with them.  The Night Owl does not increase the number of photons presented to your sensor and with a low-noise sensor there is very little benefit from read-noise reduction with faster optics.

 

There is nothing particularly wrong with using the ASI294 with the Night Owl.  You could define that smaller ROI and pretty much fit that small image circle.  The problem is that if used with a standard 8" SCT the Night Owl gives you an effective focal length of 800mm and you will be under-sampled.  You will not be terribly under-sampled so that really may not bother you but you will have decreased resolution as a result.

 

The advantage of using an IMX183 camera with a standard 8" SCT is that you will not be under-sampled.  This means you will not have the camera choice reducing the potential resolution of the system.  The smaller pixels will mean, however, that your dynamic range will be much worse than with that wonderful IMX294 camera.

 

OK, so your dynamic range is going to be much less.  What that will mean to you is not all that clear to me.

 

The ASI294's greater well-depth and its 14-bit ADC means you can do a better job of imaging both a dim target and a bright target without blowing out (sort of over-saturating) the bright target.  This is very nice and is especially important if you are doing CAP (Conventional AP) of a FOV with both bright and dim targets - and you are doing very long exposures (as you know, they like 5+ minutes).

 

But we are doing OAP (Observational AP) and we are usually doing short subs and stacking a whole bunch of them.  So when using a nice sensor like the IMX183 which doesn't have a lot of dynamic range what we do is just ensure that our sub-exposures are short enough so that we don't blow out the bright things in our FOV and do a whole lot of those sub-exposures.  Doing a lot of subs means you eventually capture a lot of signal from the dimmer target and thus get pretty good SNR for them along with the brighter target - effectively the greater number of subs gives you back much of the dynamic range which you lost by using a sensor with less dynamic range.

 

Anyway, I've got to cut this shorter as their are other things I must be doing.  But the upshot is that if you use the ASI294 with the Night Owl 0.4x corrector on a standard 8" SCT you will be under-sampled but have the option of using somewhat longer subs.  With the ASI183 you'll not be under-sampled but you'll likely need to consider using shorter subs and taking more of them.

 

One other potential benefit to using the IMX183 camera is that you can get a monochrome version.  That monochrome version has higher QE (around 80% peak QE) for better SNR - but I think most of us would opt for the OSC version and that means your QE will be around 70% and that is a little worse than what the ASI294 will be giving you.

 

Well, I hope that helps a bit.


Edited by OleCuss, 20 June 2019 - 08:06 AM.


#65 DonBoy

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Posted 20 June 2019 - 10:44 AM

Is the IMX294 really undersampled for 800mm FL @ 1.19 arcsec/pixel?   And isn't the IMX183 oversampled at 0.62 arcsec/pixel and wouldn't it be a better match if binned 2x2 and thus yield an image scale of 1.24 arcsec/pixel?



#66 OleCuss

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Posted 20 June 2019 - 11:58 AM

Is the IMX294 really undersampled for 800mm FL @ 1.19 arcsec/pixel?   And isn't the IMX183 oversampled at 0.62 arcsec/pixel and wouldn't it be a better match if binned 2x2 and thus yield an image scale of 1.24 arcsec/pixel?

It does sort of depend on your perspective.

 

I tend to operate on the assumption that the seeing will be about 2 arc-seconds.  I think that this is a reasonable assumption for most folk most of the time.  Conventional wisdom would then suggest aiming for an APP in the range of 0.67-1.0.

 

If one accepts that assumption, the ASI294 will be under-sampled but not terribly.  The IMX183 would be over-sampled, but not terribly - and since the IMX183 is a low-noise sensor there will be almost no SNR penalty from the over-sampling.

 

Tonight's forecast in my small city is for "seeing" of about 1.6-1.7 arc-seconds.  Let's go with 1.65?  This would mean that my target APP is in the 0.55-0.83 range.  So for me tonight if the forecast is correct and if I had the time and had that 0.4X reducer attached to one of my 8" SCTs the ASI183 would not be over-sampled at all and the over-sampling by the ASI294 would be a bit worse than with my baseline/typical assumption.

 

But depending on your target, how you are viewing, and what your viewing goals might be, the over- and under-sampling issues may matter a lot or not at all.

 

The flip side of the argument is that with the ASI294 you have a reasonable fit between the sensor size and the image circle I'd expect to get with the typical 0.63x reducer.  So one could argue for getting the much cheaper 0.63x reducer/corrector and you might get a roughly equivalent view?  Of course, by my 2 arc-second seeing assumption you'd then be over-sampled with the ASI294 but it wouldn't matter much since it is a low-noise sensor.

 

As it turns out, I have a mono ASI183 so I'd be happy to try out the 0.4x reducer.  I'd not be missing too much of the FOV and still be getting good detail - and with a camera which has what appears to be a pretty darned good SNR.  But if I didn't have the ASI183 and did have the ASI294 I'd likely be very happy to try doing OAP with either the 0.63x or the .04x reducer.


Edited by OleCuss, 20 June 2019 - 12:00 PM.


#67 DonBoy

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Posted 20 June 2019 - 12:24 PM

One can use this tool to determine what each camera type will provide under the varying seeing conditions for 800mm FL.

 

Here are two examples for OK Seeing:

 

Screen Shot 2019-06-20 at 1.10.05 PM.jpg

 

Screen Shot 2019-06-20 at 1.18.58 PM.jpg


Edited by DonBoy, 20 June 2019 - 12:27 PM.

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#68 cshine

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Posted 21 June 2019 - 06:13 AM

Conditions here were bad this week but I managed a quick test of the Night Owl with the C11 / ZWO294 combination. Transparency was so bad that I couldn't test the light gathering improvement, so this is purely an indication of the vignetting I found on the large sensor.

 

The setup was:

 

C11 3.28" rear port -- JMI EV Crayford focuser -- 2inch CLS filter -- Night Owl -- 21mm spacer -- 11mm collar -- 294

 

The Crayford allows the Night Owl to get quite close to the rear port although I didn't measure the exact distance. Given the size of the rear port this should not cause any vignetting as far I can tell.

 

Here's M3 on the full sensor (no ROI crop):

 

Vignetting.JPG

 

m3.JPG

 

.. and M51 on a 2072x1410 ROI crop:

 

M51-cropped.JPG

 

I think that would be the crop to use, with flats it should be OK. I stretched these in such a way as to emphasize the vignetting. Obviously no flats used here.

 

Astrometry put the image scale at 0.842 arcsec/pixel which is about the right number for F/4 and a good sampling point for OK conditions.

 

AT.JPG

 

Happy to do other tests if anyone wants me to try something else.

 

 

 


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#69 DonBoy

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Posted 21 June 2019 - 11:39 AM

Based on your M3 image at full resolution with the 294, which has a 23mm sensor diagonal.  It looks like the fully illuminated  image circle for the Night Owl is 9mm diameter.   And ROI of the 294 at 2072x1410 would yield a sensor diagonal of 11.6mm.  


Edited by DonBoy, 21 June 2019 - 11:44 AM.

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#70 bdyer22

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Posted 22 June 2019 - 04:40 PM

Just tried out the Night Owl w/ ASI 290.  Via Astrometry.net the reduction produced f4.16.  Think the spacing was off a little.

 

There might be some coma at the edges, but that could be spacing again.  Not an expert here, I think the spacing at f4 is more critical than what I usually do.  I'm happy with it.  Just got to figure out how to get it to work with the filter wheel.  Not much backspace there. smile.gif

 

FYI.  I spoke with Starizona and they said that if you use a filter wheel you need to add 1mm to backspace.  Edit:  this only applies if the filter is behind the Night Owl.

 

Astrometry:  http://nova.astromet...99119#annotated

M57 Astometry

 

Original

Stack 69frames 276s


Edited by bdyer22, 22 June 2019 - 04:43 PM.

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#71 aiken999

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Posted 30 June 2019 - 04:18 PM

Saquaro

Where did you get the 2 inch 25mm spacer?

Mike



#72 Lorenz0x7BC

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Posted 01 July 2019 - 09:17 AM

Saquaro

Where did you get the 2 inch 25mm spacer?

Mike

A T-thread 25mm spacer can be found here:

https://www.ebay.com...T-/183292408912



#73 saguaro

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Posted 01 July 2019 - 10:24 AM

Saquaro

Where did you get the 2 inch 25mm spacer?

Mike

Even though the reducer is a 2-inch format (designed to slip into a 2-inch visual back), the camera-side threads are standard T-threads (M42): https://starizona.co...ducer-corrector

 

So all you need is a 25mm T-thread spacer like the one Lorenz0x7BC linked to.



#74 Stargazer3236

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Posted 16 July 2019 - 09:38 AM

It's not a silly question.

 

The answer should be more complex than what I will give, but suffice to say that (as I'm sure you know) for a low-noise (and quite good QE) sensor like the IMX294 or the IMX183 the Night Owl doesn't really convey all that much benefit in rapidly acquiring an image with good SNR.  I think Starizona would disagree with me but I will certainly disagree with them.  The Night Owl does not increase the number of photons presented to your sensor and with a low-noise sensor there is very little benefit from read-noise reduction with faster optics.

 

There is nothing particularly wrong with using the ASI294 with the Night Owl.  You could define that smaller ROI and pretty much fit that small image circle.  The problem is that if used with a standard 8" SCT the Night Owl gives you an effective focal length of 800mm and you will be under-sampled.  You will not be terribly under-sampled so that really may not bother you but you will have decreased resolution as a result.

 

The advantage of using an IMX183 camera with a standard 8" SCT is that you will not be under-sampled.  This means you will not have the camera choice reducing the potential resolution of the system.  The smaller pixels will mean, however, that your dynamic range will be much worse than with that wonderful IMX294 camera.

 

OK, so your dynamic range is going to be much less.  What that will mean to you is not all that clear to me.

 

The ASI294's greater well-depth and its 14-bit ADC means you can do a better job of imaging both a dim target and a bright target without blowing out (sort of over-saturating) the bright target.  This is very nice and is especially important if you are doing CAP (Conventional AP) of a FOV with both bright and dim targets - and you are doing very long exposures (as you know, they like 5+ minutes).

 

But we are doing OAP (Observational AP) and we are usually doing short subs and stacking a whole bunch of them.  So when using a nice sensor like the IMX183 which doesn't have a lot of dynamic range what we do is just ensure that our sub-exposures are short enough so that we don't blow out the bright things in our FOV and do a whole lot of those sub-exposures.  Doing a lot of subs means you eventually capture a lot of signal from the dimmer target and thus get pretty good SNR for them along with the brighter target - effectively the greater number of subs gives you back much of the dynamic range which you lost by using a sensor with less dynamic range.

 

Anyway, I've got to cut this shorter as their are other things I must be doing.  But the upshot is that if you use the ASI294 with the Night Owl 0.4x corrector on a standard 8" SCT you will be under-sampled but have the option of using somewhat longer subs.  With the ASI183 you'll not be under-sampled but you'll likely need to consider using shorter subs and taking more of them.

 

One other potential benefit to using the IMX183 camera is that you can get a monochrome version.  That monochrome version has higher QE (around 80% peak QE) for better SNR - but I think most of us would opt for the OSC version and that means your QE will be around 70% and that is a little worse than what the ASI294 will be giving you.

 

Well, I hope that helps a bit.

I have decided to buy the 183MM after selling my 290MM last night. I also will buy the Night Owl 0.4 reducer corrector as well, but will get the camera first. I have read a lot about the Night Owl and 183MM as well. I already own the 294MC camera too.


Edited by Stargazer3236, 16 July 2019 - 09:39 AM.

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