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New F/4 focal reducer from Starizona

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#1 saguaro

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Posted 27 February 2019 - 01:15 PM

Starizona is just about to release an F/4 focal reducer. It is a 2-inch format, with female 2-inch filter threads on the telescope side and male T-threads on the camera side. Price will be $279. To use it, you need a 2-inch visual back that has standard female SCT threads. For example, I've been using this one: https://agenaastro.c...-2-adapter.html

 

The Starizona F/4 focal reducer is designed for use with camera sensors up to 16mm diagonal or less, which means cameras like the ASI183 and smaller sensors. It will be possible to use it with a larger sensor like the 294 (23mm diagonal) and use region of interest (ROI) in SharpCap to crop the image down a bit and still get good results.

 

I've been doing some informal testing with a borrowed prototype with my classic (40-yr old) Celestron 8-inch SCT on an Evolution Alt-Az mount. Using my ASI385MC (which has a slightly larger sensor than the 224-based cameras), the results exceed the quality of what I am able to get with my "used" Meade 3.3 reducer. Stars are sharper (more pinpoint) with the Starizona F/4 reducer when used at its recommended spacing from the camera sensor. Even when used with 5mm more spacing than recommended to increase the focal reduction to F/3.9 (which is possible if using a smaller sensor), the edge of field curvature is no worse than with the Meade 3.3 reducer and stars are still sharper across the rest of the field than when using the Meade 3.3 reducer. While the Meade 3.3 reducer is only for 1/3-inch format sensors or smaller, the Starizona F/4 reducer will work well with sensors up to 16mm diagonal which makes it more versatile.

 

Here are some test images, all taken with my classic 8-inch SCT on an Evolution Alt-Az mount, with SharpCap live stacking and master dark. No filters used.

 

M81 22x15sec Meade 3.3 reducer @F/3.8

M81 22x15sec Meade F3.8.jpg


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#2 saguaro

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Posted 27 February 2019 - 01:19 PM

M81, 32x10sec under full moon, Starizona F/4 reducer at recommended spacing

 

M81-32x10sec-Starizona F4.2.jpg

 

M81, 20x15sec, Starizona reducer with 5mm more spacing for F/3.9 (so this would be most similar to the M81 image with the Meade reducer@F/3.8 that I posted above)

 

M81-20x15sec-Starizona F3.9.jpg


Edited by saguaro, 27 February 2019 - 01:20 PM.

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#3 saguaro

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Posted 27 February 2019 - 01:23 PM

Running Man, 31x15sec, Meade 3.3 reducer @F3.8

 

Running-Man-31x15sec-Meade-F3.8.jpg

 

Running Man, 30x10sec under full moon, Starizona F/4 reducer at recommended spacing

 

Running-Man-30x10sec-Starizona F4.2.jpg



#4 saguaro

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Posted 27 February 2019 - 01:26 PM

Running Man, 20x15sec, Starizona reducer with 5mm more spacing for F/3.9 (so this would be most similar to the Running Man image with the Meade reducer@F/3.8 that I posted above)

 

Running-Man-20x15sec Starizona F3.9.jpg


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#5 makeitso

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Posted 27 February 2019 - 01:43 PM

seguraro,

 

1. What is the time frame for this to come out?

 

2. Can I use it with a 1 1/4” filter attached to my asi224?

 

3. What is the spacing?

 

If you answered these questions, I missed it. I have the right 2” visual back. I know I could use a 2” filter but 1 1/4” is better compatibility with my stuff.

 

Thanks, Jack



#6 Kaikul

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Posted 27 February 2019 - 02:08 PM

This is a nice addition to my wish list. Thank you for taking the initiative to do the tests, and posting your results.


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#7 alphatripleplus

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Posted 27 February 2019 - 02:17 PM

 

 

The Starizona F/4 focal reducer is designed for use with camera sensors up to 16mm diagonal or less, which means cameras like the ASI183 and smaller sensors. It will be possible to use it with a larger sensor like the 294 (23mm diagonal) and use region of interest (ROI) in SharpCap to crop the image down a bit and still get good results.

 

I've been doing some informal testing with a borrowed prototype with my classic (40-yr old) Celestron 8-inch SCT on an Evolution Alt-Az mount. Using my ASI385MC (which has a slightly larger sensor than the 224-based cameras), the results exceed the quality of what I am able to get with my "used" Meade 3.3 reducer. Stars are sharper (more pinpoint) with the Starizona F/4 reducer when used at its recommended spacing from the camera sensor. Even when used with 5mm more spacing than recommended to increase the focal reduction to F/3.9 (which is possible if using a smaller sensor), the edge of field curvature is no worse than with the Meade 3.3 reducer and stars are still sharper across the rest of the field than when using the Meade 3.3 reducer. While the Meade 3.3 reducer is only for 1/3-inch format sensors or smaller, the Starizona F/4 reducer will work well with sensors up to 16mm diagonal which makes it more versatile.

 

 

Robin,

 

In your pics with the Starizona reducer working at f/4, I still notice some aberrations in the corners of the 8.3mm diagonal  ASI385 sensor. I would imagine that with a larger sensor, like the 16mm diagonal ASI183, those aberrations are going to be even more noticeable and over a larger part of the sensor. Have you had a  chance to try the Starizona reducer with a 16mm sensor, like the 385, to see what it looks like? I'm just a little skeptical about their claim that it is "designed for use with camera sensors up to 16mm".

 

I would agree that for a 1/2 inch sensor, like the ASI385, it looks (fairly) good. 



#8 einarin

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Posted 27 February 2019 - 02:17 PM

Hm, I'm seeing some elongation even with recommended distance and such small sensor.

Need more examples.



#9 petert913

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Posted 27 February 2019 - 02:27 PM

F/10 down to F/4 ?  Very nice !



#10 saguaro

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Posted 27 February 2019 - 02:29 PM

seguraro,

 

1. What is the time frame for this to come out?

 

2. Can I use it with a 1 1/4” filter attached to my asi224?

 

3. What is the spacing?

 

If you answered these questions, I missed it. I have the right 2” visual back. I know I could use a 2” filter but 1 1/4” is better compatibility with my stuff.

 

Thanks, Jack

Hi Jack,

 

I don't know the date for when the F/4 reducer will be available, but it should be fairly soon. Best to contact Starizona for availability.

 

Yes, you can use a 1.25-inch filter. You will need the ZWO T2-1.25" Filter Adapter: https://agenaastro.c...-t2-1-25-3.html

 

The recommended spacing from the rear of the reducer to the camera sensor is 38.5mm. The ASI 224 has a "focus distance to sensor" of 12.5mm. So you will need to add 26mm using T-spacers. I used a 25mm T-spacer and that was close enough.

 

ZWO uncooled.jpg


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#11 saguaro

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Posted 27 February 2019 - 02:35 PM

I don't have a sensor that's close to the 16mm max. recommended size to try out. Hopefully Starizona will be publishing some images taken with larger sensors when they add the F/4 reducer to their website.

 

My tests represent just one set of sample images, using a 40-year old classic SCT. So images taken with more modern SCTs and Edge SCTs should be no worse, and may actually be better.



#12 saguaro

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Posted 27 February 2019 - 10:01 PM

The F/4 reducer I’m testing isn’t designed for use with the Edge SCTs after all. There will be an Edge version available as well.
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#13 OleCuss

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Posted 28 February 2019 - 10:17 AM

The F/4 reducer I’m testing isn’t designed for use with the Edge SCTs after all. There will be an Edge version available as well.

That is really good to know.

 

I've more than one uncorrected SCT - an F/4 with 16mm usable image circle sounds very interesting!



#14 einarin

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Posted 28 February 2019 - 10:42 AM

38.5mm backfocus is on the short side.



#15 saguaro

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Posted 28 February 2019 - 11:11 AM

38.5mm backfocus is on the short side.

That depends on how you intend to use the focal reducer in your imaging train and whether you use an Alt-Az or Equatorial mount. For my use on an Evolution Alt-Az mount, the backfocus distance is short enough to allow me to clear the base of my mount when using an un-cooled camera. Even when I added an extra 5mm of spacing to increase the focal reduction, all I had to do was move my OTA forward a little bit and I can still clear the base of my Evolution mount.

 

While using a filter wheel may not be possible, I can still easily use a filter if I want to. To use a 1.25-inch filter, I can use the ZWO T2-to-1.25-inch filter adapter which puts the filter very close to the sensor and doesn't add much if any back-focus distance. To use a 2-inch filter, I can screw it on to the front of the F/4 reducer.



#16 descott12

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Posted 28 February 2019 - 01:25 PM

Hi Robin,

Your images comparing f3.9 and f4 for the new Starizona FR are so dramatically different. The f3.9 are much better. Are you saying that a difference of only 0.1 had that much effect? Or is there something else going on?   All other variables were the same (seeing, background light pollution, etc...)??



#17 saguaro

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Posted 28 February 2019 - 01:33 PM

Hi Robin,

Your images comparing f3.9 and f4 for the new Starizona FR are so dramatically different. The f3.9 are much better. Are you saying that a difference of only 0.1 had that much effect? Or is there something else going on?   All other variables were the same (seeing, background light pollution, etc...)??

The F/4 images were taken under a full moon so that’s why they look so different. Our weather was terrible so I took the first clear night I could get despite the full moon. The other images were taken with no moon to interfere.


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#18 descott12

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Posted 28 February 2019 - 01:38 PM

Ah. That makes sense. Thanks. I wonder how  f/4 or f/3.9 compares to f/2 with HyperStar. There would probably be a significant difference there.



#19 saguaro

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Posted 28 February 2019 - 02:19 PM

Ah. That makes sense. Thanks. I wonder how  f/4 or f/3.9 compares to f/2 with HyperStar. There would probably be a significant difference there.

The major differences are image scale and imaging circle. For example, I participate in outreach events with a fellow who uses his classic C-8 with a Hyperstar and a Mallincam DS10c (Sony IMX 294 sensor). The Hyperstar 8 can illuminate a much larger imaging circle (28mm) and has an effective focal length of about 400mm. He gets great wide field views of M31 (the entire galaxy plus room to spare), M42 and Running Man together, Horsehead and Flame together, M81 and M82 together (you get the idea) with similar short exposures. With my classic C8 and the F/4 reducer (or the Meade 3.3 reducer operating at F/3.8), I have a much smaller illuminated area and much smaller field of view at around 775mm effective focal length. I wouldn't be able to use a 294-size sensor without cropping the edges of the image to remove the elongated stars at the outer edges of the images. But, I really like the image scale for most objects like galaxies, the Crab Nebula, the Horsehead, etc.  You learn to pick the targets that look best with the setup you are using, and each setup has its pluses and minuses. For example, at the last outreach event, we had lots of wind which made my live stacking efforts impossible. However, the fellow with the Hyperstar setup was not as effected due to the much shorter focal length he was using.


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#20 tmaestro

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Posted 28 February 2019 - 02:38 PM

Imaging aside, it will be lovely to pick this up and a used SCT and have 6 or 8 inches of flat field at f/4 for just sweeping around the Milky Way for well under $1000.


Edited by tmaestro, 28 February 2019 - 02:38 PM.


#21 saguaro

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Posted 28 February 2019 - 02:56 PM

Imaging aside, it will be lovely to pick this up and a used SCT and have 6 or 8 inches of flat field at f/4 for just sweeping around the Milky Way for well under $1000.

I don’t know if this reducer can be used for visual use. Good question to ask Starizona.


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#22 calypsob

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Posted 01 March 2019 - 02:31 PM

Starizona is just about to release an F/4 focal reducer. It is a 2-inch format, with female 2-inch filter threads on the telescope side and male T-threads on the camera side. Price will be $279. To use it, you need a 2-inch visual back that has standard female SCT threads. For example, I've been using this one: https://agenaastro.c...-2-adapter.html

 

The Starizona F/4 focal reducer is designed for use with camera sensors up to 16mm diagonal or less, which means cameras like the ASI183 and smaller sensors. It will be possible to use it with a larger sensor like the 294 (23mm diagonal) and use region of interest (ROI) in SharpCap to crop the image down a bit and still get good results.

 

I've been doing some informal testing with a borrowed prototype with my classic (40-yr old) Celestron 8-inch SCT on an Evolution Alt-Az mount. Using my ASI385MC (which has a slightly larger sensor than the 224-based cameras), the results exceed the quality of what I am able to get with my "used" Meade 3.3 reducer. Stars are sharper (more pinpoint) with the Starizona F/4 reducer when used at its recommended spacing from the camera sensor. Even when used with 5mm more spacing than recommended to increase the focal reduction to F/3.9 (which is possible if using a smaller sensor), the edge of field curvature is no worse than with the Meade 3.3 reducer and stars are still sharper across the rest of the field than when using the Meade 3.3 reducer. While the Meade 3.3 reducer is only for 1/3-inch format sensors or smaller, the Starizona F/4 reducer will work well with sensors up to 16mm diagonal which makes it more versatile.

 

Here are some test images, all taken with my classic 8-inch SCT on an Evolution Alt-Az mount, with SharpCap live stacking and master dark. No filters used.

 

M81 22x15sec Meade 3.3 reducer @F/3.8

attachicon.gif M81 22x15sec Meade F3.8.jpg

is this for edge scopes or any sct?  NM just saw your post about the edge


Edited by calypsob, 01 March 2019 - 02:41 PM.


#23 saguaro

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Posted 01 March 2019 - 02:50 PM

is this for edge scopes or any sct?  NM just saw your post about the edge

There will be two versions; one for Edge SCTs and Meade ACF F/10 scopes and one for non-Edge SCTs and non-ACF Meade SCTs. They told me that Meade F/8 ACF SCTs will not work well with this reducer.



#24 dvb

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Posted 02 March 2019 - 08:34 PM

Thanks for the heads up on this.  It will make the Edge 8  a very powerful imaging platform.



#25 Stargazer3236

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Posted 04 March 2019 - 12:10 AM

I might be interested in this when it comes out.




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