44 replies to this topic

[rgsalinger]

So, I'm a cynic when it comes to reports and manufacturers' optical claims. I always ask for raw data that I can measure and eyeball. Until then, it's unclear what the optimal "next step" might be for the OP. 

 

As an example, I got a Pleiades WO68 for Xmas this year. They "claim" is that it has an "image circle" that allows the use of a full frame chip. That is, at least for my scope, utter nonsense. By getting down to adding/subtracting .1mm spacers, I'm getting decent results with a ZWO 2600, but there's no way it would ever cover a bigger chip with small pixels. 

 

This is consistent with my other refractor adventures. So, my advice is always to do the research before buying a bigger chipped camera. Don't pay attention to anyone who doesn't actually use what you are using. Astrobin is your best friend, imperfect though it might be. 

 

Incidentally, smaller pixels reveal all sorts of problems with the optics on most refractors. It's not just size that matters. On the other hand, you can fix up mediocre data with the use of modern processing tools. This image looked awful in the corners (it's uncropped) until I used an AI tool to fix it up. I bet it would be even better if the data was better in the first place, but I can't prove it. 

[Northrim]

I have the 294 and the 533 both MC pro.  Both are excellent cameras but I'd chose the 533 if I were you.  The flats are easier and there is no amp glow.  Just a newer more advanced sensor.

[vidrazor]

533 has double the sensor size for less than double the price. It's a no brainer.

Hmm, 2.9um vs 3.76um. I guess math wasn't your strong point in school.

Pixel size isn't everything. The 533 is a Starvis 1 design while the 585 is a Starvis 2 design. The 585's OE is 91% versus the 533's 80%, The 585's read noise is 0.8 vs 1.0 , and has 47 fps vs 20 for the 533 (which is over double if you do the math ).

So there are advantages and disadvantages to both. The 533 is 14bit vs 12 for the 585, and has a 50k full well vs 40 for the 585, but that's about it. What's not obvious is the thermal efficiency of the Starvis 2 design, which can run hotter and still have low noise. You can run a 585 without cooling and still get great subs. Add passive cooling, and you can shoot in a 104°F heat wave!

 

The ASIair is easily the smartest move they've ever made as a company. I'd bet they've made enough profit by now on other items (cams, EFW, EAF) to cover the R&D that it took to create it. Especially since basically half of what runs on it is open source software.

Like I said, heroin dealers. Yes ripped off Stellarmate/Astroberry.

Edited by vidrazor, 15 May 2024 - 05:21 PM.

[archiebald]

Focal length has nothing to do with whether it will vignette.

The only way to assess this is to go by what the mfg says is compatible, or based on reports from users with the same optics (including any reducers, flatteners, etc.) and an APS-C sensor.

Say what you will, but I am pretty sure that my 73mm aperture, 430mm, f/5.9 scope, (or 344mm f/4.7 at 0.8) is going to give an image circle that at least a very close approximation to the OP's scope at 72mm 430mm, f/6, (or 344, f/4.8 at 0.8).

 

And I see the OP has now confirmed that he has already been happily shooting with an APS-C sensor, so that sort of confirms my estimation.

[archiebald]

The ASIair is easily the smartest move they've ever made as a company. I'd bet they've made enough profit by now on other items (cams, EFW, EAF) to cover the R&D that it took to create it. Especially since basically half of what runs on it is open source software.

...Especially since basically it runs on illegally ripped off GNU license software.

[rgsalinger]

"happily shooting" is a meaningless statement for four reasons.

 

First of all, the pixel size matters. Smaller pixels reveal optical defects that larger pixels hide. The 600D's pixels are maybe 20 percent larger (IIRC).

 

Second, it's not a measurement, it's just a statement. What would make more sense would be to specify the aspect ratio or eccentricity of the stars.

 

Third, consider how the images are being displayed. For many people, all that they see is an image on a monitor that doesn't have have the full resolution of the camera. So, the image will look better than it actually is.

 

Finally, the spot diagrams tell the story of the optical quality (assuming that they are actually met in all production samples), not the focal length or the ration of focal length to objective diameter.  

 

Of course, I've certainly seen many people who show off images that I wouldn't. So, there's that as well. That's why I like to use astrobin where you have the ability to see a full resolution image. It's not as good as seeing raw data but if none is posted then it's probably the best you can do.

 

I would never recommend any test on youtube as useful unless I knew the person doing the test. Scammers and idiots abound on youtube.

Edited by rgsalinger, 15 May 2024 - 09:24 PM.

[Oort Cloud]

Hmm, 2.9um vs 3.76um. I guess math wasn't your strong point in school.

Pixel size isn't everything. The 533 is a Starvis 1 design while the 585 is a Starvis 2 design. The 585's OE is 91% versus the 533's 80%, The 585's read noise is 0.8 vs 1.0 , and has 47 fps vs 20 for the 533 (which is over double if you do the math ).

So there are advantages and disadvantages to both. The 533 is 14bit vs 12 for the 585, and has a 50k full well vs 40 for the 585, but that's about it. What's not obvious is the thermal efficiency of the Starvis 2 design, which can run hotter and still have low noise. You can run a 585 without cooling and still get great subs. Add passive cooling, and you can shoot in a 104°F heat wave!

Like I said, heroin dealers. Yes ripped off Stellarmate/Astroberry.

Nowhere does my post mention pixel size, so I guess reading comprehension wasn't your strong suit in school, now was it?

I am referring to SENSOR SIZE, which if you look at the specs, you'll see the 585 is the same width, and half the height, so half the area. But you'd need to be able to read to do that.

[archiebald]

"happily shooting" is a meaningless statement for four reasons.

 

First of all, the pixel size matters. Smaller pixels reveal optical defects that larger pixels hide. The 600D's pixels are maybe 20 percent larger (IIRC).

 

Second, it's not a measurement, it's just a statement. What would make more sense would be to specify the aspect ration or eccentricity of the stars.

 

Third, consider how the images are being displayed. For many people, all that they see is an image on a monitor that doesn't have have the full resolution of the camera. So, the image will look better than it actually is.

 

Finally, the spot diagrams tell the story of the optical quality (assuming that they are actually met in all production samples), not the focal length or the ration of focal length to objective diameter.  

 

Of course, I've certainly seen many people who show off images that I wouldn't. So, there's that as well. That's why I like to use astrobin where you have the ability to see a full resolution image. It's not as good as seeing raw data but if none is posted then it's probably the best you can do.

 

I would never recommend any test on youtube as useful unless I knew the person doing the test. Scammers and idiots abound on youtube.

I assume you are answering my point about "happily shooting"?

 

The question I was replying to was solely related to image circle and vignetting, which has zero to do with pixel size.  The 600D's APS-C sensor is the same physical size as an IMX571 (give or take a fraction), hence the ability to "happily" shoot without vignetting will be the same.

 

You seem to be referring to resolution, a whole different topic that I don't want to comment on.

Edited by archiebald, 15 May 2024 - 05:44 PM.

[idclimber]

Hmm, 2.9um vs 3.76um. I guess math wasn't your strong point in school.

Pixel size isn't everything. The 533 is a Starvis 1 design while the 585 is a Starvis 2 design. The 585's OE is 91% versus the 533's 80%, The 585's read noise is 0.8 vs 1.0 , and has 47 fps vs 20 for the 533 (which is over double if you do the math ).

So there are advantages and disadvantages to both. The 533 is 14bit vs 12 for the 585, and has a 50k full well vs 40 for the 585, but that's about it. What's not obvious is the thermal efficiency of the Starvis 2 design, which can run hotter and still have low noise. You can run a 585 without cooling and still get great subs. Add passive cooling, and you can shoot in a heat wave!

 

Like I said, heroin dealers. Yes ripped off Stellarmate/Astroberry.

You need to look at the ZWO graphs again. You do not get HCG mode on the 585 until gain 252 where the read noise is at 1 (not 0.7). Unfortunately with the gain that high the dynamic range is down to 11 stops. If you do not run the gain that high on that camera the read noise is higher than it is on 533 at either gain 0 or 100. You do no get read noise down to 0.7 unless you crank up the gain to 450, which is hardly useful for deep sky imaging. 

 

You also need to take a look at the dark noise current graphs and see which one is lower. Hint, it is not the 585. 

 

By far the single largest complaint against the IMX533 cameras for deep sky has been the relatively small sensor. This is especially true when comparing it to the 4/3 sized sensors like the ASI294 or the old ASI1600. There may be some specialized uses for a sensor half that size,  but it is NOT a better general purpose deep sky imaging camera for most beginners. 

[archiebald]

Hmm, 2.9um vs 3.76um. I guess math wasn't your strong point in school.

Pixel size isn't everything. The 533 is a Starvis 1 design while the 585 is a Starvis 2 design. The 585's OE is 91% versus the 533's 80%, The 585's read noise is 0.8 vs 1.0 , and has 47 fps vs 20 for the 533 (which is over double if you do the math ).

So there are advantages and disadvantages to both. The 533 is 14bit vs 12 for the 585, and has a 50k full well vs 40 for the 585, but that's about it. What's not obvious is the thermal efficiency of the Starvis 2 design, which can run hotter and still have low noise. You can run a 585 without cooling and still get great subs. Add passive cooling, and you can shoot in a 104°F heat wave!

 

Like I said, heroin dealers. Yes ripped off Stellarmate/Astroberry.

 

 

Nowhere does my post mention pixel size, so I guess reading comprehension wasn't your strong suit in school, now was it?

I am referring to SENSOR SIZE, which if you look at the specs, you'll see the 585 is the same width, and half the height, so half the area. But you'd need to be able to read to do that.

   

[vidrazor]

Nowhere does my post mention pixel size, so I guess reading comprehension wasn't your strong suit in school, now was it?
I am referring to SENSOR SIZE, which if you look at the specs, you'll see the 585 is the same width, and half the height, so half the area. But you'd need to be able to read to do that.

Actually yes, my mistake, apologies. Still, that size difference doesn't stop the 585 from getting the job done, so where's the advantage?
 

Edited by vidrazor, 15 May 2024 - 06:15 PM.

[rgsalinger]

@archiebald ----

 

FWIW "happily shooting" in this context means (to this native English speaker) that the images that are produced are of good to excellent quality and that therefore certain recommended changes will not affect perceived or measured image quality. There are more as well as idclimber and others have pointed out. 

 

None of my points (post 31) had was particularly aimed at resolution at all. That's another matter involving amongst other things the size of the objective and the size of the pixels and the seeing conditions. You might want to do some reading here if resolution interests you. For a more general treatment about how camera and optical characteristics affect image data quality, this book has some really nice explanations.

 

Where I was coming from in that post was that statements like the OP is "happy" do not allow one to accurately assess the current quality of the images in order to make data based recommendations. Look, we all have our standards relating to images that we really like. Some of those are artistic and some are suseptible to measurement. It's good to measure what we can and share those measurements to help people spend money wisely.

Edited by rgsalinger, 15 May 2024 - 09:41 PM.

[archiebald]

@archiebald ----

 

FWIW "happily shooting" in this context means (to this native English speaker) that the images that are produced are of good to excellent quality and that therefore certain recommended changes will not affect perceived or measured image quality. There are more as well as idclimber and others have pointed out. 

 

None of my points (post 31) had was particularly aimed at resolution at all. That's another matter involving amongst other things the size of the objective and the size of the pixels and the seeing conditions. You might want to do some reading here if resolution interests you. For a more general treatment about how camera and optical characteristics affect image data quality, this book has some really nice explanations.

 

Where I was coming from in that post was that statements like the OP is "happy" do not allow one to accurately assess the current quality of the images in order to make data based recommendations. Look, we all have our standards relating to images that we really like. Some of those are artistic and some are suseptible to measurement. It's good to measure what we can and share those measurements to help people spend money wisely.

 

 

Not sure why this conversation is continuing -  you seem to still have me confused with others that were talking about resolution.  Yes, I know all I need to know about it but the point being discussed, and which I commented on, was sensor size as it pertains to the image circle and vignetting with a particular OTA - not resolution or picture quality.
 

[Gatoberto]

I played with the telescope simulator on telescopius.com with the different cameras (585, 533, 294, 2600) to check framing of objects and FOV. I was also able to see the effect the different pixel sizes.

 

Of course, for galaxies, having a small sensor is no problem but for larger objects like M31, M42, I find the 585 too small and the 533 a bit tight, especially coming form an APS-C DSLR.  Between 294 and 2600, I think it makes more sense to spend extra and get the 2600.

 

I've been checking full-size images on Astrobin with all these and frankly to my untrained eye, they all look excellent.   

[archiebald]

I played with the telescope simulator on telescopius.com with the different cameras (585, 533, 294, 2600) to check framing of objects and FOV. I was also able to see the effect the different pixel sizes.

 

Of course, for galaxies, having a small sensor is no problem but for larger objects like M31, M42, I find the 585 too small and the 533 a bit tight, especially coming form an APS-C DSLR.  Between 294 and 2600, I think it makes more sense to spend extra and get the 2600.

 

I've been checking full-size images on Astrobin with all these and frankly to my untrained eye, they all look excellent.   

Regarding the point I made bold, I followed a very similar path to you with my Z73 and came to the same conclusion.  Coming from my DSLR, I didn't feel comfortable with the smaller sensor for most of the popular targets, so ended up with the IMX571 (as used in the asi2600).

 

Experience up to now has shown that 344 to 430mm FL + APS-C is a great combination for a wide range of DSO's

 

Such a relief when you can get through the selection process.  Of course, there is still the finance minister to overcome!!
 

[Tapio]

Luckily I also have 70-200mm f/2.8 lens so I can get 5 degree fov with 533 if I want to (and don't have to spent more money on bigger sensor and bigger filters).

[Oort Cloud]

Actually yes, my mistake, apologies. Still, that size difference doesn't stop the 585 from getting the job done, so where's the advantage?

It wasn't enough to be incorrect, you had to sling insults as well. You'll have to pardon me for not wanting to converse with you further.

[vidrazor]

It wasn't enough to be incorrect, you had to sling insults as well. You'll have to pardon me for not wanting to converse with you further.

Well, yes, my bad, and my apologies. Carry on.
 

[Gatoberto]

Luckily I also have 70-200mm f/2.8 lens so I can get 5 degree fov with 533 if I want to (and don't have to spent more money on bigger sensor and bigger filters).

I have the Canon 70-200mm f/2.8L IS USMII and it's a fantastic lens and my No. 1 choice for my professional photography.

 

An option that could save me some money would be using the ASI533 with this telephoto lens for larger objects and the 72EDII for smaller. However, I think a good quality telescope, which is optically designed for astronomy, would render far superior image results. 

Any thoughts on this? 

 

My biggest take away from all this discussions is that it's perhaps impossible to find a one-size-fits-all camera solution. I think most advanced astrophotographers have a few cameras that match different focal lengths and sky targets.

[idclimber]

I have the Canon 70-200mm f/2.8L IS USMII and it's a fantastic lens and my No. 1 choice for my professional photography.

 

An option that could save me some money would be using the ASI533 with this telephoto lens for larger objects and the 72EDII for smaller. However, I think a good quality telescope, which is optically designed for astronomy, would render far superior image results. 

Any thoughts on this? 

 

My biggest take away from all this discussions is that it's perhaps impossible to find a one-size-fits-all camera solution. I think most advanced astrophotographers have a few cameras that match different focal lengths and sky targets.

A lot of this is no different with full frame DSLR and lenses. My D850 and the Canon equivalents can show defects in many lenses, especially those that were made in the film or early full frame digital days. I also have a 70-200 f/2.8 but it is one model older than current. Nikon like Canon released newer better versions when they released better camera with smaller pixels. 

 

The 2600 is pretty hard to beat unless you have the budget and interest in full frame, which just like terrestrial world requires equally good glass.