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Current best Solar Imaging camera?


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Hello,

     I have been away from imaging for a very long (2016) time after a hip replacement and need to relearn my hobby as I still consider myself to be an uneducated amateur.  Several months ago I setup to image and to my horror realized as I was slewing the Sun into view of the scope I had forgotten to install my Daystar Quark Ha filter on my Explore Scientific 80mm triplet scope and I THINK I may have damaged my ZWO ASI 174MM camera but I have not tried to use it since my discovery.  I have a ASI 290MM cooled that I bought awhile back (In the hopes of achieving a bit more magnification/zooming in on solar details as I could not afford a larger tripletthen or now) but I have never used yet.

   
    Is there a new king of the hill solar imaging camera or should I replace my possibly damaged ASI 174MM (I am not sure how to check it for damage) with a new ASI 174MM cooled camera? Or will the unused ASI 290MM cooled be good enough? I prefer closeups of surface features and proms to full disk imaging and hope to afford a larger perhaps 127-130mm refractor (for detailed close up shots) in the future anything bigger I feel would be wasted for solar or deep sky in my seeing conditions.

     
    I also have a 80mm single stacked Lunt Ha scope that I rarely use because for some reason my 80mm triplet with Daystar Quark Ha “seems” to give better images. But I also can not afford to double stack the Lunt... if it even can be.

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I also have the ASI 174mm and an ASI 1600MM which I use for solar imaging.

I find the plate scale (0.7 arcsec/ pixel) with the ASI 1600 suits my SM60/ ED80 set-up.

It works well for me.

(The larger chip allows full disk imaging)

 

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I'm only an enthusiastic onlooker, but from the forums and things,   the 174 mono chip is the one people tend to prefer for detailed imaging at the moment.

There is a lot of info out there on preferred and recommended pixel size for the set up you are going to use, taking into account use of barlows etc...

USB 3.0  and global shutter are also preferred options (if perhaps your older model  needs upgrading).  Also, having a fast drive (SSD) on your PC also helps with the data transfer.

Companies like Basler and Point Grey ( now FLI )  use the same chip in their cams, sometimes with slightly enhanced performance.

 

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I paired the asi 174mm with a 400+GB ssd drive but thinking I will install a 1TB NVMe drive in lap top just for image captures once I upgrade to the latest laptop with fastest most cores cpu I can afford.I will find out soon if there was any damage to the camera, Saturday is supposed to be cloud free. So Friday night I will try and remember how to do a polar alignment.

Edited by AstroEd
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highest frame rate possible (usb3), for the focal length you will be using most.   You want to image with critical sampling ratio without a barlow for practical purposes.   (but for high resolution you definitly want a powermate 2x minimum)

use the formula here to determin.   http://www.wilmslowastro.com/software/formulae.htm#CCD_Sampling

 

 

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If I did this right... based on 80mm scope and the Quark wavelength I think is 656nm and the ASI 174mm camera pixel size is 5.86 microns.... but to be honest I do not have the knowledge of what  needs to be done to read the calculations numbers.

F3EB04FB-8DFB-4E3F-AD5A-85AE1994A261.jpeg

Edited by AstroEd
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Doesn’t the above information mean since my scope is 480mm focal length at f/6 the results = 3.660417 times the native focal length so I need to use a  3.5-4.0x Barlow for optimal focal length for the camera?

 

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Ed,

Sounds about right...

If you use the Quark, with the built-in x4 barlow on an ED80 at f7.5 (=f30) you are over sampling, but if your conditions are good, get maximum resolution.

If you use a 80mm f6 scope then you need as you say a 3.5 - 4x barlow for "maximum resolution"

The local seeing may limit you.......

 

Edited by Merlin66
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10 minutes ago, Merlin66 said:

Ed,

Sounds about right...

If you use the Quark, with the built-in x4 barlow on an ED80 at f7.5 (=f30) you are over sampling, but if your conditions are good, get maximum resolution.

If you use a 80mm f6 scope then you need as you say a 3.5 - 4x barlow for "maximum resolution"

The local seeing may limit you.......

 

Oh the Quark is already barlowed so I do not need to use my power mate? Also if I use the ASI290MM will the built in Barlow mess up the imaging as according to the calculation it should be about 2x?

A side note: I own a 2.5 and 4x powermate Barlow.

Edited by AstroEd
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Ed, yes, no powermate needed with the Quark.

The ASI 290 has very small pixels 2.9 micron, not an ideal solution for the Quark. This camera would be best around in a system f12 to f15.

 

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As Ken intimates above. I use both the 174 and 290 for solar and lunar imaging.  I useD a Lunt 60 and a 2.5x powermate which is almost perfect for the 290. The 290 chip is widescreen format which works well on the Moon. For the Sun I tend to crop it down to get the capture rate up. I find the 174 slightly easier to manage when it comes to processing the frames although it is slightly under sampling. I now have a Lunt 80 which is even better with the 290. Some examples in the link below.

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Sounds like I wasted my Money on the ASI290MM (cooled), sadly At this time it is all moot as I had to order a replacement power supply for the iOptron CEM60 mount and won’t be able to try and image this weekend after all. I do have a Meade ETX125 (f/15)that I bought on clearance that might be ok for the ASI290MM, sadly the model had a defective mount (the knob for the center shaft screw never could go up far enough to place tension on the leg support tray) So I have owned it for almost 9 years and never really got to use it and misplaced its power supply also. So since I could not use it I sent the Hand controller to another astronomer who needed it. I always hoped I could modify it to be mountable on my CEM60 mount but never got around to trying.
 

So if I were to start from scratch and buy all new PROPER equipment for High resolution Solar imaging suitable for average or less sky conditions what should I buy? I never managed to learn how to properly adjust my 80mm Lunts pressure, I might have to sell it for as close to full price as possible to pay for proper equipment as it has not been used since I got my Daystar quark Ha. Though the focuser has been upgraded to a moonlight focused for automated focusing.

Edited by AstroEd
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12 hours ago, AstroEd said:

This is the calculation for the ASI290MM cooled camera pixel size. I am sorry for being confused, I really am trying to learn, I am just stupid at times.

First of all - that calculation is not quite correct. It is very close to what it should be, but wrong assumptions were used - like that x3 being x3 for Nyquist criteria - like it is somehow "better" than x2 that Nyquist criteria says or even explanation that I've heard - well this is 2d case so one ought to use x3 instead of x2.

Anyway, proper F/ratio for pixel size is 0.8133... times that value (we can go into details but it's 2.44 instead of 3).

You want F/8.85 to be properly sampling.

Now, your scope is 480mm F/6 and Quark has x4.2 telecentric lens - this means that effective F/ratio is F/25.2.

If you use ASI290 regularly, you will be oversampling by large amount. However, not all is lost. Since you have F/25.2 system, let's see if we can do something about it.

What would happen if you used camera with x3 larger pixel size instead of ASI290 native pixel size? Well, you would need 3 x F/8.85 = F/26.55 system for optimum sampling rate. That is very close to F/25.2 that you already have so you would be very close to optimum solution.

How on earth would you get x3 pixel size on such camera? Well - there is simple solution, bin your pixels 3x3 in software. There you go, almost optimum sampling rate.

But hold on, there must be some sort of catch? ASI174 is certainly better with its large pixel size?

There is a catch, but let's see how much it matters. When doing software binning, camera will have higher read noise. In case of 3x3 bin, read noise will increase x3.

ASI290 has read noise of ~1e at high gain (and you should be using it), so overall after x3 bin it will have pixel equivalent of 8.7um and read noise of ~3e.

ASI174 on the other hand has 5.86um pixel size and read noise ~3.5e.

ASI290 will have larger pixel / better matched to F/25.2 of your system and lower read noise. You only need to bin it x3 in software.

If you want to go with bigger scope - do this math again on a bigger scope and see what is suitable combination. In fact, I think that for bigger scope, you don't really want regular Quark - you want Quark combo as with it you can use your own telecentric lens and aperture masks to get needed F/ratio - both for proper sampling rate and also for best filter operation.

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Vlaiv,

Eversberg and Vollmann "Spectroscopic Instrumentation", pages 72 - 83 discuss at some great length the "optimum" sampling rate.

Definitely not the Nyquist x2.

They conclude by recommending around 3 to adequately sample.

The chip size of the ASI 290 is small 5.6 x 3.2 mm

28 minutes ago, vlaiv said:

Well - there is simple solution, bin your pixels 3x3 in software

Which AVI processing software would you recommend/ suggest?

 

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3 minutes ago, Merlin66 said:

Vlaiv,

Eversberg and Vollmann "Spectroscopic Instrumentation", pages 72 - 83 discuss at some great length the "optimum" sampling rate.

Definitely not the Nyquist x2.

They conclude by recommending around 3 to adequately sample.

I will need to see the argument for that in order to comment. Nyquist criteria is well established for band limited signal and in case of telescope aperture we have band limited signal with highest frequency depending on aperture size.

https://www.telescope-optics.net/mtf2.htm

image.png.c3e08f652e0b88574b5e2eac4f9b46a5.png

Maximum frequency is 1/lambda * F_ratio so we should sample at twice that frequency - or 2/lambda * F_ratio.

If you rearrange above equation

focal_length = 3 *aperture * pixel_size / wavelength * 1.22

=>

1 / pixel_size = (3 / 1.22) * aperture / (focal_length) * wavelength = (3 / 1.22) * 1 / f_ratio * wavelenght

Here we see that instead of 3 being quotient - 3/1.22 is used (again in error). This is because above formula is based on Airy disk size in spatial domain and not MTF in frequency domain. Just simply wrong application of Nysquist.

I came to correct value using above formula and experiment with actual data, so indeed sampling rate should be 2/f_ratio * wavelength.

15 minutes ago, Merlin66 said:

Which AVI processing software would you recommend/ suggest?

As far as I can tell PIPP has option to bin in software:

image.png.714b2a925c030278546f6ce6e27561ef.png

and I would certainly use that to calibrate my recordings and also do the binning. It can do both dark and flat calibration, and I would recommend using SER file format and 16 bit for recording and processing (in fact I would go with 32bit but not sure if calibration is done in 32bit in PIPP).

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Vlaiv,

I'll try to get a scan of the E&V pages for you.

My interest is solar images (Ha, CaK and white light) we normally use Firecapture to record a SER video of up to 2000 frames.

The focal ratio used is roughly based on the Nyquist but tempered by local seeing conditions. AS3! is used to "quality sort" and select say the "best" 30% of the frames (lucky imaging) which are then stacked as a 16bit TIFF file.

Subsequent processing (Registax6 or ImPPG) to tweak the image using wavelets/ L-R convolution.

I can't see, at the moment, how to include the CMOS software binning in our workflow. I have some raw SER files, which I can look at in PIPP.........

(Measuring a recent image, taken in H alpha, with the SM60DS/ ED80/ x1.65 barlow (efr = 12.4) gave 0.79 arcsec/ pixel on the ASI 1600MM (3.8 micron pixel))

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8 hours ago, Merlin66 said:

I can't see, at the moment, how to include the CMOS software binning in our workflow. I have some raw SER files, which I can look at in PIPP.........

(Measuring a recent image, taken in H alpha, with the SM60DS/ ED80/ x1.65 barlow (efr = 12.4) gave 0.79 arcsec/ pixel on the ASI 1600MM (3.8 micron pixel))

You don't need to bin your data if I'm reading things correctly - you are using F/12.4 with ASI1600, right?

Optimum sampling rate in Ha for 3.8um size pixels is F/11.58 - which is close enough to F/12.4 as is and no binning is needed.

In above case, binning was needed because quark was used with x4.2 integrated barlow and camera with 2.9um pixel size.

One would simply load SER files from fire capture - light SER, dark SER, flat SER, flat dark SER into PIPP, under input options select bin x3 and other options as wanted and as output - again SER/16bit, or possibly 32bit fits which would then be loaded in AS!3 for stacking. That would be the way to get binned data for those that need it to get closer to optimum sampling rate.

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