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Please recommend a Solar imaging camera

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#1 Patrick Cl

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Posted 25 July 2021 - 09:21 PM

My DMK 21AU618 has been an excellent and hard worker. It was the 'big thing' when I bought it, about 8 or 10 years ago.

 

But it has just died!

 

So I am looking for advice on a replacement to become a near-permanent part of my Lunt 60THa DS 'scope. Mono preferred, up-to-date CMOS.

I don't need a chip that's big enough to cover the whole surface in one go - I've got quite good at combining 4 or 6 panes.

I also use a 2.5X powermate  for Active regions.

 

I have tried an ASI 120MM and been amazed by the Newtons rings that it produces. Easy to remove with an out of focus flat but a serious handicap when

I have to resort to very short AVI or SER runs through shall gaps in cloud. (Very common problem when imaging from London, England.)

And it's best frame rate is 31 FPS when the ROI covers 1/4 of the Sun. I'd like about 100 FPS, if possible.

 

I have also tried one of the Celestron Skyris 236M cameras. I seem to have taken an instant dislike to the camera - I'm not sure why.

Yes, not logical, as it would probably do the job. But it also provides Newtons rings though nowhere nearly as impressive as the ASI 120.

 

Your advice please!

 

TIA

 

Patrick



#2 rigel123

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Posted 26 July 2021 - 05:46 AM

I really like my ASI174MM, but it does have a large enough chip for a full disk, which I like, and Newton Rings are basically nonexistent, at least in my particular case.  I also like my Skyris 236M though for closeups although Newton Rings are an issue particularly when barlowed.


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#3 viewer

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Posted 26 July 2021 - 08:46 AM

I think ASI290MM may suit you, if you are in for details and mosaics. Mine functions very well. Haven't seen any Newton rings or other issues so far.


Edited by viewer, 26 July 2021 - 08:48 AM.


#4 MalVeauX

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Posted 26 July 2021 - 08:52 AM

Hi,

 

Newtonian rings are not exclusive to a specific sensor or distributor of the sensor. They're the product of an imaging train that is not orthogonal to the sensor, ie, there's tilt in the system somewhere. This can happen on any system. It's exacerbated the longer the focal-ratio is.

 

If you're having issues with Newtonian rings, the issue is tilt, get a tilt adapter or work on getting sag or slop out of your imaging train. This is the source.

 

Buy a sensor based on what your goals are; such as the sensor size (FOV, such as full disc in one shot, or not, is relative here), pixel size (sampling is relative here), and FPS (potential FPS full pixel array vs cropped region or interest (ROI) relative to lucky imaging at various scales, courser can be slower, finer needs faster); relative to your budget.

 

Very best,


Edited by MalVeauX, 26 July 2021 - 09:09 AM.

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#5 hamers

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Posted 26 July 2021 - 09:08 AM

I also really like my ASI174MM and recently bought the Zwo tilt adapter, which nicely gets rid of Newton's rings. Fast frame transfer and supports ROI for even faster transfer of small areas.  



#6 Hank Molesky

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Posted 26 July 2021 - 10:35 AM

The ASI174MM is one of the favorite cameras in the forum. I love it.



#7 Patrick Cl

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Posted 26 July 2021 - 06:51 PM

Thank you, folks, for your comments.

 

I think I'll raid my piggy-bank for the extra cost of the ASI174MM.

And I'll probably find other uses for it.

 

As for Newtons Rings, I'm fairly sure that this particular ASI120 is the guilty party. Nothing that I do changes the pattern which even follows the camera to a completely different 'scope. I'm not very upset though. The camera was bought as a guide camera before I changed to off-axis guiding. It has kept me going after the DMK died.

 

I'll have to find out about 'Plastic Bag' flats with my Lunt 60THa so as to try full disc images. Should save me a lot of processing time when the Sun is in boring mode. I know nothing about the technique. Any tips, please?

 

Thank you, all,

 

Patrick



#8 LarryAlvarez

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Posted 27 July 2021 - 01:27 PM

One thing I noticed is that your 618 is a CCD with 5.6 micron pixels.  The 174 by contrast is a CMOS sensor and has almost the same size pixels but it has more of them.   Back in the day the forerunner to the 618, the 098bl sensor, was what we used for planetary imaging and solar because of its sensitivity and speed.  The 618 is 1/4" size while the 174 is almost a 1" size sensor.  That means you will see the full disk on your Lunt 60 at prime focus with just the camera and there will be space around it which will be ideal to capture the proms on the side of the full disk.  I've found the new IMX sensors from Sony really super sensitive to H-alpha and the 174 specifically is one of their fastest for frame rates too.  Be prepared for larger file sizes if you capture a video for later stacking.  If you want a preview of what and how the image of the Sun will fit on the sensor you can use this nice website to do it: Astronomy tools.   I have found it really handy when searching for that perfect setup.   It will allow you to add barlows and reducers too.  :)


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#9 Patrick Cl

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Posted 27 July 2021 - 07:33 PM

Thank you, Skylab,

 

Esp. for the link to Astronomy tools. Its going to be very useful!


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#10 lorenzo italy

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Posted 01 August 2021 - 11:55 AM

Hello everybody,
my curiosity.
The sensor of the ZWO174 is much larger than that of my 178.
But on the other hand, the 178 has the smallest pixels, over half in size.
I was wondering, if with the 178 and the Lunt 60mm I can shoot the whole solar disk with a certain resolution, even with the 174 of course I will take it all in full, but with a half resolution (due to the larger pixels).
If I want to equate (more or less) the resolution I would have to mount a Barlow of at least 2x with the 174.
But the field is reduced and the Sun no longer enters the sensor of the 174.

 

Is this my consideration correct?
Many times, reading here on the forum, I am tempted to change my 178, but then I see that maybe I do too much trouble.
Given that fortunately I have hardly ever seen the infamous grille problem.
I add an image taken from Astronomy tools, for a comparison between the various fields.

 

astronomy_tools_fov b.jpeg

 

Lorenzo



#11 MalVeauX

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Posted 01 August 2021 - 12:23 PM


Is this my consideration correct?
Many times, reading here on the forum, I am tempted to change my 178, but then I see that maybe I do too much trouble.
Given that fortunately I have hardly ever seen the infamous grille problem.
I add an image taken from Astronomy tools, for a comparison between the various fields.

 

Lorenzo

 

Hi,

 

Correct; if you use the IMX174 at native F7~F8.3, it's severely under-sampled. It will have low resolution, despite showing the full disc in the FOV. It's fine. But if you want to get all the resolution you can, you'd have to be closer to F20~F22 on the 5.86um pixels, but that would reduce the disc to a partial disc FOV of course on this IMX174 sensor.

 

The IMX178 pixels at 2.4um will sample HA at F9 or so, and so you're much closer to ideal sampling with a F7~F8.3 focal-ratio and can get the full disc FOV and the resolution will be significantly higher due to the sampling relationship. This largely would be a rather ideal budget camera for this. The only downside is that there's the issues with the grid pattern that is heavily documented. So if you try it, buy it from somewhere that allows unquestioned return policy so if you see the grid issue you can just return it. Otherwise, it would totally be a great solar camera due to its sensor size and pixel size for small solar scope full disc imaging.

 

Another option is to hunt Ebay for used security cameras that are being pulled from service. You can find lots of interesting cameras this way using common sensors to image with, some mono and larger format. I was able to buy two Flir cameras with IMX253 sensors (1.1" sensor, 3.45um pixels) for less than the cost of a single ASI174MM camera. This camera critically samples HA at F13 (so F14 is great) and the 1.1" size still allows full disc FOV, at critical sampling, from a 60mm F7~F8.3 solar scope like your Lunt.

 

Basically look up various 1" class sensors that sony produces and look up model cameras that use them. A 1" class sensor will produce a full disc image on a 1,000mm focal length basically. The rest is just adjusting things for sampling. But getting a big sensor makes life a lot easier for full disc imaging if you care about resolution and want to sample more appropriately to get the most resolution from your system that you can. Alternative, any M43 class sensor with any pixel size will also be useful for this (even more costly, but it hurts only once, no more fooling around looking for a budget camera).

 

Here's how that looks in FC:

 

Lunt 60mm F7 HA scope

2x Telenegative Amplifier (F14) with tilt adapter (to eliminate newtonian rings)

IMX253 sensor (1.1" 3.45um pixels, critically samples HA at F13)

 

Lunt60MT_2x_Tilt_IMX253_07312021.jpg

 

Real view in FireCapture:

 

FC_LuntMT_2x_IMX253_07312021.jpg

 

Results of that setup in one shot at critical sampling:

 

get.jpg?insecure

 

Very best,
 


Edited by MalVeauX, 01 August 2021 - 12:41 PM.

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#12 lorenzo italy

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Posted 01 August 2021 - 01:06 PM

Hi,

 

Correct; if you use the IMX174 at native F7~F8.3, it's severely under-sampled. It will have low resolution, despite showing the full disc in the FOV. It's fine. But if you want to get all the resolution you can, you'd have to be closer to F20~F22 on the 5.86um pixels, but that would reduce the disc to a partial disc FOV of course on this IMX174 sensor.

 

The IMX178 pixels at 2.4um will sample HA at F9 or so, and so you're much closer to ideal sampling with a F7~F8.3 focal-ratio and can get the full disc FOV and the resolution will be significantly higher due to the sampling relationship. This largely would be a rather ideal budget camera for this. The only downside is that there's the issues with the grid pattern that is heavily documented. So if you try it, buy it from somewhere that allows unquestioned return policy so if you see the grid issue you can just return it. Otherwise, it would totally be a great solar camera due to its sensor size and pixel size for small solar scope full disc imaging.

 

 

Thank you very much for the quick and accurate reply.
I already own the 178, and I'm satisfied with it.
I wanted a confirmation of what I thought, namely that if the 178 works well (no problem with grids) it is useless to buy a 174.
Always reading positive notes of 174 my hands itched, and my wallet trembled ...lol.gif

 

Lorenzo


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