Why I think I should upgrade from a Nikon D5300 to a ZWO ASI294MC Pro

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pmwolsley
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Why I think I should upgrade from a Nikon D5300 to a ZWO ASI294MC Pro

#1

Post by pmwolsley »

I currently have a Ha modded Nikon D5300 and I want to get better data so I am looking at a cooled astrocam. I only image during the summer...my hands just can't take the cold. I don't have an observatory so I need to build and tear-down my rig nightly. Ideally I would like to image until 2 or 3 in the morning. I am retired so virtually any night with clear skies is ok with me. My dark site has Bortle 4 skies. I have an 8"EdgeHD SCT and a BK80ED refractor. The refractor is pretty easy to get beautiful results with but I really like imaging at FL=2032mm with my SCT. I really want to get to the point where I can pull out the faint dust in my images. This summer I was imaging at ISO200 (unity gain for the D5300) and 500 second exposures(Star saturation limit). I decided to study my data in the hope of figuring out what can be improved.
Ghost Nebula2.jpg
The last DSO target I imaged was the Ghost Nebula.
I am a programmer so I have written a program to display my RAW data. The D5300 RAW data ranges from 600(Black Level) to 16383(Saturation) counts. At ISO200 the Full well capacity of the D5300 is 16968. I used DCRAW to extract the RAW data and debayer the RAW data into a 16b TIFF without applying scaling or whitebalance. The values in the resulting TIFF file can be considered representative of the D5300 RAW data.
Ghost Nebula Cropped.jpg
I chose to focus in on a small area at the centre of my image because I wanted to study the range of values that are typical for these "faint fuzzies".

I picked a single LIGHT frame (DSC_0015.NEF) and wrote a program to only display RAW data that ranges from 560 to 815. Any values brighter than 815 are pure white. I also add a feature where I could position a yellow rectangle that is 30 x 30 pixels in size. I then calculated average, standard deviation and SNR values for these 900 pixels for each colour. No BIAS, DARKs or FLATs were used...this is RAW data right from the camera. You can clearly see the hot pixels.
RAW Example 1.jpg
In this image, the yellow rectangle is positioned at a very dark area. The average RAW data values are (R,G,B) 638, 641 and 617. The standard deviation values are (R,G,B) 5.8, 6.3 and 5.7. The SNR values were (R,G,B) 6.4, 6.6 and 3.0.

The average Red pixel value of 638 minus the 600 "black level" means that I was only able to collect 38 counts. At unity gain I believe that 1 count = 1 electron so I think I collected, on average, only 38 electrons in the red pixels for this area. Since this was a 500 second exposure this means, on average, I was collecting 1 electron every 13 seconds. I think my Ha modded D5300 has a quantum efficiency of 60%. A stock D5300 has a quantum efficiency of 55%. This means that I was collecting "red" photons at an average rate of one every 8 seconds.

My take-away from this analysis is that my 8"EdgeHD+D5300 system does not collect photons very fast. A cooled astrocam is not going to change this situation unless it has bigger pixels and/or higher quantum efficiency. If I was able to make these improvements I could take faster photos and, for the same 2-3am curfew I could have more photons counted in my data. To me...more photons counted = better data.
RAW Example 2.jpg
For this next image I have moved the yellow rectangle to directly beside a bright star where the nebulosity glows a bright yellow. The average values here are (R,G,B) 670, 674 and 635. Standard deviations are (R,G,B) 11.0, 10.1 and 7.6. SNR values are (R,G,B) 6.4, 7.4 and 4.6. Again, using the red pixels as the example, I notice that the average value has increased from 638 to 670. This change of 32 counts tells me that astrophotography is all about making very faint changes much more visible. This is a change of 32 counts in a data file that ranges from 600 to 16383 counts. The D5300 is a 14 bit camera. In order to achieve this 32 count difference I chose a 500 second exposure that resulted in several thousands of saturated pixels that most likely exceeded their fullwell capacity. I don't think I want to entertain a cooled astrocam that uses a 12 bit A/D because then that 32 count difference would require me to dramatically overexpose the stars creating real head-aches in digital developement. I don't know if HDR techniques can help in this situation.

So my opinion is that I need a 14 bit, or better, cooled astrocam with bigger pixels and a higher quantum efficiency.

Well I found one...the only issue is that it's a colour camera. It's the ZWO ASI294MC Pro. The pixel size increases from 3.91uM(D5300) to 4.63uM. The quantum efficiency increases from 60%(D5300 Ha modded) to over 75%. Both my D5300 and the ASI294MC Pro are 14 bit cameras and, of course, the ASI294MC Pro is cooled.

I want to be able to shoot narrowband so a colour camera is not ideal but there are several users (Trevor Jones) who are getting great results with duoband filters. I would purchase a manual filter wheel and just shoot RGB on moonless nights and narrowband on moonlit nights.

The only alternative camera I considered was the ASI1600MM Pro which is a clear winner for shooting narrowband. But it's pixel size is smaller (3.8uM) and it's quantum efficiency is the same (60%). This means that the ASI1600MM would be a slower camera than my D5300. Combine that with its 12 bit A/D and the ASI1600MM Pro was not for me. I also thought about how I would use an ASI1600MM and I figured I would need a motorized filterwheel to hold and sequence the LRGB+Ha+OII +OIII filters. This increased the price for an ASI1600MM Pro solution way higher than an ASI294MC Pro solution.

Thank-you for reading this and I look forward to your comments.

Peter
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Scopes:Celestron 8" EdgeHD + 0.7focal reducer, Skywatcher BK80ED +0.85 focal reducer
Mount:Celestron CGEM mount with QHY5II-M 177mm guider
Imaging:Nikon D5300 DSLR (H-Alpha Mod) QHYCCD QHY294C
Software:Digicamcontrol, DSS, StarTools, Lightroom, CaLIGHTs(I am the author of CaLIGHTs)
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Star Dad
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Re: Why I think I should upgrade from a Nikon D5300 to a ZWO ASI294MC Pro

#2

Post by Star Dad »

I'm in Bortle 5 skies and I bought the 294 because I'd never get a multi-filtered image done. CT only gets on average 4 clear nights per month and most of those are usually near a full moon. So I grab what I can get in full living color. I do have an O-III filter, but have yet to use it. I've been shooting the moon when it's up as I've not ever done that in the past. Great images resulting. I want to try mosaics of it next.

I can say that the 294 has given me fantastically better results that the Canon 70D - and it was really good. I am having to redo my post processing of images I took because I did not realize that my darks were flawed (somehow light got into the camera and the darks I had used wiped out the dimmer, more interesting details). The new results are really great and justify buying it. For you, though, its decision, decision. Good Luck!
"To be good is not enough when you dream of being great"

Orion 203mm/f4.9/1000mm, converted TASCO 114mm/f9/1000mm to steam punk, Meade 114mm/f9/1000, Coronado PST, Orion EQ-G, Ioptron Mini-Tower and iEQ30, Canon 70D, ASI120MM,ASI294MC
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pmwolsley
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Re: Why I think I should upgrade from a Nikon D5300 to a ZWO ASI294MC Pro

#3

Post by pmwolsley »

Star Dad wrote:
Fri Nov 15, 2019 9:03 pm
I'm in Bortle 5 skies and I bought the 294 because I'd never get a multi-filtered image done. CT only gets on average 4 clear nights per month and most of those are usually near a full moon. So I grab what I can get in full living color. I do have an O-III filter, but have yet to use it. I've been shooting the moon when it's up as I've not ever done that in the past. Great images resulting. I want to try mosaics of it next.

I can say that the 294 has given me fantastically better results that the Canon 70D - and it was really good. I am having to redo my post processing of images I took because I did not realize that my darks were flawed (somehow light got into the camera and the darks I had used wiped out the dimmer, more interesting details). The new results are really great and justify buying it. For you, though, its decision, decision. Good Luck!
Star Dad,
Thanks for your feedback. I expect a learning curve when I take the plunge. Thanks for the heads-up regarding DARKs. I am taking my time making this decision. It just fantastic to be able to bounce my ideas off of people who share my hobby and are at so many different points in their astrophotography journey.

Peter
Scopes:Celestron 8" EdgeHD + 0.7focal reducer, Skywatcher BK80ED +0.85 focal reducer
Mount:Celestron CGEM mount with QHY5II-M 177mm guider
Imaging:Nikon D5300 DSLR (H-Alpha Mod) QHYCCD QHY294C
Software:Digicamcontrol, DSS, StarTools, Lightroom, CaLIGHTs(I am the author of CaLIGHTs)
Dark site: Class 4 Bortle
Home site:Class 8 Bortle
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Re: Why I think I should upgrade from a Nikon D5300 to a ZWO ASI294MC Pro

#4

Post by Star Dad »

Yeah, I understand. I took about three months to make my decision. My initial results, while about the same quality - maybe even a little worse than the Canon 70D, were disappointing, but I still justified it based on wear and tear of the shutter and vastly decreased download time (I can get 90 minutes worth of images in what use to be only 60 minutes of exposures @ 1 minute each). Now that I've discovered the error in the darks the images are much, much better. I took an image of the Lagoon Nebula (with the bad darks) and it came out beautifully. I have yet to reprocess it, and I can't wait to. But my schedule has been too overwhelming lately and I've had little time for AP).

There are a couple of others here that have a 294 as well. I think it is good to get advice from various people - as we all have different experiences. Note that when I bought mine I had to wait for the unit to clear customs because of the trade wars... it took a couple of weeks, so if you plan to buy one take that into account.
"To be good is not enough when you dream of being great"

Orion 203mm/f4.9/1000mm, converted TASCO 114mm/f9/1000mm to steam punk, Meade 114mm/f9/1000, Coronado PST, Orion EQ-G, Ioptron Mini-Tower and iEQ30, Canon 70D, ASI120MM,ASI294MC
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Re: Why I think I should upgrade from a Nikon D5300 to a ZWO ASI294MC Pro

#5

Post by pmwolsley »

Comparison.jpg
I don't know if this is valid but decided to create a chart summarizing my thoughts. I used the concept of a race where each camera would be connected to my telescope and then I would determine how much exposure time it would take for each camera to record a value of 1000 counts. I assumed that all three cameras were using their unity gain settings so that 1 electron = 1 count. Any black level(bias) offset was subtracted so that total darkness = zero counts. The calculation used only pixel area and quantum efficiency. I also assumed that all three cameras were recording color data and not narrowband.

You can see that the ASI1600MM is slightly slower than my D5300. I assumed that the Ha mod for my D5300 raised it's quantum efficiency from 55% to 60%. This may be pessimistic. If the QE for my D5300 is better than 60% then this would make the ASI1600M appear even slower.

The ASI294MC is significantly faster than the ASI1600MM. I suspect this is due to the ASI294MC having a back-side-illuminated (BSI) chip. The ASI294MC gets the job done almost twice as fast as the ASI1600MM. I would also conclude that even when narrowband imaging, the exposure time penalty for the ASI294MC would be acceptable when compared to the ASI1600MM.

Peter
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Scopes:Celestron 8" EdgeHD + 0.7focal reducer, Skywatcher BK80ED +0.85 focal reducer
Mount:Celestron CGEM mount with QHY5II-M 177mm guider
Imaging:Nikon D5300 DSLR (H-Alpha Mod) QHYCCD QHY294C
Software:Digicamcontrol, DSS, StarTools, Lightroom, CaLIGHTs(I am the author of CaLIGHTs)
Dark site: Class 4 Bortle
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yobbo89
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Re: Why I think I should upgrade from a Nikon D5300 to a ZWO ASI294MC Pro

#6

Post by yobbo89 »

It seems you have the numbers down pat, i can only add that i agree that the asi 1600 is not the right choice for you, it lacks in dynamic range and the protective lamination on the chip produces micro lensing from bright targets, the targets i image will have a lot of oversaturated stars/central regions , i almost refuse to do blending in post or hdr stacking with multiple different exposures as i never have a great success in it. dslr cameras do very well , it's just the practicality of them which is a bit annoying, getting the dark frames done at the nights temperature and cataloging it,lack of computer control support ect.

i'm just waiting until astronomy cameras catch up with the chip support off dslr spec/sizes , I don't think there are any or many full frame mono astro cameras on the market and if so at a reasonable price..

I think the majority of large pixel size cameras are ccd chips , your current setup puts out 0.40 /pixel

give this page a whirl.

https://optcorp.com/collections/telescope-cameras

you can filter by adc , pixel size, sensor type ectt, you might find something of interest.
scopes :gso/bintel f4 12"truss tube, bresser messier ar127s /skywatcher 10'' dob,meade 12'' f10 lx200 sct
cameras : asi 1600mm-c/asi1600mm-c,asi120mc,prostar lp guidecam, nikkon d60, sony a7,asi 290 mm
mounts : eq6 pro/eq8/mesu 200 v2
filters : 2'' astronomik lp/badder lrgb h-a,sII,oIII,h-b,Baader Solar Continuum, chroma 3nm ha,sii,oiii,nii,rgb,lowglow,uv/ir,Thousand Oaks Solar Filter,1.25'' #47 violet,pro planet 742 ir,pro planet 807 ir,pro planet 642 bp ir.
extras : skywatcher f4 aplanatic cc, Baader MPCC MKIII Coma Corrector,Orion Field Flattener,zwo 1.25''adc.starlight maxi 2" 9x filter wheel,tele vue 2x barlow .

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Re: Why I think I should upgrade from a Nikon D5300 to a ZWO ASI294MC Pro

#7

Post by pmwolsley »

yobbo89 wrote:
Sun Nov 17, 2019 7:19 am
It seems you have the numbers down pat, i can only add that i agree that the asi 1600 is not the right choice for you, it lacks in dynamic range and the protective lamination on the chip produces micro lensing from bright targets, the targets i image will have a lot of oversaturated stars/central regions , i almost refuse to do blending in post or hdr stacking with multiple different exposures as i never have a great success in it. dslr cameras do very well , it's just the practicality of them which is a bit annoying, getting the dark frames done at the nights temperature and cataloging it,lack of computer control support ect.

i'm just waiting until astronomy cameras catch up with the chip support off dslr spec/sizes , I don't think there are any or many full frame mono astro cameras on the market and if so at a reasonable price..

I think the majority of large pixel size cameras are ccd chips , your current setup puts out 0.40 /pixel

give this page a whirl.

https://optcorp.com/collections/telescope-cameras

you can filter by adc , pixel size, sensor type ectt, you might find something of interest.
yobbo89,
Thanks so much for your feedback. I really struggled trying to figure out this upgrade path. You can't help but feel that you are making assumptions that are way off track. That's why getting this kind of feedback from fellow astrophotographers is so valuable.

I agree that DSLR DARKs are problematic. I want to polish-up a DSLR LIGHT frame calibration program I have written so that I can sell it. But I want to charge a small fee because it has taken me well over 1,000 hours to get the math right. One benefit of my program is it's DARK frame optimization which works flawlessly with my D5300. It has given me the freedom to generate one master dark that I can use for the entire year for every night, every exposure length and ,within reason, a wide range of ISOs. It works so well that this year I calibrated all of my 2019 data using a single master DARK that I created in my basement, at room temperature, during the winter. I don't dither...there is simply no need. All of my calibrated images show no DARK current "walking noise". My 8"EdgeHD has a significant issue with differential flexure mainly because I use a separate guide scope...an OAG is on my xmas list. Sure, on occasion, I see elongated stars in my final images but never do I see "walking noise". My calibration application works with a list of LIGHT frames and as it calibrates each LIGHT frame it logs the dark frame optimization stats which always appear to be adjusting with the imaging chip temperature as it heats up internally or it cools down with the ambient temperature over the course of the evening. It's a winter project for me to finish.

Peter
Scopes:Celestron 8" EdgeHD + 0.7focal reducer, Skywatcher BK80ED +0.85 focal reducer
Mount:Celestron CGEM mount with QHY5II-M 177mm guider
Imaging:Nikon D5300 DSLR (H-Alpha Mod) QHYCCD QHY294C
Software:Digicamcontrol, DSS, StarTools, Lightroom, CaLIGHTs(I am the author of CaLIGHTs)
Dark site: Class 4 Bortle
Home site:Class 8 Bortle
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pmwolsley
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Re: Why I think I should upgrade from a Nikon D5300 to a ZWO ASI294MC Pro

#8

Post by pmwolsley »

yobbo89 wrote:
Sun Nov 17, 2019 7:19 am
It seems you have the numbers down pat, i can only add that i agree that the asi 1600 is not the right choice for you, it lacks in dynamic range and the protective lamination on the chip produces micro lensing from bright targets, the targets i image will have a lot of oversaturated stars/central regions , i almost refuse to do blending in post or hdr stacking with multiple different exposures as i never have a great success in it. dslr cameras do very well , it's just the practicality of them which is a bit annoying, getting the dark frames done at the nights temperature and cataloging it,lack of computer control support ect.

i'm just waiting until astronomy cameras catch up with the chip support off dslr spec/sizes , I don't think there are any or many full frame mono astro cameras on the market and if so at a reasonable price..

I think the majority of large pixel size cameras are ccd chips , your current setup puts out 0.40 /pixel

give this page a whirl.

https://optcorp.com/collections/telescope-cameras

you can filter by adc , pixel size, sensor type ectt, you might find something of interest.
yobbo89,
Thanks for the link. Very interesting. The comparison chart does not seem to pick up the ASI294MC with it's filters. Also the read noise is quote as 7e which seems wrong. It is the peak read noise but it looks like this is way below unity gain. I also browsed Cloudy Nights and there is a lot of chatter there about a flaw in the cooler design of this camera. It seems to work ok for roughly 2 minute exposures but if you are doing long exposure at full cooling there is a strong cooling gradient on the chip. This is caused by the cold finger not covering the full dimension of the chip. The result being that the edges of the chip see a strong thermal gradient which makes DARK frames very problematic to generate. Have you or anyone else experienced this issue?

Peter
Scopes:Celestron 8" EdgeHD + 0.7focal reducer, Skywatcher BK80ED +0.85 focal reducer
Mount:Celestron CGEM mount with QHY5II-M 177mm guider
Imaging:Nikon D5300 DSLR (H-Alpha Mod) QHYCCD QHY294C
Software:Digicamcontrol, DSS, StarTools, Lightroom, CaLIGHTs(I am the author of CaLIGHTs)
Dark site: Class 4 Bortle
Home site:Class 8 Bortle
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