Messier 82: Short Exposure Using the ASI533MC Pro
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Please upload large images to photo sharing sites (flickr, etc) rather than trying to upload them as forum attachments.
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Please upload large images to photo sharing sites (flickr, etc) rather than trying to upload them as forum attachments.
Please share the equipment used and if possible camera settings to help others.
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umasscrew39
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Messier 82: Short Exposure Using the ASI533MC Pro
I had a decent evening so I tried to capture M82 (aka, The Cigar Galaxy) using the ZWO ASI533MC Pro (200g; 10 brightness; -10 temp) on a C11" EdgeHD @ f/7 with an Optolong L-Pro filter. Guiding was used on an AP1100 mount with 3-180s subs stacked using SC. Final alignment and integration of the stacks were performed using PixInsight. The total integration time was 1 hr. The ASI533MC Pro is a small square sensor which produces minimal noise and no amp glow. It uses the same new technology as the ASI2600MC Pro which I ordered a few weeks ago and am anxious to try. I think this image demonstrates how the newer CMOS cams can produce a decent image in just 1 hr in a Bortle 6 sky with average seeing and below average transparency.
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- Messier 82 final_.jpg (475.93 KiB) Viewed 1527 times
Re: Messier 82: Short Exposure Using the ASI533MC Pro
Very nice! Incredible FOV and great guiding.
I plugged your info into the SNR calculator. I came up with a Total Stack SNR of 9 which is quite good given only 1 hour of integration time.
Something to know about how SNR is calculated, M82's surface brightness is an important factor. Galaxies are modeled by an ellipse. The size of the ellipse depends on who you talk to. One authoritative source is the Saguaro Astronomy Club (SAC) which is used by many planetarium software packages. SAC says that the dimensions of M82 are 11.2 arcmin x 4.3 arcmin at magnitude 8.4. That magnitude is spread over the ellipse's area so it is less bright than the number 8.4 would suggest. Surface brightness is measured in magnitudes per square-arcsec. M82's surface brightness is 21.24.
I've attached a screenshot from Cartes du Ciel with a DSS overlay of M82. The image quality is poor but the galaxy is just a tad bit larger than your image. Notice the red ellipse and how much larger it is. The size of that red ellipse is what is going into the calculation of surface brightness. The bottom line is if you can integrate long enough to raise the SNR to 20+ then you have captured the outer reaches of the galaxy. That would be a world-class image.
If I may make one suggestion, given the low Read Noise of your camera there is not much to be gained by running with a 180s exposure. In fact you can lower it to 90s with only a very slight reduction in SNR.
Brian
I plugged your info into the SNR calculator. I came up with a Total Stack SNR of 9 which is quite good given only 1 hour of integration time.
Something to know about how SNR is calculated, M82's surface brightness is an important factor. Galaxies are modeled by an ellipse. The size of the ellipse depends on who you talk to. One authoritative source is the Saguaro Astronomy Club (SAC) which is used by many planetarium software packages. SAC says that the dimensions of M82 are 11.2 arcmin x 4.3 arcmin at magnitude 8.4. That magnitude is spread over the ellipse's area so it is less bright than the number 8.4 would suggest. Surface brightness is measured in magnitudes per square-arcsec. M82's surface brightness is 21.24.
I've attached a screenshot from Cartes du Ciel with a DSS overlay of M82. The image quality is poor but the galaxy is just a tad bit larger than your image. Notice the red ellipse and how much larger it is. The size of that red ellipse is what is going into the calculation of surface brightness. The bottom line is if you can integrate long enough to raise the SNR to 20+ then you have captured the outer reaches of the galaxy. That would be a world-class image.
If I may make one suggestion, given the low Read Noise of your camera there is not much to be gained by running with a 180s exposure. In fact you can lower it to 90s with only a very slight reduction in SNR.
Brian
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- M82 DSS overlay.jpg (63.93 KiB) Viewed 1525 times
Re: Messier 82: Short Exposure Using the ASI533MC Pro
Some good detail in the galaxy Bruce. Have a Cigar … 
Dave
Dave
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umasscrew39
- Posts: 408
- Joined: Fri Apr 28, 2017 1:28 pm
- Location: Central Florida
- Contact:
Re: Messier 82: Short Exposure Using the ASI533MC Pro
Dave....
good one....LOL . Thanks.
Brian...
Thanks for the comments. For me, it is not about a world class image. I prefer to get a good enough image to enjoy its beauty and then read the science about it. I have had many folks tell me to increase total exposure time on CN and Astrobin but it just isn’t my interest. I think the most time I have captured is 4 hrs of the Cocoon Nebula. I am sort of between people doing EEA and AP. So, neither group likes what I do
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Your point of reducing subs is good. Using 120 or 180 seems to be a knee jerk reaction as I use those longer times for narrow band.
good one....LOL . Thanks.
Brian...
Thanks for the comments. For me, it is not about a world class image. I prefer to get a good enough image to enjoy its beauty and then read the science about it. I have had many folks tell me to increase total exposure time on CN and Astrobin but it just isn’t my interest. I think the most time I have captured is 4 hrs of the Cocoon Nebula. I am sort of between people doing EEA and AP. So, neither group likes what I do
.Your point of reducing subs is good. Using 120 or 180 seems to be a knee jerk reaction as I use those longer times for narrow band.