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Pixel count important?


zelonisv_bob
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I've been successfully using my Canon T1i for astrophotography, but with Black Friday specials being tossed in my direction, I wonder if it's time to upgrade to the Canon T6i, or even the T7i?  We're talking about the T1i's 15 MP versus the T6i's 24 MP sensors.  Am I correct in thinking that the greater number of available pixels of the T6i would be an advantage in lunar, solar and planetary imaging but not necessarily in deep sky imaging?  A quick look at the T7i's specs make it look pretty much like a T6i's but with maybe more wi-fi options, which I have no use for (I don't have a cell phone).  Besides, BJ's is not offering the newer model anyway.  Thank you for reading and, hopefully, responding.

Bob Z.

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It is not pixel count that is important, but pixel size and sensor size.

They need to be matched to your equipment and your typical imaging conditions.

Both the T6i and T7i have APS-C sized sensors with the same pixel size (3.7 microns). If one of them had a full-sized sensor then you would need to be sure that your optical train could provide a light cone that fully-illuminates the sensor. If not you would have significant vignetting of all your astroimages.

During a session with bad seeing, oversampling the image by using a camera with small pixels will not bring out more detail. What this means is that when the seeing is bad, you do not need a camera with small pictures to maximize detail. It also implies that if you typically image in areas with mediocre seeing that you may be able to save $$$ by buying a camera with larger pixels and not sacrifice any detail.

You should consider purchasing "The Handbook of Astronomical Image Processing" by Richard Berry and James Burnell from Willman-Bell Inc. This is discussed in detail in Chapter 1. However, I will warn you that the book is very technical in its theoretical treatment of imaging.

Another point. both cameras have WiFi connectivity. This has nothing to do with a cell phone, per se. Theoretically, it would allow a camera control app on your PC to communicate with the camera wirelessly, thus eliminating the cable between the camera and the PC. However, the Canon SDK will not connect to a camera over WiFi, so BYE doesn't really support this. Even if it did, you may want to use the USB connection anyway because it is the fastest way to get the images downloaded from the camera to the PC (USB 2.0 is faster than WiFi).

The street prices of the T6i and T7i are not that different and both are supported by BYE. The choice is yours. I have not heard whether the other features of the T7i would be valuable. For example, lower power consumption, lower noise, cooler operation would all benefit your imaging.

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Pixel Count is not a Variable applicable to Planetary Imaging with BYE/BYN, as Planetary Imaging is based on the LiveView Image Stream in order to get as close to a 1:1 Sensor-Pixel_to_Image-Pixel as possible.  Your T1i does essentially the same LiveView Resolution as the T6i/T7i.  The other pertinent Variable for Planetary Imaging is Frame Rate, and there is where the T6i/T7i might give you an advantage - although this would be dependent upon the Speed of your PC and the configuration of USB2 and Hub Connections between it and the DSLR.

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There is a realistic benefit of a T6i/T7i for DSO Imaging - Lower Noise.

While Gary Honis (of DSLR Full Spectrum Modification fame) doesn't have a page that specifically compares the T1i to the T6i, there is a lot of pertinent detail in this Comparison/Review of the Canon 6D (which is definitely outside your budget).  A few screens down, you can see the stats for your T1i contrasted to the "progression" of other Canon "T#i-series" Prosumer DSLRs - as well against the unfair competition of the 6D.

You can see that your T1i has a Sensor rather prone to Hot-Pixel and Thermal Noise, and the general trend in Improved Noise Handling with almost every generation of T#i-series DSLR.

Beyond that, the combo of your T1i and ES-127 APO is a really Good Match - the Scope's Dawes Limit of 0.91arcsec matches the Scope+T1i Pixel Resolution of 0.93arcsec/pixel which also matches the 1-2arcsec Seeing common to the New England area.

So, it all depends on where your AP Imaging Desires and Challenges lie.

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Thanks to you two fellows for your responses.  Previously, you had talked me out of a full-frame camera purchase, and now you've made me think twice about upgrading from my T1i to something newer; although, the thought of less thermal noise and fewer hot pixels might be worth considering.  Since first posting this morning, I've been doing research based upon the lenses offered with so-called "bundled" deals.  As it's been said, "If it looks too good to be true, maybe it ain't?"  It appears that the supplementary lenses (mostly zoom telephoto lenses) included with the basic camera body are not the latest nor best versions.  I will look into Gary Honis's article, AND, consider the Canon T6s body only.  By the way, that was an interesting remark (observation) about my New England's typical seeing conditions.  The Atlantic Ocean and my being just twenty miles from the coast are probably deleterious factors.  Thanks again.

Bob Z.  

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Bob,

I am not sure that the ocean hurts you very much.  I leave near mountains and our seeing is typically only mediocre.

Any EF lenses that you have with your T1i should work just fine with a new EOS DSLR body. I don't know about the percentage of hot pixels in new vs. old cameras, but I would expect them to be similar. Well within limits for being correctable through image calibration.

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astromann133, reviews of the T6i and T6s speak of the lower noise generated by their sensors, which are the same.  I'd appreciate lower noise in long deep-sky exposures.

Twenty miles east of my location is a city as well as a major north-south thruway with its toll booth area and the infamous New Hampshire state liquor store.  Those locations cast a lot of light skyward.  There are low mountains only 3 miles west of me.  Woe is I. 

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Monochrome astrophotography would require not only an expensive CCD-type of camera but also expensive 2" filters and a filter holder.  I assume that some other form of imaging software would have to be purchased in order to process the output of a CCD camera.  DSLRs are so much simpler, and already capture images in color.  That's really good enough for me.

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