How important is over/under-sampling? (RedCat51 + 2600MM)

Equipment CMOS
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Espen Torgersen avatar
Espen Torgersen avatar
Hi,
I see that the most popular combo here on AstroBin is the RC51 + ASI2600.



According to astronomy.tools this is not a perfect combo:



Is over/under-sampling an overrated quality, or does people mitigate this by other means?

Espen
Dan H. M. avatar
Dan H. M. avatar
You'll get differing opinions on this, but my own view is that ideal sampling is not a priority with a widefield scope like the Redcat.  Sure, you'd get better sampling with a sensor like the IMX492 or IMX183, but you'd have a smaller field of view (especially with the 183) and an inferior sensor to the ASI2600's IMX571 sensor.  I think the scope's short focal length is better served with a big, high-quality sensor that will let you capture wide fields.
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Jonny Bravo avatar
Jonny Bravo avatar
Sampling is one of those things that, in my opinion, gets blown way out of proportion. Examine the images produced with that scope/camera combination. Do you like how they look? If yes, then you'll probably be happy with the combo.
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Shane avatar
Shane avatar
I've been shooting with this exact equipment for a year now. It is much better when drizzled. But I agree with Eteocles, the better sensor and wider field is quite amazing. It becomes a challenge drizzling x2 as the files are quite large and if using Pixinsight, I've waited 12 hrs. per filter for WBPP to write masters, and I've crashed Pixinsight multiple times during processing. There are definite pro's and con's to this set up.  But overall the 2600MM is amazing…
Brian Puhl avatar
Brian Puhl avatar
Redcat is a scope that thrives on drizzle process.    The quality you get if you can collect enough integration time (20 hours or more) is pretty impressive.    I've had the priveledge of processing some redcat data to back that fact.   I believe drizzle should bring you somewhere in the range of 2 arc second sampling, maybe a bit lower.  I don't have the math on hand. 

Personally I have the Meade Quad 70mm at 350mm focal length.   I would highly recommend it over the redcat (similar price point) IF you can find it. They pop up on CN and astromart often.  I'm drizzling 20-30 hour data sets and honestly competing very close with the level of detail coming out of my 8" newt.    Granted, I am seeing limited.... Rarely do I see lower than 1 arc second conditions.     If you want to understand the power of drizzle, check out these two images I produced.    I would have never expected this level of detail from such a small scope. 

https://www.astrobin.com/699i9z/
https://www.astrobin.com/86x4im/

Make sure you open full resolution on them.  Even just clicking on the image full screen doesn't show the details. 

I never understood the power of undersample + drizzle until I bought this scope.
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Bray Falls avatar
Bray Falls avatar
3"/px is totally fine. Look at Deepskycolors image taken with 9um pixels on a reduced Takahashi. it is not a problem when you're going for large nebula structures
Dave Rust avatar
Dave Rust avatar
There can be an advantage to over sampling, too. With a color camera, I shoot BIN2. That eliminates bayer artifacts, lowers noise, and better matches the resolution of my DSO scope. Plus, processing time is 4 times faster. In effect, the 2600 changes from a 3.76 pixel to a 7.52, which just matches the FMWH of my scope (plus atmosphere). Add drizzle and the image is fantastic.
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Espen Torgersen avatar
Espen Torgersen avatar
Thank you all for the good feedback.
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