1st Light with the ZWO2600MC Pro and the RASA 8 (NGC7000 Region)

[Catanonia]

For the 1st time ever, I had 2 hours of clear skies for new equipment on the day / night it arrived   Yeeha

Very impressed with the 2600 and the data it captures along with the wide APC Sensor FOV you get to bring out the maximum benefits of the RASA8.

I got this setup for the very limited dark opportunities I get just south of Manchester and the M6 Motorway and every opportunity I get I want to maximise.

So here we have 20x 4min subs at 2x bin on the RASA8 / ZWO2600MC Pro / ASI Air Pro and NEQ6 Pro  (not too shabby for under 1.5 hours)

I was using a lEnhance 2 inch filter in Bortle 6 skies and this was processed entirely in PI with Darks, Flats and Bias frames (not that the subs really needed them)

 

Now 2 issues I have and could do with some advice on as I would like to sort them out

• Stars to some corners are elongated and probably down to either tilt or spacing / backfocus that I need to sort out
• Stars are loosing their colours, either down to the lEnhance filter or the 100 gain I am using on the 2600. I might try to take a separate set of subs with gain 0 just for the star field.

I hope you like, I certainly have a lot more tinkering to do, but a good 1st light for a change and I am certainly happy with the progress so far.

 

Edited September 15, 2021 by Catanonia

[iantaylor2uk]

To be honest, with that set-up, I would go for 30 second subs (even with the L-enhance filter on) and bin 1x1 (you can always bin 2x2 in software later if you want). 

[Catanonia]

5 hours ago, iantaylor2uk said:

To be honest, with that set-up, I would go for 30 second subs (even with the L-enhance filter on) and bin 1x1 (you can always bin 2x2 in software later if you want). 

Several reasons

• I will not loose resolution at 2x bin due to chip size and pixel size on the 400mm RASA 8
• 2xbin is 4x photon gathering and so effectively 4 times as fast as 1xbin and on an F2 that is a lot
• More photons = more data and as longer exposure than say 30sec = better detail.
• Longer exposures reduce the noise massively with the 2600
• A lot less files to store and process.

 

Edited September 15, 2021 by Catanonia

[iantaylor2uk]

You have an f/2 system, you do not need 4 mins! 

 

[The Lazy Astronomer]

15 hours ago, Catanonia said:

Several reasons

• I will not loose resolution at 2x bin due to chip size and pixel size on the 400mm RASA 8
• 2xbin is 4x photon gathering and so effectively 4 times as fast as 1xbin and on an F2 that is a lot
• More photons = more data and as longer exposure than say 30sec = better detail.
• Longer exposures reduce the noise massively with the 2600
• A lot less files to store and process.

 

Actually, by binning you are potentially losing resolution, depending on the quality of your seeing on the night. The sampling rate of your setup at bin 1 is ~1.9"/px. On nights of average to good seeing, this would be a proper sampling rate. 

Using bin 2 on those nights will get you a higher SNR for a given integration time, but at the cost of resolution.

Another thing to consider is that with a couple of exceptions (e.g. cameras which use the IMX492 sensor), binning in CMOS cameras is done after each pixel has been read out. This means there is practically no difference between binning at capture and binning in post.

It would therefore be more advantageous for you to capture at bin 1 and consider binning during processing - you can use the measured FWHM of stars in your stacked image to determine if your conditions on the night mean binning is required.

And, while a longer exposure will capture more photons, once you've reached the point where your sky background has swamped the camera read noise, using longer exposures follows a law of diminishing returns.

The optimal exposure length for your setup, at bin 1 and gain 100, and assuming a fairly typical bortle 5 sky, is somewhere in the region of a few seconds, not minutes.

 

[Catanonia]

3 hours ago, The Lazy Astronomer said:

Actually, by binning you are potentially losing resolution, depending on the quality of your seeing on the night. The sampling rate of your setup at bin 1 is ~1.9"/px. On nights of average to good seeing, this would be a proper sampling rate. 

Using bin 2 on those nights will get you a higher SNR for a given integration time, but at the cost of resolution.

Another thing to consider is that with a couple of exceptions (e.g. cameras which use the IMX492 sensor), binning in CMOS cameras is done after each pixel has been read out. This means there is practically no difference between binning at capture and binning in post.

It would therefore be more advantageous for you to capture at bin 1 and consider binning during processing - you can use the measured FWHM of stars in your stacked image to determine if your conditions on the night mean binning is required.

And, while a longer exposure will capture more photons, once you've reached the point where your sky background has swamped the camera read noise, using longer exposures follows a law of diminishing returns.

The optimal exposure length for your setup, at bin 1 and gain 100, and assuming a fairly typical bortle 5 sky, is somewhere in the region of a few seconds, not minutes.

 

interesting and contrasting statements made in my other thread about reducing the F Stop of the RASA 8

Totally confused now.