Struggling with very dim targets - Forums

Topic starter

Feb 17, 2025

I recently collected some data on the Squid nebula and am underwhelmed with the result so I'm wondering if I'm doing something wrong. Here's the specs and the result:

ZWO FF65, ASI183MM Pro, ZWO 7nm Oxygen filter
78x 300 second subs (6.5 hours), 120 gain, Bortle 5, no moon
Very basic & quick processing to see what the signal was like: Graxpert, BlurX, StarX, STF stretch

I've had a chat with some friends and the following suggestions came up. I'm not convinced that any of this would be beneficial though:

Use a camera with bigger pixels like the 533 or 2600 as the pixels will collect more photons
Use a 2x Binning
Someone also suggested that unity gain for the IMX183 is 400 - I'm fairly sure this is incorrect & unity gain for this camera is 120.

I do understand that this target is incredibly dim and I have no problem spending 50+ hours on such a target, especially when using a fairly small aperture scope but I want to make sure I'm not making any mistakes in data acquisition before I devote so much time to it.

Thanks in advance for any help or advice!

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TiffsAndAstro

Feb 17, 2025 · Edited: Feb 17, 2025

I have about 12 hours ha/Oiii from bortle 6 during strong moon and a 72ed at F5.8 533 colour camera
Not a hint of squid.
Needs a lot more time I think

Was only discovered in 2014 someone told me I think.

Craig Dixon

Topic starter

Feb 17, 2025

TiffsAndAstro:
I have about 12 hours ha/Oiii from bortle 6 during strong moon and a 72ed at F5.8 533 colour camera
Not a hint of squid.
Needs a lot more time I think
Was only discovered in 2014 someone told me I think.

That's re-assuring, thanks.

TiffsAndAstro

Feb 17, 2025

Craig Dixon:
TiffsAndAstro:
I have about 12 hours ha/Oiii from bortle 6 during strong moon and a 72ed at F5.8 533 colour camera
Not a hint of squid.
Needs a lot more time I think
Was only discovered in 2014 someone told me I think.

That's re-assuring, thanks.

Good luck but don't be shocked if you need 30 hours, if it's possible at all

andrea tasselli

Frequent contributor

Feb 17, 2025

Craig Dixon:
I do understand that this target is incredibly dim and I have no problem spending 50+ hours on such a target, especially when using a fairly small aperture scope but I want to make sure I'm not making any mistakes in data acquisition before I devote so much time to it.

*You have far too small pixels for the aperture you're using. 1.2"/px is something I'd go with this subject with a 6" not a 2.55"!

And I can easily pick it up with a L-ENH filter in my B6/7 skies in 4 hours.

Craig Dixon

Topic starter

Feb 17, 2025

andrea tasselli:
Craig Dixon:
I do understand that this target is incredibly dim and I have no problem spending 50+ hours on such a target, especially when using a fairly small aperture scope but I want to make sure I'm not making any mistakes in data acquisition before I devote so much time to it.

*You have far too small pixels for the aperture you're using. 1.2"/px is something I'd go with this subject with a 6" not a 2.55"!

And I can easily pick it up with a L-ENH filter in my B6/7 skies in 4 hours.

Would you mind expanding on this please? Here's what I get from CCD suitability calculator:

I do have a 533MC Pro but this is paired with my Skywatcher 190MN

Arun H

Frequent contributor

Feb 17, 2025

Craig Dixon:
Use a camera with bigger pixels like the 533 or 2600 as the pixels will collect more photons
Use a 2x Binning
Someone also suggested that unity gain for the IMX183 is 400 -

Bigger pixels will, of course, collect more photons, but simply because they have larger area. They don't change the number of photons incident per unit area which is purely dictated by the f number. So, binning will have the same effect.

Also, there is nothing special about unity gain. Using a gain of 400 is absurdly high and unnecessarily cuts FWC for little benefit. From the graphs, gains of 100-150 are probably going to give you all the read noise benefit you could get.

I suspect your fundamental issue is just time.

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Dan Kearl

Feb 17, 2025 · Edited: Feb 17, 2025

https://cdn.astrobin.com/solutions/images/97817/2023/55752647-6752-4841-af1b-4c6d45be5612-1695673984.jpg
This is 45 hours in Bortle 8 with a 2600mc and a Radian Triad filter.
This target is a lot more friendly with a mono setup but is doable with a color camera if you stick with it.
You need a LOT more time with your camera.

andrea tasselli

Frequent contributor

Feb 17, 2025

Craig Dixon:
andrea tasselli:
Craig Dixon:
I do understand that this target is incredibly dim and I have no problem spending 50+ hours on such a target, especially when using a fairly small aperture scope but I want to make sure I'm not making any mistakes in data acquisition before I devote so much time to it.

*You have far too small pixels for the aperture you're using. 1.2"/px is something I'd go with this subject with a 6" not a 2.55"!

And I can easily pick it up with a L-ENH filter in my B6/7 skies in 4 hours.

Would you mind expanding on this please? Here's what I get from CCD suitability calculator:

I do have a 533MC Pro but this is paired with my Skywatcher 190MN

In your conditions and with such a small aperture for the given focal length you need a LOT more time and long integrations to budge it above the sky noise in any significant manner and I suspect you haven't got that much time, especially now, given the usual constraints of the UK weather.

Andrew

Feb 17, 2025

Run some graxpert ai version 3 denoise on it.

TiffsAndAstro

Feb 17, 2025

Dan Kearl:
https://cdn.astrobin.com/solutions/images/97817/2023/55752647-6752-4841-af1b-4c6d45be5612-1695673984.jpg
This is 45 hours in Bortle 8 with a 2600mc and a Radian Triad filter.
This target is a lot more friendly with a mono setup but is doable with a color camera if you stick with it.
You need a LOT more time with your camera.

quite fantastic, but 45 hours would take me a year with UK weather

AstroRBA

Feb 17, 2025

Craig Dixon:
Use a 2x Binning

Binning 2 should help and won't compromise resolution; those pixels are already vey tiny - gain 120 should be good and try 600 sec subs if you're able?

andrea tasselli

Frequent contributor

Feb 17, 2025

CMOS binning is no binning at all.

Craig Dixon

Topic starter

Feb 18, 2025

Thanks for the advice from everyone. There are a few conflicting opinions though so I'll start at the beginning and with what I feel is probably the most fundamental: Am I using an incorrect camera for the scope? I have two setups so two possible combinations for each:

Cameras: 183MM Pro and 533MC Pro
Scopes: ZWO FF65 and Skywatcher 190MN

Currently I have the 190MN with the 533MC Pro and the FF65 with the 183MM Pro. Would I be better off swapping these setups?

600 seconds shouldn't be a problem with the FF65 as it's on an AM3, which tracks very well.

andrea tasselli

Frequent contributor

Feb 18, 2025

Both cameras give approximately the same FOV for each scope (but with very different image scales). The IMX533 one will collect ~2.5x more light per pixel (minus the light loss due to the RGB on-chip organic filters, around 10% to 15%). The 190MN will collect around 7.5x more light than the 65FF (inclusive of verious light losses here). Since the target is very dim the best choice would be the 190MN with the IMX533 but its FOV wouldn't be large enought to capture enough of the surrounding nebula. My take is that the next best option given the absolute field constraints is to put the IMX533 on the 65FF with the catch that you need to use a NB filter. The L-ENH would do because it's very good in the OIII band which you want to enphasize even at the price of some resolution loss.

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Michael Jarvis

Feb 18, 2025

I like Andrea's comments above. Also consider using an Oiii/Sii NB filter to complement the L-ENH. Still, you are signing up for a lot of integration time for this target.

Dale Penkala

Feb 19, 2025

Hello Craig,

This is just my thoughts. 1st pretty much agree with what @andrea tasselli has stated, but my personal opinion is in all honestly I feel you need more aperture to really capture this object. As you mentioned it is VERY faint not to mention processing is key! With that said you will need narrow band data and a lot of it particularly in the OIII channel as that is the faintest part of the nebula.

For what it is worth, I shot this image last summer and collected a tad bit over 20hrs of data not to mention processed the data multitude of times to get something that I was happy enough with to post. If your interested here is my image: https://app.astrobin.com/u/DalePenkala?i=srmg2k there are a couple of revisions so take a look if your interested.

In either of your setups you’re going to need integration time in order to get this object. Its not an easy one as your finding out but I wish you the best of luck!

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kvastronomer

Feb 19, 2025

Here is what 72 hours of Oiii gives you from Bortle 1-2:
https://www.astrobin.com/eqofrn/#rB