Question - California Nebula

[AstroGS]

I am seeking some advice for tonight as I am planning to image the California Nebula in narrowband with the Redcat51 + 1600MM.

The skies are supposed to be clear for tonight and a good view hours during the week but, the full moon will make things very challenging. I am chasing this and the Rosette Nebula for some time now but, when we get a new moon the skies are cloudy and when the skies are clear..... you know what I mean.

So, ideally for these targets I would push exposure time to 900 or even 1200 secs (hoping to acquire 20-30 subs for each Ha, SII and OIII) in order to get as much detail as possible and probably 20 x 120 sec subs of LRGB for stars.

My concern is if the subs will be highly impacted by the full moon - especially at those long exposures? I am actually trying to figure out if is should go at all for that target and if yes, should I go for long exposures or shorter ones, due to the moon?

Below is an image from Sky Safari on the target vs moon.

 

 

 

Edited February 5, 2023 by George Sinanis

[Elp]

Having tried imaging at 300s as a limit myself, I haven't really noticed a difference going down to say 60s but taking more of them. With my faster systems taking 30s down to 15s subs I normally multiply the total amount taken to account for the change.

[Simon Pepper]

I ran a test on this target using 1600mm pro and redcat 300s, 600s and 1000s and the best SNR was 600s. This was on the 21st of Nov 2021 no idea on the moon phase at this point but you could roll back the date on Stelarium and see. I would probably stick to 300s or even less with the moon being full maybe 180? It depends on your filter as well I wouldnt bother with Oiii at all stick with Ha the smaller the pass the better. Good luck!

Edited February 5, 2023 by Simon Pepper

[AstroGS]

41 minutes ago, Simon Pepper said:

I ran a test on this target using 1600mm pro and redcat 300s, 600s and 1000s and the best SNR was 600s. This was on the 21st of Nov 2021 no idea on the moon phase at this point but you could roll back the date on Stelarium and see. I would probably stick to 300s or even less with the moon being full maybe 180? It depends on your filter as well I wouldnt bother with Oiii at all stick with Ha the smaller the pass the better. Good luck!

Interesting input - thank you.

You were shooting with a full moon back then (21/11/2021) - here is screenshot from that night 😉 . I am using the ZWO 6nm 36mm filters.

I would give a try (starting with Ha) at 600 secs and review the first subs before to commit on the whole session on that exp time.

 

 

[AstroGS]

1 hour ago, Elp said:

Having tried imaging at 300s as a limit myself, I haven't really noticed a difference going down to say 60s but taking more of them. With my faster systems taking 30s down to 15s subs I normally multiply the total amount taken to account for the change.

You are shooting with a C6 hyper star - correct? Those SCT+Hyperstar/ RASA designs are in my head for some time now...... The RASA8 is in my shopping list.

I have never gone below 120 sec, the best SNR for me with the Redcat/ASI2600MC was always the 600 secs. But, I have never images with a mono before. It will be actually my first proper evening tonight.

[Simon Pepper]

Oh wow interesting I didn't realise that. Here are the three images. Looking agai it looks like the 300s may have had some high cloud or I have used a screen shot or compressed image. I think the middle one looks best

Edited February 5, 2023 by Simon Pepper

[Elp]

The true test would be to try a varying number of exposures but make sure the TOTAL time for each stack is the same. That's the only way you can compare.

I've imaged with the moon right next to a target, when I did HA for my M16 image last year, didn't affect it at all but I was doing 60s exposures with a standard 6.5/7 nm filter. 

Mono will be slightly more sensitive in the same given time.

HS is good within limitations, my apo is sharper but once you've experienced the speed it's difficult to go back to a standard setup. It's similar with the SY135 lens too.

Edited February 5, 2023 by Elp

[Simon Pepper]

15 minutes ago, George Sinanis said:

You are shooting with a C6 hyper star - correct? Those SCT+Hyperstar/ RASA designs are in my head for some time now...... The RASA8 is in my shopping list.

I have never gone below 120 sec, the best SNR for me with the Redcat/ASI2600MC was always the 600 secs. But, I have never images with a mono before. It will be actually my first proper evening tonight.

I am trying to add the 2600mc to my armoury so will be interesting to know your thoughts on the 1600mm and how they compare. I love my mono camera even thought its the outdated 1600  OSC does have a place though its convenient hence why I am trying to source a 2600.