Pier 11 - Rosette Nebula - advice on sub lengths

Hi John,

Maybe over the next couple of days one of the roboscopes team may find time and offer a bit of advice. I'm assuming that you intend to use the RGB filters only and not any narrowband such as Hydrogen alpha, since that will have a large bearing on the total imaging (integration) time. Now a bit of waffle, hopefully which will not put you off.

The quality of the resulting image will largely depend upon the overall integration time together to a small degree with processing experience. Noise in the data is your big enemy. What those values, exposure times and the number of them (integration time) need to be will be determined by your level of expectation. Not a satisfactory answer and hence your reason for asking here in the first place. Doh!  Also the rule of diminishing returns applies, so once you've captured enough time to produce something just about to your satisfaction, you might need to double it to get a really noticeable improvement!

Hopefully in the meantime someone will be make a suggestion that will likely produce a 'reasonable' image of that nice nebula, but at a reasonable cost to you. I'll look at some examples on the Astrobin site later and see if there is anything there on which a good guess can be made, and reply probably this evening with what, if anything, I find.

We all go through this learning curve, but it's definitely something that is very straightforward to do when you have your own setup and are able to continue to capture the data until you're satisfied with the results. On here that means more money unfortunately.

Best regards,

Ray

Ray,
Once again, thank you for taking the time to give me such good advice, very much appreciated.
John

Hi John, 

Having looked at some examples I found that most were taken using either a DSLR or colour camera, and those taken using a mono camera to my surprise mainly took advantage of using narrowband filters. The best I could find leads me to think that you ought to try 40 minutes in each of 3 colours, as 20 exposures each of 120 seconds. A total of 2 hours. It's likely you'll find that there is a lot of noise when you look closely at the result. That's something we all experience when we try and guess the amount of exposure needed on something new. . The best remedy is capturing more data but unless you have your own setup that means additional cost to you and maybe disappointment at the relatively little improvement it brought about. Alternatively you could experiment using various noise reduction techniques to mitigate it, that's something we all do. You can always submit a second booking after processing the Rosette, but for I'd stick with the 2 hours and see what you get. 

I did reply last night but for some reason it failed to get posted, likely a finger problem on my part. In that original reply I also mentioned that with the current moon phase which affects the number of days we can capture using broadband filters, there is no urgency to submit it right away. Perhaps someone will offer a better alternative based on their own experience in which case I'd use theirs. 

Also just remembered that I mentioned  the info on the forum regarding hours being rounded up when making a booking. You may have realised it after you submitted the 2 1/2 hours on m31, as you could have requested 3 hours, 360 subs (exposures). Even if you did capture those extra frames, without zooming in you'd be hard pushed to notice the improvement on that  excellent image you produced. The law of diminishing returns applies as you did capture plenty of data first time around. Apologies for rabitting on. 

Best wishes and apologies for my failure to post that reply to you last night as I said I would. 

Ray 

Ray,
Thanks so much for your help and advice, above and beyond, very much appreciated.
I will take your advice and see how it comes out.
Nothing ventured and all that.

I also took your advice and got into the sample data from Pier 7.  My first attempt at RGB processing so good to be able to do that.  Results are interesting - seems quite noisy and I think I overdid the Reds in post-processing but I am learning loads.

As always, thank you!
John

John, 

Just finished making a post myself then saw yours. Only too pleased to give a little help, I've received plenty myself in the past. That's a nice image and something you can keep going back to as you pick up more experience. You probably didn't have any calibration files so you've done a good job on taming the noise already. 

I cannot remember now but does that dataset come with data from not just the RGB filters but Ha and O3 also? If so you can make a pseudo colour image using the data from just those narrowband filters. Please just ask if you have any questions. 

Best regards, 

Ray