ngc 6888

[alacant]

Hi everyone

This is a good one to try ATM as it starts at a sensible -albeit rather low at 24º- altitude and ends at dawn just before the meridian. 

Very much an argument settler as I don't like filtered stuff, but was persuaded to try a UHC on this having inadvertently made the error of stating that I couldn't bring out the green bits in this target when using unfiltered frames. I had to admit defeat having seen the OIII (?) bits around the edges. IMO this filter compares favourable with the much praised used  L-enhance which we tried last year, especially the green bits. Should be good on the veil too when it gets to a sensible altitude. 

Thanks for looking and dslr users, do post your attempts at the same, especially if you used a filter of any type. 

700d on gso203. iso800, uhc ~4 hours iso800

Edited June 8, 2021 by alacant

[david_taurus83]

That looks great! I had seen your argument before with regards to the L-Enhance vs UHC. I might just get a decent UHC filter and pop it into the Redcat and 6D and see how it goes. I take it the UHC passes a broader spectrum than the L-Enhance but should also cut out a lot of LP as opposed to a normal LP filter?

[alacant]

Hi, yeah. I think if you have lp, you'd be better sticking to a lp filter. What the uhc seems to do is emphasise the green emission but totally destroy any notion of old-school colour.

Edited June 8, 2021 by alacant

[AndrewRrrrrr]

hi there, Nice image!

I'm very new to AP but enjoying the learning curve. Spent some time on this object over the last week or so. Here's what I got from last night, which I'm chuffed with but aware there's loads more to look into. (My efforts with APP are baby steps at the moment!)

C8 f6.3, 42x 300 second subs (3.5 hours total), Astro modified Canon 40D, ISO800, L-Enhance clip-in filter. 

Got the horizontal bands that I see other people getting with the Canon DSLRs. Anything that can be done about that?  Where do they come from as I don't see them in the individual frames. Can't see them in your image alacant.

[alacant]

30 minutes ago, AndrewRrrrrr said:

which I'm chuffed with

Lovely shot. You've done far better than we ever achieved with a C8. We would have loved to tame it as well as you have. So nice to get that magnification without having to enlarge in software.

30 minutes ago, AndrewRrrrrr said:

horizontal bands

Yeah. I think the older sensors in particular were prone to this. We had a 450d which was similar. It was one of the few DSLRs which responded to dark frames. Try the dark optimization algorithm in Siril. Worth a go?

Otherwise there are good post process band removal routines in most astro software but always better to try to remove via calibration.

Chip wise, the newer 18mp sensors seem to be band-free with the 24mp not far behind but not so good over longer focal lengths.

Cheers

Edited June 8, 2021 by alacant

[AndrewRrrrrr]

13 minutes ago, alacant said:

Lovely shot. You've done far better than we ever achieved with a C8. We would have loved to tame it as well as you have. So nice to get that magnification without having to enlarge in software.

Yeah. I think the older sensors in particular were prone to this. We had a 450d which was similar. It was one of the few DSLRs which responded to dark frames. Try the dark optimization algorithm in Siril. Worth a try?

Otherwise there are good post process band removal routines in most astro software but always better to try to remove via calibration.

Chip wise, the newer 18mp sensors seem to be band-free.

Cheers

thanks for your kind words! 🙂

Have to confess didn't take dark frames last night. I've only just got auto guiding working reasonably well so was enjoying the move from 60s subs to 300s! Didn't want to spend time taking 10x 300s darks, maybe wrong decision........ It's just occurred to me that I can do that tonight (cloudy here, but nearly same temp as last night) with the scope sat on the workbench in the garage...I will do that now, reprocess and see what happens, voyage of discovery...

Thanks for the tip re: Siril, will check it out. 

[alacant]

11 hours ago, AndrewRrrrrr said:

just occurred to me that I can do that tonight

Yes, of course. Just cover the telescope and/or use a dark room. Normally though, dark frames introduce more artefacts than they're worth. Just that in the case of the 40d, as with the 450d, they may just do what you want as the exception which proves the rule.

I didn't get past the trial stage of APP, but I seem to remember it had something similar to Siril's optiimistation. Have a search for dark scaling OWTTE. 

Siril also has a comprehensive banding algorithm.

One other thing we were'nt sure of is whether you're dithering in between frames. This, along with Siril's Linear Clip algorithm at something like 3 3 should also help.

Cheers

 

Edited June 9, 2021 by alacant

[AndrewRrrrrr]

3 hours ago, alacant said:

Yes, of course. Just cover the telescope and/or use a dark room. Normally though, dark frames introduce more artefacts than they're worth. Just that in the case of the 40d, as with the 450d, they may just do what you want as the exception which proves the rule.

I didn't get past the trial stage of APP, but I seem to remember it had something similar to Siril's optiimistation. Have a search for dark scaling OWTTE. 

Siril also has a comprehensive banding algorithm.

One other thing we were'nt sure of is whether you're dithering in between frames. This, along with Siril's Linear Clip algorithm at something like 3 3 should also help.

Cheers

 

Hi there,

Yes dithering between every frame, although I had APT set to dither "1" and this might not be enough. Going to try 5 next time.

You seem to have removed the bands very nicely there, will have a go myself.

Took 20 darks frames and reprocessed, it's an improvement, so it's darks all the way for my 40D! 

thanks again for the advice.

regards

Andrew