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CraigT82

Mars 22nd Sep - Personal best

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Great seeing last night, captured four red and blue runs from about midnight to 1am, this is the second run which was the best of the four, and also my best ever.

Fullerscope with Altair 290m, APM 2.7x barlow (at 2.3x) and Baader filters (didn't use an ADC).

4.5 mins red & 4.5 mins blue with a synth green. No derotation.

AS3 (best 15%)>Registax>Gimp 2.1

MArs 220920 R(G)B Final.png

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Why don't you try R and G and make synt B?

B is rather susceptible to seeing because of short wavelengths. Maybe G will be less affected and you get somewhat sharper image (less of a dent in the planet :D )?

Edited by vlaiv
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5 minutes ago, vlaiv said:

Why don't you try R and G and make synt B?

How do you do that??

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Just now, CraigT82 said:

How do you do that??

Same way you create synthetic G, but in other direction?

How do you create synthetic G now? There must be some math involved and I bet that we can "reverse" it to create B from true R and G.

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I just add the R on top of the B as a layer, then set its opacity to 50% and flatten image and save as green. 

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1 minute ago, CraigT82 said:

I just add the R on top of the B as a layer, then set its opacity to 50% and flatten image and save as green. 

So your green is then (R+B)/2 if I'm not mistaken?

G = (R+B)/2 => B = 2*G-R

There you go, put two times G layer set to addition and once R layer set to subtraction and you have synthetic B layer from G and R.

(I thought that synthetic G is a bit more involved that this).

 

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Excellent work, well done.

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1 hour ago, CraigT82 said:

Great seeing last night, captured four red and blue runs from about midnight to 1am, this is the second run which was the best of the four, and also my best ever.

Craig,  I just saw these on Astrobin so came looking here for them and they are really cracking images. I'm curious why you didn't capture any frames with a green filter instead of relying on synth G? Clearly it works very well though :thumbright:

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21 minutes ago, geoflewis said:

Craig,  I just saw these on Astrobin so came looking here for them and they are really cracking images. I'm curious why you didn't capture any frames with a green filter instead of relying on synth G? Clearly it works very well though :thumbright:

Thanks Geof, Basically juts to save time on stacking and sharpening, only having to do two images for each sequence rather than three!

The other night (17th Sep) I captured RGB and I tried composing an image using all three and compared that with an image composed of just the R and B with synth G, and I found I preferred the synth G image. Wasn't much in it really but seemed a touch sharper to my eye. I think next time I'll try R and G and then synth the B as Vlaiv describes above.

Edited by CraigT82

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Never heard of a synth B, so that will be interesting. Most of the clouds are captured in the B channel, so I'd wonder whether you actual see those from a synth B. In good seeing green should give you better resolution than red, so applying a R, G or R+G as a luminance can also help, but it's already a great result. I'm currently taking a peek at my data from last night, but need to do other stuff this pm, so will get back to it later. Here's an IR and an R fyi....

2020-09-22-0026_3-G-IR-Mars_P30_l2_ap28_R6.jpg.19a468be5241d459c237b3bdbbe11edb.jpg2020-09-22-0029_8-G-R-Mars_P30_l2_ap28_R6.jpg.17cf998be3e727f2b16577f5244f138b.jpg

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Those are superb Geof, looking forward to seeing the finished version.

Yes I agree about the atmospheric details n the B channel. I have seen a Mars image by Jean Luc Dauvergne where he synthesised blue and it was an impressive image but I cant find it now.   Perhaps the best way forward for me on my next outing is to capture all three channels and play with them to see what works and what doesn't. I do like experimenting!

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1 hour ago, CraigT82 said:

Perhaps the best way forward for me on my next outing is to capture all three channels and play with them to see what works and what doesn't.

That sounds like a good plan 👌

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Well done Craig, seeing mixed here but good trans, very nicely detailed images indeed!

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Another great set of images Craig. Is the ice cap getting smaller BTW?

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6 hours ago, vlaiv said:

So your green is then (R+B)/2 if I'm not mistaken?

G = (R+B)/2 => B = 2*G-R

There you go, put two times G layer set to addition and once R layer set to subtraction and you have synthetic B layer from G and R.

(I thought that synthetic G is a bit more involved that this).

 

So by doing this I can capture longer on each channel?? If that is true than that is so cole! Why don't more people do that??

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6 hours ago, CraigT82 said:

I just add the R on top of the B as a layer, then set its opacity to 50% and flatten image and save as green. 

What does it mean to flatten image?

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17 minutes ago, Chrb1985 said:

What does it mean to flatten image?

In photoshop or gimp, you might have layers of different versions/stages of the image on the right hand side. Flattening the image just basically means combining those layers together (the ones that are visible anyway) into one single layer for saving. 

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Gorgeous detail Craig. Well done

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1 hour ago, Chrb1985 said:

So by doing this I can capture longer on each channel?? If that is true than that is so cole! Why don't more people do that??

Because you can't really do that if you want to be accurate.

There are cases where you can get exact information by skipping one of the channels. Like doing LRGB and skipping any of channels and going for RGB or LGB or LRG or LRB - provided that your RGB filters precisely add up to L filter and do not overlap.

With above approach - you are effectively making up once color, and in this case it was green. No reason for green to be equal to average of R and B, but sometimes for some targets it works good enough.

My idea was simply - why not use R and G to do the same and make up blue. It might not work as well on this target or maybe other formula will give better results for this target. Point is - in each case data is being made up to speed up things and as long as you can get away with that - it is fine.

Btw, there is very nice image captured by fellow astronomer from my country, have a look here:

https://aristarh.rs/astrofotografija/mars-september-21-2020/

Captured at the same time, although @CraigT82 travels in time judging by the fact that he has this image taken in next hour or so :D

This was taken with full RGB approach and we can see that synthetic G sort of works - but maybe clouds could be a bit thicker and richer in color with regular G.

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I really need to pay more attention to the text I'm putting on the image! 

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2 minutes ago, CraigT82 said:

I really need to pay more attention to the text I'm putting on the image! 

:D

Did you look at above image and especially stats for it?

Green seems to be captured at half the rate of other two colors - maybe such approach would be the best. You get proper color information but if green is not as important for the target - maybe only spend half of usual time on it and use the rest for R and B.

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