Saturn 24th July

[Tommohawk]

Hi All. Finally got a break in the clouds to have a go at Saturn - may prove to be last for the year looking at the forecast!

Pretty windy night, so wasn't expecting too much especially with only 18 degrees elevation - seeing was OK ish. I decided to go for lots of sets and not worry too much about rotation - I had hoped to get a glimpse of the hexagon since its showing so well, but with only 200mm scope that's probably a tall order. I might try derotation when I get a mo, but not holding ny breath! I used the powermate x5 as usual so pushing my luck (as usual) at F24 ish. Camera is ASI290MM.

Grabbed 4 sets of 3 RGB @60 secs per go so 12mins of each RG and B with Firecapture. Had to really push the gain. R at 390 still only gave histo average 66%, G at 400 only gave 45%, and B at 425 gave a miserable 36%.

Processed and quality ordered in PIPP, (12 of each colour in join mode) then to AS!2 for stacking only, then Registax for wavelets etc on each of the RG and B, then combine in RGB in PS with slight sharpening.

One thing I proved is that putting a delay between each individual exposure fixed the problem I have with wacky histo readings in the log files. If a sub catches even a few frames of the previous colour as the filter wheel turns it really knocks the recorded histo.

So here's my best shot - hope you like it, please do comment or criticize - always room for improvement!

[michael.h.f.wilkinson]

Very nice result

[Tommohawk]

23 hours ago, michael.h.f.wilkinson said:

Very nice result

Thanks for that and also for all the likes.

BTW I meant to add in the original post that one of the frustrating things about working with such a slow set-up is that you get very slow frame rates. I guess this is pretty obvious really, but I was surprised how much impact it had on Saturn. I think this is aggravated by the low elevation  which must lose a certain amount of light also.

The ASI290 with USB 3 connection and reduced region of interest can in theory achieve around 400fps - but even with the gain racked up I was using 30ms expsosures sp the best I could get was 33fps. By comparison, I got nicely over 100 fps with Jupiter even with unity (350) gain.

Take home message is it doesn't matter what the camera and laptop are capable of, if the optics aren't up to it. Next year I hope to have something with a greater aperture which should help matters.

Roll on next year!

[Pete Presland]

A fine looking image, especially for the UK. It is a real tough target currently from these shores.

[Tommohawk]

On 03/08/2017 at 06:47, Pete Presland said:

A fine looking image, especially for the UK. It is a real tough target currently from these shores.

Thanks Pete.

I wondered afterwards if I might have done well to add some Lum data, if only because I might get a higher frame rate. Bit late now, but any thoughts on this?

[Grotemobile]

That is a really good image Tom . 30fps is about right for Saturn. Jupiter really produces

high frame rates. @ least you have got a good image of Saturn.

[Pete Presland]

1 hour ago, Tommohawk said:

Thanks Pete.

I wondered afterwards if I might have done well to add some Lum data, if only because I might get a higher frame rate. Bit late now, but any thoughts on this?

I would get some whatever, even if I wasn't going to use it for an LRGB image. I regularly try my range of astronomik filters to see what detail can be seen.