Starwiz

On 18/05/2019 at 00:21, Cosmic Geoff said:

I would suggest using a dedicated planetary camera e.g. a ASI120MC and cropping to 320x240 pixels to boost the frame rate. Take a video of several thousand frames and set the stacker to use the best 20% or so.

Just as an example, I took this one three years ago from the car park at Westonbirt Arboretum, so also not far from Bristol.

It was taken a few days before opposition, but even so, Saturn only reached a maximum elevation of just over 10 degrees.  I imaged it a couple of hours before it reached it's maximum height, so it would have been below 10 degrees elevation at the time.

SW200p with the ASI120mc camera and captured a couple of thousand frames, stacking only around 20% of the best.  The division can be seen so I was very happy with it considering the low elevation.

John

1 hour ago, R26 oldtimer said:

Had a go at m51 this weekend

One of my favourite galaxies.  Good luck!

18 hours ago, Marmo720 said:

Ah must have been fun though. Once you start looking at the Universe, nothing else can compares right? 

I'd been a casual observer for many years, but always felt that I needed bigger apertures which I would never be able to afford.  Starting imaging eliminated the 'aperture fever' desire and is incredibly addictive, but also immensely satisfying.

2 hours ago, Marmo720 said:

As far as midlife crisis goes, it was between astronomy or paragliding.

Been there too during my first midlife crisis, with 29 parachute jumps almost 30 years ago now.  Much happier these days with the ability to explore deep space. ?

1 minute ago, R26 oldtimer said:

Ahhh, I already enjoy my aprilia tuono, even for a couple of trackdays per month...?

Oh well, you can't use that one then.  I'm in a similar dilemma with my CBR1100xx Super Blackbird.  ?

On 20/09/2018 at 18:43, R26 oldtimer said:

I don't think so. My wife was very excited as she witnessed the stretching of the picture where the nebulocity "magically" appeared out of nowhere.

I'm sure she's going to be just as excited when a Heq5 will appear out of nowhere too!

What? Won't she??

Just tell her you're having a mid-life crisis, and it was either this or a high-powered motorbike. ?

4 minutes ago, vlaiv said:

No, sensitivity does not play a part in that. Here we are talking about splitting one very large exposure into smaller ones. You can look at it that way - instead of doing 1 grand exposure lasting multiple hours, you break it into shorter ones and add up those shorter ones. All things that are important to final result add up with time - signal adds up, more you image more there is of it. Light pollution behaves the same - longer exposure you accumulate more light pollution. Thermal noise is also the same - more you image, more it builds up. Everything except the read noise - it is the same regardless of exposure length. 10 minute sub will have same read noise as 1 minute sub.

And that is the difference - more subs you take, more times you add read noise. Level of read noise determines how much it will impact final result - lower the read noise, less impact it will have compared to other sources. Most often read noise is compared to LP noise - look above at triangle explanation, but other noise sources also participate. With narrowband imaging you eliminate most of LP - this is why you need to go longer in NB - read noise becomes important factor.

ASI1600 has very low read noise compared to other sensors. Most CCDs and DSLRs have it at about 7-9e range, some low read noise models have it at 4-5e, but that is still x3 compared to ASI1600 (and other CMOS models). With DSLRs it's often recommended to go for ISO800 or similar instead of ISO100 - this is because CMOS sensors tend to have lower read noise at higher gain settings.

Thanks Vlaiv, that's very helpful information.

John

If all goes to plan I'll be starting imaging with an ASI1600mm-Pro next month.  The exposure times seem incredibly short compared to the 10 - 15 minutes I was doing with my modded Canon 1200d.  Is that because the sensor is much more sensitive on the ASI?

BTW, I've just emigrated to Malta, so looking forward to the cloudless skies.  Light pollution where I am is slightly worse than my UK location (Bortle 5 compared to Bortle 4), but I'll also be doing narrow-band as well as LRGB.

Welcome back!  

John

Hope I'm not stating the obvious, but is the meter switched to read AC not DC?

The reason I'm asking is that low cost digital multi-meters don't read true RMS AC volts, but use a diode to convert the AC voltage to DC then use a multiplication factor to come up with the result.  DC voltage passes quite happily through a diode, so if you had AC volts selected on your meter it could show around double the actual DC voltage, thus fooling the meter.  Swapping the leads over will show zero volts as current can only pass one way through the diode.

Just a thought 

John

Welcome to the SGL! 

John