Where's my Saturn? I want it and I want it now! ;-)

[Rusted]

Hi there,

Should I be able to see Saturn on my laptop or computer monitor when I'm using a 7" f/12 refractor with a ZWO120MC USB3 and SharpCap? No filters.

I centred visually with the drives tracking so Saturn was absolutely central and the camera sharply focused on the nearby Moon just moments before.
Visually, Saturn looked bright despite its despicably low altitude. Full gain & longest exposure in SharpCap. I was fully expecting to see stars but didn't! Nowt!

Still no Saturn! 

I have really no idea what to expect from the ZWO at lower light levels.

[Davey-T]

I have found it very tricky to get planets in the camera FOV, I think that's why they invented flip mirrors  I sometimes remove the camera and squint up the scope to make sure I can see the planet but it still needs a bit of nudging to get it on the camera.

I'm using 10"SCT F/l 2500

It helps to have a finder with four illuminated crosshairs so you get a little square in the middle but it needs to be very accurately aligned with the main scope / camera.

I use Firecapture that has separate profiles for different Solar System objects with different exposure times, it needs the latest ZWO SDK to work.

Dave

[Davey-T]

Something else I've resorted to, if you're guiding, is to centre a bright star on the imaging camera using onscreen crosshairs then mark it's position on the PHD screen, slew to Saturn and use the PHD screen to get it aligned.

Dave 

[Rusted]

Thanks Dave.

My original post was really questioning the sensitivity of the ZWO.
I removed the camera and checked that Saturn was lighting up the field of view.
I refitted an eyepiece and made Saturn absolutely central.
I gave the focuser a gentle push in all directions but still nothing showed on the screens.
I used the ultra slow AWR drives to wander around the immediate area.
The camera was perfectly focused on the Moon and hard up against the eyepiece socket stop.
With a 2160mm focal length it should have been clearly visible in size.
I engaged LX in SharpCap and found several bright blue pixels and eventually a completely spotty screen.
The spots weren't stars. They were fixed and only moved with the camera. Not with the telescope. Presumably just noise?
It was completely baffling at the time. I had captured videos of Jupiter at a similar low altitude not long ago.
Jupiter wasn't bright but it was clearly visible on the screens. Saturn should have been similar.
The Goto slew from the nearby Moon had placed Saturn dead central in the eyepiece. Just for a change.
After messing about for half an hour I imagined it must be operator error.
Or I had cooked the ZWO on the sun.
That couldn't have been true because I had no problem capturing the low, half Moon just before.

[CraigT82]

You say you had it set it to longest exposure in sharpcap, isnt that 1000 seconds?! 

You should 100% be able to get a nice bright preview on Saturn on the screen, so something definitely amiss with either the exposure settings,  or the planet wasnt on the chip??

[Rusted]

Thanks but I was certain I had the planet central on the camera.

[DKNicholson]

I have experienced a very similar problem and have gone through pretty much the same process as yourself. My camera is also the ZWO ASI120MC but my telescope is a Meade LX90-8" SCT. Eventually I found that there were two issues (1) initially the planet was always outside the FOV no matter how sure I was that it shouldn't have been. (2) Focusing was very critical and the exposure had to be long enough to ensure the planet would be bright enough to see.

The problem arises when the planet is out of the FOV and the focus and exposure are not quite right. It becomes necessary to perform a crude circular scan until the planet suddenly appears on the edge of the screen, BUT if the focus and exposure isn't right you won't see the planet even when it does appear on the edge of the screen. Catch 22 - you can only really set the exposure and focus when the planet is in the FOV!

I would have the problems when I had been imaging Jupiter and it would go behind a neighbour's tree. So I thought that Saturn would be easy - focus and exposure both right and Saturn clear as the nose on your face, but could I get Saturn?! Eventually I have done a few times, but I have also abandoned a few times out of complete frustration!

Not really sure if that helps, but it's sometimes useful to know that you're not alone! Attached is an eventual Saturn!

Yours aye DKNicholson

Edited October 18, 2019 by DKNicholson
word deleted

[Rusted]

I think we must share the same batch of Catch22.

What a splendid image of Saturn despite your trials and tribulations!

It seems I must try [very] much harder. 

Thanks for the useful advice.

[DKNicholson]

20 hours ago, Rusted said:

I think we must share the same batch of Catch22. - It seems I must try [very] much harder.    Just a thought. If the exposure time is too long, a small section of the rings may have appeared in the edge of the FOV for a moment while you're scanning for the planet, but you miss them because the camera is taking a frame. I'm sure you may have tried this but if not: increase the gain to maximium, if possible, and ensure you still have at least 10fps.  Also scan quite slowly and investigate any change in brightness by carefully adjusting the focus/exposure. I've had it where the planet is actually in the FOV but the focus and exposure have reduced it to just a very faint change to the brightness of the frames. Good luck! 🤩

What a splendid image of Saturn despite your trials and tribulations! Thank you kindly

Thanks for the useful advice. Hope it helps

 

Edited October 19, 2019 by DKNicholson

[Rusted]

Thanks. Every little helps when things completely defy logic and experience.

[Yawning Angel]

The last time I caught Saturn with the 120mc-s, I think it was sub 1sec exposures with maybe 50 gain . Getting it on chip is the hardest part by far. For ref, the below is one of the capture videos (tracking ended up pointing at a street light!) Celestron C8 with an ADC, as it was low low in the murk 😕

Keep the exposure length short, high gain and pan around methodically till you get on target, then you can tweak the settings

Good hunting!

[Rusted]

Thanks Alex.

You appear to have captured your very own occultation of Saturn by the Sun. 

Edited October 19, 2019 by Rusted