ADC not an unqualified success

[Davey-T]

Tried the newly acquired ZWO ADC tonight, using 2 X Powermate 10"SCT, the actual setting up of the ADC went OK, had to use 32mm plossl to get Jupiter in the frame then swop to camera which is where it all went Pete Tong.

Moon out and skies quite cloudy.

By this time Jupiter had gone too far west so switched to Saturn, tried imaging using Firecapture and PGBfly which goes along at 30fps plus when imaging the Sun using full frame  it but couldn't even manage 10fps with ROI but a decent enough image on screen, then tried ZWOASI178 which just about managed 30fps using ROI big enough for Saturn but was only able to get a really dim image on screen.

Any thoughts, should I invest in a more suitable camera for planets or am I missing something obvious ?

Dave

Edited July 19, 2019 by Davey-T

[Ibbo!]

My thoughts

a ) Seeing was not good here tonight -C11 no powermate

b)  What gain was you using - I tend to use 70% ish on the planets and a low gain on sun and moon

c) it got a bit chilly for shorts and t shirt

[chiltonstar]

With Saturn down at murky near-horizon levels, I found I got a better image a few nights ago taking out the 1.5x Barlow I normally use*, imaging at 30 fps with my AS1224. This is therefore at about f15 (probably more like f20 because of the flip mirror and connections), the actual f ratio of the 180 Mak.

With more aperture, I would have thought you would have a brighter image than I was managing?

Chris

* Barlowed, I could barely manage 15 fps at near max gain.

Edited July 19, 2019 by chiltonstar

[Davey-T]

7 hours ago, Ibbo! said:

Seeing was not good here tonight -C11 no powermate

 

1 hour ago, chiltonstar said:

Barlowed, I could barely manage 15 fps at near max gain.

Perhaps it was just the very poor conditions, the Moon was a fuzzy in the cloud, couldn't figure out why the image in the B'Fly was so much brighter than the ZWO178 though ?

Didn't make a note of the gain will have a look at one of the vid's.

Dave

Edited July 19, 2019 by Davey-T

[Cosmic Geoff]

Were you using full frame? I crop to 320x240 for planets which vastly increases the frame rate. No need to record a lot of black sky.  Frame rate on Saturn can be slow especially if there is excess extinction.  Last session I got something like 60 fps IIRC with an ASI224MC and 8" SCT in clear conditions.

[Davey-T]

1 hour ago, Cosmic Geoff said:

Were you using full frame? I crop to 320x240 for planets which vastly increases the frame rate. No need to record a lot of black sky.  Frame rate on Saturn can be slow especially if there is excess extinction.  Last session I got something like 60 fps IIRC with an ASI224MC and 8" SCT in clear conditions.

Yes, using ROI just big enough for the planets, didn't make it run any faster, considering getting a more suitable camera if results aren't better with a clearer sky.

I see you're using a colour camera, what are the pros and cons of using colour versus mono ? I've got a filter wheel with a set of Baader LRGB filters in, was just using the L last night for testing

Dave

[Cosmic Geoff]

4 minutes ago, Davey-T said:

I see you're using a colour camera, what are the pros and cons of using colour versus mono ? I've got a filter wheel with a set of Baader LRGB filters in, was just using the L last night for testing

The colour camera gives a good enough image with far less work. I don't want to be bothered with filter wheels, 3x exposures and extra processing work. 

[Davey-T]

2 minutes ago, Cosmic Geoff said:

The colour camera gives a good enough image with far less work. I don't want to be bothered with filter wheels, 3x exposures and extra processing work. 

Can the colour camera be binned ? working out the figures for my setup with the ASI224 various combinations barlowed , unbarlowed ,binned, unbinned gives resolutions over / under the Dawes limit, does this matter as much for planetary ?

Dave

[Cosmic Geoff]

I think that the seeing is the dominating factor. If you look at my recent posts where I include an unprocessed frame you can see that the typical blur was just awful and I suspect will swamp the effect of binning and barlows.

[Davey-T]

Back to the old reliable trial and error method then 

Dave

[JamesF]

Odd that the frame rate should be so low when you're using ROI.  Makes me wonder if there's something else going on, like it's only running at USB2 speeds or something.

James

[Davey-T]

7 minutes ago, JamesF said:

Odd that the frame rate should be so low when you're using ROI.  Makes me wonder if there's something else going on, like it's only running at USB2 speeds or something.

James

Using the same MBP as for solar when both cameras run OK, the Black Fly is GIPO.

Dave

Edited July 19, 2019 by Davey-T

[Freddie]

If you were limited by the exposure you had to set to get Saturn bright enough (which you probably were with it being low, having a Barlow and using the ADC) then changing the ROI will have no impact on your frame rate.

[Davey-T]

7 minutes ago, Freddie said:

If you were limited by the exposure you had to set to get Saturn bright enough (which you probably were with it being low, having a Barlow and using the ADC) then changing the ROI will have no impact on your frame rate.

Thought it might just have been the very poor conditions cloud and Moon.

Dave

[symmetal]

Remember your maximum FPS achieveable is limited by the reciprocal of the exposure. At 5mS exposure it's 1/0.005 = 200fps. At 20mS it's 50fps, while at 100ms it's 10fps.

As you can achieve 30fps full frame on the Sun then exposure was your only limiting factor on the planets, and as Freddie said a smaller ROI would have no effect.

Use a higher gain setting to allow a shorter exposure and so achieve a higher frame rate. I've found you can use very high gain settings where the preview looks all noise, but stack enough frames and it 'magically' disappears.  A shorter exposure will also give a sharper image if the seeing is poor, as well as higher fps, so enabling more frames to be attained for the same vido duration, which when stacked will mitigate the extra noise introduced by gain.

Alan

Edited July 21, 2019 by symmetal

[Pete Presland]

Absolutely true regarding the gain. I have imaged Uranus with so much noise that can barely make the planet out! When stacked the noise is virtually gone, if you stack enough frames.