2nd attempt at Saturn

[edwardsdj]

Hi all,

Second attempt at Saturn. Thanks heaps to Matt and Jeanette for the advice :)

Conditions were much better last night and I was able to capture a LOT of data.

Anyway, here is my preliminary processed image. The first image is processed in Registax only. Second image is a good raw frame.

Paying careful attetion to the exposure during capture (as Matt suggested) worked a treat. I tried to keep it around 200 by adjusting the gain while keeping the exposure long. Decreased the frame rate to 15fps and used the automatic white balance (all as suggested by Matt).

Thanks to Jeanette, I went the 2x enlargement during frame alignment in Registax. I assume this is better than doing it at the end.

I realise this preliminary image is probably overprocessed, but I'm learning and have enough data to keep me busy for a while developing processing techniques now.

Thanks again for your help guys. Any comments, criticism, reprocessing most welcome. I'm trying to get better at this.

Celestron C8 with 2x Ultima barlow for 4000mm focal length;
Philips SPC900NC webcam at 15fps;
Stacked about 600 of 1000 frame in Registax;
Slight wavelet processing in Registax;
Slight final processing in Registax.

I'm thrilled at the detail captured in this image :D

Have fun,
Doug

[matt]

A great improvement, Doug.

Just a small point. In my reply I actually recommended not going any higer than 10fps:)

I think 15fps produces noticeable compression. Bring it down and you should see even more improvement.:thumbsup:

[edwardsdj]

Hi Matt,

I did try my best to take your advice. I started with 5fps and then 10fps but the seeing wouldn't support it. K3CCDTools kept dropping about 2/3 of the frames during capture and they all looked like the planet was swimming too much during each exposure :(

I tried to get the lowest frame rate I could which was 15fps. In hindsight, I should have tried 5fps again towards the end when Saturn was much higher and the ambient temperature dropped to around 23 degrees around 2:00am. My final two or three AVIs show very little disturbance of the image as the seeing and altitude were improving all the time.

Thanks for re-emphasising the importance of the low frame rate. Next time I'll try to keep pushing the frame rate down as the planet gets higher and the seeing improves.

I'm thinking of sticking with my current focusing system for the moment. I'll try to get the most out of my current equipment before buying more stuff. I might even attempt an image with the Lightbridge 12". Will be VERY hard on Dobsonian mount with no tracking but I'm keen to see if I can get some sort of result.

I did try to image Mars using a red Baader planetary filter. I could see some detail but the seeing was too bad in that part of the sky for me to get much of a result. I might leave Mars for the next opposition and focus on Saturn in preparation for Jupiter :)

Thanks again for looking and pointing out that I should drop the frame rate further.

Have fun,
Doug

[matt]

Not sure what's going on there?:shrug:

I would have thought you could still use 10fps, use 1/25th or 1/33 sec and just push the gain a bit more???

It's been a while since I did a run at Saturn using a ToUcam;)

[edwardsdj]

It's so unfortunate that the interface to the SPC900NC just uses sliders instead of providing nice figures like 1/25s :(

I'll have another try at reducing the exposure time with the low frame rate next. It's like the whole meaning of the exposure slider changes with the frame rate :(

I can't thank you enough for your help :)

[matt]

You can download a small app which gives you a numeric readout of your sliders's values.

I've forgotten it's name but someone will jump in and help out shortly.

I can tell you that the furthest left on the fps slider is 1/25...the next stop in is 1/33.

[edwardsdj]

I'd love to get the app.

I'll pay even more attention to the frame rate and exposure settings next time. I kept the exposure slider all the way to the left at all times. When I adjusted the frame rate, the slider would automatically move and I had to keep pushing it back to the left.

As I recall, the low frame rates where producing a brighter image so I had to back off the gain. These images were blury compared to higher frame rates. This is only my recollection and I will watch what happens more closely next time so I can give a proper description.

I should be able to adjust frame rate, exposure and gain independently as you suggest. I'm sure I'll soon figure out what I'm doing wrong.

Thanks again for your help :)