Jupiter through the 20" scope

Dave Lillis · Post by **Dave Lillis** » Sat Dec 08, 2012 3:23 pm

Hi all,
I recently installed a new fan and thermometers on my 20" scopes primary mirror, to get it cooled faster. I managed to get it down to 1.4 Celsius above ambient (I didn't want to push it any further down incase it dewed over), so I tried out some imaging of Jupiter to see what I could get.
So this is 700 images stacked out of a sequence of 3500. click image to see proper size

http://farm9.staticflickr.com/8215/8294 ... 3a45_b.jpg
I reduced the image scale abit to take out some of the graininess and added a bigger black surround.
The seeing was average, with moment go good steadiness, so I was able to use a 7mm (357x) and 5mm (500x) eyepieces at times. At 500, the moons were clearly tiny disks and had some colour. The eyepiece view was pretty much as you see it here, except not as colorful.
The higher altitude of Jupiter as seen from here compared to previous years has made a big differance. !!

Frank Ryan · Post by **Frank Ryan** » Sun Dec 09, 2012 3:21 pm

Wow.
That's cool!
It's Sooo bright!
It's a brilliant start Dave.
When the seeing is right your gonna get some
Jawdropping images!
More more more!!!

Simon Kenny · Post by **Simon Kenny** » Sun Dec 09, 2012 4:22 pm

Brilliant Dave. Tks for the tech details.
Simon

Dave Lillis · Post by **Dave Lillis** » Tue Dec 11, 2012 2:49 pm

thanks guys, I was surprised at how it came out tbh,
I took some images of Jupiter last year at the burren, same setup and was getting some really bad onion ringing on the disk edge, figured out that there was a setting in the capture program to enhance detail which was causing it, that's off permanently now.
The seeing was average, but it was the cooling of the primary that made a huge difference compared to earlier on in the evening...
I have the cooler fan held in a suspension type system so it now causes zero vibration when on, you wouldn't know it is on when looking through the eyepiece.

I'm pondering putting together a proper fully automatic cooling/heating system on the primary, one which monitors ambient and keeps the mirror from getting too cold or warm, its not technically difficult, cooling a mirror is easy, heating it without distortion is a different story.

Frank Ryan · Post by **Frank Ryan** » Wed Dec 12, 2012 11:44 pm

Sounds cool if you pardon the pun.
The new fan setup sounds like it's working great.
The heating as you say is a different matter.
I assume it needs to be uniform across the disk of the mirror.
That's gonna be tough.
There are a few ideas I have though.
What exactly would be required in terms of heating?

Dave Lillis · Post by **Dave Lillis** » Mon Dec 17, 2012 8:30 pm

oops, meant to reply earlier, the heating would be by 2x 6 or 8 inch heater pads from scopestuff, anything bigger and they would block the fans cooling action, I have a simple circuit that will monitor the primary mirrors temperature and ambient air temperature and will turn on the heat if the mirror falls within 1 degree of ambient (off at 2 degrees) and turn on the fans if the mirror is above 2 degrees of ambient,
The 1 and 2 degree values are completely configurable.

The entire point is to keep the mirror between 1 and 2 degrees above ambient. This should prevent dew-ing while eliminate thermals.

What I'm debating in my head is the effort required to put this together worth it, maybe a job for early next year.

Dave Lillis · Post by **Dave Lillis** » Sat Dec 22, 2012 9:53 am

got around to processing a second avi from that night, this one is at 22.57, that 39 minutes before the image in the first post.

its abit more colorful, to me it looks a little better, but not as sharp as I want yet though. I think its time to research a better camera,
Its interesting to see how much the planet rotates in 39 minutes !!

Frank Ryan · Post by **Frank Ryan** » Mon Dec 31, 2012 2:07 am

Dude with a DMK you'd get awesome shots!!
How much is a 2nd hand one?
Weren't we gonna pay money for some kind of cam for the club?
Why not take a look at what's out there?

Dave Lillis · Post by **Dave Lillis** » Mon Dec 31, 2012 11:50 am

yea, totally agree, a dmk camera would be a killer combination with this scope on a good night,

I do remember the committee had discussed a camera 2-3 years ago, the committee has changed alot since then, don't think it would be on the cards now and funds aren't there for it anyway,,,
Never heard of a second hand one on any market, I think if someone gets one of these, they tend to hang onto it.,