Had another go at Jupiter this morning, results were ok but the seeing conditions weren't that great. Lots of moisture in the air and heavy dew on everything..
I'm very jealous of the seeing conditions at your place Mr Bird.
I have only once, and for a very brief period, had seeing to allow me to view the kind of detail visually that you seem to capture routinely with your camera.
How do you do this. Even your supposed bad shots are simply brilliant. Tell me what sort of scope do you have? I was going to post one of my shots and I think that now I won't. You can even see Io on the eastern limb.
Trust me, it's a testament to the power of image processing... :-)
I did check visually, and it was possible to see a lot of this detail through the eyepiece at 200x, but it was all a lot smaller than the view through the laptop.
I have a "closed tube" system, and I think it allows a stable column of air to settle around the mirror. The tube is closed behind the mirror by the peltier cooling setup. The downside to this approach is that I depend completely on active cooling to drive the heat out of the mirror, as there is no natural convection.
I think it's a good system, but it's very different to the conventional wisdom of "openness" around the mirror for cooling. The conventional approach does not work in Canberra because there is just too much temperature difference between day and night - air cooling can't keep up.
I have a system of 4 sensors that measure the temperature (2 on the mirror, 1 on the metal of the tube, and 1 in the outside air) and my laptop can switch the peltier cooling on and off as needed to keep the mirror at the same temperature as the outside air.
Have I mentioned how much I like aluminium for tube material? It just tracks ambient air temperature very closely, much better than other metals or white painted tubes which will "supercool" several degrees below ambient.
Originally posted by Starkler I'm very jealous of the seeing conditions at your place Mr Bird.
I have only once, and for a very brief period, had seeing to allow me to view the kind of detail visually that you seem to capture routinely with your camera.
Another ripper Bird, well done. I have seen views like this, but not often. You obviously are getting some good seeing. I have been up to try a few times, but returned to bed after a look through the eyepiece.
Keep it up.
Gary
I echo Gary's comments... Congrats on a fantastic image Bird.
I wish the seeing here would settle. I like Gary have been up at the wee small hours only to return to bed after a quick seeing check on Jupiter. I have all but given up on Saturn. It's just too low!
Thanks Bird for the info, your system is similar to the SCT that I have, except i have my scope permanently outside under three tarps, and I dont have fans for cooling, but do have a closed system and aluminum casing. I think that either my collimation is out (possible) or the seeing is bad ( most likely during summer) or my barlow lens a 2x teleconverter is not aprochromatic. I can't nut it out, On nights when the image is nice and crisp through the EP and barlow I still cannot get shots totally focused, they have a blue cast at one end and a red cast at the other end of the image. I have to do way to much wavelet adjustments to get a reasonble image, which means it looks over processed. Although I must say, that when the air is cold, the imaging does get better. How do I conquer this problem. Aside from patience.
Sorry for the whinging, but getting up early to image and then having this happen time and time again, makes me testy. And I want to break through that final barrier to getting images I can really be proud of.
Paul, no problems about asking questions... lets see if we can figure it out...
I also see the 3 colours coming out of alignment - when I do the final recombine to make a colour image I have to shift G and B to line up with R. I think it is a combination of atmospheric effects (selective refraction at different wavelengths) and a non-perfect barlow and optics.
Green is the worst, I normally have to shift it like 5 pixels. Some of this shift may also be introduced by my colour wheel...
Something you might try is to split your colour images apart into separate RGB sets and process them seperately, then recombine at the end. Unfortunately you'll still have the lower resolution issue of the colour camera but maybe you can get the colour planes lined up.
You can use virtualdub to save your images as BMP's, and then something like pbmtools or imagemagick to split each frame into its components.
Not sure what time you're imaging, but I'd suggest on Jupiter to try between 4 and 5.30am, that's when I get the best seeing so maybe it'll be the same for you, and also Jupiter is highest.
Next time you're in Canberra, bring your scope along...
Another question for you Paul, what sort of temperature differences do you get between day and night? If it's a big difference, like 15 degrees, then you might find that your mirror will not be able to cool fast enough.
Thanks Anthony for the advice, now for the answers.
Its good to know that everyone seems to get the colour cast shifting. Might try the splitting into separate colours, sounds like a great idea, and worth the experiment. I already do the RGB shift in wavelets and then adjust as I go so that I get the best picture I can.
Now as for temp difference, last night it was 21 degrees and during the day 38, so perhaps you are right, that I need to do a mod to install a cooling system into the back of the telescope (yikes anyone know how to do this with a $6k telescope?).
As for imaging, I have taken your advice and been imaging at 4- 4:30 am. Unfortunately, this cannot last for long, as my neighbour has a lovely gum tree which is now getting in the way. So I will have to be content with earlier and earlier times so that I can image. I have a very limited field of view.
Finally, I might just take you up on that offer of a visit to Canberra, so that I can see how the master works.
17 degree temperature change... Well I'm guessing that you're suffering from local seeing - you should be able to tell if the mirror is too hot by pointing at a star and defocussing the image. Look for rotating spikes around the edge of the defocussed star. Thats a sure indication of warm air spilling off the side of the mirror. Not sure if that applies to a closed tube SCT though...hmm.
Before I built this peltier cooler I could see that happening all night long. Set up at 8pm, still getting those heat spikes at 3am. Pack up in disgust.
I've seen a "SCT cooler" that was a dongle that you poke up the inside through the eyepiece hole. It has a fan to circulate air. Now I'm thinking that you could bolt a peltier cooler onto it and make it push cooler air into the scope.
Yeah, I am definitely getting rotating spikes. Maybe that is really the problem. Either I make a mod or get the new RCX400 (what a joke). So it looks like I am doing some mods. Need to do some research. Thanks for the help.
Actually a peltier cooler for your scope is easy, now that I think about it.
Imagine something that screws onto the SCT thread at the back of the scope, made out of solid aluminium and extending about 10cm or so inside the scope. Enough to clear through teh hole in the mirror and extend a short distance into the body of the scope.
Bolt a peltier cooler onto the part that's sticking out the end and you can cool that lump of metal so that it pulls heat out from inside the scope. This is more-or-less exactly what my prototype cooler is doing.
I see that Jaycar are selling peltier units very cheap - I bought marlow brand at about $70 each, Jaycar have some other brand for about $20. I use a PC power supply to run the cooler - it chews a lot of amps @ 12v.
An interim solution is to store the scope somewhere that's cool - ideally at about 20 degrees (or whatever the overnight minimum will be) so that the scope is already at temperature when you take it outside.
Thought you might like to see this - it's a temp graph I took last year, and it shows how my mirror (red line) never catches up to the ambient temperature (purple). The tube temp is also shown in green.
The mirror was cooled by two computer fans going flat-out, and it still wasn't enough. After I saw this graph I knew that a peltier was on the drawing board.
The graph has a nasty spike caused when I went out and accidentally put my hand on the sensor, but I couldnt be bothered editing it out :-)
