Another major factor is seeing. Where I am it rarely gets above 5/10. On average 4/10.
That severely narrows your chances of getting good shots, despite having the great equipment.
Correct, weather condition can severally effect the final out come but there is aways to limit this problem. If you look at the high end camera, such as the DMK and Lumenera, they have one thing in common - high frame rate eg 60fps. This increase the chance of capture more frames which are unaffected by the weather as appose to the 5 or 10fps you would get with a TuCam. For example I can collect up to 1600 frame in 90sec when imaging jupiter as appose to 450 to 900 frame with a webcam. If I take the top 10% of the 1600 frame I will have 160 I can use for my final image were as with the webcam you will only have 45 to 90 frame to play around with.
The final result, more frame that are collected which are unaffected by the weather, the better quality image.
Been doing some imaging with neximage at 20fps, what looks unexceptable at 5 and 10 fps is resonable at 20fps. The image even appears smoother at 20fps than 15. Cannot explain it.
30 and 15 fps always produce low quality images with neximage. People talk about compression and that 5 & 10 is all that can be used where commpression isn't a problem. But why is 20 fps performing so well?
Just say someone is a newbie with a stack of cash, you can not go out and buy a c14, lumenera camera and start producing damian peach images.
Technique is a major factor as with any hobby / sport / business etc.
When i got into astronomy July last year, I had in my mind to start with a DOB and then from there upgrade. I would still recommend for anyone that this is the path to follow ie cut your teeth on a dob, push it around, learnt to collimate, estimate seeing, cool it, work out imaging without tracking etc etc.
The next step after that is the hard one.
It is a multiple $1000 step. A BIG STEP and one i hope to make only once or twice over the next 15 years.
Is there a correct answer for everyone, of course not.
Bird with his reflector, damian and chris go with c11's and c14.
I have heard Mewlons are the best mirror setups of all for planetary and I only know of Rob_T's
It is a fantastic fast paced hooby, cutting edge! We only have the last 3 or 4 years of Damian Peach lifting the imaging bar and now a lot are catcing up. We becomes adept at studying the weather, image processing, electronics, programming for filter wheels.
lester, purely the seeing i would presume. Have you had a night of imaging in 8/10 or better?
There is always a trade off from number of frames for stacking and quality of frames.
In say 5/10 or 6/10 seeing. 10 or 15 or 20 fps will be great as you get more and more frames to try and get rid of the crap. Compression plays very little effect here, as you would never notice it!
BUT in 9/10 seeing, when you can capture 400 frames that are all great in their own right, then you want them to be as uncompressed as possible, hence 5 fps is best. There are no distortions to try and stack out! Each and every image in that avi is the same size
See the attachment, it is a converted jpeg from the avi. I had nearly 400 of these frames to work with. The moon stayed in focus nearly the whole time. So, the only thing i can improve here is making sure it is not compressed. Stacking 200 perfect frames compared to 2000 perfect frame will have very little difference. The only difference is the compression.
Damian Peach captures in barbados due to the seeing, Chris Go captures in the phillipines where he has 7/10 or better nearly every night. Very little processing is needed. Into registax, and a little wavelets and thats it.
So, you are spot on, 20fps works well, except if your seeing is great, then compression effects will come into play. You don't need 2000 frames if the seeing is great, even 100 frames will produce a great image. The DSO guys might take 5, 10 or maybe 20 frames and stack them and produce great results.
This is an image I did the other night. I had better one but due to dumd thumbs I accidentally deleted them from the HD. This is a stack of about 400 from a total of 1600.
the c9.25 and c14 are apparently ideal setups for planetary in terms or mirror setups, but not the c11.
I not sure I understand fully why?
I was just pondering the above question. If we say that all things are equal then there would be no difference between any of the SCT on the market. But if you look at the specs of the competing scopes you may see some interesting stats.
Just working with Secondary Mirror obstruction by area (could not find relevant info on obstruction by diameter to I will leave in out of the equation) you will notice there is quite a variation in centre obstructions.
If a smaller centre obstruction will give you better contrast then you can infer the following.
There is little difference between the C9.25” and the M10” and in the right hands should produce quality images if everything is equal e.g. collimation, camera, weather etc.
When it comes to the C11” verse the M12” it looks that the M12” would be the better choice for planetary imaging due to the smaller central obstruction.
And finally the big one, the C14” verse the M14” again the C14” is the better choice for planetary imaging again due to the smaller central obstruction.
So apart for the size of your bank account, if we go on the premise that a smaller centre obstruction will give you better contrast when imaging the planets then the C9.25”, M10” M12” or the C14” would be the scopes of choice. But remember technique makes up 90% of the imaging process.
Me may need to rethink my decision about my next scope for planetary imaging. Maybe a M12” or, yes you guessed it, a C14”.
I got a quote today for an aluminium tube that breaks down for transport. I think that I am yet to see convincing proof that the SCT's beat reflectors in the planetary game.
A c14 would be great, but $$ and a mount = more $$$. In the immediate future, I will follow the lead, get a better camera, new tube with integrated peltier cooling system and also bigger ALT bearings for more accurate tracking with the dob briver II
When i have lotsa money a titan and a c14 would be great!
very interesting. Don't know how much 2% greater obstruction would be noticeable when imaging.
Why hasn't some one perfected the un-obstructed reflector? Would have potential to perform as good as a refractor with extra diameter and not too long a tube if you use a folded reflector.
I'd say seeing is #1, then technique and processing
Hi Mike
I agree, understanding the weather is important, it is all part of the technique. But as you will find out with the DMK, as I have discussed earlier, the high frame rate can over come some of the blurring effect of the weather. So on night were you think it will be no good for the ToUcam due to its slow frame rate it will be ok for the DMK. The DMK is capable of imaging up to 60fps so there is a greater chance of capturing more image free of the blurring effect of the weather as apposed to the ToUcam which on average is 10fps. This mean instead of 100 frame you will have 300 of 400 frame usable for stacking and processing.
This is one of the reasons why people who are using these camera have great success.
Yes Paul I thought there would have to be some sought of unobstructed reflector kicking around. But they don't seem to have taken off. If they are as good as they should be in theory there would be more of them around.
A better average is derived from it.
This is a stack of about 400 from a total of 1600.
Maybe a M12” or, yes you guessed it, a C14”.
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