Thinking of dragon fly.

[Slawomir (Suavi)]

I'm not quite sure whether it is worth the effort, for me anyway. Cheap lenses, cheap cameras, perhaps cheap focusers eventually adding up to a substantial amount of $$$, but quite likely allowing to quickly capture only substandard data anyway. What's the point of having a high SNR when quality of data suffers

Why not spend the same $$$ on a quality less complex rig that one enjoys using? And who cares if images are a bit noisy, if stars are pinpoint to the corners? Just my five cents.

[lazjen (Chris)]

The "real"way to win is to do both - lots of expensive scopes, expensive cameras, filters, focusers, etc and make that into a Dragonfly setup. :p

[xelasnave]

I see some images that have 50 hours or more.

Would there be any benefit in being able to capture ten times that?

Would say five hundred hours of data be exciting or over kill?
Alex

[JA]

Originally Posted by xelasnave

I see some images that have 50 hours or more.

Would there be any benefit in being able to capture ten times that?

Would say five hundred hours of data be exciting or over kill?
Alex

Hi Alex,

I think that all else being equal, provided that the sub-exposures that make up your 50 or 500 hours are adequately exposed (not too underexposed/read noise limited or too overexposed as to blow out highlight detail) , then yes there is a benefit in the signal to noise ratio of the image, which if the data is randomly distributed should be around (up to) the square root of 10 = 3.16 times less noisy in the 500 hour compared to 50 hour images, processing not withstanding. How obvious that difference is, is another story and will depend on the starting point. How good is original 50 hour image reference? Was it taken with top end gear and therefore more likely to be high contrast/fine detailed/less noisy or was it taken with lower end gear such as webcams with "lesser" lenses.

To take your example, one might find the signal to noise ratio with top end equipment at 50 hours of total exposure already "entirely acceptable" and although 10 times the exposure duration would provide an improvement the improvement might be judged as potentially not worth the time for the incremental improvement (may have to occur over a few years of data collection depending on weather/conditions), whereas on lower end gear such as webcams/etc the improvement in signal to noise ratio will be more evident because of a lower starting point of the attendant 50 hour image.

That is not to say that quality images can't be achieved with certain gear, just that the higher you start, the better you'll be in terms of overall image quality with or without the 10 times exposure increase you proposed.

I think the Dragonfly telescope is a wonderful concept, that within certain parameters and in certain applications can and has been shown to outperform many of of the big boys. It's also the sort of project that really interests me.

Best
JA

[Atmos (Colin)]

There is more that needs to be considered that absolute imaging time. When you start getting into incredibly deep stacks - say 100+ hours - your limit can come down to how good you are with your calibration frames. If you don't have absolutely perfect calibration frames, I mean exceptional, the difference between 100 hours and 500 hours may be how hard you can stretch Fixed Pattern Noise.

[xelasnave]

Originally Posted by Atmos

There is more that needs to be considered that absolute imaging time. When you start getting into incredibly deep stacks - say 100+ hours - your limit can come down to how good you are with your calibration frames. If you don't have absolutely perfect calibration frames, I mean exceptional, the difference between 100 hours and 500 hours may be how hard you can stretch Fixed Pattern Noise.

I like it when we identify specific issues.
How do we overcome this problem.

Well if nothing else for my part having a one hour window has me grasping at straws.

But realistically $5000 a unit, say... gets expensive each addition hour...from a quality point of view I would be happy if such a unit did as good a job as a normal rig... as I said it has dawned on me just how little observing time you get...but set up in a van and going to somewhere to image half the night a month or two each object you take on...say 8 hours a night times ten...each week...month even given filter requirements mean some stuff could be done even full moon..I think not sure...but say 100 days imaging at 80 hours a night...thats 8000 hours... how would you manage that??? could , assuming good what could you do..Hubble Deep space shots eat your heart out???

I could go four maybe but thats still $20,000...no wont happen.
I would still like to have a go at building one out of binos...I found out today focusers are cheaper than I thought..

Alex

[Slawomir (Suavi)]

Maybe it would be worthwhile starting with a dual set up and perhaps after making it work reliably one could add more lenses?

[xelasnave]

Originally Posted by Slawomir

Maybe it would be worthwhile starting with a dual set up and perhaps after making it work reliably one could add more lenses?

Yes ..now thats the go.
You set up two. Get them working.
Add another two... managable instalements and each stage would hint at the problems of the next stage.

A coulpe of binos held on the mount with duct tape and old suingle shot 30 second exposure also held on with duct tape..

Must look on the net and see if anyone out there is building one..you would think soeone will be.

Alex

[Atmos (Colin)]

I currently have the components to attach 3 DSLR to a mount at once. Overall cost of that was about $500 (bought the stuff a while back) but it is purely for DSLRs.
If you want to do really deep stacks, you cannot do it with a standard DSLR. You need to be able to precisely match temperatures with your images and darks otherwise the mismatch in thermal noise because your limiting stack depth.

Your flats should have 100+ and be 50% of saturation. Each camera will need its own set of Darks, Flat Darks and Flats. The more of everything the better! Remember, image calibration actually ADDS noise to your images but stacking allows you to average the left over random noise out.

[xelasnave]

well I was thinking of just an approach to taking darks and bias and lights one after the other to try and average temp variations...not with this in mind but a system of imaging ...sorting would be a pain..well if it worked I am not sur ehow stacking programs work ... I dont know but what a challenge.
Actually just buy very old cheap dslr with a kit lens but a few new nikons..I expect the lens is probably ordinary but something like that you get remote focus.....use as a proto type to sort out everything...Anyways one rig at a time. You could mount them on a bar without much trouble..a none zoom lens other wise maybe issues...Alex

[xelasnave]

All of a sudden even with dslr group the vision of cables everywhere..does a usb to your camera power it or does it still use the internal battery..I have not noticed..
Its like the guy who built the 48 cylinder motor bike..imagine the problems to sort that thing out..
but you still cant ride it.
I wonder once everyone has their dragon fly system and its reached that level of intensity...could we say link 10 different folk each with an array of 10 and gulp in 100 hours every hour...if you process more data can you still get more because you have so much data.
I forgot there is someone trying to sell units..that was on this forum a while back..I wonder what they claim and offer and charge...and if anyone is using them and to what degree.
Alex

[Atmos (Colin)]

The DSLR still runs off of the internal battery. Depending on how you do it you could possibly get away without needing all of them USB connected; just use a shutter release.

[xelasnave]

Originally Posted by Atmos

The DSLR still runs off of the internal battery. Depending on how you do it you could possibly get away without needing all of them USB connected; just use a shutter release.

Internal batteries would be a blessing saving a lot of cables.
Cord less remotes also. Just buttons to press.

alex

[JA]

Originally Posted by xelasnave

Internal batteries would be a blessing saving a lot of cables.
Cord less remotes also. Just buttons to press.

alex

Hi Alex,

They also may be a curse.... as Lithium Ion batteries will give of some heat, certainly during charge, but also during discharge (use) which in the extreme, say with long runs, lots of images, lots of screen or live view or video use might heat the image sensor slightly and thereby increase noise in the image.

It's something which would be good to quantify by experiment... Image noise, say taking a dark (image) using the internal camera battery versus using a plug in external power adapter to the camera. To really test it, the battery should remain in use for a while and to be fair the external power soucre as well.

BUT The above is only really relevant for a DSLR or a device with internal batteries, not with USB powered webcams or astrocams that were discussed earlier in the thread

Best
JA