DSLR or IS DFK21AU04

[SkyExplorer]

Hi,

Can anyone let me know the difference between say a IS DFK 21AU04 CCD and a Canon 450D DSLR? I believe both can take long exposure photos and both I think can take video, and so act as web cams.

Thanks

[arad85]

For planetary:

DFK - uncompressed high frame rate video - no artefacts, great for planetary imaging. Small chip, so can be a challenge getting the object on chip, particularly at long focal lengths needed for planetary imaging.

450 - large chip so easier to get on chip, but uses compression in live mode. Less sensitive, so may have a problem catching finer details at higher frame rates needed for seeing through the seeing for planetary.

For DSO:

DFK - lack of sensor size is an issue to fit objects on chip. For example, in my C80ED the field of view is 20'x15' with the DMK21 wheras with the 450D it is 2x1.5 degrees

450 - beats anything below a large format dedicated CCD cam for almost anything and can be used as a day-to-day camera easily too.

HTH

[Space Bat]

Hi

The DSLR is much better for wider field DSO's - you can use the EOS ustility to remote control the camera and is fairly easy to use.

Planetry imaging at prime focus is not good and would require eypiece projection to increase the image size on what is a much larger sensor chip. Plus with different seeing conditions and varying degrees of illumination a planet can have, the camera just can't cope as well as the DFK interface for setting up.

The DFK is a great little camera and ideal for Lunar and planets - you can take much more control when imaging planets and using it with 2, 3, 4X barlows increases the image size to get better detail.

The CCD in the DFK is much smaller than the DSLR CMOS/CCD so taking wider extended DSO objects such as Orion nebula...etc it will only be able to see the core of the nebula and trapezium but not the full nebula this is a DSLR job.

I have had some success on the DFK with planetry nebula's as they are much smaller - however poor seeing has not left me much to play with.

Chris

[jgs001]

There is a place for both in the kit line up. The IS camera is excellent for planetary and lunar and makes a good quidecam for long exposure deep sky imaging. Which is where the SLR comes into it's own. I have the QHY5v in place of the IS camera (it's half price) and use the two just like that. I would like a small sensor camera like the IS for getting image scale on some DSO's... but cost is an issue at the moment.

[SkyExplorer]

Thanks for the quick replies.

I'd like to buy one or the other to start out on the imaging road, the dslr is better for DSO and the IS is better for planetary. Doh! It seems there is always a compromise with this hobby (unless you have deep pockets)

I only have a EQ 5 mount at present and an f5 scope, so bearing this in mind if you had the choice which one should I get? (possible a tough question I know)

Can I use a barlow with a dslr and what is eypiece projection ??

Thanks

[jgs001]

What do you want to image ?

Planetary, then the IS

Deep Sky, the dSLR

With that setup, widefield images with the dSLR is probably the better bet.

[arad85]

LOL. You may have focus issues with your newt (often the focuser can't get the camera close enough to focus - I can't in my f/5 dob) which might require a replacement focuser. I assume the mount is motorised? If not it will need to be for DSO. You will also need a method of attaching it to the scope (another £20 or so) plus a remote shutter release - another £30 from ebay (unless you've got a laptop to use instead). Don't forget you'll need to power the laptop in some way too...

Also, if you get hooked, expect to be lusting after a HEQ5/EQ6 fairly soon. DSO astrophotography is all about the mount...

[glowjet]

Have a look at the : 12Dstring Field of view calculator, it will give you some idea what can be achieved with both cameras,

John.

[riklaunim]

With DMK, DFK, DBK 21 (or other webcam, or 1/4" CCD cam) you can get small FOV, and as it's 8 bit camer - you won't get many colors as with 16 bit deep space CCDs (DSLR is probably 12 or 16 bit, depends on camera...). Also DSLR photography of DS objects requires longer exposures - better mount, tracking, and probably guiding

So you can get both - D*K21 for lunary, planetary, and DSLR or 16-bit astro CCD for DS, wide field photography.

In my 150/750 newtonian and DMK21 only the trapezium of M42 gets in the FOV:

RGB, lazy stacking of color channels

Or max size without cropping:

[SkyExplorer]

I'm already looking at the HEQ5 !

The scope I have is skywatcher Explorer 200P at f5 and an unmotorised EQ5 mount - Don't laugh!

I'd like to have a go at taking images of both planets and DSO, although as my mount is unmotorised it seems DSO images will not be possible.

Would I not attach the dslr to the thread on the barlow ? If I have a problem with f5 scope focusing with dslr will I have this with IS camera as well? If so how could I fix this?

[riklaunim]

- You need at least REQ motor drive, even for short exposures.

- 8" big newtonian is hard to keep steady and to guide it - so it won't be easy

- for lunary and planetary imaging you need a fast CCD camera like those from imaging source. You record an avi and then stack it. For planetary imaging you need a good barlow. The greater - the better seeing you need (and motorized mount). For my 150/750 newtonian 4x barlow is optimum-max. This astrophotography is cheap as very short exposures doesn't require super steady tracking etc.

- for darker deep sky objects you need very good mount (motorized) and guiding (if you take 10 min exposure then for that 10 mins the target may not move.) This is very expensive astrophotography

[jgs001]

I'm not sure, but I think that scope would be borderline on an HEQ5 for deep sky imaging. I'm afraid I can't help/comment on the possible focus issues, I've never used a reflector.

[SkyExplorer]

I guess what I initially was trying to find out is thus:

As the IS DFK is almost the same cost as a DSLR (which I can also use to take daytime photos with) would a DSLR be as good as a IS camera at taking images of planets dso's?

From what I am reading it depends on what I want to view and the scope I have. It seems with my scope that I may have focusing problems (if I understood that bit correctly)?

I was looking at Orion last night and could see the trapzium and excellent structure to the nebula around it (it had a greenish tint) and looked almost 3d. I was wondering if taking a photo of what the "eye" sees (the grey nebula) is possible and if so how as this could be a cheaper way of taking DSO images to start with - Or am I barking up the wrong tree ?

[riklaunim]

DSLR like old Canons are cheap because they are old and mass produced. They have CMOS sensors that have lesser sensitivity than CCD sensors in astronomy cameras - so it's cheap, but needs longer exposure times etc.

For lunary and planetary imaging big sensors, DSLR aren't that good as you need some frames to stack and get much better image. Small cams like IS can get 30-60 frames per second so it's take a short avi to get few hundred of them. DSLR can't do that, and fast rotating planets like Jupiter have to be imaged fast before the details rotate.

If you want to make images of nebulas then you have to have motorised mount, polar aligned. You connect DSLR through T2 threads, and you should get also Baader coma corrector (or maybe the SkyWatcher one). As for focusing - check at day on distant object. In my Newtonian DMK21 has focus lower than eyepieces. Barlows will move the focus point up (good for planetary/lunary imaging with filter wheels, flip mirrors etc.)

[brianb]

Also note that running frame counts into the thousands gobbles up space by the bucketload with a "low res" camera, with a DSLR even terabyte drives would look insignificant. The much smaller weight helps the stability of the mount when imaging, too.

[resonator77]

I noticed that folks above forgot to mention Celestron CG-5 GT. It is a great all round for planetary and DSO mount and it is cheaper!!!

[SkyExplorer]

Thanks for all the replies.

It sounds like the IS camera is good starting point for imaging planets and even Orion to some degree (looked at the photos on your site riklanium using the DMK 21 - Very good!).

[riklaunim]

~no noise, and uncompressed AVI capture by IC.Capture.AS is very good starting point. Mono (DMK) is in some way better than color cams - as you can use various filter to get better results (and RGB filters to get the color image). It's 8-bit so it won't give super detailed nebulae, but still, very good at start (and may work as a guide cam later)

[MishMich]

You can image planets with a DSLR, and while not as good as a dedicated planetary imager, they will be as good as a webcam or guider equivalent (such as the QHY5). When capturing the video stream, at x5 magnification in live view, the size of the image will be much the same, and the size of the resulting AVI will be little different from a webcam - appx 720px. This way you only use part of the sensor, not the whole sensor.

I have images of Saturn & Mars, with x5 magnification on liveview, and x5 barlow, through an 8" reflector. This is the 'brightest' image with that magnification, but a x2 or x3 barlow would be brighter, if smaller.

Stargazers Lounge - MishMich's Album: imaging - Picture

Stargazers Lounge - MishMich's Album: imaging - Picture

I would go for the DSLR, see how you get on with it, try out both types of imaging with it, see which you enjoy doing, how far you get, then when you are ready to move on, decide whether to upgrade to a planetary or dedicated DS imager.

Alternatively, you could get a webcam and an EOS1000D, and see how you get on with them.

M.

[arad85]

I noticed that folks above forgot to mention Celestron CG-5 GT. It is a great all round for planetary and DSO mount and it is cheaper!!!

Hmm... not with an 8" newtonian on it wouldn't. Perhaps with a small refractor but I soon realised it would be a wasted effort to get it working well enough for my tastes, so swapped it for an EQ6 (plus EQMOD s/w is so much better than anything for the CG5).

[SkyExplorer]

The pictures are very good!

Is that the f6 scope you have listed?

Did you need anything extra to help focusing?

[riklaunim]

I use SkyWatcher motofocus for focusing for DMK camera and on high magifications

[Whippy]

Another alternative for planetary would be to use a DSLR for eyepiece projection imaging. What this entails is attaching the camera to an eyepiece in some way which negates the need for a barlow. The Baader Hyperion range of eyepieces has threads at the top and with the right adapters make a sturdy connection.

Tony..

[MishMich]

Sorry, it was in the post that got truncated. That is with the f/6 8" SPX & x5 barlow. However, what you need to watch out for is whether you can achieve focus with the SW 8" - as somebody said earlier. My SPX is set up in a way that I can achieve prime focus as is, but in order to use an eyepiece, I have to insert a 2" extension to achieve focus. This is the same with a web-cam or CCD-camera (or the QHY5). With a barlow, I need an extension for the DSLR as well. So, with the SW, my guess is you may be able to use the DSLR with a barlow (or EP projection), or a CCD cam or web cam - but there could be problems with the DSLR for DSOs. However, the SPX, I am told, can be adjusted for either - by moving the primary mirror (there seems to be a fair bit of scope for movement when I collimated the other day) . Whether it is possible to move the primary mirror of the SW in order to allow you to achieve prime focus I have no idea, but it could be worth checking out before buying a particular type of camera, especially if you can avoid having to replace the focuser in order to use a DSLR. I have never had a SW reflector, so can't help beyond that - perhaps somebody else knows whether it is possible to move the primary mirror enough to achieve prime focus, and how you go about that.

M.

[SkyExplorer]

So if I understand everything correctly I may have a problem trying to get the image in focus using both the dslr and the IS camera with my scope?

What about if I were to get something like this http://firstlightoptics.com/proddetail.php?prod=st102ota or this http://firstlightoptics.com/proddetail.php?prod=ev102eq32 (without mount) and mount it on my EQ5 mount. Would this be a better bet than my reflector?