Ask your fellow astronomers to solve your telescope queries
Sat Dec 10, 2005 11:50 am
I have been thinking about moving on to a Starlightexpress, possibly the SXV M8 C although I still need to educate my self in these things. I was sticking to CCD technology because I always hear that digital SLRs can't handle long exposures with out creating loads of noise. Now I have just found this [url=http://www.telescopehouse.co.uk/page.aspx?theLang=001lngdef&pointerid=EB9D79522B8F448487078A871B0B3B98&action=lnk][b]Canon 20DA astro digital SLR[/b][/url]. What do you think of this? How would it compare to the SXV M8 C?
I currently use a Meade DSI, but I want more resolution and better image quality. My scope is an LX90 8" SCT. Although the Canon is much more expensive than the Starlightexpress, it would be more useful as it is a good camera which I can use for general photography too, but my main aim is to get good astro images. I'm just not sure that the Canon's CMOS would be able to cope with the long exposure times. I have also never used an SLR for astro imaging before so am not sure how different the techniques will be. Can you still use a CCD autoguider when imaging with an SLR?
Sun Dec 11, 2005 1:10 am
Hi Al - that's a very pertinent question these days. DSLR's are coming on in leaps and bounds , the 20DA being the latest. The trade-off with DSLR's seem to be that they are noisier than CCD imagers and cannot be cooled. I read a few more recently but can't remember them off-hand. If its no-compromise astrophotography you want, then a cooled CCD is the way to go.
For long exposures, more critical than the performance of your imager is going to be the performance of your mount. If you have a poor mount, no matter what imager you use, you will get poor images at long exposure times. I use the DSI on a celestron C8 SCT and have gotten really nice images. But then my mount is an an AstropPhysics 1200 GTO... But I'm in the same boat as you in terms of having learned the ropes, I now want to upgrade the CCD imager. I'll probably go for a used SBIG ST7 or ST8.
As far as autoguiding goes, I'm sure you could image with a DSLR and guide with the DSI if it was positioned in a piggybacked guidescope...
Fri Dec 16, 2005 11:10 am
A tricky one this but let's get the easy part over with - I use an unmodified Canon EOS 300d for Astro-photography but I also use a webcam (Toucam Pro) for autoguiding at the same time so provided you have a guide 'scope mounted on your main 'scope this will not represent any problem. Your DSI would make an excellent auto-guider with a suitable interface.
I limit my DSLR photographs to about three minutes maximum because of two things:- sensor noise and light pollution 'fogging'.
The latter affects both CCDs and DSLRs to the same extent so this can be a severe limiting factor for long exposure photography.
Sensor noise is much more significant with DSLRs which normally have a CMOS sensor and cannot be cooled.
The relatively short exposure times mean that not enough detail is captured in a single frame however, I resolve both sensor noise and lack of detail issues by taking many photographs and 'stacking' them with a 'dark frame subtraction to cancel out the sensor noise'.
As has been stated already, one the main limiting factors in long exposure photography is adequate tracking and again, taking many shorter exposures and stacking them helps to alleviate this problem too. Tracking problems will, of course, effect both CCDs and DSLRs to the same extent!
From this, you may think that I am advocating that a DSLR is the solution - this is not, however, the case! Both types of camera have their uses. For DSOs, an astro CCD is the ideal choice as it is very sensitive and gives a higher 'magnification' than a DSLR but if you wanted to take a wide field shot (say of the Pleiades) then you would find that the CCD camera would only capture a small amount of the cluster whereas the DSLR would be perfect!
As a good all rounder, the DSLR does it for me with the caveats mentioned above and the 'astro' versions of Canon's EOS range go some way to making the DSLR a very attractive proposition for astro use (although at some cost!). However, when I can afford it, I will also buy a CCD astro camera (maybe from Starlight) to compliment the DSLR that I currently use as in the real world, I really could use both to good effect!
Sat Dec 17, 2005 8:50 am
I recently had a Canon 20Da for a short two week period (one of which was Moon'd out). Conveniently ignoring all technical comparisons between the DSLR and a cooled astronomical CCD camera (I also own an SXV-M8C), the big bonus when using a DSLR is that it's all wrapped up in one easy to use package. The interactive focusing mode of the 20Da is great to use and largely removes the need to have a separate PC with focusing assist software. It's noise was also very well contained with its exposures looking very clean in comparison with my own Canon 10D.
In the week I had to use it, I took mostly wide field images, here are some examples...
Sat Dec 17, 2005 12:26 pm
Lovely shots of M31 and M45 especially the 1st M45. From your description of the difference in the noise levels between the 10D and the 20DA it is not completely clear how much of an improvement you saw - would you describe the difference as significant? I ask because I have a 300 D which has much in common with the 10D and I am now happy with focus as I use DSLRFocus and find the whole thing intuitive and useful but sensor noise is always an issue (although resolveable to large extent).
I also have a Skywatcher 80ED and am looking forward to using it in earnest on M45 if I can get some clear skies as my previous attempts with a Skywatcher 80 Short Tube spoilt this object with chromatic aberrations as you would expect!
Mon Jan 09, 2006 1:00 am
personaly I don't own a digital camera capeable of astro photography
but I do have several friends who do and they all seem to be using cannon 300d or the 350d and yes they do manage to take some remarkable pictures I've seen them taken raw format and again when processed in photoshop or kccd/similar and now another program/software has been found that is free to download It is to deal with just the things you are suffering from on this post subject camera noise /and graining the program is called neatimage.
its well capeable of de -noising (if thats the word)lol. the Canon eos20d
in fact its for many of the leading brands of camera casio fujifilm hp kodak nikon olympus and so on
you get a basic package but register it and it becomes a lot more powerful they tell me hope this reply is of some use to you
I am just really starting out here myself have got a Meade LPI and just got me an untouched philips toucam 740k off ebay today anyone any good with a soldering iron for modding one step forward march[:D]
all the best
Fri Mar 10, 2006 5:06 pm
I've just started out with a Meade ETX-105 and an LPI but I'd like to get pictures like the samples above - I've seen colourful results of M42 from samples of the Cannon 20d as it apparently lets in more red light than most SLRs?
Do you have any images to share from the LPI? what do you think of it? I struggle with the s/w and think it'll get harder with a better camera but then maybe th escope is too small?
Any help is greatly appreciated
Mon Jun 19, 2006 6:40 pm
Al, check out the following web sites:
This is the official canon website on astro imaging with canon eos cameras, and very informative, also:
Then search the images captured with canon eos 10D and 300D cameras.
These should convince you that high quality astro imaging is possible with SLR type digital cameras. I use StarlightXpress ccd cameras and SLR digital for imaging. Both have their uses but the learning curve with SLR types is miniscule (particularly if you already use an SLR for â€˜conventionalâ€™ photography) compared to getting up and running with a ccd camera.You can obtain a mint second hand canon eos 300D body from reputable dealers at the moment for Â£299.00 (check the ffordes photographic web site, for instance).
Mon Jun 19, 2006 7:46 pm
[font=arial][color=#00cc33][size=3]Just be aware that the D20a may not be useable for general photography without the addition of an IR filter. It is my understanding that this is one of the differences between the D20a and the standard D20.[/size][/color][/font]
[font=arial][color=#00cc33][size=3]With the IR filter removed, the cameral is more sensitive to the red end of the spectrum (where we find Ha emissions). This is good for astro work, but not for general photography. Removal of the IR filter is also likely to compromise the function of the auto focus feature when used for general photography.[/size][/color][/font]
[font=arial][color=#00cc33][size=3]As I say, it is fixable with a filter, but you mat need to be aware that you will have that little bit of extra expense.[/size][/color][/font]
[size=3][font="times new roman"][color=#00cc33] [/color][/font][/size]
Mon Jun 19, 2006 10:00 pm
I wouldn't worry about the canon 20Da. It's no longer made (rumours abound on the web of canon introducing a 30Da) and it's not available second hand worldwide.
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