Very confused wet-darkroom photographer

I really need help with my digital confusion I have many years experience in a wet darkroom, a few years ago I quite happily and smoothly made the transition to digital photography - Sheer bliss. But now I'm extremely confused with the digital astro-photography. I at last managed to get a chance to photograph Saturn again tonight, but :!: :!: This is the result:

www.irishastronomy.org/user_resources/fi...08768700-Saturn7.jpg

According to the DSI software, I at last managed to take 200 frames, the combine box was ticked. I don't see any difference between this picture and the one I managed to get a few nights ago:

www.irishastronomy.org/user_resources/fi...08768748-Saturn6.jpg

The second picture was only 17 frames and exposure was 1.0, tonights picture was 200 frames and the exposure was 0.1200, the other strange thing is tonights picture amounts to 6 Kb while the other amounts to 6.50 Kb. I had hoped that by reducing exposure, I would have put a little more detail in Saturn, but they look both the same. The pictures are in mono as I can never get rid of the purple colour which makes Saturn look rediculous. I now have 7 pictures of Saturn all taken under different circumstances and exposure, some are only 1 or 2 frames but not a bit of difference between them.
Any advice anyone?

Bill H.

Hi Bill - I feel your pain...

My understanding of the DSI is that when you have the combine box checked, it takes pic 1 then pic 2 and combines them. It then takes pic 3 and then combines it with the combined pic 1 & 2. Then it adds in pic 4 etc etc. Now, I don't know exactly what the combine algorithm is but I assume it is some kind of average of two pics - the already combined stack plus the latest pic it has just taken. As you take more frames, the quality of the pic increases - to a point.

I'm sure I read in the DSI manual somewhere that they reckon 90 stacked frames should reduce noise to a minimum. Less than 90 (or so) will give you some noise. More than 90 or so will not result in any significant difference (all other things being equal).

One thing I have done is remove the IR filter. I have read in the DSI Yahoo group that it really has no significant impact except on colour shots. Also, there seems to be significant quality issues with the filters. Mine has a horrible streak across it which shows on every frame - a flat removes it but I chose to take the filter out altogether.

Now, this said, I actually think your Saturn pics are good - they are definately as good as my best ones! But remember - the DSI does what it says on the tin. Deep Sky... Have a lash at M42 or some clusters (M46, 47, 48 etc). I tried the Beehive the other night and I was gobsmacked at the detail I could get out of the DSI. And like you, my Saturn images were not great. But I certainly got down to mag 15 stars with the DSI and an 8"SCT and that was without trying. As I improve my technique, I hope to get better. Assuming the cloud and sky-glow stays away...

Here's my best pic of Jupiter so far - 33 frames. I took another of 510 frames and that is *worse* - so bad I'm embarassed to upload it...

www.irishastronomy.org/user_resources/fi...8773073-Jupiter3.tif


Dave

Hi Dave,
Thanks for the words of encouragement. I'm more convinced that either I'm missing something out, or my software isn't working. I would have expected my 200 stacked images to amount to in excess of 150 kb's rather than the 5 kb it is. Your 37 stacked images of Jupiter amount to 68 kb and when I checked your Saturn image, it was around the 100 kb. As my DSI takes images, the quality of the first image never improves in the preview, it stays static. The final result and file size leads me to believe that it isn't actually stacking any images. Also, when I change the DSI for the LPI, it says the LPI can't be found, yet I know the software was loaded. Perhaps I have a serious sofware prob? I decided to try the LPI, just to see if it was any better at imaging the planets, but alas, it tells me it's not there! I shall try some deepsky imaging next chance I get.
Bill

Hi Bill - the size that an image reaches seems to be black magic! I just checked through some previous images and one particular Saturn image I took consisted of 117 stacked images. But here's the key - each of the 117 individual images amounted to about 200 to 220K. The combine image (of all 117 frames) was 68K - nearly a quarter of the size! I guess the combing algorithm is fairly complex and beyond the comprehension of mere mortals.

Needless to say, I now totally ignore file sizes and just visually look at the quality of the image.

Dont forget, as in your posted image, the majority of that picture is black - that can easily be represented by just a few 'bits' of data. I'm sure if it was a nice piccy of an orchid, in colour and well lit, the image size would be far far greater becuase you are recording all the colour levels. In an astrophoto, the predominant colour is black (for mono images of course).

Certainly, after stacking the first handful of images, the picture quality doesn't seem to get noticeably better - but I bet you the more images you get, the better the post-production image will be. I do see an improvement, especially deep sky, with the first 3 or 4 images, then it starts looking the same as more images are added.

One way of knowing you are getting lots of individual images is to choose 'save all uncombined images' when you click the 'save proc' button.

Finally, when you remove the DSI, shut down autostar competeley. Next, plug in the LPI then restart autostar. That might do the trick.

Dave

Hi Bill,
what king of scope are you using for the saturn images?
Looking at the center of saturn, it seems like to me that the center of the image is still to bright.
If I were you, this is what I would try.
Turn off (if possible) any stacking or image processing the DSI does and save the images unmodified into a directory and stack them using registax, or have you done this already ??

As for IR blocking filters, I can only speak about the toucam pro and 300D in this regard, it is considered that the toucam pro is too sensitive to IR, this can lead to a slightly washed out image and a loss of detail, so its highly recommended that you use a IR blocking filter with the toucam pro,
The canon 300D has a built-in IR blocking filter but unfortnately it leaks into the visible red and blocks some of the red, thats what all this modified 300d caper comes from.

When you look at the imaging chip in the DSI, is it the samed size as the chip in the LPI ??
The LPI and toucam pro have the same number of pixcels, BUT the LPI chip is bigger, I've seen this for myself, this mean that the LPI pixcels are bigger, this makes it harder to get as sharp an image as the toucam, as each pixcel is representing a bigger amount of surface area, so images of Jupiter/etc would be blockier.
Maybe the software that comes with it has builtin stacking to try and compensate for that ? theoretically that should do the trick,
I read a review on the web a while back comparing the LPI to the toucam pro and the toucam beat it by a mile for detail on jupiter and saturn etc.
I dont know if this is also the situation for the DSI ?!?

Now, I've nothing against the LPI, I'm sure with experience, you'll be able to get an excellent image out of it.

I'd love to give one of these LPIs or DSIs a run for their money on my scope with jupiter or saturn, to see how good they really are.

Bill - you can have your cake and eat it! As Dave said, you can save all your individual images AND you can still have the combined single image.

When you click on 'save proc', choose 'save all uncombined images'. After you have finished imaging (or the clouds have rolled in ) check the directory where the images are stored. What you'll see is this:

Saturn1.jpg
Saturn1-1.jpg
Saturn1-2.jpg
Saturn1-3.jpg
Saturn1-4.jpg
Saturn1-5.jpg

Saturn1.jpg is the combined (using the Meade algorithm) image of 1-1 through 1-5. If you like, you can process the original images in something like Registax and see if there is a difference. I've tried this and the jury is out...

As regards the IR filter - Dave is probably right - I'm not sure how it improves or disimproves images you take but certainly the Meade group seem to think that at least for deep sky it is OK to remove it. For planets, washed out detail may be the case. That said, apparently the IR filter is not great anyway and some advocate removing the DSI filter and using a threaded eyepiece IR filter in the nosepiece.

To be honest, I found there to be no difference in Saturn with or without the IR filter in the DSI.

But one thing is for sure, very few DSI imagers (if any) are posting planetary images with the DSI - they are all deep sky stuff - and very nice too. That is what the DSI excels at. I guess it makes sense since Meade also provide the LPI alternative for just that, Lunar Planetary Imaging.

www.meade.com/dsi/gallery/gallery.html shows what an 8" LX200 can do with the DSI - note, no planets!

Since your pics of Saturn look in focus and you have gotten over the 01% hump, I'd suggest trying a deep sky object - try M42. This is what I did and I got a very pleasant surprise. My images of Saturn were just the same as yours, even with 100+ combined images. But then when I turned to M42 - detail was super, even the colour worked!

I'm now concentrating on deep sky stuff with the DSI and as soon as these pesky clouds go away, I'll post up any images I get!

Cheers

Dave

PS:
Here are some comments on the DSI, LPI and Toucam from a guy who has an up-coming article on the DSI in Sky and Telescope (so I assume he knows his stuff!)

DSI is hands-down the DSO winner.
Toucam can't be beat for planetary (but LPI may be just as good).
LPI is supported up to 16 sec exposure in K3CCD Tools - makes a
pretty good guide camera (Std Toucam can't do this).
DSI is "weak" for planetary (you can do it, but it takes more work
for lesser result)