Astrophotography w/300D - M27 Dumbell Nebula

[vwestervelt]

Well, I don't know if there are many out there interested in astrophotography, but I've finally got a web page built for some of my first images with the new camera.

I'm very pleased with my initial results, though I'm currently limited to around 75 seconds exposure at F1.98 with the Fastar lens for my telescope. (8" Nextstar GPS w/Fastar assy)

The reason for this limitation is the absence of a wedge mount to polar align the telescope (for long exposure, you need to precisely align to the axis of the earth to counteract our rotation. To give you an idea, if I turn off the computer control on my telescope, this object would leave the field of view at F1.98 in about 9 seconds.)

I'm currently using Alt-Az mode with will give me field rotation for long exposure. So...I'm limited to higher ISO and shorter exposures. All pictures on this page are 60 second exposures. I can't wait to see what this camera can do on a long exposure lower ISO on these targets.

Anyway, comments welcome. These are my first shots w/this camera so be gentle :)

http://www.vernwestervelt.com/Nebulae/M27.htm

[timnelsonic]

Thanks for sharing. I plan on picking up a 300D in the next few weeks and I'm dying to try it with my Celestron Nexstar 4. I've had poor success with this scope using point-and-shoot digital cameras...I suspect this camera will work a lot better.

Please post more pix when you have some. Hopefully, I'll be back in a couple of months with some of my own!

[vwestervelt]

Thanks Tim,

The only images I've had time to post are at

http://www.vernwestervelt.com/Astrophotography.htm

I have several other methods I've used, but I'm really liking my initial results from the 300D.

A problem you'll have with the nextstar 4 will definitely be weight. I have a Nextstar 8 also (also a single fork mount)...the weight of the camera makes it VERY unstable. If you breath on it , it wiggles and streaks the stars. It was the very reason that led me to the Nextstar 8 gps.

The Meade ETX 90 or 125 are much better at comparable optics for stability as they have dual fork mounts.

For what it's worth, with the nextstar 4 I'd go with as small and light of a camera as possible.

It probably would work fine for planetary though! your exposures are going to be MUCH shorter (1/20 - 1/60 or so usually)

Thanks again for you comments. It's going to take a while to get this right for me :) work keeps getting in the way! and sleep :)

[timnelsonic]

I'm not suprised that weight is an issue. I noticed the same thing when I was attempting eyepiece projection using a Kodak DC 260. For a non-SLR, that is a pretty heavy camera. In addition to weight, it was just an awkward setup to have such a big camera attached to the eyepiece.

I'm hoping the 300D will work better, because I won't have to do eyepiece proejction and it can mount on the rear. Since I live in light-polluted Southern California, my 4" scope isn't much good for deep sky objects, so I'll be limiting my work to lunar and planetary work anyway. Much easier to practice with, that's for sure!

Let us know when you have more stuff posted.

[vwestervelt]

Another point.....

FOCUS

If you're not using a wedge for polar alignment, you will have a difficult time focusing with this camera and the nexstar 4i.

There's just no easy way to get your eye to the viewfinder in Alt-az mode.

Also....BE CAREFUL....in alt-az with the nexstar 4, you can damage your camera as I don't think there's enough clearance between the rear mount and the tele base! You can set limiters in the scope setup to prevent this...but when the scope is moving I'd rest my hand on the off switch to be safe :)

[jimsloy]

Vern-

I never got a chance to chat w/ you yet, but your website pics look great! I think I've decided on the Meade ETX90, or, Meade ETX105 (which I think is new and wont ship for 4-5mnths). Think spending the extra $$ for the 125 is worth it over the 90?

[vwestervelt]

Jim, a lot of that decision depends on what you want to do.

The 90AT/105AT & 125AT are all good scopes....I recommend AT because if you're interested in astrophotography, you'll want the delux tripod and ability to go equitorial for longer exposures.

A point of caution. If you want to do deep sky objects....i.e Orion Nebula, Galaxies etc. you may want to consider a different approach.

the 90/105/125 are F13.8/F14/F15 at prime focus respectively (prime focus meaning using the telescope as a lens). As an example, the dumbell nebula I took in this post was at F1.98. The long focal lengths and large F ratings mean LONG exposures! Look at my page with the ring nebula and you can see what I mean. Most of those were at F10 and 60 seconds.

The 60 second shot of M27 here would take several minutes at F14 for comparable brightness....not sure exactly but I'd guess around 13 minutes. Alignment of your scope gets increasingly complex as well for this long of an exposure (precise star alignment over the course of the exposure is paramount...a small misalignment will streak your stars on a 10 minute exposure...we are rotating pretty fast after all :)). That plus the odd puff of wind can really ruin your night after waiting 10 minutes with the shutter open.

For planetary nebula or solar system on the other hand, these 3 scopes are great! For Jupiter you'll likely end up using a 2x barlow to take it to F24! Planets are BRIGHT compared to stars.

It's the main reason I settled on the Celestron Nexstar 8 gps with the fastar lens option. All at prime focus I can do F10...which is the native telescope at 2032mm focal length. F6.3 with a focal reducer, and F1.98 with the fastar option. It makes a very flexible scope. The F1.98 let's me take some very large objects in a single frame that would take a mosaic (several images pieced together) for one of the meade telescopes listed here.

If you go this route, you'll likely end up purchasing a F4-F6 refractor or newtonian when you get around to wanting some nebula shots.

In any event, you'll end up helping the economy and having fun in the process :)

[vwestervelt]

Jim, What type of photography are you initially interested in?

[CyberDyneSystems]

I am no expert on astrophotography,. but I habe two items that may be of help.

1: Focusing,
Canon makes an item called "Angle finder C" it attaches to the eyepiece and gives you a 90% veiwfinder that pivots,. very handy on a low tripod mount and will alleviate a number of issues. Also it has built in magnification that is adjustable up to 2.5X if i remember correctly which also aids in manual focus.

2: Long exposure,
Here I am completely out of my expertise,. but I have read where astrophotographers will instead of taking one long exposure, they will take several shorter ones and layer them in Photoshop to bring out the brightness and cut down on grain/noise.

[vwestervelt]

you are right on both scores.

1. The right angle focuser helps with astrophotography, but really only with very bright objects. I happen to have one, but it really only get's you "close to focus". It's so small and allows so little light to pass, you just can't fine tune focus....it may very well be partially due to my old pair of eyes :)

2. Stacking really focuses on brightness and contrast of the target image. The unfortunate part here is you stack noise as well. There are some sophisticated programs that will help reduce signal to noise ratio, but since noise is going to be generated more or less consistently (all variables remaining constant...target glow...thermal...power..) then you also amplify noise along with the target. These software packages are really good at filtering out Atmospheric distortion...as this won't appear exactly the same in any two images....kind of like looking down a blacktop on a hot summer day...the "heat waves" would never duplicate exactly in two frames....thus stacking would enhance real detail while reducing distortion.

The real solution is to "subtract" noise......then stack the images using these software packages. Again, I haven't been able to find a way to take a darkframe with this camera. apparently if target signal is below a threshold, it cancels all noise. I've done up to 5 minutes at iso1600 with cap on and gotten flat black.

Still happy with the camera though.

[jimsloy]

I am not so interested in Nebula as I am the moon and planetary objects. That's why I'm thinking the Meade 105 or 125 should cut it. Agreed?

[vwestervelt]

:) you know...that's exactly what I said to my wife to justify my ETX90 (in 97)......

well...needless to say....2 telescopes and many cameras later... :)

I do love shooting the moon though!

And agreed, you'll be happy with either, very good optics and I'm sure they've got the software worked out (was buggy in 98)

[vwestervelt]

Another point about these scopes.....they are very nicely PORTABLE.!!!

Get a foam lined hard case and you're set to take it wherever you go...

let me know what you decide.

[tony723]

Hi Vwestervelt,

If I use 90AT with 300D, can I shorten the exposure time by 'stacking' photo? I heard that there are some PC software work with webcam can perform quite sharp images.

Also I am new to astrophotography, what is the basic equipment required other than the telescope (i.e. 90AT) and the camera (i.e. 300D)? Can you post some photos of your setup?

Many thanks!

[vwestervelt]

Hi Tony,

Well, there's no short answer to your question.

Yes, you can stack images to enhance contrast and brightness....BUT....you also stack noise. You have to subtract noise out of each frame as much as possible BEFORE stacking.

For lunar and planetary, brightness isn't a problem, and you can use stacking to reduce signal to noise ratio. The theory is that "real" detail only appears in the same place on each image and "noise" is random...therefore the more images you stack...noise ratio gets less.....

All that said....The best photo's I've taken, and the best I've seen in astrophotography are longer exposure (either digital or film) and lower ISO ratings.

There's a thousand variations...not the least of which is having a good dark sky w/out light pollution (skyglow filters can help, but limit exposures.)

I'll try and get some pictures of my setup on this site this weekend. The weather stinks here so I may as well do that :) No stars this week....

Vern

[vwestervelt]

Jim, another comment about this choice in scopes.....You may also want to consider a small apochromatic refractor.

80-100mm apeture at F5 or F6 should run in the 500-900.00 range. they won't have the focal lenght you're looking for with planetary, but you can always get a good quality Barlow and this will allow you the flexibilty of a great wide field nebula scope.

just a thought. In hindsight, I wish I had started this way.

Vern Westervelt

[sam bailey]

I just bought a Rebel. I quickly figured out that existing EOS T-rings will not work. They are too loose. What I can't figure out is that I verified an EF lens fits just fine, just as good as the EF-S that came with it. I have not had time to investigate closer at this time. I have heard via Astronomics that I am not the first one to experience this. I have tried two difference manufacturers T-rings with the same result. Go figure!. I have emailed Scopetronics to see if they are interested in making them. Otherwise I will get a cheap EF lens and take it apart to make one. Anyone noticed this yet?

[vwestervelt]

Not sure about that, I'm using a standard eos t-ring and it seems to work fine.

[sam bailey]

Thanks for the response. I wonder if there is a difference since you have the non USA 300D version instead of the Rebel. Can you mount an EF-S lens on yours? The EF-S lenses are not supposed to be backwards compatible. Your bayonet mount may be different from mine.

[rdenney]

vwestervelt wrote:
Jim, another comment about this choice in scopes.....You may also want to consider a small apochromatic refractor.

80-100mm apeture at F5 or F6 should run in the 500-900.00 range. they won't have the focal lenght you're looking for with planetary, but you can always get a good quality Barlow and this will allow you the flexibilty of a great wide field nebula scope.

just a thought. In hindsight, I wish I had started this way.

Vern Westervelt

I have a Pentacon Practicar medium-format lens that I can adapt to my Canon. It is a 500mm lens at f/5.6, which gives it a primary aperture of 90mm. With five elements and multicoating, it's quite a good performer, but I haven't done anything astronomical with it yet. You can get these in Pentax screw mount, but the better approach is to get one in Pentacon Six mount, and then get a Pentacon Six to EOS adaptor (which is about $35). In perfect condition, the lenses are well under $500. It's a heavy sucker, though.

Rick "who has a Pentacon-Six-mount 2x teleconverter, too" Denney

[RichardSimon]

vwestervelt wrote:
...
Yes, you can stack images to enhance contrast and brightness....BUT....you also stack noise. You have to subtract noise out of each frame as much as possible BEFORE stacking.
...

Vern

First - I was impressed with the M27 picture -- wow!

You are incorrect about the effects of stacking. In fact, if the noise in the image is random, as you add frames together (preferably a true mathematical average), the amount of noise will decrease as the square root of the number of images. Thus, 9 images, each with 1 minute exposure, will theoreticaly have 1/3 the noise of an individual image. There are limits to how well this works in practice - certain types of errors (such as a hot pixel) will not decrease no matter how many frames you add. For those sorts or errors, it is essential to subtract a "dark frame". Another important effect can be related to having enough signal that the noise is well behaved, but the target is not overexposed... clipping at either end could reduce the effectiveness of adding frames.

If you are stacking frames, it is probably best to save the images in RAW format, and use software which will use all the bits in the 16-bit images (12 bits of useful dat, of course, from the 10D). I would try an exposure where the brightest stars are not too overexposed, and where the sky background is just visible. I have had some luck doing this, with noticeable improvements from stacking 8 frames, but I haven't done a great deal of experimenting. It seems that I get the best results (in terms of seeing faint stars) with the max ISO; when that is the case, stacking frames really helps with the noise.

There is one large qualification in all this - the camera is doing a number of peculiar things to the raw pixel data to produce an image. Interpolation over the Bayer pattern to get colors and internal noise processing will both introduce non-linear effects that may reduce the effectiveness of stacking frames. I imagine that using noise-reduction software before stacking frames is also a bad idea, since it would probably change the statistical properties of the noise and reduce the effectiveness of stacking frames.

Good luck!

[vwestervelt]

Richard, Thanks for the comments...!

I agree completely with your comments on stacking....but there are a couple of things working against this camera and that approach.

All things remaining constant....target in the frame, temperature outside, etc.......this camera produces a VERY consistent noise pattern. Part of the reason why is the "on-the-fly" sampling and noise processing it does.

I've taken as many as 75 images of the same target at the same exposure settings.....and sampled a specific pixel x pixel region from 10 of those random frames. The statistical graphs of those samples were dang near identical across all 10 frames....and I mean identical. I couldn't tell which was which without looking at the file name.

I don't argue that you can, with enough frames, "stack-out" the noise statistically, but I'm not crazy about freezing my arse off getting 25 x 5minute images of the target :)

It would just be SOOOOOOO much easier if I could get a dark frame with this camera :)

I'm still happy with the images, you'd think it would have been easy for Canon to give a software swith to turn off processing. How hard is it to do no code? :)

Anyway...thanks for the comments....I've been trying most of the various methods...stacking, neatimage..etc. Still not as good as dark frame.

Vern Westervelt

[sam bailey]

FIgured out the problem with the t-ring. Apparently both t-rings I had tried were for a smaller Canon design, even though one was clearly marked for an EOS. I went to a camera store that had several and the EOS one worked perfectly. Go figure. Plan to try some pictures of the total lunar eclispe tomorrow.

[agit-prop]

As you pointed out a wedge will help immensely with the field rotation. I've just completed modifications to my Meade LX10 to autoguide. I've added a celestron 80mm f/5 refractor (these are made by Synta in China and are available cheap) in a home-made guide-scope mount. I'm using a parallel port relay card and a webcam mounted to the 80mm to guide. The Astrovideo software from Algarve Astronomy is the smarts of the system as in analyzes images from the webcam and sends correction pulses via the relat interface. Granted, it doesn't have goto, but it is on a wedge!

Here's an image I made through the webcam (18 frames stacked) over a year ago...

http://www.pbase.com/image/3093133.jpg

I hope to exceed this image with my D30.

[Riod]

Your images of the dumbell are great. About ten years ago I tried to photograph the moon through a 6 inch reflector that I built many years before that. I had an adapter to attach my Pentax k-1000 to the scope. I had no success at all and finally gave up. There has to be something that I did not quite understand or comprehend!

Please detail the Fastar assembly. I would love to try again with my new 300d.

Thanks.

[jimsloy]

Got my Meade ETX-125EC. Ready for some shots. I got the T-mount for the 10D, but now, I've found I need the #64 adapter for the scope. Anything I need to order to get the astrophoto part of my life working?

Would a teleconverter on the 10D be of any use in doubling the scope zoom?

[kfong]

jimsloy wrote:

Would a teleconverter on the 10D be of any use in doubling the scope zoom?



Yes, but there are several caveat:
1. 10D talks to TC and TC tries to talk to your scope. The scope doesn't talk back and TC report an error to 10D. 10D thinks there is a bad lens in the mount and refuses to take any picture. Cure: You'll have to tape up the contacts in the TC.

+ usual problems in focusing your magnified image of star light.

Ken

[jimsloy]

Vern, et al:

I took my first images of the moon last nite, blurry, but I didn't use mirror lockup, fast exp, etc. - so I'm not too worried about that yet. The half moon took up more then 1 full frame and was very bright and still a bit blurry, but nonetheless, I can work on that skill.

As for Saturn, Nebula, etc: Will my Meade 125 coupled with the 10D and several images grab me anything? The 10D is mounted with the T-adapter and Meade camera mount, or, am I understanding this correctly in that some folks actually use the camera thru the different eyepieces that they see Saturn thru? (ie- pointing the camera thru the 6mm Plossl eyepiece).

[vwestervelt]

My web site crashed and it took a while to get back.

http://www.vernwestervelt.com/Astronomy/Astronomy.htm

It'll take a couple of weeks to rebuild :)