Waxing Half Moon -Astrophotography-Digital Rebel - 10-20-04

[vwestervelt]

Well, it's been a while...(company moved me last fall) since I've had my telescope & Dig Rebel out.

Last night I went after a half moon (it was 54.7% phase actually..missed the 50)

The link is a page describing hardware used, and resulting images. Images are reduced for web, but are all taken with the Dig Rebel.

I'd appreciate comments, tips...etc. Struggling a bit with exposure with such a contrasting (light to dark) image with such a powerful lens...(telescope at F10 is equiv to 2100mm 8" apature)

I was pleased with the images, but I'm always wanting to improve :)

http://www.vernwestervelt.com/Astronomy/waxing_half_moon_102004.htm

Vern Westervelt "look to the night sky, dream of the future while you see the past"

[BrandonSi]

Move closer.

Kidding :)

Nice shots, I really like them.. make me want to get a telescope.

[vwestervelt]

Thanks Brandon...it's proven to be an extremely challenging photography type....(but very addicting).

And hey, my wife likes it, keeps me in the yard :)

still open for tips and comments....

Vern

[PhotoManMike]

Hi Vern,

Great images! One question though: why did you feel you needed to use the SkyGlow filter? It won't provide any benefit for the moon, and it probably cost you a stop or two of exposure, as well as some color shift.

You didn't mention on your web page if you were using the RC-1 wireless remote controller. I highly recommend this for astrophotography (I have one I use with my 100). Best $20 I ever spent on camera equipment!

The diameter of the moon at the film plane is roughly the focal length of your telescope in millimeters/110, which would be about 19mm with the 2100 mm focal length of your 'scope. That's why it doesn't fit onto the 15 mm APS-C size sensor in your DRebel.

As far as exposure, the last time I imaged the moon with my SCT (9/29/04, a day past full and 5 days before I got my 20D), I used 400 speed film and I guesstimated a starting point for exposure at about 1/1000 sec by using the "sunny 16" rule and adjusting the time for the brighter image at f/10. I also looked at the information in Michael Covington's book, "Astrophotography for the Amateur" (which I also recommend), and his tables gave a couple of stops greater exposure. This made sense because you don't want the moon to appear 18% grey!

In any event, I made a couple of series of exposures between 1/750 and 1/125, but I found that all of the images except the 1/750's could be made usable with some curve adjustments when I scanned them in. Remember though that I was using 400 speed, not 100, and I didn't have the skyglow filter. Slow my numbers down by 4 stops (2 for the film speed and 2 for the filter) and we're in the same ballpark.

I can sympathize completely with your focusing difficulties! On an entire 24 exposure roll of film, I only had two images that were focused well enough to really use.

Practice your technique now--the last lunar eclipse until 2007 is less than six days away!

Regards,
Mike

[pcasciola]

I'm actually trying to get ready for that lunar eclipse now. I just ordered the T-mount for my 20D, and picked up the RC-80N3 remote today.

A friend of mine has a 9" Schmidt-Cassegrain (Celestron CGE I think).

Does anyone know if the T-mount is all I need to hook up to that scope?

I'd also like to hook the 20D up to his German equatorial mount with my 300mm F/4L for some nebula shots. Does anyone know if that is possible and what I would need to mount the camera on that type of scope mount?

[PhotoManMike]

Hi Phil,

To hook up a 20D (or any EOS SLR) to an SCT, you'll need a T-adapter to convert between the rear cell threads and a T thread (Celestron p/n 93633-A), and you'll need a T ring to adapt the EOS bayonet mount to a T thread. The latter can be found at just about any good sized camera store or ordered online.

With this setup, the image of the full moon will be larger than the field of view on the 20D with an 8 or 9-1/4 inch SCT. You'll therefore also want to consider using Celestron's f/6.3 reducer/corrector. If my math is right, the entire full moon should just fit into the field of view of the 20D with a 9-1/4 inch and the f/6.3 reducer

Mike

[ron chappel]

Um...doesn't the EOS Tmount include everything needed?
Just asking as i'm not experienced at telescopes

Vern i can see why you wanted to get exactly 50% moon-it looks great cutting the diagonal of a square frame

[PhotoManMike]

Hi Ron,

You need both pieces. One is specific to the telescope, the other is specific to the camera lensmount. The common interface is the T-thread in the middle. Check out this page:

http://www.celestron.com/prod_pgs/accessories/photo_visual_accessories.htm

Scroll down about 2/3 of the way, to where it says "T-Adapters". T-rings are listed there also, the second accessory category after T-Adapters.

Mike

[pcasciola]

Thanks PhotoManMike, that's exactly the info I needed. Part numbers and everything!!! The f/6.3 reducer is a little expensive, so I'm going to do a little more research to make sure that is the right one to fit the moon in frame with the 1.6x crop of the 20D.

Worst comes to worst I'll throw my 300mm on the 20D, which gets some pretty decent moon shots on it's own: Moon pic with 20D and 300mm F/4L (http://www.casciola.com/pics/moon300mm.jpg)

[vwestervelt]

Thanks for the inputs.

PhotomanMike...I appreciate your commentary. About the remote cable...for shots under 30 seconds, all that's needed is the USB cable and remote capture. It's a bit easier this way as I can stress tie the cable to the table to keep me from inadvertantly "tugging" on the scope...wasting the shot :)

I'm 30 miles NW of Dallas/Fort Worth....without the sky glow filter, the "glow" from light pollution will tend to "fuzz" out contrast as it slightly lightens the frame. You can easily level it out with Photoshop, but I've found that the simple addition of the filter greatly enhances contrast from a light polluted site. This filter is a must for nebulae if you have any light pollution.....(when I win a lottery, I'm moving to a mountain in CO :)

For longer shots, I've made an adapter that uses the miniplug connection of the remote trigger, but connects to my parralell port. (I'm a 20 year electronics engineer :) I control shutter and frame integration with a program called "DslrFocus" (www.dslrfocus.com) This is a wonderful program to automate long exposure shots, as well as integrate several medium shots into one. You need but build/buy the cable to do anything over 30 secs. I do have the remote shutter, but don't use it. I really would need it to be about 15 feet to be practical...I don't like working too close to the scope in case I bump it out of alingment.

And I'm studying up on all the weather dances I can find to keep the sky clear for the eclipse.....(this is no small feat as I'm 6'6", 275...hard work)

PCASCIOLA......I'd also recommend a "tele-adapter" for your T-ring. www.telescope.com has one, but you'll need to beef theirs up a bit. This is a standard "t-ring to rear cell" adapter, but this one is adjustable, allowing you a range of motion of around 1 1/2 inches. depending on the focal travel of your scope, this can give you two advantages....1- pretty much ensure you can bring your camera to focus...especially if you use filters that will change your focal length etc....2 - allow you to adjust focal length to change the field landing on the sensor to reduce vignetting....this also is useful if you wand a "specific" field for a lunar shot..but the filter or barlow changes the field by effectively putting the sensor farther away (longer focal)...the adapter can move you back to the desired field. You may not want/need to get that crazy....I'm addicted :)

And PhotoMan is right...If you don't get the 6.3 reducer, you will shortly after you start imaging :) It's useful, and puts some brighter nebulae in range of the scope listed...M27 for example. (will give you much shorter exposure times.....which makes tracking/alignment less of an issue...

RON CHAPPEL......I actually prefer the Mosaic method simply due to the increased contrast of the crater detail I pick up at F10...when you back the mosaic down to a normal 8 x 10, the result is significantly better than the single frame. The resultant image is around 6000x4000....easily puts you within reach of a larger print..

PCASCIOLA....with the 6.3 reducer.....T-Ring....T-ring to visual back....and a tele-adapter (get the adjustable one)...the moon should easily fit to a frame with your 9 1/4 SCT....

Note about the adjustable teleadapter. I had some teflon slugs inserted carefully into mine to reduce play in the adapter. keeping the sensor perpendicual to the focal plane is very important for contrast and focus...if it's not, you can actually get part of the moon in focus and some not...(I have several CD's of shots like this till I figured what the heck was going on....)


Thanks for the inputs....!!! PHotoman, I'm going to do a little study on the exposure.....I've never really gotten it completely to my satisfaction.

[billsh]

When is the lunar eclipse? I hadn't heard. (right now I'm living in a cave called "the office") I would like to try and shoot it with my 20D and 400 5.6 sigma. I have shot the moon a few times. Anything different when shooting an eclipse?

[amorrison]

Unless I am mistaken, the F6.3 reducer also flattens the field, which is curved by nature in SCTs and you may find that you cannot get the entire moon in focus at the same time, without it. Had that problem with my C11 anyway. Wishing you clear skies for the eclipse!!

[vwestervelt]

yep, you're right. Especially with the C11..(much longer focal length if I"m not mistaken..)

At F10 without the reducer you are imaging a smaller field which isn't bad, but when you move out to the edges where the landscape is significantly distant in perspective....does make it a challenge.

Too bad the auto depth of field won't work on the telescope :)

[Jim_T]

Hey.. There is a moon !!... All we've seen where I live since the 12th of October is low dark grey clouds overhead.

There's one small technical error on your web page.. The images are superb, and the layout is good, but you have a small typo.. You have "Cannon" Rebel instead of "Canon" Rebel (There's only one N) :)

Those are great shots.. I'm impressed. They're far better thant what I can do with my 100-400 lens.. I've been pondering the idea of buying a telescope.. (I recently moved to the country where it 's dark enough at night to see the milky way overhead). I just hope when I do pick up a telescope, I get the same results as you :)

[amorrison]

Eclipse is October 27th. See http://science.nasa.gov/headlines/y2004/13oct_lunareclipse.htm

Schedule is included there. (Sorry if this is off-topic).

[vwestervelt]

thanks JimT....I'll remove the offending "n" :)

I would love to be able to see the milky way from where I'm at.

My focus has been galaxies and Nebulae..(haven't rebuilt my site yet....) very difficult with light pollution.

Looking at the weather....doesn't look like I'm going to have the sky to see the eclipse :(

[billsh]

Thanks agmorrison for the link. Sorry if my post was off topic.

[ron chappel]

Ah thanks mike

Our club is going to an astro night soon (full moon) so i am going to take along all the T rings i have lying around for others to use.
The club member who organized the night has allready confirmed that the scopes accept normal T-rings so that makes it super easy :)

[vwestervelt]

Here's the link for the focus cable I'm using...

http://www.dslrfocus.com/help/eoscable.htm

[Tom W]

Eclipse is October 27th. See http://science.nasa.gov/headlines/y2004/13oct_lunareclipse.htm

Schedule is included there. (Sorry if this is off-topic).

Thanks for the info - its on topic as far as I'm concerned.

BTW, vwestervelt, nice images. I get to use a 100-400 and a 1.4X teleconverter for my moon shots. A good scope and mount are in the future, but not right now...

[robertwgross]

Here's the link for the focus cable I'm using...

http://www.dslrfocus.com/help/eoscable.htm

Does this link work? It doesn't now.

---Bob Gross---

[vwestervelt]

The link has been intermittant this weekend I've heard.

[vwestervelt]

Jim T.....I have fixed the "technical error" :) Thanks! And my mom was an english teacher :)