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Poor quality of lunar images with 20D/C90

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Anonymous
September 24, 2005 3:05:23 PM

Archived from groups: rec.photo.digital (More info?)

I have a relatively new DSLR and an old (~ 1980, black tube) Celestron
C90. The other light I tried taking a picture of the full moon with
the camera at prime focus (tripod, ASA 1600, 1/800, remote release
after ~10 sec of MLU), and the results were reasonably well-exposed
but very fuzzy (and noisy: maybe ISO 200 or 400 would be better). I
was using an Olympus Varimagni right angle finder attached to the
camera. This gives a 2.5x magnification of the viewfinder, and I got
the focus as sharp as I could. The view through the 20D viewfinder is
horrible, though . . . I wish the screen had at least a small spot of
fine-grained matte. There's a picture at:

http://home.comcast.net/~jgates777/Moon.html

I thought that perhaps the 'scope was damaged or had deteriorated in
some way, but visual observations (30mm Kellner) look very sharp. So,
I have a few questions:

1. Is it normal for lunar astrophotographs to have much lower
resolution than visual images?
2. Since the 'scope focuses "beyond infinity", it is very
difficult to focus on the screen in a Canon 20D. Do you have any tips
for manual focusing with a DSLR, or is it largely trial and error
("Jeff R." at sci.astro.amateur recommended a Hoffman mask)?
3. The tripod I was using was an old, cheap Velbon (~$25 new) I
bought for a video project, and is none too stable. If you touch the
'scope at all the image dances all over the place. After some
research, I've ordered a Bogen / Manfrotto 3246 with 488RC2 Midi
Ballhead that will be used primary for daylight photography, but it
hasn't arrived yet. Would you folks with experience expect this to be
any better?

I understand that the 'scope is not the greatest, and this was my first
try at lunar imaging, but my images look nowhere near as good as those
I've seen from similar setups. I don't expect miracles, but these
pictures are pretty sad. Any suggestions?

More about : poor quality lunar images 20d c90

Anonymous
September 24, 2005 6:42:16 PM

Archived from groups: rec.photo.digital (More info?)

Nominally it's about 1000mm f11, but I have read that the effective
aperture is more like f12.5 (as Ray Fisher suggests below). I'd
believe you about the exposure, but I read ISO 1600, 1/1800 from the
EXIF data and if anything the image looks underexposed.
Anonymous
September 24, 2005 6:57:02 PM

Archived from groups: rec.photo.digital (More info?)

I understand that there is not a lot of aperture with the C90, but
I've seen other C90 shots via afocal methods that are far better.
The link that Basiltoo posted below, for example
http://forums.dpreview.com/forums/read.asp?forum=1010&m...
shows what I would call very fine detail from such a small scope.
Admittedly, it's not a full moon, and the shodw adds quite a bit of
perceived detail. I'll try a less than full moon next time and play
around with the ISO/exposure tradeoff. Perhaps the new tripod will
help. Thanks for the comments and suggestions.
Related resources
Anonymous
September 24, 2005 7:01:18 PM

Archived from groups: rec.photo.digital (More info?)

Well, I'm not really attempting to get into astrophotography with
this sort of telescope. I just thought a moon shot would be
interesting. Getting an astronomical tripod seems a bit of overkill
unless I'm attempting guided exposures of planets and deep space
objects. If I were going to do that, I'd probably figure out a way
to spring for a telescope with at least 8" of aperture. But, as I
said, I did spring for a substantially better tripod for terrestrial
work, and hopefully that will help a bit.
Anonymous
September 24, 2005 7:02:27 PM

Archived from groups: rec.photo.digital (More info?)

Yes, I used MLU and a cable release. I waited for approximately 10
seconds after MLU before tripping the shutter.
Anonymous
September 24, 2005 7:04:37 PM

Archived from groups: rec.photo.digital (More info?)

Yes, saw that the other night. In fact, that image is was prompted me
to try a moon shot --- I wanted to see how well my (much older, well
traveled) C90 could do. Not very well, it seems.
Anonymous
September 24, 2005 10:25:13 PM

Archived from groups: rec.photo.digital (More info?)

Was you tripod sitting on a deck or on solid ground? A deck may be
suject to vibrations, although your shutter speed was quite high.

I have a C90 (older, orange) that I have been waiting to use with my
D70 to get some moon pictures. I say waiting because I have a
restricted view from my house due to hills and trees and the moon
hasn't been in position yet. Also coincidentally, I have been putting
up with a shakey Veblon for years and just recently bought a Manfretto
tripod. So far I have just tried to shoot some star trails with the
camera and a lens, but had trouble at first until I moved the tripod
off of the deck.
September 24, 2005 10:54:35 PM

Archived from groups: rec.photo.digital (More info?)

On 24 Sep 2005 11:05:23 -0700, "jess" <jgates@erols.com> wrote:

>I have a relatively new DSLR and an old (~ 1980, black tube) Celestron
>C90. The other light I tried taking a picture of the full moon with
>the camera at prime focus (tripod, ASA 1600, 1/800, remote release
>after ~10 sec of MLU), and the results were reasonably well-exposed
>but very fuzzy (and noisy: maybe ISO 200 or 400 would be better). I
>was using an Olympus Varimagni right angle finder attached to the
>camera. This gives a 2.5x magnification of the viewfinder, and I got
>the focus as sharp as I could. The view through the 20D viewfinder is
>horrible, though . . . I wish the screen had at least a small spot of
>fine-grained matte. There's a picture at:
>
>http://home.comcast.net/~jgates777/Moon.html
>
>I thought that perhaps the 'scope was damaged or had deteriorated in
>some way, but visual observations (30mm Kellner) look very sharp. So,
>I have a few questions:
>
> 1. Is it normal for lunar astrophotographs to have much lower
>resolution than visual images?
> 2. Since the 'scope focuses "beyond infinity", it is very
>difficult to focus on the screen in a Canon 20D. Do you have any tips
>for manual focusing with a DSLR, or is it largely trial and error
>("Jeff R." at sci.astro.amateur recommended a Hoffman mask)?
> 3. The tripod I was using was an old, cheap Velbon (~$25 new) I
>bought for a video project, and is none too stable. If you touch the
>'scope at all the image dances all over the place. After some
>research, I've ordered a Bogen / Manfrotto 3246 with 488RC2 Midi
>Ballhead that will be used primary for daylight photography, but it
>hasn't arrived yet. Would you folks with experience expect this to be
>any better?
>
>I understand that the 'scope is not the greatest, and this was my first
>try at lunar imaging, but my images look nowhere near as good as those
>I've seen from similar setups. I don't expect miracles, but these
>pictures are pretty sad. Any suggestions?

Your picture is fuzzy, alright! Mine are a little bit better, but not by a
lot... I just got a scope to use with my D70.... and yes its dam hard to focus!

I was shooting at 1/250 sec, ISO 800. The scope is a 4" MAK-CAS 1300mm f/13.

I was told that I would be better off with a scope with f/6 or so... maybe next
year!

Tripod is a Slik very heavy model (cost as much as the scope!) good for normal
photography, but it too shakes the moon if you touch it! I use the IR remote.

I'm going to try damping out vibration with an old coat or something and see if
that helps.

I will post a moon pic on alt.binaries.photos.original for you to see.
September 25, 2005 12:02:07 AM

Archived from groups: rec.photo.digital (More info?)

Whats the f number of the scope ?.
You should be able to expose the moon at approx f8, 1/250th with ISO 100.
You are right focussing can be difficult !
September 25, 2005 12:13:07 AM

Archived from groups: rec.photo.digital (More info?)

"jess" <jgates@erols.com> wrote in message
news:1127585123.145180.137920@o13g2000cwo.googlegroups.com...
> 3. The tripod I was using was an old, cheap Velbon (~$25 new) I
> bought for a video project, and is none too stable. If you touch the
> 'scope at all the image dances all over the place.
Why not get the tripod that Celestron sells for such a scope? It seems to
me that you are trying to get good photographs with equipment that is
totally inadequate (except for the scope that is).
Jim
Anonymous
September 25, 2005 12:56:14 AM

Archived from groups: rec.photo.digital (More info?)

"jess" <jgates@erols.com> wrote in news:1127585123.145180.137920
@o13g2000cwo.googlegroups.com:

> I have a relatively new DSLR and an old (~ 1980, black tube) Celestron
> C90. The other light I tried taking a picture of the full moon with
> the camera at prime focus (tripod, ASA 1600, 1/800, remote release
> after ~10 sec of MLU), and the results were reasonably well-exposed
> but very fuzzy

You might find this thread interesting:
http://forums.dpreview.com/forums/read.asp?forum=1010&m...

--
Regards,
Baz
Anonymous
September 25, 2005 1:03:42 AM

Archived from groups: rec.photo.digital (More info?)

In article <1127585123.145180.137920@o13g2000cwo.googlegroups.com>,
"jess" <jgates@erols.com> wrote:

> I have a relatively new DSLR and an old (~ 1980, black tube) Celestron
> C90. The other light I tried taking a picture of the full moon with
> the camera at prime focus (tripod, ASA 1600, 1/800, remote release
> after ~10 sec of MLU), and the results were reasonably well-exposed
> but very fuzzy (and noisy: maybe ISO 200 or 400 would be better).

Hey! I used to have a C80 when I was a kid! Tied it to a Pentax.

There is no need for that fast of ASA. I used to shoot 200 ASA and as
slow as 1/125 and get sharply exposed moon shots. That ASA speed is
probably where most of the fuzziness is coming from. Yeah, no need to
shoot at 1/800.

Also, the exposure for a mostly full moon like that is the same for a
sunny day (sunny/16).

What kind of DSLR and what mode are you in? JPEG or RAW?

look!
http://www.weasner.com/etx/guests/guests_moon.html

> I
> was using an Olympus Varimagni right angle finder attached to the
> camera. This gives a 2.5x magnification of the viewfinder, and I got
> the focus as sharp as I could. The view through the 20D viewfinder is
> horrible, though . . . I wish the screen had at least a small spot of
> fine-grained matte. There's a picture at:
>
> http://home.comcast.net/~jgates777/Moon.html
>
> I thought that perhaps the 'scope was damaged or had deteriorated in
> some way, but visual observations (30mm Kellner) look very sharp. So,
> I have a few questions:
>
> 1. Is it normal for lunar astrophotographs to have much lower
> resolution than visual images?
> 2. Since the 'scope focuses "beyond infinity", it is very
> difficult to focus on the screen in a Canon 20D. Do you have any tips
> for manual focusing with a DSLR, or is it largely trial and error
> ("Jeff R." at sci.astro.amateur recommended a Hoffman mask)?
> 3. The tripod I was using was an old, cheap Velbon (~$25 new) I
> bought for a video project, and is none too stable. If you touch the
> 'scope at all the image dances all over the place. After some
> research, I've ordered a Bogen / Manfrotto 3246 with 488RC2 Midi
> Ballhead that will be used primary for daylight photography, but it
> hasn't arrived yet. Would you folks with experience expect this to be
> any better?
>
> I understand that the 'scope is not the greatest, and this was my first
> try at lunar imaging, but my images look nowhere near as good as those
> I've seen from similar setups. I don't expect miracles, but these
> pictures are pretty sad. Any suggestions?




--

Photographs by Christian Bonanno
http://christianbonanno.com/
Anonymous
September 25, 2005 1:13:46 AM

Archived from groups: rec.photo.digital (More info?)

No, I can't use a shaky foundation as an excuse: the tripod was
sitting with legs and centerpost fully collapsed on a concrete
driveway. I was, however, shooting over the top of my house because,
like you, I am surrounded by obstructions (mostly 60' oak trees).
There was not a substantial temperature differential between indoor and
outdoor temperature at the time, although there was quite a bit of sun
load on the attic during the day and there might have been some
convection currents and turbulence above the roof.

In reality, however, I think the main problem was focus. I've not
used a D70, though I have a number of friends who own and absolutely
love them. I hope for your sake that the Nikon has a better screen
than the 20D. As I indicated above, I'll try focusing on a single
star before trying the moon the next time. I'll also try to let the
moon get higher in the sky (assuming the clouds ever break up).

It's ironic in a way, but I used to shoot my Olympus OM-1 and OM-2
cameras, and though the 20D would be a step up in quality and
flexibility. In many ways it is, but I sure do miss that bright
viewfinder and fine matte screen (when I needed it). Anyway, good luck
with your moon shots. If mine ever get better I'll repost here and
tell y'all how I did it. If they don't . . . well, there's always
macro work and the grandkids!
September 25, 2005 1:30:19 AM

Archived from groups: rec.photo.digital (More info?)

Do you use mirror lock to stop vibrations ?
September 25, 2005 5:35:08 AM

Archived from groups: rec.photo.digital (More info?)

On 24 Sep 2005 15:01:18 -0700, "jess" <jgates@erols.com> wrote:

>Well, I'm not really attempting to get into astrophotography with
>this sort of telescope. I just thought a moon shot would be
>interesting. Getting an astronomical tripod seems a bit of overkill
>unless I'm attempting guided exposures of planets and deep space
>objects. If I were going to do that, I'd probably figure out a way
>to spring for a telescope with at least 8" of aperture. But, as I
>said, I did spring for a substantially better tripod for terrestrial
>work, and hopefully that will help a bit.

You'll get 100x better shots by simply buying a Philips Tuocam Pro
webcam, stacking about 200-800 video images (30 per second)
with software like Registax and letting it process the image for
you. DSLRs are NOT a good solution for lunar or planetary
photography.
-Rich
September 25, 2005 8:25:50 AM

Archived from groups: rec.photo.digital (More info?)

On 24 Sep 2005 21:13:46 -0700, "jess" <jgates@erols.com> wrote:

>No, I can't use a shaky foundation as an excuse: the tripod was
>sitting with legs and centerpost fully collapsed on a concrete
>driveway. I was, however, shooting over the top of my house because,
>like you, I am surrounded by obstructions (mostly 60' oak trees).
>There was not a substantial temperature differential between indoor and
>outdoor temperature at the time, although there was quite a bit of sun
>load on the attic during the day and there might have been some
>convection currents and turbulence above the roof.
>
>In reality, however, I think the main problem was focus. I've not
>used a D70, though I have a number of friends who own and absolutely
>love them. I hope for your sake that the Nikon has a better screen
>than the 20D. As I indicated above, I'll try focusing on a single
>star before trying the moon the next time. I'll also try to let the
>moon get higher in the sky (assuming the clouds ever break up).
>
>It's ironic in a way, but I used to shoot my Olympus OM-1 and OM-2
>cameras, and though the 20D would be a step up in quality and
>flexibility. In many ways it is, but I sure do miss that bright
>viewfinder and fine matte screen (when I needed it). Anyway, good luck
>with your moon shots. If mine ever get better I'll repost here and
>tell y'all how I did it. If they don't . . . well, there's always
>macro work and the grandkids!


why not post your message in alt.binaries.pictures.astro.

There's some clever people there.
Anonymous
September 25, 2005 10:19:13 AM

Archived from groups: rec.photo.digital (More info?)

jess wrote:

> As I indicated above, I'll try focusing on a single
> star before trying the moon the next time. I'll also try to let the
> moon get higher in the sky (assuming the clouds ever break up).
>
If you think focusing on the moon is hard, wait until you try to focus
on a tiny star. I was thinking of doing the opposite: waiting until the
moon was in view so I could focus at it and then move over to also do
some star trails.
Anonymous
September 25, 2005 12:33:24 PM

Archived from groups: rec.photo.digital (More info?)

You may be right. I was hoping to try last night but the cloud cover
is 100% in the DC area. I'm going to try the Hoffman mask idea and
try it on a couple of stars.
Anonymous
September 25, 2005 1:55:36 PM

Archived from groups: rec.photo.digital (More info?)

jess wrote:
> You may be right. I was hoping to try last night but the cloud cover
> is 100% in the DC area. I'm going to try the Hoffman mask idea and
> try it on a couple of stars.
>
Jess,
You might try DSLRfocus. It is a free program, I believe.
You do need a laptop. It reads out the image from the camera
and displays it magnified on the screen so you can check focus.
You still manually focus, but it gives you the information you need.
I wonder about modifying one of those right angle finders to give
higher magnification for focusing.

Another alternative is some company sells a gadget you put in the
focuser (if I remember right, a knife edge at the right distance so
you can do a Foucault test on a star, a very precise way to
get focus), then lock the focuser, pull out the device, and put in
the camera. I'll try and find the link, as I was planning to
buy one myself.

Ignore the people saying the 20D is not good for astrophotography.
In fact, it is the camera of choice these days for deep sky.

Here is a moon shot, limited by lens and seeing:
http://www.clarkvision.com/galleries/gallery.astrophoto...

Roger
Anonymous
September 25, 2005 1:59:44 PM

Archived from groups: rec.photo.digital (More info?)

Rich wrote:

> On 24 Sep 2005 15:01:18 -0700, "jess" <jgates@erols.com> wrote:
>
>
>>Well, I'm not really attempting to get into astrophotography with
>>this sort of telescope. I just thought a moon shot would be
>>interesting. Getting an astronomical tripod seems a bit of overkill
>>unless I'm attempting guided exposures of planets and deep space
>>objects. If I were going to do that, I'd probably figure out a way
>>to spring for a telescope with at least 8" of aperture. But, as I
>>said, I did spring for a substantially better tripod for terrestrial
>>work, and hopefully that will help a bit.
>
>
> You'll get 100x better shots by simply buying a Philips Tuocam Pro
> webcam, stacking about 200-800 video images (30 per second)
> with software like Registax and letting it process the image for
> you. DSLRs are NOT a good solution for lunar or planetary
> photography.
> -Rich

While this method gets a good image, it would be extremely difficult
to image the whole moon at high resolution. You would end up
needing to mosaic thousands of images, a task I've not seen anyone
do. Webcams work well for small subjects, like planets (as viewed from
Earth--no wise cracks, I know planets are big; they just appear small
when viewed from Earth).

A large megapixel DSLR is the ideal tool to image subjects like the moon.

Roger
September 25, 2005 2:05:13 PM

Archived from groups: rec.photo.digital (More info?)

"jess" <jgates@erols.com> wrote in message
news:1127598136.442095.138800@f14g2000cwb.googlegroups.com...
> Nominally it's about 1000mm f11, but I have read that the effective
> aperture is more like f12.5 (as Ray Fisher suggests below). I'd
> believe you about the exposure, but I read ISO 1600, 1/1800 from the
> EXIF data and if anything the image looks underexposed.
>

1/1800 @ 1600 ISO
= 1/900 @ 800 ISO
=1/450 @ 400 ISO
=1/225 @ 200 ISO
=1/112 @ 100 ISO

from my figures of 1/250 @ f8 using 100 ISO
your f number = approx f 16, so 12.5 sounds about right.

try setting 100 or 200 ISO for better quality.

and use the mirror lock facility in the camera.

Cheers
Anonymous
September 25, 2005 6:54:06 PM

Archived from groups: rec.photo.digital (More info?)

Now that you mention it, most of the webcam images I've seen are of
relatively small objects (as viewed from Earth), and all I really
wanted was a decent picture that images the entire moon, full and/or in
various phases..

Someone in the thread mentioned the Series IV 'Stiletto' Focusers by
Stellar Technologies international' The link is

http://www.stellar-international.com/

This (or something like it) is what you may have been recalling. The
Ronchi Screen units seem interesting. Can you comment on the relative
advantages and disadvantages of each type?

I have enjoyed your posts and web site immensely; your discussions of
"digital vs. film" are a big reason I decided to take the DSLR
plunge. In fact, it was initially the two photos of the moon by
yourself and Annika (???) that led me to try the moon photo in the
first place. Now if only I could afford those long "L" lenses . .
..
September 25, 2005 7:41:46 PM

Archived from groups: rec.photo.digital (More info?)

> from my figures of 1/250 @ f8 using 100 ISO
> your f number = approx f 16

D'oh ! try f11, makes your f12.5 nearer.
Anonymous
September 25, 2005 10:31:42 PM

Archived from groups: rec.photo.digital (More info?)

Well, Mr. Clark. did indicate that the 20D is the CAMERA of choice for
deep sky work. Both webcams and DSLRs are cameras, but I think it
would be difficult to justify calling a dedicated CCD imager a
"camera", at least in the ordinary vernacular sense. And, as Mr.
Clark points out webcams are rather ill-suited to DSOs.

I don't know enough about the subject to know whether the 20D
specifically is the camera of choice, although I have read that there
are some problems with the Nikon D70 having to do with the noise
reduction circuitry, as I recall. It does, moreover, seem possible to
allow taking decent DSO images with a 20D and related DSLRs. See

M31: http://www.schweifstern.de/images-pages/deepsky/m31_ef2...
M31: http://www.schweifstern.de/images-pages/deepsky/m31_20D...
Pipe nebula: http://azastrophotography.com/Pipe%20Region.htm
Lagoon nebula:
http://www.photo.net/photodb/photo?photo_id=3708346&siz...
M31, M41, Horsehead Nebula,Great nebula in Orion; M33;
http://web.canon.jp/Imaging/astro/pages_e/13_e.html
Numerous (with Canon 10D):
http://www.ricksastro.com/Gallery/htm/10D.htm
Numerous (with Canon 10D):
http://www.astrosurf.com/afernandez/gallery/wo-10d/WO_1...
Numerous (1DS Mk2):
http://www.whirlpoolgalaxy.com/firstlight_canon_1dsmii_...

There are a lot more. Now, these may not be as good as those taken by
professional astronomers, and they may not be as good as those taken
with the most modern equipment specifically designed for deep space
astrophotography. But I would say that calling DSLRs "not
suitable" for guided imaging of DSOs is difficult to justify on the
basis of these images.

As to the Hubble, well, yeah, it takes really, REALLY good images of
DSOs. However, the $6.2 billion cost is a bit out of my price range.
My last name is Gates, but my first name isn't Bill.
Anonymous
September 26, 2005 12:33:24 AM

Archived from groups: rec.photo.digital (More info?)

jess wrote:

> Now that you mention it, most of the webcam images I've seen are of
> relatively small objects (as viewed from Earth), and all I really
> wanted was a decent picture that images the entire moon, full and/or in
> various phases..
>
> Someone in the thread mentioned the Series IV 'Stiletto' Focusers by
> Stellar Technologies international' The link is
>
> http://www.stellar-international.com/
>
> This (or something like it) is what you may have been recalling. The
> Ronchi Screen units seem interesting. Can you comment on the relative
> advantages and disadvantages of each type?

Yes that's it! Thanks for finding it.
The Ronchi ruling would be easier to focus because you don't need to
position the star exactly on a knife edge. The more expensive one
with the 300 lines/inch would probably work better. At 300 lpi, that
is a 12 micron spacing. The diffraction spot diameter of an
f/11 system is 14 microns. So with a faster system, the star image could
fall in between the rulings giving a somewhat less precise
focus. But I'm not sure if it would be enough to make a difference.
It might with the cheaper lower 180 lpi model.
The knife edge is very precise, but harder to work as precise
positioning of the star at the knife edge is necessary. A clock
drive would be necessary with the knife.

> I have enjoyed your posts and web site immensely; your discussions of
> "digital vs. film" are a big reason I decided to take the DSLR
> plunge. In fact, it was initially the two photos of the moon by
> yourself and Annika (???) that led me to try the moon photo in the
> first place. Now if only I could afford those long "L" lenses . .

Thank you. Good luck.
Roger
Anonymous
September 26, 2005 3:55:38 AM

Archived from groups: rec.photo.digital (More info?)

john_doe_ph_d <john_doe_ph_d@yahoo.com> wrote:
>jess wrote:
>
>> As I indicated above, I'll try focusing on a single
>> star before trying the moon the next time. I'll also try to let the
>> moon get higher in the sky (assuming the clouds ever break up).
>>
>If you think focusing on the moon is hard, wait until you try to focus
>on a tiny star. I was thinking of doing the opposite: waiting until the
>moon was in view so I could focus at it and then move over to also do
>some star trails.

Stars tend to be easier because they focus to a tiny point. The moon
doesn't.

--
Ray Fischer
rfischer@sonic.net
Anonymous
September 26, 2005 4:00:07 AM

Archived from groups: rec.photo.digital (More info?)

Roger N. Clark (change username to rnclark) <username@qwest.net> wrote:
>Ignore the people saying the 20D is not good for astrophotography.
>In fact, it is the camera of choice these days for deep sky.

No, it isn't. Sorry. The 20D is not suitable for deep-sky objects
that require 30-120 minute exposures. Cooled imagers with built-in
autoguiders still work much better.

As an aside, the Hubble space telescope did a deep-sky photo of the
object around the Andromeda galaxy. The combined exposure time was
about four days. THAT is deep sky.

>Here is a moon shot, limited by lens and seeing:
>http://www.clarkvision.com/galleries/gallery.astrophoto...

Nice enough moon shot, but no relation at all to deep-sky photography.

--
Ray Fischer
rfischer@sonic.net
Anonymous
September 26, 2005 4:00:08 AM

Archived from groups: rec.photo.digital (More info?)

Ray Fischer wrote:

> Roger N. Clark (change username to rnclark) <username@qwest.net> wrote:
>
>>Ignore the people saying the 20D is not good for astrophotography.
>>In fact, it is the camera of choice these days for deep sky.
>
> No, it isn't. Sorry. The 20D is not suitable for deep-sky objects
> that require 30-120 minute exposures. Cooled imagers with built-in
> autoguiders still work much better.

You mean like this:
Veil nebula: 140 minutes with 20Da (20D with IR filter removed):
http://astrophotography.aa6g.org/Astronomy/Astrophotos/...

or this:
The Pleiades, M45: 180 minutes with a 20Da:
http://astrophotography.aa6g.org/Astronomy/Astrophotos/...

See this for technical specs for low light astro work:
EOS 20D CMOS detector characterization noise and dark current
http://astrosurf.com/cavadore/APN/carac/EOS20D

Thousands and thousands of stunning deep sky astrophotos are being taken with
DSLRs. Latest data from the 20D camera is that it has 3 electron
RMS read noise at ISO 1600, an incredibly low value. No other DSLR camera
has achieved that. Most cooled CCD imagers have around 20 electron read noise.

> As an aside, the Hubble space telescope did a deep-sky photo of the
> object around the Andromeda galaxy. The combined exposure time was
> about four days. THAT is deep sky.
>
>
>>Here is a moon shot, limited by lens and seeing:
>>http://www.clarkvision.com/galleries/gallery.astrophoto...
>
> Nice enough moon shot, but no relation at all to deep-sky photography.

This thread is about photographing the moon!

If you would go to the gallery and look at other photos (or simply click the
previous button on the above page), you would see deep sky astrophotos
taken with DSLRs.

Roger
Anonymous
September 26, 2005 8:34:05 AM

Archived from groups: rec.photo.digital (More info?)

Roger N. Clark (change username to rnclark) <username@qwest.net> wrote:
>Ray Fischer wrote:
>
>> Roger N. Clark (change username to rnclark) <username@qwest.net> wrote:
>>
>>>Ignore the people saying the 20D is not good for astrophotography.
>>>In fact, it is the camera of choice these days for deep sky.
>>
>> No, it isn't. Sorry. The 20D is not suitable for deep-sky objects
>> that require 30-120 minute exposures. Cooled imagers with built-in
>> autoguiders still work much better.
>
>You mean like this:
>Veil nebula: 140 minutes with 20Da (20D with IR filter removed):
>http://astrophotography.aa6g.org/Astronomy/Astrophotos/...

10 minute exposures.

>or this:
>The Pleiades, M45: 180 minutes with a 20Da:
>http://astrophotography.aa6g.org/Astronomy/Astrophotos/...

10 minute exposures.

The 20d is a fine camera and you can do some excellent astrophotography
with it. The 20Da has some additional benefits. But it still has
more noise than cooled CCD imagers dedicated to the job.

--
Ray Fischer
rfischer@sonic.net
Anonymous
September 26, 2005 8:34:06 AM

Archived from groups: rec.photo.digital (More info?)

Ray Fischer wrote:

> Roger N. Clark (change username to rnclark) <username@qwest.net> wrote:
>
>>Ray Fischer wrote:
>>
>>
>>>Roger N. Clark (change username to rnclark) <username@qwest.net> wrote:
>>>
>>>
>>>>Ignore the people saying the 20D is not good for astrophotography.
>>>>In fact, it is the camera of choice these days for deep sky.
>>>
>>>No, it isn't. Sorry. The 20D is not suitable for deep-sky objects
>>>that require 30-120 minute exposures. Cooled imagers with built-in
>>>autoguiders still work much better.
>>
>>You mean like this:
>>Veil nebula: 140 minutes with 20Da (20D with IR filter removed):
>>http://astrophotography.aa6g.org/Astronomy/Astrophotos/...
>
>
> 10 minute exposures.
>
>
>>or this:
>>The Pleiades, M45: 180 minutes with a 20Da:
>>http://astrophotography.aa6g.org/Astronomy/Astrophotos/...
>
>
> 10 minute exposures.
>
> The 20d is a fine camera and you can do some excellent astrophotography
> with it. The 20Da has some additional benefits. But it still has
> more noise than cooled CCD imagers dedicated to the job.
>

You have conflicting statements:
1) "The 20D is not suitable for deep-sky objects"
2) "The 20d is a fine camera and you can do some excellent astrophotography"

The facts of multiple astounding astrophotos prove #2 is correct.

It matters little if you do one long exposure or multiple added exposures.
Multiple short exposures average the read noise and minimize thermal noise.
The fact that DSLRs with a different processing method get within a factor
of about 2 of a cooled dedicated $10,000 CCD is astounding, and at
more than 5 times lower cost. In fact the multiple short exposure
method has advantages: guiding errors in one frame can be thrown
out. Other events like airplanes, bumping the telescope, etc
only ruin one frame of many. CCD imagers are starting to use this
method too. The only time a cooled CCD gets MUCH fainter is when
a black and white image is done and one uses no filters over
the CCD.

But for color images, the difference between cooled CCDs and
DSLRs is very small. The DSLR is much easier to use in my opinion, as
you get full color with each image. And among DSLRs, the 20D has
the lowest measured noise and overall best noise performance
among amateur astronomers who are reporting test results on cameras.

Roger
Anonymous
September 26, 2005 2:48:10 PM

Archived from groups: rec.photo.digital (More info?)

Bob wrote:

> On 24 Sep 2005 11:05:23 -0700, "jess" <jgates@erols.com> wrote:
>
>>I have a relatively new DSLR and an old (~ 1980, black tube) Celestron
>>C90. The other light I tried taking a picture of the full moon with
>>the camera at prime focus (tripod, ASA 1600, 1/800, remote release
>>after ~10 sec of MLU), and the results were reasonably well-exposed
>>but very fuzzy (and noisy: maybe ISO 200 or 400 would be better).

I suspect the focus is off. You might find it worth practicing in the
daytime on a distant object first (or even the moon).

Full moon is more difficult to photograph well than first or last
quarter where there are sharp shadow details on the terminator to aid
focussing. You might also try putting a shadow mask with two holes at
oppposite sides in front of the scope objective as a focussing aid.

When the two spots merge the image is in focus. If you are stuck
focussing on a crude glass screen the other option is to take several
shots refocussing between each and hope that you hit the sweet spot.

My Pentax istD works pretty well with my old MTO f10 1000mm mirror lens.

Try asking on sci.astro.amateur chances are someone there has exactly
the same hardware combination and can advise on the pitfalls.

Regards,
Martin Brown
Anonymous
September 27, 2005 8:17:28 AM

Archived from groups: rec.photo.digital (More info?)

Roger N. Clark (change username to rnclark) <username@qwest.net> wrote:
>Ray Fischer wrote:
>> Roger N. Clark (change username to rnclark) <username@qwest.net> wrote:
>>>Ray Fischer wrote:
>>>>Roger N. Clark (change username to rnclark) <username@qwest.net> wrote:

>>>>>Ignore the people saying the 20D is not good for astrophotography.
>>>>>In fact, it is the camera of choice these days for deep sky.
>>>>
>>>>No, it isn't. Sorry. The 20D is not suitable for deep-sky objects
>>>>that require 30-120 minute exposures. Cooled imagers with built-in
>>>>autoguiders still work much better.
>>>
>>>You mean like this:
>>>Veil nebula: 140 minutes with 20Da (20D with IR filter removed):
>>>http://astrophotography.aa6g.org/Astronomy/Astrophotos/...
>>
>>
>> 10 minute exposures.
>>
>>
>>>or this:
>>>The Pleiades, M45: 180 minutes with a 20Da:
>>>http://astrophotography.aa6g.org/Astronomy/Astrophotos/...
>>
>>
>> 10 minute exposures.
>>
>> The 20d is a fine camera and you can do some excellent astrophotography
>> with it. The 20Da has some additional benefits. But it still has
>> more noise than cooled CCD imagers dedicated to the job.
>>
>
>You have conflicting statements:
> 1) "The 20D is not suitable for deep-sky objects"
> 2) "The 20d is a fine camera and you can do some excellent astrophotography"

There's no conflict.

>The facts of multiple astounding astrophotos prove #2 is correct.

Where are all of the 120-minute exposures?

>It matters little if you do one long exposure or multiple added exposures.

Of course it matters.

--
Ray Fischer
rfischer@sonic.net
Anonymous
September 27, 2005 8:21:18 AM

Archived from groups: rec.photo.digital (More info?)

In article <dhah4n$r06$1@bolt.sonic.net>, rfischer@bolt.sonic.net
says...
> >The facts of multiple astounding astrophotos prove #2 is correct.
>
> Where are all of the 120-minute exposures?

Does it really matter if you do twelve ten minute exposures or one 120
minute exposure? Methinks not, as the amount of light collected should
be the same.

> >It matters little if you do one long exposure or multiple added exposures.
>
> Of course it matters.

See above.
--
http://www.pbase.com/bcbaird
Anonymous
September 28, 2005 8:01:22 AM

Archived from groups: rec.photo.digital (More info?)

Brian Baird <no@no.thank.u> wrote:
> rfischer@bolt.sonic.net

>> >The facts of multiple astounding astrophotos prove #2 is correct.
>>
>> Where are all of the 120-minute exposures?
>
>Does it really matter if you do twelve ten minute exposures or one 120
>minute exposure?

Sometimes, yes.

> Methinks not, as the amount of light collected should
>be the same.

Except for the pixels that end up black because not enough photons
were detected to exceed the minimum.

--
Ray Fischer
rfischer@sonic.net
Anonymous
September 28, 2005 9:02:59 AM

Archived from groups: rec.photo.digital (More info?)

In article <dhd4ih$l0d$1@bolt.sonic.net>, rfischer@bolt.sonic.net
says...
> > Methinks not, as the amount of light collected should
> >be the same.
>
> Except for the pixels that end up black because not enough photons
> were detected to exceed the minimum.

Which is why you shoot at high sensitivities when you stack images.

Really, this isn't rocketry.
--
http://www.pbase.com/bcbaird
Anonymous
September 28, 2005 1:29:16 PM

Archived from groups: rec.photo.digital (More info?)

On Tue, 27 Sep 2005 04:21:18 GMT, Brian Baird <no@no.thank.u> wrote:

>In article <dhah4n$r06$1@bolt.sonic.net>, rfischer@bolt.sonic.net
>says...
>> >The facts of multiple astounding astrophotos prove #2 is correct.
>>
>> Where are all of the 120-minute exposures?
>
>Does it really matter if you do twelve ten minute exposures or one 120
>minute exposure? Methinks not, as the amount of light collected should
>be the same.

Beyond the time required to fully record the image, keeping
the lens open on a digital camera carries no benefit -- the photons do
not accumulate over time as they do on film. By making ten shorter
shots, you can superimpose and average out the information from
multiple "as exposed as they can get" shots.

>
>> >It matters little if you do one long exposure or multiple added exposures.
>>
>> Of course it matters.
>
>See above.
Anonymous
September 29, 2005 5:18:04 AM

Archived from groups: rec.photo.digital (More info?)

kashe@sonic.net wrote:
> On Tue, 27 Sep 2005 04:21:18 GMT, Brian Baird <no@no.thank.u> wrote:
>
>
>>In article <dhah4n$r06$1@bolt.sonic.net>, rfischer@bolt.sonic.net
>>says...
>>
>>>>The facts of multiple astounding astrophotos prove #2 is correct.
>>>
>>>Where are all of the 120-minute exposures?
>>
>>Does it really matter if you do twelve ten minute exposures or one 120
>>minute exposure? Methinks not, as the amount of light collected should
>>be the same.

This is correct. If you get 100 photons (electrons) per 10 minute exposure,
then after 12 exposures added together you have a total of
1200 photons (electrons). The problem with multiple exposures is read noise.

Say the read noise is 3 electrons (the read noise of the 20D),
then the final noise accumulated read noise is 3 * square root 12
= 10.4 electrons. But the noise from 1200 electrons is
square root 1200 = 34.6 electrons, so photon noise dominates.
Total noise is sqrt(10.4^2 + 34.6^2) = 36.1 electrons.
>
>
> Beyond the time required to fully record the image, keeping
> the lens open on a digital camera carries no benefit -- the photons do
> not accumulate over time as they do on film.

This is correct. Film loses charged state of the photosensitive grains,
so photons do not accumulate linearly. This is called reciprocity
failure. Digital sensors do not suffer from that problem so are
quite superior in that regard.


> By making ten shorter
> shots, you can superimpose and average out the information from
> multiple "as exposed as they can get" shots.

Huh?

>>>>It matters little if you do one long exposure or multiple added exposures.
>>>
>>>Of course it matters.
>>
>>See above.

Yes, the statement
"It matters little if you do one long exposure or multiple added exposures."
is correct, assuming read noise is small, which it is on good cameras
like the 20D.

Jeez, I was out for 2 days (calibrating a NASA sensor) and this thread
is still going.

Roger
Anonymous
September 29, 2005 5:26:32 AM

Archived from groups: rec.photo.digital (More info?)

Ray Fischer wrote:

> Brian Baird <no@no.thank.u> wrote:
>
>>rfischer@bolt.sonic.net
>
>
>>>>The facts of multiple astounding astrophotos prove #2 is correct.
>>>
>>>Where are all of the 120-minute exposures?
>>
>>Does it really matter if you do twelve ten minute exposures or one 120
>>minute exposure?
>
>
> Sometimes, yes.
>
>
>> Methinks not, as the amount of light collected should
>>be the same.
>
>
> Except for the pixels that end up black because not enough photons
> were detected to exceed the minimum.
>

As long as you digitize the noise there is no minimum. In any
one exposure, the signal can be less than one DN (data number)
per exposure. Then given enough exposures you can dig the signal
out of the noise by averaging multiple exposures. We are doing this
right now with the NASA Cassini mission to measure faint rings.
The Cassini VIMS instrument is limited to about 1 second exposures
or the infrared channels (5 micron wavelengths) saturate due
to thermal emission inside the instrument running at 140 kelvin.
We do hour plus integrations averaging thousands of exposures.
Signal levels 0.1 DN/exposure and lower have been extracted to give a
signal-to-noise ratio good enough to identify composition from the
spectrum and produce images that show the extent of the rings.

Roger
!