Fork Mounts, Equatorial Wedges & Astrophotography?

Hey all, I've been looking at the variety of scopes out there with an alt-az
fork mount, and available equatorial wedge (like the Meade
EXT-70/90/105/125, similar models from Celestron, etc.)

Now, my understanding is that one big problem with alt-az mounts that track
is for long-exposure astrophotography - while it will follow the rotation of
the target around Polaris, it won't deal with the image appearing to revolve
in the viewfinder, and therefore creating a streaking affect on film. Is
this something that using an equatorial wedge will take care of?

From what I've read, the equatorial wedge allows these scopes to rotate only
on their azimuth, removing the need to change their elevation on their
"altitude" axis. Are they basically being set up so they're on the same
plane as the objects you're observing? If so, are they then viewing that
target as if it were moving in a straight line across the sky, with no
apparent revolution?

Basically, here's the deal. I'm fairly new to astronomy, and
astrophotography, and was considering picking up something with a better
aperture than the 50mm f/1.7 camera lens I've been using on the Maxxum 5 I
recently picked up. While it's a pretty decent lens, it only has a 29mm
maximum aperture. While wide-field images of a few seconds are pretty easy
to do (I've got some older ones with an X-700 up on my site, but I've got
some better ones I took with the Maxxum waiting to be scanned), getting
narrower fields of view and better magnification isn't really workable with
my current setup, which my eclipse photos show pretty handily - the moon is
tiny, because I had only 100mm of focal length.

So, my goals are something with better light gathering, that might help me
image some of the really faint objects out there. Tracking would be nice,
to get star fields without star trails, and maybe get things like nebulas,
galaxies, etc. Some level of magnification would be nice, when I'm trying
to take pics of the planets, or the Moon, etc.

My price range basically sucks at the moment. I can probably spring up to,
oh, $300 or so over the next couple months. More than that, and we're
talking 1-2 months additional per $100. I understand this means I won't
have the best gear out there. Heck, I'm looking at tepid, mediocre gear,
most likely. I understand and accept that - this isn't going to be the last
scope I buy, and financial issues will not be an issue forever - a year or
two from now, $1000-$2000 for a rig probably won't concern me.

So, my options:

First, would be something like the EXT-90, waiting a couple of extra months
or so to do that. This is where that whole equatorial wedge combined with a
fork mount comes into play.

Next would be something similar to the Celestron Firstscope 114EQ. Of
course, I've never used a German equatorial before, so I'm not sure how the
learning curve is. For one thing, what do you do when the majority of the
things you want to look at are in the opposite direction from Polaris?
Example: most times I have available to observe, Orion or the Pleiades (two
of my favorites to look at), aren't near Polaris - I'd have to point the
scope in the opposite direction.

Now, option three is just....weird. Anyone have any experience with Rubinar
lenses or telescopes (examples he
http://www.rugift.com/photocameras/m...ras_lenses.htm and also
he http://www.lzos.ru/tovnp/teles/teleng.htm) - they make 1000 mm focal
length f/10 and 500 mm focal length f/5.6 Maksutov-Cassegrain lenses that,
with an adaptor, will fit my camera easily. Both have available adaptors to
let you hook up eyepieces and use them as telescopes. Combine one with a
German equatorial from Orion, for example, a motor for tracking, etc, and I
can get a scope with halfway-decent magnification and a tracking mount for a
good price. Of the two, I'd lean more towards the 500mm, even though it's a
bit smaller in aperture, because it'd also work well in daylight as a
supertelephoto lens for my camera, whereas the 1000mm is a bit too big for
that. This option's nice because I can do it piecemeal, and get out the
door at a fairly low price.

OK, I think I've gone on long enough. Any advice would be welcome.

--Jason
http://www.websown.com/~jdonahue/astro/astrophoto.htm

"Jason @websown .com" jdonahueantispamantispam wrote in message
...
Hey all, I've been looking at the variety of scopes out there with an
alt-az
fork mount, and available equatorial wedge (like the Meade
EXT-70/90/105/125, similar models from Celestron, etc.)

Now, my understanding is that one big problem with alt-az mounts that
track
is for long-exposure astrophotography - while it will follow the rotation
of
the target around Polaris, it won't deal with the image appearing to
revolve
in the viewfinder, and therefore creating a streaking affect on film. Is
this something that using an equatorial wedge will take care of?
Yes.

From what I've read, the equatorial wedge allows these scopes to rotate
only
on their azimuth, removing the need to change their elevation on their
"altitude" axis. Are they basically being set up so they're on the same
plane as the objects you're observing? If so, are they then viewing that
target as if it were moving in a straight line across the sky, with no
apparent revolution?
The terms are Ra and Dec, when equatorially mounted. Technically, the
equatorial wedge, is to my mind a misnomer. It is really a 'polar wedge'
(this is why you refer to such mountings as polar aligned). If you imagine
that you are standing on the Earth, exactly at the true (not magnetic) North
pole. Here you are standing 'on' the axis about which the planet revolves
(remember the skies apparent motion, is being created by the world rotating,
not any 'real' motion up there). Hence if you now put a clock flat on the
ground, and set it to turn one revolution in each sidereal day (about four
secods faster than a normal clock), it's hour hand, will remain pointing at
exactly the same point in the sky, with no other motion being needed. Put an
angled pointer on the hour hand, and aim it at a star, and again the pointer
will remain correctly aimed as the night passes.
This is the basis of wedge aligning. The scope is mounted at an angle, so
it's base is parallel to the equator (or as if it was sitting on a flat
table at the North pole). Mounted like this, the motion to match the stars,
is rotation on the Ra axis, while the one needed to point to different parts
of the sky, is the Dec axis.

Basically, here's the deal. I'm fairly new to astronomy, and
astrophotography, and was considering picking up something with a better
aperture than the 50mm f/1.7 camera lens I've been using on the Maxxum 5 I
recently picked up. While it's a pretty decent lens, it only has a 29mm
maximum aperture. While wide-field images of a few seconds are pretty
easy
to do (I've got some older ones with an X-700 up on my site, but I've got
some better ones I took with the Maxxum waiting to be scanned), getting
narrower fields of view and better magnification isn't really workable
with
my current setup, which my eclipse photos show pretty handily - the moon
is
tiny, because I had only 100mm of focal length.

So, my goals are something with better light gathering, that might help me
image some of the really faint objects out there. Tracking would be nice,
to get star fields without star trails, and maybe get things like nebulas,
galaxies, etc. Some level of magnification would be nice, when I'm trying
to take pics of the planets, or the Moon, etc.

My price range basically sucks at the moment. I can probably spring up
to,
oh, $300 or so over the next couple months. More than that, and we're
talking 1-2 months additional per $100. I understand this means I won't
have the best gear out there. Heck, I'm looking at tepid, mediocre gear,
most likely. I understand and accept that - this isn't going to be the
last
scope I buy, and financial issues will not be an issue forever - a year or
two from now, $1000-$2000 for a rig probably won't concern me.

So, my options:

First, would be something like the EXT-90, waiting a couple of extra
months
or so to do that. This is where that whole equatorial wedge combined with
a
fork mount comes into play.

Next would be something similar to the Celestron Firstscope 114EQ. Of
course, I've never used a German equatorial before, so I'm not sure how
the
learning curve is. For one thing, what do you do when the majority of the
things you want to look at are in the opposite direction from Polaris?
Example: most times I have available to observe, Orion or the Pleiades
(two
of my favorites to look at), aren't near Polaris - I'd have to point the
scope in the opposite direction.

Now, option three is just....weird. Anyone have any experience with
Rubinar
lenses or telescopes (examples he
http://www.rugift.com/photocameras/m...ras_lenses.htm and also
he http://www.lzos.ru/tovnp/teles/teleng.htm) - they make 1000 mm focal
length f/10 and 500 mm focal length f/5.6 Maksutov-Cassegrain lenses that,
with an adaptor, will fit my camera easily. Both have available adaptors
to
let you hook up eyepieces and use them as telescopes. Combine one with a
German equatorial from Orion, for example, a motor for tracking, etc, and
I
can get a scope with halfway-decent magnification and a tracking mount for
a
good price. Of the two, I'd lean more towards the 500mm, even though it's
a
bit smaller in aperture, because it'd also work well in daylight as a
supertelephoto lens for my camera, whereas the 1000mm is a bit too big for
that. This option's nice because I can do it piecemeal, and get out the
door at a fairly low price.

OK, I think I've gone on long enough. Any advice would be welcome.

--Jason
http://www.websown.com/~jdonahue/astro/astrophoto.htm
Realistically, I'd avoid any of the scopes you mention for photography...
The problem is that to take good pictures, requires the mount to be _very_
rigid. Most of the cheaper scopes do not approach this requirement, even
remotely (one 'rule of thumb', is to halve the useable load on a mount for
photography). You can take photographs through these scopes, but trying to
take even slightly longer exposure astophotographs, will leave you
screaming.
One of the best 'small' mounts, in terms of the accuracy of it's gears, is
the Vixen GP-DX mount. Start by being prepared to go 'second hand', and see
if you can obtain one of these. Add a tracking motor, and then even with
your current lens, be amazed at how much 'deeper' your images can go,
showing widefield features superbly.
Going 'longer' with the lens, then allows more detail to be seen, but adds
its own problems. The first is that many camera lenses, will show
significant chromatic aberration on astronomical objects. Catadioptic lenses
have less problems in this regard than refractor designs. The second link
you give, shows a lens that might well take some quite reasonable pictures.
However another problem then rears it's ugly head. No mount is perfect.
Unless the telescope is absolutely accurately aligned, and the mount is
perfect, as exposure times, and focal lengths increase, faults in the
tracking will start to appear on the pictures. The 'solution' to this, is to
guide the camera. With this, some light (either using an 'OAG', a prism that
steals a small amount of light from the edge of the field of view), or a
seperate 'guide' telescope attached to the same mount, is fed to either a
small CCD camera, with software to guide the scope, or to an eyepiece, with
an illuminated crosshair, allowing the photographer to apply the tiny
'tweaks' needed for perfect guiding. So you need to consider how you are
going to guide, as part of the system.
If there is an astronomy club near you, it'd be well worth going along.
Firstly, sometimes old equipment will be for sale. Secondly, you may well
find that you can try some of the systems and techniques before spending
money, and save a lot of waste...
It is worth saying, that there are some very 'budget' solutions,if you are
at all mechanically minded. Do a web search for 'barn door tracker'. This is
a system using a hinged board, operated by a motor, that can be built for a
very few dollars, and allows reasonable duration photography at medium focal
lengths (don't try pushing up to 1000mm, without guiding - 200mm is a more
reasonable scale). If you can build one of these, combined with a slightly
longer focal length lens, you may be suprised at just how good the images
look. :-)

Best Wishes

Just my 2 cents worth.

If your budget starts at $300, you might want to put the kaibosh on the
astrophotography plan. In my experience astrophotography is similar to the
classic definiton of a boat, "a hole in the water you pour money into."

"Jason @websown .com" jdonahueantispamantispam wrote in message
...

Basically, here's the deal. I'm fairly new to astronomy, and
astrophotography, and was considering picking up something with a better
aperture than the 50mm f/1.7 camera lens I've been using on the Maxxum 5 I

*snip*

My price range basically sucks at the moment. I can probably spring up
to,
oh, $300 or so over the next couple months. More than that, and we're
talking 1-2 months additional per $100. I understand this means I won't
have the best gear out there.

You said you are new to astronomy... I recommend you get yourself a decent
aperture (6-8") Dob (fairly close to your $300 budget) and spend the next
year or two learning the sky... then when you have (multi) thousands of $ to
spend, you can play astrophotography.

If you can, go for an Orion (US not UK) ED80mm refractor. This is of
excellent quality but there is a waiting list. Look for Orion ED80 on Google
to get some reviews.

MarkDJ


"Jason @websown .com" jdonahueantispamantispam wrote in message
...
Hey all, I've been looking at the variety of scopes out there with an
alt-az
fork mount, and available equatorial wedge (like the Meade
EXT-70/90/105/125, similar models from Celestron, etc.)

Now, my understanding is that one big problem with alt-az mounts that
track
is for long-exposure astrophotography - while it will follow the rotation
of
the target around Polaris, it won't deal with the image appearing to
revolve
in the viewfinder, and therefore creating a streaking affect on film. Is
this something that using an equatorial wedge will take care of?

From what I've read, the equatorial wedge allows these scopes to rotate
only
on their azimuth, removing the need to change their elevation on their
"altitude" axis. Are they basically being set up so they're on the same
plane as the objects you're observing? If so, are they then viewing that
target as if it were moving in a straight line across the sky, with no
apparent revolution?

Basically, here's the deal. I'm fairly new to astronomy, and
astrophotography, and was considering picking up something with a better
aperture than the 50mm f/1.7 camera lens I've been using on the Maxxum 5 I
recently picked up. While it's a pretty decent lens, it only has a 29mm
maximum aperture. While wide-field images of a few seconds are pretty
easy
to do (I've got some older ones with an X-700 up on my site, but I've got
some better ones I took with the Maxxum waiting to be scanned), getting
narrower fields of view and better magnification isn't really workable
with
my current setup, which my eclipse photos show pretty handily - the moon
is
tiny, because I had only 100mm of focal length.

So, my goals are something with better light gathering, that might help me
image some of the really faint objects out there. Tracking would be nice,
to get star fields without star trails, and maybe get things like nebulas,
galaxies, etc. Some level of magnification would be nice, when I'm trying
to take pics of the planets, or the Moon, etc.

My price range basically sucks at the moment. I can probably spring up
to,
oh, $300 or so over the next couple months. More than that, and we're
talking 1-2 months additional per $100. I understand this means I won't
have the best gear out there. Heck, I'm looking at tepid, mediocre gear,
most likely. I understand and accept that - this isn't going to be the
last
scope I buy, and financial issues will not be an issue forever - a year or
two from now, $1000-$2000 for a rig probably won't concern me.

So, my options:

First, would be something like the EXT-90, waiting a couple of extra
months
or so to do that. This is where that whole equatorial wedge combined with
a
fork mount comes into play.

Next would be something similar to the Celestron Firstscope 114EQ. Of
course, I've never used a German equatorial before, so I'm not sure how
the
learning curve is. For one thing, what do you do when the majority of the
things you want to look at are in the opposite direction from Polaris?
Example: most times I have available to observe, Orion or the Pleiades
(two
of my favorites to look at), aren't near Polaris - I'd have to point the
scope in the opposite direction.

Now, option three is just....weird. Anyone have any experience with
Rubinar
lenses or telescopes (examples he
http://www.rugift.com/photocameras/m...ras_lenses.htm and also
he http://www.lzos.ru/tovnp/teles/teleng.htm) - they make 1000 mm focal
length f/10 and 500 mm focal length f/5.6 Maksutov-Cassegrain lenses that,
with an adaptor, will fit my camera easily. Both have available adaptors
to
let you hook up eyepieces and use them as telescopes. Combine one with a
German equatorial from Orion, for example, a motor for tracking, etc, and
I
can get a scope with halfway-decent magnification and a tracking mount for
a
good price. Of the two, I'd lean more towards the 500mm, even though it's
a
bit smaller in aperture, because it'd also work well in daylight as a
supertelephoto lens for my camera, whereas the 1000mm is a bit too big for
that. This option's nice because I can do it piecemeal, and get out the
door at a fairly low price.

OK, I think I've gone on long enough. Any advice would be welcome.

--Jason
http://www.websown.com/~jdonahue/astro/astrophoto.htm




---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
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"Jason @websown .com" jdonahueantispamantispam wrote in message
...
Hey all, I've been looking at the variety of scopes out there with an
alt-az
fork mount, and available equatorial wedge (like the Meade
EXT-70/90/105/125, similar models from Celestron, etc.)

Now, my understanding is that one big problem with alt-az mounts that
track
is for long-exposure astrophotography - while it will follow the rotation
of
the target around Polaris, it won't deal with the image appearing to
revolve
in the viewfinder, and therefore creating a streaking affect on film. Is
this something that using an equatorial wedge will take care of?

Exactly. That's its purpose.

With an equatorial wedge, the telescope rotates around only one axis, which
is parallel to the earth's axis. All parts of the telescope remain in the
same orientation relative to the stars as the rotation proceeds.

Let me suggest a couple of books (which I happen to have written) -- How to
Use a Computerized Telescope (which covers astrophotography briefly, along
with other telescope details) and Astrophotography for the Amateur. A few
dollars spent on a book can save you hundreds on equipment.


--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope

My price range basically sucks at the moment. I can probably spring up to,
oh, $300 or so over the next couple months. More than that, and we're
talking 1-2 months additional per $100. I understand this means I won't
have the best gear out there.

It is not really possible to buy a scope and mount that are capable of doing
astrophotography for $300. For $300 you can buy a scope that does a decent job
visually but astrophotography requires not only a much more accurate mount, but
a significant amount of accessories.

A few random comments:

1. Avoid the ETX-70.

2. People do photography with the ETX-90 but with the slow focal ratio
exposures are long and the mount marginal.

3. www.astropix.com
http://www.astropix.com/HTML/I_ASTROP/TOC_AP.HTM

4. Consider buying a scope that will allow you to enjoy the visual aspects of
astronomy and later move on to photography once you have more experience.

Jon

On Sat, 22 Nov 2003 01:07:34 -0800, "Jason" ...reflected:

snip

Next would be something similar to the Celestron Firstscope 114EQ. Of
course, I've never used a German equatorial before, so I'm not sure how the
learning curve is. For one thing, what do you do when the majority of the
things you want to look at are in the opposite direction from Polaris?
Example: most times I have available to observe, Orion or the Pleiades (two
of my favorites to look at), aren't near Polaris - I'd have to point the
scope in the opposite direction.

That's precisely the beauty and attraction of the German Equatorial
Mounting(GEM), for with it you may point any telescope mounted thereupon
anywhere.

snip

Alan

(Jon Isaacs) wrote in message ...

4. Consider buying a scope that will allow you to enjoy the visual aspects of
astronomy and later move on to photography once you have more experience.

Do some wide-field fixed tripod shots. Spend ten bucks
and build a barndoor tracker. The experience will
serve you well.

You'll get really neat pictures, and will be able to
tell, pretty quickly, if astrophotography is for you.
While the pictures can be wonderful, the act of actually
taking them requires fairly serious patience.

In other words, it's like watching paint dry, with the
added bonus of freezing your backside off while you're
doing it... :-)

Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89mg pied a terre..."
ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte

"Laura Halliday" wrote in message
om...

Do some wide-field fixed tripod shots. Spend ten bucks
and build a barndoor tracker. The experience will
serve you well.

You'll get really neat pictures, and will be able to
tell, pretty quickly, if astrophotography is for you.
While the pictures can be wonderful, the act of actually
taking them requires fairly serious patience.

I agree wholeheartedly. That's how I got started, and it's why my book
starts with a lot of detail on such things. With very little equipment, you
start encountering the same technical issues and skill-building
opportunities that you would encounter with the very biggest telescopes.
Either you like it or you don't. And you can get beautiful pictures with
simple equipment, particularly in the winter -- Orion is a very fine
fixed-tripod target.

--
Clear skies,

Michael Covington -- www.covingtoninnovations.com
Author, Astrophotography for the Amateur
and (new) How to Use a Computerized Telescope