Re: [OT] Telescope
- From: Tom McDonald <tmcdonald2672@xxxxxxxxxxx>
- Date: Mon, 05 Jan 2009 09:14:49 -0600
Yowie wrote:
"Tom McDonald" <tmcdonald2672@xxxxxxxxxxx> wrote in message
news:uq38l.53370$lX6.32304@xxxxxxxxxxxx
Yowie wrote:I mentioned that I was looking at getting a telescope here recently.Great news! Now a couple of questions:
Problem solved: my husband got me one for Christmas - a Celestron
AZ76 (Newtonian). It prestty much bottome of the range but it does
the job and does it much better than my old Tesco one.
One problem I have with it is the tripod being unstable, such that
the tripod often moves rather than the scope itself, but my biggest
problem by far with viewing the night sky has nothing to do with the
scope but my seeming irresistability to all forms of biting insect.
I can only stand to be out on a summer night for about 15 minutes
before the itching becomes intolerable and I have to retreat inside.
There are other niggles, but its still a cool 'scope and the moon
looks wonderful through it.
Is this the scope you got:
PowerSeeker 76mm x 700mm alt-azimuth reflector
* Alt-azimuth mount with adjustable height aluminium tripod
and accessory tray
* 5 x 24 finderscope
* 3x Barlow lens
* 4mm + 20mm 1.25" eyepieces
* "The Sky - Level 1" CD-ROM included
Thats the one!
If so, then you might try using the scope with the legs not fully
extended, and observing while sitting. This could help steady the
mount.
Did that - helps enormously with my back, didn't helP so much moving the
scope around. The other niggle is that the finderscope doesn't directly line
up scope proper such that I have to look at anything, I first haveto place it
int he finderscope at about the 2pm position, 2/3 of the radius away from
the intersection of the cross hairs. OK for the moon, exceptionally annoying
for points like stars. I don't know whether I've mounted it wrong or whether
its adjustable.
What kind of eyepieces do you have? Are they Huygens, or Kellner,
or Plossel? (They may be marked with the name next to the size in
mm; or they may have an initial next to the size in mm.)
If they are Huygens, unless you have very good eyesight, you will
probably find it easier to get higher power using the 20mm
eyepiece with the Barlow lens than with the 4mm eyepiece.
I have no idea, they're whatever came with the scope and are simply marked
'20mm' and '4mm'. I had no problem viewing the moon with the 4mm one, but
found that it moved through the field of vision annoyingly quickly and went
back to just using the 20mm one - with which the whole of the moon is
visible in the field of view. Looks magnificent too - any idea how to get a
decent photo of the image using a relatively cheap point-and-shoot digital
camera?
Yup. The easiest is afocal photography:
http://www.astronomyforbeginners.com/astrophotography/afocal.php
You basically hold the camera square on to the eyepiece and snap a picture. Don't use the flash!
There are purpose-made rigs for holding a camera so that it is properly positioned for taking this kind of image. Here's a link to one version:
http://www.telescope.com/control/product/~category_id=photo_accessories/~pcategory=astro-imaging/~product_id=05228
Or:
http://tinyurl.com/92wt8w
The great advantage of digital cameras is that you don't have to pay for the film you would inevitably mess up trying to get the hang of hand-held afocal photography through a telescope. If you want to spring for the universal camera mount (probably costing a quarter or more of the price of the scope itself!), you can more reliably get images. But you may find the money better spent on better eyepieces, a more sturdy tripod, or an equatorial mount for your scope.
Another way to take pictures is 'prime focus' photography; but for this to work well, you need to have an SLR camera and the appropriate "T" ring to attach to the telescope. Probably not worth the price for you, and your scope may not be one that can actually mount a "T" ring anyway. This process does not allow the use of eyepieces (the camera is the eyepiece here); and what you have at the end is a telephoto lens of the same length as the focal length of your scope. In this case, you'd have a 700mm telephoto lens.
You might try to take snaps at prime focus. Just remove the eyepiece and line up the camera with the light path.
http://www.astronomyforbeginners.com/astrophotography/prime-focus.php
Another option is called 'eyepiece projection'. This involves an adapter that connects an SLR camera to the outside of the eyepiece tube, and allows you to use your telescope's eyepieces to project a magnified image onto the camera's film or CCD. Again, this requires an SLR, a "T" ring, and the eyepiece projection adapter. By the time you've gotten all the appropriate equipment for this, you've spent more than the price of the scope.
Afocal is probably your best bet. You'll probably only be able to get images of the moon and other very bright things; but it's cheap and fun to play with.
<snip>
--
Tom "Go Pack" McDonald
.
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