Yet Another Astral Photography Question

[w_tothe]

Yup, I'm having trouble again. :). Here's my situation. My last

question was in regards to my camera not taking pictures when i had

the Lens off. That question was answered very promptly and got it

too work right when i got home. BUT, when i have the Camera Attached

to the Telescope and lets say i'm looking at the moon, the moon is

not focused. I've adjusted the focus on the telescope and even

adjusted how far telescope lens is dropped in the 'scope, but still

get a blurry moon in the viewfinder.

 

I'm thinking that either:

A) I need a new lens for my telescope.

B) Condensation could be building up on something (about 40 or so

degrees here)

C) My telescope is just a POS

or

D) My Camera is just a POS.

 

Any Ideas/Suggestions??

Thanks in Advance.

[danny_spence]

Here are a few possibilities ... Can you get a sharp image looking through the regular eyepiece on the telescope? If it's not clear and sharp here, the camera won't fare any better. When attached to the telescope the image in the camera's viewfinder will be considerably darker and slightly lower in contrast than what you can see with the telescope eyepiece. Also, any high clouds will utterly destroy a clear image of the night sky. Are you staying outside the entire time with your equipment or are you going in and out several times with your gear? Going straight from the outside cold to your warm house can cause condensation to form on any cold surface.

[stephen hazelton]

The most likely problem is simply one of spacing, of getting your camera body in the right place. Without knowing the setup (not a telescope expert here), I can't offer much more advice on that topic.

 

"I need a new lens for my telescope." New lenses, new telescopes, new cameras, won't make the picture focused if the spacing isn't right. If these were your problem, you'd be seeing lower quality photos, but probably couldn't tell the difference through the viewfinder. You might try the set-up during the day. If you focused much closer than infinity, then something should be in focus- swing the rig around area, see if anything closer than a star pops into focus.

 

"Condensation could be building up on something" When you take the camera off, is there condensation everywhere? If you've used the camera out there and used the telescope out there, and don't get gobs of condensation, then you won't magically get condensation when you put them together.

 

"My telescope is just a POS or D) My Camera is just a POS." As above, if this was the case, you'd be complaining about your photos, not getting the image focused in the first place.

[jerry thirsty]

Is your telescope a Newtonian design? Many of those do not have enough focus travel for a camera. Several years ago I had one, and it wasn't possible to rack the focuser in far enough to bring the camera to focus. What I ended up doing was installing longer push/pull bolts on the primary mirror, thus moving the primary mirror an inch or more up the telescope tube toward the open end. This in turn moved the focal point of the telescope further out so that the focuser could rack in far enough for the camera. Of course, if you install different bolts on the primary you will have to re-collimate the telescope optics.

[bert_krages1]

This sounds like a problem with insufficient back focus on the telescope. There are a couple of possibilities to try. One is using a barlow lens in front of the camera adapter. Another is to get an <A HREF="http://www.telescope.com/shopping/product/detailmain.jsp?itemID=65&itemType=PRODUCT&iMainCat=6&iSubCat=29&iProductID=65">adaptor</A>

to do afocal photography. Otherwise, you will need to use another telescope. If you are interested in other ways to do astrophotography (e.g., camera and tripod), you might want to look at my book <A HREF="http://www.krages.com/hb.htm">Heavenly Bodies: The Photographers Guide to Astrophotography</A>.

[imaginator]

Give us a break... what kind of telescope are you using?

[w_tothe]

It's a Field Vision Reflector Telescope. Focal Length = 900mm, Aperture = 114mm (4.5inch), Resolving power of about 1". The actual length of the tube is a lil shy of 3 feet.

The current camera adaptor is <a href>http://shopping.discovery.com/stores/servlet/ProductDisplay?catalogId=10000&storeId=10000&langId=-1&productId=10879&rel_productId=10181&categoryId=11683&interCategoryId=22518&parent_category_rn=1109 </a href> (but it's the 1.25" barrel)

[Mike Gammill]

The type of telescope you describe probably could not have the primary mirror moved forward the needed amount without major modification. You could go the afocal route (try holding the camera body over the eypiece to see if you get a sharp image) If you are trying prime focus photography (using telescope as a 900mm tele) but can't get a sharp image, see if you can find a barlow lens with T-threads. It might allow your telescope to reach focus with a camera and give you a bigger image as well.

BTW, if you're interested primarily in photographing the moon, some telescope dealers are heavily discounting the older Meade ETX 90 (has a 1300mm focal length 90mm mirror) It's a Maksutov Cassegrain (fancy mirror lens) with a built in motor drive for tracking. I've seen them go for under $200. Lots of focus travel.