Celestron C-5 quality?

[kurtstone]

I was recently given an orange tube Celestron c-5 that has not been used for at least 15 years. I have a drebel and would like to use this celestron for still wildlife. I have no experience with telescopes - I think it needs to be cleaned. Any suggestions for how to get the scope in good condition?

How about the quality - anyone using one of these?
Basic stats:
Objective Diameter: 127-mm
Focal Length (typical, w/diagonal): 1347-mm
Limiting Magnitude: 13.76
Theoretical Diffraction Limit: 0.892 arc-sec

[CyberDyneSystems]

Wel,. I would vertainly not recomend this option for wildlife shooting (In fact there was another post just today :) )

...but that is if the question invloved BUYING a scope,. :)

Since you allready have one,. 1347MM!!!!!!!! :shock:

Wow,. definately worht a try,. and for Astro photography!! It is certainly the right tool.

Definately worth tryingindeed. I don't know about the cleaning. but what you first need to find out is how to get this thing atached to your Drebel to it.

Most all of these scopes have a t mount thread. You will need either the T-mount adapter and an EOS adapter,. or just the T-mount to EOS adapter. The T-mount to EOS adapter should only be about $10.00 - $20.00 at a camera store,. I have a tiny Celestron that came with the other part, so you may have it too.. other scopes I have seen have the T-mount threads built right in! All in all, it is pretty cheap to get it up and running...

I'd see if you can get the parts and try it out before looking into cleaning it.

[RichardSimon]

It sounds like the C5 is similar, optically, to the Meade 125EX that I have. I have put my 10D on the 125EX, and I can make the following observations:

- www.scoptronix.com probably sells the adapter(s) you need (I am not affiliated with them in any way). You probably need a C5 to T Thread adapter, then a t-threaded adapter for the Canon. Maybe $20 each? Maybe you already have the first one?

- The C5 is probably either Maksutov or Casegrain optics, meaning 2 bounces. More than likely, the 'scope doesn't have a modern antireflective coating on the optics. Between that and the size of the secondary mirror, the contrast will be low, compared to what a good telephoto gives you, and the thing will be very sensitive to glare. You are going to need a long black tube in front to reduce stray light in many situations.

- Focus is very tricky with scope plus camera, and you will be working at f/11, where things are dim and the autofocus (obviously!) won't work. Practice will help, as will bright sunny days.

- You should try to verify the alignment of the optics, especially if the secondary mirror is adjustable (likely if it is a Casegrain). I'm sure there are lots of places on the 'net to give you how-to advice in this area. For example, http://www.pietro.org/Astro_C5/c5_nexstar.htm seems to have lots of useful info.

- Cleaning telescope optics is something to be done with great caution. You should be careful, if disassembly is required, that you know how to reassemble and and align the optics. It may not be too difficult - just read a little before you do it! As far as the need for cleaning: the tube is closed but not sealed; every time an eyepiece is changed is another chance for a little dust to get into the tube. Small amounts of dust will increase the amount of light scattering, reducing image contrast. There are lots of suggestions out there for lens cleaning; be careful, whatever you do, not to damage the optics and make thigs worse! In particular, the aluminum coatings inside the tube are probably not overcoated, and are very easy to scratch.

- You are obviously going to need a solid tripod. At these magnifications, you may also need to use the mirror lockup feature on the 10D - the mirror moving up can induce substantial vibrations.

To give you an idea of what can be done, the photo below is of my daughter and her boyfriend. The picture was taken of a moving target(!) from about 100m away. The high f/ ratio (f/15 in this case) required a 1/500 sec exposure with ISO 400. I have posted both a reduced full frame, and a full resolution version of a selected area. There are several things to note:
- The contrast of this image is low, with the effects of the mirror optics apparent in the histogram (no really dark areas).
- Focus, motion blur, and/or atmospheric bluring have softened the image so that some sharpening is still needed for a final image. Given the conditions (a warm, breezy beach), the resolution of the image is probably much lower than the theoretical limit of the optics.
- I probably needed more of a lens shade in front of the telescope, to reduce the amount of scattered light in the image.

On the other hand - this is an image that is especially liked in my family, and there is no way that I could have gotten this candid shot without being a long ways away!

Have fun with the C5....

Richard Simon

First image: Entire frame, resized to show everything
Subject distance ~100m (entire frame is about 0.65 degrees wide)
Meade ETX125 (1900mm, f/15) ISO 400 1/500sec
Processed using high sharp, low contrast, custom white balance with FVU
http://home.earthlink.net/~rsimondsl/data/FullFrame_Resampled.JPG

Second image: Selected portion of the image, full resolution
http://home.earthlink.net/~rsimondsl/data/Selected_FullResolution.JPG