Off axis guider

[scottyiu]

Probably a very basic question... But I have a Celestron 127 MAK, will that work with a off axis guider? Thanks...

[sxinias]

Hi Scotty,

Welcome to the astronomy forum. A few more details may help someone understand what you are doing and if an off axis guider will work; eg, type of mount you are using, what you are photographing, your camera, etc.

[scottyiu]

Hello. Thanks for your reply. My telescope is a 127mm Maksutov-Cassegrain and has a focal length of 1500mm. The mount is a az mount with autostar. My camera is a Nikon D60 DSLR. Hopefully if a off axis guider works then I am looking to photograph maybe some of the brighter deep sky objects.

[sxinias]

Scotty

I use a similar setup. A 6 inch SCT on a Skywatcher AZ goto mount (looks identical to your SLT mount but has different handcontroller firm ware) and a Canon EOS DSLR.

I don't think that you need bother about guiding. The reason is that with an azimuth mount, you will get field rotation. Stars close to center of the photograph will look fairly normal but rapidly become streaks of light the further away they are from the center of the photograph. This happens for photos taken with exposure times as short as 5 or 6 seconds for objects near the zenith or a minute or two for objects near the horizon in the east or west.

Also, the tripod on your telescope, and mine too, vibrates too readily for long exposure photos. Then there is the tracking ability of the mount. For visual purposes your mount will seem to keep an object dead center of the eyepiece; however, for a long exposure shot, you will notice that actually the mount is constantly making small corrective movements which translate into a blurred photograph.

Does this mean you can not take photos? No. You can take a series of short exposure photos and stack them into one final photo using one of several computer programs such as registax, etc. You can also piggyback the camera and get a lot of nice shots using the camera’s lens.

Here is a link to a primer for astrophotography: Mounts for Astrophotography