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HOW TO MODIFY A SKYWATCHER SW880 (10" DOB) TO INTERFACE A CANON EOS 350D CAMERA
Word of Warning ~ This modification will reduce the focal length of your scope and therefore you will need to use an extension tube app 50-60mm for your eyepieces

Fig 1 GSO Crayford racked in height 3" SW880 R&P Racked in 4"
Shows base of R&P milled out an extra 1.82mm the diameter of the GSO and 4x4mm tapped holes.
I found a local Engineer who had a computerised Milling machine and he only charged a small fee for doing this work during a "quiet" period.
R&P Base fitted to GSO Now only 2.5 high. You could machine out the GSO base . But I preferred to use the old R&P which will still fit on the modified base and the crayford is still original if wanted."

The racked in measurements are taken to the 2" drawtube face from the Dob Tube with this modification the focal length is shortened by 1.5" which is adequate to mount a Canon EOS 350D direct to the 2" focuser for prime photography. The focal point is approx 10mm racked out with the camera having a 35mm focal depth from face to the sensor
Note: Having modified the focuser for the camera, you will of course need a short extension tube adapter to make up the loss in overall focal length to use your normal EPs. These tubes are quite cheaply found on EBay.



The first scope I purchased was a very cheap 3" on EBay The .95" EPs, were pretty poor but it was a start. I modified the plastic tripod mount to an aluminium plate so as to fit on a Manfrotto Tripod, put on a better finder scope and made a camera adapter, the first of three I have made. A problem with the camera mount surfaced when the lens touched the EP and an "error 18" obstructed lens kept coming up. This has been addressed in the MkIII version below

Home made Dobsonian Scope, Using Skywatcher 200mm f5 Primary and 58mm secondary. Crawford 2"/1.25" Focuser and GSO super Plossls

The 3rd camera mount, came about quite by accident, searching through my junk box, I found a 50mm PVC pipe joiner and discovered that the inside diameter was exactly the same as the OD of the 1.25" EP adapter, also by fitting a filter extension on the camera prevented the lens of the camera from touching the EP face, which fits perfectly and aligns spot on in the adapter. The third photo is a shot of the moon taken using this adapter using a GSO SP 26mm. Pic 4 a much overexposed picture of Jupiter shows its potential. The camera is a Canon A520 4mpx point and shoot.

First attempt at "prime Focus" 3 days before end of moon cycle taken at 6am on approach of dawn
Interfacing a Canon EOS 350D XT Rebel proved to be a bit of a problem with the 200mm Dobsonian, in that the focal length of the camera added a further 35mm to the focal length (and the focusing range of the scope) using an EOS Tee ring and a Meade adapter. The only solution to start with was to raise the Primary mirror 60mm up in the tube. This of course also put the EPs out of range of the focuser, this was compensated by using the 60mm focal extension tube which came with the Meade adapter.
With a DSLR camera you do not have a preview of the photo when shooting and focusing of the scope must be done through the viewfinder. The above photo was taken using only the scope's mirrors in the "Prime Focus" mode, which means no eyepieces nor lens are used. This can present a number of problems, like focusing and the length of the exposure on a scope manually guided, hence the EQ platform project. 2X viewfinder extensions are available to assist in focusing.
The photo was taken at ASA400 1/100 with Canon 350D

One month after the first attempt with the Canon EOS 350D the above photo was taken 5/9/06
Almost full moon, focusing and editing moonshots is becoming better, the extension viewfinder for the Canon, has certainly proved its worth in fine tuning the focusing, which can be difficult at the best of times for my ancient eyes.
ASA200 1/800 - No filters used. Edited in PS
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  • Located in Myaree, Western Australia. For a large range of optical devices and Telescopes/accessories ~ Official Skywatcher Agents: Contact Greg on 08-93137444



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