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Hello Everyone, I have 7x 36mm Baader filters in my QHY Filter wheel. I use a simple Orion 80ED with a manual focuser. I have two questions basically. a) How important is refocusing between the LRGB Ha OIII and SII filters? b) If important, then how do I manually calculate the offset distance between them assuming the filters aren't parfocal?
I have recently collimated one of my telescopes the Orion SpaceProbe II Reflector Telescope. Spider vanes are equal in length, secondary mirror correctly centered to focuser tube and tilt. Completed correct collimation. When I have done the star test surprisingly there are rectangular shadows appearing at 5 o'clock and 11 o'clock position. I believe the 11' o'clock is focuser draw tube and the the other is secondary mirror clip. I could not take picture of it but I could able to find a picture of similar issue someone faced. The same I have attached. Please look in the issue and guide me. The shadows exactly protrude at 11 and 5 o'clock positions in the image attached. I have taken couple of photos through focuser tube with draw tube in and out. Shows perfect cllimation. Pls look in to the photos. 1. Star test(Someone's photo facing similar issue) 2. Look through focuser when draw tube fully in( you can see protruding draw tube) 3. Look through focuser when draw tube fully out( only secondary mirror clip seen) 4. Look through focuser when draw tube fully in with camera flash( you can see correctly aligned spider vanes, correctly centered primary mirror reflection in center and draw tube). 5. Look through focuser when draw tube fully out with camera flash(Only secondary mirror clip seen all others correctly aligned) Interestingly I had observed that these rectangular obstructions are appearing when outward focus(I mean when draw tube fully out) draw tube not obstructing light path. So strange. Experts pls look in to the matter. Earlier this issue is not there in star test the star test image is exactly like image number one except without rectangular shadows but little offset at 4 'o clock. After adjusting the spider vanes and bring the secondary mirror holder exactly center to OTA this issue arrised. do the obscene of the offset causing the issue. But for slow telescopes offset is not an issue. One can align secondary mirror at the center of the OTA. What could be the issue then? Thanks in advance.