Warren - Stargazing since the 60's! Scopes: ETX-LS6, ED80T, AT6RC, Lunt LS60T, C9.25 Mounts: Atlas EQ-G, Vixen Portamount II Cameras: Atik 314L+,DMK31AU03,SSAG, ASI120MC Filters: Astrodon LRGB, Orion HA, SII, OIII Acc: Orion 5 place Filter wheels x 2, Flatman Primary Imaging site: Bortle Scale Class 6 Red Zone http://astrobin.com/users/rigel123/
Whenever I have come into large sums of money in my life, I always put half of it aside to spend on fast cars and the pursuit of loose women.
I put aside the other half to spend frivolously.
Money can't buy happiness, but it sure makes living with misery a lot easier!
Clear Skies,Bob One 'scope at a time... "Onward! Ever forward, never straight!" - T. McMahon
C10NGT, Z8, 150 Rumak, XLT 150, C6, C5, SW5 Newt, 4.5 Ball, C102GT, C90, ST80, A70LF; 15x70, 25x100; Burgess BV; Paracorr II; T6 2.5, XO 2.58/5.1, Ethos-SX 3.7, Delos 4.5, TV Plossl 7.4-26, BCO 10, Hutech HC 12.5, Sterling 12.5-25, ES100 14, CZJ H 16/25, CZJ O 16, M5k UWA 24, T5 31, Ultrascopic 35, Titan-II 40; Bino Pairs M5k UWA 6.7, Baader Zoom 8-24, M5k SWA 24, TV Plossl 26, RKE 28.7; Zooms NZ 2-4, NZ 3-6, Leica ASPH 8.9-17.8, Baader 8-24; Baader Zoom Barlow, VIP Barlow
Friends call me Duane. Compustar C14, Leo Henzl's Custom C8, 6" Refractor Adv. GT mount, 6" F5 Omni XLT Newt., LXD-75 F4 Imaging SN8, Meade 8" F6 Newtonian, EX Dynamax DX6, RV-6 ETX-90 Astro, Meade 2045 4" SCT, B&L 4000 Vixen/Celestron 80mm F11 JC Penny 60mm AZ/ALT Refractor Binos 25x100
Quote:Of course if the mirror is shifting that much it also raises the question whether you are holding collimation.JimC
Quote:I was surprised since I don't experience this "shift" at all with my LS6. Could be newer, lighter scope though.
Quote:Quote:I was surprised since I don't experience this "shift" at all with my LS6. Could be newer, lighter scope though. Which "shift" are you talking about? The sideways shift while you're focusing or the focus slipping after you've focused? Let's don't be ambiguous.Mike
Quote:Is it possible that focus is changing due to thermal contraction of the OTA?
Quote:If your focus is changing though, and the image is not moving, perhaps you are having some other problem that has nothing to do with the mirror movement.
Quote:Try putting the scope out for a few hours before observing but if the temp is falling fast, it could be that if this is the problem (tube contracting) you may not resolve it.
Quote: This was the reason Celestron shipped Carbon fiber tubes for a while. As I recall, they said that the Carbon Fiber would not expand or contract the way the metal OTAs did so that for long period images, the focus would not change.
Could be your problem??
Quote:Quote:Quote:I was surprised since I don't experience this "shift" at all with my LS6. Could be newer, lighter scope though. Which "shift" are you talking about? The sideways shift while you're focusing or the focus slipping after you've focused? Let's don't be ambiguous.Mike I don't see either, no sideways motion when focusing and no drift after getting the object in focus.
Cactus Patch Observatory / 14" LX200
"The four points of the compass be logic, knowledge, wisdom, and the unknown. Some do bow in that final direction. Others advance upon it. To bow before the one is to lose sight of the three."
150mm MCT f/13, 31% CO
"People say I'm in denial. I disagree."
Quote:Yea, Rick, that's true. Over the years we've all seen various levels of mirror shift. And it's not surprising, really, when you move the mirror something is gonna shift.I consider myself fortunate my current Mak can focus on stars at upwards of 100x per inch and remain in the FOV. Easily. I doubt the star shifts more than the diameter of it's first ring, about 2.4" arc. That may change as it get's used, but for now no worrying about approaching focus from either direction. Though, slewing across the meridian does require a slight retouch. Like you, I can easily live with that. Would probably have refocused, anyway.
Quote:Mike, yea, the difference is noted. Mine has a tiny bit of either. But, if your 90 Mak is "slipping" losing focus simply slewing around the moon, that's not normal. I believe this focus slip is caused by the primary feeling the force of gravity and flopping a bit. It's probably tilting a tiny bit against the primary baffle as the scope changes it's orientation. Mirror shift is the primary being forced out of true by the focuser knob itself - during focus. Ideally, the primary should probably rest on the focuser knob and "lean" against the baffle.
Glenn in Boulder Starsplitter Dob 12.5" F6 with NGC Max Digital Setting Circles. Celestron C8, CG5 mount, Stellarvue 2" diagonal. EXS 102mm ED triplet. Siebert Black Night Binoviewer w/ Ultra 24s, Multi Mag OCA for my Dob, Galaxy Viewer FL Reducer + barlow adapter for my C8. Kendrick firefly heaters for the Binoviewer EP's. A fair number of eyepieces, filters, etc. Barska X-trail 30x80, Zhumell 20x80 and Alpen 10x42s binos. Solar filters for all the binos.