alacant Posted November 19, 2017 Share Posted November 19, 2017 Hi everyone I'm trying to convince myself I don't need an OAG. There's star elongation -I think- this may be due in part at least to the PHD2 error corrections being greater in RA than in DEC. The PHD2 gurus suggested that dither may also be a factor, so half the frames here are not dithered. They also suggested the near impossibility of being able to guide a 6" f8 Newtonian without an OAG. Anyway, 2 nights of experimentation with and without dither, breaking down and tightening with proper screws, neoprene shims to stop the mirror moving, springs over the primary lock screws, llaves allen y inglesas... Do you notice the elongation? Thanks for looking and clear skies. 700d + nt150l; 3 hours frames of different lengths 30s to 6m Link to comment Share on other sites More sharing options...
Davey-T Posted November 19, 2017 Share Posted November 19, 2017 Not at 100% full size so I wouldn't worry about it. Very nice image, just taking some flats to see how my version has come out so far, if it's anywhere near as good as yours I'll be well pleased. I should think an OAG on a Newt' would cause problems anyway with focus travel and balance. Dave Link to comment Share on other sites More sharing options...
cfpendock Posted November 19, 2017 Share Posted November 19, 2017 Really nice. I like the framing and the field of view. Chris Link to comment Share on other sites More sharing options...
tomato Posted November 19, 2017 Share Posted November 19, 2017 Nice one, dust lane detail is there, not enough star elongation to detract from the end result in my humble opinion. I’m currently working on a wider field image which will include the galaxy cluster Abell 347, assuming they’ll be visible in my final image. Link to comment Share on other sites More sharing options...
alacant Posted November 20, 2017 Author Share Posted November 20, 2017 13 hours ago, tomato said: wider field image which will include the galaxy cluster Abell 347 That's an interesting project. Just had a quick look in CDC. It looks as if 750mm will fit in both 891 and a lot of the little galaxies. Do you have enough frames for an interim view yet? Cheers and clear skies. Link to comment Share on other sites More sharing options...
alacant Posted November 20, 2017 Author Share Posted November 20, 2017 14 hours ago, Davey-T said: an OAG on a Newt' would cause problems anyway with focus travel and balance Hadn't thought of that. I've about 25mm inward focus left and at f8, there's no corrector to have to worry about, but yeah, the extra weight would probably be difficult to balance. Are there OAGs designed for Newtonians I wonder, or are they for refractors only? Link to comment Share on other sites More sharing options...
ollypenrice Posted November 20, 2017 Share Posted November 20, 2017 The OAG is primarily a tool for reflectors because of the issue of mirror flop which the guidescope doesn't 'see.' I've never used one on a refractor, though you can. If you have the back focus I'd go for it. I'd be very reluctant to give up dither with a DSLR, too. Olly Link to comment Share on other sites More sharing options...
glowingturnip Posted November 20, 2017 Share Posted November 20, 2017 can confirm OAGs work a treat on newts. Like you I was sceptical too, but having one now on my 200PDS (200mmx1000mm) I'm getting better guiding than ever, and always manage to find a guide star (so far anyway). Just do your calcs for focus travel and weight etc. Link to comment Share on other sites More sharing options...
jjosefsen Posted November 21, 2017 Share Posted November 21, 2017 I love the dust lane running right through! Putting this on the list of object to image for sure.. What mount are you using? Link to comment Share on other sites More sharing options...
alacant Posted November 21, 2017 Author Share Posted November 21, 2017 12 minutes ago, jjosefsen said: the dust lane Yeah, I'm trying to picture what's happening. If we're seeing it edge on, then the dust lane must divide the galaxy into 3 layers, stars:dust:stars maybe? Or could it be there's dust only at the side toward us but outside the galaxy? Link to comment Share on other sites More sharing options...
alacant Posted November 21, 2017 Author Share Posted November 21, 2017 17 minutes ago, jjosefsen said: What mount eq6 Link to comment Share on other sites More sharing options...
jjosefsen Posted November 21, 2017 Share Posted November 21, 2017 2 hours ago, alacant said: Yeah, I'm trying to picture what's happening. If we're seeing it edge on, then the dust lane must divide the galaxy into 3 layers, stars:dust:stars maybe? Or could it be there's dust only at the side toward us but outside the galaxy? Makes sense that the dust is in the middle of the galaxy when edge on, as it is also affected by the spin of the core. In my mind atleast.. ☺️ Link to comment Share on other sites More sharing options...
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