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  #21  
Old 22-10-2019, 12:22 PM
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lollywater (Paul)
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David, back to your original question.
I think you will have trouble with the variable extender on the 294. The extender has female one end and male the other. You need female both ends to attach the 294 and the 183 to the Rasa. The male of the extender attaches to the female of the 290 leaving the female extender to attach to the Rasa. I dont have one, but I think you may need a 5mm female to female as well as the 12mm variable extender for the 294. The Starizona is female/female

Re the image,I have assumed the Starizona is correct spacing and altered the extender accordingly for the 290.
cheers
Paul


sorry, image is upside down
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Last edited by lollywater; 22-10-2019 at 12:50 PM.
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  #22  
Old 22-10-2019, 12:28 PM
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h0ughy (David)
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Originally Posted by lollywater View Post
David, back to your original question.
You will have trouble with the variable extender on the 294. The extender has female one end and male the other. You need female both ends to attach the 294 and the 183 to the Rasa. The male of the extender attaches to the female of the 290 leaving the female extender to attach to the Rasa.

sorry, image is upside down
Have a 48 to 42mm adapter
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  #23  
Old 22-10-2019, 01:08 PM
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I have a few 42-48 adapters. The dont fit on my Rasa
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  #24  
Old 22-10-2019, 01:32 PM
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I have a few 42-48 adapters. The dont fit on my Rasa
The one from zwo does
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  #25  
Old 22-10-2019, 04:17 PM
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lollywater (Paul)
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Hmm. I have the one from ZWO as well . I cant get it to fit anywhere on the Rasa but I will take your word for it. The 11mm female/female 42 that comes with the 294 will attach to my Rasa .

On my Rasa , a variable extender needs a double female 42 spacer as well to attach the 294 to it. The 11mm that comes with the 294 plus a variable extender will be too long . I need the 11mm double female, so to get to 26mm I need a number of smaller 42 spacers. I dont have any smaller than 5mm. The Starizona on its own sorts that out for me.

The variable extender attaches my 290, 224 and 178 to the Rasa to a total of 26mm
cheers
Paul
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  #26  
Old 22-10-2019, 11:58 PM
astrod (Rod)
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For the ngc 6744 image it doesn't quite look like tilt but slightly worse tracking in one axis. I have a RASA8 where I had tilt and the effect is to have elongated stars in one corner (or side).
I introduced a ZWO tilt adapter 11mm + 10mm spacer + 6.5mm sensor distance and could focus well. I also added a T2 shim which moved the focus about 10% of the focus range.
Now I introduced the ZWO tilt adapter to fix tilt and I found that because it sits on the outside part of the locking collar it fixed the problem (without using its adjustment features) because it sits perfectly square whereas normal (narrow) T2 extensions tend not to sit sufficiently accurately.
I can give more details because I've glossed over things.
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  #27  
Old 23-10-2019, 09:08 AM
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lollywater (Paul)
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Thanks Rod.
Is that poor tracking in one axis because of poor polar alignment? How should I fix that?
My Rasa used to have significant tilt but a trip back to Celestron improved it heaps.

When I added a 10mm spacer to the 11mm + 6.5 mm camera =27.5, I had no trouble with focus either. The Starizona plus camera is 26mm so I have been keeping all the cameras at 26mm. Frankly, I dont notice any difference.
cheers
Paul
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  #28  
Old 23-10-2019, 09:37 AM
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Can you try a long single exposure? That would accentuate any tracking issues, at that focal length you should be able to get a minute or more unguided without major issues but if you have a polar alignment issue it should show up reasonably clearly by then, and any mechanical issues would be a lot more apparent.

If you used the ASI294 I would suggest a minute, at 120 gain and -15 degrees (It is a 294MC Pro isn't it? I know you have mentioned it elsewhere before but cant think in which thread) The area covering NGC253 and NGC288 should fit on the sensor of the 294 through the RASA.
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  #29  
Old 23-10-2019, 10:53 AM
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Thanks Paul
I will try that. None of my ZWO's are cooled.
cheers
Paul
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  #30  
Old 23-10-2019, 11:09 AM
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Ah, I had it in my mind you had a cooled 294.

You should still be able to do a minute or so exposure without too many dramas with hot pixels spoiling the show. I assume that the gain levels are the same as the cooled ones. If not, unity gain is 120 on the 294MC Pro and for a longer exposure I would use the equivalent if it is different on the non cooled version. I use it in the long exposures as for me it provides the best compromise between quick capture and linearity of response.
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  #31  
Old 23-10-2019, 06:13 PM
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Paul
I have a RisingCam 1600 that is cooled but I very rarely use it because I prefer Sharpcap to RisingSky software.
I will try both cameras at 1 minute and see how I go.
Might see you next Saturday night at Snake Valley.
cheers
Paul
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  #32  
Old 24-10-2019, 12:11 AM
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Hi Paul

(I'm having trouble getting the hang of how to use this messaging system.)

Because stars are (slightly) elongated in one direction and generally across the whole image then I guess the RA tracking is not as good as Dec. I do get this for some parts of the sky and certain seeing conditions. Poor PA you might see the Dec corrections being more busy but guiding should be ok. It might be slight backlash or tracking near the meridian which expose balancing imperfections.

Glad your significant tilt problem was fixed. What I found were subtle tilt problems when using certain configurations of adapters. When you see these problems you initially don't know whether it is the mirror; the "secondary" collimation; adapters holding your camera or if the sensor in the camera is slightly off-square.

I have removed the clear window because I found a configuration where I use 1.25" filters sitting in the middle of the tilt adapter. I was nervous about forking out money for the Starizona system plus want to buy 2" filters; not knowing if narrowband would work, etc. The short answer is the 1.25" filters work well at F2.

Not having the clear window and adding 1.25" filters downstream changes the distances a bit. I think I inferred (measured indirectly) for full focus travel (30 revolution of the focuser knob) the focal plane moves about 3mm so it can pick up a fair bit of slop (so numbers like 26 or 27.5 work). Having said that, I guessed that the best (design) focus would be somewhere where the focuser is say 30% where 0% in fully in and 100% is fully out. This means focus is achieved when starting from fully-in with 10 revolutions of the focus knob. Or equivalent 1mm of focal plane positioning. I'm seeing very sharp stars across my sensor when I do this (when I have it focussed and the mount is tracking well).

Rod





Thanks Rod.
Is that poor tracking in one axis because of poor polar alignment? How should I fix that?
My Rasa used to have significant tilt but a trip back to Celestron improved it heaps.

When I added a 10mm spacer to the 11mm + 6.5 mm camera =27.5, I had no trouble with focus either. The Starizona plus camera is 26mm so I have been keeping all the cameras at 26mm. Frankly, I dont notice any difference.
cheers
Paul
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  #33  
Old 24-10-2019, 08:56 PM
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Here is ngc 6744 ,58s x 10, zwo 294 uncooled, slight stretch on astrotoaster. I had to increase the min star size on sharpcap because of hot pixels.
The tracking seems ok to me and no donuts.
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  #34  
Old 25-10-2019, 06:57 AM
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The stars in the top corners (Particularly) suggest that the spacing is not quite right. If it were mine I would say the camera needed to move a small amount further away from the scope, but the RASA seems to reverse that. And perhaps a tiny amont of sensor tilt, both of which I reckon the F2 will make it fiendishly touchy about, we could be talking about a fraction of a mm here.



The stars in the corners appear like little arcs is what I am referring to.
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  #35  
Old 25-10-2019, 06:24 PM
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Quote:
Originally Posted by The_bluester View Post
The stars in the top corners (Particularly) suggest that the spacing is not quite right. If it were mine I would say the camera needed to move a small amount further away from the scope, but the RASA seems to reverse that. And perhaps a tiny amont of sensor tilt, both of which I reckon the F2 will make it fiendishly touchy about, we could be talking about a fraction of a mm here.



The stars in the corners appear like little arcs is what I am referring to.
Thanks Paul
A tilt adjuster has just arrived from Bintel. It is 11mm,so if I add a 10 mm spacer (as Rod suggested) to the 294 that will make 27.5. I will give that a go next clear night.
I am not sure what the problem was with the 283. That was the first time I used it on the Rasa. It wouldnt screw all the way on the Starizona filter holder , so it wasnt 26mm. But I cant see why that would cause a tracking problem
cheers
Paul
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