Now that is something I had not considered. I am 1mm different from specs, but could move back 5mm.
Not worried about the AO issue as the guide camera is in the filter wheel and as yet not seen an instance where it does not find a guide star. So a rotator is just a luxury.
Yes, I agree.
To be fair though, the benefit afforded by fr is in the order of a 10x increase in the number guide stars to choose from. One of these stars will be on average 10x brighter so you are more often than not able to run the AO at 10hz.
You can claw back a little bit of this advantage by sacrificing perfect framing of the imaging chip, or completely sidestep it by only imaging the 10% of dso's with the optimum guide star located at the field angle matching your imaging train. You could always periodically (manually) reposition the field angle of the guide camera to image a new batch of dso's.
271mm to work with, more if I move the secondary closer to the primary.
camera and AOX = 91.84 + 12.2 for adapter to TS flattener + 25mm for flattener + 10.3 for adapter to Atlas + 122 from atlas to rear adapter of rotator. Finally 15mm to mirror cell. That makes 276.43mm. 5mm could be gained from the secondary position.
For a rotator a Pyxis is the best solution from a quality and cost effective basis that matches your GS unit, IMHO do not consider anything else as they are nowhere near the capability.
I have a Pyxis that came on an Officina Stellare RiLA600 that I bought recently - it did not achieve focus with the CCD I have as my CCD was not your standard CCD design, so I upgraded to an Officina Stellare Rotofocuser (this is not what you want as it is EUR 3,500) for the system, and the Pyxis whilst being used (tested) once and thereby being basically perfect - is superfluous - it will not be used. If you are interested.
ASA make the best flatteners that exist globally. But you will need to give the Aust agent the system spec to get a correct selection, be prepared for a larger bill than the usual Yank or Asian stuff. Do this if you want something that is specifically engineered to your exact needs and also at the best quality level available globally. It is unapologetically expensive, but at their quality level you expect this.
There are other options that you could consider. These are grand master custom hand craftsmen in Japan (the guys that actually make this and other gear for Tak). They do not however speak or read English, but they are very capable as they have made gear for me for years, they do a really great job.
ASA on the other hand are a no risk solution, they will do exactly what you ask, to a sensational capability.
Good luck.
Last edited by Astromelb; 03-06-2014 at 05:57 PM.
Reason: correction
271mm to work with, more if I move the secondary closer to the primary.
camera and AOX = 91.84 + 12.2 for adapter to TS flattener + 25mm for flattener + 10.3 for adapter to Atlas + 122 from atlas to rear adapter of rotator. Finally 15mm to mirror cell. That makes 276.43mm. 5mm could be gained from the secondary position.
This all seems to be ok to me, but you might want to check that the flattener does not move the focus position. I know that with my mpcc for instance it does not effect the focal length, but the focus position does move.
This all seems to be ok to me, but you might want to check that the flattener does not move the focus position. I know that with my mpcc for instance it does not effect the focal length, but the focus position does move.
Yeah I was wondering if the focus position moved and you know the last time I went through the adapter roulette. The ASA one moves the focus back 5mm but the TS one does not say anything about focus shift. It could well be that is does move.
For a rotator a Pyxis is the best solution from a quality and cost effective basis that matches your GS unit, IMHO do not consider anything else as they are nowhere near the capability.
I have a Pyxis that came on an Officina Stellare RiLA600 that I bought recently - it did not achieve focus with the CCD I have as my CCD was not your standard CCD design, so I upgraded to an Officina Stellare Rotofocuser (this is not what you want as it is EUR 3,500) for the system, and the Pyxis whilst being used (tested) once and thereby being basically perfect - is superfluous - it will not be used. If you are interested.
ASA make the best flatteners that exist globally. But you will need to give the Aust agent the system spec to get a correct selection, be prepared for a larger bill than the usual Yank or Asian stuff. Do this if you want something that is specifically engineered to your exact needs and also at the best quality level available globally. It is unapologetically expensive, but at their quality level you expect this.
There are other options that you could consider. These are grand master custom hand craftsmen in Japan (the guys that actually make this and other gear for Tak). They do not however speak or read English, but they are very capable as they have made gear for me for years, they do a really great job.
ASA on the other hand are a no risk solution, they will do exactly what you ask, to a sensational capability.
Good luck.
Yes I already have the pyxis rotator. FLI focusor but am looking to fit in the flattener and AOX if I can.
Yes, I agree.
To be fair though, the benefit afforded by fr is in the order of a 10x increase in the number guide stars to choose from. One of these stars will be on average 10x brighter so you are more often than not able to run the AO at 10hz.
You can claw back a little bit of this advantage by sacrificing perfect framing of the imaging chip, or completely sidestep it by only imaging the 10% of dso's with the optimum guide star located at the field angle matching your imaging train. You could always periodically (manually) reposition the field angle of the guide camera to image a new batch of dso's.
Clive the guide star selection is automatic at present via CCDAP's selection criteria. Never missed a guide star yet and the stars are always just at the very outer edge of the field. The pick off prism is just a fraction out side the imaging field. There is a slight shadow of the prism on my flats, but there is always plenty of stars for CCDAP to select from.
If that makes sense.
Latest notion is that I can fit all of it in. I am about 5mm short but either flattener might push focus back a bit or I can push the secondary back a little like you suggested.
Paul, I'm sure you know this
but for the benefit of anyone who isn't aware;
RC's typically have an f3 primary and an f8 final focal ratio.
It follows then that any movement in the secondary position relative to the primary will be amplified at the ratio of 8/3.
Therefore, to gain an extra 5mm of back focal length, the secondary should be moved towards the primary by 1.875mm.
Paul, I'm sure you know this
but for the benefit of anyone who isn't aware;
RC's typically have an f3 primary and an f8 final focal ratio.
It follows then that any movement in the secondary position relative to the primary will be amplified at the ratio of 8/3.
Therefore, to gain an extra 5mm of back focal length, the secondary should be moved towards the primary by 1.875mm.
Can't say I would agree with this advice. Mirror spacing is critical with an rc in preventing spherical aberration.
Dear Paul,
How are you focusing ?
If you are using an electric focus process and also a Pyxis rotator you may end up in exactly the same place I did with my RiLA600, not enough back focus.
So I changed to an Officina Stellare Rotofocuser - please see - http://www.astronomyalive.com.au/off...-aseembly.html
It works perfectly.
Clear skies.
RC's typically have an f3 primary and an f8 final focal ratio.
It follows then that any movement in the secondary position relative to the primary will be amplified at the ratio of 8/3.
Therefore, to gain an extra 5mm of back focal length, the secondary should be moved towards the primary by 1.875mm.
Actually, factor is (8/3)^2 + 1 or 8.1x .
That is, for every one millimeter change in spacing, focus moves by more than 8mm. To move final focus by 5mm you need to change spacing by mere 0.6mm.
Which won't change much spherical correction, btw.
Actually, factor is (8/3)^2 + 1 or 8.1x .
That is, for every one millimeter change in spacing, focus moves by more than 8mm. To move final focus by 5mm you need to change spacing by mere 0.6mm.
Which won't change much spherical correction, btw.
Thanks for the clarification. I will keep this in mind. 5mm should do the trick but if I moved 1mm back that would make it 8mm back and that is probably more than enough to accommodate everything. Interesting times. Back end of the scope is worth ten times more than the front end.
I received the TS Optical flattener today. See images below (not great but at least you can see what I am on about).
The flattener is rather large really. Very solid construction and has that sturdy feel to it. It comes with an adapter for DSLRs but I don't have it attached.
I am awaiting adapters being made by Precise Parts which should be shipped on Thursday.
