mbrickley

Hi Dave Thank you so much for coming back to me, sorry for the delay posting a response... I have two little ones and they were soooo full on over Easter! I think this sounds like a great Mount ., can you tell me have you Tried using it unguided and if so are you able to get 1 min or so subs from it (I’m at 540mm fl) thanks so much and have a good day Mark

Thanks very much for replying... the RST-135 was another mount I was considering exactly for the EAA use as you describe using 1 minute subs but the consensus seemed to be you couldn’t image unguided at all with it due to the high unguided pe... can I ask are you guiding the 5 min subs and are you polar aligning this using the QHY polemaster that I think just bolts on to it? Thanks very much for taking the trouble to reply Mark

Hi Im considering this mount and will use it for a mixture of proper astrophotography, obviously what it’s designed for, but also for some visual observing and for some EAA with 30s- 1 minute subs. I’d obviously buy a mount of this calibration for the proper Astro sessions but would also want to use it for short EAA sessions with no fuss. I understand the concepts of model building and accurate polar align but wonder if anyone has tried just aligning on the pole using sharp cap or the like , doing a 1 (2 if it doesn’t support 1) star align and then using it without model building etc.... I’d be very interested if anyone had tried doing this for visual how they found goto accuracy and if anyone has tried this and then taking short subs such as you use for EAA of say 1 minute. When I’m doing EAA, which translates to the kids went to bed late and it’s work tomorrow, I would not want to spend half an hour building a complex model but just do a rough setup as above slew to several targets and produce images of relatively low quality by stacking 30s-1min images using sharpstack for live viewing and documentation Any info would be very gratefully digested 😎 mark

I've now had a chance to calculate some other parameters for my 460ex based on the data I collceted as above: readout noise = 3.84 electrons conversion factor (gain) = 0.26 electrons / ADU. This implies a ccd photosite contains at full readout 65535 = 17039 electrons which is just under 3k less than the full well capacity as quoted by Sony of 20k . This 10% or so overhead may account for the linearity up to the full adu count, see above. I suspect the manufacturer has set the maximum adu to keep the readout within the linear range of the chiop. Since the maximum possible accuracy for magnitude determination vareid with the inverse square root of this (see http://www.britastro.org/vss/ccd_photometry.htm) this implies a maximum magnitude accuracy of 0.007 magnitudes but of course in real terms sky noise and maybe read noise will be the poroblem. dark current = 0.001524 electrons per pixel s-1. This is negligible at all sensible exposures all in all the camera should perform well for photometry Its interesting to note that at all reasonbale exposures the error induced by both read noise and dark current is about 1 adu and therefore can be ignored.

HI I am interested in using the Atik for variable star phootmetry amongst other things and I couldnt find good validate ddata for its linearity so I've spent a happy day makinga constant light source imaging box as per Berry and Burnells Image processing book and producing some reliable data for the linearity of the 460Ex (and hence one would expect the underlying sony chip) over its full ADU intensity range. The results are frankly stunning regards the ability of this camera to perfiorm as a linear measurement tool: The linearity is within 0.01% of the linear regression up to over 99.5% of its range and the overall r squared approaches 1. This means that under fairly rigorous testing the camera is completely reliable as a photometric tool over its entire ADU range and I think puts to bed the idea that you can only use this ABG camera up to some arbitary ADU (50% of range is often quoted). This result suggest the camera does as well as a NABG camera to all intents and purposes as regards linearity at least and thus makes an excellent tool to partner with a small telescope (ie matching the small pixels) as a scientific tool for photometry and by extension more esoteric pursuits such as galaxy morphology analysis and the like. I'm really suprised by this data but I think Atik should feel very pleased with themselves. Incientially I have no contact with Atik other than as a now very satisfied customer. graph attached. Cheers Mark