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Hello, I know the importance to have a cooled imager for the deep sky. But I will want nevertheless to know as from which exposure time that is really necessary . thank. Bernard |
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Hi Bernard, It depends very much on the camera type (DSLR,CCD) and the ambient temperature. My experience with several cameras ( I used MEADE CCD,CANON DSLR, ATIK and ASI) is : if ambient temperture is higher than 10° C and exposure times greater 30 seconds all cameras need cooling. Not to forget to take dark current and dark / flatfield frames for each telescope / cam / optic train configuration. Cooling of DSLR is tricky, I build a thermo box with fan and thermo- electric cooling plates around it. Works fine, but adds a lot of weight. I hope I could give you some hints cheers Wanni |
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| Thank Wanni |
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I am new at astro-imaging but not photography - I am a sports photography by trade and a Nikon shooter. i have some high quality Nikon glass, as in Nikon 200x400 F/4 and Nikon 600 mm F/4 using a DSLR plus an assortment of wide angles, I naturally wanted to try imaging with these kits. I do not use batteries to power the cameras for two reasons (1) heat produced from the batteries which set underneath the sensor and (2) and the need for frequent battery replacement during a shoot - especially in cold weather which is when I am inclined to use the DSLR. If I was just exposing for one 30 or 60 second exposure.... then the heat caused would not create unmanageable noise but multiple exposures without times to cool down between shots is another issue - ie the bane of DSLR's when astroimaging. I have a Nikon D800e that has been modified both for astro-imaging and with a heat reduction system (Spencers did the upgrade and I recommend them) ...I also have the Nikon D810a, which is their newest and only digital astroimaging camera. The difference in images is noticeable.... the heat reduction system is the difference. Personally, I like to image with the DSLR but choose to do this in cool conditions - fall an winter. Other than that I will use a CCD, Atik 383L OSC or Atik 414ex monno with cooling to 40 below ambient. Even with these cameras modified and equipped with cooling systems - there is still a great need for the support files, "darks, bias, and flats." |
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Another Nikon shooter here. I more tolerant of the noise and will shoot typically 5 minutes in dark sky. The ATIK 460ex I cool typically to -5 C but in winter sometimes -25 just to get below ambient.  With DSLR, I'd say 15C< ambient is good for me, where I am most nights are usually that. I know someone tries a T3I at 34C, this was pretty bad noise wise.... |
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