Nikodemuzz

Pardon me, but this is going to be accompanied with a story. 😃 Couple of weeks ago we were skiing in northern Finland. I had brought my astro gear with me, as the forecast showed good chance for a clear night during the week. I had just taken delivery of my SpaceCat, which was to be (and still will be) the start of my astrophotography career. I also brought the C11 for visual observations. The conditions were tough for visual and AP, with the large moon and the temperatures falling below -25C as the night went on. There were people with us who had never looked through a telescope, so I had set up for visual during the day. We spent some time mainly observing the moon as it got dark. The weather was a bit nippy, and everybody was happy to go inside quite soon. After dinner I headed back out. I mounted the SpaceCat, and had quite a bit of difficulty balancing, presumably the mount lubrication was starting to get slightly viscose from the cold. The grease was not the only thing feeling the northern winter and not appreciating it. Silly me, I had left the hand controller on the mount as we went in for dinner. For a moment I thought there was something wrong with the mount, but quickly realized it was just that the LCD had slowed down enough to not show the rolling text on the display at all! So I brought the hand controller in to warm up for a moment. Had a cup of rum and cocoa and headed back out to try again. Now the hand controller was working fine, and I was able to align the mount without too much issue. Next would be polar alignment using the All-Star alignment, as Polaris was hidden behind some large trees. As it turned out, my tripod placement during the day had left something to be desired, and the latitude bolts did not have enough adjustment in them to cover the error. I was faced with a choice, either move the tripod a bit and re-align, or press on with poor polar alignment. My frozen fingers and the re-dying hand controller decided I would press on. I could still have a go at guiding with a SynGuider I received with the scope a few years back. So I installed the SynGuider on the finder, only to find that the finder's helical focuser had frozen solid! OK, so no guiding. I could still try some short exposures unguided. I chose M81+M82 as my target, as they were the most interesting target in the area opposite from the moon. I slewed there, managed to focus and lo and behold! The clouds start to roll in. In the end I managed around 8 minutes through increasingly thickening cloud, no polar alignment, no guiding. It was fun, though, and plenty of lessons learned! I have to say that the camera (Fuji X-T3) operated flawlessly, despite being cold enough to stick to my bare fingers. I had quite something else in mind, but this is what I got... First attempt at imaging as well as processing. Probably not the last! 😃

Looking quickly it seems that there is less color noise in the latter, "darkless" image, which is interesting. Hot pixels are still there in both images, should they not have been removed during the stacking/calibration? Well, I am by no means an expert here, I'm sure the more experienced users will be able to help.

I found this article (which is no doubt familiar to many of you) :https://clarkvision.com/articles/do_you_need_a_modified_camera_for_astrophotography/ He mentions the same thing as you, Alan, about the Ha responses of stock cameras, and there is also a further link that contains transmission curves for a bunch of cameras: http://kolarivision.com/articles/internal-cut-filter-transmission/ The differing responsiveness to Ha is quite interesting and significant when choosing camera model, but I also found the writer's argument about post processing very intriguing. Do you guys agree with him? If he is correct, then what is the appropriate processing method that does not suppress as he describes? This is quite interesting, there seem to be arguments both for and against DSLR modification, with compelling photographic evidence backing either side. 😃 I certainly wouldn't mind if the modification wasn't necessary at all. It would also make me all the more frustrated about the lack of support for my Fuji. 😃

Thanks for sharing. I can certainly see what you mean about being able to pick up faint stuff! How dark is your sky, and did you use filters?

Thank you, Michael! That certainly increases my confidence level about my ability to complete the mod.

Thanks for the message! Very impressive result for such a short integration time, congratulations! I'm also in a Bortle 5 area, so this is quite informative. Where did you have the modification made, if I may ask? About calibration, I assume you mean dark frames? I have been under the impression that with the uncooled cameras there might not be much benefit from using dark frames. Dithering should help, if I'm not mistaken (a manual process with the X-T3...)

I would love to hear more about that! Thanks!

Are you sure? One full turn seems like an enormous room for error, although the thread may be very fine. I was thinking that I could measure the screw positions with a digital caliper, but thought it couldn't be trusted to be precise enough.

Thanks Michael, it is always useful to hear from others who have walked the path. 😃 The sensor alignment process did jump out as a potential source of headache when I read the modification instructions. The methods of recording the original sensor position that Gary mentions don't seem very precise. Especially if one would be using fast optics, the alignment probably has to be correct within some tens of microns or less. Shouldn't be a problem if I can measure the correct distances with that much accuracy, but I'll have to consider how I can make that happen.

Which models in particular? No need for modification would be a welcome prospect. Actually, my Fuji X-T3 should be a pretty good performer in that regard. Unfortunately the thorough lack of support from any astro utilities makes any attempts at proper deep sky photography a very laborious process. Which is why I am now looking at an additional camera to do that job.

You mean sensitivity in general? I would expect the Ha sensitivity to be behind a dedicated astro camera like that, especially without modification. Still, interesting to know! Not all targets are that dependent on Ha.

Thanks for the heads up regarding the 6D! Gary Honis has the instructions for modifying it, but of course that doesn't mean that there would'nt be mines in that field... Used 6D's are expensive enough to cause sadness if they are turned to paperweights by a ham-fisted hobbyist.

I'm considering a DSLR for an interim camera before eventually investing in a (mono) CCD. The idea is to modify the camera, and perform the modification myself. While I'm quite confident that I have the tools and skills to perform the modification with the help of online documentation, I would rather not do it on a new, expensive camera. There are, however, a lot of different models which would be reasonably priced on the used market. I can pretty well judge how those cameras would work in the normal photography scenario, but in astro imaging with modifications? Not so much. Are there some models that are particularly well suited for this function? I was looking at used Canon models that could be had with reasonable prices used (Canon because I don't know anything about Nikon cameras, and I already have EOS adapters for my scope. I could still consider Nikon if there is a benefit to it): - 600D - 2000D - 60D - 5D Mk2 - 6D (prices start to get high, but I could consider it if there is enough return in terms of quality) Older models than these are obviously more affordable, and I would be happy to go with one of those if they offer better value. The way I see it, the main differences will be sensor performance, modification difficulty (if there are differences) and price. The cameras will be used via laptop so I don't see much in terms of features that could make a big difference. In the models above there are both full frame and APS-C models. I could work with either field of view. Primarily my imaging will be with the WO SpaceCat, in the future perhaps also with a larger refractor. I might also have a go with my C11 + reducer, but that is of secondary importance. Any thoughts?

Edit: Never mind!

Do you know of any plans to add support for Fuji cameras?