The Admiral

Thanks for posting a link to this fascinating individual, Steve. A man of many talents. Ian

Now you are asking! Ian

In fact Kay's do call them machine screws, rather than bolts! So it shouldn't be 'nuts and bolts'! Ian

I've generally bought my stainless nuts and bolts from Kay's Fasteners through eBay. You can buy in small quantities quite economically, and the service has been first rate. The pictures shown will give you a guide as to how long the thread is. http://stores.ebay.co.uk/Kays-Fasteners?_trksid=p2047675.l2563 Ian

There has been much fuss about conveying Li batteries, what with laptops catching fire and the like, and I believe that Royal Mail does not unless the battery is in the item it is to power. I'm no authority, but checking on the web seems to indicate that up to 100Wh capacity is generally freely allowed on aircraft, but must be carried as hand luggage. You can buy fireproof battery bags and I think if it was me I'd get one for a larger capacity battery if I was transporting it. Ian

Welcome to the thread icebergahed. Sorry, bit of a long answer coming up (never let it be said I don't give value for money . But then I'm not getting paid for this!) First things first, a lot of imagers will tell you nothing less than an EQ mount will do, and then a dedicated astro camera is to be preferred. Totally untrue, but there are limitations doing Alt-Az imaging with a DSLR, but so long as you are content to stay within those limitations, all well and good. The principal limitation is that with an Alt-Az mount, the image will rotate as the target moves across the heavens. You can get around this peripheral star streaking by using short exposure times, say 30s or less, sometimes more, depending on which part of the sky you are looking at. The consequence of that is that you will need to take an awful lot of pictures, many dozens, if not hundreds, in order to suppress the noise in the image. The second thing is that Alt-Az mounts move in two directions to keep a target centred, in a kind of zig-zag pattern, and with the cheaper mounts these movement aren't necessarily very fine, and you will find that some of your frames will show star streaking, even if, on the whole, the target remains centred. You cannot use such frames and so you will end up discarding a percentage. This mount inadequacy is made worse when you have long focal length 'scopes, such as the 6SE. OK for visual, but a bit of a challenge with photography. You can ameliorate this by using a flattener/reducer, such as https://www.firstlightoptics.com/reducersflatteners/celestron-f63-focal-reducer.html. This does three things. Firstly it reduces the FL of the telescope and so it will be less susceptible to mount inadequacies, but secondly, and just as importantly, it will give you a wider field and in doing so will concentrate more photons onto each pixel. In other words, improve your recorded signal of these faint objects, and help improve your image, but at the expense of a wider overall field of view. Thirdly, it will keep the image sharper across the frame, rather than sharpness being confined to the centre of the frame. This isn't an essential accessory, but I think it would be worthwhile. Some others may chip in here. Interestingly enough, the starter of this thread asked a similar question about this back in 2012 (https://stargazerslounge.com/topic/167836-focal-reducer-on-nexstar-6se/). I'm sure that plenty of material on this can be found on this site with a search. Finally, I'd thoroughly recommend reading "Astro-photography on the Go - Using Short Exposures with Light Mounts", by Joseph Ashley. Good luck, and looking forward to see your images on here! Ian

Thanks for that. It looks as though your cat is showing a bit more resolution than the refractor, as you'd hope, but I'm not sure that I don't prefer the refractor version* . One thing I did spot was that on the full-sized version there are a number of, possibly pixel sized, black spots. I don't know whether this is a characteristic of the sensor, or the processing. Besides limited seeing of course, when you are imaging at the 0.5 arcsec/px level (using a 0.71x reducer pretty much nullifies the change when you go up from 16Mp to 24Mp I reckon), you are really asking the mount to track at better than 0.5 arcsec, and from what I've read that would be quite challenging. Anyway, thanks for giving us a bit of an insight into the X-T2 as an astro camera. Ian Edit. But then, I think the colour in the new one is better! I suppose the black dots could be star forming regions, but I don't think so as they are fairly widespread.

Well it's always worth looking at the user guide for StarTools (http://www.startools.org/downloads). This is a refreshed guide which I've not studied, but it should be in there like the original. To be honest, I'm not that consistent with StarTools and I'd probably start with a 50% or 33% bin in the first instance, depending on my mood , but it all rather depends on how noisy my image is, and I may push this higher if things look too ragged. Of course, the image gets quite small. On the other hand if it's a bright target and I think I may want to print up the image I might try without binning. I suggest that you try to see what the effect is on any particular image. Now don't forget that I image with a 715mm FL refractor with the X-T1, which gives about 1.4 arcsec/px native, or 1.75 with reducer. This is most likely to be below the seeing conditions anyway, and so is providing empty resolution, so binning won't make any appreciable difference to the final image other than improve the noise. Your Vixen will give about 0.5 arcsec/px even with the X-T1, even less with the X-T2, so unless your seeing is exceptionally good you could bin significantly without losing any 'real' resolution. Again, try it an see. Repeating a StarTools process where you might want to change just one or two parameters is not made easy as the software doesn't store the settings in a sidecar file for example, but you can look in the StarTools log file where each setting is listed in a text file; you just have to re-enter them again. That's my understanding anyway. There are a number of ST users on this site so if you've specific questions, then post them. The ST Forum is reasonably good too, and Ivo is quite responsive. Ian

Thanks for doing the test David. They are very nice images and it certainly looks as though the X-T2 performs at least as well as the X-T1. The Ha response seems to be every bit as good, which is a key thing. I'm not sure about noise, I think more experience with it would be needed, especially as the two M13 images have different black point settings which makes comparison harder. That Vixen certainly resolves the stars well, even if it does take 2 hours to collimate (!), and I like the star colour in the X-T2 process. As a matter of interest, I would have thought the X-T2 image would have been well over-sampled, so how much, if any, binning did you do in StarTools? Regards, Ian

That's a nice image, I like the clarity and strong colours. Nice to know the other details though please! Like, what mount, guiding, sub duration? Ian

This thread has piqued my interest in construction method, 'cos it strikes me that if you double skin the walls, then there must be a proper construction method to eliminate potential damp and rot problems. Just randomly surfing t'interweb searching for 'garden rooms', I found this example: https://www.greenretreats.co.uk/construction/. I'm not saying that this is necessarily the right way to do it, but it looks as though a cavity and vapour barrier is a good idea (like house walls really, and ventilation of roof spaces). Just my 2 cents worth! Ian

I've no experience of observatories but do have a shed . The problem with shiplap I find is that the overlap is not great and it doesn't take much shrinkage to result in gaps through which rain can blow in. Knots are another problem, because if they fall out there's a hole. I guess it all comes down to the quality and type of the wood used for construction. Ian

That's a great start Galen, you are on your way Yes, a dark site will make a big difference I'm sure, but there are a few things that can help you on your way. Don't ignore the value of using flats and darks, try to get them if you can. If you use darks, make sure that you take a decent number of them otherwise they'll introduce more noise than improve the picture. I'm talking of 50 or so here! Also, try to get (a) as long a sub as you can without stars getting out of round or increasing the sky background too much, and (b) increase the total exposure time. As an Alt-Az imager stuck with a maximum of 30s subs, I take anything up to ~250 subs with a 102mm refractor! I'm sort of thinking of at least an hour's worth after stacking only the good subs. It may be a case of diminishing returns, but 15 minutes is a bit on the low side. And it does use up the hard drive capacity, especially as they're converted to DNG as well! I don't know what ISO you use but I generally image at 1600, though if I have bright objects in the field and I want to capture with as much colour as I can, I drop it down to ISO400. I agree, the Ha response is pretty good for a non-modded camera, and it's noise is low and resolution delivered excellent. I wondered about about the X-T2's performance as it has rather smaller pixels, perhaps too small? Is the red response just as good? If you look at the read noise vs ISO here, for both the X-T1 and X-T2, you'll see a different behaviour. The X-T1 is ISO-less, but the X-T2 appears to use two different amplifiers depending on ISO. Ian

Hmm, mindful of the Sony star-eater problem, I wonder if the signal processing to reduce noise is intrinsic to the sensor chip rather than external to it, resulting in artificially 'quietened' pixels. I would be surprised if Sony made a different chip solely for astro imaging use. All a wild guess, of course! Sorry, I am getting a bit off-thread here. Ian

Olly, I have long wondered though whether the presence of, say, amp glow, or other similar large scale artefacts besides hot pixels would invalidate the use of a master bias in lieu of a proper dark (though not to replace a flat dark as I wouldn't expect such defects to be prevalent with short exposures). What is your experience in this? Ian